First data on the concentrations and distribution of noble metals in Riphean magmatic complexes of the Bashkir meganticlinorium and eastern margin of the East European Platform

The noble metal (PGE and Au) geochemical specialization of igneous rocks of the Bashkir meganticlinorium and adjacent areas of the East European Platform is characterized for the first time. The identical plots of normalized PGE and Au concentrations of igneous rocks in these regions indicate similar conditions and mechanisms of the formation of the noble metal geochemical specialization during the emplacement of magmatic bodies. It is established that a specific feature of noble metal geochemical specialization (the “rhodium anomaly”) in magmatic complexes of the Bashkir meganticlinorium and eastern areas of the East European Platform is determined by the concentrations of noble metals in sulfide minerals (pentlandite); i.e., it is “primary” in origin.     

环渤海地区矿产资源现状和勘查潜力

本文简要论述了环渤海地区黑色、有色、贵金属、非金属、固体燃料和油气矿产资源现状和勘查潜力。在综合研究的基础上,提出环渤海地区仍具有良好的找矿前景。找矿领域集中在已知矿床的边部、外围及深部,以及地质工作程度较低的中西部地区和新类型矿床的找寻等方面。     

Noble metal-bearing ferromanganese deposits in the Kimkan basin,Russian Far East

It has been established that large ferromanganese deposits enriched in noble metals, Co, U, V, and REE in the Kimkan sedimentary basin are confined to Vendian–Cambrian black shales. Lithostratigraphy plays an important role in the localization of such deposits and promising ore-bearing fields. Deposits and occurrences of complex iron and ferromanganese ores are polygenous and polychronous, because they underwent intense hydrothermal alterations with the superposition of noble metal and uranium mineralization in the Cretaceous. Efficient utilization of complex iron ores in the Kimkan open pit needs the construction of a metallurgical plant.     

东乡地区有色、贵金属矿(点)重磁场特征及找矿探讨

东乡地区处赣东北断裂、信江隐伏深断裂相交部位及两侧,地跨两个地体,区内的有色、贵金属矿床大都受断裂作用的控制,与之成矿关系密切的岩体是赛阳关闪长玢岩体.由于断裂带中及两侧分布的不同地层或岩体存在密度差异,导致其上方出现重力梯度带,而重力梯度带及其变异带上分布众多的航磁局部异常,这些局部磁异常是目前全区已知有色、贵金属矿的主要分布地带.结合地质化探资料,掌握重(磁)异常的分布情况时开展矿产勘查及找矿评价有着重要的意义.     

Fractionation of the noble metals by physical processes

During partial melting in the earth’s mantle, the noble metals become fractionated. Os, Ir, Ru, and Rh tend to remain in the mantle residue whereas Pt, Pd, and Re behave mildly incompatible and are sequestered to the silicate melt. There is consensus that sulfide plays a role in the fractionation process; the major noble metal repository in the mantle is sulfide, and most primitive mantle melts are sulfide-saturated when they leave their mantle sources. However, with sulfide–silicate partitioning, the fractionation cannot be modeled properly. All sulfide–silicate partition coefficients are so extremely high that a silicate melt segregating from a mantle source with residual sulfide should be largely platinum-group elements free. We offer a physical alternative to sulfide–silicate chemical partitioning and provide a mechanism of generating a noble metal-rich melt from a sulfide-saturated source: Because sulfide is at least partially molten at asthenospheric temperature, it will behave physically incompatible during melt segregation, and a silicate melt segregating from a mantle residue will entrain molten residual sulfide in suspension and incorporate it in the basaltic pool melt. The noble metal abundances of a basalt then become independent of sulfide–silicate chemical partitioning. They reflect the noble metal abundances in the drained sulfide fraction as well as the total amount of sulfide entrained. Contrary to convention, we suggest that a fertile, sulfide-rich mantle source has more potential to generate a noble metal-enriched basaltic melt than a refractory mantle source depleted by previous partial melting events.     

贵金属配分模式及地质应用

通过与ＲＥＥ模式对比，介绍了贵金属配分模式的构筑方法和组成参数；并对包括地幔岩石、科马提岩和玄武岩在内的各种基性、超基性岩石的特性ＰＧＥ＋Ａｕ配分模式和贵金属分馏机制进行了综述。     

Source identification of methane in groundwater in shale gas development areas: A critical review of the state of the art,prospects, and future challenges

Shale gas exploration and development carry the risk of causing groundwater contamination and enhancing the greenhouse effect through methane leakage. Identifying the source of abnormal methane in groundwater of shale gas development areas is becoming a research hotspot in the fields of groundwater and climate change. This paper reviews the traditional methodology in identifying sources of methane and its deficiency in groundwater application. Then potential and advantages of using noble gases were discussed on how to overcome these limitations of the traditional method. Finally, based on noble gas, the current application status and future challenges of methane source identification in groundwater were analyzed. It can be summarized as:(1) due to chemical and/or microbial processes in the aquifer system, the traditional methodology for methane source identification, which utilizes molecular and isotopic compositions of hydrocarbon gas, has multiple interpretationsand large uncertainties;(2) the non-reactive nature and well-characterized isotopic compositions of noble gases in the atmosphere, hydrosphere, and crust, make noble gases ideal indicators of the sources of methane in groundwater. Moreover, the mechanism of formation and release of crustal noble gas prevent shale gas signatures from being interfered with by natural gas;(3) the key scientific tasks surrounding the use of noble gases for methane source identification include quantitatively separating the components of atmosphere-derived, mantle-derived, and crust-derived noble gases from the bulk noble gases in groundwater. It quantifies the solubility fractionation of noble gases induced by water-gas interaction during methane migration to the aquifer. The application of noble gases can bring a new perspective to tracing the source of methane in groundwater and is of great significance to the protection of groundwater quality in shale gas development areas and mitigation of climate change.     

Prospects of large-scale noble metal mineralization in the Upper Selemdzha minerogenic zone (by the example of the Malomyr and Sagur-Semertak ore clusters)

The Upper Selemdzha minerogenic zone, which has the potential for noble metal mineralization in the Upper Amur, has been studied. It is confined to the thick strata of Paleozoic terrigeneous-sedimentary rocks (sandstones, siltstones, clay schists, packages of their thin rhythmical interlayering, sedimentary breccias, and conglomerates) in the Tokura subzone of the Selemdzha-Kerbinsk zone in the Amur-Okhotsk area of the Mongol-Okhotsk system, overlain by Early Cretaceous volcanogenic sedimentary rocks and intruded by Early Cretaceous quartz diorites, granodiorites, and dacites. In the Malomyr and Sagur-Semertak ore clusters, there are a few known potential deposits of noble metals and ore occurrences; when studied and prospected, they can exhibit vein-veinlet noble metal mineralization with rich contents of gold and platinoids in ore columns and metasomatic deposits.     

Sources for gold,palladium and iridium in deep-sea sediments

Deep-sea sediment cores, one from the Caribbean (calcareous ooze) and three from the Pacific-Antarctic basin (Globigerina ooze, siliceous ooze and pelagic clay) were analysed for Au, Pd, Ir and Mn by neutron activation. The average noble metal contents for 37 samples are: Au (ppb) Pd (ppb) Ir (ppb) 1.05 ± 0.9 3.5 ± 2.8 0.31 ± 0.14 Biogenic and lithogenic (terrigenous) constituents account for much of the noble metal in these sediments. The average noble metal content, particularly that of Au and Ir, shows little variation over the entire suite of four cores despite large differences in the proportions of biogenic and lithogenic fractions. In general neither component is a markedly more significant noble metal sink than the other. However, a strong correlation between Au and CaCO₃ in the Caribbean calcareous ooze suggests that the biogenic fraction is a significant concentrator in this core.Palladium content is more variable than that of Au or Ir and in two of the Antarctic cores some Pd, probably of hydrogenous origin, is present.The Ir content of all cores is higher than that expected of purely terrigenous sources and there is little suggestion of biogenic concentration of the metal. $\text{Au}\text{Ir}$ ratios differ greatly from average continental crust but are similar to oceanic crust. In one of the Antarctic cores some Ir of hydrogenous and of extraterrestrial origin may be present.     

Types and Ore-forming Conditions of Gold Deposits in the Jinsha River-Lancang River-Nujiang River Area

The Jinsha River-Lancang River-Nujiang River area is one of the important prospect areas for noble metal and nonferous metal deposits of China. Of a great variety of gold deposits present in this area, the following types seem to be economically most valuable and promising: tectonic alteration type in ophiolitic melange; polymetallic quartz vein type related to intermediate-acid intrusions; finely disseminated type in fracture zones; mixed hydrothermal type in tectonic fractures of carbonate rocks; hydrothermal type related to subvolcanic rocks; volcanic-hot spring type; submarine volcano exhalation-sedimentary-hydrothermal reformation type. Metallogenic epochs are exclusively Mesozoic and Cenozoic, and ore deposits and orebodies are controlled by linear structures. Magmatic activity has affected gold mineralization in varying degrees, and gold deposits are basically of mesothermal-epithermal type with ubiquitous and intense alterations. Ore-forming materials and hydrothermal solutions show multi-source character.     

Synthesis of PGE sulfide standards for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS)

Sulfide compositions with known Re, Os, Ir, Ru, Rh, Pt, and Pd contents are synthesized to be used as standards for noble metal analysis in solid solution in sulfides. Major elements were added as metals and elemental S. The noble metals, i.e. 35 and 60 ppm each, were added as solutions by micro syringe. Following synthesis at 1 atm the sulfides were sintered at 1.5 to 2 GPa to obtain pellets with theoretical density. Aliquots of the pellets were analysed by isotope dilution ICP-MS for bulk Re and platinum-group elements (PGE). The spatial noble metal distribution was investigated with an ArF excimer laser coupled to a single collector ICP mass spectrometer. Sample homogeneity is shown to depend on the metal/S spectrum and the major element composition of the sulfide, as well as on more subtle factors like oxygen partial pressure during synthesis, run temperature, and degree of partial melting. The most homogeneous sulfide composition is a (Fe,Ni)_{1 − x} S monosulfide with 5 wt % Ni and 1-sigma variations in ³⁴S-normalized noble metal count rates of <3.6%. Nearly as homogeneous is a pure Fe_{1 − x} S monosulfide with 1-sigma variations in ³⁴S-normalized noble metal count rates of <5.8 %. A Cu-bearing Fe_{1 − x} S monosulfide with 2 wt % Cu was found to be considerably more heterogeneous, suggesting that Cu in solid solution in monosulfides promotes noble metal heterogeneity. The sulfide composition least suitable for the synthesis of noble metal sulfide standards is NiS.     

Study of Noble Metal Elements in Lower Cambrian Black Rock Series of Guizhou-Hunan Provinces, China

ＩＮＴＲＯＤＵＣＴＩＯＮＬｏｗｅｒＣａｍｂｒｉａｎｂｌａｃｋｒｏｃｋｓｅｒｉｅｓｅｘｉｓｔｓｂｒｏａｄｌｙｉｎｍｏｒｅｔｈａｎ１０ｐｒｏｖｉｎｃｅｓｉｎＳｏｕｔｈＣｈｉｎａ（Ｃｈｅｎｅｔａｌ．,１９９０）．Ｔｈｅｂｏｔｏｍｏｆｔｈｅｓｅｒｉｅｓｓｐｏ...     

Metal concentrations and carbonaceous matter in the black shale type rocks of the Urals

Here, the results of examination of black shale type rocks from the Urals for noble metal mineralization are presented for the first time: they have been obtained using atomic–absorption spectrometry along with data of a complex analysis of a carbon mineralization applying a complex of high-resolution techniques. The data acquired demonstrate anomalously high Au concentrations in all the rocks examined. The carbon matter occurs in a wide range of phase states, including nanocrystalline graphite, carbon nanofiber, nanoglobules, diamond-like carbon, and bitumens. The black shale type rocks were found to be promising for further studies in order to seek industrially valuable objects including in areas of the northern part of the Urals.     

Geochemistry of Fe-Mn deposits of the Atlantic Ocean (Strakhov Basin,Elena Seamount,and Cape Verde Quadrangle)

Fe-Mn deposits for this research were sampled at the floor of the Atlantic Ocean in the Cape Verde Quadrangle, Elena Seamount, and Strakhov Basin. The samples were analyzed for major components and for Ni, Co, Cu, P, S, and other trace elements by ICP-AES. Common features in the distribution of REE (high positive Ce anomalies) were discovered, and trends in the distribution of elements with depths are revealed. As, Pb, Sr, Co, and Pt are prone to accumulate in shallower water areas, whereas Cu and Li are enriched at deeper water territories. The samples are analyzed in compliance with Andreev’s classification, and their noble metal composition is determined.     

Noble metal specialization of Lower and Middle Riphean terrigenous rocks in the South Urals

Results of the study of noble metal specialization of Lower and Middle Riphean terrigenous rocks in the Bashkir Anticlinorium (South Urals) are reported. The study revealed their genetic differences in the relatively unaltered, i.e., “background” terrigenous rocks in type sections of the Burzyan and Yurmatau groups and in sedimentary rocks of the same stratigraphic levels from tectonic zones subjected to local dynamothermal metamorphism of the greenschist facies and intruded by mafic rocks. It has been established that Ru serves as a geochemical marker of the impact of magmatic processes on sedimentary rocks and the redistribution of noble metals during metamorphism and local metasomatism. A generalized model is proposed for the formation of noble metal geochemical specialization of Lower and Middle Riphean terrigenous rocks in the South Urals.     

Metallogenic analysis of the type gold-bearing districts in the southern and eastern framing of the North Asian Craton: Geotectonic position,geological structure,and specifics of formation

Large ore-placer districts in the southern and eastern framing of the North Asian Craton (Bodaibo, Upper Selemdzha, South Verkhoyansk, and Ten’ka) are characterized by some common features such as the confinement to the areas of the decreased crustal thickness and gravity gradient zones traced by deep-seated faults; the fold-thrust structure of the terrigenous-black-shale sequences; the phyllitic, greenschist, and sometimes epidote-amphibolite metamorphism of the ore-bearing rocks; and the complex and long history of the Au accumulation, which involved the subsequent stepwise change from the ore-preparatory to the ore-generating stages. The latter stage is spatially and temporally related with manifestations of orogenic (volcanoplutonic) magmatism, which produced mineralization of the gold-quartz, gold-sulfidequartz, gold-black shale, gold-rare metal, and gold-silver formations. The peculiarities of their spatial relations (juxtaposition-superposition or lateral zoning) determine the scales of the noble metal concentration, the economic significance of the deposits, and the metallogenic potential of the regions. The revealed similarity in the evolution and structure of the compared districts should be taken into account in choosing new promising areas and estimating the potential gold-bearing territories in the framing of the North-Asian and other cratons.     

硫化物矿物中痕量元素的激光剥蚀-电感耦合等离子体质谱微区分析进展

第一行过渡金属元素及痕量贵金属元素高度富集在硫化物矿物中,常形成具有工业意义的矿床,使得硫化物具有重大的经济价值。对天然硫化物矿物中的这些痕量金属元素丰度及其分布的研究,在矿石成因学、经济地质学、环境地球化学等领域具有重要的应用价值。激光剥蚀-电感耦合等离子体质谱(LA-ICP-MS)微区分析技术是一种强大的痕量元素分析工具,非常适合直接分析硫化物矿物中痕量元素的浓度及其空间分布。由于硫化物的激光剥蚀特性与硅酸盐及氧化物不同,分析校准用的标准物质又极度缺乏,严重阻碍了这一技术在硫化物矿物微区分析中的应用。本文评述了硫化物简介、硫化物中痕量金属元素分析的意义、LA-ICP-MS微区分析技术在硫化物矿物痕量元素分析中的优势及近年来的应用进展、硫化物分析中的干扰与校准、包含铂族元素及金的硫化物标准物质的研制进展及合成硫化物标准物质最有应用前景的方法。     

Nanoparticles of noble metals in the supergene zone

Formation of noble metal nanoparticles is related to various geological processes in the supergene zone. Dispersed mineral phases appear during weathering of rocks with active participation of microorganisms, formation of soil, in aqueous medium and atmosphere. Invisible gold and other noble metals are incorporated into oxides, hydroxides, and sulfides, as well as in dispersed organic and inorganic carbonic matter. Sulfide minerals that occur in bedrocks and ores unaltered by exogenic processes and in cementation zone are among the main concentrators of noble metal nanoparticles. The ability of gold particles to disaggregate is well-known and creates problems in technological and analytical practice. When Au and PGE nanoparticles and clusters occur, these problems are augmented because of their unusual reactions and physicochemical properties. The studied gold, magnetite, titanomagnetite and pyrite microspherules from cementation zone and clay minerals of laterites in Republic of Guinea widen the knowledge of their abundance and inferred formation conditions, in particular, in the contemporary supergene zone. Morphology and composition of micrometer-sized Au mineral spherules were studied with SEM and laser microprobe. The newly formed segregations of secondary gold on the surface of its residual grains were also an object of investigation. The character of such overgrowths is the most indicative for nanoparticles. The newly formed Au particles provide evidence for redistribution of ultradispersed gold during weathering. There are serious prerequisites to state that microorganisms substantially control unusual nano-sized microspherical morphology of gold particles in the supergene zone. This is supported by experiments indicating active absorption of gold by microorganisms and direct evidence for participation of Ralstonia metallidurans bacteria in the formation of peculiar corroded bacteriomorphic surface of gold grains. In addition, the areas enriched in carbon and nitrogen have been detected with SEM on the surface of gold spherules from Guinea. Such organic compounds as serine, alanine, and glycine are identified on their surface with Raman spectroscopy. The experiments have been carried out and new data have been obtained indicating the role of micromycetes in concentration and distribution of noble metals in ferromanganese nodules of the World Ocean. Au and Pt were detected in the system with radioisotopes. It has been established that two forms of gold distribution develop within pseudomorphs of fungi colonies: (1) as pseudomorphic concentrates and (2) dispersed form unrelated to the colony structure. Inhomogeneities in distribution of dispersed platinum are manifested in the form of linear anomalies with elevated concentrations at the margins of the colonies.     

富钴结壳中贵金属元素的特征

对太平洋CL、CM海山调查时获取9个富钴结壳样品,采用化学处理及ICP-MS法进行分析。对贵金属元素含量分布特征、富集因子、标准化模式以及来源进行探讨和研究。结果表明：海山结壳中贵金属元素Ag、Au、Ru、Rh、Pd、Pt等的平均含量分别为： 1.05×10^-6、2.3×10^-6、15.6×10^-9、22.3×10^-9、2.39×10^-9和432×10^-9。与结核、洋壳及陆地矿石的Pd/（Pt+Pd）、Pt/（Pt+Pd）和Pd/Pt等贵金属元素的比值相比,大洋富钴结壳的 Pd/（Pt+Pd） 比值最低,为0.006;其次是结核,为0.06;洋壳为0.08;陆地矿石的Pd/（Pt+Pd）比值较大,为0.35～0.65。结壳的Pt/（Pt+Pd）比值最高,为0.99;其次是结核,为0.95;洋壳为0.93;陆地矿石的Pt/（Pt+Pd）比值相对较低,为0.33～0.65。统计分析显示了不同区域、不同环境中贵金属元素的特征参数变化,并且说明富钴结壳中富铂、金、钌、铑,而贫钯。贵金属元素标准化显示,海山富钴结壳均存在着Pt、Au正异常和Pd的负异常,其中Au异常幅度与结核的Au异常一致。     

Noble Metal Concentrations in Shoshonitic Lamprophyres: Analysis of the Weekend Dykes, Eastern Shore, Nova Scotia, Canada

Devonian, spessartite dykes, known as the Weekend dykes, onthe Eastern Shore of Nova Scotia contain panidiomorphic texturesand mineral (amphibole, clinopyroxene, and biotite) compositionstypical of shoshonitic lamprophyres. The major element and traceelement geochemistry of the Weekend dykes is also representativeof shoshonitic lamprophyres with high large ion lithophile elementconcentrations (LILE, e.g., Rb, K, and Ba) relative to the lightrare earth elements (LREE, e.g., La) and very low Nb and Ti.Only Ta concentrations are uncharacteristically high relativeto Nb and Ti. The dykes are variably evolved but many samplesshow primitive compositions with high mgnumber [>0.70, wheremg-number=Mg/(Mg+09total Fe) atomic] high MgO and Ni concentrations(>10 wt.% and 150 ppm, respectively), and low heavy REE concentrations.All noble metal concentrations (Au, Pd, Pt, Rh, Ru, and Ir)tend to be lower in evolved samples than in primitive rocks,suggesting that evolved magmas were efficiently scavenged byimmiscible sulphide globules and that shoshonitic lamprophyreplutons may hold economic promise for the platinum-group elements(PGE). Noble metal abundances in even the most primitive rocksare low compared with many basaltic rocks excepting mid-oceanridge basalt (MORB). This makes doubtful the idea that Megumagroup mesothermal gold deposits, which are spatially and temporallyassociated with the dykes, derived their gold from the lamprophyres.Models that explain PGE concentrations and Pd/Ir ratios in awide variety of mafic rocks suggest that the low noble metalabundances probably reflect metal retention in mantle sulphides,olivine, and PGE alloys at low percentages of melting. However,noble metal abundances are higher than expected if the oceanicslab was involved in the melting process or if the source regionresembled that for most MORB, which appears to have low PGE.Mantle metasomatism represents an unlikely explanation for thePGE abundances, which are equivalent to those expected in alkalinehot-spot magmas. The high PGE abundances of hot-spot magmas(compared with MORB) may be related to the incorporation ofcore materials in deep mantle plumes. Presumably the hot-spotlikemantle became part of the subcontinental lithospheric mantlebefore the subduction and transpressional event that producedthe shoshonitic magmas.