The Early Paleoproterozoic Monchegorsk layered mafite-ultramafite massif in the Kola Peninsula: Geology, petrology, and ore potential

The Early Paleoproterozoic Monchegorsk Complex is exposed over an area of 550 km² and comprises two layered mafite-ultramafite intrusions of different age: the Monchegorsk pluton of ultramafic and mafic rocks and the predominantly gabbroid Main Range Massif (also referred to as the Moncha-Chuna-Volch??i Tundras Massif), which are separated by a fault. Both massifs consists of intercalating cumulates (first of all, Ol ± Crt, Ol + Opx ± Crt, Opx, Opx + Pl ± Cpx, and Pl), they were produced by similar melts of siliceous high-Mg series but differ in the stratigraphy of their cumulates: while the Monchegorsk pluton is dominated by ultramafites, the Main Range Massif consists mostly of gabbroids, first of all, of gabbronorites. The complex is accompanied by PGE-Cu-Ni ore mineralization, low-sulfide Pt-Pd mineralization, and chromite mineralization. Judging from geological data and isotopic dates, the Monchegorsk Complex is a long-lived magmatic center, which evolved over a time span of 50 Myr at 2.50?C2.46 Ga. The Main Range Massif is younger and likely truncates the western continuation of the Monchegorsk pluton. The complex is spatially restricted to the zone of the Middle Paleoproterozoic regional Central Kola Fault and is now tectonic collage whose rocks were variably affected by overprinted metamorphism in the course of deformations. These processes most significantly affected rocks along the peripheries of the Monchegorsk pluton in the south. These rocks were completely transformed under greenschist-facies conditions but often preserved their primary textures and structures. The processes overprinted both the marginal portions of the pluton itself and the rocks of its second phase, which are accompanied by economic low-sulfide PGE deposits. The PGE-Cu-Ni ore mineralization of the Monchegorsk Complex is genetically related to two distinct evolutionary episodes with a quiescence period in between:

1. The emplacement of large layered mafite-ultramafite intrusions at 2.5?C2.45 Ga. Economic deposits of sulfide Cu-Ni ores with subordinate PGE mineralization occur within the Monchegorsk pluton, and the moderate-grade low-sulfide PGE ores are related to its second evolutionary phase (in the foothills of Vuruchuaivench and in the Moroshkovoe Lake, and Southern Sopcha areas). The primary magmatic ore mineralization is predominantly Cu-Fe-Ni sulfide with PGE bismuthides-tellurides.
2. The Monchegorsk Complex was involved in the zone of the Central Kola Fault at 2.0?C1.9 Ga and was broken in a collage of tectonic blocks. The rocks were sheared along the boundaries of the blocks and were affected by overprinted metamorphism, which proceeded under greenschist-facies conditions in the structures surrounding the Monchegorsk pluton in the south. Thereby the primary PGE-Cu-Ni ore mineralization underwent metamorphic processes was recrystallized with the formation of Pt-Pd arsenides, stannides, antimonides, selenides, etc. This processes was associated with the partial redistribution of PGE with their local accumulation (up to economic concentrations), and the orebodies themselves acquired diffuse outlines. In other words, the second episode was marked by the transformation of the older primary magmatic ore mineralization.

     

Geology, mineralogy, and genesis of PGE mineralization in the South Sopcha massif, Monchegorsk complex, Russia

New data are reported on the localization and genesis of PGE mineralization at the South Sopcha deposit situated in the southern framework of the Monchegorsk pluton. Disseminated PGE-Cu-Ni mineralization, the thickness of which in particular boreholes exceeds 100 m, is hosted in the zone of alternating peridotite, pyroxenite, norite, and gabbronorite. The PGE grade does not exceed 1?C2 gpt with Pd/Pt = 3?C4 at Ni and Cu contents from 0.2 to 1.5 wt %. The PGE contents up to 4?C6 gpt and Pd/Pt = 4?C8 are noted at local sites of hydrothermally altered rocks. Another type of PGE mineralization is established in the outcrops of the southeastern marginal group of the massif. Pyroxenite, norite, and gabbronorite fragments are incorporated here in the gabbroic matrix, making up a complex zone of magmatic breccia complicated by mylonites and late injections. Elevated PGE contents (1.0?C6.5 gpt) are detected in all types of rocks in the zone of brecciation, mainly in the matrix. Platinum-group minerals (PGM) occur in association with magmatic and late sulfides, amphibole, mica, and chlorite. PGM vary in composition depending on the petrographic features of rocks. In rocks of the layered series and in pegmatoid pyroxenite PGM are extremely diverse comprising PGE compounds with As, Sb, Bi, Te, Se, and S. In the brecciated rocks of the marginal group, Pd bismuthotellurides (mainly merenskyite), sperrylite, hollingworthite, and Pd- and Rh-bearing cobaltite and gersdorffite are predominant. The PGE mineralization in rocks of the layered series and pegmatoid pyroxenite was formed from the magmatic melt enriched in volatiles and with subsequent transformation of PGE assemblages under the influence of hydrothermal fluids at a lower temperature. In gabbroic rocks of the marginal group, PGM are associated with the latest sulfides (chalcopyrite, bornite, chalcocite), forming separate grains and thin veinlets in hydrothermally altered rocks. The gabbroic melt affected incompletely crystallized rocks of the layered series by formation of contact-type PGE mineralization, deposition and redeposition of ore matter.     

Deep structure and metallogeny of the Kirovograd polymetallic ore district,the Ukrainian Shield: Correlation of geological and seismic data

The study of deep structure of the Kirovograd ore district proceeds from a broad treatment of its geological boundaries and combination of metasomatic uranium, pegmatitic lithium, and hydrothermal gold deposits, as well as lodes of magmatic titanium ore within these boundaries. The spatial juxtaposition of the Novoukrainsk-Kirovograd granitoid massif and the Korsun-Novomirgorod rapakivi granite-anorthosite massif is a distinguishing feature of the Kirovograd ore district. The former massif along with stratified metamorphic rocks forms an intrusive-ultrametamorphic basement, whereas the latter massif is autonomous with respect to the basement. Taken together, both massifs make up the Novoukrainsk-Korsun-Novomirgorod composite pluton, which determines the architecture of the Kirovograd ore district not only at the present-day erosion surface but also at deeper levels of the lithosphere. The uranium, lithium, and gold deposits are localized in the intrusive-ultrametamorphic basement and controlled by various combinations of intrinsic and superposed structures; the vertical extent of mineralization is also controlled by their combinations. Some combinations are unique. Primarily, these are triple junctions of superposed faults, which host the largest metasomatic uranium orebodies. At the same time, the deposits are spatially related to the local mediumscale trough in topography of the Moho discontinuity. This mantle trench is discordant relative to the Novoukrainsk-Korsun-Novomirgorod pluton. These and other data discussed in the paper allow us to consider the Kirovograd polymetallic ore district as a Paleoproterozoic center of crustal-mantle magmatic activity and ore formation. This center was formed 2.1-1.7 Ga ago in the course of juxtaposition of three development stages differing in associations of intrusive rocks, style of deformation and metamorphism of rocks, origin and localization of ore deposits.     

赣南河草坑铀矿田成矿地质特征及找矿目标类型

河草坑铀矿田位于大富足岩体北西部接触带附近,构造、岩浆及热液活动强烈,发育多种类型的铀矿床、矿点及放射性异常点带.其中发育在花岗岩外带含碳变质岩中的岩浆热液型铀矿,以及发育在花岗岩内带的岩浆热液叠加氧化淋滤而成的复成因铀矿,是今后的找矿目标类型.     

Low-Sulfide PGE ores in paleoproterozoic Monchegorsk pluton and massifs of its southern framing,Kola Peninsula,Russia: Geological characteristic and isotopic geochronological evidence of polychronous ore–magmatic systems

New U–Pb and Sm–Nd isotopic geochronological data are reported for rocks of the Monchegorsk pluton and massifs of its southern framing, which contain low-sulfide PGE ores. U–Pb zircon ages have been determined for orthopyroxenite (2506 ± 3 Ma) and mineralized norite (2503 ± 8 Ma) from critical units of Monchepluton at the Nyud-II deposit, metaplagioclasite (2496 ± 4 Ma) from PGE-bearing reef at the Vurechuaivench deposit, and host metagabbronorite (2504.3 ± 2.2. Ma); the latter is the youngest in Monchepluton. In the southern framing of Monchepluton, the following new datings are now available: U–Pb zircon ages of mineralized metanorite from the lower marginal zone (2504 ± 1 Ma) and metagabbro from the upper zone (2478 ± 20 Ma) of the South Sopcha PGE deposit, as well as metanorite from the Lake Moroshkovoe massif (2463.1 ± 2.7 Ma). The Sm–Nd isochron (rock-forming minerals, sulfides, whole-rock samples) age of orthopyroxenite from the Nyud-II deposit (2497 ± 36 Ma) is close to results obtained using the U–Pb method. The age of harzburgite from PGE-bearing 330 horizon reef of the Sopcha massif related to Monchepluton is 2451 ± 64 Ma at initial ε_Nd =–6.0. The latter value agrees with geological data indicating that this reef was formed due to the injection of an additional portion of high-temperature ultramafic magma, which experienced significant crustal contamination. The results of Sm–Nd isotopic geochronological study of ore-bearing metaplagioclasite from PGE reef of the Vurechuaivench deposit (2410 ± 58 Ma at ε_Nd =–2.4) provide evidence for the appreciable effect of metamorphic and hydrothermal metasomatic alterations on PGE ore formation. The Sm–Nd age of mineralized norite from the Nyud-II deposit is 1940 ± 32 Ma at initial ε_Nd =–7.8. This estimate reflects the influence of the Svecofennian metamorphism on the Monchepluton ore–magmatic system, which resulted in the rearrangement of the Sm–Nd system and its incomplete closure. Thus, the new isotopic geochronological data record the polychronous development of the Monchegorsk ore–magmatic systems and the massifs in its southern framing.     

The Talazhin plagiodunite–troctolite–anorthosite–gabbro massif (East Sayan): petrogeochemistry and ore potential

The petrology and ore potential of the Talazhin massif located in northwestern East Sayan are studied. The internal structure of the intrusion, the petrographic composition of its rocks, and their metallogenic, petrostructural, and petrogeochemical features are considered. The probable temperature and chemical composition of the parental magma of the pluton were computed using the KOMAGMAT-3.52 program on the modeling of equilibrium crystallization. The obtained data indicate that the Talazhin massif is a rhythmically layered plagiodunite–troctolite– anorthosite–gabbro intrusion formed from low-Ti high-alumina olivine–basalt melt. It is promising for Cu–Ni–PGE mineralization.     

Platinum-group elements in alpine-type ultramafic rocks and related chromite ores of the main ophiolite belt of the Urals

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.     

与镁铁－超镁铁质岩石有关的矿床类型

本文综述了近年来的研究成果,介绍了与镁铁质-超镁铁质岩有关的矿床类型和成矿作用。重点讨论的矿种有钒钛磁铁矿、铜-镍、铬铁矿、磁铁矿、铂族、钴、金、镁、磷灰石、金刚石、石棉、蛭石、宝玉石等,涉及的矿床成因类型主要有:岩浆型(包括岩浆熔离、贯入、分异和爆发型)、热液型、矽卡岩型、变质型、火山喷溢型、风化型(包括风化壳和砂矿)以及复合型等。从勘查找矿考虑,可从含矿镁铁-超镁铁质岩石类型入手,结合矿床成因类型和产出构造环境因素,将矿床分为与深成岩、浅成岩和喷出岩有关的三大类和若干亚类矿床,并详细介绍了各类的主要矿床类型、成矿地质特征、成因特点和矿床实例。在此基础上,对与镁铁-超镁铁质岩有关的成矿作用进行了4个层次讨论,包括单一矿床的复合成矿作用、杂岩体本身的不同矿床类型和矿种的组合、不同镁铁-超镁铁质岩套之间的伴生,以及与非超镁铁质岩套的共生与组合。     

熊耳山—外方山矿集区中生代Au-Mo成矿系统

熊耳山—外方山矿集区位于秦岭造山带之华北板块南缘,经历了复杂的碰撞造山过程,成矿时间跨度大,成矿强度高,成矿作用多样。复合造山过程和相应的成矿作用已被深入研究,但成矿系统的划分和叠加成矿作用尚需研究。本文将熊耳山—外方山矿集区发育的Au-Mo矿床划分为造山型Mo矿床、斑岩型Mo矿床、岩浆热液脉型Mo矿床、造山型Au矿床和岩浆热液型Au矿床5个类型,对应5种成矿系统：(1)造山型Mo矿床形成于250~227 Ma的同碰撞环境和227~194 Ma的后碰撞环境,为变质热液萃取壳源Mo成矿;(2)斑岩型Mo矿床形成于163~135 Ma的洋陆俯冲环境和135~116 Ma的岩石圈减薄环境,为岩浆热液携带幔源或壳源Mo成矿;(3)岩浆热液脉型Mo矿床形成于227~194 Ma的后碰撞环境,为岩浆热液携带幔源Mo成矿;(4)造山型Au矿床在三叠纪发生了预富集作用,主要形成于163~135 Ma的洋陆俯冲环境和135~103 Ma的岩石圈减薄环境,为变质热液萃取壳源Au成矿;(5)岩浆热液型Au矿床仅形成于135~103 Ma的岩石圈减薄环境,为岩浆热液携带壳源Au成矿。矿集区主要存在两种叠加成矿作用,即不同构造背景下多种成矿系统的叠加和同一构造背景下不同成矿系统的叠加。     

Ore Mineralization in Ultramafic and Metasomatic Rocks of the Ospin–Kitoi Massif,Eastern Sayan

In the Ospin–Kitoi ultramafic massif of the Eastern Sayan, accessory and ore Cr-spinel are mainly represented by alumochromite and chromite. Copper–nickel mineralization hosted in serpentinized ultramafic rocks occurs as separate grains of pentlandite and pyrrhotite, as well as assemblages of (i) hexagonal pyrrhotite + pentlandite + chalcopyrite and (ii) monoclinal pyrrhotite + pentlandite + chalcopyrite. Copper mineralization in rodingite is presented by bornite, chalcopyrite, and covellite. Talc–breunnerite–quartz and muscovite–breunnerite–quartz listvenite contains abundant sulfide and sulfoarsenide mineralization: pyrite, gersdorffite, sphalerite, Ag–Bi and Bi-galena, millerite, and kuestelite. Noble metal mineralization is represented by Ru–Ir–Os alloy, sulfides, and sulfoarsenides of these metals, Au–Cu–Ag alloys in chromitite, laurite intergrowth, an unnamed mineral with a composition of Cu₃Pt, orcelite in carbonized serpentinite, and sperrylite and electrum in serpentinite. Sulfide mineralization formed at the late magmatic stage of the origination of intrusion and due to fluid–metamorphic and retrograde metasomatism of primary rocks.     

Low-sulfide PGE ore in the Volchetundra gabbro-anorthosite pluton, Kola Peninsula, Russia

The internal structure of the Volchetundra gabbro-anorthosite massif is considered, including localization of low-sulfide PGE mineralization and its mineralogy. The Volchetundra massif 24 km long and 0.5–4.0 km wide occupies the middle part of the Main Range complex, which extends for 75 km in the nearly meridional direction. The main and marginal zones are distinguished in the massif. The marginal zone 20–400 m wide extends along the entire eastern contact of the massif and is primarily composed of mediumgrained meso- and leucocratic norite, gabbronorite, plagioclasite, and less fequent orthopyroxenite. The main zone consists of coarse-grained leucogabbro and gabbronorite with an anorthosite zone in the axial part of the massif. The PGE mineralization of the Volchetundra massif is distinctly subdivided into two types substantially differing in localization, mineralogy, geochemistry, and economic importance. Mineralization of the first type is localized in the marginal zone and characterized by the highest resource potential. Mineralization hosted in the main zone belongs to the second type. The PGE ore of marginal zone is spatially and genetically related to the pyrite-pentlandite-chalcopyrite-pyrrhotite sulfide mineralization (1–5%) in the form of fine inequigranular interstitial disseminations, and less frequent larger grains and pockets localized within two ore zones each up to 2 km in extent. The thickness of separate mineralized layers varies from 0.5 to 3.0 m and up to 45 m in bulges. The average Pt + Pd grade is 1.37 gpt at Pd/Pt = 3.1. The mineralization of the second type has been penetrated by boreholes. Separate intersections do not correlate with one another and are limited in extent both along the strike and down the dip. The PGE mineralization is related to finely dispersed pentlandite-pyrite-pyrrhotite-chalcopyrite sulfides, sulfide emulsions, and less abundant stringer-disseminated sulfide ore. The orebodies vary from 2 to 7 m in thickness. The average Pt + Pd grade is 1.61 gpt; Pd/Pt = 1.3. The PGE mineralization includes 22 mineral species. PGE sulfides (cooperite-braggite-vysotskite; laurite and erlichmanite in insignificant amounts) are predominant. Bismuthotellurides (moncheite-kotulskite-merenskyite) and arsenides (sperrylite, palladoarsenite, arsenopalladinite, atheneite) are subordinate in abundance. In addition, sulfoarsenides (platarsite, hollingworthite), tellurides (telargpalite, sopcheite, keithconnite, melonite, hessite), paolovite, and Pt-Fe alloy have been identified. An admixture of native gold and electrum occur constantly.     

PROSPECTING FOR COPPER (GOLD )-POLYMETAL ORES FROM THE LANCANGJIANG TECTONIC ZONE IN WESTERN YUNNAN

The Lancangjiang tectonic zone in Western Yunnan is an important magmatic,metamorphic and tectonic mobile zone of Southwestern China,whose geotectonic location is very unique.It is characterized by complex geological structures,perfectly developed strata,frequent magmatic activities,,various degrees of metamorphism,rich ore resources and lots of metal deposits,thus formed a centralized zone of mineralization and also constituted one of the important metallogenic belts of noble and nonferrous metal deposits.     

南秦岭泥盆系典型金矿床高盐度流体脑其深源特征

对赋存于南秦岭泥盆系浅变质碎屑岩中的陕西太白金矿到八卦庙金矿主成矿阶段的石英和含铁白云石中的流体包裹体进行研究,发现局部富含高盐度、含子矿物的流体包裹体,通过光学显微镜,电子探针（ＥＰＭＡ）,扫描电镜／能谱（ＳＥＭ／ＥＤＳ）发现子矿物主要为黄铁矿,铁白云石、石盐、毒砂及一些成分复杂的子矿物,认为矿床成矿流体具复杂的物理化学条件,不同于一般的热液金矿床,结合矿床形成的大地构造位置分析,主成矿阶段矿物     

Ulan-Tologoi Ta–Nb Deposit: the Role of Magmatism in the Formation of Rare Metal Mineralization

The role of magmatic differentiation is considered for the formation of the Ulan-Tologoi Ta–Nb–Zr deposit (northwestern Mongolia) related to the eponymous alkali granite pluton. Data are presented on the structure of the pluton, the composition of its rocks, and distribution of rare metal mineralization. The ores of the pluton include alkali granites with contents of ore elements exceeding the normative threshold for Ta (>100 ppm). The rare metal mineralization includes pyrochlore, columbite, zircon, bastnaesite, monazite, and thorite, which are typical of all alkali–salic rocks; however, their amount varies depending on the REE content of the rocks. The pluton was formed ~298 Ma ago under the influence of a mantle-crustal melt source.

     

河南桐柏围山城金银成矿系统矿床地球化学特征

河南桐柏围山城的金银矿床形成于印支—燕山期碰撞造山的动力学背景。对矿床地球化学的研究表明 ,各矿床围岩均发生大规模的成矿元素活化迁移 ,稀土元素和硫同位素资料均指示矿化主要源自早期的矿源层 ;Pb同位素资料指示俯冲下插的南秦岭构造岩片部分融熔形成的花岗岩浆和深源流体提供了部分成矿物质 ;H、O同位素资料指示成矿流体主要由大气降水、部分岩浆热液和变质热液混合演化而成。工业矿体的形成与后期的构造及热流体的叠加改造有关。矿化带内金银矿床具有共同的成矿地质背景和成矿地质特征 ,构成了一个完整的以沉积初始富集、构造及岩浆热液改造的成矿系统     

蒙古国巴彦洪戈尔地区金矿床地质特征及成因

巴彦洪戈尔地区位于蒙古中央地块南侧, 构造活动复杂, 发育有多期构造岩浆活动。区内发育有与花岗岩类有关金、铜等矿床。金矿床类型有石英脉型和斑岩型、矽卡岩型, 主要金和铜矿化与二叠纪磁铁矿系列花岗岩类密切相关, 与钛铁矿系列花岗岩类有关的矿化较少。成矿年代学研究显示, 金矿床的形成应早于三叠纪, 主要发生于石炭纪和二叠纪, 形成于微大陆碰撞期构造转换过程中的岩浆活动期间, 区内金矿床(点)构成蒙古国最具潜力的金成矿带。     

论地穹区“三位一体”金的构造成矿及其有序性

本文以笔者所提出的构造矿源层(前寒武系变质岩区)+燕山期岩体(岩浆岩或火山岩)+断裂交汇部位(构造扩容空间)的金银-多金属构造成矿的模式(或谓“三位一体”构造成矿模式),对中国主要金矿的构造成矿、成矿控矿系列(构造成矿区、构造成矿带、构造成矿田、矿床和矿体的成矿定位)作了进一步的论述。指出了具有前寒武系变质岩的地穹区及其边缘断裂带为金的构造成矿富集区,并指出了金矿构造成矿的有序性规律及找矿远景区。     

小秦岭太华杂岩副片麻岩碎屑锆石U-Pb年龄、Hf同位素及其地质意义

小秦岭地区是华北克拉通南缘早前寒武纪基底重要分布区,可见大量构造抬升剥露的基底结晶杂岩带。太华杂岩是小秦岭出露最古老的地质体,对于探讨华北克拉通南缘早期地壳形成和演化及其构造归属等问题具有重要意义。在小秦岭地区,太华杂岩被划分为正片麻岩系和以孔兹岩系为主的表壳岩。利用LA-ICP-MS锆石U-Pb定年方法测得小秦岭地区太华杂岩表壳岩中黑云斜长片麻岩碎屑锆石的源区物质主要形成于2.40～2.11 Ga,经历了两期的古元古代晚期变质事件（～2.04 Ga和～1.91 Ga）,限定该套表壳岩的沉积时代介于2.11～1.91 Ga。结合锆石Hf同位素特征,我们认为该表壳岩的碎屑物质可能主要来自中条山的涑水杂岩体及绛县杂岩体、熊耳花岗岩体、小秦岭古元古代花岗岩体等,其初始的源区物质可能为太华杂岩的新太古代正片麻岩系。此外,本研究揭示华北中部造山带可能记录了一个长达约250 Ma（～2.05～1.8 Ga）持续的俯冲-碰撞过程。     

The Ishkinino Co-Cu massive sulfide deposit hosted in ultramafic rocks of the Main Ural Fault Zone, the southern Urals

The results of study of the Ishkinino Co-Cu massive sulfide deposit hosted in ultramafic rocks of the Main Ural Fault Zone are discussed. The ore field is localized in a fragment of Early Devonian accretionary prism composed of oceanic and island-arc tectonic sheets. The antiform structure of the ore field was formed at the collision stage in the Late Devonian. The primary ore was deposited near the bottom in the environment of the accretionary prism at the island-arc stage of evolution, whereas the superimposed ore mineralization was related to the collision stage. The primary ore is composed of massive, stringer-disseminated, and clastic varieties with two mineral assemblages of sulfides and oxides. The superimposed stringer-disseminated ore mineralization is represented by Co-Ni-Fe arsenides and sulfoarsenides, native gold, Bi and Te minerals, and late sulfides and oxides. Loellingite, safflorite, rammelsbergite, and krutovite were identified in the massive sulfide ore for the first time in the Urals. The geochemical attributes of Co-Ni minerals serve as indicators of superimposed processes. Chromites contained in rocks and ore correspond to Cr-spinel of suprasubduction ultramafic rocks in chemical composition. It is suggested that sulfide ore may be found in the accretionary prisms of the presently active island arcs composed of ultramafic sheets.     

中酸性岩浆体系成矿流体及微量元素地球化学特征

从流体成矿作用角度出发，与酸性岩浆体系有关的成矿流体可以分为：酸性岩浆硅酸盐熔融体，岩浆一热液过渡阶段硅酸盐熔融体及其分异的流体，酸性岩浆熔体分异形成的热水成矿溶液。酸性岩浆体系主要提供热源和部分矿质，其提供的热源驱动地下水淋滤、萃取围岩中的成矿物质形成地下水热液成矿流体。变质岩混合岩化形成花岗质岩浆过程中所形成的混合岩化成矿流体。在此基础上，讨论了上述不同成矿流体的微量元素地球化学特征及其对成矿的控制作用。