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1.
《International Geology Review》2012,54(10):917-926
The results of a study of copper, nickel, cobalt, platinum, palladium, gold, and rhodium distribution in basic ore-forming sulfide minerals (chalcopyrite and pyrrhotites) as well as in the silicate portion of the host rocks of the Noril'sk deposit, are given. Interrelations between metals in different sulfide minerals and silicates are characterized. It has been established that palladium, platinum, and gold are concentrated in chalcopyrite while cobalt and rhodium are concentrated in pyrrhotite. The cobalt and precious metal content in sulfides grows with the increase of their nickel content. The relative content, however, of all these elements estimated for 1% of nickel is different in chalcopyrites and pyrrhotites. The former show a high platinum, palladium, and gold content and the latter--cobalt and rhodium. Ratios of these elements in sulfides and silicates are different. The relative platinum content increases in silicates due to a considerably greater content of mineralized platinum. Both nickel and cobalt form silicate compounds the latter to a much greater extent than the former. The relative cobalt content is therefore higher in silicates than in sulfides. In descending order, the element concentrations in sulfides range as follows: copper, nickel, palladium, gold, cobalt, platinum. — Auth. English Summ. 相似文献
2.
Granite-hosted gold mineralization in the Midlands greenstone belt: a new type of low-grade gold deposit in Zimbabwe 总被引：1，自引：0，他引：1
In 1992, the Ford gold deposit was rediscovered during field work in the Kwekwe district near the Indarama mine, approximately 200 km southwest of Harare, Zimbabwe. Based on diamond drilling and open pit operations, estimated ore reserves are at least 3 Mt with an average gold content of 2.5 g/t. The gold deposit is located within a porphyritic granite dike with a thickness of 20–50 m, striking 800 m NNW-SSE. It dips 60–70° to the NE and intrudes a volcano-sedimentary sequence of tholeiitic basalts, acid volcanics, and banded iron formations of the Bulawayan Group (2900–2700 Ma). The intrusion of the dike occurred at 2541 ± 17 Ma (Pb/Pb step leaching technique) within a second order structure and is related to displacement along transcrustal deformation zones such as the Sherwood- and Taba-Mali deformation zones. Gold mineralization is confined to the s-shaped part of the dike intrusion. At the present stage of mining, the deposit is characterized by the absence of major veins, the occurrence of disseminated pyrite throughout the orebody, and a distinct alteration pattern comparable to that of porphyry copper deposits. The central zone of the dike shows a typical K-feldspar-albite-sericite-pyrite (±biotite?) alteration, followed by a narrow external propylitic zone. Native gold with an average Ag content of 5 wt.% and a grain size of 5–100 μm is rare and occurs within pyrite and secondary K-feldspar. Sulphide mineral separates of pyrite and minor arsenopyrite probably contain invisible gold (up to 120 ppm) amenable to cyanidation. Anomalously high gold values of ～7 ppm have been found in the transition between the K-feldspar-albite-sericite-pyrite alteration and the propylitic zone, indicating that the mineralizing fluids have experienced major physico-chemical changes in the transition zone. The regional tectonic position of the orebody suggests that the emplacement of the granite and the gold mineralization are structurally controlled. The Pb isotope composition of several leachates of pyrite indicate isotope disequilibrium with magmatic minerals and point to a contamination of the mineralizing fluid by Pb from older (sedimentary?) sources. Stable isotope geochemistry of sulphides and carbonates as well as the metallogeny of the deposit compare to shear-zone hosted gold mineralization in the Kwekwe district, for which a deep crustal origin has been discussed. Although this study documents contrasting evidence for a porphyry-gold versus a shear-zone type of mineralization, it is suggested that gold-bearing fluids were syntectonically introduced into a ductile shear zone within the granite dike either during cooling of the intrusion or later in Archaean or early Proterozoic times. 相似文献
3.
《International Geology Review》2012,54(12):1149-1165
The Gay deposit, situated in the Orenburg region, is identified with one of Russia's principal occurrences of pyrite (pyrite deposits are an important source of Russia's gold). It belongs to the west subzone of the Magnitogorsk synclinorium and occurs in Devonian rhyolite-basaltic volcanic rocks. The deposit comprises five large pyrite-chalcopyrite, pyrite-chalcopyrite- sphalerite, and pyrite orebodies. The supergene zone extends to 120-240 m below surface and consists of the following three subhorizontal zones (from bottom to top): the secondary sulfide enrichment, the leaching, and the oxidation zone (where ores are enriched in gold). There are two levels of secondary gold enrichment in the weathering profile. The lower level, located in the leaching zone, corresponds with the level of water table fluctuations. The rich, flat-lying horizon (1.5-10.0 m) is composed of bedded, friable native sulfur-quartz ores; it contains 19.0-52.2 ppm Au and up to 389 ppm Ag. Native gold and silver halides (chlorargyrite, iodargyrite, and embolite) are the principal precious-metal minerals. Electrum, native silver, acanthite, and uytenbogaardtite constitute the minor ones. The upper level of the enrichment is located in the lower part of gossan. This bonanza is composed of hematite-quartz ochres. Gold concentration is 13.5 to 21.2 ppm. Native gold of high fineness and silver halides apparently are associated here with poorly crystallized iron oxides. The formation of supergene gold enrichments may result partly from residual concentration and partly from mobilization and reprecipitation of the precious metal. Rich horizons form by repeated gold redeposition in accordance with weathering and a gradual erosion surface lowering. The lower bonanza forms at first in the process of oxidation involving pyrite and native sulfur. Gold may be transported by complexes with metastable sulfur oxy-anions: sulfites, thiosulfates, or polythionates. The upper enriched horizon forms in the course of further evolution of the weathering profile in the stage of hematite recrystallizaiton and its transformation into goethite. 相似文献
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5.
K. Nicholson 《Mineralium Deposita》1990,25(2):126-131
A stratiform manganiferous horizon, up to 4 m thick but localised in aerial extent, occurs 10 km south-east of Inverness in north-east Scotland. It overlies Precambrian Grampian Group schists and is itself overlain by Middle Old Red Sandstone (Devonian) conglomerate, which elsewhere rests unconformably on the schists. The deposit was mined briefly in the early 1920s and is composed principally of fine-grained braunite with minor bustamite. Lower sections of the deposit contain cavities, infilled by late baryte, calcite and rhodochrosite, which resemble stromatactis. This horizon is underlain by a hematite-quartz layer, thought to represent a laterite formed by pre-MORS weathering of the underlying schists. The mineralogy and geochemistry of the manganese ore (enriched in Ag, As, Ba, Bi, Pb, Sb, Sr and Zn) are characteristic of a hydrothermal origin. Such an origin, when considered in conjunction with the outcrop, textures, mineralogy and stratigraphy of the deposit together with the palaeogeography of the region, can only be explained by deposition from hot-springs in a sublacustrine environment. Nearby baryte mineralisation may also have been deposited from the same geothermal system, which had the Caledonian 407 Ma Moy granitoid as heat source. The managanese ore is enriched in gold pathfinder elements and minor detrital gold has been found in the area. Gold mineralisation may therefore have also been deposited in the upper sections of this Devonian geothermal system. 相似文献
6.
Gold mineralisation at the Wallaby gold deposit is hosted by a 1,200 m thick mafic conglomerate. The conglomerate is intruded by an apparently comagmatic alkaline dyke suite displaying increasing fractionation through mafic-monzonite, monzonite, syenite, syenite porphyry to late-stage carbonatite. In the mine area, a pipe-shaped zone of actinolite-magnetite-epidote-calcite (AMEC) alteration overprints the conglomerate. Gold mineralisation, associated with dolomite-albite-quartz-pyrite alteration, is hosted in a series of sub-horizontal, structurally controlled zones that are largely confined within the magnetite-rich pipe. The deposit has a current ore reserve of 2.0 Moz Au, and a total resource of 7.1 Moz Au.TIMS U–Pb analysis of magmatic titanite and SHRIMP U–Pb analysis of gold-related phosphate minerals are used to constrain the timing of magmatism and gold mineralisation at Wallaby. Monzogranite and carbonatite dykes of the Wallaby syenite intruded at 2,664±3 Ma, at least 5 m.y. and probably 14 m.y. before gold mineralisation at 2,650±6 Ma. The significant hiatus between proximal magmatism and gold mineralisation suggests that gold-bearing fluids were not derived from magmas associated with the Wallaby syenite, particularly since intrusive events are unlikely to drive hydrothermal systems for more than 1 m.y.Analysis of the C and O isotopic compositions of carbonates from regional pre-syenite alteration and AMEC alteration at the Wallaby gold deposit suggests that AMEC alteration formed via interaction between magmatic fluids and the pre-syenite wallrock carbonate. The C and O isotopic composition of gold-bearing fluids, as inferred from ore-carbonate, are isotopically distinct from proximal magmatic fluids, as inferred from magmatic carbonate in carbonatite dykes.Thus, detailed isotopic and geochronological studies negate any direct genetic link between proximal magmatic activity related to the Wallaby syenite and gold mineralisation at Wallaby. The gold endowment of the Wallaby gold deposit, combined with the relatively low solubility of gold as thiosulfide complexes in low-salinity ore fluids at temperatures of about 300°C, implicates the influx of very large volumes of auriferous hydrothermal fluids. No large-scale shear-zones nor faults through which such large fluid-volumes could pass have been identified within the immediate ore environment, so fluid influx most probably occurred largely in a unit-confined, brittle-ductile fracture system. This was the ~500-m diameter AMEC alteration pipe, which was a brittle, iron-enriched zone in an otherwise massive conglomerate. During compressional deformation, the competency contrast between unaltered and AMEC-altered conglomerate created a zone of increased fracture permeability, and geochemically favourable conditions (high Fe/Fe+Mg ratio), for gold mineralisation from a distal source.Editorial Handling: C. Brauhart 相似文献
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The Macraes deposit (> 10 Moz resource) is a Cretaceous orogenic system hosted in the Hyde-Macraes Shear Zone (HMSZ) which was mineralised under lower greenschist facies during later stages of lower greenschist facies metamorphism of host metasedimentary schists. Gold is encapsulated primarily in sulphides that have replaced silicates in ductile shears that are focussed in micaceous rocks. The shears anastomose around structurally competent lenses, and were enhanced by hydrothermal graphite deposition and alteration of albite to muscovite. In contrast, scheelite with minor auriferous sulphides occurs in multigenerational quartz veins that filled fractures in competent lithologies. Hence, scheelite was deposited coevally with gold, from the same hydrothermal fluid, but in different structural settings from most gold at all scales from millimetres to hundreds of metres. Consequentially, there is weak correlation between Au and W at all scales in the deposit. Multigenerational gold and scheelite mineralisation occurred during progressive deformation in the shear zone in two contrasting structural and mineralogical styles in syn-deformationally weakening gold-bearing micaceous shears, and in syn-deformationally hardened competent rocks that became silicified and veined with quartz and scheelite. Hydrothermal fluid flow in the gold-bearing shears occurred at the grain boundary, microshear, and microfracture scales, and was slow (< 1 m/year), continuous, and pervasive. In contrast, vein formation in more competent lithologies was episodic, locally rapid (> hundreds of m/year), and was controlled by fracture permeability. The Au and W enrichment in the Macraes deposit resulted from regional scale metal mobility, driven by coeval recrystallisation in higher-grade (upper greenschist to amphibolite facies) metamorphism that persisted structurally below the Macraes deposit for at least 10 Ma after mineralisation ceased. 相似文献
8.
老挝琅勃拉邦帕奔金矿地质特征及找矿标志 总被引：1，自引：0，他引：1
老挝帕奔金矿处于云南三江成矿带南延部分,区域上是重要的铁、铜、金矿集中区。目前矿区共发现五条金矿体,其赋矿围岩为下二叠统海相碳酸盐岩,均产于北北东向的韧性剪切带裂隙和北北西向次级构造裂隙中。矿区以发育碳酸盐化为特征,按碳酸盐的产出特征可将金矿体分为蚀变岩型（碳酸盐呈微细脉或复脉）、构造破碎带型（碳酸盐呈胶结物）和含金方... 相似文献
9.
MAO Guangzhou HUA Renmin GAO Jianfeng ZHAO Kuidong LONG Guangming LU Huijuan YAO Junming 《《地质学报》英文版》2010,84(3):614-623
<正>Jinshan gold deposit is located in northeastern Jiangxi,South China,which is related to the ductile shear zone.It has a gold reserve of more than 200 tons,with 80%of gold occurring in pyrite. The LREE of gold-bearing pyrite is as higher as 171.664 ppm on average,with relatively higher light rare earth elements(LREE;159.556 ppm) and lower HREE(12.108 ppm).TheΣLREE/ΣHREE ratio is 12.612 and(La/Yb)_N is 11.765.These indicate that pyrite is rich in LREE.The(La/Sm)_N ratio is 3.758 and that of(Gd/Yb)_N is 1.695.These are obvious LREE fractionations.The rare earth element(REE) distribution patterns show obvious Eu anomaly with averageδEu values of 0.664,andδCe anomalies of 1.044.REE characteristics are similar to those of wall rocks(regional metamorphic rocks),but different from those of the Dexing granodiorite porphyry and Damaoshan biotite granite.These features indicate that the ore-forming materials in the Jinshan gold deposit derived from the wall rocks, and the ore-forming fluids derived from metamorphic water.The Co/Ni ratio(average value 0.38) of pyrite suggests that the Jinshan gold deposit formed under a medium-low temperature.It is inferred from the values of high-field strength elements,LREE,Hf/Sm,Nb/La,and Th/La of the pyrite that the ore-forming fluids of the Jinshan gold deposit derived from metamorphic water with ClF. 相似文献
10.
Gold and platinum-group-metals (PGM) are cycled through Earth’s environments by interwoven geological, physical, chemical and biological processes leading to the trans/neoformation of metallic particles in placers. The placer deposit at Corrego Bom Successo (CBS, Brazil) is one of the few localities worldwide containing secondary gold- and PGM-particles. Placer gold consists of detrital particles from nearby hydrothermal deposits that were transformed in the surface environment. Processes that have affected these particles include short-distance transport, chemical de-alloying of the primary gold‑silver, and (bio)geochemical dissolution/re-precipitation of gold leading to the formation of pure, secondary gold and the dispersion of gold nanoparticles. The latter processes are likely mediated by non-living organic matter (OM) and bacterial biofilms residing on the particles. The biofilms are largely composed of metallophillic β- and γ-Proteobacteria. Abundant mobile gold and platinum nanoparticles were detected in surface waters, suggesting similar mobilities of these metals. Earlier hydrothermal processes have led to the formation of coarsely-crystalline, arborescent dendritic potarite (PdHg). On potarite surfaces, biogeochemical processes have then led to the formation of platinum- and palladium-rich micro-crystalline layers, which make up the botryoidal platinum‑palladium aggregates. Subsequently potarite was dissolved from the core of many aggregates leaving voids now often filled by secondary anatase (TiO2) containing biophilic elements. The presence of fungal structures associated with the anatase suggests that fungi may have contributed to its formation. For the first time a primary magmatic PGM-particle comprising a mono-crystalline platinum‑palladium-alloy with platinum‑iridium‑osmium inclusions was described from this locality, finally defining a possible primary source for the PGM mineralisation. In conclusion, the formation of modern-day placer gold- and PGM-particles at CBS began 100s of millions of years ago by magmatic and hydrothermal processes. These provided the metal sources for more recent biogeochemical cycling of PGEs and gold that led to the trans/neoformation of gold- and PGM-particles. 相似文献
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小尖山金矿位于康古尔金矿中东段,矿体主要有含金蚀变岩和含金花岗细晶岩两类,以蚀变岩型金矿为主,发育于变质岩区,具有低温绿片岩相的面貌,受韧性剪切带控制并以剪切作用为主要的成矿机制. 相似文献
13.
伏牛山矿床是一个含伴生金的矽卡岩型铜矿床，伴生金的平均品位为０．３６ｇ／ｔ，伴生银的平均品位为１２．４ｇ／ｔ。本文通过多种分析测试（如：相关分析，配分计算，矿相显微镜观察，透射电镜研究，分步溶解，物相分析等），对伴生金的赋存状态做了较为详细的研究。结果表明：金的存在与黄铜矿关系密切；金的存在形式主要为显微金、次显微金及少量晶格金，其中显微金主要存在于黄铜矿中，次显微金及晶格金主要存在于黄铁矿中。 相似文献
14.
A. R. Cabral G. Beaudoin M. Choquette B. Lehmann J. C. Polônia 《Mineralogy and Petrology》2007,90(1-2):141-150
Summary The Córrego Bom Sucesso alluvial deposit near Serro, Minas Gerais, probably provided the specimens from which the element
palladium was first discovered. Its Pt–Pd nuggets are characteristically botryoidal, arborescent and coralloidal, and exhibit
an external halo with the composition of palladiferous platinum to virtually pure platinum. X-ray mapping of an arborescent
Pt–Pd nugget from the historical occurrence documents selective palladium depletion, similar to the high-fineness gold haloes
developed on detrital Au–Ag grains under supergene conditions. The Pd-depleted alteration zone truncates inclusions of crystals
stoichiometrically close to PdPt within the Pt–Pd aggregate. Selective metal leaching in the weathering environment can account
for the frequently observed Pt-enriched rims on alluvial platiniferous alloys which may lead to the formation of platinum
nuggets at an advanced degree of weathering.
Present address: Department of Geology: Exploration Geology Rhodes University PO Box 94, Grahamstown, 6140 South Africa 相似文献
15.
小尖山金矿位于康古尔金矿中东段，矿体主要有含金蚀变岩和含金花岗细晶岩两类，以蚀变岩型金矿为主，发育于变质岩区，具有低温绿片岩相的面貌，受韧性剪切带控制并以剪切作用为主要的成矿机制。 相似文献
16.
义兴寨金矿属于典型的石英脉型金矿床。金矿物以单颗粒的银金矿为主,有少量的自然金。粒度多集中在10～50μm;形态多为浑圆粒状、麦粒状、不规则粒状、角砾状、细脉状等。主要以包体金、粒间金、裂隙金存在于黄铁矿、黄铜矿、石英等颗粒中。利用数量和面积两种统计方法分别对金矿物进行形态、粒度、存在状态的特征统计,显示不同类型金矿物在出现率和面积配分特征上有较大差别。化学成分中普遍含有Fe、S、Cu、Zn、Pb元素,分析得出Fe、S与Au呈不同程度的反相关关系,Pb元素含量相对稳定,Cu、Zn元素变化较大;结合Au、Ag含量与温度关系,显示金矿物形成于中低温环境。成色为510.7~887.9,平均653.6,显示浅成成矿环境。纵向上,从1350 m标高到1070 m标高,金矿物的成色平均值由778.4逐渐降低为651.7,显示逆向分带特征,指示深部1070 m标高以下仍有稳定矿体存在。 相似文献
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Henrik Stendal Robert Frei Sospeter Muhongo Thorkild M. Rasmussen Saidi Mnali Faustin Petro E. Brian Temu 《Journal of African Earth Sciences》2004,38(5):437-447
Gold and base metals of the Mpanda Mineral Field (MMF) is the focus of this paper. Gold veins and gold-bearing base metal occurrences are structurally controlled by conjugate sets of NW–SE and E–W trending faults and/or shear zones that crosscut high-grade metamorphic rocks and post-kinematic intrusions. It was anticipated that Palaeoproterozic country rocks could have been potential host rocks for the gold mineralisation in this area. This argumentation was based on Pb model ages of various deposits from the MMF. Recent fieldwork and Pb isotopic results presented herein indicate that epigenetic gold and base metal vein-type mineralisation in the MMF is post-Palaeoproterozoic.Our Pb isotope study concentrates on constraining the sources of metals in gold-bearing quartz reefs and base metal occurrences. Pb isotopes of whole rocks and minerals indicate that mineralisation was emplaced during the Neoproterozoic, contemporaneous with the intrusion of alkaline granites and carbonatite complexes (e.g., Sangu–Ikola carbonatite complex) at 720 Ma. The source of Pb in the mineral occurrences is compatible with that characteristic of the Palaeoproterozoic host rocks. Aeromagnetic data suggest that the gold-bearing, NNW–SSE trending area continues to the north beyond Mpanda town. Pb isotope results and aeromagnetic data have significant implications for future exploration programs within the region, in that the search should potentially focus on the defined geophysical borders and trendlines, and on Neoproterozoic, rather than Palaeoproterozoic vein systems. 相似文献
19.
Simon J. Meldrum Romeo S. Aquino Rene I. Gonzales Robert J. Burke Artha Suyadi Bambang Irianto Donald S. Clarke 《Journal of Geochemical Exploration》1994,50(1-3)
The Batu Hijau porphyry Cu---Au deposit lies in southwest Sumbawa Island, Indonesia. It is a world-class porphyry Cu deposit in an island are setting, and is typical of this deposit type in most features, including igneous association, morphology, hydrothermal alteration and mineralisation style.The region was not previously recognised as a porphyry Cu province; disseminated Cu sulphides were first recognised in float samples in southwest Sumbawa in 1987. Associated stream sediment sampling identified a broad area of anomalous Au and Cu in an area of greater than 5 km2 around Batu Hijau, including 169 ppb Au in BLEG samples and 580 ppm Cu in stream silts 1 km from the deposit. Mineralisation in bedrock at surface contains > 0.1 wt % Cu and > 0.1 ppm Au over an area of 0.6 km × 1.2 km, including a zone 300 m × 900 m containing > 0.3 wt % Cu. Areas with elevated Mo (> 30 ppm) form a distinctive annulus around this Cu-rich zone.Batu Hijau mineralisation is hosted in a tonalite intrusive complex, and diorite and metavolcanic wallrocks. There are no post-mineralisation igneous intrusions or breccia pipes within the deposit. The main tonalite intrusion forms a stock in the centre of the deposit, where it generally displays intensely pervasive potassic (biotite with magnetite-quartz) alteration and hosts most of the higher grade mineralisation. Younger tonalite dykes intruding the centre of this stock are generally less altered and mineralised than the older tonalite.The core zone of potassic alteration grades outward into extensive propylitic alteration (chlorite-epidote), with both variably overprinted by widespread fracture controlled intermediate argillic alteration (sericite-chlorite), and minor phyllic (sericite-pyrite) and sodic (albite) alteration. Argillic (sericite-kaolinite) and advanced argillic (kaolinite-alunite-pyrophyllite) assemblages occur near surface.Copper and Au grades within the orebody show a positive correlation with quartz stockwork intensity, although disseminated Cu sulphides are also common. Chalcopyrite and bornite are the principle hypogenal minerals, with minor chalcocite. Oxidation extends to a depth of 5 m to 85 m below surface across the deposit, and is underlain by weak supergene mineralisation. Drill testing of the deposit down to 650 m below surface reveals a single cylindrical to conical orebody of 334 million tonnes grading 0.8 wt % Cu and 0.69 gm per tonne Au; the depth extent of mineralisation is unknown. 相似文献
20.
《Journal of Structural Geology》2004,26(6-7):995-1005
The Southern Alps of New Zealand is an active oblique collisional mountain belt with extensive regional tectonically driven fluid flow. There is no evidence for igneous activity, and fluids consist of varying proportions of meteoric water and mid-crustal fluid derived from dehydration reactions. Fluid flow is controlled by fracture porosity, particularly in damage zones along faults and fault intersections. Gold and arsenic bearing veins exposed at the surface indicate two principal zones of gold mineralisation at depth. One of these is in the highest mountains, near to, but not in the region of maximum uplift. Deformation is dominated by reverse faulting, but some normal and strike-slip faults occur as well. The other zone of gold mineralisation is at and near the intersection of regional oblique dextral reverse faults and regional strike-slip faults. Both zones are characterised by small discontinuous vein systems, locally accompanied by ankeritic alteration of host rock. Veins occur in extensional and shear veins, and in dilational jogs with implosion breccias. Gold mineralisation occurred at many structural levels between the brittle–ductile transition and the near-surface region. The Southern Alps hydrothermal system represents an active roof zone to a mesothermal gold deposition system at depth. As such, this is a modern analogue for mesothermal gold terranes elsewhere in New Zealand and around the world. Observations on the regional distribution of fluid flow in active orogens can give insights into fluid flow at depth where gold mineralisation is occurring now. Comparison of these observations with ancient gold-bearing belts allows construction of three-dimensional concepts of orogenic fluid flow and gold mineralisation. 相似文献