浙江安吉多金属矿床金银赋存状态及银矿物特征研究

安吉矿区是以热液型铅锌铜为主的多金属矿床,工程样化验结果显示,各类矿石均含有高品位的银,可以独立划分银矿体。岩矿显微鉴定、SEM/EDS及EPMA分析结果表明,矿区中的Pb、Zn和Cu主要以方铅矿、闪锌矿、黄铜矿形式存在,银与这些硫化物有密切的依存关系。对数十个典型矿石光薄片进行了研究,发现矿区多数铅锌铜矿石中金、银主要以类质同像形式存在于方铅矿、闪锌矿、黄铜矿、黄铁矿等硫化物中,金、银含量分别达0.03%~0.57%和0.02%~3%。而热液脉型铅锌矿石中的银主要以两种独立银矿物(硫锑铜银矿和银锑黝铜矿)的形式,在方铅矿之中呈粒状、短柱状、叶片状、树枝状、不规则状发育,单颗粒粒度多在10~60μm之间,少数可达100μm,集合体粒度可达200μm。另外这两种独立银矿物之中还存在类质同像形式的金,据统计,金、银含量分别达0.14%~0.35%和10.98%~69.12%。因此,方铅矿为银独立矿物的主要载体之一,且富方铅矿的矿石中更容易发现独立银矿物。     

甘肃寨上金矿床矿物组成特征与矿质沉淀机理

位于西秦岭礼(县)—岷(县)成矿带西段的寨上金矿床,是近年发现的一个大型微细浸染型金矿。笔者通过显微镜观察、电子探针和扫描分析等综合分析技术,确认金矿床中矿物组成相当丰富,既有大量硫化物、硫盐、氧化物、硫酸盐、碳酸盐、钨酸盐,又有碲化物、自然金属及多金属互化物。除常见矿物为自然金、黄铁矿、黄铜矿、黝铜矿、方铅矿、闪锌矿、辉锑矿、石英、白钨矿、方解石、菱铁矿、铁白云石和重晶石外,笔者还鉴定出在卡林型金矿床较少见的一些矿物,如硫铜锑矿、车轮矿、辉锑铅矿、辉钼矿、碲汞矿、碲镍矿、Cu-Zn-Ni-Sn-Fe的金属互化物和白钨矿等。矿石中矿物种类较多,组成较复杂以及存在显微自然金,构成寨上金矿床的一大特色。赋矿围岩中含Fe碳酸盐矿物溶解释放Fe以及溶解Fe的大量硫化物化,是寨上金矿床中存在显微可见自然金的最重要因素和金沉淀富集的有利条件。     

The Sin Quyen Cu–Fe–Au–REE deposit (northern Vietnam): composition and formation conditions

The Sin Quyen Cu–Fe–Au–REE deposit is localized in the Proterozoic deposits of the Phan Xi Pang zone, northern Vietnam. The mineralization is formed by lenticular and sheet-like bodies occurring concordantly with the host rocks. Seventeen orebodies have been recognized in the deposit, which form an ore horizon up to 140 m in total thickness, about 2 km in strike, and up to 350 m in dip. The ores are of simple mineral composition: Au-rich copper and iron sulfides (chalcopyrite, pyrite, pyrrhotite) and iron oxides (magnetite, hematite). Gold and silver are distributed unevenly in the ores: Their contents vary from hundredths and tenths of ppm to 1.8 ppm. Copper sulfide ores are the main concentrator of gold and silver. All ores are characterized by high REE contents, tens and hundreds of times exceeding the element clarkes. The highest contents have been revealed for Ce and La. Orthite is the main carrier of REE. No correlation between REE and ore elements of sulfide-oxide ores has been revealed, which points to the independent formation of the mineralization. Orebodies together with the host rocks underwent metamorphism at 500–600 to 630–685 °C and 3–7 kbar. The spatial association of the mineralization with amphibolites (metamorphosed basites) and the mineral composition of ores suggest that the Sin Quyen deposit is of Cyprian volcanogenic type.     

金川铜镍硫化物矿床中铂族矿物的主要类型和产出特征:热液蚀变过程中铂族元素的富集机理

金川铜镍硫化物矿床是我国最主要的铂族元素(PGE)资源产地,其矿石受热液蚀变作用影响明显,并产出多种铂族矿物(PGM)。岩浆演化和热液蚀变过程中PGE的迁移富集机制和PGM的成因,一直是研究PGE地球化学行为非常关注的问题。本文对金川铜镍硫化物矿床中PGM的研究发现,其主要类型包括含PGE的硫砷化物(硫砷铱矿)和砷化物(砷铂矿),Pd的铋化物、碲化物和硒化物,以及少量其他铂族矿物。其中,硫砷铱矿可包裹于各种贱金属硫化物(镍黄铁矿、磁黄铁矿和黄铜矿)中,表明硫砷铱矿可能结晶于早期的含As硫化物熔体,随后被包裹于硫化物熔体冷凝分异产生的单硫化物固溶体(MSS)和中间硫化物固溶体(ISS)中。硫化物熔体中的As可能主要通过地壳混染作用加入幔源岩浆。大量铋钯矿(PdBi)呈微细乳滴状包裹于黄铜矿中,为晚期ISS冷凝形成黄铜矿过程中出溶的产物。少量铋钯矿(PdBi_2)呈不规则状充填于矿物裂隙,与次生磁铁矿脉紧密共生,并随矿石的蚀变程度增加,铋钯矿的化学成分由PdBi逐渐向PdBi_2转变,表明这部分铋钯矿为后期热液蚀变产物。铋碲钯矿和钯的硒化物则主要产出于镍黄铁矿裂隙且与次生磁铁矿紧密共生,指示明显的热液成因。钯的硒化物的出现表明,岩浆期后酸性、高盐度、高氧逸度的富Cl~-流体对金川铜镍硫化物矿床中Pd的迁移和富集起到了关键控制作用。     

Geochemistry and mineralogy of platinum group element in ores of the Kingash deposit,Eastern Sayan,Russia

The paper discusses the results of studying the contents of platinum group elements (PGE) and platinum group minerals (PGM) in ores of the Kingash deposit. The bulk of PGE has been established as concentrated in disseminated sulfide chalcopyrite–pyrrhotite–pentlandite ore and is represented by palladium bismuth–tellurides. During melt differentiation, the content and relationship of PGE are changed; the Pd/Pt value increases (up to 1.9 and 4.2 in dunite and wehrlite, respectively) with decreasing Mg number. The distribution of PGE, sulfur, and REE in various ore types suggests two formation mechanisms of high-grade ores: (1) the product of liquid immiscibility and gravity separation at the early magmatic stage and (2) involvement of the residual melt saturated in volatiles, which contributed to transportation and segregation of PGE at the late magmatic stage. The evolution of the ore system of the Kingash massif is characterized by sequential enrichment of PGM in Ni from high-Mg to low-Mg rocks similarly to sulfide minerals of disseminated ore. The criteria for ore content in utramafics of the Kansk block have been identified based on compared ore element and PGE concentrations in ultramafic rocks of the Kingash and Idar complexes.     

Chemical composition of the ore and occurrence state of the elements in Jingbaoshan platinum-palladium deposit

The Jingbaoshan platinum-palladium deposit is China＇s largest independent PGM （platinum-group metals） deposit so far discovered. There are eleven kinds of useful components in the ore： Pt, Pd, Os, Ir, Ru, Rh, Au, Ag, Cu, Ni, and Co. The platinum-group elements, gold and silver occur in the form of minerals in ores. twenty-five kinds of precious metal minerals have been found, of which twenty one belong to the platinum-group minerals. The minerals are very small in grain size. Copper occurs mainly as copper sulfide with a small amount of free copper oxide, and the beneficiated copper accounts for 95.21%. Nickel occurs mainly as nickel sulfide, and some nickel silicate and nickel oxide occur in the ore. The beneficiated nickel accounts for 72.03%. Cobalt occurs mainly as cobalt sulfide, and there are some cobalt oxide and other kinds of cobalt. The beneficiated cobalt accounts for 77.58%.     

甘肃礼县-岷县成矿带西段寨上金矿床中自然金的发现及成因意义

位于西秦岭礼(县)-岷(县)成矿带西段的寨上金矿床是近年发现的一个大型微细浸染型金矿。在研究甘肃寨上金矿床物质组分的过程中,采用显微镜观察、电子探针扫描、化学分析等综合分析技术发现了显微自然金颗粒。矿石中的自然金颗粒形态多样,粒度变化较大(5～150μm)。电子探针分析结果显示,自然金中Au=88.23%～92.73%,Ag=7.41%～9.08%,为含银自然金,成色905～926。金的载体矿物有砷黄铁矿、方铅矿、碲汞矿、铁白云石等。金的嵌布类型有粒间金、裂隙金和连生金3种。赋矿围岩中含Fe碳酸盐矿物溶解释放出Fe和溶解Fe的大量硫化物化,可能是寨上金矿床中存在显微可见自然金的最重要因素。     

Mineralogy of the Boroo Gold Deposit in the North Khentei Gold Belt,Central Northern Mongolia

Mineral assemblages and chemical compositions of ore minerals from the Boroo gold deposit in the North Khentei gold belt of Mongolia were studied to characterize the gold mineralization, and to clarify crystallization processes of the ore minerals. The gold deposit consists of low‐grade disseminated and stockwork ores in granite, metasedimentary rocks and diorite dikes. Moderate to high‐grade auriferous quartz vein ores are present in the above lithological units. The ore grades of the former range from about 1 to 3 g/t, and those of the latter from 5 to 10 g/t, or more than 10 g/t Au. The main sulfide minerals in the ores are pyrite and arsenopyrite, both of which are divisible into two different stages (pyrite‐I and pyrite‐II; arsenopyrite‐I and arsenopyrite‐II). Sphalerite, galena, chalcopyrite, and tetrahedrite are minor associated minerals, with trace amounts of bournonite, boulangerite, geerite, alloclasite, native gold, and electrum. The ore minerals in the both types of ores are variable in distribution, abundance and grain size. Four modes of gold occurrence are recognized: (i) “invisible” gold in pyrite and arsenopyrite in the disseminated and stockwork ores, and in auriferous quartz vein ores; (ii) microscopic native gold, 3 to 100 µm in diameter, that occurs as fine grains or as an interstitial phase in sulfides in the disseminated and stockwork ores, and in auriferous quartz vein ores; (iii) visible native gold, up to 1 cm in diameter, in the auriferous quartz vein ores; and (iv) electrum in the auriferous quartz vein ores. The gold mineralization of the disseminated and stockwork ores consists of four stages characterized by the mineral assemblages of: (i) pyrite‐I + arsenopyrite‐I; (ii) pyrite‐II + arsenopyrite‐II; (iii) sphalerite + galena + chalcopyrite + tetrahedrite + bournonite + boulangerite + alloclasite + native gold; and (iv) native gold. In the auriferous quartz vein ores, five mineralization stages are defined by the following mineral assemblages: (i) pyrite‐I; (ii) pyrite‐II + arsenopyrite; (iii) sphalerite + galena + chalcopyrite; (iv) Ag‐rich tetrahedrite‐tennantite + bournonite + geerite + native gold; and (v) electrum. The As–Au relations in pyrite‐II and arsenopyrite suggest that gold detected as invisible gold is mostly attributed to Au⁺¹ in those minerals. By applying the arsenopyrite geothermometer to arsenopyrite‐II in the disseminated and stockwork ores, crystallization temperature and logfs₂ are estimated to be 365 to 300 °C and –7.5 to –10.1, respectively.     

Thermodynamic Modelling of Ore-Forming Mechanism of the Changkeng Gold-Silver Deposits in Guangdong Province

The Changkeng gold-silver deposits consist of a sediment-hosted, disseminated gold deposit and a replacement-type silver deposit. The mineralizations of gold and silver are zoned and closely related to the silicification of carbonate and clastic rocks, so that siliceous ores dominate in the deposit. The mineralizing temperature ranges mainly from 300 to 170℃, and K+, Na+, Ca2+, Mg2+, and Cl- are the major ions in the ore-forming fluid. Calculations of distribution of metal complexes show that gold is mainly transported by hydrosulphide complexes, but chloride complexes of silver, iron, lead, and zinc, which are transformed into hydroxyl and hydrosulphide complexes under neutral to weak-alkaline circumstances in the late stage, predominate in the ore-forming solutions. Water-rock interaction is confirmed to be the effective mechanism for the formation of silver ores by computer modelling of reaction of hydrothermal solution with carbonate rocks. The solubility analyses demonstrate that the precipitation     

Loypishnyun Low-Sulfide Pt–Pd Deposit of the Monchetundra Basic Massif,Kola Peninsula,Russia

The geology of the basal-structural Loypishnyun low-sulfide Pt–Pd deposit is characterized, including its mineral composition and the peculiarities of its PGE and chalcophile-element distribution in ore. The deposit is situated in the northeastern part of the Monchetundra basic massif and is localized in its lower norite–orthopyroxenite zone, intensely injected with late gabbroic rocks. Two ore zones are distinguished within the deposit. Ore zone 1 has been traced by drilling for about 1.5 km at a thickness from 10–15 to 120 m and incorporates from two to nine separate lenticular–sheetlike orebodies 0.5–25 m in thickness. Ore zone 2 has been traced for 550 m and is represented by one orebody 5–35 m thick. The internal structure of the orebodies is characterized by alternation of low-grade (Pt + Pd = 0.5–0.9 gpt), ordinary (Pt + Pd = 1.0–1.9 gpt), and high-grade (Pt + Pd > 2 gpt) interlayers of various thickness. The ores are spatially and genetically related to sulfide mineralization (pentlandite–chalcopyrite–pyrrhotite) in an amount of 1–5 vol %. The PGE distribution in ores normalized to primitive mantle is characterized by fractionation of easily fusible platinoids with a positive Pd anomaly. The spectra of chalcophile elements normalized to primitive mantle are notable for elevated Te, Bi, As, and Se contents with respect to Sn, Hg, and Pb, which reflects the significant contribution of Te, Bi, and As in the formation of platinum group minerals (PGM), whereas Se, which is devoid of proper mineral phases, most likely is an admixture in the composition of sulfides. The S/Se value in ore of the Loypishnyun deposit varies from 31 to 814. The platinum group elements (PGE) in ore are represented by 45 noble metal minerals. Ore zone 1 is characterized by lateral mineral zoning, which is expressed as replacement of a bismuthotelluride–sulfide PGM assemblage by an assemblage of copper–PGE compounds and alloys. In ore zone 2, a mineral assemblage of tellurides, copper–PGE compounds and alloys predominates, with native gold, silver, and palladium, as well as sulfides and bismuthotellurides, playing a subordinate role. The formation of PGM ore proceeded under variable sulfur fugacity conditions, beginning with the late magmatic stage at temperatures of 900–700°C and ending with hydrothermal transformation at a temperature of <500°C.     

新疆克兰盆地红墩铅锌矿床与铁木尔特铅锌矿床的对比研究

虽然红墩铅锌矿床与铁木尔特铅锌矿床均产于新疆阿尔泰山南缘中部的克兰裂谷盆地,且二者的矿体产状与地层走向一致,具有明显的纹层状构造,但是在某些主要地质特征上,二者却存在显著的差异.例如,前者赋存于中泥盆统阿勒泰镇组的沉积碎屑岩,与海相基性火山岩有关,表现为锌多铅少,不含铜,且闪锌矿为含铁较少的低温闪锌矿;而后者却赋存于下泥盆统康布铁堡组的火山碎屑-碳酸盐岩中,与海相酸性火山岩有关,表现为铅多锌少,富含铜,且闪锌矿为含铁较多的高温闪锌矿.综合对比研究表明,红墩铅锌矿床属于SEDEX型铅锌矿床,而铁木尔特铅锌矿床则属于VHMS型铅锌矿床.     

新疆托里萨Ⅰ金矿床的地质特征及成因研究

新疆托里萨I金矿床产于托里蛇纹岩套的超镁铁岩相内,与超镁铁岩的蚀变交代作用有关.矿床地球化学研究表明该矿床的形成与海底热泉活动有关,是一种新的金矿床类型.     

吉尔吉斯斯坦Taldybulak Levoberezhny(左岸)金矿地质特征及金属矿物学研究

Taldybulak Levoberezhny(又称左岸)矿床位于吉尔吉斯斯坦北天山东段,是区内第三大金矿(金储量130 t,平均品位6.9 g/t)。长期以来,该矿床矿物学研究薄弱,成因类型存在争议,已有观点包括斑岩型、造山型、多阶段叠加成矿等。野外地质调查及室内岩相学鉴定发现：金矿化同时受韧性剪切带和岩体控制,局部显示一定的顺层特征;常见矿石类型包括浸染细脉浸染型、石英电气石硫化物型、块状硫化物型、稀疏浸染型、方解石硫化物脉型等;相关围岩蚀变以硅化、绢云母化、电气石化、碳酸盐化最为强烈,可见绿泥石化、绿帘石化、泥化等。电子探针分析发现,左岸金矿同时发育可见金和不可见金。前者包括银金矿(w(Au)=67.90%~80.86%,w(Ag)=14.24%~30.76%)、含银自然金(w(Au)=88.95%,w(Ag)=8.09%)等,以包体金、裂隙金或粒间金形式赋存于黄铁矿中。后者可赋存于黄铁矿和黄铜矿中(w(Au)=0.16%~0.33%)。不同类型矿石中黄铁矿的形态、结构、成分存在一定差异,显示了叠加成矿的可能性。浸染状细脉浸染型矿石中黄铁矿以中粗粒(30~1 300 μm,多数>200 μm)、半自形自形立方体为主,基本无碎裂或碎裂不明显,可含有自然金、银金矿或硅酸盐包体;成分上具有中等的As(0.03%~1.72%,平均0.66%)、Co(0.06%~0.19%,平均0.13%)、Te(0.03%~0.06%,平均0.04%)含量和As/S、Fe/S、Co/As比值,基本不含Cu、Pb、Zn、Ag。石英电气石硫化物型矿石中黄铁矿多呈中粗粒(30~2 000 μm)、半自形它形粒状,往往发生碎裂,并被黄铜矿、方铅矿等矿物交代;部分颗粒可含有银金矿或硅酸盐包体;总体具有较高的As(0.05%~2.05%,平均0.97%)、Co(0.05%~0.34%,平均0.15%)含量和As/S、Fe/S比值,Co/As比值较低。块状硫化物型矿石中黄铁矿多呈半自形它形粒状产出,但粒度变化较大(250~3 000 μm或者30~300 μm);化学成分上以较高的As(0.05%~2.20%,平均1.21%)、Te(0.04%~0.09%,平均0.06%)含量,高的As/S、Fe/S比值和低的Co/As比值为特征。稀疏浸染型矿石中黄铁矿呈中粒(集中于50~200 μm)、半自形它形粒状产出,内部可含有硫化物、硅酸盐、银金矿、自然金等包体;可发生碎裂并被黄铜矿等沿裂隙充填交代;化学成分变化较大,总体具有较高的Co(0.08%~1.04%,平均0.35%)含量和Co/As比值,几乎不含Te、Cu、Zn。方解石硫化物脉型矿石中黄铁矿呈中粗粒(40~480 μm)、半自形它形粒状产出,内部往往含硅酸盐等包体;黄铁矿以显著低的As(0.04%~0.08%,平均0.06%)、Co含量(0.04%~0.20%,平均0.10%)以及As/S、Fe/S比值为特征,Co/As比值较高,且不含Zn。从上述左岸金矿的控矿构造、矿化类型、围岩蚀变以及不同类型矿石中黄铁矿形态、结构、成分的差异等4方面特征显示,左岸金矿可能存在多期次矿化、叠加成矿。     

Carbonatitic Volcanic Genesis of Hetaoqing Fe-Cu Deposit in Central Yunnan, China

Abstract. The Kunyang rift on western margin of Yangtze Platform is a continental rift, and also a rare Precambrian Fe-Cu mineralization zone in China. The Wuding-Lufeng mineralization area in the middle section of the rift is an important part of the zone, and an elliptic-shaped volcanic collapsed basin, controlled by a ring fracture system with carbonatitic volcanic rocks mainly occurring along the northwestern edge of the basin. The Hetaoqing Fe-Cu ore deposit at the western side of the basin is hosted in carbonatitic volcanic rocks and pyroclastic sedimentary rocks. The original ore bodies occur as layers, bands and lenses conformable to the host carbonatitic rocks. The ores usually appear as massive, impregnated and granular in carbonatitic rocks, and as brecciform and sandy in pyroclastic sedimentary rocks. Ore-forming minerals are magnetite, hematite, chalcopy-rite, bornite, pyrite, carrollite, molybdenite, cobaltite and skinnerite, and secondary minerals limonite, chalcocite, azurite, malachite and tenorite. Gangue minerals are calcite, dolomite, ankerite, common hornblende, arfvedsonite, augite, aegirine-augite, albite, phlogopite, biotite, chlorite and apatite. Evidences of mineral chemistry, trace elements and isotopic ratios of ores, as well as geological features, suggest that the original ores are igneous in origin. Chemical features of magnetites in the deposit belong to carbonatite type, and are similar to those from the Bayan Obo carbonatites. The ores are rich in iron, titanium, rare earth elements, niobium, tantalum, gold, silver, phosphor and sulfur. These features indicate that the Fe-Cu deposit associated with volcanic activity in the Wuding-Lufeng basin is alkali-carbonatite volcanic type.     

安徽朝山金矿床矿石含金性和硫同位素研究

朝山金矿床位于铜陵市东郊狮子山矿田内。除了自然金之外,矿床中金主要以晶格金方式赋存于磁黄铁矿、黄铁矿和毒砂等矿石矿物之中;各种类型矿石成矿元素研究表明,含金磁黄铁矿石中金含量最高,其他依次为含金磁黄铁矿—黄铁矿矿石、含金黄铁矿化大理岩、含金矽卡岩、含金黄铁矿矿石等;硫同位素分析显示矿石硫主要来自深源或幔源硫,但在上升过程中遭受到地壳物质混染。在上述研究基础上,综合前人研究成果及朝山金矿地质特征,表明朝山金矿床属于热液交代型金矿床,形成时代为燕山中晚期。     

Mineral and geochemical compositions,regularities of distribution,and specific formation of ore mineralization of the Rogovik gold-silver deposit (northeastern Russia)

New data on the mineral composition and the first data on the geochemical composition of ores of the Rogovik gold-silver deposit (Omsukchan ore district, northeastern Russia) have been obtained. Study of the regularities of the spatial distribution of ore mineralization shows that the deposit ores formed in two stages. Epithermal Au-Ag ores of typical poor mineral and elemental compositions were generated at the early volcanic stage. The major minerals are low-fineness native gold, electrum, acanthite, silver sulfosalts, kustelite, and pyrite. The typomorphic elemental composition of ores is as follows: Au, Ag, Sb, As, Se, and Hg. The content of S is low, mostly < 1%. Silver ores of more complex mineral and elemental compositions were produced under the impact of granitoid intrusion at the late volcanoplutonic stage. The major minerals are high-Hg kustelite and native silver, silver sulfosalts and selenides, fahlore, pyrite, chalcopyrite, galena, and sphalerite. The typomorphic elemental composition of ores is as follows: Ag, As, Sb, Se, Hg, Pb, Zn, Cu, and B. The content of S is much higher than 1%. The ores also have elevated contents of Mo, Ge, F, and LREE (La, Ce, and Nd). At the volcanoplutonic stage, polychronous Au-Ag ores formed at the sites of the coexistence of silver and epithermal gold-silver mineralization. Their specific feature is a multicomponent composition and a strong variability in chemical composition (both qualitative and quantitative). Along with the above minerals, the ores contain high-Hg gold, hessite, argyrodite, canfieldite, orthite, fluorapatite, and arsenopyrite. At the sites with strongly rejuvenated rocks, the ores are strongly enriched in Au, Ag, Hg, Cu, Pb, Zn, Ge, Se, La, Ce, Nd, S, and F and also contain Te and Bi. The hypothesis is put forward that the late silver ores belong to the Ag-complex-metal association widespread in the Omsukchan ore district. A close relationship between the ores of different types and their zonal spatial distribution have been established. In the central part of the Rogovik deposit, epithermal Au-Ag ores are widespread in the upper horizons, Ag ores are localized in the middle horizons, and rejuvenated polyassociation Au-Ag ores occur at the sites (mostly deep-seated) with ore-bearing structures of different ages.     

Compositional variations and morphological evolution in platinum beach placers, southern New Zealand

Morphologies of placer platinum group minerals (PGM) are more variable and resistant to modification during transport than placer gold grains. This study documents morphological evolution of PGM placer grains during up to 120 km of transport in beach placers after river transport from inferred sources up to 200 km inland. PGM morphological changes are calibrated with changes in morphology of associated placer gold. Most of the PGM are Pt-Fe alloy and have been fed into the beach placer system from a large river at the western end of the beaches on the south coast of New Zealand. The incoming fluvial PGM suite includes Os, Ir and Ru alloys which may have been derived from distal ophiolitic sources. More proximal sources have Ural-Alaskan affinities and these contributed cooperite and braggite, or sperrylite, locally, as well as Pt-Fe alloy grains. Some PGM may have been recycled through Cretaceous-Quaternary fluvial sediments before entering the modern placer system. Recycled placer PGM grains have also been derived from elevated Quaternary beaches near the coastline. PGM grains entering beach placers have rough surfaces, with remnants of crystal faces, and these evolve to smooth flakes with progressive long-shore transport. PGM flakes have slightly thickened rims caused by impacts by saltating sand on windy beaches, and the most distal beach placers contain flakes with incipient toroidal shapes. These PGM incipient toroids are poorly developed compared to accompanying well-formed toroidal gold that has developed in nearly all beach placers, including those on elevated Quaternary beaches. Typical PGM and gold placer grain size decreases with increasing distance of transport, from fluvial grain size of 400–1,000 to ～200 microns on the most distal beaches, accompanied by eastward loss of equant PGM grains and associated increase in proportion of flakes. Although net transport distance is ～120 km in the beach placer complex, frequent aeolian transport of grains from beach to dunes and subsequent recycling by storm surges substantially increased total transport distance in a dynamic windy tectonic environment.     

Noble-metal minerals in ores of the black-shale type in the Voronezh Crystalline Massif, central Russia

High-carbonaceous stratified formations and related metasomatic rocks of global abundance are among highly promising sources of gold and platinum-group metals (PGMs) in the 21st century. The Au-PGM mineralization of the black-shale type hosted in the Early Karelian Kursk and Oskol groups in central Russia is characterized by complex multicomponent and polymineralic composition (more than 60 ore minerals, including more than 20 Au and PGM phases) and diverse speciation of noble metals in form of (1) native elements (gold, palladium, platinum, osmium, silver); (2) metallic solid solutions and intermetallic compounds (Pt-bearing palladium, Fe-bearing platinum, gold-platinum-palladium, osmiridium, rutheniridosmin, platiridosmin, platosmiridium, Hg-Te-Ag-bearing gold, gold-silver amalgam, arquerite, palladium stannide (unnamed mineral), platinum-palladium-gold-silver-tin); (3) PGM, Au, and Ag sulfoarsenides, tellurides, antimonides, selenides, and sulfosalts (sperrylite, irarsite, hessite, Pd and Pt selenide (unnamed mineral)), testibiopalladinite, Pd antimonide (unnamed mineral), etc.; and (4) impurities in ore-forming sulfides, sulfoarsenides, tellurides, antimonides, and selenides. The chemical analyses of PGM and Au minerals are presented, and their morphology and microstructure are considered.     

北祁连块状硫化物矿床中矿石和主要矿石矿物地球化学特征

对北祁连山白银矿田和郭密寺矿田中主要矿床的矿石和矿石矿物组分特征研究表明，由于各矿田的成矿条件和地球化学背景存在差异，造成不同矿床的矿石和矿石矿物元素组合各具特色。但作为同一类型矿床，它们之间又有很多共性，特别是同一矿田内各矿床的地球化学特征具有相似性和过渡性，反映了成矿条件变化的趋势。     

辽东林家三道沟-小佟家堡子地区金（银）矿成矿特征及成因

以林家三道沟、小佟家堡子金（银）矿床为例,系统总结了区内金（银）矿床的成矿条件及地质特征,对矿床的相关岩体、围岩及矿石进行了流体包裹体、稳定同位素测试分析。结果表明：矿床赋存于古元古界辽河群大石桥亚群杨树沟岩组第6岩段碎屑岩-碳酸盐岩建造和盖县亚群汤家沟岩组碎屑岩建造中;主要容矿岩石为硅化大理岩、变粒岩、片岩;近矿围岩蚀变主要为硅化、绢云母化、黄铁矿化和碳酸盐化;自然金的粒度以显微不可见金为主;均一温度（100～200 ℃）、成矿流体盐度（w（NaCl）（1.91 % ～9.73%）均较低;矿石石英中成矿流体δD值为-48.0‰～-93.0‰,δ¹⁸O_H2O计算值为-8.63‰～+1.31‰,表明成矿流体主要来自于地热水和原生地层水;矿石硫同位素δ³⁴S值平均为+8.61‰,赋矿围岩、岩体δ³⁴S为＋0.50‰～＋7.6‰,表明矿石中硫主要来自古元古代地层和印支晚期岩体;金（银）矿石中²⁰⁶Pb/²⁰⁴Pb为17.664～19.186 7,²⁰⁷Pb/²⁰⁴Pb为15.044～15.883,²⁰⁸Pb/²⁰⁴Pb为37.693～38.784,铅源具有壳幔混合源特点。矿床成因类型为沉积变质-岩浆热液叠加型。