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1.
我国一些铜镍硫化物矿床主要金属矿物的特征 总被引：7，自引：0，他引：7
镍、铜共生的铜镍硫化物矿床是镍矿也是铜矿的重要矿床类型。磁黄铁矿，镍黄铁矿、黄铜矿是这类矿床的主要金属矿物。它们的某些矿物学特征，特别是微量元素Ｃｏ／Ｎｉ比值，与其他铜矿类型明显不同，这三种矿物组成不同于任何其他铜矿类型的典型矿物共生组合， 形成特殊的海绵损铁状、球滴状构造。 相似文献
2.
塔里木克拉通东北缘坡北、磁海等地二叠纪幔源岩浆活动形成了镍钴硫化物矿床和铁钴氧化物矿床，两者赋矿镁铁 超镁铁岩体的年龄相近(290~260 Ma)，主、微量元素和Sr Nd Hf同位素组成相似，分配系数接近的微量元素比值分布于相同趋势线，揭示两者岩浆源区相同，可能为俯冲板片流体交代的亏损地幔或软流圈地幔。两类矿床镁铁 超镁铁质岩中Co与Ni含量正相关，Co主要富集在基性程度高的岩石中；块状硫化物与磁铁矿矿石中Co与Ni相关性差，Co和Ni具有不同的富集机制，Co热液富集作用明显。北山镁铁 超镁铁杂岩体是地幔柱相关软流圈上涌，诱发俯冲板片交代的亏损岩石圈地幔发生部分熔融，形成的高镁母岩浆演化过程中经历壳源混染、硫化物饱和富集镍钴形成铜镍钴硫化物矿床，富铁母岩浆氧逸度高、富水，岩浆分离结晶磁铁矿、叠加热液作用富集钴，形成铁钴氧化物矿床。 相似文献
3.
The Ni-Co-(PGE) sulfide deposits of the Thompson Nickel Belt (TNB) in Northern Manitoba, Canada are part of the fifth largest nickel camp in the world based on contained nickel; past production from the TNB deposits is 2500 kt Ni. The Thompson Deposit is located on the eastern and southern flanks of the Thompson Dome structure, which is a re-folded nappe structure formed during collision of the Trans-Hudson Orogen with the Canadian Shield at 1.9–1.7 Ga. The Thompson Deposit is almost entirely hosted by P2 member sulfidic metasedimentary rocks of the Paleoproterozoic Ospwagan Group. Variably serpentinised and altered dunites, peridotites and pyroxenites contain disseminated sulfides and have a spatial association with sediment-hosted Ni sulfides which comprise the bulk of the ore types. These rocks formed from rift-related komatiitic magmas that were emplaced at 1.88 Ga, and subsequently deformed by boudinage, thinning, folding, and stacking.Disseminated sulfide mineralization in the large serpentinised peridotite and dunite intrusions that host the Birchtree and Pipe Ni-Co sulfide deposits typically has 4–6 wt% Ni in 100% sulfide. The disseminated sulfides in the less abundant and much smaller boudinaged serpentinised peridotite and dunite bodies associated with the Thompson Deposit have 7–10 wt% Ni in 100% sulfide. The majority of Thompson Mine sulfides are hosted in the P2 member of the Pipe Formation which is a sulfidic schist developed from a shale prololith; the mineralization in the schist includes both low Ni tenor (<1 wt% Ni in sulfide) and barren sulfide (<200 ppm Ni) and a Ni-enriched sulfide with 1–18 wt% Ni in 100% sulfide. The semi-massive and massive sulfide ores show a similar range in Ni tenor to the metasediment-hosted mineralization, but there are discrete populations with maximum Ni tenors of ∼8, 11 and 13 wt% Ni in 100% sulfide. The variations in Ni tenor are related to the Ni/Co ratio (high Ni/Co correlates with high Ni tenor sulfide) and this relationship is produced by the different Ni/Co ratios in sulfides with a range in proportions of pyrrhotite and pentlandite. Geological models of the ore deposit, host rocks, and sulfide geochemical data in three dimensions reveal that the Thompson Deposit forms an anastomosing domain on the south and east flanks of a first order D3 structure which is the Thompson Dome. In detail, a series of second order doubly-plunging folds on the eastern and southern flank control the geometry of the mineral zones. The position of these folds on the flank of the Thompson Dome is a response to the anisotropy of the host rocks during deformation; ultramafic boudins and layers of massive quartzite in ductile metasedimentary rocks control the geometry of the doubly-plunging F3 structures. The envelope of mineralization is almost entirely contained within the P2 member of the Pipe formation, so the deposit is clearly folded by the first order and second order D3 structures. The sulfides with highest Ni tenor (typically >13 wt% Ni in sulfide) define a systematic trend that mirrors the configuration of the second order doubly-plunging F3 structures on the flanks of the Dome. Although moderate to high Ni tenor mineralization is sometimes localized in fold hinges, more typically the highest Ni tenor mineralization is located on the flanks of the fold structures.There is no indication of the mineralogical and geochemical signatures of sedimentary exhalative or hydrothermal processes in the genesis of the Thompson ores. The primary origin of the mineralization is undoubtedly magmatic and this was a critical stage in the development of economic mineralization. Variations in metal tenor in disseminated sulfides contained in ultramafic rock indicate a higher magma/sulfide ratio in the Thompson parental magma relative to Birchtree and Pipe. The variation in Ni tenor of the semi-massive and massive sulfide broadly supports this conclusion, but the variations in metal tenor in the Thompson ores was likely created partly during deformation. The sequence of rocks was modified by burial and loading of the crust (D2 events) to a peak temperature of 750 °C and pressure of 7.5 kbar. The third major phase of deformation (D3) was a sinistral transpression (D3 event) which generated the dome and basin configuration of the TNB. These conditions allowed for progressive deformation and reformation of pyrrhotite and pentlandite into monosulfide solid solution as pressure and temperature increased; this process is termed sulfide kinesis. Separation of the ductile monosulfide solid solution from granular pentlandite would result in an effective separation of Ni during metamorphism, and the monosulfide solid solution would likely be spread out in the stratigraphy to form a broad halo around the main deposit to produce the low Ni tenor sulfide. Reformation of pentlandite and pyrrhotite after the peak D2 event would explain the broad footprint of the mineral system. The effect of the D3 event at lower pressure and temperature would have been to locally redistribute, deform, and repeat the lenses of sulfide.The understanding of the relationships between petrology, stratigraphy, structure, and geochemistry has assisted in formulating a predictive exploration model that has triggered new discoveries to the north and south of the mine, and provides a framework for understanding ore genesis in deformed terrains and the future exploration of the Thompson Nickel Belt. 相似文献
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5.
攀西红格钒钛磁铁矿矿田白草矿区发育富钴硫化物矿物,关于其成因和形成环境方面的研究较为薄弱。本文采用矿物学、矿物化学、地球化学等方法对其进行系统研究。矿石中主要富钴硫化物为磁黄铁矿（Po）、黄铁矿（Py）、镍黄铁矿（Pn）、硫钴镍矿（Se）。磁黄铁矿Co、Ni平均质量分数分别为0.21%、0.42%,Co/Ni平均值为1.10;黄铁矿Co、Ni平均质量分数分别为0.18%、0.29%,Co/Ni平均值为0.77;镍黄铁矿Co、Ni平均质量分数分别为2.67%、34.30%,Ni/Fe平均值为1.08、S/Fe平均值为1.91、M/S#平均值为1.13;硫钴镍矿Co、Ni平均质量分数分别为24.30%、22.90%,Co/Ni平均值为1.06。根据Po-Py矿物温度计,白草矿区富钴硫化物结晶温度在267~490℃之间,表明其形成于中高温的条件。通过与地幔包体镍黄铁矿S/Fe、M/S#特征值的对比,结合磁黄铁矿具有陨硫铁（Tr）同质多象晶体的特征,认为白草矿区硫化物具有地幔源的特征,说明成矿物质来源于地幔。白草矿区钴地球化学特征研究表明,在硫化物熔体分离过程中,钴迁移至单硫化物固溶体形成Po-Py固溶体,再由Po-Py固溶体中迁移至Pn、Se,形成了Se、Pn、Po-Py、Ccp（黄铜矿）中Co质量分数依次递减的现象。 相似文献
6.
西藏冈底斯成矿带南木林县浦桑果铜多金属矿床是新发现的大型铜多金属矿床,该矿床以品位高,成矿元素复杂为其特征。本文应用野外地质编录、显微镜鉴定、电子探针等手段对浦桑果矿床矿石矿物特征以及Co、Ni元素赋存状态进行了研究。矿石矿物主要由黄铜矿、方铅矿、闪锌矿、铜蓝等组成。矿石中的有用元素除了铜、铅锌、银外,钴、镍元素是伴生有益组分,矿石中主要Co-Ni元素独立矿物为镍辉砷钴矿。通过电子探针分析,Co元素含量平均为17.87%,Ni元素含量平均12.66%,Co-Ni元素同时以类质同象置换铁的形式赋存于金属硫化物中,黄铜矿平均含Co0.04%、Ni0.08%,黄铁矿平均含Co0.40%、Ni0.20%,闪锌矿平均含Co0.14%、Ni0.06%,磁黄铁矿平均含Co0.79%、Ni0.18%等。Co-Ni元素作为重要的伴生矿产,对提高矿床综合利用价值,丰富青藏高原矿床类型,指导找矿工作部署具有重要的意义。 相似文献
7.
Yu. A. Poltavets V. N. Sazonov Z. I. Poltavets G. S. Nechkin 《Geochemistry International》2006,44(2):143-163
Relationships between noble-metal and oxide-sulfide mineralization during the origin of the Volkovsky gabbroic pluton are discussed on the basis of geochemical data and thermodynamic calculations. The basaltic magma initially enriched in noble metals (NM) relative to their average contents in mafic rocks, except for Pt, is considered to be a source of Pd, Pt, Au, and Ag in the gabbroic rocks of the Volkovsky pluton. The ores were formed with a progressive gain of NM in the minerals during the fractionation of the basaltic magma. The active segregation of NM in the form of individual minerals (palladium tellurides and native gold) hosted in titanomagnetite and copper sulfide ore occurred during the final stage of gabbro crystallization, when the residual fluid-bearing melt acquired high concentrations of Cu, Fe, Ti, and V, along with volatile P and S. Copper sulfides—bornite and chalcopyrite—are the major minerals concentrating NM; they contain as much as 22.65–25.20 ppm Pd and 0.74–1.56 ppm Pt; 4.39–8.0 ppm Au, and 127.2–142.6 ppm Ag, respectively. The copper ore and associated NM mineralization were formed at a relatively low sulfur fugacity, which was a few orders of magnitude (attaining 5 log units) lower than that of the pyrite-pyrrhotite equilibrium. The low sulfur fugacity and the close chemical affinity of Pd and Pt to Te precluded the formation of pyrrhotite, pyrite, and PGE disulfides. The major ore minerals and NM mineralization were formed within a wide temperature range (800–570°C), under nearly equilibrium conditions. Foreign elements (Ni, Co, and Fe) affected the thermodynamic stability of Pd and Pt compounds owing to the difference in their affinity to Te and to elements of the sulfur group (S, Se, and As). The replacement of Pd with Ni and Co and, to a lesser extent, with Pt and the replacement of Te with S, As, and Se diminish the stability field of palladium telluride. Comparison of Pd tellurides from copper sulfide ores at the Volkovsky and Baronsky deposits showed the enrichment of the former in Au, Sb, and Bi, while the latter are enriched in Pt, Ni, and Ag. The enrichment of Pd tellurides at the Baronsky deposit in Ni is correlated with the analogous enrichment of the host gabbroic rocks. 相似文献
8.
粤北大宝山铜多金属矿床一直存在燕山期岩浆热液成因和海西期火山喷流成因之争,争议的焦点在于块状、似层状硫化物矿体的成因。本文在全面开展矿区地质调查和钻探查证的基础上,对块状、似层状和脉状硫化物矿石中的黄铁矿和磁黄铁矿开展EPMA和LA-ICP-MS原位分析。测试结果表明,不同产状黄铁矿的平均分子式相似,分别为FeS_(1.98)、FeS_(1.99)和FeS_(1.98),似层状和脉状硫化物中磁黄铁矿的平均化学式为Fe_(0.886)S和Fe_(0.874)S,属形成温度相对较低单斜磁黄铁矿。与花岗岩岩浆热液标型黄铁矿相比,不同产状的黄铁矿和磁黄铁矿中Co、Ni、Mn、Se和Ge等元素以类质同象形式赋存,它们含量较低但稳定,Cu、Pb、Zn、Ag、Bi和Tl及Ga主要以微细矿物子晶形式存在,其含量丰富,但变化明显。从块状、似层状到脉状硫化物矿体,黄铁矿和磁黄铁矿中Co、Zn和Se的含量及Co/Ni值降低,而Cu、Pb、Ag、Bi等元素的含量明显升高。结合矿区次英安斑岩的产状和含矿性特征表明,大宝山矿床块状、似层状和脉状硫化物矿体都是次英安斑岩深部岩浆房产出的含矿流体在不同赋矿环境中的产物。 相似文献
9.
M. N. Çagatay 《Mineralium Deposita》1987,22(3):163-171
The Pancarli Ni-Cu mineralization is located in the metamorphic sequence of the Bitlis massif consisting of biotite gneiss, quartz-feldspar gneiss, amphibolite, and metagranitic rocks. The rocks are probably Precambrian in age and have been affected by regional amphibolite-facies metamorphism and by a later cataclasis. There is also evidence of an earlier eclogite-facies metamorphism. The Ni-Cu mineralization occurs as massive sulfide lenses aligned parallel to the penetrative foliation along various levels. The lenses are up to 3 m in length and 2 m in width. The host rock in the immediate vicinity of the orebodies is generally quartz-feldspar gneiss or more rarely quartz-feldspar gneiss and amphibolite. The mineral paragenesis of the ore consisting of pyrrhotite, pentlandite, and chalcopyrite and the low As and Co contents of the ore indicate an orhomagmatic origin of the mineraliza tion. The textures and chemistry of the spinel minerals in the Pancarli deposit together with Cu/(Cu+Ni) ratio of 0.29 of the ore suggest that the mineralization is genetically related to a basic magma. The only mafic rocks in the area are amphibolites that are characterized by a tholeiitic basaltic chemical composition. However, no imprignation and network ores are present in any of the amphibolite bodies. A model based on the segregation of a sulfide melt fraction from a basaltic magma in a magma chamber has been proposed. The subsequent and independent intrusions of the two fractions into the country rocks account for the absence of the impregnation and network ores in the amphibolites, and explain the similarities in geologic setting of the ore and amphibolites as well as their observed field relationships. Structural and textural features of the ores indicate that they have been subjected to regional metamorphism and the later cataclastic deformation that affected the country rocks. The author believes that the ores probably formed during the Pan-African orogenic development of the Bitlis massif in Late Precambrian time. In their present state, the Pancarli ores exhibit varying degrees of weathering with supergene assemblages.Formerly with the Middle East Technical University, Ankara, Turkey 相似文献
10.
喀拉通克铜镍矿床铂族元素地球化学特征及其成矿作用意义 总被引：16，自引：7，他引：9
喀拉通克铜镍矿床位于准噶尔板块北缘,矿区主要矿体赋存于Y1-Y3号岩体中。矿石构造类型为致密块状和浸染状两大类,其中前者与后者呈贯入接触,不同浸染状类型之间为过渡关系。岩石和矿石的PGE总量偏低,且以PPGE为主,IPGE含量较低。整体上岩石中的PGE含量显示随基性程度降低而变小。矿石中的PGE含量随硫化物含量增加增大,显示PGE主要分布于硫化物熔离形成的物相中。100%硫化物计算后,矿石PGE含量平均仅为573×10-9。各岩体中浸染状矿石PGE组成并无明显差异;岩石和矿石具有相似的PGE分配模式,均属于Pt-Pd配分型。岩石Ni/Cu-Pd/Ir关系以及岩石地球化学资料显示,形成喀拉通克岩体的初始岩浆为MgO含量较高的玄武质岩浆,属于PGE不亏损的岩浆。基于PGE不亏损的大陆拉斑玄武岩初始岩浆推算,喀拉通克矿床母岩浆明显亏损PGE,而深部硫化物熔离可能是导致母岩浆PGE亏损的主要原因。岩石和矿石Pd/Pt比值总体特征,岩石Cr与Ni、Ir、Ru和Rh相关性,以及硫同位素和岩石学资料分析表明,初始岩浆在地壳深部发生的橄榄石、铬铁矿等矿物的分离结晶作用,可能是促使硫过饱和与深部熔离的主要因素。IPGE与PPGE分异特征及其相关分析,结合矿床宏观地质特征,推断该矿床浸染状矿的成矿作用经历了初始岩浆（PGE不亏损）→橄榄石等矿物分离结晶→硫化物深部熔离→成矿母岩浆（PGE亏损）→上侵并结晶分异的成矿过程。块状矿则可能是这一过程中PGE亏损的成矿母岩浆相对滞后熔离形成的硫化物熔体贯入的结果。 相似文献
11.
吉林省红旗岭铜镍硫化物矿床矿石学特征 总被引：8，自引：0，他引：8
吉林省红旗岭地区目前正在开采的铜镍硫化物矿床共有5个,均属岩浆熔离型矿床.矿石矿物磁黄铁矿显微镜下可识别出3个同质多象变体:陨硫铁(tr)、六方磁黄铁矿(hpo)和单斜磁黄铁矿(pm).其基本结构主要为NiAs型,具有较高的Ni Cu Co含量,与相应的地幔包体成分相近.镍黄铁矿也有高温结晶型、低温出溶型和低温结晶型3种类型.电子探针微区成分分析显示了同种矿物的不同变种在成分上具有继承与关联性.在该矿床首次发现的辉砷镍矿的存在和黄铁矿的标形特征说明含S-As流体的交代作用在成岩后期普遍存在,为分析红旗岭铜镍硫化物矿床的成矿机制研究提供了矿物学信息. 相似文献
12.
捕虏体麻粒岩是了解下地壳形成和演化的重要样品。汉诺坝新生代玄武岩中的二辉麻粒岩捕虏体样品中富含各种硫化物相,主要类型有:①孤立产出的球状出溶硫化物;②矿物颗粒之间或颗粒内的粗晶硫化物;③次生硫化物包裹体群;④裂隙充填硫化物。电子探针分析表明,硫化物的矿物成分均为贫镍磁黄铁矿,(Ni+Co+Cu)/Fe(原子比)远小于0.2;(Fe+Cu+Co+Ni)/S(原子比)比地幔岩的磁黄铁矿小,多小于0.875,反映了一种S过饱和环境。各种产状的磁黄铁矿中Au、Ag都有一定的含量,其平均值分别为0.19%～0.22%(Au)、0.01%～0.02%(Ag),反映下地壳的麻粒岩化与金矿化的成因联系。磁黄铁矿的Ni、Co、Cu含量与S正相关,说明微量重金属元素与S具有同源的关系,由于地幔去气伴随S而进入下地壳。 相似文献
13.
The quasiequilibrium directed crystallization technique was used for experimental simulation of zoning characteristic of Cu-rich pyrrhotite-chalcopyrite and pyrrhotite-cubanite-mooihoekite-haycockite ores at the Oktyabr??sky deposit. Directed crystallization of samples I (Fe 32.55, Cu 10.70, Ni 5.40, S. 51.00, Pt = Pd = Rh = Ir= Au = Ag = 0.05 at %) and II (Fe 33.74, Cu 15.94, Ni 1.48, S. 48.75, Pt = Pd = 0.05 at %) was performed. These samples approximate average composition of the ore. Monosulfide (mms) and intermediate (iss) solid solutions progressively crystallized from the melt. The curves of ore element distribution in samples have been drawn. The partition coefficients (k) of ore elements between solid solutions and sulfide melt have been determined depending on melt composition. The paths of melt, mss, and iss compositions are supplemented by tie lines connecting compositions of equilibrium liquid and solid phases. The phase composition of samples after cooling was studied using an optical microscope, XRD, and microprobe. The zoning of sample I is described by the following sequence of phases: monoclinic pyrrhotite ?? hexagonal pyrrhotite + tetragonal chalcopyrite ?? tetragonal and cubic chalcopyrite + pentlandite + bornite. Crystallized sample II consists of four zones: (1) hexagonal pyrrhotite and isocubanite; (2) hexagonal pyrrhotite, cubanite, and pentlandite; (3) low-S pc-phase close to haycockite and pentlandite; and (4) mooihoekite, pentlandite, and bornite mixtures. This sequence corresponds to the secondary zoning, which reflects both the primary fractionation of components and the solid-phase reactions during cooling of the crystallized sample. The Rh, Ru, and Ir partition coefficients between mss and melt have been measured, and speciation of PGM in samples has been identified. The results obtained are compared with typical natural Cu-rich sulfide ore of the Oktyabr??sky deposit. 相似文献
14.
V.V. Ryabov O.N. Simonov S.G. Snisar A.A. Borovikov 《Russian Geology and Geophysics》2018,59(8):945-961
The source of sulfur in giant Norilsk-type sulfide deposits is discussed. A review of the state of the problem and a critical analysis of existing hypotheses are made. The distribution of δ34S in sulfides of ore occurrences and small and large deposits and in normal sedimentary, metamorphogenic, and hypogene sulfates is considered. A large number of new δ34S data for sulfides and sulfates in various deposits, volcanic and terrigenous rocks, coals, graphites, and metasomatites are presented. The main attention is focused on the objects of the Norilsk and Kureika ore districts. The δ34S value varies from -14 to + 22.5‰ in sulfides of rocks and ores and from 15.3 to 33‰ in anhydrites. In sulfide-sulfate intergrowths and assemblages, δ34S is within 4.2-14.6‰ in sulfides and within 15.3-21.3‰ in anhydrites. The most isotopically heavy sulfur was found in pyrrhotite veins in basalts (δ34S = 21.6‰), in sulfate veins cutting dolomites (δ34S = 33‰), and in subsidence caldera sulfates in basalts (δ34S = 23.2-25.2‰). Sulfide ores of the Tsentral’naya Shilki intrusion have a heavy sulfur isotope composition (δ34S = + 17.7‰ (n = 15)). Thermobarogeochemical studies of anhydrites have revealed inclusions of different types with homogenization temperatures ranging from 685 °C to 80 °C. Metamorphogenic and hypogene anhydrites are associated with a carbonaceous substance, and hypogene anhydrites have inclusions of chloride-containing salt melts. We assume that sulfur in the trap sulfide deposits was introduced with sulfates of sedimentary rocks (δ34S = 22-24‰). No assimilation of sulfates by basaltic melt took place. The sedimentary anhydrites were “steamed” by hydrocarbons, which led to sulfate reduction and δ34S fractionation. As a result, isotopically light sulfur accumulated in sulfides and hydrogen sulfide, isotopically heavy sulfur was removed by aqueous calcium sulfate solution, and “residual” metamorphogenic anhydrite acquired a lighter sulfur isotope composition as compared with the sedimentary one. The wide variations in δ34S in sulfides and sulfates are due to changes in the physicochemical parameters of the ore-forming system (first of all, temperature and Pch4) during the sulfate reduction. The regional hydrocarbon resources were sufficient for large-scale ore formation. 相似文献
15.
The Laloki and Federal Flag deposits are two of the many (over 45) polymetallic massive sulfide deposits that occur in the Astrolabe Mineral Field, Papua New Guinea. New data of the mineralogical compositions, mineral textures, and fluid inclusion studies on sphalerite from Laloki and Federal Flag deposits were investigated to clarify physiochemical conditions of the mineralization at both deposits. The two deposits are located about 2 km apart and they are stratigraphically hosted by siliceous to carbonaceous claystone and rare gray chert of Paleocene–Eocene age. Massive sulfide ore and host rock samples were collected from each deposit for mineralogical, geochemical, and fluid inclusion studies. Mineralization at the Laloki deposit consists of early‐stage massive sulfide mineralization (sphalerite‐barite, chalcopyrite, and pyrite–marcasite) and late‐stage brecciation and remobilization of early‐stage massive sulfides that was accompanied by late‐stage sphalerite mineralization. Occurrence of native gold blebs in early‐stage massive pyrite–marcasite‐chalcopyrite ore with the association of pyrrhotite‐hematite and abundant planktonic foraminifera remnants was due to reduction of hydrothermal fluids by the reaction with organic‐rich sediments and seawater mixing. Precipitation of fine‐grained gold blebs in late‐stage Fe‐rich sphalerite resulted from low temperature and higher salinity ore fluids in sulfur reducing conditions. In contrast, the massive sulfide ores from the Federal Flag deposit contain Fe‐rich sphalerite and subordinate sulfarsenides. Native gold blebs occur as inclusions in Fe‐rich sphalerite, along sphalerite grain boundaries, and in the siliceous‐hematitic matrix. Such occurrences of native gold suggest that gold was initially precipitated from high‐temperature, moderate to highly reduced, low‐sulfur ore fluids. Concentrations of Au and Ag from both Laloki and Federal Flag deposits were within the range (<10 ppm Au and <100 ppm Ag) of massive sulfides at a mid‐ocean ridge setting rather than typical arc‐type massive sulfides. The complex relationship between FeS contents in sphalerite and gold grades of both deposits is probably due to the initial deposition of gold on the seafloor that may have been controlled by factors such as Au complexes, pH, and fO2 in combination with temperature and sulfur fugacity. 相似文献
16.
岩浆铜镍矿床100%硫化物中的Ni含量与赋矿岩石和成矿过程紧密相关,记录岩浆成分、分异程度与硫化物演化过程。硫化物异常高镍(高镍硫化物)往往被认为与科马提质岩浆或者后期热液作用密切相关。近年研究结合勘查证实,赋含高镍硫化物的矿床(高镍铜镍矿床)不仅限于科马提岩,还与苦橄质、玄武质岩浆有关,另外,热液富集作用并不是必要因素。本文总结了世界上高镍铜镍矿床的基本特征和形成机制,分析提出了不同机制的判别标志,并展望了其勘查前景。详细对比高镍铜镍矿床的产出环境、赋矿岩相、矿石特征、矿物组合等特征,该类矿床往往产于大陆裂谷和造山带环境,与基性程度较高的岩浆有关,以橄榄岩赋矿为主,含镍硫化物组合主要为镍黄铁矿-磁黄铁矿-黄铜矿组合,少数为针镍矿-镍黄铁矿-黄铁矿组合。科马提岩相关矿床可将Ni含量大于16%的硫化物定义为高镍硫化物,苦橄质-玄武质岩浆相关矿床的硫化物可分为高镍硫化物(Ni10%)、中镍硫化物(5%～10%)和富铜硫化物(Ni5%,CuNi)。原生高镍硫化物可由富镍岩浆熔离、硫化物从橄榄石中吸取Ni、硫化物结晶分异、硫化物与硫不饱和岩浆反应等机制形成。苦橄质-玄武质岩浆相关的矿床,硫化物与橄榄石的Fe-Ni交换反应是高镍硫化物形成的重要机制。辉石岩源区地幔部分熔融形成富镍岩浆是否为高镍硫化物形成的必要条件尚存争议。不同机制形成的高镍硫化物具有迥异的岩石-矿物组合和地化特征。硫化物矿物组合、橄榄石成分(Fo值、Ni含量、Fo值-Ni含量的相关性)、伴生元素(铜、铂族元素)丰度-配分模式等特征可作为区分不同高镍硫化物形成机制的有效指标。我国新疆黄山南、坡一和青海夏日哈木矿床(部分浸染状矿化橄榄岩)以赋含高镍硫化物为特征,新疆喀拉通克矿床的硫化物则以富铜为特征,中国其余矿床的硫化物均属中镍硫化物。目前研究指示中国的高镍铜镍矿床与母岩浆相对富镍、硫化物与橄榄石Fe-Ni交换作用密切相关,后者可使硫化物Ni含量提升3%～5%。在铜镍矿床勘查方面,稀疏-中等浸染状高镍硫化物矿石即可达到工业品位,稠密浸染状-块状高镍硫化物矿石可达到很高的Ni品位(10%),是高品位镍矿勘查的一个重要方向。造山带环境富水、相对高氧逸度(可高达QFM+1)的岩浆可能是形成高镍硫化物的有利条件,该环境橄榄石Fo值较高(87mol%)的岩体有利于形成高镍硫化物。 相似文献
17.
The platinum-group elements (PGE) in base metal sulfides (BMS) of the Merensky reef are mostly close to the detection limit
of the proton microprobe. The only phase that accommodates appreciable PGE is pentlandite. Total average PGE plus Au grades
of the sulfide fraction of the Merensky reef are about 500 ppm. We estimate the modal proportions of the major BMS to be around
53 percent pyrrhotite, 25 percent pentlandite, and 22 percent chalcopyrite (ignoring minor phases). Using this estimate, we
calculate by how much the sulfides are oversaturated with respect to individual PGE. With respect to Pt, the sulfides are
many times oversaturated, i.e., nearly all Pt occurs as discrete PGE phases. With regard to Pd the sulfides are oversaturated
by about a factor of two. The Ru and Rh levels are at and below saturation levels. Available experiments suggest that the
entire PGE content of the sulfide fraction can easily be accommodated in solid solution in BMS at temperatures as low as 500°C.
The fact that the BMS are oversaturated with most PGE thus indicates that the sulfides have continued to exsolve PGE below
that temperature. Calculated sulfur fugacities indicate that f
S2 is controlled by silica activity, as expected in high-temperature ores, suggesting that metal/sulfur ratios of the ore may
not have changed much since complete solidification of the intercumulus silicate melt of the Merensky reef. All sulfides investigated
have cooled below the maximum temperature of pentlandite-pyrite coexistence, which experiments place at 250±30°C. Final closure
temperatures of the sulfide-PGE mineral assemblages, approximated by extrapolating the pentlandite-pyrrhotite solvus beyond
its experimentally determined range, are possibly as low as 80 to 90°C.
Received: 25 April 1995/Accepted: 5 September 1995 相似文献
18.
Peter C. Lightfoot Reid R. Keays Dawn Evans-Lamswood Robert Wheeler 《Mineralium Deposita》2012,47(1-2):23-50
The Voisey’s Bay deposit is hosted in a 1.34-Ga intrusion composed of troctolite, olivine gabbro, and ferrogabbro. The sulfide mineralization is associated with magmatic breccias that are enveloped by weakly mineralized olivine gabbros and troctolites, and also occurs as veins along structures in adjacent paragneiss. A dyke is connected to the base of the north wall of the Eastern Deeps Intrusion, and the entry point of this dyke into the chamber is the locus of the Eastern Deeps nickel sulfide deposit. A detailed exploration in the area between the Eastern Deeps and the Ovoid has shown that these intrusions and ore deposits are connected by a splayed dyke. The Eastern Deeps Deposit is surrounded by a halo of moderately to weakly mineralized variable-textured troctolite (VTT) that reaches a maximum thickness above the axis of the Eastern Deeps Deposit along the northern wall of the Eastern Deeps Intrusion. The massive sulfides and breccia sulfides are petrologically and chemically different when compared to the disseminated sulfides in the VTT, and there is a marked break in Ni tenor of sulfide between the two. Sulfides hosted in the dyke tend to have low metal tenors ([Ni]100?=?2.5–3.5%), sulfides in Eastern Deeps massive and breccia ores have intermediate Ni tenors ([Ni]100?=?3.5–4%), and disseminated sulfides in overlying rocks have high Ni tenors ([Ni]100?=?4–8%). Four principal processes control the compositions of the Voisey’s Bay sulfides. Coarse-grained loop-textured ores consisting of pyrrhotite crystals separated by chalcopyrite and pentlandite exhibit a two orders of magnitude variation in the Pd/Ir ratio which is due to mineralogical variations where pentlandite is enriched in Pd and Ir is dispersed throughout the mineral assemblage. A decrease in Ir and Rh from the margin of the Ovoid toward cubanite-rich parts at the central part of the Ovoid is consistent with fractionation of the sulfide from the margins toward the center of the Ovoid. The Ovoid ores have higher Ni and Pd tenor than the Eastern Deeps massive sulfides; this is consistent with both a higher R factor and greater degree of silicate parental magma evolution in the Ovoid than the Eastern Deeps. The disseminated sulfides surrounding the Eastern Deeps deposit have some of the highest Ni and Pd tenors at Voisey’s Bay, which are indicative of not only more primitive magmas but also higher R factors than the Ovoid or the Eastern Deeps. VTT and normal-textured troctolite of the Eastern Deeps that contain trace sulfide have 0.1–3?ppb Pt and 0.1–3?ppb Pd, whereas weakly to heavily mineralized variable troctolites in the same unit have one to two orders of magnitude higher abundances of Pt and Pd. Troctolites and olivine gabbros from other parts of the Voisey’s Bay Intrusion and other Nain Plutonic Suite Intrusions, including the Kiglapait, Newark Bay, Barth Island, Mushua, and Nain Bay South Intrusion, also have low platinum group element abundances. Although it is possible that this is a signature of a widespread sulfide saturation event that pre-dated ore formation at Voisey’s Bay, it is more likely that platinum group element (PGE) depletion is a product of the source melting process where low degrees of melting resulted in the retention of PGE in the mantle source. If so, this indicates that PGE depletion should be used with caution as an exploration tool in the Nain Plutonic Suite. 相似文献
19.
Mantle xenoliths are common in the Cenozoic basalts of the Changbaishan District,Jilin Province,China.Sulfide assemblages in mantle minerals can be divided into three types:isolated sulfide grains,sulfide-meh inclusions and filling sulfides in fractures.Sulfide-meh inclusions occur as single-phase sulfides,sulfide-silicate melt,and CO_2-sulfide-silicate melt inclusions. Isolated sulfide grains are mainly composed of pyrrhotite,but cubanite was found occasionally.Sulfide-meh inclusions are mainly composed of pontlandite and MSS,with small amounts of chalcopyrite and talnakhite.The calculated distribution coefficient K_(D3)for lherzolite are similar to that of mean experimental value.The bulk sulfides in lherzolite were in equilibrium with the enclosing minerals, indicating immiscible sulfide melts captured in partial melting of upper mantle.Sulfide in fractures has higher Ni/Fe and(Fe Ni)/S than those of sulfide melt inclusions.They might represent later metasomatizing fluids in the mantle.Ni/Fe and(Fe Ni)/S increase from isolated grains,sulfide inclusions to sulfides in fractures.These changes were not only affected by temperature and pressure,hut by geochemistry of Ni,Fe and Cu,and sulfur fugacity as well. 相似文献
20.
《Chemie der Erde / Geochemistry》2023,83(2):125954
Magmatic sulfide liquids are effective at concentrating a range of metals. Within magmatic sulfide systems pentlandite, an exsolution product of monosulfide solid solution (MSS), is the primary host of Ni, Co and significant concentrations of Pd. Over the last decade, LA-ICP-MS mapping has revealed non-uniform metal distributions and complexity to the metal patterns such as zonation and the linear alignment of elements. Whereas the compatibility and partitioning behavior of chalcophile elements during sulfide fractionation are well constrained, there is little knowledge on the crystallographic control exerted on metal distributions.In this study, LA-ICP-MS mapping of globular sulfides from the Crystal Lake Intrusion, Ontario (Canada), is complimented by EBSD analysis, revealing a strong crystallographic control on both the concentration of metals and pentlandite exsolutions. Elements considered incompatible in the high temperature monosulfide solid solution (MSS) phase (e.g., Cr, V, As, Pb, Ag, Bi and Pd) are preserved as a microfabric, showing preferential concentration in association with the (0001) basal plane of pyrrhotite and adjacent pentlandite. Where the [0001] axis is viewed perpendicular to the cut surface, the microfabric is considered to be an intersection lineation between the basal (0001) plane and the surface of the cut section.Pentlandite textures described in magmatic sulfide deposits include granular, fan and laths/blades. Our observations indicate that marginal pentlandite exsolutions, are in optical continuity with granular exsolutions, providing insights into the growth of pentlandite at MSS grain boundaries. We conclude that all pentlandite forms are crystallographically controlled by the hexagonal mineral system of MSS/pyrrhotite, with the [0001] c-axis of pyrrhotite corresponding to the 〈111〉 axis of pentlandite. This axis also acts as a twinning rotation axis for the two identified pentlandite orientations. Fan and lath textured exsolutions are considered geometrically equivalent structures, being reconstructed as flat disc–shapes developed parallel to the basal (0001) plane of pyrrhotite, which acts as a preferred nucleation site. A network of low-angle grain boundaries are recognized as hexagonal or rectangular structures within pyrrhotite, with the morphology shown to be dependent on the orientation of the crystals. As these features are again geometric equivalents, they can be reconstructed as intragrain hexagonal prisms. We speculate due to their localized development, that they could represent a plastic response of the pyrrhotite to accommodate the increase in volume suggested to be associated with late pentlandite exsolutions and thus are the result of static lattice recovery.The microstructural and trace element observations presented here provide new context to some of the common textural features of magmatic sulfide deposits, while importantly highlighting the strong crystallographic control on both metal distributions and sulfide textures. This study also importantly recognizes the dominance of hexagonal pyrrhotite within the ores of the Crystal Lake Intrusion and likely other magmatic sulfide deposits. This has implications for mineral processing as its non-magnetic properties can result in dilution of Ni-Cu-PGE ores and thus requires special attention for the flotation strategy. 相似文献