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The Lagoa Seca is a gold deposit located in the Mesoarchean Andorinhas greenstone belt in the eastern portion of the Amazonian Craton, northern Brazil. It consists of clastic metasedimentary (metagreywacke and metasiltstone) and metavolcanic (metadacite and metaultramafic) rocks. It was operated by Troy Resources Ltd. as an open pit mine from 2008 to 2014, and it produced approximately 150 koz of gold. The hydrothermal alteration halo is directly associated with the internal zonation of the Lagoa Seca shear zone, and it includes i) a distal zone composed of chlorite-epidote-carbonate, ii) an intermediate zone with minerals from the distal alteration plus moderate silicification, iii) a proximal zone composed of biotite-magnetite (carbonate-amphibole-sulfide-gold), and iv) a gold-rich ore zone that has been affected by sulfidation and potassification. Whole-rock geochemistry and mineral chemistry studies on the hydrothermally altered host rocks show that Al2O5 and Na2O increase with silica content, while Fe2O3, MnO, MgO, CaO and the LOI decrease. The minor and trace elements are characterized by very good correlations among Zr, Nb, Ti and LREEs. The REE patterns of hydrothermal rocks show high to moderate fractionation with the La/Lu(cn) of the LREEs and HREEs towards the center of the hydrothermal conduit and are accompanied by a weak negative europium anomaly. The trace-element geochemistry is consistent with that of the subduction related calc-alkaline magmas in continental arcs. In addition, the tectonic discriminant diagrams show a calc-alkaline affinity and classify the host rocks as being derived from subduction processes. The hydrothermal chlorites are classified as brungsvite; mica is phlogopite and amphiboles range from actinolite, tremolite to Mg-hornblende. The main sulfide is pyrite, which is accompanied by minor amounts of chalcopyrite, galena, pyrrhotite and traces of millerite. The EPMA analysis of the pyrite shows that As, Co and Cu increase towards the center of the hydrothermal zone, as well as Zn, Ni and Au decrease in the opposite direction. Gold is present predominantly as inclusions in pyrite/chalcopyrite, with a high Au content. A chlorite geothermometer indicates that the temperatures ranged from 275 °C to 351 °C in the hydrothermal zones. The oxygen and carbon stable isotope data from the calcite of the ore zone return values of 8.12‰ SMOW and −6.36‰ PDB, respectively, which are compatible with a metamorphic fluid source. However, sulfur stable isotope displays 1.92‰ V-CDT, which may suggest a magmatic sulfur source. The composition of the fine-grained pyrite indicates that the hydrothermal fluid presents a deep crustal source of metamorphic origin, and it is accompanied by a mixed magmatic contribution, which was probably generated during the dominant TTG evolution of the area. The whole-rock Sm-Nd isotopic analyses produced a TDM of 2.92–3.04 Ga and an eNd (2.9) of +0.39 to +1.67 for metaultramafic rocks, a TDM of 2.78–2.92 Ga and an eNd of (2.9) +1.61 to +2.92 for metasedimentary rocks, and a TDM of 2.79–2.83 Ga and an ƐNd of (2.9) +2.83 to +3.02 for metadacite rocks. An Sm–Nd isochron age of 2867 ± 40 Ma indicates a Mesoarchean age for the host rocks.

The color of quartz and other minerals can be either caused by defects in the crystal structure or by finely dispersed inclusions of other minerals within the crystals. In order to investigate the mineral chemistry and genesis of the famous prase (green quartz) and amethyst association from Serifos Island, Greece, we used electron microprobe analyses and oxygen isotope measurements of quartz. We show that the color of these green quartz crystals is caused by small and acicular amphibole inclusions. Our data also shows that there are two generations of amphibole inclusions within the green quartz crystals, which indicate that the fluid, from which both amphiboles and quartz have crystallized, must have had a change in its chemical composition during the crystallization process. The electron microprobe data also suggests that traces of iron may be responsible for the amethyst coloration. Both quartz varieties are characterized by isotopic compositions that suggest mixing of magmatic and meteoric/marine fluids. The contribution of meteoric fluid is more significant in the final stages and reflects amethyst precipitation under more oxidizing conditions.

The present paper proposes a methodology that complies with the requirements of identifying and characterizing jadeite (and its associated minerals) for archaeological studies, avoiding the acquisition of samples and ensuring the integrity of the object. The methodology exploits a carefully selected array of techniques (optical microscopy, UV fluorescence photography, X-Ray digital radiography, infrared and Raman spectroscopies, X-Ray fluorescence and particle induced X-ray emission spectroscopies) that, despite not definitively replacing laboratory procedures, provides a first mineral and elemental evaluation of jadeite archaeological objects. The proposed methodology was applied in the characterization of twelve different jade tones, allowing the identification of major - jadeite, albite and omphacite - and minor - pumpellyite, actinolite, analcime, rutile, grossular and titanite - mineral phases. To display its advantages and limitations, this methodology was also compared with a characterization employing specific gravity measurements and with an invasive methodology based on petrography and scanning electron microscopy with energy dispersive spectroscopy.

Vibrational spectroscopies (Fourier Transform Infra Red, FTIR, and Raman) are exceptionally valuable tools for the identification and crystal&ndash, chemical study of fibrous minerals, and asbestos amphiboles in particular. Raman spectroscopy has been widely applied in toxicological studies and thus a large corpus of reference data on regulated species is found in the literature. However, FTIR spectroscopy has been mostly used in crystal&ndash, chemical studies and very few data are found on asbestos amphiboles. This paper is intended to fill this gap. We report new FTIR data collected on a suite of well-characterized samples of the five regulated amphibole species: anthophyllite, amosite, and crocidolite, provided by the Union for International Cancer Control (UICC) Organization, and tremolite and actinolite, from two well-known occurrences. The data from these reference samples have been augmented by results from additional specimens to clarify some aspects of their spectroscopic features. We show that the FTIR spectra in both the OH-stretching region and in the lattice modes region can be effective for rapid identification of the asbestos type.

The six commercial asbestos minerals (chrysotile, fibrous actinolite, crocidolite, amosite, fibrous tremolite, and fibrous anthophyllite) are classified by the IARC as carcinogenic to humans. There are currently several lines of research dealing with the inertisation of asbestos minerals among which the dry grinding process has received considerable interest. The effects of dry grinding on tremolite asbestos and anthophyllite asbestos in eccentric vibration mills have not yet been investigated. Along the research line of the mechanical treatment of asbestos, the aim of this study was to evaluate the effects of dry grinding in eccentric vibration mills on the structure, temperature stability, and fibre dimensions of tremolite asbestos from Val d&rsquo, Ala, (Italy) and UICC standard anthophyllite asbestos from Paakkila mine (Finland) by varying the grinding time (30 s, 5 min, and 10 min). After grinding for 30 s to 10 min, tremolite asbestos and anthophyllite asbestos showed a decrease in dehydroxylation and breakdown temperatures due to the increase in lattice strain and the decrease in crystallinity. Moreover, after grinding up to 10 min, tremolite and anthophyllite fibres were all below the limits defining a countable fibre according to WHO.

Metamorphic rocks have scientific significance for parsing the evolutionary process of an orogenic belt. The Wuliangshan area is a very complex region of metamorphism, where it is nearly impossible to conduct conventional geological investigation because of the extremely rugged topography and difficult travel conditions. Previous research on the area’s metamorphic rocks is limited. There are two metamorphic belts, the Yunling-Jinghong and Wuliangshan metamorphic belts, identified by means of traditional field survey. To better identify the metamorphic rocks of the Wuliangshan area, this study adopted the principal component analysis (PCA) and spectrum-area (S-A) methods, using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data, to extract the anomalies of diagnostic metamorphic minerals in metamorphic rocks, such as actinolite, chlorite, epidote, biotite, muscovite, hornblende, andalusite, staurolite, cordierite, and sillimanite. The methods are based on the principle that the metamorphic degree is reflected by the diagnostic metamorphic minerals. Profile investigation and petrographic analysis show that the identification accuracy of the diagnostic metamorphic minerals reached 85.65%. Seven concentrations of metamorphic rocks were delineated based on the extracted metamorphic mineral anomalies. Compared with previous study results, this study showed that there are metamorphic rocks in defined Regions 1, 2, 3, 4 and 6, which are consistent with existing data; whereas in Regions 5 and 7, there is new information regarding the existence of metamorphic rocks, which may offer new clues about the formation of this area through additional studies. The results of this study not only reveal detailed information for geological survey of the Wuliangshan area but also provide useful methods for future surveys.

This paper provides new mineralogical and morphological characterizations of calcic amphiboles from hydrothermally altered dolerites from France to discuss their potential to contain naturally occurring asbestos (NOA) and to release elongated mineral particles corresponding to asbestos fibers, or asbestos-like fibers, into the air. The calcic amphiboles were characterized using electron microprobe analysis, scanning and transmission electron microscopy. The results underline that fibrous occurrences of actinolite and ferro-actinolite regularly occur in hydrothermally altered dolerites, both in the groundmass and in quartz veins. In the groundmass, actinolitic amphiboles crystallize at the expense of magmatic clinopyroxenes and are rarely fibrous. Conversely, actinolite and ferro-actinolite fibers from quartz veins are potentially asbestiform to clearly asbestiform. The identification of quartz veins in hydrothermally altered dolerites is, therefore, an important parameter which should draw attention to the possible presence of asbestiform actinolite fibers. The mineralogical characterization of such veins as well as the estimation of their thickness and density is an important point to consider during studies involving NOA issues. Moreover, the degree of weathering of the dolerites, which directly affects the ability of non-asbestiform actinolite crystals to dissociate into very thin fibers, regarded as cleavage fragments instead of as asbestos, is also a key parameter to consider. Hydrothermally altered dolerites are common rocks likely to be exploited by the quarrying industry to produce aggregates or to be affected by construction works. Due to the abundance of actinolite fibers that they may contain locally, these rocks become priority targets to be monitored in terms of geological characterization and airborne fiber emission to ensure the protection of populations and workers.

The shape of a thermoluminescence (TL) glow curve has fundamental importance for calculating the characteristic parameters of trap levels within the band gap. TL analysis are mostly based on the three-parameter general order kinetics model. The parameters are activation energy, order of kinetics, and frequency factor. Peak shape method is one of the most prominent methods for extracting the activation energy from a TL curve. An overview of different peak shape methods along with an alternative approach formulated directly from basic TL equations is presented in this chapter. Generally, peak shape method requires prior knowledge of order of kinetics to determine activation energy which creates a difficulty due to the non-uniqueness of symmetry factor for a particular value of order of kinetics. A modified version of peak shape method which is free from this constraint is discussed here. Activation energies from experimental curves of tremolite and actinolite are estimated using peak shape method. Limitation of peak shape method for saturated TL peaks with heavy retrapping is also discussed.

International audience; Electron back-scattered diffraction (EBSD) maps and crystal-preferred orientation (CPO) of eclogite-facies (omphacite and garnet) and amphibolite-facies (hornblende and actinolite) phases are reported for understanding the rheological behaviour of crust during subduction. Two types of eclogites from the subduction-related high-pressure/low-temperature type Sanbagawa metamorphic belt, Japan, have been investigated. Type-I eclogite (sample Sb-1) is composed of garnet, omphacite, secondary actinolite and hornblende. Type-II eclogite (samples Sb-2 and Sb-2a) are mainly composed of omphacite, garnet, and retrograde hornblende with no actinolite. Omphacite, the peak eclogite-facies phase, exhibits L-type CPO (maximum density of [001] axes parallel to and high density of {110} poles normal to the lineation) in Type-I eclogite, suggesting intra-crystalline plasticity with [001] {110} and {110} active slip systems, indicating a constrictive strain regime at mantle depths. Omphacite in Type-II eclogite exhibits a similar fabric but with much weaker CPO. Using the LS-index symmetry analysis (one for the end-member L-type, zero for the end-member S-type, and intermediate values for LS-types), a progressive change in LS index of 0.80 for Type-I and 0.61 to 0.44 for Type-II eclogites is observed. These values suggest a transition from axial extension parallel to the lineation for Sb-1 and weaker CPO associated with pure or simple shear for Sb-2 and Sb-2a. Garnet, the second dominant phase in the eclogite-facies stage, exhibits weak and complex fabric patterns in all eclogite types, behaved like rigid bodies and does not show plastic deformation. Amphibolite-facies phases (e.g., hornblende and actinolite) exhibit more than two types of CPO. Hornblende and actinolite in Type-I eclogite have a strong CPO along [001] axes aligned parallel to the lineation, indicating homotactic crystal growth probably by the replacement of omphacite during the early stages of retrogression. Type-II eclogites have weak CPO in hornblende but with characteristic alignment of [001] parallel to the lineation and other poles to planes (100), (010), and {110} normal to the lineation. This fabric might have resulted from a cataclastic deformation and could be related to the late-"D1" deformation stage in the Sanbagawa metamorphic belt.

A suite of samples collected mainly from river cobbles in the Mt. Hibernia Complex in SE Jamaica includes metamorphosed basaltic and clastic sedimentary rocks, which are interpreted here as part of a Cretaceous accretionary prism. The metabasic rocks occur as blueschists and greenschists, whereas the metasedimentary rocks are former greywackes s.l ., or psammopelites, and can now be characterized as phyllites. Eight characteristic mineral assemblages can be defined within the metabasic sample suite, involving amphibole (Na amphibole and/or actinolite), pumpellyite, lawsonite, epidote, chlorite, titanite, phengite, albite and quartz. Augite is an important relict phase of the magmatic source rocks. White mica, chlorite and quartz predominate in the phyllites in variable proportions, but Na amphibole, epidote, albite and titanite may also be important. Calculated P–T pseudosections show that the assemblage glaucophane–pumpellyite–chlorite occurs only in a restricted field along the lower P–T limit of the blueschist facies. Pseudosections also indicate that peak P–T conditions for the blueschist samples studied here lie in the range 6.5–7.2 kbar and 310–340°C, that is at the upper stability limit of pumpellyite and lawsonite, and in the range 6.4–7.8 kbar and 340–380°C for greenschist samples. The P–T range for phyllites overlaps with both. Thus, blueschists and greenschists represent comparable pressure but different temperature conditions of formation. Literature data on the mapped distribution of metabasic rock types suggests an isobaric metamorphic field gradient in the Mt. Hibernia Complex, with temperatures increasing slightly but significantly from blueschist to greenschist zones. We interpret this gradient as reflecting either increasing temperatures in the accretionary complex away from the subducting slab or thermal re-equilibration in a cooling subduction zone. Sodium-Ca amphiboles, predominantly winchite, are commonly observed as rims around Na amphibole and formed together with albite porphyroblasts during decompression. Comparison with published information on the miscibility gap between Na and Ca amphiboles shows that many of these compositions fall within this gap for temperatures around 350°C. Thus, these amphiboles either grew metastably below the critical temperature of the gap, or some as yet undefined parameter must be responsible for drastically altering the shape of the gap. Published descriptions of deformation in the Mt. Hibernia Complex show that coaxial pure shear initially predominates, as is common in accretionary complexes; however, a late shearing event, postulated here to be caused by the collision between the Great Arc of the Caribbean and the continental margin of North America at 75–70 Ma, is held responsible for the rapid exhumation of the combined blueschist–greenschist sequence.

Iron oxide–apatite (IOA) ore deposits occur globally and can host millions to billions of tons of Fe in addition to economic reserves of other metals such as rare earth elements, which are critical for the expected growth of technology and renewable energy resources. In this study, we pair the stable Fe and O isotope compositions of magnetite samples from several IOA deposits to constrain the source reservoir of these elements in IOAs. Since magnetite constitutes up to 90 modal% of many IOAs, identifying the source of Fe and O within the magnetite may elucidate high-temperature and/or lower-temperature processes responsible for their formation. Here, we focus on the world-class Los Colorados IOA in the Chilean iron belt (CIB), and present data for magnetite from other Fe oxide deposits in the CIB (El Laco, Mariela). We also report Fe and O isotopic values for other IOA deposits, including Mineville, New York (USA) and the type locale, Kiruna (Sweden). The ranges of Fe isotopic composition (δ56Fe, 56Fe/54Fe relative to IRMM-14) of magnetite from the Chilean deposits are: Los Colorados, δ56Fe (±2σ) = 0.08 ± 0.03‰ to 0.24 ± 0.08‰; El Laco, δ56Fe = 0.20 ± 0.03‰ to 0.53 ± 0.03‰; Mariela, δ56Fe = 0.13 ± 0.03‰. The O isotopic composition (δ18O, 18O/16O relative to VSMOW) of the same Chilean magnetite samples are: Los Colorados, δ18O (±2σ) = 1.92 ± 0.08‰ to 3.17 ± 0.03‰; El Laco, δ18O = 4.00 ± 0.10‰ to 4.34 ± 0.10‰; Mariela, δ18O = (1.48 ± 0.04‰). The δ18O and δ56Fe values for Kiruna magnetite yield an average of 1.76 ± 0.25‰ and 0.16 ± 0.07‰, respectively. The Fe and O isotope data from the Chilean IOAs fit unequivocally within the range of magnetite formed by high-temperature magmatic or magmatic–hydrothermal processes (i.e., δ56Fe 0.06–0.49‰ and δ18O = 1.0–4.5‰), consistent with a high-temperature origin for Chilean IOA deposits. Additionally, minimum formation temperatures calculated by using the measured Δ18O values of coexisting Los Colorados magnetite and actinolite separates (630 °C) as well as Fe numbers of actinolite grains (610–820 °C) are consistent with this interpretation. We also present Fe isotope data from magmatic magnetite of the Bushveld Complex, South Africa, where δ56Fe ranges from 0.28 ± 0.04‰ to 0.86 ± 0.07‰. Based on these data and comparison to published Fe and O stable isotope values of igneous magnetite, we propose extending the magmatic/high-temperature δ56Fe range to 0.86‰. Considering that the Chilean IOAs and Kiruna deposit are representative of IOA deposits worldwide, the Fe and O stable isotope data indicate that IOAs are formed by high-temperature (magmatic) processes.

The detection of hydrous minerals on Mars is of great importance for revealing the early water environment as well as possible biotic activity. However, few studies focus on abundance retrieval of hydrous minerals for some difficulties. In this paper, we studied the area around the Mars Science Laboratory (MSL) landing site, to identify hydrous minerals and retrieve their abundance. Firstly, the distribution of hydrous minerals was extracted using their hydration features. Then, a sparse unmixing algorithm was applied along with the CRISM spectral library to retrieve the abundance of hydrous minerals in this area. As a result, seven hydrous minerals were retrieved, i.e. actinolite, montmorillonite, saponite, jarosite, halloysite, szomolnokite and magnesite and, the total concentration of all hydrous minerals was as high as 40 vol% near the lower reaches of Mount Sharp. Our results were consistent with results from related research and the in-situ analysis of the MSL rover Curiosity.

The Paleozoic Bayazeh ophiolite is situated in the western part of the Central-East Iranian microcontinent (CEIM). This ophiolite consists of serpentinised peridotites, metagabbros, metamorphosed ultrabasic dykes, metapicrites, serpentinites and metamorphosed listwaenites which are covered by Late Paleozoic schists and marbles. The unique petrological characteristic of this ophiolite is due to regional metamorphism, which produced listwaenites by carbonation of serpentinites. The mineral association of the Bayazeh metamorphosed listwaenites is represented by amphiboles (tremolite and actinolite), carbonates (dolomite and calcite), quartz, serpentine (antigorite), chromian spinel, ferritchromite and chlorite (pycnochlorite). The main textures are nematoblastic and granoblastic. Rockforming minerals and the association of the outcrops with serpentinites indicate that the amphibole-bearing listwaenites were generated by regional metamorphism of serpentinites. The mineral assemblage of these rocks and the chemical composition of chromian spinels and amphiboles reveal that these minerals were metamorphosed under upper greenschist to lower amphibolite facies P-T conditions. Relicts of well-preserved chromian spinel cores in the studied rocks were used as a petrogenetic indicator. The high Cr and Mg values, together with the low Fe3+ and Ti contents of the serpentinite chromian spinels confirm their magmatic nature. The chemical characteristics of the investigated chromian spinels suggest that the protolith should have been a harzburgite belonging to a suprasubduction zone geotectonic setting.

The most highly valued placer nephrite deposits in the world occur in the Yurungkash and Karakash Rivers (also known as the White and Black Jade Rivers) in Hetian, Xinjiang, Northwest China. However, the ages of these deposits and the geological environment in which they formed are not known, and their genesis, mineral compositions, and geochemical and petrographic characteristics are poorly constrained. More than 50 samples of white, green, brown, and black nephrites were examined from the placers with the aim of understanding the timing and processes of formation of the nephrite and its archeological significance. The samples collected comprise fine-grained tremolite with highly variable Fe 2 O 3 (total) contents (green nephrite = 0.77–3.97 wt.%; black nephrite = 0.56–16.23 wt.%) and FeO concentrations (green = 0.67–3.18 wt.%; black = 0.48–9.55 wt.%). XRD and petrographic studies indicate that placer nephrite is more mineralogically complex than primary nephrite and contains tremolite (most samples > 80.1 wt.%), diopside (≤ 21.3 wt.%), chlorite (≤ 10.5 wt.%), zircon, titanite, apatite, spinel, garnet, epidote, barite, actinolite, sphalerite, pyrrhotite, graphite, calcite, and iron-hydroxide. The black nephrite contains significant amounts of graphite and Fe(OH) 3 as mineral inclusions. The presence of strong negative Eu anomalies (0.04–0.26), flat REE patterns, and δ 18 O = 1.3‰–8.4‰ (330 °C) and δD = − 17.7‰ to − 87.1‰ (350–650 °C) for the ore-forming fluids suggests that the deposit is a Mg-skarn formed by the metasomatism of dolomite by fluids derived from local granite/granodiorite intrusions with quite few samples showing geochemical characteristics of serpentinite-related nephrite. Zircons inclusions in the placer nephrite are oval in shape, 0.1), positive Ce anomalies (Ce/Ce*) of ≥ 1.31. Zircons from both Alamas and two placer rivers have similar geochemical signatures, suggesting that the zircon grains in the placer nephrite were derived from the magmatic rocks that host the nephrite deposits. Zircon grains from two samples of black nephrite yield concordant SHRIMP U–Pb ages of 389 ± 4 Ma, 397.1 ± 3.5 Ma, and 440.7 ± 4.4 Ma. Zircon grains from one sample of green nephrite yield concordant SHRIMP U–Pb ages of 377.8 ± 6.2 Ma. These ages are roughly close to those of the emplacement ages of the Alamas and Buya granodiorites and probably represent the recrystallization of zircons or formation ages of the nephrite within the Hetian Nephrite Belt. Some igneous zircon grains yield ages of ~ 600 Ma and were probably sourced from the wall rocks and entrained in the ~ 400 Ma magma. Petrographic studies indicate that the Mg-skarns that host the primary nephrite have been thermally metamorphosed. The nephrite formed during early retrogression from diopside skarn → tremolite skarn (coarse-grained), epidote skarn → tremolite skarn and coarse-grained tremolite → fined-grained tremolite. The first step in the formation of nephrite was alteration of the Mg-dolomite to form an assemblage of diopside, epidote, and minor grossular. This was followed by metasomatism of the skarn assemblage by pneumatolitic/hydrothermal fluids derived from local granitoid intrusions, which, combined with later brittle deformation, formed the fine-grained tremolite (nephrite). Zircon inclusions in the primary and placer nephrite at Hetian have similar geochemical characteristics, implying that the nephrites are genetically related. However, the placer nephrite contains more complex phases or associated minerals than does the primary nephrite. Primary nephrite is generally regarded as the main source of the downstream placer nephrite deposits. The fine grain-size of the tremolite and small quantities of accessory minerals are the main characteristics of high-quality placer nephrite. A combination of transport by glacial melt-water and the relatively high altitude (the primary source region and the placer deposits differ in elevation by 3 km) led to the formation of the two extensive placer nephrite deposits at Hetian.

As results of X-ray diffraction analysis, samples of asbestos and soil were composed maily of dolomite (, tremolite (), actinolite (), talc (), calcite () and small amounts of quartz () and clay minerals. The average size of asbestos fibers was about and maximum of some asbestos was in length. The aspect ratio of asbestos fiber were over 3 : 1 and inclined extinction in the range of . Single isolated fragments of asbestos are probably fiber and acicula form in crystal edge along the cleavage plane. Tremolite that composed main asbestos mineral in rock and soil around Dong-a mine is higher content of Fe than actinolite asbestos.

Iron formations, hematitic cherts (jaspers), ‘tuffites’, silica-iron exhalites and other metalliferous chemical sedimentary rocks are important stratigraphic marker horizons in a number of volcanogenic massive sulfide (VMS) districts worldwide, forming during episodes of regional hydrothermal activity. The VMS prospective ca. 484–464 Ma Tyrone Igneous Complex of Northern Ireland represents a structurally dissected arc-ophiolite complex that was accreted to the composite margin of Laurentia during the Grampian orogeny (ca. 475–465 Ma), and a potential broad correlative to the VMS-rich Buchans–Robert's Arm arc system of the Newfoundland Appalachians. Silica-iron-rich rocks occur at several stratigraphic levels in the Tyrone Igneous Complex spatially and temporally associated with rift-related basalts (e.g., Fe–Ti-rich eMORB, IAT, OIB) and zones of locally intense hydrothermal alteration. In the ca. 475–474 Ma lower Tyrone Volcanic Group, these rocks are characterized by massive, 1–5 m thick blood-red jaspers, hematitic siltstones and mudstones, and intensely silica-hematite altered tuffs and flows. Their mineralogy is dominated by quartz–hematite ± magnetite–(chlorite-sericite ± tremolite/actinolite), with Fe concentrations rarely exceeding 10 wt.%. Relict textures (including the presence of coalesced spherules of silica-iron oxides) in rocks exposed at Tanderagee NW, Creggan Lough and Tory's Hole are indicative of seafloor exhalation, whereas replacement of the original volcanic stratigraphy is evident to varying degrees at Tanderagee, Beaghbeg and Bonnety Bush. In the structurally overlying ca. 473–469 Ma upper Tyrone Volcanic Group, chemical sedimentary rocks include recrystallized: (i) thin and laterally-restricted jaspers in thick sequences of graphitic pelite at Boheragh; and (ii) laterally-persistent sulfidic cherts and ironstones dominated by quartz–hematite–magnetite–(chlorite) or quartz–pyrite–(chlorite) in sequences of tuff at Broughderg. Compared to chemical sedimentary rocks associated with VMS deposits worldwide, their geochemical characteristics are most similar to silica-iron exhalites of the Mount Windsor Subprovince (SE Australia) and jaspers of Central Arizona, Bald Mountain (Northern Maine), the Urals, Iberian Pyrite Belt and Lokken ophiolite (Norway). Positive Eu anomalies (at Slieve Gallion and Tanderagee NW), elevated Cu + Pb + Zn, Au, Fe/Ti, Fe/Mn, Sb, Ba/Zr and Fe + Mn/Al, together with low REE, Sc, Zr and Th, are indicative of a greater hydrothermal component and potentially more VMS-proximal signatures. Based on bulk ironstone geochemistry, Bonnety Bush, Tanderagee NW-Creggan Lough, Broughderg and Drummuck (Slieve Gallion) are considered the most VMS prospective areas in the Tyrone Igneous Complex and warrant further exploration.

New occurrences of large-scaled Zn-Pb deposits are recently found in the Danjang-myeon, Milyang. They are skarn-type deposits which replaced the intercalated limestone beds in the Jeonggaksan Formation. This study aims at characterizing occurrences, mineralogy, and chemistry of Zn-Pb ores and skarn minerals. Skarn orebodies are mainly found in 3 areas, named Gukjeon-ri, Gorye-ri, and Gucheon-ri orebodies, where sphalerite found as main ore mineral in 200-300 m in height and amount of galena increases as altitude does. Ores are dark grey to dark green in color and closely related with clinopyroxene zone. They occur with hedenbergite, grossular, actinolite, epidote, and small amounts of axinite, calcite, and quartz. Main ore mineral is sphalerite which includes tiny spotted grains of galena and chalcopyrite and becomes rich in grade in association with clinopyroxene and epidote. FeS contents in sphalerite show relatively wide range between 1.53 and 23.07 mole%, whose contents intend to increase towards biotite granite known as ore-related igneous rocks. CdS contents are in the range of 0.22-0.93 mole%, showing decrease tendency from southwest (Gukjeon-ri) to northeast (Gucheon-ri). Zn-Pb deposits developed in Danjang-myeon reveal decrease in temperature with increase of altitude, leading to gradual changes in compositions of ore and skarn minerals.

The Astamal Fe-LREE skarn deposit is the largest iron skarn in NW Iran. It is a unique case, as a distal skarn deposit which crops out approximately 600 m from the associated Oligo-Miocene granodioritic pluton. This deposit formed in the south-southwest of the pluton where fractures and faults within the Upper Cretaceous volcano-sedimentary host rocks acted as conduits for the mineralizing fluids. The deposit contains three iron ore bodies: southern, northern and eastern. The main mineral assemblage within the ore zones is characterized by magnetite, pyrrhotite and pyrite, with lesser quantities of chalcopyrite, hematite, goethite and limonite. The skarn minerals predominantly comprise garnet, epidote, actinolite, calcite, quartz, clinopyroxene and chlorite (in order of abundance). Retrograde alteration is strongly developed in the skarn zone where most of the garnet has been pervasively altered to secondary minerals (e.g. epidote, calcite and quartz) both in the rims and the cores whereas the majority of the clinopyroxene has been replaced by a hydrous retrograde mineral assemblage (e.g. tremolite, actinolite and chlorite). Garnets with andradite–grossular compositions are the dominant mineral in the skarn zone, which are generally isotropic with a narrow compositional range along the growth lines (Adr94.3–64.5Grs21.9–2.7Alm11.1–0.2). These garnets are Fe-rich and have high Fe/(Fe + Al) ratios (between 0.96 and 0.78). Cu and Ni are enriched in the garnets. This suggests that these elements were enriched in the hydrothermal fluids from which the garnet precipitated. This is supported by the presence of chalcopyrite and Ni-bearing massive magnetite in the study area, which also suggests that Cu and Ni were enriched in the late stage ore-bearing hydrothermal fluids. Clinopyroxene with a hedenbergitic composition is generally homogenous and has particularly high Fe/Fe + Mg ratios (between 0.99 and 0.86) and is poor in TiO2, MnO and Cr2O3. High Zn concentrations were also detected in the clinopyroxenes (up to 1044 ppm), despite an absence of significant Zn mineralization (such as sphalerite) in the district. Therefore, it is believed that the proportion of Zn in the hydrothermal fluids decreased significantly from the time of clinopyroxene formation to the period of the sulfide deposition phase. Allanite and LREE-bearing epidotes are the main LREE bearing minerals in this deposit. The epidote is also Fe-rich with high Fe/(Fe + Al) ratios (between 0.32 and 0.44). Due to a lack of replacement texture between both garnet and clinopyroxene and garnet and actinolite (which is formed by alteration of clinopyroxene), it is believed that these two minerals have grown simultaneously and are coexisting minerals. In the Astamal skarn, these minerals can be stable and coexisting at temperatures between 490 and 560 °C and LogƒO2 = − 16 to − 31.

Concentrations of biotite flakes were distributed at multiple locations during the site investigation for the Tianchi Pumped Storage Power Station project in Henan Province, China. Rock mass was highly weathered on both sides of a prominent fault, and a large number of white and gray, locally yellow–brown, argillaceous agglomerations were observed. The local core at the end of the ZK44 hole presented a gray and white sandstone structure. Petrochemical tests, which included sheet identification, scanning electron microscopy, electron probe analysis, and X-ray diffraction, showed that the main alteration types were mica-rich-type altered rocks and clay-type altered rocks, which were accompanied by chlorite, epidote, actinolite, and other alteration minerals. According to the mechanical test results, the smallest antidisintegration index was 84 %, disintegration was easily accomplished, the maximum axial free expansion rate was 0.00204 %, the maximum free expansion rate in the radial direction was 0.0178 %, and maximum lateral constrained expansion rate was 0.0194 %. The swelling pressure of all the specimens did not exceed 10 kPa, and the clay-type altered rocks exhibited three large expansion parameters. Uniaxial and triaxial compression tests showed that the strength of granite, as reflected by its deformation and elastic moduli, decreased to values even lower than those of highly weathered rocks because of alteration. The poor characteristics of the altered rock presented great challenges for support or lining during the construction and operation stages. After excavation, the expanded altered rocks should be cleaned up immediately, the support or lining should be in place immediately, and water should be drained in time.

The Zloty Stok Au-As deposit (SW Poland) hosts two distinct nephrite varieties: 'type 1' - a grayish green or pale green, translucent, with waxy to greasy luster nephrite composed of actinolite and abundant lollingite; 'type 2' - a deep or intense green, less-translucent, with sub-vitreous to dull luster nephrite composed of tremolite and actinolite, with rare lollingite and arsenopyrite. 'Nephrite type 1' shows evidence for more intense metasomatism and recrystallization than 'type 2', e.g., more abundant arsenide, sulfosalt, and tungstate minerals, and higher Fe, As, and Co concentrations. The tremolite and actinolite in both types formed at the expense of dolomite-either directly from dolomite or through diopside formation. Calcite is a byproduct of the amphiboles' formation directly from dolomite. Amphiboles have Cr2O3 and NiO concentrations of 0.00-0.04 wt.% and 0.00 wt.%, respectively, typical of dolomite-related nephrites. Diopside composition (up to 51 Wo, 0.00-0.05 wt.% Cr2O3 and 0.00-0.09 wt.% NiO) is similar to other dolomite-related nephrite compositions. Bulk-rock Cr and Ni (

Serpentinites are rocks, often used in buildings, formed in large extent by minerals of the serpentine group: chrysotile, antigorite, lizardite, and polygonal serpentine. The fibrous type (e.g. chrysotile) of serpentine group minerals, along with several amphibole varieties (e.g. actinolite and tremolite), are the major components of asbestos family. The exposure to fine fibrous asbestos powder is linked to diseases such as pleural mesothelioma and asbestosis. The identification of the main varieties of the serpentine group, laminated or fibrous, becomes an issue of great interest for public health. This work introduces an analytical strategy able to distinguish the different serpentine polymorphs directly on the sample, allowing the analysis within their textural environment, evidencing at the micrometer scale the mineral reactions of the phases. Samples coming from the Koniambo massif (Grande Terre Island, New Caledonia) were studied by means of optical microscopy, scanning electron microscopy–energy dispersive X-ray spectroscopy, and Raman spectroscopy. Raman peaks observed in the high wavenumber spectral range of 3550–3850 cm−1, associated with OH stretching vibrations, allow the discrimination of the all four serpentine varieties. The relationship between the different varieties of serpentine, at a micrometric scale, in complex samples, has been investigated by two-dimensional Raman mapping. Copyright © 2015 John Wiley & Sons, Ltd.

This study used spectrometry to determine the spectral absorption of five types of mafic-ultramafic rocks from the Kaishantun ophiolite suite in Northeast China. Absorption peak wavelengths were determined for peridotite, diabase, basalt, pyroxenite, and gabbro. Glaucophane, actinolite, zoisite, and epidote absorption peaks were also measured, and these were used to distinguish such minerals from other associated minerals in ophiolite suite samples. Combined with their chemical compositions, the blueschist facies (glaucophane + epidote + chlorite) and greenschist facies (actinolite + epidote + chlorite) mineral assemblage was distinct based on its spectral signature. Based on the regional tectonic setting, the Kaishantun ophiolite suite probably experienced the blueschist facies metamorphic peak during subduction and greenschist facies retrograde metamorphism during later slab rollback.

Worldwide studies have been done about the toxicity and carcinogenicity of asbestos minerals occurring in ophiolitic rocks. Inhalation of asbestos due to environmental exposure could cause malignant mesothelioma and lung cancers. In particular, the ophiolitic rocks in Tethyan realm represents a serious enivironmental concern due to both the presence of asbestos-like minerals and the large Cr abundance that is prone to solubilisation as CrVI. At the Pollino Geopark (southern Apennines, Italy), serpentinites-rich ophiolite rocks and sediments of the Frido Unit crop-out. In these rocks, tremolite, an asbestos-like mineral, is typically intergrown with fibrous antigorite and chrysotile. Tremolite shows acicular, friable, fibrous, and elongated habitus, can be easily released into the environment as a result of both natural processes and anthropogenic activities. In the analyzed rocks, tremolite is present mainly in veins as much as in the matrix and forms crowns around clinopyroxene porphyroclasts. The different analytical techniques showed the recognition of the amphibole-like minerals (actinolite and tremolite) that are the dominant phases, with a small percentage of Fe2+. The presence of Fe in the “ideal” tremolite asbestos could cause pathological effects for the human living in the Pollino Geopark. This study has several environmental relevant implications, including, for example, the realization of national health protecting programs and the mapping of natural sites characterized by the presence of asbestos minerals in Pollino Geopark and in others area where outcrop asbestos bearing ophiolitic rocks.

Asbestos mineral fibers have been associated with the development of a variety of diseases in humans and experimental animals, including asbestosis, lung cancer, and mesothelioma. Asbestos includes several mineral types divided into two mineral groups, serpentine and amphibole forms. Chrysotile is the serpentine mineral classified as asbestos, whereas the amphiboles include amosite, crocidolite, tremolite, actinolite and anthophyllite. There are a number of mineral fibers that occur with asbestiform morphology and that have been associated with various asbestos-induced diseases. These include the Libby amphiboles (associated with a vermiculite mine northwest of Libby, MT), erionite (in Turkey and North America), fluoro-edenite (in Sicily), and perhaps balangeroite (in Italy). In addition, each of the asbestos minerals occurs in a non-fibrous form, and these may occur as cleavage fragments that satisfy the definition for a fiber, i.e., particles with an aspect ratio of at least 3:1 and roughly parallel sides. Cleavage fragments of non-asbestiform minerals have not been associated with asbestos-induced diseases nor are these minerals regulated by the Occupational Safety and Health Administration. Finally, there are a number of other mineral species which can occur in human lung samples that satisfy the definition for a fiber as given above. These similarly have not been associated with asbestos-induced diseases. All of these various minerals satisfying the definition for a fiber can be referred to as elongated mineral particles (EMP). It is the purpose of this presentation to discuss the role of scanning electron microscopy (SEM) equipped with an energy dispersive x-ray analyzer (EDXA) in the detection and classification of EMP in human lung samples.

The issue of Elongated Mineral Particles (EMP) in building materials has been revealed during roadworks in 2013 in France. In fact, road coating aggregates are made of specific rock gravels that can contain Naturally Occurring Asbestos (NOA), which is mainly actinolite. The legislation refers to six regulatory asbestos, that consist in asbestiform habitus of the six minerals. The current technical standard is not adapted for analyzing natural material, as it cannot distinguish the asbestiform fibers and the cleavage fragments fibers. Therefore, the Eichrom Laboratories developed an internal method for analyzing rock gravel and identifying the different kind of EMP. This analytical method is based on an accurate sample preparation and three techniques at different resolutions: a petrological analysis with a stereomicroscope, a mineralogical analysis with a Polarized Light Microscope (PLM) and structural and with a Transmission Electronic Microscope (TEM). This innovative procedure is reinforced by the expertise of geologists, which is not necessary for the manufactured products. Putting the process in a national standard is essential for result homogenization of the asbestos testing laboratories.

The study performed on the host rocks of the Tighardine deposit allows proposing a new lithostratigraphic succession, mainly constituted of three volcanic and volcano–sedimentary units and dolomitic bed and lenses. Volcanic rocks consist mainly of basalt, andesite, and less common dacites. They are characterized by a FeO/MgO ratio range of 0.8–10.0, TiO2 contents ranging between 0.6 and 3.2 wt%, and high values of Zr/Y (7.1 to 9.9), Nb/Y (0.5 to 1.1), and Nb/La (0.7 to 1.1) ratios, providing good evidence of intracontinental tholeiitic character with a subalkaline affinity. They have no Nb anomaly and high Ti/Yb ratios (> 4000), suggesting their derivation from an enriched source and emplacement in an extensional continental setting. Fractional crystallization is the main differentiation mechanism of these rocks, and crustal contamination may have contributed to their final geochemical signature. U/Pb dating these volcanic rocks revealed ages of 603.5 ± 3.3 and 596.1 ± 3.3 Ma. These early Ediacaran ages chronologically correlate to the age of the Lower Ouarzazate Supergroup located in the Precambrian area of the Moroccan Anti-Atlas. The Tighardine formations underwent superimposed polyphase metamorphism. Mineralogical investigations show evidence of local intense thermal metamorphism and hydrothermalism evidenced by andalusite and cordierite in pelites; diopside, tremolite, and actinolite in dolomite; and by actinolite in volcanic rocks. Late brown biotite may overgrow early metamorphic minerals in all facies. Hydrothermal transformation is particularly confined in the crossings of N–S and N70 to E–W faults. The local thermal metamorphism and hydrothermalism result from a hypothetical granitic intrusion at depth. The early disseminated polymetallic mineralization (Cu–Pb–Zn) is confined in the Ediacaran volcanic and volcanosedimentary formation of Tighardine. This volcanic activity contributes to the genesis of the Tighardine ore deposit. The economic ore deposit is related to the recrystallization and brecciation of this early-disseminated polymetallic mineralization, during the Variscan event or later.

Iron oxide-apatite (IOA) or Kiruna-type deposits are an important source of iron and other elements including REE, U, Ag, and Co. The genesis of these deposits remains controversial, with models that range from a purely magmatic origin to others that involve variable degrees of hydrothermal fluid involvement. To elucidate the formation processes of this deposit type, we focused on the Chilean Iron Belt of Cretaceous age and performed geochemical analyses on samples from El Romeral, one of the largest IOA deposits in northern Chile. We present a comprehensive field emission electron microprobe analysis (FE-EMPA) dataset of magnetite, apatite, actinolite, pyroxene, biotite, pyrite, and chalcopyrite, obtained from representative drill core samples. Two different types of magnetite grains constitute the massive magnetite bodies: an early inclusion-rich magnetite (Type I); and a pristine, inclusion-poor magnetite (Type II) that usually appears as an overgrowth around Type I magnetite. High V (∼2500–2800 ppm) and Ti concentrations (∼80–3000 ppm), and the presence of high-temperature silicate mineral inclusions (e.g., pargasite, ∼800–1020 °C) determined by micro-Raman analysis indicate a magmatic origin for Type I magnetite. On the other hand, high V (2300–2700 ppm) and lower Ti (50–400 ppm) concentrations of pristine, inclusion-poor Type II magnetite indicate a shift from magmatic to hydrothermal conditions for this mineralization event. Furthermore, the composition of primary actinolite (Ca- and Mg-rich cores) within Type II magnetite and the presence at depth of fluorapatite and high Co:Ni ratios (>1–10) of pyrite mineralization are consistent with a high temperature (up to 840 °C) genesis for the deposit. At shallow depths of the deposit, the presence of pyrite with low Co:Ni ratios (

Cerro de Pasco (Peru) is known for its large epithermal polymetallic (Zn-Pb-Ag-Cu-Bi) mineralization emplaced at shallow level, a few hundred meters below the paleo-surface, at the border of a large diatreme–dome complex. Porphyry-style veins crosscutting hornfels and magmatic rock clasts are found in the diatreme breccia and in quartz–monzonite porphyry dikes. Such mineralized veins in clasts allow investigation of high-temperature porphyry-style mineralization developed in the deep portions of magmatic–hydrothermal systems. Quartz in porphyry-style veins contains silicate melt inclusions as well as fluid and solid mineral inclusions. Two types of high-temperature (> 600 °C) quartz–molybdenite–(chalcopyrite)–(pyrite) veins are found in the clasts. Early, thin (1–2 mm), and sinuous HT1 veins are crosscut by slightly thicker (up to 2 cm) and more regular HT2 veins. The HT1 vein quartz hosts CO2- and sulfur-rich high-density vapor inclusions. Two subtypes of the HT1 veins have been defined, based on the nature of mineral inclusions hosted in quartz: (i) HT1bt veins with inclusions of K-feldspar, biotite, rutile, and minor titanite and (ii) HT1px veins with inclusions of actinolite, augite, titanite, apatite, and minor rutile. Using an emplacement depth of the veins of between 2 and 3 km (500 to 800 bar), derived from the diatreme breccia architecture and the supposed erosion preceding the diatreme formation, multiple mineral thermobarometers are applied. The data indicate that HT1 veins were formed at temperatures > 700 °C. HT2 veins host assemblages of polyphase brine inclusions, generally coexisting with low-density vapor-rich inclusions, trapped at temperatures around 600 °C. Rhyolitic silicate melt inclusions found in both HT1 and HT2 veins represent melt droplets transported by the ascending hydrothermal fluids. LA-ICP-MS analyses reveal a chemical evolution coherent with the crystallization of an evolved rhyolitic melt. Quartz from both HT1 and HT2 veins also contains secondary, low-temperature (~ 300 °C) brine and aqueous fluid inclusions that record the cooling of the system. Both vein types are locally crosscut and/or reopened by a pre-diatreme polymetallic event consisting of pyrite, sphalerite with “chalcopyrite disease,” galena, chalcopyrite, tetrahedrite–tennantite, and minor quartz. LA-ICP-MS analyses of mineral and high-temperature fluid inclusions hosted in HT1 and HT2 veins and in situ secondary-ion mass spectrometry oxygen isotope analyses of vein quartz indicate a magmatic signature for the mineralizing fluids with no major meteoric water input and allow reconstruction of the source and chemical evolution of fluids that formed these porphyry-style veins as snapshots of the early and deep mineralizations at Cerro de Pasco. This detailed study of the porphyry-type mineralization hosted in clasts offers a unique opportunity to reconstruct the late magmatic and early hydrothermal evolutions of porphyry mineralization underlying the world-class Cerro de Pasco epithermal polymetallic (Zn-Pb-Ag-Cu-Bi) deposit.

Fe-Ti-oxide micro-inclusions in clinopyroxene of oceanic gabbro from the mid Atlantic ridge have been studied using electron backscatter diffraction and electron probe microanalyses. A first generation of Fe-Ti-oxide inclusions occurs as needles or elongated plates lying in the (010) plane of the clinopyroxene host. The inclusions show distinct elongation directions following “irrational” planes either nearly parallel to the “c” or nearly parallel to the “a” axis of the clinopyroxene host. The habit planes correspond to inclusion-host interfaces, where densely packed oxygen layers of the inclusion and host phases are coherent across the interface. Both inclusion types have distinct crystallographic orientation relations to the host, which are determined by the nearly parallel alignment of densely packed oxygen layers in the inclusions and the clinopyroxene host. Based on the angle between the two elongation directions primary formation of the inclusion at 800° to 900 °C was inferred. Initially, homogeneous Ti-bearing magnetite was precipitated together with titanian pargasite lamellae due to reaction of early magmatic clinopyroxene with late magmatic fluid or melt. After cooling below 600 °C the Ti-magnetite decomposed into an oriented magnetite + ulvospinel intergrowth. Late stage hydrothermal alteration leads to the corrosion of the magnetite-ulvospinel inclusions and partial replacement by ilmenite as well as newly precipitated homogeneous ilmenite plates that are closely associated with actinolite lamellae lying in the (100) plane of the clinopyroxene host.

The silicate mineral asbestos is categorized into two main groups based on fiber structure: serpentine asbestos (chrysotile) and amphibole asbestos (crocidolite, amosite, anthophyllite, tremolite, and actinolite). Chrysotile is used in more than 2 000 applications and is especially prevalent in the construction industry. Although its use is banned or restricted in more than 52 countries, an estimated 107 000 workers die from asbestos exposure each year, and approximately 125 million workers continue to be exposed. Furthermore, ambient exposures persist to which the public is exposed, globally. Today, the primary controversies regarding the use of asbestos are the potencies of different types of asbestos, as opposed whether or not asbestos causes morbidity and mortality. The asbestos industry has promoted and funded research based on selected literature, ignoring both clinical and scientific knowledge. In this piece, we highlight a prominent example of a conflicted publication that sought to undermine the World Health Organization (WHO) campaign to stop the use of all forms of asbestos, including chrysotile asbestos. Independent and rigorous scientific data provide sufficient evidence that chrysotile asbestos, like other forms of asbestos, is a cause of asbestos-related morbidity and premature mortality.

Magnetite is a common mineral found in a wide range of mineral deposits and in different geological environments. The study of surface textures and morphology of magnetite can provide information that is useful to 1) discriminate different types of magnetite such as that attributed to magmatic, metamorphic and supergene environments, 2) identify host bedrocks, 3) sediment provenance, and 4) recognize chemical and mechanical processes affecting grains during erosion, transport, and after deposition in sedimentary environments. In this study, magnetite grains from the Izok Lake volcanogenic massive sulfide deposit (Nunavut, Canada) and from till covering the area have been investigated using scanning electron microscopy, mineral liberation analysis, and optical microscopy to document their mineral associations, surface textures, grain shape and size distribution. Evidences such as 1) contact relations between magnetite and sphalerite, 2) sphalerite and chalcopyrite inclusions in magnetite, and 3) intergrowths of magnetite with actinolite and gahnite suggest that in Izok Lake deposit and related gahnite-rich stringer zone, magnetite formed by replacement of sulfide minerals during regional, upper greenschist to amphibolite facies metamorphism. Magnetite from iron formation also formed as a result of oxidation–dissolution of almandine, or breakdown of Fe-bearing minerals during metamorphism. Euhedral, fine-grained magmatic magnetite in association with ilmenite, plagioclase and hornblende was identified in bedrock gabbro. Magnetite overgrowths on the surface of existing magnetite and other metamorphic minerals fingerprinted the supergene processes affecting bedrocks and sediments after metamorphism. Magnetite in till around the Izok Lake deposit is mostly imprinted by mechanical microtextures such as crescentic gouges, deep grooves, arc-shaped steps, and troughs that are diagnostic of transportation by thick continental ice sheets. A small proportion of magnetite grains characterized by V-shaped percussion cracks also indicate transportation by fluvial and/or glaciofluvial environments. Shape, grain-size distribution, and mineral association of magnetite in till suggest that in vicinity of the Izok Lake deposit, till has mainly been fed by the deposit and related alteration zones, though, a high proportion of grains have been derived from iron formations, bedrock gabbro, and Mackenzie dikes.

The world-class Sangan iron skarn deposit with a proven reserve of > 1000 Mt iron ore @ 53% Fe, is located in the Khaf-Kashmar-Bardaskan Volcano-Plutonic Metallogenic Belt (KKB-VPMB) of northeastern Iran along the E–W trending regional Doruneh Fault, north of the Lut Block. Skarn mineralization occurs at the contact of the 39.1 ± 0.6 Ma to 38.3 ± 0.5 Ma Middle Eocene syenite to syenogranite porphyry source pluton with Cretaceous carbonate rocks. The source pluton is part of an I-type, calcalkaline granitoid series with potassium to shoshonitic affinity, metaluminous to slightly peraluminous character. The granitoids are enriched in LILE (Cs, Rb, Ba, K, Th, and U) and LREE (La and Ce), are depleted in HFSE (Nb, Y, Ta, and Ti), HREE (Yb and Lu) and Eu, which together with the low Sr (96 to 362 ppm) and (La/Yb) N contents suggest a metasomatized, slab-derived mantel source within the Cenozoic volcanoplutonic continental arc of northeaster Iran. The location of the skarn orebodies is controlled by the regional E–W Doruneh Fault structure, and the spatial distribution and the two, calcic and magnesian, skarns is controlled by the composition of the carbonate protolith that consists of limestone in the west and dolomite in the east. The chemistry of the skarn minerals reflects the composition of the protoliths. The western skarn is dominated by ca-rich calcsilicates that consist of prograde Ca-rich garnet (Adr 50–97 Grs 0–45 Sps-Alm 2 -7 ), Ca–Fe-rich pyroxene (Hd 75.6 Di 20 Jo 4.5 ), K–Cl–F-bearing Fe–Ca-rich amphibole ferrohastingsite (Fe 4.4 Ca 2 Mg 0.5 K 0.4 Na 0.3 )(Si 6.5 Al 1.8 O 22 )(Cl, F, OH) 2 in endoskarns, and retrograde ferroactinolite (Fe 4.2 Ca 2 MgMn 0.04 Na 0.1 K 0.06 )(Si 7.8 Al 0.2 O 22 )(F, Cl, OH) 2 and Fe-rich chlorite ripidolite (Fe 4.3 Mg 1.1 Ca 0.06 Mn 0.01 )(Al 2.8 Si 3 O 10 )(OH) 8 in the exoskarns. Wollasonite, plagioclase, and K-feldspar have been additionally formed together with ferrohastingsite in the endoskarns. The eastern magnesian skarn is typically phlogopite-rich (K 0.9 Mg 2.7 Fe 0.2 Na 0.02 )(Si 2.9 Al 1.2 O 10 ) (OH, F) 2 , and consists of prograde forsterite (Fo 97.0 Fa 2.7 ), diopsidic pyroxene (Hd 0.2 Di 0.88 ), and retrograde Mg-rich actinolite, Mg-rich chlorite clinochlore (Mg 4.5 Fe 0.1 K 0.05 )(Al 1.8 Si 2.7 O 10 )(OH) 8 , serpentine and talc. Iron mineralization overprints the calcsilicate skarns in both the western and the eastern skarns and is magnesian in the eastern orebodies (3.65 wt.% MgO). The iron ore consists of a number of high grade, replacement, and magnetite orebodies with minor amounts of pyrrhotite, chalcopyrite, and pyrite indicating a large scale metasomatic transfer of iron bearing fluids during Middle Eocene magmatic activity at the KKB-VPMB.

Titanite (sphene, CaTiSiO5) is sensitive to changes in temperature, oxygen and water fugacity, and fluid composition. In order to understand formation processes and the nature of hydrothermal fluids, various types of titanite from Cu ores at the Baogutu reduced porphyry Cu deposit were chosen for detailed study. Magmatic titanite is associated with biotite, plagioclase and K-feldspar, whereas hydrothermal titanite occurs with K-feldspar, chlorite, actinolite and calcite. The formation of hydrothermal titanite was related to hydration of igneous minerals under high fH2O, whereas the widespread replacement of ilmenite by titanite (without magnetite) indicates a relatively low oxygen fugacity. Magmatic titanite has low Al, high Fe, Y, Sn, Zr, Nb and REE contents, relative to hydrothermal titanite. On the basis of the Zr-in-titanite and Al-in-chlorite geothermometers, formation temperatures for magmatic and hydrothermal titanite are estimated to be 687–739 °C and 250–670 °C, respectively. The gradual decrease in REE, Y and Sn contents from magmatic to late hydrothermal titanite was probably caused by precipitation of REE-bearing minerals. Magmatic and hydrothermal titanites have similar chondrite-normalized REE patterns with negative Eu anomalies and relatively flat HREE. Randomly selected titanites have Nd isotopic compositions similar to the host rocks. Thus, both magmatic and hydrothermal titanite are believed to have been predominantly derived from a mantle source.

In this paper, we present U–Pb ages and trace element compositions of titanite from the Ruanjiawan W–Cu–Mo skarn deposit in the Daye district, eastern China to constrain the magmatic and hydrothermal history in this deposit and provide a better understanding of the U–Pb geochronology and trace element geochemistry of titanite that have been subjected to post-crystallization hydrothermal alteration. Titanite from the mineralized skarn, the ore-related quartz diorite stock, and a diabase dike intruding this stock were analyzed using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Titanite grains from the quartz diorite and diabase dike typically coexist with hydrothermal minerals such as epidote, sericite, chlorite, pyrite, and calcite, and display irregular or patchy zoning. These grains have low LREE/HREE and high Th/U and Lu/Hf ratios, coupled with negative Eu and positive Ce anomalies. The textural and compositional data indicate that titanite from the quartz diorite has been overprinted by hydrothermal fluids after being crystallized from magmas. Titanite grains from the mineralized skarn are texturally equilibrated with retrograde skarn minerals including actinolite, quartz, calcite, and epidote, demonstrating that these grains were formed directly from hydrothermal fluids responsible for the mineralization. Compared to the varieties from the quartz diorite stock and diabase dike, titanite grains from the mineralized skarn have much lower REE contents and LREE/HREE, Th/U, and Lu/Hf ratios. They have a weighted mean 206 Pb/ 238 U age of 142 ± 2 Ma (MSWD = 0.7, 2σ), in agreement with a zircon U–Pb age of 144 ± 1 Ma (MSWD = 0.3, 2σ) of the quartz diorite and thus interpreted as formation age of the Ruanjiawan W–Cu–Mo deposit. Titanite grains from the ore-related quartz diorite have a concordant U–Pb age of 132 ± 2 Ma (MSWD = 0.5, 2σ), which is 10–12 Ma younger than the zircon U–Pb age of the same sample and thus interpreted as the time of a hydrothermal overprint after their crystallization. This hydrothermal overprint was most likely related to the emplacement of the diabase dike that has a zircon U–Pb age of 133 ± 1 Ma and a titanite U–Pb age of 131 ± 2 Ma. The geochronological results thus reveal two hydrothermal events in the Ruanjiawan deposit: an early one forming the Wu–Cu–Mo ores related to the emplacement of the quartz diorite stock and a later one causing alteration of the quartz diorite and its titanite due to emplacement of diabase dike. It is suggested that titanite is much more susceptible to hydrothermal alteration than zircon. Results from this study also highlight the utilization of trace element compositions in discriminating titanite of magmatic and hydrothermal origins, facilitating a more reasonable interpretation of the titanite U–Pb ages.

Extending approximately 1300 km and located in the Western Kunlun Mountains, the Hetian nephrite belt is the largest nephrite belt in the world and contains approximately 11 major deposits and more than 20 orebodies including the Alamas deposit. Hetian nephrite deposits can be classified as Mg-skarn deposits with Precambrian dolomitic marble host rock and green, green–white and white nephrite zones are distributed gradually in the zone of a granodiorite pluton. The green nephrite is mainly predominately composed of tremolite with generally minor to trace constituents of diopside, grossularitic garnet, actinolite and other minerals. Also green nephrite has higher content of TFe2O3, than green–white and white nephrites have. We subdivided the zircons from the green nephrites into four types, depending on their internal textures, mineral inclusions, and SHRIMP U–Pb ages. Type I zircons are round instead of idiomorphic in shape and lack obvious zoning. Type II and IV zircons have broad, clear oscillatory zoning and are hypidiomorphic or idiomorphic in shape; they contain inclusions of diopside, tremolite, chlorite and calcite. Most Type III zircons are narrow rims ( 0.1), similar REE and trace element patterns, a Ce anomaly (Ce/Ce* > 5), and ΣREE contents of 454 to 922 ppm and 102 to 3182 ppm with averages of 627 ppm and 855 ppm, respectively. The similar geochemical signatures, morphologies, and ages indicate that most zircons (or fragments of zircon) in the nephrite came from the granodiorite and some experience partially recrystallized during skarnization. This is consistent with the field observation that original granodiorite–dolomitic marble boundary is now represented within a nephrite sequence, with the green nephrite close to the granodiorite and the white/white–green nephrites adjoining the dolomitic marble. Typical skarn deposits experience prograde and retrograde metasomatism stages. According to the field observations and petrographic studies, both prograde metasomatism and the early retrograde altered stages are two main stages for the formation of Alamas nephrite deposits. The replacements of coarse-grained tremolite by fine-grained tremolite (nephrite) lead to the formation of nephrite. Based on petrographic studies, the main formation processes of the nephrite are 1) diopside ← dolomite; 2) tremolite (nephrite) ← diopside; and 3) chlorite ← tremolite (nephrite). Thus, the timing of the formation of nephrite is later than that of Mg-skarn.

Metabasite refers to metamorphosed basalts and other mafic igneous rocks (rich in iron and magnesium). When a mafic igneous rock is subjected to new pressure and temperature conditions during metamorphism, these chemical components will rearrange themselves to form new minerals. Metabasites can be found in many metamorphic belts including Sanandaj-Sirjan metamorphic belt of Iran. The study area is a Tanbour metamorphic complex in Eastern of Sirjan city, which is geologically located at the Sanandaj-Sirjan metamorphic belt in Southern Iran. Metabasite in this complex consists of greenschist, epidote amphibolite and amphibolite. Amphibole and plagioclase are the main minerals in the greenschist and amphibolite, and the a secondary mineral in some micaschist seen in the study area. The electron microprobe analysis was done on this mineralization in greenschist, epidote amphibolite and amphibolite, which showed that the amphiboles in greenschist was a member of the calcic group and Actinolite type, and the amphiboles in epidote amphibolite was a member of the calcic group and these amphiboles were tschermakite up to Ferro-Tschermakite + Ferro-Hornblende type. The amphibole in amphibolite is a member of the calcic group and this amphibole is Magnesio-Hornblende type. The plagioclases in the greenschist is pure albite (An 3.29 - 3.6), and in the epidote amphibolite is oligoclase (An 19.5 - 24.2), while in the amphibolites is oligoclase (An 16.9 - 26.6). The estimated P–T conditions are in favor of their metamorphism under epidote amphibolite (550°C and 8 kbar) and amphibolite (611°C - 652° Cand 10.5 kbar) facies.

The South Dehgolan intrusion in the Sanandaj-Sirjan Zone ranges in composition from calc-alkalic monzogabbro to syenite to alkalic granite. This suite is composed mainly of variable proportions of quartz, K-feldspar, plagioclase, biotite, hornblende, and pyroxene. The plagioclase composition varies between albite to labradorite. The biotites are Mg- to Fe-rich in the monzogabbro to granite, respectively. The amphiboles are calcic and the composition varies from magnesiohornblende to actinolite. Clinopyroxene compositions fall in the diopside-augite field. The average calculated near-solidus crystallization temperatures are 774 °C, 655 °C, and 775 °C for the monzogabbro-monzodiorite, syenite, and granite, respectively. Calculated average pressures of emplacement are 1.7, 1.3, and 1.9 kbar for the monzogabbro-monzodiorite, syenite, and granite rocks, respectively, crystallizing at different respective depths of about 6.7, 5.0, and 7.3 km. The interpreted oxygen fugacities in the monzogabbro-monzodiorite and syenite rocks are typical of arc magmas, with oxygen fugacities above the Ni-NiO buffer. Water contents in the monzogabbro-monzodiorite and syenite were calculated to range from 4.7 to 4.4 wt.% and in the granite is 3.8 wt.%. High water and volatile contents in the monzogabbro to syenite may have allowed the magma to reach shallower crustal levels. During the evolution of this magmatic system to higher silica contents, there was an increase in the activity of oxygen and decrease in the temperature and the emplacement depth from the monzogabbro-monzodiorite to syenite rocks; this is consistent with the typical evolution of the granitoid rocks. However, the calculated higher temperature and pressure and low $f$O2 and H2O content in the later granite reflects notable differences in its origin and crystallization conditions. The range in mineral compositions is this intrusive suite is consistent with a relationship to subduction of the Neotethys oceanic crust beneath the Central Iranian microcontinent, although there was a change from calc-alkaline to alkaline magmatism.

In recent years, environmental exposure to naturally occurring asbestos (NOA) has been shown to be a cause of several types of lung disease, which may occur when NOA outcrops are in proximity to residential areas. In this study, we present the results of our investigation of NOA hosted in outcrops of serpentinites in Basilicata region (Southern Italy), which could be potentially harmful to human health. For this purpose, fifteen serpentinite rock samples collected within and near the village of San Severino Lucano were characterized in detail by optical microscope (OM), X-ray powder diffraction (XRPD), thermal analysis (TG/DSC/DTG/DDSC), scanning and transmission electron microscopy combined with energy-dispersive spectrometry, analytical electron microscopy (SEM/EDS and TEM/AEM). Chrysotile and asbestos tremolite or asbestos actinolite were identified in all samples. The NOA in these outcrops could be subject to weathering processes and/or human activities, which generate airborne particles, thus exposing the neighbouring populations to a series of health risks. The size and morphology of NOA are also discussed, regarding the carcinogenic effect that these factors may have on human health. Due to the health risks associated with disturbing NOA-bearing rock, an asbestos exposure control plan must be instituted.

This project developed from studies demonstrating that Libby Amphibole Asbestos (LAA) causes a non-typical set of health outcomes not generally reported for asbestos, including systemic autoimmunity and an unusual and devastating lamellar pleural thickening that progresses to severe pulmonary dysfunction and death. Further, mineral fiber mixtures with some similarities to LAA have recently been discovered in southern Nevada and northwestern Arizona, where the material exists in extensive recreational areas and is present in yards, roads, parking lots and school yards. The objective was to compare the health outcomes in mice exposed to either LAA or the fibrous amphiboles collected in Arizona at the Lake Mead National Recreational Area at very low doses to represent environmental exposures. In this study, the fibrous amphibole asbestos sample from Arizona (AzA) is composed of winchite (69%), actinolite (22%), and non-amphibole minerals (9%) and has a mean aspect ratio of 16.7±0.9. Fibrous amphibole asbestos from Libby (LAA) is composed of winchite (70%), richterite (9%), tremolite (5%), and non-amphibole minerals (16%) with a mean aspect ratio of 8.4±0.7. C57BL/6 mice were exposed by oropharyngeal aspiration to fiber suspensions at a very low dose of 3μg/mouse. After seven months, both LAA- and AzA-exposed mice had indices of chronic immune dysfunction related to a TH17 cytokine profile, with B cell activation, autoantibody production and proteinuria, suggesting kidney involvement. In addition, both exposures led to significant lung and pleural fibrosis. These data suggest that there is risk of pulmonary disease and autoimmune outcomes with environmental exposure to amphibole asbestos, and that this is not limited to Libby, Montana.

The Choghart magnetite-apatite deposit situated in the Bafq district, Central Iran, has been scrutinized for rare earth elements (REEs) by precise geochemical investigation. The Central Iran is a susceptible area of rare earth elements. One of the Choghart’s prominent points is the existence of hydrothermal zones which made prediction of REEs occurrence within the deposit possible. Choghart is placed within felsic volcanic tuffs, rhyolitic rocks, and volcanic sedimentary sections belonging to the lower Cambrian. Abundance and distribution pattern of REEs in Choghart iron deposits reveal a part of deposit formation and its mineralogical modifications. Petrography and mineralogy of the ore body demonstrated two main types of alterations (sodic and calcic) associated with iron ore mineralization in Choghart deposit. The main ore includes a large quantity of massive magnetite in the lower part of Choghart deposit. The minor mineralization involves apatite, pyrite, alkaline amphibole, especially actinolite and tremolite, calcite, talc, quart, monazite, and bastnasite. Geochemical sampling from north–northeast (N-NE) side of the mine denotes the presence of these elements in hydrothermal zones. Statistical populations of the area were categorized by fractal geometry into four main differentiations: host rock type (albitofyre), iron, metasomatose, phosphate zones, and a subset of the phosphate zone which is named high iron high phosphate type. REEs like lanthanum, neodymium, yttrium, and niobium constitute the most quantity of Choghart. Deposit characteristics demonstrate its similarity to Kiruna type. The significant feature of iron oxide-apatite deposits of Kiruna ore type is the existence of monazite inclusions within apatite. These inclusions were also observed within apatite type I and II of Choghart mineralization. Moreover, REEs geochemistry in Choghart deposit was identified by investigation on geochemical data analyses. The analysis represents negative Eu anomaly and further enrichment of light REEs compared to the heavy ones. Chondrite normalized REEs patterns are defined by negative anomalies of Eu, which is the main characteristic of Kiruna ore type. The results showed that REEs concentration in phosphate zone, as a high absorption of REEs, is much higher than metsomatose, albitofyre, and iron zones. REEs distribution in N-NE side of the mine indicated that the contact of iron ore with tailings in N-NW side of the mine leads REEs to be enriched nearly 1% , as well as that of NE with high contents of REEs 1.5% ), which is very significant.

The Maronia Cu-Mo &plusmn, Re &plusmn, Au deposit is spatially related to a microgranite porphyry that intruded an Oligocene monzonite along the Mesozoic Circum-Rhodope belt in Thrace, NE Greece. The magmatic rocks and associated metallic mineralization show plastic and cataclastic features at the south-eastern margin of the deposit that implies emplacement at the ductile-brittle transition, adjacent to a shear zone at the footwall of the Maronia detachment fault. The conversion from ductile to brittle deformation caused a rapid upward magmatic fluid flow and increased the volume of water that interacted with the host rocks through high permeable zones, which produced extensive zones of potassic and sodic-calcic alteration. Potassic alteration is characterized by secondary biotite + K-feldspar (orthoclase) + magnetite + rutile + quartz &plusmn, apatite and commonly contains sulfides (pyrite, chalcopyrite, pyrrhotite). Sodic-calcic alteration consists of actinolite + sodic-calcic plagioclase (albite/oligoclase/andesine) + titanite + magnetite + chlorite + quartz &plusmn, calcite &plusmn, epidote-allanite. The high-oxidation state of the magmas and the hydrothermal fluid circulation were responsible for the metal and sulfur enrichments of the aqueous fluid phase, an increase in O2 gas content, the breakdown of the magmatic silicates and the production of the extensive potassic and sodic-calcic alterations. Brittle deformation also promoted the rapid upward fluid flow and caused interactions with the surrounding host rocks along the high temperature M-, EB-, A- and B-type veins.

The Anjerd Cu skarn deposit is located 40 km north of Ahar, NW Iran, which comprises three different stages of skarn–type mineralization and metasomatic alteration including (i) prograde, (ii) early retrograde and (iii) late retrograde. Prograde stage is identified by garnet as andradite–grossularite and diopsidic pyroxene crystallization, whereas retrograde stage overprinted the prograde skarn and is predominantly composed of tremolite, actinolite, quartz, epidote and chlorite. Metasomatic alteration started with generation and evolution of the mineralizing fluids in the Shayvar batholith, followed by the fluids ascending into fractures of the skarn in the metamorphic zone. Subsequently, retrograde alteration continued to the end of the skarnification process. Based on mineral chemistry studies, garnet is dominated by andradite (27–78 mol. %) and grossularite (20–67 mol. %) compositions and pyroxenes by diopside (65–98 mol. %) and hedenbergite (2–34 mol. %) compositions. Based on detailed petrography studies, three types of fluid inclusions were recognized including two–phase liquid–rich (LV), vapor–rich (VL), and three–phase (LVS) inclusions. The characteristic of the mineralizing fluids during the skarn evolution was changed significantly from early retrograde stage with (i) high temperature (up to 460 °C) and high salinity (up to 39 wt% NaCl equiv.), through late retrograde stage with (ii) moderate to high temperature (334 to 446 °C) and low salinity (0.3 to 0.8 wt% NaCl equiv.), (iii) low to moderate temperature (158 to 362 °C) and moderate salinity (1.7 to 12.3 wt% NaCl equiv.), suggesting that high–temperature and moderately saline fluids are indicative of a magmatic source within the minerals belonging to the prograde skarn, while the fluids with lower temperature and low to moderate salinity indicating a meteoric source for the retrograde skarn assemblage. The δ18O values for prograde garnet and magnetite vary from ∑0 to 8.2‰, whereas δ18O and δD values for retrograde calc–silicates in equilibrium with fluid including epidote range from 6.7 to 9.2‰ and −10.2 to −31.4 and for chlorite range from 1.9 to 2.7‰ and −37.5 to −48.1‰, respectively, pointing out that mixing of magmatic fluids with meteoric water in the retrograde alteration. Moreover, the δ34S values of pyrite and chalcopyrite (−3.6 and +4.9‰), suggesting a magmatic source for sulfur which was largely responsible for the mineralization in the Anjerd deposit.

The paper presents the results of studies of diopside rocks collected from the“Aldanslyuda” mining and processing plant dumps as aggregates for the production of heavy-weight and sand concretes. The presented data shows that the average chemical composition of these diopside rocks is on: SiO2 - 46.38%, CaO2 - 16.53% and MgO2 - 15.30%. The low content of magnesium and calcium dioxides indicates that even when the specific surface area is incriesed to 5000 cm2/g and above, the diopside will only work as a filler. The mineralogical composition of rocks is represented by diopside, actinolite and pargasite. It was found that it is more efficient to use diopside rocks as an aggregate to produce concrete. By testing the crushed stone of a mixture of a fraction from 5 to 20 mm and sand from sifting of crushing solid stone, it was shown that these diopside rocks are suitable as aggregates to produce heavy-weight and sand concretes of strength class up to 60 MPa. To consider the possibility of using them to obtain high-strength concretes, it is necessary to conduct more experimantal research

Near-Infrared spectroscopy (NIR) is a useful tool for direct and on-site identification of rock mineralogy in spite of the difficulties arising in spectral evaluation, due to limited availability of spectral libraries at the time. Especially in the field, a functional methodology for the identification and evaluation if possible, of the geologic materials, is of interest to many researchers. However, several different parameters (such as grain size, color, mineralogy, texture, water content etc.) can affect the spectroscopic properties of the samples resulting in spectral variability. The subject of the present work focuses in various lithotypes (monzodiorite, diorite, altered diorite, actinolite schist, cataclasite, slate) from Kos Island, Aegean Sea, in Greece, all bearing hydrous minerals in various amounts. The evaluation of the results obtained from NIR spectroscopy offered important qualitative information about the mineralogy of the lithotypes examined. The important asset of the method is that no sample preparation was necessary. From the reflectance spectra, the NIR-active minerals that were identified include chlorite, micas, amphiboles and epidotes. Petrographic and mineralogic analyses were also employed in order to confirm the NIR results and provide more detailed information about the mineralogy of the samples, the grain size and the orientation of the minerals. Correlation of wavelength positions at ~1400 nm with loss on ignition (LOI) values led us to relate the various lithotypes in terms of their petrological affinities. NIR spectroscopy was proved to be a useful tool, especially for the mineralogic identification of rocks underwent low- to medium grade metamorphism, from greenschist to amphibolite facies.

Metamorphosed mafic-ultramafic rocks from the central portion of the Rio Grande do Norte Domain of the Borborema Province (BP), northeastern Brazil, have been studied here with the objective of gaining a better understanding of the Archean evolution of this portion of the BP. The study area is underlain by gneissic-migmatitic basement as well as biotite schists and paragneisses of the Serido and Jucurutu formations of the Serido Group. The mafic-ultramafic rocks (serpentinites, amphibole-schists and amphibolites) occur in lenses for 30 km along strike following the NNE regional foliation. The serpentinites occur as relatively small exposures of elongated bodies within paragneisses of the Jucurutu Formation and orthogneisses of the Caico Complex. They consist of xenoblastic serpentine (75–99%) that has replaced the primary ferromagnesian minerals of the protolith. The amphibole schists and amphibolites are whitish gray to green, depending on the dominant mineral phase, tremolite, talc or actinolite. The mafic-ultramafic rocks present high MgO, Ni and Cr2O3 contents and very low TiO2, Na2O and K2O contents, being compositionally similar to mafic-ultramafic rocks from other Archean greenstone belts worldwide. U-Pb (SHRIMP) dating of zircons returned concordia ages of 3526 ± 5 Ma (MSWD = 0.0084) for the serpentinites of the Serra Verde Mine and 3747 ± 12 Ma (MSWD = 9.8) for serpentinites from the Oiticica Mine. The petrographic and geochemical characteristics as well as the Eo to Paleoarchean ages of the studied rocks are significant as the basement of this portion of the BP is dominantly of Paleoproterozoic age. It is envisaged that these results will lead to further debate and a greater understanding of crustal evolution of the BP. We propose that these mafic-ultramafic rocks are part of a dismembered Archean greenstone belt, which present the oldest ages so far determined for the South American Platform.

Trace element concentrations, particularly rare earth elements and yttrium (REY) in feldspars and accessory minerals, have been determined in a suite of albitized igneous, metasedimentary and metasomatite rocks from the Moonta-Wallaroo district, Olympic Cu–Au Province, South Australia. Results show that changes in REY-fractionation trends and concentrations in feldspars and common accessories are associated with key textures in albite-bearing associations from different lithologies. In granitic rocks, pseudomorphic replacement of pre-existing feldspars is typified by porous albite with cleavage-oriented intergrowths of sericite and pore-attached hematite. These observations are comparable with albitization features of granitic terranes elsewhere. A mineral association (albite-sericite ± chlorite), similar to that from granitoids, is observed as pervasive spots in limestone, inferring prograde skarnoid reactions at low fluid/rock ratio in an impure carbonate. In metasedimentary and metasomatite rocks with comparable Na2O content (~ 5–6 wt.%), fine-grained granoblastic albite suggests growth under high fluid/rock ratios irrespective of lithology. In such cases, albite with the highest REY content (ΣREY ~ 200 ppm) accounts for the entire REY budget, e.g., in albite–biotite-schist with the lowest abundance of accessory minerals. Nanoscale investigation confirms this albite to be a REY carrier (elements incorporated within the crystal lattice); no pore-attached inclusions are observed. In contrast, albite with the lowest REY-concentration (~ 14 ppm) is encountered in the metasomatite. In such rocks, recording the highest ΣREY (~ 1000 ppm) in whole-rock, partitioning of REY is favoured among the abundant accessories (titanite, apatite) and calc-silicates (actinolite, clinozoisite) rather than albite. Comparable low-REY albite is also found in granitoid-derived albitite (Na2O ~ 5 wt.%), in which abundant accessories and discrete REY-minerals formed during albitization account for the high ΣREY content (~ 700 ppm) in whole rock. The role of coupled dissolution–reprecipitation reactions (CDRR) is critical for REY (re)distribution within albitized igneous rocks, where REY-release from early magmatic accessories and/or feldspars assists REY-enrichment into late albite. The presence of abundant nanopore-attached inclusions in plagioclase demonstrates the nanoscale nature of CDRR-driven albitization in granitoids, consistent with published experimental work on altered granites. Such porosity offers sites for REY entrapment seen within discrete REY-minerals in new-formed K-feldspar. Similarly, release and uptake of REY, concurrent with albitization, is seen in formation of coarser REY-minerals (xenotime, bastnasite, synchysite) during CDRR-driven replacement of accessory Fe–Ti-oxides by symplectites of chlorite and hematite. Based on the differences identified between the albitization pathways in igneous and metasedimentary rocks, we discuss how albitization proceeds via a series of complex fluid–mineral reactions, each involving the redistribution, accumulation and retention of REY. These reactions are critical for defining the endowment and deportment of REY in rocks that have undergone sodic alteration. Contrary to previous models, albitization appears controlled by pH rather than redox conditions. Despite regional differences in local geological environment and alteration style across the Olympic Cu–Au Province, albitization, the initiation of hydrothermal alteration, is a pre-requisite stage for REY-enrichment in Iron-Oxide–Copper–Gold (IOCG) systems. REY distribution patterns in feldspars may thus have value in mineral exploration as criteria enabling alteration associated with mineralization to be distinguished from the regional background. Strong albitization without superposition of later potassic alteration may not, however, be automatically linked to the formation of giant IOCG deposits. Albitization enhances rock permeability and in a strongly faulted structural environment without a suitable trap, hydrothermal fluids may be more readily lost from the system.

The green Hetian nephrite, which has delicate textures, spinach-like green and less cracks, contains three types of aggregates: primary nephrite, placer nephrite and Gobi nephrite. The deposits were located in the south part of the Tarim Basin, Xinjiang, China. In the orebodies of the deposits, primary nephrites occurr as veins or lenses along faults or fissures of adjacent ultramafic rocks. Samples with fine-grained and felted cohesive textures were collected from Hetian-Yutian County, Xinjiang Uyghur Autonomous Region, its mineralogical characteristics, H-O isotopic characteristics and forming mechanism have been discussed by means of SEM, EPMA, XRD, IR spectrum, Raman spectrum, DTA and TG study, and H-O isotope study. Microscopic observation and SEM show that green nephrite has interlocking-felted cryptocrystalline blastic texture with fine topography and high compactness. Tremolite, as a main mineral composition of the green nephrite, has high amounts of Si, Ca, and Mg; it turns into actinolite with the help of increasingly large amount of Fe. XRD, IR spectrum and Raman spectrum identified the occurrence of accessory minerals of chromite, chlorite, serpentine, clinopyroxene and apatite. DTA study demonstrates that the structure of tremolite was destroyed at 900 – 1100°C, while TG study demonstrates the tremolite has such little water that it lost only 0.89 – 1.33% of its weight when heated to 900 – 1100°C. The petrogenesis of green Hetian nephrite deposits are implied to be a result of metasomatic alteration of ultramafic-mafic rocks, and the black, spot-like chromite implies ultramafic-mafic rocks. The analysis of H-O isotope study indicates that the ore-forming hydrothermal fluids of Gobi nephrites are primary magmatic water, but details of hydrothermal fluids of primary and placer nephrites are still remained unknown and needed to be investigated furthermore.

Department of Earth and Environmental Sciences, Chonnam National University, Gwangju 500-757, KoreaNaturally occurring asbestos (NOA) occurs in rocks and soils as a result of natural weathering and human activi-ties. The asbestos have been associated with ultramafic and mafic rocks, and carbonate rock. The previous studieson NOA were mainly limited to ultramafic and mafic rock-hosted asbestos in Korea. But, studies on carbonate-hosted asbestos are relatively rare. Therefore, the purposes of this study were to investigate mineralogical character-istics of carbonate-hosted and metapelite-hosted NOA and to examine genesis of NOA occurred in the both rocks.The study area was Daerori, Seosan, Chungnam Province, Korea. The major rock formation consisted of limestoneand schist which have been known to contain asbestos. Sampling was performed at outcrop which contained car-bonate rock showing acicular asbestos crystals as well as pegmatitic intrusion that contacted with carbonate rock.PLM, XRD, EPMA, and EDS analyses were used to characterize mineral assemblages, mineralogical characteris-tics, and crystal habits of amphiboles and other minerals. BSEM images were also used to examine the genesis ofasbestos minerals. The amphibole group was observed in all of the carbonate rocks, and actinolite and tremolitewere identified in all rocks. These mineral habits were mainly micro-acicular crystals or secondary asbestiform min-erals on the surface of non-asbestiform minerals appearing split end of columnar crystals produced by weathering.BSEM images showed residual textures of samples. The residual textures of carbonate rocks showed dolomite-trem-olite-diopside mineral assemblages that formed during prograde metasomatism stage. Some carbonate rock alsoshowed diopside-tremolite-talc mineral assemblages which were formed during retrograde metasomatism stage, asthe residual textures. In result the presence of asbestos actinolite-tremolite in the carbonate rocks were confirmed inthe areas where actinolite-tremolite asbestos was influenced by low temperature hydrothermal solution during meta-somatism stage. These asbestos minerals showed the acicular asbestiform minerals, but even non-asbestiform miner-als, a bundle or columnar shape, could transform to asbestiform minerals as potential NOA by weathering becausethe end of columnar shape of non-asbestiform minerals appeared as multiple acicular shaped fibers.

The Blockspruit fluorite prospect, located in North West State of the Republic of South Africa, occurs within an actinolite rock zone that was emplaced into the Kenkelbos-type granite of Proterozoic age. There are a large number of termite mounds in the prospect. For geochemical prospecting for rare earth elements (REEs), in total, 200 samples of termite mound material were collected from actinolite rock and granite zones in the prospect. Geochemical analyses of these termite mound materials were conducted by two methods: portable X-ray fluorescence (XRF) spectrometry and inductively coupled plasma-mass spectrometry (ICP-MS). Comparison of the two methods broadly indicates positive correlations of REEs (La, Ce, Pr, Nd, and Y), in particular Y and La having a strong correlation. As the result of modal abundance analyses, the actinolite rock at surface mainly consists of ferro-actinolite (89.89 wt%) and includes xenotime (0.26 wt%) and monazite (0.21 wt%) grains as REE minerals. Termite mound materials from actinolite rock also contain xenotime (0.27 wt%) and monazite (0.41 wt%) grains. In addition, termite mound materials from the actinolite rock zone have high hematite and Fe silicate contents compared to those from granite zone. These relationships suggest that REE minerals in termite mound materials originate form actinolite rock. Geochemical anomaly maps of Y, La, and Fe concentrations drawn based on the result of the portable XRF analyses show that high concentrations of these elements trend from SW to NE which broadly correspond to occurrences of actinolite body. These results indicate that termite mounds are an effective tool for REE geochemical prospection in the study area for both light REEs and Y, but a more detailed survey is required to establish the distribution of the actinolite rock body.

In contrast to Nordic countries, talc-rich rocks (massive and schistose talc-bearing rocks—talcite, magnesite-talc schists, chlorite-talc schists, and/or chlorite-actinolite-talc schists often loosely classified as soapstone) represented practically an unknown natural building and sculptural stone in the Czech Republic. This extraordinary material was quarried and used in the only region of the Czech Republic where Sobotin amphibolite massif (Sumperk district, northern Moravia) outcrops. Metamorphosed basic igneous rocks contain small lenses of soapstone that were exploited in the past and used not only for refractory purposes but also as a construction and sculptural material.Occurrences of ‘Sobotin’ soapstone show distinct zone macrofabric marked by the occurrence of massive soapstone in the core that gradually changes to talc-dominant schists, later to actinolite/tremolite-rich schists and finally to chlorite schists at the contact with surrounding amphibolites. The most typical ‘Sobotin’ soapstone exhibits high density (up to 2,900 kg m−3), low water uptake (maximum 0.68 wt %), favorable dynamic elastic properties (P-wave velocity 5,340–5,840 m s−1, S-wave velocity 2,900–3,300 m s−1), and mechanical properties (tensile splitting strength 5.2–6.9 MPa, uniaxial compressive strength 17.5–24.1 MPa). ‘Sobotin’ soapstone is relatively resistant to weathering action although schistose varieties show typical delamination when exposed to frequent freeze/thaw cycling in harsh mountainous environment. Field survey of monuments, architectural and building artefacts made from ‘Sobotin’ soapstone contributed to our knowledge on duration of exploitation of ‘Sobotin’ soapstone that was for sure utilised from the second half of seventeen century till the beginning of the twenty century. The most characteristic feature of ‘Sobotin’ soapstone is its strict local use on the territory of about 20 villages surrounding previously exploited soapstone lenses.