26 results on '"Stephen J. Barnes"'
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2. Chromitite layers indicate the existence of large, long-lived, and entirely molten magma chambers
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Rais Latypov, Sofya Chistyakova, Stephen J. Barnes, Belinda Godel, Gary W. Delaney, Paul W. Cleary, Viktor J. Radermacher, Ian Campbell, and Kudakwashe Jakata
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Medicine ,Science - Abstract
Abstract The classical paradigm of the ‘big magma tank’ chambers in which the melt differentiates, is replenished, and occasionally feeds the overlying volcanos has recently been challenged on various grounds. An alternative school of thought is that such large, long-lived and largely molten magma chambers are transient to non-existent in Earth’s history. Our study of stratiform chromitites in the Bushveld Complex—the largest magmatic body in the Earth’s continental crust—tells, however, a different story. Several chromitites in this complex occur as layers up to 2 m in thickness and more than 400 kms in lateral extent, implying that chromitite-forming events were chamber-wide phenomena. Field relations and microtextural data, specifically the relationship of 3D coordination number, porosity and grain size, indicate that the chromitites grew as a 3D framework of touching chromite grains directly at the chamber floor from a basaltic melt saturated in chromite only. Mass-balance estimates imply that a few km thick column of this melt is required to form each of these chromitite layers. Therefore, an enormous volume of melt appears to have been involved in the generation of all the Bushveld chromitite layers, with half of this melt being expelled from the magma chamber. We suggest that the existence of thick and laterally extensive chromitite layers in the Bushveld and other layered intrusions supports the classical paradigm of big, albeit rare, ‘magma tank’ chambers.
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- 2022
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3. Time scales and length scales in magma flow pathways and the origin of magmatic Ni–Cu–PGE ore deposits
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Stephen J. Barnes and Jesse C. Robertson
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Geology ,QE1-996.5 - Abstract
Ore forming processes involve the redistribution of heat, mass and momentum by a wide range of processes operating at different time and length scales. The fastest process at any given length scale tends to be the dominant control. Applying this principle to the array of physical processes that operate within magma flow pathways leads to some key insights into the origins of magmatic Ni–Cu–PGE sulfide ore deposits. A high proportion of mineralised systems, including those in the super-giant Noril'sk-Talnakh camp, are formed in small conduit intrusions where assimilation of country rock has played a major role. Evidence of this process is reflected in the common association of sulfides with vari-textured contaminated host rocks containing xenoliths in varying stages of assimilation. Direct incorporation of S-bearing country rock xenoliths is likely to be the dominant mechanism for generating sulfide liquids in this setting. However, the processes of melting or dissolving these xenoliths is relatively slow compared with magma flow rates and, depending on xenolith lithology and the composition of the carrier magma, slow compared with settling and accumulation rates. Chemical equilibration between sulfide droplets and silicate magma is slower still, as is the process of dissolving sulfide liquid into initially undersaturated silicate magmas. Much of the transport and deposition of sulfide in the carrier magmas may occur while sulfide is still incorporated in the xenoliths, accounting for the common association of magmatic sulfide-matrix ore breccias and contaminated “taxitic” host rocks. Effective upgrading of so-formed sulfide liquids would require repetitive recycling by processes such as re-entrainment, back flow or gravity flow operating over the lifetime of the magma transport system as a whole. In contrast to mafic-hosted systems, komatiite-hosted ores only rarely show an association with externally-derived xenoliths, an observation which is partially due to the predominant formation of ores in lava flows rather than deep-seated intrusions, but also to the much shorter timescales of key component systems in hotter, less viscous magmas. Nonetheless, multiple cycles of deposition and entrainment are necessary to account for the metal contents of komatiite-hosted sulfides. More generally, the time and length scale approach introduced here may be of value in understanding other igneous processes as well as non-magmatic mineral systems. Keywords: Magmatic ore deposits, Assimilation, Intrusions, Nickel, Norilsk, Komatiites
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- 2019
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4. Zoned Pyroxenes as Prospectivity Indicators for Magmatic Ni-Cu Sulfide Mineralization
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Louise Schoneveld, Stephen J. Barnes, Hannu V. Makkonen, Margaux Le Vaillant, David J. Paterson, Valentina Taranovic, Kai-Yuan Wang, and Ya-Jing Mao
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clinopyroxene ,orthopyroxene ,chromium ,zoning ,XRF ,sulfide ,Science - Abstract
Small intrusions dominated by olivine- and pyroxene-rich cumulates are well known to be favorable hosts to magmatic Ni-Cu-(Platinum Group Element—PGE) sulfide mineralization. Such intrusions are common in a variety of settings around the world, but only a very small proportion contain economically exploitable sulfides; these tend to be of conduit or chonolith style. If prospectivity could be discriminated from sparse sampling at early exploration stages, then the discovery rate for deposits of this type could be improved. To this end, a number of pyroxene-bearing samples from small intrusions containing magmatic sulfide deposits have been investigated including the Noril'sk-Talnakh camp in Siberia, the Kotalahti nickel belt in Finland, Ntaka Hill in Tanzania, Nova-Bollinger in the Albany-Fraser Orogen of Australia, Savannah in the Halls Creek Orogen of Australia, Jinchuan in central China, Xiarihamu in Tibet and Huangshanxi in the east Tianshan Ni province of NW China. To compare, samples from unmineralized intrusions in four of these regions were also investigated along with four mafic intrusions from other localities that are not associated with any known economic sulfide mineralization. Using fine-scale (
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- 2020
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5. Crystallization of spinel from coexisting silicate and sulfide immiscible liquids: An equilibrium case with postcumulus reactions
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Ya-Jing Mao, Stephen J. Barnes, Louise Schoneveld, Belinda Godel, Morgan Williams, Dongmei Tang, Zhen Kang, and Ke-Zhang Qin
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Geophysics ,Geochemistry and Petrology - Abstract
Spinel minerals occur as inclusions in both silicates and sulfides in the Kalatongke magmatic Ni-Cu deposit in NW. China, showing textural and compositional variations. The spinel enclosed in olivine and other silicates (orthopyroxene, clinopyroxene, and hornblende) is predominantly Cr-magnetite with minor Cr-spinel, having wide variations in MgO (0.1–8.0 wt%), Al2O3 (1–25 wt%), Cr2O3 (3–20 wt%), and TiO2 (0.5–6.2 wt%) contents. Such continuous variations suggest that Cr-magnetite in silicates was crystallized from residual melts and experienced extensive reaction with trapped liquid undergoing a typical tholeiitic trend of increasing Fe and Ti concentrations. Crystals of Cr-magnetite enclosed in disseminated sulfides have similar Mg, Al, Cr, Ti, V, Sc, Ga, Mo, Zr, and Nb concentrations to the Cr-magnetite in silicates. Such compositional similarity, which is explained by the simultaneous equilibrium crystallization of Cr-magnetite from the silicate and sulfide melts, shows that the Kalatongke deposit is a typical example of where the same mineral phase is formed from two coexisting immiscible liquids. However, the Cr-magnetite in disseminated sulfide and that in silicates show distinctly different crystal size distribution patterns, illustrating that the chemical equilibrium was attained despite contrasting growth rates. Nevertheless, the Cr-magnetite in disseminated sulfides shows significantly lower Ni, Co, and Zn contents (median value of 845, 22, and 319 ppm) than that in silicates (median value of 1428, 160, and 1039 ppm). This cannot be the result of sulfide fractionation because there is little compositional variation between Cr-magnetite included in pyrrhotite (early crystallized phase) and that immersed in chalcopyrite (late crystallized phase). Such Ni, Co, and Zn depletions, combined with the relatively constrained Fe/Ni, Fe/Co, and Fe/Zn ratios in those Cr-magnetite, are attributed to postcumulus reactions between Cr-magnetite and sulfide melts. The spinel hosted by massive sulfides is magnetite, which has distinctly different compositional variations and crystal size distribution patterns compared with those of the silicate-hosted Cr-magnetite, although the magnetite in massive ore generally has similar contents in some lithophile elements (Zr, Ta, Mo, Sn, Mn) to the silicate-hosted Cr-magnetite. This could be taken as evidence for a mixture of early accumulated sulfide pools with a component of drained sulfide from the cumulates above. This study shows a detailed textural and compositional investigation of spinel is useful to decode the sulfide evolution processes during the formation of magmatic Ni-Cu deposits and highlights that equilibrium crystallization and postcumulus reactions play critical roles in controlling the spinel/magnetite composition.
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- 2023
6. Petrogenesis of thick, high-grade PGE mineralisation in the Flatreef, northern Bushveld Complex
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Wolfgang D. Maier, Stephen J. Barnes, Belinda M. Godel, Danie Grobler, and William D. Smith
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Geophysics ,Geochemistry and Petrology ,Economic Geology - Abstract
The Flatreef of the northern limb of the Bushveld Complex is a world-class platinum-group element (PGE) deposit representing the down-dip extension of the Platreef. Exploration drilling in the central portion of the project area intersected a particularly thick PGE-mineralised portion of the Flatreef exposed in drill core TMT006 and its two deflections, containing 4.5 ppm PGE (Pt + Pd + Rh + Au) over 90 m and ~ 3.7 ppm PGE over 150 m. Data obtained using whole rock geochemical analysis, field emission scanning electron microscopy, micro X-ray fluorescence and X-ray computed tomography indicate that the PGE are hosted by, or are spatially closely associated with, disseminated sulfides that occur interstitial to the cumulus silicate minerals. PGE grades show a broad, albeit irregular trend of progressive downward decrease, whereas most metal ratios (Cu/Ni, Pt/Rh, Cu/Pd and, to a lesser degree, Pt/Pd) remain broadly constant throughout the 90 m main ore zone. These features are interpreted to reflect two stages of ore formation: (i) hydrodynamic concentration of sulfidic ultramafic crystal mushes and (ii) localised downward percolation of sulfide melt in response to fluidisation of the cumulate mush caused by infiltration of ascending magmatic or crustal fluids. The model is consistent with the close spatial association of the sulfides with interstitial plagioclase as well as accessory phlogopite, quartz, apatite and rutile, whereas cumulus orthopyroxene is largely free of sulfide.
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- 2023
7. Nickel in olivine as an exploration indicator for magmatic Ni-Cu sulfide deposits: A data review and re-evaluation
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Stephen J. Barnes, Zhuo-Sen Yao, Ya-Jing Mao, Ana P. Jesus, Shenghong Yang, Valentina Taranovic, and Wolfgang D. Maier
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Geophysics ,Geochemistry and Petrology - Abstract
Nickel contents of olivine have been widely used as petrogenetic indicators and as fertility indicators for magmatic sulfide potential of mafic-ultramafic intrusions, on the assumption that olivines crystallized from magmas that had equilibrated with sulfide liquid should be relatively depleted in Ni compared with a sulfide-free baseline. This has given rise to a large accumulation of data that is brought together here, along with data on volcanic olivines, to critically evaluate the effectiveness of the approach. We identify multiple sources of variance in Ni content of olivine at a given Fo content, including variability in mantle melt composition due to depth, water content (and possibly source), subsequent fractional crystallization with and without sulfide, recharge and magma mixing, batch equilibration between olivine and sulfide at variable silicate-sulfide ratio (R), and olivine/liquid ratio; and subsequent equilibration during trapped liquid crystallization in orthocumulates. Baselines for Ni in olivine in relation to Fo content are somewhat lower in orogenic belt settings relative to intrusions in continental large igneous provinces (LIPs). This is probably related to differences in initial parent magma compositions, with plume magmas generally forming deeper and at higher temperatures. No clear, universal discrimination is evident in Ni in olivine between ore-bearing, weakly mineralized, and barren intrusions, even when tectonic setting is taken into account. However, sulfide-related signals can be identified at the intrusion scale in many cases. Low-R factor and low-tenor sulfides are associated with low-Ni olivines in several examples, and these cases stand out clearly. Anomalously high-Ni olivines are a feature of some mineralized intrusions, in part due to trapped liquid reaction effects. However, in some cases, this mechanism cannot account for the magnitude of enrichment. In these cases, enrichment may be due to re-entrainment of “primitive” Ni-rich sulfide by a more evolved Fe-rich magma, driving the olivine to become Ni-enriched due to Fe-Ni exchange reaction between sulfide and olivine during transport. An extreme case of this process may account for ultra-Ni enriched olivine at Kevitsa (Finland), but more subtle signals elsewhere could be positive indicators. A lack of clear mineralized/barren distinction in specific groups of related intrusions, e.g., the deposits of NW China or the Kotalahti Belt in Finland, may well be due to “false negatives” where undiscovered mineralization exists in specific intrusions or in their feeder systems, or may also be due to a multiplicity of confounding factors. Wide variability of both Fo and Ni between related intrusions at regional scale may be a useful regional prospectivity indicator, more than an intrusion-scale discriminant, and is certainly informative as a petrogenetic indicator. In general, the use of Ni-olivine as a fertility tool is more likely to generate false negatives than false positives, but both are possible, and the technique should be used as part of a broader weight-of-evidence approach.
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- 2023
8. Compositions and Ni-Cu-PGE Tenors of Nova-Bollinger Ores with Implications for the Origin of Pt Anomalies in PGE-Poor Massive Sulfides
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Stephen J. Barnes, Clifford R. Stanley, and Valentina Taranovic
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Geophysics ,Geochemistry and Petrology ,Economic Geology ,Geology - Abstract
The Nova-Bollinger Ni-Cu-platinum group element (PGE) deposit in the Fraser zone of the Albany-Fraser orogen consists of two main orebodies, Nova and Bollinger, hosted by the same tube-shaped intrusion but having distinctly different Ni tenors of around 6.5 and 4.8 wt %, respectively. Nova is also higher in Pd, but Cu and Pt tenors are similar. Both deposits have very low PGE tenors, with average Pd concentrations of 110 ppb in massive sulfide at Bollinger and 136 ppb at Nova. The Nova and Bollinger orebodies show relatively little internal differentiation overall on deposit scale but show strong differentiation into chalcopyrite-rich and chalcopyrite-poor regions at a meter scale. This differentiation is more prevalent at Nova, where massive sulfide-filled vein arrays are more extensively developed, and in massive ores, particularly veins, than in net-textured ores. Net-textured and disseminated ores have on average Ni and Cu grades and tenors similar to those of massive, semimassive, and breccia ores in the same orebody but a smaller range of variation, largely due to a more limited extent of sulfide liquid fractionation and higher average concentrations of Pt and Pd than adjacent massive ores. Unusually for differentiated magmatic sulfides, there is no systematic positive correlation between Pt, Pd, and Cu. A partial explanation for the lack of a Pd-Cu correlation is that Pd was partitioned into peritectic pentlandite in the middle stages of sulfide liquid solidification. This explanation is not applicable to Pt, as Pt characteristically forms its own phases rather than residing in base metal sulfides. PGE tenors are very low in both orebodies, very similar to those observed in other Ni-Cu-Co sulfide ores in orogenic settings, notably the Savannah and Savannah North orebodies. This depletion is attributed to sulfide retention in the mantle source of the parent magmas rather than to previous fractional extraction of sulfide liquid in staging chambers or feeder networks. The higher Ni and Pd tenors at Nova are attributed to reworking and upgrading of precursor sulfide liquid originally deposited upstream at the Bollinger site. Replicate analyses of multiple jaw-crusher splits returned highly variable Pt and Au assays but much smaller relative errors in the other PGEs. The poor Pt and Au reproducibilities are attributed to nugget effects, explicable by much of the Pt and Au in the samples being present in sparse Pt- and Au-rich grains. This is principally true for Pt in massive rather than disseminated ores, accounting for a strong contrast in the distribution of Pt/Pd ratios between the two ore types. Numerical simulation suggests that Pt is predominantly resident in Pt-rich platinum group minerals with grain diameters of 100 µm or more and that at the low (
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- 2022
9. Lithologic and Geochemical Constraints on the Genesis of a Newly Discovered Orebody in the Jinchuan Intrusion, NW China
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Jian Kang, Xie-Yan Song, Ting-Mao Long, Qing-Lin Liang, Stephen J. Barnes, Lie-Meng Chen, De-Xian Li, Qi-Xing Ai, and Ya-Lin Gao
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Geophysics ,Geochemistry and Petrology ,Economic Geology ,Geology - Abstract
The Jinchuan Ni-Cu-platinum group element (PGE) sulfide deposit is one of the world’s major magmatic sulfide deposits. The Jinchuan intrusion originally consists of two independent bodies, named the Western and Eastern intrusions. Recently, an underground exploration program discovered a large economic orebody in the Fine-Grained unit of the Western intrusion, independent of the orebody No. 24 that occurs at the base of the Coarse-Grained unit. The newly discovered orebody dips to the southwest with thicknesses of 20 to 150 m and is composed of olivine-sulfide cumulates with net-textured sulfide overlain by lherzolite with disseminated sulfide. The net-textured olivine-sulfide cumulates have average grades of 2.1 wt % Ni and 1.2 wt % Cu, whereas the disseminated ores in the lherzolite have average grades of 0.6 wt % Ni and 0.4 wt % Cu. This makes this orebody, named orebody No. 3 and hosted in segment III, the fourth largest at Jinchuan. The sharp lithologic and chemical variation between the net-textured olivine-sulfide cumulates and the disseminated sulfide-bearing lherzolite indicates that they were formed by different processes. Evident differences in sulfidefree whole-rock compositions reflect the dunite forming as olivine adcumulate and the lherzolite as olivine orthocumulate with variable trapped liquid abundances. The olivine-sulfide cumulates were formed by percolation of sulfide liquid into the olivine adcumulates, expelling the interstitial silicate melts upward, whereas the disseminated ores in the lherzolite were formed by settling of finely dispersed sulfide droplets in the olivine crystal mush, within which pyroxene crystallized from the interstitial melts. Variations of PGE tenors of the net-textured sulfides demonstrate fractionation of the sulfide liquids. The relatively high PGE tenors of the disseminated sulfides compared with the net-textured sulfides are associated with upgrading of the sulfides due to reaction with fresh magma.
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- 2022
10. Sulfide Ore Formation of the Kalatongke Ni-Cu Deposit as Illustrated by Sulfide Textures
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Ya-Jing Mao, Stephen J. Barnes, Belinda Godel, Louise Schoneveld, Ke-Zhang Qin, Dongmei Tang, Morgan Williams, and Zhen Kang
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Geophysics ,Geochemistry and Petrology ,Economic Geology ,Geology - Abstract
The Kalatongke magmatic Ni-Cu deposit features high Ni-Cu grades compared with other Ni-Cu deposits in the Central Asian orogenic belt. The sulfides, mainly hosted by olivine norite and gabbronorite, are characterized by high Cu/Ni ratios. There is wide variety of textural relationships in the mineralized rocks, including globular, sulfide matrix, emulsion, disseminated, net-textured, and semimassive to massive textures. Quantitative textural measurements reveal that more than 65 vol % of the total sulfide volume in disseminated ore (defined as containing 4–10 vol % sulfide) and more than 90 vol % of the total sulfide volume in net-textured ore (typically 16 vol % sulfide) are hosted in few interconnected networks with equivalent sphere diameters (ESDs) larger than 6 mm. This illustrates that sulfide coalescence is a critical process. The remaining sulfide blebs define two groups of log-linear particle size distribution (PSD), i.e., a finer group (ESD of 0.080–
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- 2022
11. Native gold enrichment process during growth of chalcopyrite-lined conduits within a modern hydrothermal chimney (Manus Basin, PNG)
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Si-Yu Hu, Stephen J. Barnes, Anais Pagès, Michael Verrall, Joanna Parr, Zakaria Quadir, Louise Schoneveld, and Ray Binns
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Geophysics ,Geochemistry and Petrology - Abstract
Seafloor hydrothermal chimneys from back-arc basins are important hosts for metals such as Cu, Zn, Pb, Ag, and Au. Although the general growth history of chimneys has been well documented, recent studies have revealed that the fine-scale mineralogy can be highly complex and reflects variable physicochemical conditions of formation. This study utilized a novel combination of scanning electron microscopy (SEM)-based electron backscattered diffraction (EBSD) and synchrotron X-ray fluorescence microscopy (SXFM) to uncover the detailed growth processes of multiple chalcopyrite-lined conduits within a modern chalcopyrite-sphalerite chimney from Manus Basin and to assess the controls on native gold precipitation. On the basis of previous studies, the chimney conduit was thought to develop from an initial sulfate-dominated wall, which was subsequently dissolved and replaced by sphalerite and chalcopyrite during gradual mixing of hydrothermal fluids and seawater. During this process, sphalerite was epitaxially overgrown by chalcopyrite. Accretionary growth of chalcopyrite onto this early formed substrate thickened the chimney walls by bi-directional growth inward and outward from the original tube wall, also enclosing the outgrown pyrite cluster. A group of similar conduits with slightly different mineral assemblages continued to form in the vicinity of the main conduit during the further fluid mixing process. Four types of distinct native gold-sulfide/sulfosalt associations were developed during the varying mixing of hydrothermal fluids and seawater. Previously unobserved chains of gold nanoparticles occur at the boundary of early sphalerite and chalcopyrite, distinct from gold observed in massive sphalerite as identified in other studies. These observations provide baseline data in a well-preserved modern system for studies of enrichment mechanisms of native gold in hydrothermal chimneys. Furthermore, native gold is relatively rarely observed in chalcopyrite-lined conduit walls. Our observations imply that: (1) native gold is closely associated with various sulfides/sulfosalts in chalcopyrite-lined conduit walls rather than limited to the association with tennantite, Bi-rich minerals, and bornite as reported previously; and (2) the broad spectrum of gold occurrence in chalcopyrite-line conduits is likely to be determined by the various mixing process between hot hydrothermal fluids with surrounding fluids or seawater. Quantitative modeling of fluid mixing processes is recommended in the future to probe the precise gold deposition stages to efficiently locate gold in modern hydrothermal chimneys.
- Published
- 2022
12. Coupled Li-P Zoning and Trace Elements of Olivine from Magmatic Ni-Cu Deposits: Implications for Postcumulus Re-Equilibration in Olivine
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Ya-Jing Mao, Louise Schoneveld, Stephen J Barnes, Morgan J Williams, Ben-Xun Su, Philipp Ruprecht, Noreen J Evans, and Ke-Zhang Qin
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Geophysics ,Geochemistry and Petrology - Abstract
Olivine is an important mineral in mafic–ultramafic rocks and records various crustal and mantle processes in basaltic magma. Generally, phosphorus (P) is immobile in olivine and its zoning tends to record magmatic processes. In contrast, lithium (Li) is one of the most mobile elements in olivine and tends to be re-distributed by postcumulus to hydrothermal processes. This study reports coupled Li-P oscillatory and sector zoning in cumulus olivine (Fo > 80 mol%) from magmatic Ni-Cu deposits in northwest China. The close to 1:1 relationship between Li + Na cation and P cation in olivine suggests P substitutes for slowly diffusing Si at the tetrahedral site and Li (Na) substitutes for Mg at the octahedral metal site. The preservation of such coupled Li-P zoning suggests that the charge-balanced–controlled substitution of Li+P5+ for Mg2+Si4+, producing a member of the Li(Fe)PO4 structure, may cause sluggish Li diffusion in olivine. The Li-P zoning is uncorrelated to other elements (Fe, Mg, Cr, Al, Ca, Ti, V, Ni, Zn, Mn, Co, and Sc). The Ca abundances in cumulus olivine are significantly depleted relative to those in volcanic olivine and modeled for olivine using the rhyolite–MELTS program, whereas the Mg, Fe, Mn, Zn, Ni, and Co contents show no signs of depletion. The Cr and Al contents in high Fo olivine are lower than those in volcanic olivine with a similar Fo value. The depletions in Ca, Cr, and Al (both divalent and trivalent cations) have been attributed to post-crystallization re-equilibration processes. We suggest that the selective Ca-Cr depletion in olivine resulted from re-equilibration between olivine and clinopyroxene–orthopyroxene–spinel–melts at the postcumulus stage, whereas the Al content variation in olivine is likely controlled by olivine–spinel (pyroxene) re-equilibration. Olivine fractionation modeling results reveal that Co content in both olivine and sulfides changes slightly during evolution, whereas the olivine Ni/Co ratio decreases dramatically from 30 (at Fo90) to 4 (Fo80). These are consistent with the variation of Ni and Co contents in olivine from sulfide-barren rocks but cannot explain the strong positive Ni-Co correlation observed in olivine from the sulfide-bearing rocks. The considerable increase in the Ni/Co ratio in olivine coexisting with the high Ni tenor sulfide compared with the slight increase of the Ni/Co ratio in olivine coexisting with moderate-low Ni tenor sulfide strongly suggests that the Ni and Co contents and Ni/Co ratio in olivine from the mineralized rocks were the results of olivine–sulfide interaction. The olivine Fe/Zn and Mn/Zn ratios show little difference between sulfide-barren and sulfide-rich rocks, but these ratios decrease considerably with the decreasing Fo values. Overall, the study suggests that elements (Ca, Cr, Al, Mg, Fe, Ni, Co, Zn, etc.) diffuse faster than P have been re-distributed in cumulus olivine by re-equilibration processes, modifying the elemental content and inter-element ratios in olivine. The characteristics of the crystallization, particularly the source recorded in cumulus olivine, may be obscured and overprinted by postcumulus processes.
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- 2022
13. Evolution of the Munali Intrusive Complex: Host to a carbonate-rich Ni-(Cu-PGE) sulfide deposit
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Daryl E. Blanks, David A. Holwell, Stephen J. Barnes, Louise E. Schoneveld, Adrian J. Boyce, and Laston Mbiri
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Geochemistry and Petrology ,Economic Geology ,Geology - Published
- 2022
14. The critical role of magma degassing in sulphide melt mobility and metal enrichment
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Giada Iacono-Marziano, Margaux Le Vaillant, Belinda M. Godel, Stephen J. Barnes, and Laurent Arbaret
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Multidisciplinary ,General Physics and Astronomy ,General Chemistry ,General Biochemistry, Genetics and Molecular Biology - Abstract
Much of the world’s supply of battery metals and platinum group elements (PGE) comes from sulphide ore bodies formed in ancient sub-volcanic magma plumbing systems. Research on magmatic sulphide ore genesis mainly focuses on sulphide melt-silicate melt equilibria. However, over the past few years, increasing evidence of the role of volatiles in magmatic sulphide ore systems has come to light. High temperature-high pressure experiments presented here reveal how the association between sulphide melt and a fluid phase may facilitate the coalescence of sulphide droplets and upgrade the metal content of the sulphide melt. We propose that the occurrence of a fluid phase in the magma can favour both accumulation and metal enrichment of a sulphide melt segregated from this magma, independent of the process producing the fluid phase. Here we show how sulphide-fluid associations preserved in the world-class Noril’sk-Talnakh ore deposits, in Polar Siberia, record the processes demonstrated experimentally.
- Published
- 2021
15. Variability of sulfur isotopes and trace metals in pyrites from the upper oceanic crust of the South China Sea basin, implications for sulfur and trace metal cycling in subsurface
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Si-Yu Hu, Xuan-Ce Wang, Liyan Tian, Laure Martin, Louise Schoneveld, Stephen J. Barnes, Paul Guagliardo, Weiwei Ding, and William D.A. Rickard
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Geochemistry and Petrology ,Geology - Published
- 2022
16. Quantitative assessment of the relative roles of sulfide liquid collection, magmatic degassing and fluid-mediated concentration of PGE in low-sulfide ores of the Norilsk intrusions
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Yulia D. Gritsenko, Alexandra P. Kondrikova, Sabine Gilbricht, Louise Schoneveld, Stephen J. Barnes, Bélinda M. Godel, Sergey F. Sluzhenikin, Dmitry B. Petrenko, Thomas Seifert, and Marina A. Yudovskaya
- Subjects
Geochemistry and Petrology ,Economic Geology ,Geology - Published
- 2022
17. Nova-Bollinger Ni-Cu sulfide ore deposits, Fraser Zone, Western Australia: Petrology of the host intrusions sulfide-silicate textures and emplacement mechanisms of the ores
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Taranovic, Valentina, primary, Stephen, J. Barnes, additional, Beresford, Steve, additional, Miller, John, additional, and Rennick, Steven, additional
- Published
- 2019
- Full Text
- View/download PDF
18. List of Contributors
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Yuri Amelin, Nicholas T. Arndt, Gennadiy Artemenko, Wenqian Bai, Darcy Baker, Stephen J. Barnes, Ann M. Bauer, Robert L. Bauer, Raphael Baumgartner, Richard W. Belcher, Vickie C. Bennett, Ankit Bhandari, Marion E. Bickford, Janne Blichert-Toft, Svetlana Bogdanova, Christian O. Böhm, Bernard Bourdon, Gary R. Byerly, Richard W. Carlson, Nicole Cates, Barbara Cavalazzi, Aaron J. Cavosie, Thomas Chacko, Godfrey Chagondah, Kevin R. Chamberlain, David C. Champion, Stefan Claesson, Kent C. Condie, Brendan Cummins, Alexandra Krull Davatzes, Sukanta Dey, Tara Djokic, Chunyan Dong, Annika Dziggel, J. Elis Hoffmann, Don Francis, Clark R.L. Friend, Yashvardhan Gaur, Steven Goderis, William L. Griffin, Martin Guitreau, Xie Hangqiang, Simon L. Harley, Russell P. Hartlaub, Larry M. Heaman, Esa Heilimo, Christoph Heubeck, Keyron Hickman-Lewis, Axel Hofmann, Pentti Hölttä, Hannu Huhma, David L. Huston, George D. Kamenov, James F. Kasting, Nigel M. Kelly, Anthony I.S. Kemp, Alexander F.M. Kisters, Asko Kontinen, Alfred Kröner, Monika A. Kusiak, Laura Lauri, Morgane Ledevin, Baptiste Lemirre, Evelyn Y. Levine, Yuan Li, Dunyi Liu, Yongsheng Liu, Shoujie Liu, Donald R. Lowe, Yongjun Lu, Mingzhu Ma, Terrence P. Mernagh, Aniruddha Mitra, Stephen J. Mojzsis, Sudipto Mondal, Peter Morant, Jean-Francois Moyen, Paul A. Mueller, Elodie Muller, Thorsten J. Nagel, Jinia Nandy, Pritam Nasipuri, Marc D. Norman, Allen P. Nutman, Jonathan O'Neil, Craig O'Neill, Suzanne Y. O'Reilly, Dominic Papineau, Jayanta K. Pati, Pascal Philippot, Franco Pirajno, Greg Poole, Jesse R. Reimink, Claire Rollion-Bard, Antoine S.G. Roth, Lopamudra Saha, Scott D. Samson, Saheli Sarkar, Aaron M. Satkoski, Manavan Satyanaryanan, Mark D. Schmitz, Graham A. Shields, Leonid Shumlyanskyy, Bruce M. Simonson, Alexandr Slabunov, Robert H. Smithies, Catherine Spaggiari, Luke Steller, Gary Stevens, Kenichiro Sugitani, Sahand Tadbiri, Abhishek Topno, John W. Valley, Martin J. Van Kranendonk, Mark A. van Zuilen, Yusheng Wan, Frances Westall, Simon A. Wilde, Michael T.D. Wingate, Joseph L. Wooden, Stephen Wyche, Hangqiang Xie, Shiwen Xie, Chao Zhang, Siqi Zhang, and Keqing Zong
- Published
- 2019
19. List of Contributors
- Author
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Ahmed H. Ahmed, Shoji Arai, Stephen J. Barnes, Graham C. Begg, Elena A. Belousova, Dmitriy A. Chareev, Marco L. Fiorentini, William L. Griffin, Jon M.A. Hronsky, Rais M. Latypov, Margaux Le Vaillant, Chusi Li, Kreshimir N. Malitch, Sisir K. Mondal, Ria Mukherjee, Suzanne Y. O’Reilly, Kwan-Nang Pang, Edward M. Ripley, J. Gregory Shellnutt, Sergey F. Sluzhenikin, Joyashish Thakurta, Jill A. VanTongeren, Anna Vymazalová, and Inna Yu Badanina
- Published
- 2018
20. The 1.88 Ga Kotalahti and Vammala nickel belts, Finland: geochemistry of the mafic and ultramafic metavolcanic rocks
- Author
-
Stephen J. Barnes, Hannu V. Makkonen, Sarah E. Dowling, Robin E.T. Hill, and Petri Peltonen
- Subjects
lcsh:Geology ,nickel ,sulfides ,lcsh:QE1-996.5 ,picrite ,ultramafics ,platinum ,volcanic rocks ,Svecofennian ,Finland - Abstract
The mafic and ultramafic volcanic rocks within the Svecofennian (1.88 Ga) Kotalahti and Vammala Nickel Belts, Finland, are spatially associated and coeval with a suite of mineralized mafic–ultramafic intrusions. They have been divided into five suites based on major element geochemistry and spatial distribution: the Rantasalmi high- and low-Mg suites, the Vammala high-Mg suite, and the Rantasalmi, Kestilä and Pielavesi low-Mg suites. The Rantasalmi and Vammala high-Mg suites are very similar and probably comagmatic, and the Kestilä and Rantasalmi low-Mg suites are derived from them by a combination of fractionation and crustal assimilation. The Pielavesi suite is interpreted as an unrelated suite of island-arc affinity.On the basis of their trace element contents, the Kotalahti Belt intrusions are comagmatic with part of the analyzed volcanic rocks. In the Vammala Belt it is likely that the parent magmas to the intrusions and picrite magmas have a common mantle source but have evolved along distinct paths, and the picrites probably do not represent parent magmas tapped directly from the intrusions. Platinum-group element data show localised evidence for depletionby sulfide extraction. Vammala picrites are predominantly S-undersaturated, with the exception of lavas in the Stormi area. In the Kotalahti Belt the volcanic rocks are predominantlyS-undersaturated, while the volcanic rocks in the more northern part of the Belt are predominantly S-saturated. These spatial differences imply that the PGE contents of the metavolcanic rocks can be used as regional area selection criteria for intrusive nickel-copper-(PGE) deposits within the Finnish Svecofennian.
- Published
- 2009
21. Mapping non-magnetic, talc-bearing ultramafic rocks in the Kalgoorlie region using airborne hyperspectral data
- Author
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Bruce Groenewald, Rob Hewson, Stephen J. Barnes, and Thomas Cudahy
- Subjects
Non magnetic ,Ultramafic rock ,Outcrop ,Pediment ,Soil water ,General Engineering ,medicine ,Schist ,Hyperspectral imaging ,Mineralogy ,Talc ,Geology ,medicine.drug - Abstract
Previously unrecognised ultramafic units in the Kalgoorlie-Kanowna area have recently been discovered using airborne hyperspectral sensing. Some of these units are up to 1 km in length and 200 m in width and were identified through airborne mineral mapping of talc. These areas lack significant magnetic expression, have little or no outcrop or subcrop and comprise a surface dominated by talc-bearing soil pediment. Exploration drill spoil in these areas confirms the presence of weathered talc schists underlying the soils. These results suggest that even in well mapped areas of deeply weathered greenstone belts, airborne hyperspectral sensing can complement traditional geophysical data by mapping non-magnetic, talc-bearing ultramafic rocks, which may be potential hosts to massive nickel and base metal mineralisation.
- Published
- 2006
22. Comparative lithogeochemistry of komatiites in the Norseman-Wiluna and Abitibi Greenstone Belts, and implications for nickel sulfide targeting
- Author
-
Stephen J. Barnes, Rebecca A. Sproule, and C. Michael Lesher
- Subjects
chemistry.chemical_classification ,Olivine ,Nickel sulfide ,Sulfide ,General Engineering ,Geochemistry ,engineering.material ,Mantle plume ,Tectonics ,chemistry.chemical_compound ,chemistry ,Magma ,engineering ,Geology ,Terrane - Abstract
This paper uses large sets of whole-rock geochemical data to make comparisons between the komatiitic rocks of Abitibi (AGB) and Norseman-Wiluna (NWGB) greenstone terranes. The NWGB komatiite suite has a much higher proportion of highly olivine-enriched cumulates than the AGB suite, as indicated by data-density distributions on plots of MgO vs FeO and MgO vs Cr, although average compositions of the komatiite magmas in the two belts were not significantly different. NWGB komatiites appear generally more contaminated, on the basis of various ratios of strongly to moderately incompatible low-mobility trace elements. Both factors which are likely contributors to the much higher Ni sulfide resource endowment of the NWGB. The combination of high degrees of contamination and presence of olivine adcumulates in the NWGB attests to the presence of exceptionally high-intensity, prolonged eruptions, capable of forming long-lived entrenched magma pathways, represented by highly olivine-enriched cumulates, and capable of melting substrates to form orebodies. This is in contrast with more episodic, lower volume eruptions in the AGB. The contrast is interpreted as the result of crustal structure and tectonic setting, rather then the size and intensity of mantle plume sources.
- Published
- 2006
23. The Perseverance and Mount Keith Nickel Deposits of the Agnew-Wiluna Belt, Yilgarn Craton, Western Australia
- Author
-
Marco L. Fiorentini, Paul Duuring, Caroline S. Perring, Ben Grguric, and Stephen J. Barnes
- Subjects
Geochemistry ,Yilgarn Craton ,Geology ,Mount - Published
- 2011
24. Nickel Deposits of the Yilgarn Craton
- Author
-
Stephen J. Barnes
- Subjects
Mineralization (geology) ,Nickel sulfide ,Geochemistry ,chemistry.chemical_element ,Yilgarn Craton ,engineering.material ,Boom ,Nickel ,chemistry.chemical_compound ,chemistry ,Ultramafic rock ,Laterite ,engineering ,Prospecting ,Geology - Abstract
The Yilgarn craton is one of the world's major nickel provinces, containing 31.5 million tonnes (Mt) of Nimetal with an in situ value of about $350 billion on a pre-mining basis, amounting to 13.6 percent of the world'scurrently known Ni resources. This entire resource inventory has been discovered since 1966. This chapterpresents an analysis of the 40-year discovery history, which isideal as a province-scale case study in mineralexploration. The province experienced a major peak in exploration activity between 1966 and 1971, the "nickel boom," which accounted for more than half of all NiS deposits, and all of the giant (>1 Mt Ni) NiS deposits so far discovered. Almost 70 percent of those discoveries were related to direct surface prospecting methods, commonly based on recognition of magnetic ultramafic rocks as favorable hosts. Since the end of the nickel boom, the dominant discovery method has been follow-up exploration around significant known mineralization. From about the mid-1990s, electromagnetic (EM) surveying, which had been considered ineffective during the nickel boom phase, became a demonstrably successful technique for the detection of sulfide deposits. An improved understanding of geologic processes and controls has played an important role in sustaining exploration success since the end of the early, surface-prospecting phase of the nickel boom. Most nickel laterite deposits were first found during the nickel boom but not considered at that time to be economically significant. A large surge in exploration activity, much of it focused on resource delineation rather than true green-fields exploration, occurred between 1996 and 2001, triggered by the advent of the Pressure Acid Leach (PAL) technology in the mid-1990s. The discovery record of the Yilgarn province exhibits many patterns typical of an exploration province: early discovery of both the largest deposits and most of the metal and generally increasing discovery costs as the province matures. The average discovery costs for nickel in the Yilgarn have been 5.2 c/lb for sulfide nickel and 0.6 c/lb for laterite nickel. The Yilgarn province offers two examples of exploration expenditure booms arising from the coincidence of an upturn in commodity price with the opening up of new exploration parameter spaces. These are the initial discovery of komatiite-hosted nickel sulfide at Kambalda in 1966, and the mid-1990s recognition of the potential of PAL technology to treat laterite ore deposits.
- Published
- 2006
25. Introduction
- Author
-
Stephen J. Barnes and Robin E. T. Hill
- Subjects
Earth and Planetary Sciences (miscellaneous) ,General Earth and Planetary Sciences - Published
- 1992
26. Geochemistry of the J-M (Howland) Reef of the Stillwater Complex, Minneapolis Adit area; I, Sulfide chemistry and sulfide-olivine equilibrium; reply
- Author
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Stephen J. Barnes and Anthony J. Naldrett
- Subjects
Geophysics ,Geochemistry and Petrology ,Economic Geology ,Geology - Published
- 1986
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