57 results on '"Heinrich, Christoph"'
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2. Band Ligation-Assisted Forceps Scissor Transection of a Unique Pedunculated Colorectal Lesion with Stalk Varices
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Zimmer, Vincent and Heinrich, Christoph
- Published
- 2022
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3. Anorectal Endoscopic Hybrid Resection of an Uncommon Cause of Debilitating Diarrhoea: Polypoid Supra-Anal Mucosal Prolapse Syndrome
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Zimmer, Vincent and Heinrich, Christoph
- Published
- 2021
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4. Hematite Breccia-Hosted Iron Oxide Copper-Gold Deposits Require Magmatic Fluid Components Exposed to Atmospheric Oxidation: Evidence from Prominent Hill, Gawler Craton, South Australia.
- Author
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Schlegel, Tobias U., Wagner, Thomas, Wälle, Markus, and Heinrich, Christoph A.
- Subjects
HEMATITE ,GOLD mining ,IRON oxides - Abstract
The Prominent Hill deposit is a large iron oxide copper-gold (IOCG) resource located in the Olympic IOCG province of South Australia. The deposit is hosted by brecciated sedimentary rocks and structurally underlying lavas of the ca. 1.6 Ga Gawler Range Volcanics. Both rock units are altered and mineralized, forming characteristic hematite breccias. They are located in the footwall of the Southern overthrust separating the host-rock package in the footwall from Paleoproterozoic metasedimentary rocks in the hanging wall. The metasedimentary rocks were intruded by the Hiltaba Suite granites, which are comagmatie with the Gawler Range Volcanics and show widespread magnetite-rich alteration. Economic mineralization was formed dirough a two-stage process. Early pyrite and minor chalcopyrite were deposited from moderately reduced fluids during sulfide stage I and are hosted in subeconomic magnetite skarns and in the brecciated sedimentary host rocks. This preore stage was overprinted by the economically important stage II sulfides, deposited from hypogene, oxidized fluids ultimately sourced from the paleosurface. The high-grade Cu ores contain dominantly chalcocite, bomite, chalcopyrite, and gangue minerals including fluorite, barite, and minor quartz hosting mineralization-related fluid inclusion assemblages. Petrography, microthermometry, and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICPMS) microanalysis were used to characterize pre-, syn- and postmineralization fluid inclusion assemblages. The results permit discrimination of four fluid end members (A, B, C, and D). Fluid A is the main ore fluid and hosted in fluorite and barite intergrown with Cu sulfides in the breccia matrix. It is weakly saline (< 10 wt % NaCl equiv) and contains low concentrations of K, Pb, Cs, and Fe (600 ppm) but is rich in Cu (1,000 ppm) and U (0.5-40 ppm). A magmatic origin of the salinity is supported by the low molar Br/Cl ratio of 0.003. We suggest that the solute inventory was derived from shallow fluid exsolution and degassing of late Gawler Range Volcanics and subsequent complete oxidation of the fluid via contact with atmospheric oxygen. Fluid A migrated through oxidized aquifers to the site of the Prominent Hill deposit, where it became the main driver of stage II copper mineralization. Fluid B occurs in fluid inclusions in siderite + quartz-bearing veins crosscutting the hematite breccia. It is die most saline fluid, with a total NaCl + CaCb concentration of 36 to 45 wt % and a low Ca/Na mass ratio of 0.3. Fluid B is rich in K, Fe, Pb, and Cs and contains modest Cu (-70 ppm). Its composition is typical of a moderately reduced magmatic-hydrothermal brine modified by fluid-rock interaction. Fluid C is hosted by fluid inclusions in fluorite and barite within bomite + chalcocite-bearing ores. It is a calcic-sodic brine witii 16 to 28 wt % NaCl + CaCl
2 and has an elevated Ca/Na (0.6) and high Br/Cl ratios characteristic of basin brines of residual bittern origin. It is quite rich in Cu (-200 ppm) and likely contributed metals to economic mineralization. Fluid D is hosted by inclusions in fluorite in late veins crosscutting the hematite breccia. The total NaCl + CaCl2 salinity ranges between 19 and 30 wt %, and the concentrations of K, Mn, Cs, and Pb are similar to those of fluid C. Fluid D is a basement brine with characteristically high Ca/Na ratios of about 2 and contains modest Cu (-100 ppm). The high-grade copper mineralization in the Prominent Hill deposit originated dominantly from magmatic components, including both die metal inventory (Cu, minor Au, and U) and sulfur. The essential factor controlling the high-grade IOCG mineralization was wholesale oxidation of magmatic Cu and S from Gawler Range volcanic eruptions; volcanic gases reacted with atmospheric oxygen at or near the Earth's surface-for example, in an acidic volcanic lake environment. Oxidized surface fluids charged with Cu, U, and sulfate and high acidity then infiltrated the host rocks at Prominent Hill and became reduced by ferrous iron in residual magmatic brine, in nonmagmatic basin brine, and by ferrous iron-bearing minerals. Copper sulfides and hematite precipitated in a zone of fluid mixing and by interaction of the fluids with acid-neutralizing host-rock strata. Limited sulfide for the low-sulfidation ore mineral assemblage was supplied, to presently unknown proportions, from magmatic-hydrothermal pyrite derived in a preore stage of mineralization and from magmatic sulfate reduced by aqueous Fe2+ to precipitate hematite. Exploration-relevant factors for Prominent Hill-style high-grade copper ores are the combination of (1) active volcanism during the late stages of the Gawler Range Volcanic Province, (2) a fluid-mixing interface between deep brines and an acidic, surface-oxidized but magmatically charged water as the main ore fluid, and (3) a mappable gradient of acid neutralization in brecciated and chemically reactive host rocks, ideally containing carbonates and some earlier pyrite. [ABSTRACT FROM AUTHOR]- Published
- 2018
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5. Magma Evolution Leading to Porphyry Au-Cu Mineralization at the Ok Tedi Deposit, Papua New Guinea: Trace Element Geochemistry and High-Precision Geochronology of Igneous Zircon.
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Large, Simon J. E., von Quadt, Albrecht, Wotzlaw, Jörn-Frederik, Guillong, Marcel, and Heinrich, Christoph A.
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MAGMAS ,PORPHYRY ,ZIRCON - Abstract
Geologic field relationships combined with spatially resolved geochemistry and high-precision U-Pb geochronology of zircons allow quantification of magmatic processes leading to porphyry emplacement and Au-Cu ore formation at Ok Tedi, the Earths youngest giant porphyry-skarn deposit. Trace element contents in zircons were obtained by laser ablation-inductively coupled plasma-mass spectrometry before selected grains were removed from the sample mount, chemically abraded, spiked, and dissolved for high-precision U-Pb geochronology by chemical abrasion-isotope dilution-thermal ionization mass spectrometry. U-Pb geochronology by laser ablation-sector field-inductively coupled plasma-mass spectrometry on abundant inherited zircon cores that occur in all intrusions together with Hf isotope analyses by solution multicollector-inductively coupled plasma-mass spectrometry permitted further assessment of the degree of crustal assimilation of the upper crustal magma reservoir. The combined chemical data and precise crystallization ages of zircons indicate closed system fractional crystallization and concurrent cooling in a common magma reservoir, from which the intrusions at Ok Tedi were successively extracted. Inherited zircon populations and Hf isotope analyses of Pleistocene zircons record lower crustal assimilation with Proterozoic basement. Based on cathodoluminescence (CL) imaging a chemically distinct zircon population with low Th/U was identified in the youngest synore intrusive rocks. These zircons indicate injection of a distinct magma into the common magma reservoir, which triggered the emplacement of the youngest porphyry, intrusion of a polymictic breccia with partly igneous matrix, and intimately associated hydrothermal Au-Cu mineralization. Crystallization ages of chemically characterized zircon crystals extend over a total time span of 212 ± 44 k.y., recording the minimum duration of fractional crystallization in the large magma reservoir from the time it reached zircon saturation. The youngest zircons in each intrusion resolve the emplacement of early thorite intrusions, low-grade monzodiorite porphyries, including the Sydney monzodiorite and Fubilan porphyry, into three time-resolved pulses separated by a total of ~160 k.y. The Sydney monzodiorite contains barren quartz veins and produced endoskarn and exoskarn; however, the exact timing of skarn-hosted Au-Cu mineralization is not yet clear. The emplacement of the ore-bearing Fubilan porphyry and the intrusive breccia overlap at 1.187 ± 0.022 Ma, constraining the time and duration of porphyry emplacement with associated Au-Cu mineralization. The injection of a distinct, probably more mafic magma batch into the magma reservoir preceded the emplacement of the Fubilan porphyry and the intrusive breccia by less than the resolution of 30 k.y., indicating that this event was the immediate trigger for Au-Cu mineralization at Ok Tedi. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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6. Pedunculated gastritis cystica profunda polyp presenting with upper GI bleeding and volcano-like surface alteration.
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Zimmer, Vincent and Heinrich, Christoph
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- 2022
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7. Lithology and Hydrothermal Alteration Control the Distribution of Copper Grade in the Prominent Hill Iron Oxide-Copper-Gold Deposit (Gawler Craton, South Australia).
- Author
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SCHLEGEL, TOBIAS U. and HEINRICH, CHRISTOPH A.
- Subjects
COPPER mining ,PETROLOGY ,HYDROTHERMAL alteration - Abstract
The Prominent Hill iron oxide-copper-gold (IOCG) deposit, located in the Gawler craton of South Australia, contains ca. 278 million metric tons (Mt) of ore at 0.98% Cu, 0.75 g/t An, and 2.5 g/t Ag. In contrast to the predominantly granite-hosted Olympic Dam IOCG deposit, Prominent Hill is mainly within unmetamorphosed sedimentary rocks comprising coarse clastic to laminated argillaceous lithologies with some volcaniclastic components and variable carbonate, including local massive dolomite. Essentially unmetamorphosed sedimentary rocks and structurally underlying mafic to intermediate-composition lavas, inferred to be members of the lower Gawler Range Voleanics, host the economically mineralized hematite breccias. The volcanic-sedimentary package was downfaulted and tilted along a major east-west fault, north of which similar but regionally low-grade metamorphosed rocks were affected by subeconomic skarn mineralization, and (on a more regional scale of the Mount Woods domain) intruded by granitic and gabbroic bodies. Hydrothermal alteration and mineralization at Prominent Hill involved pervasive and texturally destructive replacement of formerly calcareous, dolomitic, and siliciclastic breccia components. Hydrothermal alteration minerals comprise hematite, magnetite, siderite, ankerite, quartz, sericite, chlorite, kaolinite, fluorapatite, fluorite, barite, REE-U minerals (including monazite), uraninite, and coffinite, together with Cu sulfides including chalcopyrite, bornite, and chalcocite in the highest grade ore. Brecciation and replacement caused mechanical mixing as well as chemical alteration of primary lithologies, such that sedimentary contacts became obscured. Mass-balance calculations identify Al, Ti, Si, and Zr as least mobile components during hematite-chlorite-sericite to weak hematite-quartz alteration. Because Zr was not regularly assayed in drill cores, we use concentration ratios of Ti, Al, and Si from the deposit-scale assay database to delineate the distribution of lithochemical units prior to hydrothermal alteration and Cu mineralization. The resulting lithochemical model, based on one horizontal and five vertical cross sections, is used as a basis for mapping alteration patterns calculated from molar (Fe + Si)/(Fe + Si + Al), K/Na, and K/Al ratios. These chemical patterns, in conjunction with mineral stoichiometry, indicate that the spatial distribution of hematite, chlorite, variably phengitic sericite (and/or illite) ± kaolinite ± quartz-bearing alteration is superimposed on the pattern of interpreted lithologic contacts. The alteration patterns confirm visual logging results, showing that hematite enrichment correlates only partially with the distribution of Cu grades of >0.25 wt %. A subvertical body of complete replacement by hematite and quartz with consistent but subeconomic gold enrichment forms a Cu-barren core in the central and eastern parts of the deposit. Zones of increasing K/Al and K/Na ratios extend upward and westward from this Cu-barren core, transgressively overprinting lithologic contacts. The degree of hematite-quartz replacement can be measured by a hematite-quartz alteration index, here termed the HMSI value [(Fe + Si)/(Fe +Si + Al)], which inversely correlates with the normal probability for Cu grade. Areas of highest Cu grade (>1 wt %) spatially correlate with irregular zones having intermediate molar alteration indices: 0.34 < K/Al < 0.40, 20 < K/Na < 36, and HMSI < 0.98. Hematite breccias and Cu ore deposition developed after tilting of the host sequence into its present steep orientation, as indicated by geopetal structures within the breccia matrix. Thus, the economic mineralization occurred late in the deformational history of the region and after extrusion of the lower Gawler Range Voleanics. The formation of the Prominent Hill orebodies occurred during or after upthrusting of deeper seated rocks containing subeconomic Cu in skarns north of the fault. Faulting as well as ore formation may be related to orogenic processes in the central and northern part of the Mount Woods domain. Iron oxide introduction was decoupled from, and at least partly preceded, hydrothermal deposition of high-grade Cu. Geochemical and petrographic data indicate that economic Cu mineralization occurred together with mildly acidic hematitechlorite-sericite ± siderite alteration of originally carbonate-, illite-, and feldspar-bearing sedimentary rocks. The presence of copper enrichment wath an intermediate degree of cation leaching from the host rocks indicates that pH neutralization of initially highly acidic metal-transporting fluids was an essential factor causing Cu sulfide deposition. Distinct ranges in Na-K-Al ratios and low HMSI values offer potential as exploration indicators pointing toward higher ore grades. These results from Prominent Hill are consistent with recently published mineralogical studies at the giant Olympic Dam deposit, indicating similar ore depositional controls despite lithologically different host rocks. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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8. The endoscopic "hide-bound" bowel sign in systemic sclerosis.
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Zimmer, Vincent and Heinrich, Christoph
- Published
- 2021
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9. The Serra Pelada Au-Pd-Pt Deposit, Carajás, Brazil: Geochemistry, Mineralogy, and Zoning of Hydrothermal Alteration.
- Author
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BERNI, GABRIEL V., HEINRICH, CHRISTOPH A., LOBATO, LYDIA M., WALL, VICTOR J., ROSIÈRE, CARLOS A., and FREITAS, MARCELO A.
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HYDROTHERMAL alteration ,IRON oxides ,COPPER research ,GOLD ,HYDROTHERMAL deposits - Abstract
The Serra Pelada Au-Pd-Pt deposit is located within the Carajás mineral province, which also hosts the world-class iron ore and iron oxide-hosted copper-gold deposits of the Amazon craton in Brazil. The unusual low-temperature hydrothermal mineralization at Serra Pelada is epigenetic, hosted by metasedimentary rocks of the Águas Claras Formation and structurally localized in the Serra Pelada overturned syncline. The orebodies are controlled by the intersection of subvertical NE-trending fault zones with metasiltstones, mainly at the syncline's hinge, with minor ore occurrences at the upper and lower limb. Intense tropical weathering over the last 70 m.y. has completely overprinted the shallow ore in and near the flooded open pit, but primary hydrothermal features are preserved in deeper drill core delineating the remaining resource. Gold, platinum, and palladium mineralization is associated with intense argillic alteration, hematite breccias, and silicification, with the highest grade ore hosted by brecciated metasiltstones that are highly enriched in amorphous carbon. Distal alteration zones comprise a reducing and oxidizing alteration front. The hydrothermal mineral paragenesis comprises kaolinite, quartz, sericite, amesite (Mg-rich Al-silicate), amorphous carbon, hematite, monazite, rutile, pyrite, and a complex assemblage of Bi-, Ag-, Pb-, Cu-, Co-, Ni-, Pt-, Pd-, and Au-bearing, chalcogenide (S, Se), and arsenide (As, Sb) minerals. Major element changes during hydrothermal alteration include C and Mg addition, K depletion, localized silica loss, and silicification with notable introduction of trace elements including light rare earth elements (LREE), Bi, Pb, U, V, Cu, Co, Ni, and As. The hydrothermal alteration and element association of the Serra Pelada deposit show geochemical similarities with unconformity-related uranium deposits, which may also be enriched in Au, Pd, and Pt and were formed by mixing of fluids that interacted with a highly oxidized cover sequence and highly reduced rock packages in structures of brittle-ductile strain. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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10. Direct endoscopic visualization of putative biliary tract pneumatosis cysts by ultraslim cholangioscopy.
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Zimmer, Vincent and Heinrich, Christoph
- Published
- 2021
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11. Melt and Fluid Inclusions in Hydrothermal Veins: The Magmatic to Hydrothermal Evolution of the Elatsite Porphyry Cu-Au Deposit, Bulgaria.
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STEFANOVA, ELITSA, DRIESNER, THOMAS, ZAJACZ, ZOLTAN, HEINRICH, CHRISTOPH A., PETROV, PARASKEV, and VASILEV, ZLATI
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FLUID inclusions ,INCLUSIONS (Mineralogy & petrology) ,HYDROTHERMAL deposits ,CATHODOLUMINESCENCE - Abstract
The magmatic to hydrothermal transition in the Late Cretaceous Elatsite porphyry Cu-Au-(Mo-platinum group element) deposit has been studied in a suite of samples with clear timing relations between porphyry dikes, magmatic-hydrothermal veins, silicate melt inclusions in quartz veins, fluid inclusion generations, and ore minerals. Ore mineralization occurs late, at temperatures ~200° to 300°C below those of the early, multistage interplay between magmatic and hydrothermal processes at near-magmatic temperature-pressure conditions. Crosscutting relations and petrography indicate that shortly after the intrusion of the earliest, monzodioritic dikes, fluids precipitated a first generation of granular quartz veins accompanied by potassic alteration. The second vein generation with crystalline quartz textures and K-feldspar alteration halos formed at the same time as the second, granodioritic pulse of porphyry intrusions. Cathodoluminescence imaging of quartz growth textures reveals that the earliest fluid inclusions in the crystalline quartz veins are of intermediate density and ~8 wt % NaCl equiv salinity, probably trapped at near-lithostatic pressures of ~1,200 to 1,300 bars at near-magmatic temperatures (≤730°C), and implies a depth of ~4 to 5 km. Depressurization led to phase separation, indicated by a first generation of coexisting brine and vapor inclusions trapped at temperatures of ≥640°C and suprahydrostatic pressures of ≥920 bars. A second quartz generation in crystalline quartz veins precipitated during progressive depressurization and hosts assemblages of coexisting brine, vapor, and silicate melt inclusions, trapped at temperatures in excess of 600°C and suprahydrostatic pressures of 630 to 880 bars. Some open-spaced quartz veins were filled with aplite during this stage. Field relations and geochemical evidence suggest that the aplites as well as the silicate melt inclusions in hydrothermal quartz veins represent volumetrically minor residual melts that evolved directly from granodiorite porphyries at the level of deposit formation, and do not represent aliquots of metal-supplying magma at depth. Fluid inclusions coexisting with the silicate melt inclusions are metal rich, but these fluids predate sulfide precipitation and are, therefore, not the dominant fluids responsible for the Cu-Au mineralization at Elatsite. Melt-fluid-metal separation processes recorded in these co-trapped silicate melt and fluid inclusions in vein quartz are small-scale, local phenomena and do not appear to be suited for understanding and quantifying metal segregation in the deeper source. Microthermometry data of fluid inclusions, trapped during the later stages of the formation of the second quartz generation, show further depressurization to ~260 to 325 bars and cooling to ~460°C, representing a hot hydrostatic regime. Bornite, chalcopyrite, and magnetite seem to be slightly later precipitated at temperatures ≤460°C in separate veins or opened spaces of preexisting veins. Dissolution textures of the second quartz generation indicate a subsequent local redissolution of vein quartz, most likely as a result of passing through a window of retrograde quartz solubility upon further cooling below 460°C. The next, economically most important chalcopyrite-pyrite stage is largely devoid of quartz precipitation and is mostly expressed as "paint veins." Due to the lack of fluid inclusions, the temperature-pressure conditions of formation of these veins could not be constrained. The waning phase of hydrothermal activity is represented by a quartz-carbonate-zeolite stage, formed at low temperature (~145°C), as indicated by microthermometry of fluid inclusions trapped in quartz from this stage. Laser ablation-inductively coupled plasma-mass spectrometry analyses of fluid inclusions show very high Cu contents in early intermediate-density fluid inclusions and in the first vapor inclusion generation, followed by a drastic decrease in the second generation of vapor inclusions. The decrease correlates with the appearance of anhydrite inclusions in the second quartz generation and may indicate that a lack of sulfur in these later vapor inclusions led to Cu partitioning into the brine. Alternatively, it is also possible that, unlike early vapor inclusions, the later vapor inclusions were not susceptible to postentrapment copper enrichment, in accordance with recent experiments. A progressive Cu enrichment in the brine phase correlates well with depressurization prior to mineralization. Mass balance considerations based on analyzed fluid components and fluid phase relations indicate that brine was volumetrically minor and therefore likely stagnant, but this may have prepared ore precipitation by accumulating Cu stripped from ascending vapor. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
12. The Porphyry Cu-(Mo-Au) Deposit at Altar (Argentina): Tracing Gold Distribution by Vein Mapping and LA-ICP-MS Mineral Analysis.
- Author
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ZWAHLEN, CARMEN, CIOLDI, STEFANIA, WAGNER, THOMAS, REY, ROGER, and HEINRICH, CHRISTOPH
- Subjects
PORPHYRY ,MINERALIZATION ,PLIOCENE Epoch ,PYRITES ,STATISTICAL correlation - Abstract
The Altar porphyry Cu-(Mo-Au) deposit occurs in the Miocene to early Pliocene copper belt of the high Andes of western Argentina, close to the Chilean border. A cluster of late Miocene porphyries intruded a more extensive complex of early Miocene rhyolitic to andesitic volcanic and subvolcanic rocks. Potassic alteration in the Central Porphyry was partially overprinted by feldspar-destructive alteration and finally by argillic to advanced argillic alteration. Early stockwork veins have been cut successively by quartz-pyrite veins, tourmaline veins, and enargite veins. Based on correlation analysis of assay results and mapped abundances of these four vein types, we estimate that approximately 11 to 26% of the copper in the Altar orebody is associated with enargite veins, whereas the remainder is associated with the early stockwork veining and potassic alteration. Gold concentration is low compared with typical Cu-Au porphyries of the Andean back-arc region, but higher than in the giant Miocene deposits of Chile, at an average Au/Cu ratio of 0.14 x 10
-4 by weight across the Central Porphyry orebody at Altar. Gold is dominantly associated with chalcopyrite in the domain of stockwork veining and potassic alteration. Small-scale assays in combination with petrographic observations and laser ablation-inductively coupled plasma-mass spectrometry microanalyses show that a significant fraction of the gold in the stockwork veins is enclosed in pyrite as submicroscopic particles attached to inclusions of a Bi-Te-Pb-Ag-enriched Cu-Fe sulfide phase. Microscopic grains of native gold also occur along grain boundaries between pyrite and chalcopyrite, and rarely as larger particles in enargite veins. [ABSTRACT FROM AUTHOR]- Published
- 2014
- Full Text
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13. Fluid Evolution and Uranium (-Mo-F) Mineralization at the Maureen Deposit (Queensland, Australia): Unconformity-Related Hydrothermal Ore Formation with a Source in the Volcanic Cover Sequence.
- Author
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HURTIG, NICOLE C., HEINRICH, CHRISTOPH A., DRIESNER, THOMAS, HERRMANN, WALTER, WALL, VIC, and MATHISON, IAN
- Subjects
MINERALIZATION ,ORE deposits ,HYDROTHERMAL deposits ,VOLCANIC ash, tuff, etc. ,ECONOMIC geology - Abstract
Maureen is the largest among several U (-Mo-F) prospects occurring along a Late Devonian unconformity in the Georgetown area, northern Queensland, Australia. Mineralization is structurally controlled by the intersection of steep east-west fractures with an unconformity between a Proterozoic basement and a Paleozoic cover sequence of continental sedimentary rocks and abundant rhyolitic volcanic rocks. The mineralogical composition of high-grade ore (pitchblende + Fe-rich molybdenite + arsenopyrite + arsenian pyrite + fluorite + dickite + chlorite + goyazite ± graphite or hematite), postlithification brecciation, and quartz dissolution indicate a strong chemical gradient and disequilibrium during mineralization between the reduced basement and the largely oxidized cover sequence. Elemental and mineral zonation centered to faults, and fractures cutting the unconformity, indicates locally reducing and quartz-dissolving conditions during the formation of tabular U-Mo orebodies, which are surrounded by a halo rich in fluorite. A detailed pétrographie study, microthermometry, and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analyses of quartz- and fluorite-hosted fluid inclusions provide concentrations of ore- forming components in fluids related to hydrothermal uranium mineralization. Three fluids were involved in the mineralizing process at Maureen: a likely oxidized saline (L3) fluid, an aqueous (LI) fluid, and a CH4-bearing carbonic vapor (cV). The oxidized saline (L3) fluids trapped in fluorite and dicldte-bearing hydrothermal quartz veinlets crosscutting detrital quartz show the highest average concentrations of U (10-47 ppm), Mo (489-888 ppm), and As (318-777 ppm), with element ratios close to those of high-grade mineralized rocks. We suggest that aqueous (LI) fluids mixed in the cover sequence with oxidized saline fluids (L3) to precipitate fluorite as a distal halo, surrounding the east-west fractures. Their mixture, an oxidized moderately saline fluid (L2), reacted with methane-bearing carbonic vapor (cV) to precipitate U and Mo by reduction, close to the intersection of the fractures with the unconformity. Geochemical analysis of coexisting vapor and liquid assemblages indicate mixing of oxidized saline fluids with reduced carbonic vapors to be the driving force for uranium precipitation. The Maureen deposit shares essential geologic characteristics and hydrothermal processes with Proterozoic unconformity-related U deposits, but probably owes its unusual element association of U with (equally redox sensitive) Mo and abundant F to a source region in the volcano-sedimentary cover sequence that was enriched in these elements, due to the presence of highly fractionated, easily leachable, and oxidizable felsic volcanics. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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14. Witwatersrand gold deposits formed by volcanic rain, anoxic rivers and Archaean life
- Author
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Heinrich, Christoph A.
- Abstract
The Witwatersrand Basin in South Africa is one of the best-preserved records of fluvial sedimentation on an Archaean continent. The basin hosts the worlds biggest gold resource in thin pebble beds, but the process for gold enrichment is debated. Mechanical accumulation of gold particles from flowing river water is the prevailing hypothesis, yet there is evidence for hydrothermal mobilization of gold by fluids invading the metasedimentary rocks after their burial. Earth’s atmosphere three billion years ago was oxygen free, but already sustained some of the oldest microbial life on land. Here I use thermodynamic modelling and mass-balance calculations to show that these conditions could have led to the chemical transport and precipitation of gold in anoxic surface waters, reconciling the evidence for fluvial deposition with evidence for hydrothermal-like chemical reactions. I suggest that the release of sulphurous gases from large volcanic eruptions created acid rain that enabled the dissolution and transport of gold in surface waters as sulphur complexes. Precipitation of the richest gold deposits could have been triggered by chemical reduction of the dissolved gold onto organic material in shallow lakes and pools. I conclude that the Witwatersrand gold could have formed only during the Archaean, after the emergence of continental life but before the rise of oxygen in the Earth’s atmosphere.
- Published
- 2015
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15. Source Plutons Driving Porphyry Copper Ore Formation: Combining Geomagnetic Data, Thermal Constraints, and Chemical Mass Balance to Quantify the Magma Chamber Beneath the Bingham Canyon Deposit.
- Author
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STEINBERGER, INGO, HINKS, DONALD, DRIESNER, THOMAS, and HEINRICH, CHRISTOPH A.
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PORPHYRY ,COPPER ,MAGMAS ,COPPER mining ,GEOMAGNETISM ,MAGNETIC susceptibility ,BINGHAM Copper Mine (Utah) - Abstract
The formation of porphyry copper deposits requires a focused flux of magmatic fluid, expelled from a large reservoir of water-, metal-, and sulfur-rich magma. The dimensions of this usually hidden magma reservoir are difficult to determine but can be constrained by combining geophysical observations with thermal constraints and the mass balance imposed by the chemical enrichment of elements in the deposit. Here we show that an internally consistent scenario can be derived for the world-class Cu-Mo-Au deposit at Bingham Canyon (Utah, United States), which quantifies the essential characteristics, approximate dimension, and temporal evolution of a large pluton that generated the deposit. The mineralized district shows a distinct WSW-ENE-striking magnetic anomaly indicating a large intrusive body underlying the sedimentary host rocks of the Oquirrh Mountains. Modeling the deep body by geomagnetic methods is possible because of the high contrast in magnetic susceptibility between sedimentary host rocks and intrusive rocks and because a former volcanic edifice is largely eroded. Additional constraints from drilled geology and district-wide outcropping rocks, including partial demagnetization by hydrothermal alteration on the mine scale, restrict the range of possible solutions to a broadly laccolith-shaped intrusion with a volume of approximately 1,400 to 3,000 km³. From the roof of the laccolith, several smaller subvolcanic stocks and dikes protrude to the present surface, of which a major one is hosting the Bingham Canyon deposit. The roof of the laccolith probably lies between 2 and 3.5 km below the bottom of the present open-pit mine, and the average thickness of the laccolith is constrained between 2 and 3.5 km. Thermal modeling, using pluton dimensions derived from the geologic and geomagnetic modeling, indicates that a single laccolith with a magma volume of -2,000 km³ beneath Bingham would have solidified within about 230,000 years or less. Comparison of the thermal models with published high-precision geochronologic data and petrologic constraints suggests a scenario in which about 1,000 km³ of magma was encapsulated by inward crystallization of the pluton after the preore equigranular monzonite stocks solidified and extrusive volcanism was probably terminated. This encapsulated reservoir was close to water saturation and contained approximately 150 billion metric tons (Gt) of magmatic water for subsequent closed-system fractionation and eventual fluid expulsion driving porphyry copper mineralization. Chemical mass balance shows that the known metal endowment and mapped mass of vein quartz within the deposit can be advected and precipitated by a fluid mass that is slightly smaller than the available 150 Gt of water. A conservative estimate indicates that 115 Gt of water is sufficient to precipitate all the quartz associated with successive Cu-Au- and Mo-stage veins as well as their barren precursors. According to our thermal model, approximately 250 km³ of quartz monzonite magma with a temperature of about 690°C remained partially liquid some 215,000 years after initial intrusion of the laccolith. At that point, it expelled almost simultaneously the quartz monzonite porphyry and the main mass of accumulated fluid, generating most of the vein quartz in the quenched porphyry and the adjacent older rocks. Petrographic evidence indicates that the ore metals precipitated near the end of individual pulses of quartz veining that followed recurrent but waning pulses of porphyry intrusion. Considering published experimental solubility data as well as ore metal contents in fluid inclusions, a small fraction of the available fluid mass is sufficient to transport and precipitate all the ore metals after an initial fluid pulse precipitated most of the quartz. However, the total amount of sulfur present in the deposit, which includes Cu and Mo sulfides as well as a major addition of pyrite, would be facilitated by addition of a mafic magma input into the residual magma chamber that contained the evolved felsic magma. This magmatic injection probably triggered the emplacement of the mineralized porphyries, consistent with the more mafic composition of some of the latest porphyry dikes and the CO
2 -rich nature of ore-related fluid inclusions. [ABSTRACT FROM AUTHOR]- Published
- 2013
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16. Fluid-Flow Patterns at Brothers Volcano, Southern Kermadec Arc: Insights from Geologically Constrained Numerical Simulations.
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GRUEN, GILLIAN, WEIS, PHILIPP, DRIESNER, THOMAS, DE RONDE, CORNEL E. J., and HEINRICH, CHRISTOPH A.
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VOLCANOES ,GEOLOGY ,CALDERAS ,VOLCANISM ,PERMEABILITY - Abstract
Numerical, multiphase pure-water simulations were performed to study the first-order geologic and physical parameters controlling the style and distribution of hydrothermal venting at Brothers volcano, southern Kermadec arc, New Zealand. By comparing the results for different permeability scenarios, we can show that the location of venting on the inner slopes of the caldera (e.g., at the NW caldera site) requires the presence of higher permeability faults. Venting at the top of the Upper cone develops naturally by hydrothermal flow in porous rocks above an underlying magma body. However, this magmatic reservoir cannot alone account for present-day hydrothermal venting at the NW caldera site, which implies that a larger magma chamber, which was responsible for caldera collapse, is still active. Modeled venting temperatures for scenarios with homogeneous host-rock permeability correspond well with formation temperatures determined by sulfate-sulfide mineral pairs from different vent sites at Brothers volcano. Direct measurements of vent fluids at the NW caldera site today, however, show higher temperatures than modeled. This may be due to rapid ascent of hot fluids in individual fractures that are not resolved in the simulations. At the cone sites, measured temperatures are lower than modeled, likely the result of mixing with ambient seawater in near-surface permeable rocks. The inferred presence of a constant magmatic fluid source underneath the volcanic edifice leads to a more rapid development of the hydrothermal circulation and stabilizes the system at higher temperatures. We suggest that the hydrothermal evolution and fluid-flow patterns at Brothers volcano are controlled by episodes of varying magmatic fluid input into a seawater-dominated convection system. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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17. Separation of Molybdenum and Copper in Porphyry Deposits: The Roles of Sulfur, Redox, and pH in Ore Mineral Deposition at Bingham Canyon.
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Jun Hun Seo, Guillong, Marcel, and Heinrich, Christoph A.
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PORPHYRY ,MONZONITE ,RAMAN spectroscopy ,LASER ablation ,PERMEABILITY ,HYDROSTATICS - Abstract
The giant Bingham Canyon porphyry Cu-Mo-Au deposit (Utah) is associated with Eocene sub volcanic intrusions. It shows a distinct metal zonation above a barren core, with dominantly shallow Cu-Au mineralization (Cu stage) following the early quartz monzonite porphyry (QMP) intrusion, and spatially deeper Mo mineralization (Mo stage) occurring in a separate vein set exclusively after a late quartz latite porphyry (QLP) intrusion that truncates earlier Cu-Au veins. To understand this metal separation and the geochemical process of molybdenite mineralization, we investigated fluid inclusions by microthermometry, Raman spectroscopy, and laser ablation inductively couple plasma mass spectrometry (LA-ICP-MS) microanalysis in low- and high-grade quartz veins of both mineralization stages. In deep, low-grade quartz veins interpreted to represent the root zone of the Cu stage we found high concentrations of Cu, S, and Mo in the fluid inclusions, whereas in low-grade Mo-stage veins, we found lower Cu, but similar concentrations of S and Mo, compared to the inferred input fluids to the Cu stage. Sulfur and copper concentrations were similar in intermediate-density-type fluid inclusions in deep low-grade Cu-stage samples, whereas intermediate-density-type inclusions in low-grade Mo-stage veins have S contents that exceed their Cu contents. In high-grade Mo-stage vein, we found large variations of Mo concentrations in coexisting brine and vapor inclusions. Compared to the P-T conditions of the Cu precipitation stage (90-260 bars and 320°-430°C), the Mo-precipitating fluids were trapped at higher pressures and temperatures of 140 to 710 bars and 360° to 580°C. Mass-balance calculation based on the compositions of intermediate-density inclusions and brine + vapor assemblages, interpreted to be derived by phase separation during decompression of the ascending single-phase intermediate-density fluid, indicate that the mass of vapor phase exceeded that of brine by about 9:1 in both mineralization stages. Combining this mass balance with the analyzed vapor/brine partitioning data indicates that more than 70% of Mo and S (by mass) in the deposit were deposited from the vapor phase. Earlier Cu-Au deposition was similarly dominated by vapor, but recently published data about post entrapment Cu diffusion in and out of fluid inclusions cast doubt on previous quantifications, suggesting that almost none of the copper was deposited by brine. Mo is less likely to be modified by selective diffusion, and high Mo contents (max 0.0054 Mo/Na in intermediate density; 380 µg/g Mo in brine) in the hydrothermal fluids were maintained from the early Cu stage to the late Mo stage. This indicates that Mo concentration was not the decisive (actor for separate precipitation of late Mo ore at Bingham Canyon. Instead, the metal separation may be explained by a reduction in redox potential and an increase in acidity in the evolving source region of the fluids, i.e., a large sub volcanic magma reservoir. This is indicated by the stoichiometry of chalcopyrite and molybdenite precipitation reactions, a tentative difference in the Fe/Mn ratio in fluids of veining stages, incipient muscovite alteration along high-temperature molybdenite veins, and an increasing tendency for Mo to fractionate from brine to vapor. We suggest that the early Cu-stage fluids were slightly more oxidized and neutral, allowing Cu-Fe sulfides to saturate first, while molybdenite saturation was suppressed and Mo was lost from the early ore stage. By contrast during the later Mo stage, the fluids were more reduced and acidic, thereby allowing selective saturation of molybdenite as the first precipitating sulfide in the cooling and expanding two-phase fluid, consistent with textural observations. This interpretation may imply more generally that small differences in redox potential and acid/base balance of the magmatic source of porphyry-mineralizing systems may be decisive in the temporal and spatial separation of the two metals. [ABSTRACT FROM AUTHOR]
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- 2012
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18. Scissor‐type knife stalk transection for a difficult‐to‐access pedunculated colorectal lesion
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Zimmer, Vincent and Heinrich, Christoph
- Published
- 2021
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19. Direct Analysis of Ore-Precipitating Fluids: Combined IR Microscopy and LA-ICP-MS Study of Fluid Inclusions in Opaque Ore Minerals.
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KOUZMANOV, KALIN, PETTKE, THOMAS, and HEINRICH, CHRISTOPH A.
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FLUID inclusions ,ORES ,LASER ablation ,INDUCTIVELY coupled plasma mass spectrometry ,PORPHYRY - Abstract
Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) in combination with near-infrared microscopy of fluid inclusions hosted by ore minerals that are opaque to visible light can provide the composition of ore-precipitating fluids. We applied the two techniques to well-constrained fluid inclusion assemblages hosted by pyrite, enargite, and quartz to trace the sortie and evolution of the fluids in high-sulfidation epithermal veins overprinting a porphyry copper deposit at Rosin Poieni, Romania. Despite some analytical limitations caused by the sulfide host minerals, the data demonstrate that fluids trapped in apparently cogenetic quartz and ore minerals are chemically different. Systematic changes in major and trace element ratios between liquid-vapor, vapor-rich, and brine fluid inclusion assemblages in the three minerals record an evolving fluid source at the porphyry to epithermal transition. Regarding their Cs/(Na + K) ratios, most of epithermal quartz-hosted fluid inclusion assemblages form a well-defined cluster, which coincides with the narrow range of the porphyry-stage fluids trapped in early quartz of the porphyry stockwork veins. Their Cu/(Na + K) ratios are 10 to 100 times lower compared to the pyrite-hosted inclusions and correspond to the lowest Cu/(Na + K) ratios recorded for the porphyry-stage fluids. By contrast, pyrite-bested, vapor-rich fluid inclusions have the highest Cu/(Na + K) similar to the highest Cu/(Na + K) ratios measured in the porphyry-stage fluid inclusions. The results led to the conclusion that the gangue and ore minerals in the high-sulfidation epithermal veins at Rosin Poieni formed by successive pulses of chemically distinct hydrothermal fluids that were successively exsolved from residual melt batches of a progressively crystanizing magma at greater depth. These results are consistent with detailed textural observations, but petrography alone could not have led to this unambiguous conclusion. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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20. The Bingham Canyon Porphyry Cu-Mo-Au Deposit. III. Zoned Copper-Gold Ore Deposition by Magmatic Vapor Expansion. .
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LANDTWING, MARIANNE R., FURRER, CAROLINE, REDMOND, PATRICK B., PETTKE, THOMAS, GUILLONG, MARCEL, and HEINRICH, CHRISTOPH A.
- Subjects
COPPER ores ,GOLD ores ,ORE deposits ,EXPANSION of vapors ,PORPHYRY ,FLUID inclusions ,BINGHAM Copper Mine (Utah) - Abstract
Fluid inclusion microthermometry and laser-ablation ICPMS microanalysis are combined with geological and textural observations to reconstruct the spatial and temporal evolution of magmatic fluids that formed the subvolcanic porphyry Cu-Au(-Mo) ore deposit at Bingham Canyon, Utah. The Bingham Canyon orebody is exposed over ∼1.6 km vertically and has the shape of an inverted cup with distinct metal zoning. Fluid inclusions in the barren but highly veined and potassically altered deep center of the system have intermediate density (∼0.6 g cm
-3 ) and a salinity of ∼7 wt percent NaCl equiv. They have subequal concentrations of Na, K, Fe, and Cu and contain minor CQ2 . The intermediate-density fluids were trapped as a single phase, mostly at >500°C and >800 bars. The Au-Cu-rich center near the top of the orebody contains low-density vapor inclusions (-0.2 g cm-3 ) coexisting with brine inclusions containing ∼45 wt percent NaCl equiv. The vertical transition of different inclusion types indicates phase separation of the single-phase input fluid upon volume expansion associated with a pressure drop to 200 ± 100 bars. Mass-balance calculation based on all analyzed inclusion components indicates that the mass of the vapor phase exceeded that of the brine by ∼9/1. The vapor contained Cu as its dominant cation (∼1.5 wt %) and contributed about 95 percent of the total amount of copper transported to the base of the orebody. Bornite, chalcopyrite, and native gold were precipitated in a narrow temperature interval from 430° to 350°C, into secondary pore space created by local redissolution of vein quartz as a result of retrograde quartz solubility in the vapor-dominated fluid system. Intermediate-density fluid inclusions in the deepest parts of the peripheral copper ore zone have identical density and composition, including similar gold contents, as those in the deep center. Microthermometry and statistical estimation of phase proportions in the inclusions show that the vapor in the peripheral Cu-rich but Au-poor ore zone remained denser, and the separating brine was less saline (∑36 wt % NaCl equiv), compared to vapor and brine in the central Au-Cu ore zone. This indicates that the peripheral fluids experienced a lower degree of phase separation, due to slightly higher fluid pressure at equivalent temperature, compared to more strongly expanding fluids in the center of the system. The systematic zoning of Au/Cu within the ore shell, despite compositionally similar input fluids, is interpreted to have resulted from slightly different pressure-temperature-density evolution paths of magmatic fluids. Copper was selectively precipitated in the peripheral ore zone, in contrast to complete coprecipitation of Au and Cu in the central upflow zone of the vapor plume. The formation of particularly rich Cu-Au ore in the center of the upward-expanding fluid plume is consistent with published experimental data, showing that the solubility of metals in hydrous vapor decreases sharply with falling pressure, due to destabilization of the hydration shell around metal complexes in expanding vapor. Tiffs interpretation supports the classic vapor plume model for porphyry copper ore formation but additionally emphasizes the role of sulfur-bearing complexes as a key chemical control on magmatic-hydrothermal metal transport and the deposition of Cu and Au in porphyry ores. Our interpretation of selective Cu ± Au precipitation as a function of vapor density can explain the more general observation that most gold-rich porphyry copper deposits are formed in shallow sub-volcanic environments, whereas deeper seated porphyry Cu-(Mo) deposits are generally gold poor. [ABSTRACT FROM AUTHOR]- Published
- 2010
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21. The Bingham Canyon Porphyry Cu-Mo-Au Deposit. II. Vein Geometry and Ore Shell Formation by Pressure-Driven Rock Extension. .
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GRUEN, GILLIAN, HEINRICH, CHRISTOPH A., and SCHROEDER, KIM
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VEINS (Geology) ,ORE deposits ,PORPHYRY ,COPPER ores ,MOLYBDENUM ores ,GOLD ores ,BINGHAM Copper Mine (Utah) - Abstract
Copper, gold, and molybdenum in the Bingham Canyon deposit (Utah, United States) show a systematic distribution in grade and metal ratios. Most Cu-Au mineralization follows, both spatially and temporally, the emplacement of the quartz monzonite porphyry (QMP), a southwest-northeast-elongated thick dike intruding along the contact between the premineralization equigranular monzonite stock and surrounding sedimentary rocks. Copper ore grades define the shape of an inverted cup, which is centered on the QMP but has a much broader, near-circular footprint. Several deep root zones surround a barren core occupied by the same litho-logic units and intense potassic alteration but insignificant metal tenor. Throughout the deposit, gold to copper ratio is systematically zoned. The distribution of molybdenum resembles that of copper and partly overlaps with it, but the molybdenum ore shell is generally displaced inward and downward from the copper ore shell. Systematic measurement of the abundance and orientation of three major vein types obtained at the pit surface were complemented with unoriented vein density data from drill core logging. Quartz stockwork veins, the earliest and most abundant of the mapped vein types, are related to potassic alteration and major Cu-Au mineralization. Their greatest vein density follows the intrusion of the QMP but extends far beyond, into sedimentary rocks and especially into adjacent parts of the pre-ore equigranular monzonite. Their orientation is predominantly steep, with a variable strike. Quartz-molybdenite veins postdate all intrusions and are less abundant than quartz stockwork veins. They show variable orientation of strikes mad a weaker tendency to steep dips. Quartz-pyrite veins with sericitic alteration halos crosscut all intrusions and earlier veins. They are rare within the central high-grade part of the deposit and predominantly occur near and outside the northeastern and southwestern ends of the QMP. They have a strongly preferred orientation parallel to the porphyry (likes, with steep dips and strike directions fanning out radially from the center of the deposit. Repeated cycles of dike intrusions with distinct southwest-northeast orientation, followed by steep stockwork veins with variable strikes distributed over the broad ore shell and a final return to oriented postore veins are interpreted to result from alternation between two stress regimes. A regional, probably weakly transtensional regime controls the emplacement of dikes and postore veins. Ore vein formation and mineralization is controlled by active rock extension (increase in differential stress) in the roof area above a broad region of high fluid pressure in a subjacent magma chamber, rather than by local hydrofracturing caused by fluid exsolution from the porphyries (decrease in effective rock pressure and positive volume change upon magma crystallization). Shallow vein mineralization well above the lithostatic-to-hydrostatic transition is consistent with low (hydrostatic or even vapor-static) pressures of ore deposition indicated by a companion study of fluid inclusions. The process of pressure-driven roof extension favors the accumulation of metals in high-grade ore shells, compared to temperature-driven concepts according to which the porphyry mineralization is spread out vertically by following downward-retracting isotherms in a cooling magmatic-hydrothermal system. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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22. Sediment-Hosted Gold Deposits in Guizhou, China: Products of Wall-Rock Sulfidation by Deep Crustal Fluids.
- Author
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WENCHAO SU, HEINRICH, CHRISTOPH A., PETTKE, THOMAS, XINGCHUN ZHANG, RUIZHONG HU, and BIN XIA
- Subjects
SEDIMENTS ,GOLD ,SULFIDATION ,ROCK-forming minerals ,OXIDE minerals - Abstract
Sediment-hosted gold deposits in Guizhou, China, are hosted in late Paleozoic and early Mesozoic sedimentary rocks along the southwest margin of the Precambrian Yangtze craton. They have characteristics similar to Carlin-type gold deposits in Nevada and are notably enriched in As, Sb, Hg, and Tl. The Shuiyindong and Yata deposits consist of disseminated, strata-bound sulfides in Permian bioclastic limestone and fault-con-trolled mineralization in Middle Triassic calcareous clastic rocks, respectively. Mineralization in both deposits consists of barren milky quartz veins, disseminated gold-bearing arsenian pyrite and arsenopyrite, stibnite, realgar, and orpiment. The barren milky quartz veins occur in the ore-controlling structures with an envelope of gold mineralization in the host rock consisting of disseminated gold-bearing arsenian pyrite and arsenopyrite and replacement-style quartz veinlets. Later drusy quartz, stibnite, realgar, and orpiment fill fractures and vugs on the periphery of gold mineralization. Petrography, microthermometry, laser Raman spectroscopy, and laser ablation inductively coupled plasma mass spectrometric (LA-ICP-MS) analyses of fluid inclusious are used to characterize the chemical evolution of ore fluids at Shuiyindong and Yata. Early barren milky quartz veins trapped aqueous fluid with moderate salinity (6.0 wt % NaCI equiv) and minor CO
2 (<2.4 mol %) at a temperature of 230° ± 30°C. This fluid contains measurable B, Na, K, Cs, Sr, As, Sb, and Au (3.8 ± 0.5-5.7 ± 2.3 µg/g) determined by LA-ICP-MS and is interpreted to approximate the mineralizing fluid responsible for precipitation of early barren quartz veins. Low-salinity (0.9-2.3 wt % NaCI equiv), CO2 -bearing (6.3-8.4 mol %), aqueous fluids are recorded in replacement-style quartz veinlets. They formed gold-beating arsenian pyrite and arsenopyrite and quartz veinlets at a temperature of 210° ± 20°C and pressures of 450 to 1,150 bars, corresponding to depths between 1.7 and 4.3 km under lithostatic conditions. Fluid inclusions in late stibnite-orpiment-realgar-quartz veins contain high CO2 (58-64 mol %) and N2 (19.2-23.7 mol %) with trace CH4 (up to 1.6 mol %). The increasing content of CO2 and decrease in the concentrations of Au and As in aqueous-carbonic inclusions are interpreted to result from carbonate dissolution at the level of the deposits during gold mineralization. Covariance of Au, As, Sb, and Sr concentrations in the fluids is interpreted to reflect deposition of As mad Sb sulfides and gold concurrent with carbonate crystallization. Iron is below detection limit (~400 µg/g) in all fluid inclusion types, suggesting that the ore fluids were Fe poor but possibly sulfur rich, possibly explaining their exceptionally high gold contents. Iron in sulfide minerals was probably derived from dissolution of ferroan minerals in the host rocks, sulfidized by H2 S-rich fluids to precipitate arsenian pyrite, arsenopyrite, and gold. Pressure fluctuation induced by faulting resulted in local fluid immiscibility and led to late deposition of realgar, orpiment, stibnite, and calcite. Hydrogen and oxygen isotope compositions of ore fluids (δD(H = -35 to -68‰, δ2 O)18 O(H = 4-16.5‰) indicate a metamorphic origin, possibly related to crustal thickening and prograde metamorphism during the late Yanshanian orogeny. [ABSTRACT FROM AUTHOR]2 O)- Published
- 2009
23. The Composition of Magmatic-Hydrothermal Fluids in Barren and Mineralized Intrusions.
- Author
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AUDÉTAT, ANDREAS, PETTKE, THOMAS, HEINRICH, CHRISTOPH A., and BODNAR, ROBERT J.
- Subjects
HYDROTHERMAL deposits ,IGNEOUS intrusions ,MAGMAS ,GRANITE ,IGNEOUS rocks ,SALINITY - Abstract
This paper addresses the question of whether or not there are fundamental differences in the composition of magmatic-hydrothermal fluids in barren versus variably mineralized systems, and if so, at which stage of magmatic-hydrothermal evolution the differences were generated. Combining microthermometry and laser ablation ICP-MS, we studied high-temperature, premineralization fluid inclusions in three barren granites, one Sn-W-mineralized granite, one porphyry Cu-mineralized intrusion, one porphyry Mo-mineralized intrusion, and one Th-U-REE--mineralized granite, and compared the results with published data from 10 other intrusive systems. Many of the fluid inclusions are paragenetically associated with melt inclusions, providing direct insights into the stage at which metals were transferred from the crystallizing magma into the exsolving aqueous fluids. In 10 out of 14 magma systems in which the physical and compositional properties of the magmatic fluid(s) could be determined, the exsolved aqueous fluid was a single phase of relatively low salinity (2-13 wt % NaCl equiv; avg 5 wt % NaCl equiv), confirming predictions based on indirect evidence and observations made in earlier studies. Furthermore, in magmas that crystallized at low pressure (< 1.3 kbars), the salinity of the magmatic fluid increased with increasing degree of crystallization, whereas in magmas that crystallized at higher pressure (>1.3 kbars) the opposite behavior occurred, as predicted by published numerical models of aqueous fluid-saturated magma crystallization. During the transition from magmatic to subsolidus conditions, both pressure and temperature within and adjacent to intrusions decreased, leading to widespread vapor-brine immiscibility. Due to the low salinity of the single-phase parent fluid the two-phase field generally was entered from the vapor side, resulting in condensation of subordinate amounts of brine from the low-density bulk fluid. If the transition from single- to two-phase aqueous fluid occurred in locally closed systems one can use the compositions of vapor and brine in subsolidus boiling assemblages to calculate the composition of the bulk fluid. This method was applied to those occurrences in which no single-phase parent fluid was found (i.e., where the earliest aqueous fluid found was already in the two-phase field). The metal content of the least fractionated low-salinity fluids at each location correlates positively with the type and amount of mineralization in the associated intrusions, with high Cu concentrations being observed in fluid related to porphyry Cu deposits, high Sn and W concentrations in fluids related to Sn-W mineralization and high Ce concentrations in fluids related to REE mineralization. The earliest fluids in barren intrusions are comparatively metal poor, except for two cases in which certain metal concentrations are as high as in mineralized systems. A significant portion of the geochemical signature of barren versus mineralized intrusions was thus inherited from earlier stages in the development of these magma systems. In the case of Mo, Sn, W, and Ce, the correlation between fluid composition and type and amount of mineralization is more distinct in high-temperature brines than in the least fractionated low-salinity fluids. This, together with other lines of evidence, suggests that brine condensates play a central role ill the formation of Sn, W, Mo, and REE deposits. In the case of porphyry Cu (-Au) systems it appears more likely that the greater proportion of metal precipitated from the vapor phase, although brines may have played a significant role as well. [ABSTRACT FROM AUTHOR]
- Published
- 2008
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24. Hydrothermal Evolution of the El Teniente Deposit, Chile: Porphyry Cu-Mo Ore Deposition from Low-Salinity Magmatic Fluids.
- Author
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Klemm, Leonhard M., Pettke, Thomas, Heinrich, Christoph A., and Campos, Eduardo
- Subjects
HYDROTHERMAL alteration ,PORPHYRY inclusions ,CATHODOLUMINESCENCE ,FLUID inclusions ,LASER ablation ,METASOMATISM ,COPPER mining - Abstract
The magmatic-hydrothermal evolution of the El Teniente porphyry Cu-Mo deposit in the Central Andes in Chile is reconstructed based on field relationships scanning electron microscopy cathodoluminescence petrography, and fluid inclusion analysis by microthermometry and laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS). Three major stages of Cu-Mo mineralization are observed. Following the barren hydrothermal stage 1 the stage 2 mineralization is characterized by quartz-anhydrite stockwork veins and breccias with chalcopyrite, bornite, and molybdenite. Both stages 1 and 2 are associated with pervasive potassic alteration. Quartz-anhydrite veins with chalcopyrite, bornite, and molybdenite associated with phyllic alteration represent stage 3 mineralization. Stage 4 mineralization, linked to the formation of the large Braden diatreme, is characterized by breccias and rare veins containing a lower temperature assemblage with tourmaline, sericite, and lesser tennantite, bornite, and chalcopyrite with late gypsum in local vugs. Ten fluid types are distinguished in this study based on petrographic and microthermometric criteria, such as phase proportions, daughter minerals, homogenization behavior, and salinity. The hydrothermal evolution across the stages of Cu deposition is characterized by the contraction of a vapor phase originating by phase separation during stage 2. Overall cooling of the system at pressures fluctuating around the two-phase fluid surface led to a transition from a two-phase fluid state dominated by vapor at ~410°C and 300 bars in stage 2, to a single-phase low-salinity fluid derived from cooling and contraction of magmatic vapor to a liquid, which dominates during stage 3 mineralization at <350°C and 200 bars. Copper mineralization mainly formed from the vapor phase and its low-salinity liquid derivatives, representing a large volume of fluid with an initially high Cu content (1.2 ± 0.4 wt % Cu). Copper sulfides precipitated upon cooling between 410° and 320°C, indicated by a drop of Cu/(Na + K + Mn + Fe) ratios of over four orders of magnitude through the evolution of the deposit from stage 2 to stage 4. The highest Mo concentrations occur in residual brines resulting from extreme boiling, as indicated by concurrent halite saturation. Recent geochronology (Cannell, 2005; Maksaev et al., 2004) suggests a relatively, long-lived magmatic- hydrothermal system at El Teniente. Our fluid chemical data show no evidence for major crystal fractionation in a large fluid-generating upper-crustal magma chamber, because Cs/(Na + K + Mn + Fe) is constant from pre-ore to all syn-ore fluids. However, the initiation of copper mineralization was associated with a 4- to 10-fold increase in the concentration of Cu, Mo, Li, and Fe in the inferred main ore-forming input fluid, compared with pre-ore fluids of intermediate salinity and otherwise very similar major and trace-element ratios. These data indicate that injection from depth of an exceptionally Cu, Mo, Li, and, probably, also S-rich volatile phase into an already actively evolving upper-crustal magmatic-hydrothermal system triggered the formation of this unusually large and rich copper deposit. [ABSTRACT FROM AUTHOR]
- Published
- 2007
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25. Magmatic Fluids in the Breccia-Hosted Epithermal Au-Ag Deposit of Roşlia Montanǎ, Rolnania.
- Author
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Wallier, Stefan, Rey, Roger, Kouzmanov, Kalin, Pettke, Thomas, Heinrich, Christoph A., Leary, Stephen, O'Connor, Gary, Tămaş, Călin G., Vennemann, Torsten, and Ullrich, Thomas
- Subjects
BRECCIA ,ROCKS ,ORE deposits ,MINES & mineral resources - Abstract
The breccia-hosted epithermal Au-Ag deposit of Roşa Montană is located 7 km northeast of Abrud, in the northern part of the South Apuseni Mountains, Romania. Estimated total reserves of 214.91 million metric tons (Mt) of ore at 1.46 g/t Au and 6.9 g/t Ag (10.1 Moz of An mid 47.6 Moz of Ag) make Roşia Montană one of the largest gold deposits in Europe. At this location, Miocene calc-alkaline magmatic and hydrothermal activity was associated with local extensional tectonics within a strike-slip regime related to the indentation of the Adriatic microplate into the European plate during the Carpathian orogenesis. The host rocks of the magmatic complex consist of pre-Mesozoic metamorphosed continental crest covered by Cretaceous turbiditic sediment (flysch), Magmatic activity at Roşia Montană and its surroundings occurred in several pulses and lasted about 7 m.y. Roşia Montană is a breccia-hosted epithermal system related to strong phreatomagmatic activity due to the shallow emplacement of the Montana dacite. The Montana dacite intruded Miocene volcaniclastic material (volcaniclastic breccias) and crops out at Cetate and Carnie Hills. Current mining is focused primarily on the Cetate open pit, which was mapped in detail, leading to the recognition of three distinct brecia bodies: the dacite breccia with a dominantly hydrothermal matrix, the gray polymict breccia with a greater proportion of sand-sized matrix support, and the black polymict breccia, which reached to the surface, contains carbonized tree trunks and has a dominantly barren elastic matrix. The hydrothermal alteration is pervasive. Adularia alteration with a phyllic overprint is ubiquitous; silicification and argillic alteration occur locally. Mineralization consists of quartz, adularia, carbonates (commonly Mn-rich), pyrite, Fe-poor sphalerite, galena, chalcopyrite, tetrahedrite, and native gold and occurs as disseminations, as well as in veins and fillings vugs within the Montana dacite and the different breccias. The age of mineralization (12.85 ± 0.07 Ma) was determined by 4th Ar
39 Ar dating on hydrothermal adularia crystals from vugs in the dacite breccia in the Cetate open pit. Microthermometric measurements of fluid inclusions in quartz phenocrysts from the Montana dacite revealed two fluid types that are absent from the hydrothermal breccia and must have leech trapped at depth prior to dacite dome emplacement: brine inclusions (32-5 wt % NaCl equiv, homogenizing at Th > 460°C) and intermediate density fluids (4.9-15.6 wt % NaCl equiv. Th between 345°--430°C). Secondary aqueous fluid inclusion assemblages in the phenocrysts have salinities of 0.2 to 2.2 wt percent NaCl equiv and Th , of 200° to 280°C, Fluid inclusion assemblages es in hydrothermal quartz from breccias and veins have salinities of 0.2 to 3.4 wt percent NaCl equiv and Th , from 200° to 270°C. The oxygen isotope composition of several zones ot an orerelated epithermal quartz crystal indicate a very constant δ18 O of 4.5 to 5.0 per mil for the mineralizing fluid, despite significant salinity and temperature variation over time. Following microthermometry, selected fluid inclusion assemblages were analyzed by laser ablation-inductively coupled-plasma mass spectrometry (LAICPMS). Despite systematic differences in salinity between phenocryst-hosted fluids trapped at depth and fluids from quartz in the epithermal breccias, all fluids have overlapping major and trace cation ratios, including identical Na/K/Rb/Sr/Cs/Ba. Consistent with the constant near-magmatic oxygen isotope composition of the hydrothermal fluids, these data strongly indicate a common magmatic component of these chemically conservative solutes in all fluids.… [ABSTRACT FROM AUTHOR]- Published
- 2006
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26. An Uncommon Category of Polyp Lesion in a Western Colon.
- Author
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Zimmer, Vincent and Heinrich, Christoph
- Published
- 2019
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27. Vapor Transport of Metals and the Formation of Magmatic-Hydrothermal Ore Deposits.
- Author
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Williams-Jones, Anthony E. and Heinrich, Christoph A.
- Subjects
ORE deposits ,HYDROTHERMAL deposits ,GEOTHERMAL resources ,METALS ,COPPER - Abstract
In most published hydrothermal ore deposit models, the main agent of metal transport is an aqueous liquid. However, there is increasing evidence from volcanic vapors, geothermal systems (continental and submarine), vapor-rich fluid inclusions, and experimental studies that the vapor phase may be an important and even dominant ore fluid in some hydrothermal systems. This paper reviews the evidence for the transport of metals by vapor (which we define as an aqueous fluid of any composition with a density lower than its critical density), clarifies some of the thermodynamic controls that may make such transport possible, and suggests a model for the formation of porphyry and epithermal deposits that involves precipitation of the ores from vapor or a vapor-derived fluid. Analyses of vapor (generally >90% water) released from volcanic fumaroles at temperatures from 500° to over 900°C and near-atmospheric pressure typically yield concentrations of ore metals in the parts per billion to parts per million range. These vapors also commonly deposit appreciable quantities of ore minerals as sublimates. Much higher metal concentrations (from ppm to wt %) are observed in vapor inclusions trapped at pressures of 20O to 1,000 bars in deeper veins at lower temperatures (400°-50°C). Moreover, concentrations of some metals, notably Cu and Au, are commonly higher in vapor inclusions than they are in inclusions of coexisting hypersaline liquid (brine). Experiments designed to determine the concentration of Cu, Sn, Ag, and Au in HCl-bearing water vapor at variable although relatively low pressures (up to 180 bars) partly explain this difference. These experiments show that metal solubility is orders of magnitude higher than predicted by volatility data for water-free systems, and furthermore that it increases sharply with increasing water fugacity and correlates positively with the fugacity of HCl. Thermodynamic analysis shows that metal solubility is greatly enhanced by reaction of the metal with HCl and by hydration, which results in the formation of species such as MeCl
m ⋅nH2 O. Nonetheless, the concentrations measured by these experiments are considerably lower than those measured in experiments involving aqueous liquids or determined for vapor fluid inclusions. A possible explanation for this and for the apparent preference of metals such as Cu and Au for the vapor over the coexisting brine in some natural settings is suggested by limited experimental studies of metal partitioning between vapor and brine. These studies show that, whereas Cu, Fe, and Zn all partition strongly into the liquid in chloride-bearing sulfur-free systems, Cu partitions preferentially into the vapor in the presence of significant concentrations of sulfur. We therefore infer that high concentrations of Cu and Au in vapor inclusions reflect the strong preference of sulfur for the vapor phase and the formation of sulfur-bearing metallic gas species. Phase stability relationships in the system NaCl-H2 O indicate how vapor transport of metals may occur in nature, by showing a range of possible vapor evolution paths for the conditions of porphyry-epithermal systems. At the world-class Bingham Canyon porphyry Cu-Au deposit, evidence from fluid inclusions supports a model in which a single-phase fluid of intermediate to vapor-like density ascends from a magma chamber. On cooling and decompression, this fluid condenses a small fraction of brine by intersecting the two-phase surface on the vapor side of the critical curve, without significantly changing the composition of the expanding vapor. Vapor and brine reach Cu-Fe sulfide saturation as both phases cool below 425°C. Vapor, which is the dominant fluid in terms of the total mass of H2 O, Cu, and probably even Cl, is interpreted to be the main agent in metal transport.… [ABSTRACT FROM AUTHOR]- Published
- 2005
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28. An evaluation of synthetic fluid inclusions for the purpose of trapping equilibrated, coexisting, immiscible fluid phases at magmatic conditions
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Simon, Adam C., Frank, Mark R., Pettke, Thomas, Candela, Philip A., Piccoli, Philip M., Heinrich, Christoph A., and Glascock, Michael
- Abstract
We report data that allow us to evaluate the method of trapping immiscible, saline aqueous fluids (i.e., vapor and brine in the NaCl-KCl-HCl-FeCl2-AuHCl2-H2O system) as synthetic fluid inclusions in pre-fractured quartz cores in order to quantify the concentrations of Au, Fe, K, and Na, among coexisting three-phase, immiscible fluids (i.e., haplogranite melt, brine, and vapor) at magmatic conditions. Coexisting vapor and brine were trapped experimentally at 800 °C and 100-110 MPa as synthetic fluid inclusions in both quartz microfractures and quenched silicate melt (i.e., glass), and also sampled indirectly using the recovered quenched aqueous fluid. Quartz-hosted and glass-hosted brine inclusions were analyzed by laser-ablation inductively-coupled-plasma mass spectrometry (LAICPMS) and instrumental neutron activation analysis (INAA), respectively. Quenched aqueous fluid from each experiment containing a quartz core was recovered and analyzed by atomic absorption spectrophotometry (AAS). The composition of aqueous fluids trapped as quartz-hosted inclusions, glass-hosted inclusions, and those recovered after quench yield consistent and precise data, at the 2σ uncertainty level, for the elements of interest. The overlapping Au, Fe, K, and Na concentrations in aqueous fluids trapped and analyzed via three entirely different instrumental techniques (i.e., LAICPMS, INAA, and AAS) suggest strongly that quartz microfractures heal on a slow enough time scale to permit entrapment of fully equilibrated aqueous fluids at our experimental PTX conditions. The data evince clearly that the chemical composition of fluids in quartz microfractures at the time of self-healing represents equilibrium conditions; hence, synthetic fluid inclusions in experiments with low thermal gradients across the charge provide a reasonable estimate of fluid composition at least at the experimental conditions examined in this study.
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- 2007
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29. Open pit pattern identifies sessile serrated adenoma/polyp on non-magnified acetic acid-enhanced colonoscopy
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Zimmer, Vincent, Heinrich, Christoph, and Lammert, Frank
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- 2020
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30. Potential utility of dedicated non-magnified endoscopy for identification of open pit pattern in sessile serrated adenoma/polyp
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Zimmer, Vincent, Heinrich, Christoph, and Lammert, Frank
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- 2020
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31. Multiphase Thermohaline Convection in the Earth’s Crust: I. A New Finite Element – Finite Volume Solution Technique Combined With a New Equation of State for NaCl–H2O
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Geiger, Sebastian, Driesner, Thomas, Heinrich, Christoph, and Matthäi, Stephan
- Abstract
We present a new finite element – finite volume (FEFV) method combined with a realistic equation of state for NaCl–H2O to model fluid convection driven by temperature and salinity gradients. This method can deal with the nonlinear variations in fluid properties, separation of a saline fluid into a high-density, high-salinity brine phase and low-density, low-salinity vapor phase well above the critical point of pure H2O, and geometrically complex geological structures. Similar to the well-known implicit pressure explicit saturation formulation, this approach decouples the governing equations. We formulate a fluid pressure equation that is solved using an implicit finite element method. We derive the fluid velocities from the updated pressure field and employ them in a higher-order, mass conserving finite volume formulation to solve hyperbolic parts of the conservation laws. The parabolic parts are solved by finite element methods. This FEFV method provides for geometric flexibility and numerical efficiency. The equation of state for NaCl–H2O is valid from 0 to 750°C, 0 to 4000 bar, and 0–100 wt.% NaCl. This allows the simulation of thermohaline convection in high-temperature and high-pressure environments, such as continental or oceanic hydrothermal systems where phase separation is common.We present a new finite element – finite volume (FEFV) method combined with a realistic equation of state for NaCl–H2O to model fluid convection driven by temperature and salinity gradients. This method can deal with the nonlinear variations in fluid properties, separation of a saline fluid into a high-density, high-salinity brine phase and low-density, low-salinity vapor phase well above the critical point of pure H2O, and geometrically complex geological structures. Similar to the well-known implicit pressure explicit saturation formulation, this approach decouples the governing equations. We formulate a fluid pressure equation that is solved using an implicit finite element method. We derive the fluid velocities from the updated pressure field and employ them in a higher-order, mass conserving finite volume formulation to solve hyperbolic parts of the conservation laws. The parabolic parts are solved by finite element methods. This FEFV method provides for geometric flexibility and numerical efficiency. The equation of state for NaCl–H2O is valid from 0 to 750°C, 0 to 4000 bar, and 0–100 wt.% NaCl. This allows the simulation of thermohaline convection in high-temperature and high-pressure environments, such as continental or oceanic hydrothermal systems where phase separation is common.
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- 2006
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32. Multiphase Thermohaline Convection in the Earth’s Crust: II. Benchmarking and Application of a Finite Element – Finite Volume Solution Technique with a NaCl–H2O Equation of State
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Geiger, Sebastian, Driesner, Thomas, Heinrich, Christoph, and Matthäi, Stephan
- Abstract
We present the benchmarking of a new finite element – finite volume (FEFV) solution technique capable of modeling transient multiphase thermohaline convection for geological realistic p-T-Xconditions. The algorithm embeds a new and accurate equation of state for the NaCl–H2O system. Benchmarks are carried out to compare the numerical results for the various component-processes of multiphase thermohaline convection. They include simulations of (i) convection driven by temperature and/or concentration gradients in a single-phase fluid (i.e., the Elder problem, thermal convection at different Rayleigh numbers, and a free thermohaline convection example), (ii) multiphase flow (i.e., the Buckley–Leverett problem), and (iii) energy transport in a pure H2O fluid at liquid, vapor, supercritical, and two-phase conditions (i.e., comparison to the U.S. Geological Survey Code HYDROTHERM). The results produced with the new FEFV technique are in good agreement with the reference solutions. We further present the application of the FEFV technique to the simulation of thermohaline convection of a 400°C hot and 10 wt.% saline fluid rising from 4 km depth. During the buoyant rise, the fluid boils and separates into a high-density, high-salinity liquid phase and a low-density, low-salinity vapor phase.We present the benchmarking of a new finite element – finite volume (FEFV) solution technique capable of modeling transient multiphase thermohaline convection for geological realistic p-T-Xconditions. The algorithm embeds a new and accurate equation of state for the NaCl–H2O system. Benchmarks are carried out to compare the numerical results for the various component-processes of multiphase thermohaline convection. They include simulations of (i) convection driven by temperature and/or concentration gradients in a single-phase fluid (i.e., the Elder problem, thermal convection at different Rayleigh numbers, and a free thermohaline convection example), (ii) multiphase flow (i.e., the Buckley–Leverett problem), and (iii) energy transport in a pure H2O fluid at liquid, vapor, supercritical, and two-phase conditions (i.e., comparison to the U.S. Geological Survey Code HYDROTHERM). The results produced with the new FEFV technique are in good agreement with the reference solutions. We further present the application of the FEFV technique to the simulation of thermohaline convection of a 400°C hot and 10 wt.% saline fluid rising from 4 km depth. During the buoyant rise, the fluid boils and separates into a high-density, high-salinity liquid phase and a low-density, low-salinity vapor phase.
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- 2006
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33. Magma evolution and the formation of porphyry Cu–Au ore fluids: evidence from silicate and sulfide melt inclusions
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Halter, Werner, Heinrich, Christoph, and Pettke, Thomas
- Abstract
Silicate and sulfide melt inclusions from the andesitic Farallón Negro Volcanic Complex in NW Argentina were analyzed by laser ablation ICPMS to track the behavior of Cu and Au during magma evolution, and to identify the processes in the source of fluids responsible for porphyry-Cu-Au mineralization at the 600 Mt Bajo de la Alumbrera deposit. The combination of silicate and sulfide melt inclusion data with previously published geological and geochemical information indicates that the source of ore metals and water was a mantle-derived mafic magma that contained approximately 6 wt.% H2O and 200 ppm Cu. This magma and a rhyodacitic magma mixed in an upper-crustal magma chamber, feeding the volcanic systems and associated subvolcanic intrusions over 2.6 million years. Generation of the ore fluid from this magma occurred towards the end of this protracted evolution and probably involved six important steps: (1) Generation of a sulfide melt upon magma mixing in some parts of the magma chamber. (2) Partitioning of Cu and Au into the sulfide melt (enrichment factor of 10,000 for Cu) leading to Cu and Au concentrations of several wt.% or ppm, respectively. (3) A change in the tectonic regime from local extension to compression at the end of protracted volcanism. (4) Intrusion of a dacitic magma stock from the upper part of the layered magma chamber. (5) Volatile exsolution and resorption of the sulfide melt from the lower and more mafic parts of the magma chamber, generating a fluid with a Cu/Au ratio equal to that of the precursor sulfide. (6) Focused fluid transport and precipitation of the two metals in the porphyry, yielding an ore body containing Au and Cu in the proportions dictated by the magmatic fluid source. The Cu/S ratio in the sulfide melt inclusions requires that approximately 4,000 ppm sulfur is extracted from the andesitic magma upon mixing. This exceeds the solubility of sulfide or sulfate in either of the silicate melts and implies an additional source for S. The extra sulfur could be added in the form of anhydrite phenocrysts present in the rhyodacitic magma. It appears, thus, that unusually sulfur-rich, not Cu-rich magmas are the key to the formation of porphyry-type ore deposits. Our observations imply that dacitic intrusions hosting the porphyry–Cu–Au mineralization are not representative of the magma from which the ore-fluid exsolved. The source of the ore fluid is the underlying more mafic magma, and unaltered andesitic dikes emplaced immediately after ore formation are more likely to represent the magma from which the fluids were generated. At Alumbrera, these andesitic dikes carry relicts of the sulfide melt as inclusions in amphibole. Sulfide inclusions in similar dykes of other, less explored magmatic complexes may be used to predict the Au/Cu ratio of potential ore-forming fluids and the expected metal ratio in any undiscovered porphyry deposit.Silicate and sulfide melt inclusions from the andesitic Farallón Negro Volcanic Complex in NW Argentina were analyzed by laser ablation ICPMS to track the behavior of Cu and Au during magma evolution, and to identify the processes in the source of fluids responsible for porphyry-Cu-Au mineralization at the 600 Mt Bajo de la Alumbrera deposit. The combination of silicate and sulfide melt inclusion data with previously published geological and geochemical information indicates that the source of ore metals and water was a mantle-derived mafic magma that contained approximately 6 wt.% H2O and 200 ppm Cu. This magma and a rhyodacitic magma mixed in an upper-crustal magma chamber, feeding the volcanic systems and associated subvolcanic intrusions over 2.6 million years. Generation of the ore fluid from this magma occurred towards the end of this protracted evolution and probably involved six important steps: (1) Generation of a sulfide melt upon magma mixing in some parts of the magma chamber. (2) Partitioning of Cu and Au into the sulfide melt (enrichment factor of 10,000 for Cu) leading to Cu and Au concentrations of several wt.% or ppm, respectively. (3) A change in the tectonic regime from local extension to compression at the end of protracted volcanism. (4) Intrusion of a dacitic magma stock from the upper part of the layered magma chamber. (5) Volatile exsolution and resorption of the sulfide melt from the lower and more mafic parts of the magma chamber, generating a fluid with a Cu/Au ratio equal to that of the precursor sulfide. (6) Focused fluid transport and precipitation of the two metals in the porphyry, yielding an ore body containing Au and Cu in the proportions dictated by the magmatic fluid source. The Cu/S ratio in the sulfide melt inclusions requires that approximately 4,000 ppm sulfur is extracted from the andesitic magma upon mixing. This exceeds the solubility of sulfide or sulfate in either of the silicate melts and implies an additional source for S. The extra sulfur could be added in the form of anhydrite phenocrysts present in the rhyodacitic magma. It appears, thus, that unusually sulfur-rich, not Cu-rich magmas are the key to the formation of porphyry-type ore deposits. Our observations imply that dacitic intrusions hosting the porphyry–Cu–Au mineralization are not representative of the magma from which the ore-fluid exsolved. The source of the ore fluid is the underlying more mafic magma, and unaltered andesitic dikes emplaced immediately after ore formation are more likely to represent the magma from which the fluids were generated. At Alumbrera, these andesitic dikes carry relicts of the sulfide melt as inclusions in amphibole. Sulfide inclusions in similar dykes of other, less explored magmatic complexes may be used to predict the Au/Cu ratio of potential ore-forming fluids and the expected metal ratio in any undiscovered porphyry deposit.
- Published
- 2005
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34. The physical and chemical evolution of low-salinity magmatic fluids at the porphyry to epithermal transition: a thermodynamic study
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Heinrich, Christoph
- Abstract
Fluid-phase relationships and thermodynamic reaction modelling based on published mineral solubility data are used to re-assess the Cu–Au-mineralising fluid processes related to calc-alkaline magmatism. Fluid inclusion microanalyses of porphyry ore samples have shown that vapour-like fluids of low to intermediate salinity and density (~2–10 wt% NaCl eq.; ~0.1–0.3 g cm−3) can carry percentage-level concentrations of copper and several ppm gold at high temperature and pressure. In epithermal deposits, aqueous fluids of similar low to intermediate salinity but liquid-like density are ubiquitous and commonly show a magmatic isotope signature. This paper explores the physical evolution of low-salinity to medium-salinity magmatic fluids of variable density, en route from their magmatic source through the porphyry regime to the near-surface epithermal environment, and investigates the chemical conditions required for effective transport of gold and other components from the magmatic to the epithermal domain. Multicomponent reaction modelling guided by observations of alteration zonation and vein overprinting relationships predicts that epithermal gold deposits are formed most efficiently by a specific succession of processes during the evolution of a gradually cooling magmatic–hydrothermal system. (1) The low-salinity to medium-salinity fluid, after separating from the magma and possibly condensing out some hypersaline liquid in the high-temperature porphyry environment, must physically separate from the denser and more viscous liquid, and then cool within the single-phase fluid stability field. By cooling under adequate confining pressure, such a vapour will evolve above the critical curve and contract, without any heterogeneous phase change, to an aqueous liquid of the same salinity. (2) High concentrations of gold, transported as stable Au bisulphide complexes supporting >1 ppm Au even at 200°C, can be maintained throughout cooling, provided that the fluid initially carries an excess of H2S over Cu+Fe on a molal scale. This condition is favoured by an initially high sulphide content in a particularly low-salinity magmatic fluid, or by preferential partitioning of sulphur into a low-salinity vapour and partial removal of Fe into a hypersaline liquid at high temperature. (3) Acid neutralisation further optimises gold transport by maximising the concentration of the HS−ligand. This may occur by feldspar destructive alteration along pyrite±chalcopyrite±sulphate veins, in the transition zone between the porphyry and epithermal environments. An alternative acid/base control is the dissolution of calcite in sediments, which may enable long-distance gold transport to Carlin-type deposits, because of the positive feedback between acid neutralisation and permeability generation. The three physical and chemical transport requirements for high-grade epithermal gold mineralisation are suggested to be the common link of epithermal gold deposits to underlying magmatic–hydrothermal systems, including porphyry-Cu–Au deposits. Both mineralisation types are the result of gradual retraction of isotherms around cooling hydrous plutons in similar tectonic and hydrologic environments. As magmatic fluid is generated at increasing depths below the surface the importance of vapour contraction increases, leading to the typical overprinting of potassic, phyllic and advanced argillic alteration and their related ore styles.Fluid-phase relationships and thermodynamic reaction modelling based on published mineral solubility data are used to re-assess the Cu–Au-mineralising fluid processes related to calc-alkaline magmatism. Fluid inclusion microanalyses of porphyry ore samples have shown that vapour-like fluids of low to intermediate salinity and density (~2–10 wt% NaCl eq.; ~0.1–0.3 g cm−3) can carry percentage-level concentrations of copper and several ppm gold at high temperature and pressure. In epithermal deposits, aqueous fluids of similar low to intermediate salinity but liquid-like density are ubiquitous and commonly show a magmatic isotope signature. This paper explores the physical evolution of low-salinity to medium-salinity magmatic fluids of variable density, en route from their magmatic source through the porphyry regime to the near-surface epithermal environment, and investigates the chemical conditions required for effective transport of gold and other components from the magmatic to the epithermal domain. Multicomponent reaction modelling guided by observations of alteration zonation and vein overprinting relationships predicts that epithermal gold deposits are formed most efficiently by a specific succession of processes during the evolution of a gradually cooling magmatic–hydrothermal system. (1) The low-salinity to medium-salinity fluid, after separating from the magma and possibly condensing out some hypersaline liquid in the high-temperature porphyry environment, must physically separate from the denser and more viscous liquid, and then cool within the single-phase fluid stability field. By cooling under adequate confining pressure, such a vapour will evolve above the critical curve and contract, without any heterogeneous phase change, to an aqueous liquid of the same salinity. (2) High concentrations of gold, transported as stable Au bisulphide complexes supporting >1 ppm Au even at 200°C, can be maintained throughout cooling, provided that the fluid initially carries an excess of H2S over Cu+Fe on a molal scale. This condition is favoured by an initially high sulphide content in a particularly low-salinity magmatic fluid, or by preferential partitioning of sulphur into a low-salinity vapour and partial removal of Fe into a hypersaline liquid at high temperature. (3) Acid neutralisation further optimises gold transport by maximising the concentration of the HS−ligand. This may occur by feldspar destructive alteration along pyrite±chalcopyrite±sulphate veins, in the transition zone between the porphyry and epithermal environments. An alternative acid/base control is the dissolution of calcite in sediments, which may enable long-distance gold transport to Carlin-type deposits, because of the positive feedback between acid neutralisation and permeability generation. The three physical and chemical transport requirements for high-grade epithermal gold mineralisation are suggested to be the common link of epithermal gold deposits to underlying magmatic–hydrothermal systems, including porphyry-Cu–Au deposits. Both mineralisation types are the result of gradual retraction of isotherms around cooling hydrous plutons in similar tectonic and hydrologic environments. As magmatic fluid is generated at increasing depths below the surface the importance of vapour contraction increases, leading to the typical overprinting of potassic, phyllic and advanced argillic alteration and their related ore styles.
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- 2005
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35. Experimental determination of Au solubility in rhyolite melt and magnetite: Constraints on magmatic Au budgets
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Simon, Adam C., Pettke, Thomas, Candela, Philip A., Piccoli, Philip M., and Heinrich, Christoph A.
- Abstract
The solubility of Au metal in rhyolite melt and coexisting magnetite has been determined at 800 °C, 140 MPa, and ƒO2≈ NNO in a Au-metal saturated, sulfur-free, vapor-brine-silicate melt system. Whole crystals of magnetite suspended within quenched rhyolite glass were analyzed by LA-ICPMS. These data yield a solubility of Au in magnetite on the order of 2 mg/g. The solubility of Au metal in rhyolite melt hosting the magnetite crystals is on the order of 500 μg/g. These data indicate a partition coefficient for Au between magnetite and melt, DAuMt/melt≈ 4. Using reasonable estimates of the mass fraction of magnetite that crystallizes in crustal magmatic systems, we modeled the proportion of Au sequestered by magnetite during fractional crystallization. We considered fractionation in two steps: the idealized derivation of a rhyolite by fractionation of basalt at depth, and the closedsystem crystallization of the rhyolite in a magma chamber below the site of ore deposition. Magnetite sequesters 14-54% Au from basaltic parent melt that produces a rhyolite melt via crystal fractionation, at modal abundances of 1-5%. Less then 4% Au is sequestered from a crystallizing rhyolite melt because of low modal abundances of magnetite (<~2%). Our experimental and model results suggest that early crystallization of magnetite can play a mitigating role in the ability of a calc-alkaline magmatic system to yield a Au-rich ore fluid.
- Published
- 2003
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36. Experimental determination of Au solubility in rhyolite melt and magnetite: Constraints on magmatic Au budgets
- Author
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Simon, Adam C., Pettke, Thomas, Candela, Philip A., Piccoli, Philip M., and Heinrich, Christoph A.
- Abstract
The solubility of Au metal in rhyolite melt and coexisting magnetite has been determined at 800 °C, 140 MPa, and ƒO2≈ NNO in a Au-metal saturated, sulfur-free, vapor-brine-silicate melt system. Whole crystals of magnetite suspended within quenched rhyolite glass were analyzed by LA-ICPMS. These data yield a solubility of Au in magnetite on the order of 2 mg/g. The solubility of Au metal in rhyolite melt hosting the magnetite crystals is on the order of 500 μg/g. These data indicate a partition coefficient for Au between magnetite and melt, DAuMt/melt≈ 4. Using reasonable estimates of the mass fraction of magnetite that crystallizes in crustal magmatic systems, we modeled the proportion of Au sequestered by magnetite during fractional crystallization. We considered fractionation in two steps: the idealized derivation of a rhyolite by fractionation of basalt at depth, and the closedsystem crystallization of the rhyolite in a magma chamber below the site of ore deposition. Magnetite sequesters 14-54% Au from basaltic parent melt that produces a rhyolite melt via crystal fractionation, at modal abundances of 1-5%. Less then 4% Au is sequestered from a crystallizing rhyolite melt because of low modal abundances of magnetite (<~2%). Our experimental and model results suggest that early crystallization of magnetite can play a mitigating role in the ability of a calc-alkaline magmatic system to yield a Au-rich ore fluid.
- Published
- 2003
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37. Cu – Au – Pb – Zn – Ag metallogeny of the Alpine – Balkan – Carpathian – Dinaride geodynamic province
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Heinrich, Christoph and Neubauer, Franz
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- 2002
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38. A fluid inclusion reconnaissance study of the Huanuni tin deposit (Bolivia), using LA-ICP-MS micro-analysis
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Müller, Barbara, Frischknecht, Rolf, Seward, Terry, Heinrich, Christoph, and Camargo Gallegos, Willy
- Abstract
Fluid inclusions have been studied in selected quartz-cassiterite veins of the Huanuni tin deposit, Bolivia. Fluid inclusion assemblages were found in quartz that bracket at least one stage of cassiterite deposition, and some were found in quartz crystallised during a later sulphide mineralisation stage. All fluid inclusions consisted of two phases only (liquid+vapour), which homogenised to a liquid upon heating and were classified to be of pseudosecondary or secondary in origin. Salinities in fluid inclusions related to the cassiterite deposition were up to 22 wt% NaCl equiv., and homogenisation temperatures of low and high salinity inclusions overlap in the range of 370 to 390 °C. Laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to determine element concentrations in selected fluid inclusions. The high salinity fluid inclusions show elevated contents of Li, B, Na, K, Mn, Fe, Zn, Ge, As, Rb, Sn, Sb, Cs, La and Pb compared with the lower salinity samples (wt% NaCl equiv. lower than 6%). High concentrations of incompatible lithophile elements including Li, B and Cs are characteristic for fluids derived from highly fractionated granitic systems. Fe, Zn, Pb, and Ge are the most important heavy metals transported with tin in the aqueous fluid. Sn, Fe, Zn, Pb are probably transported as chloride complexes, and the initial fluid-chemical data for successive fluid-inclusion generations indicates that SnO2precipitation occurred by injection of a hot saline magmatic fluid into heated low-salinity waters of possible meteoric origin.
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- 2001
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39. Quadrupole mass spectrometry and optical emission spectroscopy: detection capabilities and representative sampling of short transient signals from laser-ablation
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Pettke, Thomas, Heinrich, Christoph A., Ciocan, Adeline C., and Günther, Detlef
- Abstract
Laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has become a powerful tool in geochemistry, but for some important elements it is prone to interferences. The detection capabilities of optical emission spectroscopy (OES) might be superior to quadrupole mass spectrometry (QMS) in certain cases. Experiments for Na, Mg, Si, K, Ca and Fe showed limits of detection (LOD) with QMS of 0.9, 0.3, 700, 7.1, 180, 22 µg g−1, respectively, obtained for continuous ablation of the Glass standard SRM 612 from NIST at a rate of ≈5.5 ng s−1 in a 40 µm ablation pit. A modern OES system linked to the same LA setup showed poorer LOD of one to two orders of magnitude for these elements except for Ca. This is mainly due to the better sensitivities of QMS resulting from higher signal-to-background ratios. Yet, from the recording of short transient signals by QMS generated by the ablation of ~500 pg of material using a single laser shot, 2040 times higher LOD have to be accepted relative to continuous ablation. For menus exceeding ≈10 isotopes with dwell times above 10 ms, the scan speed of the sequential QMS filter relative to the signal duration may be insufficient for representative sampling of short (<≈3 s) transient signals, leading to less reproducible results. Simultaneous signal recording by OES has the potential to eliminate this problem, if the LOD of OES are low enough to detect such signals. Unfortunately, the duty cycle of the OES system degraded significantly with increasing number of spectral lines, due to the slow data readout, from 35% (10 elements) to 12% measurement efficiency (18 elements). The example of natural fluid inclusions shows that, for multi-element menus and short transient signals, LA-ICP-QMS is currently the best method, until the sensitivity, dynamic range of the CCD and data readout speed of OES instruments are improved.
- Published
- 2000
40. Epidermoid metaplasia of the esophagus
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Zimmer, Vincent and Heinrich, Christoph
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- 2021
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41. Enhanced sensitivity in laser ablation-ICP mass spectrometry using helium-argon mixtures as aerosol carrier
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Günther, Detlef and Heinrich, Christoph A.
- Abstract
Laser ablation-ICP-MS is a sensitive and accurate technique for major to trace multi-element analysis at high spatial resolution on the scale of 10 μm. A wide variety of samples can be studied quantitatively, including minerals and their solid, liquid or melt inclusions as required for geochemical studies. As the desired spatial resolution increases, however, detection limits become severely constrained by the total amount of sample material reaching the ICP. Detection limits are therefore determined by the ablation rate and by the efficiency of removal of ablated aerosol particles from the ablation spot and their transport into the plasma. Properties of the carrier gas are known to affect the ablation process and the efficiency of particle transportation. This study explores the effects of different ablation-cell configurations and the use of helium, dry argon and argon moistened with water for the transport of aerosols into an ICP-MS, using a prototype 193 nm ArF excimer laser. Deposition of visible particles deposited around the ablation pit is significantly reduced when helium is used instead of argon. A moderate flux of helium through the chamber, mixed with moistened argon immediately downstream from the ablation chamber, leads to at least a 2-3-fold increase in the signal intensities across the entire mass range when compared with argon gas only. Background intensities above mass 85 are significantly reduced, but polyatomic interferences in the low mass region increase by an order of magnitude, owing to oxide formation caused by the water load. A high flux of helium, mixed just behind the ablation cell with dry argon, yields a 2-3-fold sensitivity enhancement, in addition to greatly reduced background intensity across the entire mass range. This results in one order of magnitude improvement in detection limits for most elements. These modifications permit the routine determination of minor concentrations of chlorine in microscopic fluid inclusions or the analysis of minerals, such as trace element concentrations in quartz (e.g., Na and Li down to 500 ng g−1, using a 40 μ ablation pit). Furthermore, this improved sensitivity has recently yielded the first quantitative determination of gold concentrations (~0.1 μg g−1) and full rare-earth element patterns in single 25 μm fluid inclusions.
- Published
- 1999
42. Comparison of the ablation behaviour of 266 nm Nd:YAG and 193 nm ArF excimer lasers for LA-ICP-MS analysis
- Author
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Günther, Detlef and Heinrich, Christoph A.
- Abstract
The ablation characteristics of a 266 nm Nd:YAG laser and a 193 nm excimer laser were compared by successive experiments by inductively coupled plasma mass spectrometry (ICP-MS), using the same ablation cell without changing the carrier-gas flows within comparative experiments. Both laser-optical systems have a fairly flat-topped lateral energy distribution yielding pan-shaped ablation pits on the sample. Comparative experiments with the two optical systems were carried out with argon and with helium+argon as carrier gases. For both lasers and both gas set-ups, signals of 40 s duration were recorded with a pulse rate of 10 Hz, with similar fluence adjusted to give comparable rates of material ablation. ICP-MS signal intensities were normalised to the total ablated volume, to compare the effects of lasers and gases on transport efficiency, ionisation efficiency and response and time-dependent element fractionation. The accuracy of trace element results was tested using two materials that allow stable ablation with both lasers but have significantly different matrix compositions (SRM 612 silicate glass from NIST and AGV-1 geological reference material in lithium tetraborate fusion). The time-averaged rate of material ablation is similar for both lasers and independent of the carrier gas in the sample chamber, but decays more rapidly with the 266 nm system. In argon, the signal unit response per volume of ablated material is similar with both lasers. In helium, the signal intensity with the 266 nm laser is enhanced slightly (maximum two-fold) compared with argon, but with the 193 nm system a consistent 2-3-fold signal enhancement is achieved. The use of helium reduces the amount of visible (>1 μm size) particle deposition in the ablation cell, irrespective of laser wavelength, and tests with successive ablations of chemically contrasting samples indicate memory effects with the 266 nm system that are absent in the same experiment with the 193 nm system. The limits of detection for both lasers were further improved by the use of He owing to the decrease in background intensities. Time-dependent element fractionation during a 40 s single-spot ablation is almost eliminated with the 193 nm system (<10%), but with the 266 nm laser inter-element intensity ratios comparing the first and the second halves of the ablation period varied by up to 60% for some elements. Results for the cross-calibration between silicate (SRM 612) and borate glasses (AGV-1) obtained with both lasers indicate that the fractionation with the 266 nm system is similar for these two matrices, but this is not generally true for silicate minerals. The 193 nm system gives slightly better reproducibility between multiple analyses of one sample compared with the 266 nm system, yielding 2-5% RSDs for major and minor elements and 7-15% for concentrations below 10 ppm.
- Published
- 1999
43. Capabilities of an Argon Fluoride 193 nm Excimer Laser for Laser Ablation Inductively Coupled Plasma Mass Spectometry Microanalysis of Geological Materials
- Author
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GÜNTHER, DETLEF, FRISCHKNECHT, ROLF, HEINRICH, CHRISTOPH A., and KAHLERT, HANS-J.
- Abstract
Recent developments in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) have demonstrated its potential forin situ microanalysis for major, minor and trace elements in solids, such as minerals. With the low backgrounds and high sensitivity of new ICP-MS instruments, limits of detection of 1–10 ng g-1 in a 40 m ablation pit for many elements can be reached. Fractionation effects due to different ablation rates of various elements have prevented quantification without matrix-matched standards with 1064 nm Nd:YAG lasers. These effects have been reduced but not eliminated using shorter UV wavelengths (e.g. a quadrupled Nd:YAG 266 nm). Excimer lasers with wavelengths below 200 nm are expected to reduce fractionation effects further, but they present a serious challenge to the design of optical systems, especially if high-resolution UV ablation needs to be combined with high quality visual observation, which is essential for the study of complex materials, such as geological samples. An LA system was developed using an homogenized UV laser beam (193 nm, Argon Fluoride excimer) with a common UV–visual objective on a modified petrographic microscope with reflected and transmitted light illumination, in combination with a Perkin-Elmer Elan 6000 ICP-MS instrument. The optical system allows imaging of both visible and UV laser light onto the sample surface at the same time. Laser operating parameters and their influence on the ablation process were investigated using NIST SRM 612/610. Fractionation effects due to differential ablation of various elements as a function of time can be reduced to interelement correlation coefficients of r=0.9 or better and have become insignificant within the precision of quadrupole ICP-MS using this new optical design. Energy densities and repetition rates need to be kept within limited ranges for accurate and reproducible determinations of trace elements such as Zn, U and Pb, which have previously presented strong fractionation problems. LA-ICP-MS determinations on natural hornblende, augite, and garnet, calibrated against NIST SRM 612 using any major element as an internal standard, agree well with independent literature data. These experiments with the Argon Fluoride 193 nm excimer system demonstrate a greatly reduced matrix dependence of the ablation process, which facilitates in situ analysis of unknown samples.
- Published
- 1997
- Full Text
- View/download PDF
44. Kyanite-eclogite to amphibolite fades evolution of hydrous mafic and pelitic rocks, Adula nappe, Central Alps
- Author
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Heinrich, Christoph A.
- Abstract
In the southern Adula nappe (Central Alps), two stages of regional metamorphism have affected mafic and pelitic rocks. Earlier eclogite facies with a regional zonation from glaucophane eclogites to kyanite-hornblende eclogites was followed by a Tertiary overprint which varied from greenschist to high-grade amphibolite facies. Despite a common metamorphic history, contrasting equilibration conditions are often recorded by high-pressure mafic eclogite and adjacent predominantly lower-pressure pelite assemblages. This pressure contrast may be explained by different overprinting rates of the two bulk compositions during unloading. The rates are controlled by a mechanism in which dehydrating metapelites provide the H
2 O required for simultaneous overprinting of enclosed mafic eclogites by hydration.- Published
- 1982
- Full Text
- View/download PDF
45. Quantitative analysis of major, minor and trace elements in fluid inclusions using laser ablationinductively coupled plasmamass spectrometry
- Author
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Günther, Detlef, Audétat, Andreas, Frischknecht, Rolf, and Heinrich, Christoph A.
- Abstract
Microscopic fluid inclusions in minerals are the main source of information about the chemical composition of fluids associated with large-scale material transport in the Earth's interior. Hydrothermal transport processes are responsible for the natural enrichment of metal resources in many ore deposits. For the multi-element analysis of the microscopic fluid inclusions (typically 550 μm in diameter), LA-ICP-MS has become one of the most promising techniques owing to the recent progress in laser optics design and the development of high-sensitivity ICP mass spectrometers. The quantitative analyses of 19 major, minor and trace elements covering a concentration range of five orders of magnitude were carried out on 39 single natural fluid inclusions, together with a number of experiments to optimise controlled ablation and to test the calibration procedure. A modified commercial ICP-MS instrument was used together with a prototype ablation system based on a 193 nm excimer laser. In a stepwise opening procedure for complex polyphase inclusions, a small hole (4 μm pit) was first drilled for the partial release of liquid and vapor, followed by complete drilling out using a pit covering the entire inclusion. Controlled ablation improves the reproducibility of element ratios to less than 20% for most major, minor and trace elements measured in an assemblage of cogenetic inclusions (including elements that are initially present as solid precipitates within the inclusion), provided that the entire transient ICP-MS signal is integrated. Element ratios were calculated from integrated intensity ratios using an external standard, either a NIST SRM glass or an aqueous standard solution ablated directly through a plastic film. Absolute concentrations were calculated from the element ratiosviaan internal standard element, whose concentration was determined prior to ablation. Microthermometric measurements of phase transitions were used to determine total salinity from known phase diagrams, by measuring either the depression of ice-melting temperature, or the temperature of dissolution of NaCl crystals. Salinity can be related to the concentration of Na (or in some cases Cl), which serves as the internal standard element for the quantification of trace element concentrations. Calculated limits of detection are in the ng g−1to μg g−1region, depending on the volume of the inclusions. The accuracy of the overall analysis, including internal and external calibration, is typically between 5 and 20%, as demonstrated on alkali elements in synthetic fluid inclusions of known composition.
- Published
- 1998
46. BESTIARY 345f.
- Author
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MATTHES, HEINRICH CHRISTOPH
- Published
- 1956
- Full Text
- View/download PDF
47. BEOWULFSTUDIEN
- Author
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MATTHES, HEINRICH CHRISTOPH
- Published
- 1953
- Full Text
- View/download PDF
48. ZUM QUELLENPROBLEM DER PALLADIS TAMIA.
- Author
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MATTHES, HEINRICH CHRISTOPH
- Published
- 1941
- Full Text
- View/download PDF
49. FRANCIS MERES UND ERASMUS VON ROTTERDAM.
- Author
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MATTHES, HEINRICH CHRISTOPH
- Published
- 1939
- Full Text
- View/download PDF
50. “THUS CONSCIENCE DOES MAKE COWARDS OF US ALL” (HAMLET III, 1).
- Author
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MATTHES, HEINRICH CHRISTOPH
- Published
- 1936
- Full Text
- View/download PDF
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