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1.
《International Geology Review》2012,54(7):1062-1068
The mineralized area (fig. 1) lies inside a large dunitic body. The sulfides are small phenocrysts of pentlandite (with chalcopyrite and pyrrhotite); chromite is generally present and metasomatic magnetite is locally abundant, as replacer of the sulfides. A genetic connection of the sulfides with the dunites is indicated. There is no evidence of any epigenetic segregation of the ore minerals and hence no reason to expect presence of economic ores in this particular part of the massif. — V.P. Sokoloff 相似文献
2.
文章专门讨论与特定成岩作用伴生的铬、铂和硫化物矿床形成的内生因素。该类成岩作用对矿石富集有显著影响。矿床的巨大规模起因于与广泛强烈的成岩过程有关的特殊的成矿作用。这些作用导致产在超基性杂岩中的特殊纯橄榄岩（铬矿石）、基性超基性层状侵入体中的低硫层和铁镁橄榄石纯橄榄岩（铂族金属矿床）的形成,以及富铁火成分异岩的透岩浆硫化作用（Ｃｕ Ｎｉ硫化物和Ｃｕ Ｚｎ Ｐｂ硫化物矿石）。还根据巨型矿床的成因模型提出了矿物学岩石学的找矿标志 相似文献
3.
黔西北铅锌矿床REE特征及其意义 总被引：8，自引：4，他引：8
据各类样品的REE组成，研究了三个矿床矿石，恂变围岩及其原岩REE地球化学特征，计算出近似的成矿流体REE成分，讨论了REED 成矿（蚀变）过程中的地球化学行为，结合其他地质地球化学特征认为成矿物质主体是来源于下部的富金属流体，蚀变围岩的REE模式可作为寻找盲矿标志。 相似文献
4.
针对北秦岭丹凤地区产铀花岗岩的区域地层、赋矿围岩、蚀变岩和铀矿石进行稀土元素地球化学研究,结果表明:各类样品具有大体类似的LREE富集及Eu负异常的稀土配分模式,表明它们之间稀土元素特征具有继承性;赋矿黑云母二长花岗岩与区域地层(丹凤岩群变质基性火山岩)稀土元素特征指示,二者均形成于岛弧环境;蚀变花岗岩和铀矿石主要继承了赋矿花岗岩的特征。各类样品Y/Ho值变化范围狭窄,为25.09~33.46,显示它们具有共同的源区。铀矿石具有最高的wB(∑HREE),且与铀矿石的品位存在正相关关系,暗示HREE与铀的迁移具有同步性。 相似文献
5.
On the basis of a representative collection of ultramafic rocks and chromite ores and a series of technological samples from the largest (Central and Western) deposits in the Rai-Iz massif of the Polar Urals and the Almaz-Zhemchuzhina and Poiskovy deposits in the Kempirsai massif of the southern Urals, the distribution and speciation of platinum-group elements (PGE) in various type sections of mafic-ultramafic massifs of the Main ophiolite belt of the Urals have been studied. Spectral-chemical and spectrophotometric analyses were carried out to estimate PGE in 700 samples of ultramafic rocks and chromite ores; 400 analyses of minerals from rocks, ores, and concentrates and 100 analyses of PGE minerals (PGM) in chromite ores and concentrates were performed using an electron microprobe. Near-chondritic and nonchondritic PGE patterns in chromitebearing sections have been identified. PGE mineralization has been established to occur in chromite ore from all parts of the mafic-ultramafic massifs in the Main ophiolite belt of the Urals. The PGE deposits and occurrences discovered therein are attributed to four types (Kraka, Kempirsai, Nurali-Upper Neiva, and Shandasha), which are different in mode of geological occurrence, geochemical specialization, and placer-forming capability. Fluid-bearing minerals of the pargasite-edenite series have been identified for the first time in the matrix of chromite ore of the Kempirsai massif (the Almaz-Zhemchuzhina deposit) and Voikar-Syn’ya massif (the Kershor deposit). The PGE grade in various types of chromite ore ranges from 0.1–0.2 to 1–2 g/t or higher. According to technological sampling, the average PGE grade in the largest deposits of the southeastern ore field of the Kempirsai massif is 0.5–0.7 g/t. Due to the occurrence of most PGE as PGM 10–100 mm in size and the proved feasibility of their recovery into nickel alloys, chromites of the Kempirsai massif can be considered a complex ore with elevated and locally high Os, Ir, and Ru contents. The Nurali-Upper Neiva type of ore is characterized by small-sized primary deposits, which nevertheless are the main source of large Os-Ir placers in the Miass and Nev’yansk districts of the southern and central Urals, respectively. 相似文献
6.
Mineralogy and geochemistry of banded iron formation and iron ores from eastern India with implications on their genesis 总被引：1，自引：0，他引：1
The geological complexities of banded iron formation (BIF) and associated iron ores of Jilling-Langalata iron ore deposits,
Singhbhum-North Orissa Craton, belonging to Iron Ore Group (IOG) eastern India have been studied in detail along with the
geochemical evaluation of different iron ores. The geochemical and mineralogical characterization suggests that the massive,
hard laminated, soft laminated ore and blue dust had a genetic lineage from BIFs aided with certain input from hydrothermal
activity. The PAAS normalized REE pattern of Jilling BIF striking positive Eu anomaly, resembling those of modern hydrothermal
solutions from mid-oceanic ridge (MOR). Major part of the iron could have been added to the bottom sea water by hydrothermal
solutions derived from hydrothermally active anoxic marine environments. The ubiquitous presence of intercalated tuffaceous
shales indicates the volcanic signature in BIF.
Mineralogical studies reveal that magnetite was the principal iron oxide mineral, whose depositional history is preserved
in BHJ, where it remains in the form of martite and the platy hematite is mainly the product of martite. The different types
of iron ores are intricately related with the BHJ. Removal of silica from BIF and successive precipitation of iron by hydrothermal
fluids of possible meteoric origin resulted in the formation of martite-goethite ore. The hard laminated ore has been formed
in the second phase of supergene processes, where the deep burial upgrades the hydrous iron oxides to hematite. The massive
ore is syngenetic in origin with BHJ. Soft laminated ores and biscuity ores were formed where further precipitation of iron
was partial or absent. 相似文献
7.
云南会泽铅锌矿床脉石矿物方解石REE地球化学 总被引：19，自引：5，他引：19
方解石是云南会泽铅锌矿床最重要的脉石矿物，原生矿石中三种产状（即团块状状、团斑状和脉状）方解石的REE含量、有关参数和配分模式都有一定的差异，但不同产状方解石之间以及同种产状方解石的REE地球化学特征具有连续变化规律。分析结果表明：矿区原生矿石中三种产状方解石为同源不同阶段形成的产物；矿床成矿流体具有多来源特征，地幔流体在成矿流体形成过程中具有重要作用；成矿流体在演化过程REE含量逐渐降低；成矿环境由相对还原向相对氧化变化。 相似文献
8.
四川西部呷村银多金属矿床稀土地球化学研究 总被引：3，自引：0，他引：3
呷村矿床是我国典型的含金富银多金属海相火山岩型块状硫化物矿床。通过对该矿床岩石及矿石的稀土地球化学研究，结合硫铅同位素的工作，提出成矿热液为高温酸性、富C1溶液，其稀土特征为富轻稀土，具明显正铕异常。在蚀变过程中，流体／岩石比值相对较主，稀土元素在成矿流体－围岩间具有明显的带进或带出。正铕异常产生最可能的来源是该区深部火山岩富含长石，热水溶液与火山岩发生水岩反应使长石释放出铕，使热水溶液具正Eu异常，这方面也反映该矿床成矿物质与深部火山岩有密切关系。弱负铈异常是成矿流体继承海水Ce亏损的结果。层状矿石中Eu异常变化较大，且其中LREE的含量变化大于HREE。主要原因可能是矿石中矿物组成和形成条件的变化。呷村矿床的成矿模式可以认为是火山喷发过程中产生了岩浆热液，并带出了硫和金属元素，并在海底附近快速沉淀形成。成矿后为正常深海沉积岩覆盖。 相似文献
9.
J. Proenza F. Gervilla J. Melgarejo O. Vera P. Alfonso A. Fallick 《Mineralium Deposita》2001,36(7):658-669
The Potosí Mine is located in the Moa-Baracoa massif in the easternmost part of the Cuban Ophiolitic Belt. Chromite mineralization occurs within the mantle-crust transition zone. Two events of magma intrusion overprint the chromitite bodies: one gave rise to the crystallization of pegmatitic olivine-norite dikes, and the other produced pegmatitic gabbro dikes. Sulfide-poor chromite ores, brecciated chromite ores, and sulfide-rich chromite ores can be distinguished in the different chromitite bodies. Sulfide-poor ores represent more than 80 vol% of the chromitites. This type occurs far from the zones intruded by pegmatitic gabbro dikes and shows petrographic and chemical features similar to other chromitite bodies described in the Moa-Baracoa massif. Brecciated chromite ores occur within pegmatitic gabbro dikes. In this type, chromite crystals occur included within chromian diopside and plagioclase. These silicates often contain droplet-like sulfide aggregates. Sulfide-rich ores are spatially associated to the contacts between sulfide-poor chromite and pegmatitic olivine-norite dikes. These ores mainly consist of recrystallized (coarse) chromite with interstitial pyrrhotite, pentlandite, cubanite, and chalcopyrite. Chromite from sulfide-rich ores exhibits TiO2, FeO, V2O3, MnO, and especially, Fe2O3 contents, higher than those of chromite from brecciated ores and much higher than those of chromite from sulfide-poor ores. The sulfide-rich ores are PGE-rich (up to 1,113 ppb of total PGE), and show nearly flat chondrite-normalized PGE patterns, slightly above 0.1 times chondritic values. Mineralogical and chemical data indicate that the chromite ores of the Potosí Mine were modified by the intrusions of olivine-norite and gabbro dikes. The interaction between pre-existing sulfide-poor chromite ores and the intruding volatile-rich silicate melts produced strong brecciation, partial dissolution, and recrystallization (coarsening) of chromite. The sulfide assemblage formed by fractionation of the immiscible sulfide melt segregated from the volatile-rich silicate melt that generated the pegmatitic olivine-norite. The segregation of the sulfide melt can be interpreted as the consequence of chemical interaction between intruding melts and the host chromite. The variable extent of this interaction produced chromite ores with variable sulfide ratios. The magmatic nature of the sulfide mineralization is supported by sulfur isotope data, which range from -0.4 to +0.9. Sulfide melt collected incompatible PGE (Rh, Pt, Pd) to produce the typical flat chondrite-normalized pattern of sulfide-rich chromite ores. 相似文献
10.
Metasomatic interactions between slab-derived melts and depleted mantle: Insights from xenoliths within Monglo adakite (Luzon arc, Philippines) 总被引：1，自引：0，他引：1
M. Gregoire S. Jego R.C. Maury M. Polve B. Payot R.A. Tamayo Jr. G.P. Yumul Jr. 《Lithos》2008,103(3-4):415-430
The Monglo adakite contains mafic and ultramafic xenoliths, which probably originated from the mantle section of an Early Cretaceous supra-subduction zone ophiolitic complex located within the Luzon arc crust. Spinel-bearing dunites are dominant among this xenolith collection and display evidence for three episodes of subduction-related melt percolation. The first one is evidenced by an undeformed clinopyroxene characterized by convex-upwards REE pattern. This clinopyroxene crystallized from a calc-alkaline basaltic magma, likely formed in the Cretaceous supra-subduction setting of the ophiolite. Then, two metasomatic events, evidenced by orthopyroxene-rich and amphibole-rich secondary parageneses, respectively, affected most of the spinel dunites. The opx-rich paragenesis is related to the circulation within the dunitic upper mantle of hydrous slab-derived melts similar to those affecting the mantle peridotite xenoliths from Papua New Guinea and Kamchatka. Finally the amphibole-rich veins are related to the interaction between the studied dunite xenoliths and the host adakite or an adakitic melt similar to it. 相似文献
11.
12.
The Zambales ophiolite is the major source of chromite ore in the Philippines. The chromitites are concordant cumulates and are associated with distinct chromitite-bearing sequences within the mantle peridotites. Refractory and metallurgical chromite deposits are spatially separated and related to different lithologic associations, which crystallized from different parental magmas. — Refractory chromite ores (30–44 wt% Cr2O3; 20–30 wt% Al2O3) are linked with the peridotite-troctolite-olivine gabbro lineage. Two main types were found: (1) Al-rich refractory ores associated with harzburgites and feldspathic periodotites and (2) more Cr-rich varieties associated with lherzolites. — Metallurgical chromite ores (45–53 wt% Cr2O3; 12–18 wt% Al2O3) are linked with the peridotite-pyroxenite-norite lineage. Two main types were also found: (1) Cr-rich metallurgical ores associated with orthopyroxenites and (2) more Al-rich varieties related to clinopyroxenites. — The chemical composition of chromite within the deposits varies depending on the chromite/silicate ratios of the ore types and grades continuously into accessory chrome spinels in the wall-rock peridotites. — The geochemistry of accessory chrome spinels in various peridotites and mafic cumulates depends on the mineralogical composition and the stratigraphic position of their host rocks.New address: BEB Erdgas und Erdöl GmbH, Riethorst 12, D-3000 Hannover 51The terms chrome-spinels and chromite are used as follows: 1. Chrome-spinel is only used for those occuring as accessory minerals in various ultramafic and mafic rocks (= accessory chrome-spinels). Their chemical composition has been determined only by microprobe analysis. — 2. Chromite is used for ore and ore deposits (=chromitites); the chemical composition has been determined by wet chemistry (AAS) or by microprobe analysis 相似文献
13.
A. P. Kozlov V. A. Chanturiya E. G. Sidorov N. D. Tolstykh Yu. M. Telegin 《Geology of Ore Deposits》2011,53(5):374-389
The results of mineralogical-technological studies of PGM mineralization in zonal mafic-ultramafic complexes of the Ural-Alaskan
type are given. All studied massifs in the Urals and Kamchatka are characterized by similar evolution of mineral assemblages.
The chromite (platinum-chromitite-dunite) and dunite (platinum-pegmatoid dunite) geological-economic types of small platinum
deposits and occurrences are separate enriched sites (ore shoots) of large-volume platinum ore deposits. These are rather
thick and extended zones of recrystallized dunites with attributes of high-temperature structural deformations and intense
fluid reworking. Low Pt grade in ore (<0.5 gpt) is determined by fine and very fine (grain size class — 80 μm) euhedral PGM
crystals distributed rather uniformly in ore mass. The high and occasionally anomalous Pt contents (up to 1 kgpt and higher)
are related to large xenomorphic segregations of PGM, which concentrate largely in the marginal parts of separate chromite
segregations. The significant part of productive Pt-bearing mineralization is hosted in olivine matrix of igneous rocks, so
that recovery of platinum cannot be associated only with separation of chromite ore. The direct gravity concentration of platinum
ore without preliminary separation of chromite concentrate is recommended as the main technique of platinum recovery. The
technological scheme provides for two-stage comminution of ore with between-cycle separation of coarse the PGM fraction into
the concentrate as a commodity product. The results obtained allow us to regard the aforementioned mineralization as a new
geological and economic type of lode platinum deposits, whose potential is comparable with active platinum reserves in the
complex Cu-Ni ores of the Noril’sk district. 相似文献
14.
Maria Economou-Eliopoulos 《Ore Geology Reviews》1996,11(6):363-381
Compilation of some new data on ophiolites for Greece and Yugoslavia, and published data from previous studies, indicate that platinum-group element (PGE) and gold concentrations in chromite ores are generally low, ranging from less than 100 ppb to a few hundred ppb. However, samples from several ophiolite complexes exhibit an enrichment (of a few ppm) (a) only in Os, Ir and Ru,(b) only in Pt and/or Pd or (c) in all PGE. This enrichment (up to 10s ppm) is mainly related with chromitites hosted in supra-Moho dunites and dunites of the uppermost stratigraphic levels of the mantle sequence and it seems to be local, independent of the chromitite major element composition and the chromite potential of the ophiolite complexes. The contents of PGE combined with less chalcophile elements (Ni, Co, Cu), the ratios of incompatible/compatible elements, and PGE-patterns provide evidence for discrimination between chromitites derived from primitive magmas and those derived from partially fractionated magmas, although they have a similar major element composition. Thus, they can be used for a stratigraphic orientation in the mantle sequence, and therefore for exploration targets. Moreover, PGE data offer valuable information for the evaluation of the chromite potential in ophiolite complexes. The most promising ophiolites seem to be those which apart from the petrological and geochemical characteristics indicating extensive degree of partial melting in the mantle source contain only one chromite ore type (the other type being only in small proportion) of limited compositional variation, in both major elements and PGE, low ratios of , while PGE-enriched chromitites in the mantle sequence are only occasionally present. In contrast, ophiolites which contain both high-Cr and -Al chromitites, and where their chalcophile element data implies relatively extensive fractionation trend are not good exploration targets for chromite ores, although they are related with a SSZ environment. 相似文献
15.
内蒙古黄岗梁锡铁多金属矿床层状夕卡岩的喷流沉积成因 总被引：6，自引：1，他引：6
内蒙古自治区黄岗梁矿床是大兴安岭中南段的一个大型Sn-Fe多金属矿床,燕山期火山侵入岩广泛出露,通过对矿床地球化学特征的系统研究,并结合矿床地质特征,得出的主要研究成果为:①与含微细浸染胶状锡的磁铁矿层共生的层状夕卡岩与海底火山活动关系密切,是一种很具特色的喷流岩;②REE地球化学特征表明,该矿床层状夕卡岩与典型岩浆热液接触交代夕卡岩存在较大差异,而与现代海底热流体和喷流型矿床及其共生的热水沉积岩有较大的相似性,应属热水喷流成因;③层状夕卡岩的碳、氧同位素组成关系可与许多沉积喷流型块状硫化物矿石及其共生的喷流岩相对比,暗示了两者具有相似的形成机理。 相似文献
16.
津巴布韦大岩墙中的层状铬铁矿储量丰富,易于开采且矿石质量较高。本文通过对产自不同次岩浆房的铬铁矿样品进行电子探针分析,表明铬铁矿的地球化学数据较为集中,TiO_2含量较低,Mg#变化不大,Cr#逐渐升高,表现出随着温度和压力的降低,铬铁矿化学成分向着富Cr和富Fe的方向演变。综合分析表明该层状铬铁矿是在拉张环境背景下,由于深大断裂诱发深部地幔发生部分熔融,形成的基性-超基性岩浆快速上涌,随着温度和压力的逐渐降低,由分离结晶作用导致铬铁矿矿物的堆晶沉淀形成层状矿体。 相似文献
17.
《地学前缘(英文版)》2016,7(3)
Bayan Obo ore deposit is the largest rare-earth element(REE) resource,and the second largest niobium(Nb) resource in the world.Due to the complicated element/mineral compositions and involving several geological events,the REE enrichment mechanism and genesis of this giant deposit still remains intense debated.The deposit is hosted in the massive dolomite,and nearly one hundred carbonatite dykes occur in the vicinity of the deposit.The carbonatite dykes can be divided into three types from early to late:dolomite,co-existing dolomite-calcite and calcite type,corresponding to different evolutionary stages of carbonatite magmatism based on the REE and trace element data.The latter always has higher REE content.The origin of the ore-hosting dolomite at Bayan Obo has been addressed in various models,ranging from a normal sedimentary carbonate rocks to volcano-sedimentary sequence,and a large carbonatitic intrusion.More geochemical evidences show that the coarse-grained dolomite represents a Mesoproterozoic carbonatite pluton and the fine-grained dolomite resulted from the extensive REE mineralization and modification of the coarse-grained variety.The ore bodies,distributed along an E-W striking belt,occur as large lenses and underwent more intense fluoritization and fenitization.The first episode mineralization is characterized by disseminated mineralization in the dolomite.The second or main-episode is banded and/or massive mineralization,cut by the third episode consisting of aegirinerich veins.Various dating methods gave different mineralization ages at Bayan Obo,resulting in long and hot debates.Compilation of available data suggests that the mineralization is rather variable with two peaks at~1400 and 440 Ma.The early mineralization peak closes in time to the intrusion of the carbonatite dykes.A significant thermal event at ca.440 Ma resulted in the formation of late-stage veins with coarse crystals of REE minerals.Fluids involving in the REE-Nb-Fe mineralization at Bayan Obo might be REE-F-C02-NaCI-H20 system.The presence of REE-carbonates as an abundant solid in the ores shows that the original ore-forming fluids are very rich in REE,and therefore,have the potential to produce economic REE ores at Bayan Obo.the Bayan Obo deposit is a product of mantle-derived carbonatitic magmatism at ca.1400 Ma,which was likely related to the breakup of Columbia.Some remobilization of REE occurred due to subduction of the Palaeo-Asian oceanic plate during the Silurian,forming weak vein-like mineralization. 相似文献
18.
湖南沃溪金-锑-钨矿床成因的稀土元素地球化学证据 总被引：11，自引：0，他引：11
沃溪金-锑-钨矿床的稀土元素地球化学组成良好地反映了成矿作用的条件和过程,并为示踪矿床成因提供了有用的信息.以流体包裹体为代表的成矿溶液,以较高的稀土总量、显著的轻稀土富集和缺乏明显的铕异常为特征,代表了一种通过在碎屑沉积物柱中循环而萃取矿质的演化的海水热液.矿石相对于成矿流体(母液)富集重稀土而轻微亏损铕,反映了矿石沉淀过程中来自于海水的稀土元素掺合.同一矿层内由下往上,重稀土相对富集的程度逐渐增大而稀土总量则逐渐降低,表明随着热液化学沉淀作用的进行,海水掺合的影响逐渐增强.矿石的稀土元素组成,无论在分布模式还是在轻重稀土之间的分馏程度上,均与其他许多 Sedex型多金属矿床十分相似,暗示了这些矿床具有相似的成因机制.稀土元素地球化学特征支持矿床同生沉积成因的观点. 相似文献
19.
广西大厂层状花岗质岩石地质、地球化学特征及成因初探 总被引：1，自引：0，他引：1
在广西大厂拉么矿区黑云母花岗岩岩体周围的层状花岗质岩石,其地质产状、成岩时代、结构构造、矿物成分、化学成分及稀土元素、微量元素地球化学特征等方面与一般的交代岩不同,也与一般的岩浆成因花岗岩不同;成岩物质既有岩浆来源又有地层来源,反映了与笼箱盖岩体同源的岩汁或热液沿层交代泥盆系的成因特征。它与层状锡多金属矿体、层状夕卡岩及层状锌-铜矿体等共同构成燕山期酸性岩浆作用所形成的层状交代体系。 相似文献
20.
Chromitite occurrences in the Pindos ophiolite complex are located in elongated dunite bodies hosted in harzburgite of the mantle sequence, and show a compositional variation from high-Al to high-Cr type. Although the majority of the chromite ores is characterized by paucity in fluid inclusions, abundant fluid inclusions were found in chromite hosted by a coarse-grained pyroxenite dike at the Spanos Valley, Pindos complex. Chromite occurs in highly variable proportion in an orthopyroxene matrix or as inclusions in orthopyroxenes. Its composition is homogeneous and has an average Cr/(Cr+Al) ratio 0.73.The investigation of chromitites revealed the presence of primary and secondary fluid inclusions. The primary inclusions are of following types: Three-phase solid-liquid-gas, three-phase liquid-liquid-gas, two-phase liquid-gas and one-phase octahedron crystal-shaped. The secondary fluid inclusions are two-phase liquid-gas and mono-phase fluid inclusions.The presence of fluid inclusions in chromite aggregates hosted in orthopyroxenite dikes, in combination with the trace element contents in chromite concentrates and the mineralogical composition of the dikes may indicate that an aqueous phase separated from the magma. 相似文献