Sedimentary Environment and Mineralization of the Black Shale Polymetallic Layer in the Early Cambrian,SW China:Constraints from in situ LA-ICP-MS Analysis of Pyrite

A polymetallic layer is usually developed at the bottom of the early Cambrian black shale in Guizhou Province.The mineral that makes up the polymetallic layer is related to the sedimentary facies.To analyze the differentiation mechanism between polymetallic deposits(Ni-Mo and V),the Zhijin Gezhongwu profile located in the outer shelf and the Sansui Haishan V deposit located in the lower slope are selected to study the in situ sulfur isotopes and trace elements of pyrite.The results show that δ^(34)S values of pyrite vary widely from−7.8‰to 28‰in the Gezhongwu profile,while the δ^(34)S values are relatively uniform(from 27.8‰to 38.4‰)in the Haishan profile.The isotopic S composition is consistent with the transition that occurs in the sedimentary phase from the shelf to the deep sea on the transgressive Yangtze platform;this indicates that the δ^(34)SO_(4)^(2−)values in seawater must be differently distributed in depositional environments.The sulfur in the Ni-Mo layer is produced after the mixing of seawater and hydrothermal fluid,while the V layer mainly originates from seawater.Overall,the Ni-Mo and V deposits have been differentiated primarily on the basis of the combined effect of continental weathering and hydrothermal fluid.

Study on the occurrence state of indium in sphalerite of Dulong Sn–Zn–In polymetallic deposit,Southwest China

The Dulong deposit,located in the Laojunshan area of southeastern Yunnan,China,is an important polymetallic deposit due to its high reserves of tin,zinc,and indium.The occurrence state of indium is critical for understanding its supernormal enrichment mechanism.Previous studies investigated the occurrence state of indium(including the valence state)based on the indium content in sphalerite and the correlation between metal concentrations.However,more evidence is needed to better constrain indium occurrence at the micro-,nano-,or even atomic scale.In this study,EPMA-FIB-SEM-TEM and XPS techniques were employed to investigate the indium distribution characteristics and occurrence state in sphalerite from the Dulong Sn–Zn–In polymetallic deposit.The maximum concentration of indium in the indium-rich sphalerite samples is 0.37%,and the results of the EPMA analysis showed a relatively homogeneous distribution of indium in sphalerite.The FIB-SEM-TEM results demonstrated that the lattice stripes of sphalerite were periodically and continuously distributed at the nanoscale,confirming that sphalerite in the deposit was an excellent single crystal structure,and the peak heights of the various characteristic peaks of indium in the EDX spectra were relatively close to each other,with no distinct peaks of high indium content.In addition,the XPS results indicate that the element valence state of indium in sphalerite is In^(3+),and it combines with S^(2-)to form a bond.These results indicate that indium in sphalerite of the Dulong deposit is uniformly distributed at both the micro-and nanoscale,and there is no indium-independent mineral.In^(3+)enters the crystal lattice of sphalerite by replacing Zn2+in the form of isomorphic substitution.

Contamination, Precision and Accuracy of pXRF Geochemistry: Case Study-Polymetals Resources Ltd., Mansala Gold Project, Siguiri Basin, Northeast Guinea

Quality Assurance and Quality Control (QA/QC) is a critical component of all pXRF geochemistry processes. A properly constructed pXRF QA/QC programme identifies possible instrumental errors and provides a means of securing fit for purpose data from the pXRF programme. pXRF QA/QC programmes involve daily contamination, precision, and accuracy checks to ensure the generation of fit for purpose data. In the exploration field or mine-site, pXRF is capable of producing extremely valuable data that is fit for purpose if calibrated properly. However, it should not be used as a replacement for acquiring data from an accredited laboratory using established analytical techniques that produce high quality data. Contamination is the checking of the cleanliness of the analyser window or the presence of dust in the measuring environment. At Polymetals, using Olympus Vanta C-Series pXRF analyser with silver anode, contamination is assessed by measuring an instrumental blank (SiO2), to identify any foreign matter on the analyser window. Assuming that the window film is new, and the fused silica disc is dust free, only Si should be detected. If any other significant element is detected, the film is replaced, and the test is re-run. Accuracy is a measure of how close the measured value is to the true value and is assessed by measuring the abundance of selected elements contained within a Certified Reference Material (CRM) or the NIST check standard sample supplied with the pXRF analyser. Elements of interest must report within ±20% of the standard value. Precision is a measure of how close repeat measurements are to one another and is assessed by taking multiple readings on a particular sample to determine the stability of the analyser. The Relative Standard Deviation (RSD) of the replicate measurements is then calculated. The RSD values should be less than 20% for most analytes, except chromium, for which the value should be less than 30%. Once contamination, accuracy and precision are within accepted limits, the batch/daily measurements are considered to have passed the QA/QC protocol. The data is thus fit for purpose and transferred to the data file. Any batch/daily measurement reported to have failed due to instrumental errors is re-analysed. QA/QC protocols should be applied to each project. The QQ/QC protocols instituted after the pXRF samples meeting the quality sample conditions thus pulverised dry samples in pXRF sample cup covered with thin pXRF films, are used to generate fit for purpose data from soils samples at Mansala which is used to generate pathfinder element(s) to delineate anomalous pathfinder trends for further exploration works.

Geochemistry of Platinum Group and Rare Earth Elements of the Polymetallic Layer in the Lower Cambrian,Weng'an,Guizhou Province

The black shales of the Lower Cambrian Niutitang Formation in Weng＇an, on the Yangtze platform of south China, contain voluminous polymetallic sulfide deposits. A comprehensive geochemical investigation of trace, rare earth, and platinum group elements （PGE） has been undertaken in order to discuss its ore genesis and correlation with the tectono-depositional setting. The ore-bearing layers enrich molybdenum （Mo）, nickel （Ni）, vanadium （V）, lead （Pb）, strontium （Sr）, barium （Ba）, uranium （U）, arsenic （As）, and rare earth elements （REE） in abundance. High uranium/ thorium （U/Th） ratios （U/Th〉I） indicated that mineralization was mainly influenced by the hydrothermal process. The 8U value was above 1.9, showing a reducing sedimentary condition. The REE patterns showed high enrichment in light rare earth elements （LREE） （heavy rare earth elements （HREE） （LREE/HREE=5-17）, slightly negative europium （Eu） and cerium （Ce） anomalies （δEu=0.81- 0.93）, and positive Ce anomalies （δCe=0.76-1.12）. PGE abundance was characterized by the PGE-type distribution patterns, enriching platinum （Pt）, palladium （Pd）, ruthenium （Ru） and osmium （Os）. The Pt/Pd ratio was 0.8, which is close to the ratios of seawater and ultramafic rocks. All of these geochemical features suggest that the mineralization was triggered by hydrothermal activity in an extensional setting in the context of break-up of the Rodinian supercontinent.

Late Mesozoic Ore-forming Events in the Ningwu Ore District, Middle-Lower Yangtze River Polymetallic Ore Belt, East China: Evidence from Zircon U-Pb Geochronology and Hf Isotopic Compositions of the Granodioritic Stocks

Late Mesozoic volcanic-subvolcanic rocks and related iron deposits, known as porphyry iron deposits in China, are widespread in the Ningwu ore district （Cretaceous basin） of the middle-lower Yangtze River polymetallic ore belt, East China. Two types of Late Mesozoic magmatic rocks are exposed： one is dioritic rocks closely related to iron mineralization as the hosted rock, and the other one is granodioritic （-granitic） rocks that cut the ore bodies. To understand the age of the iron mineralization and the ore-forming event, detailed zircon U-Pb dating and Hf isotope measurement were performed on granodioritic stocks in the Washan, Gaocun-Nanshan, Dongshan and Heshangqiao iron deposits in the basin. Four emplacement and crystallization （typically for zircons） ages of granodioritic rocks were measured as 126.1±0.5 Ma, 126.8±0.5 Ma, 127.3±0.5 Ma and 126.3±0.4 Ma, respectively in these four deposits, with the LA-MC-ICP-MS zircon U-Pb method. Based on the above results combined with previous dating, it is inferred that the iron deposits in the Ningwu Cretaceous basin occurred in a very short period of 131-127 Ma. In situ zircon Hf compositions of εHf（t） of the granodiorite are mainly from -3 to -8 and their corresponding 176Hf/177Hf ratio are from 0.28245 to 0.28265, indicating similar characteristics of dioritic rocks in the basin. We infer that granodioritic rocks occurring in the Ningwu ore district have an original relationship with dioritic rocks. These new results provide significant evidence for further study of this ore district so as to understand the ore-forming event in the study area.

Mineral Geochemical Compositions of Tourmalines and Their Significance in the Gejiu Tin Polymetallic Deposits, Yunnan, China

The Gejiu tin polymetallic deposits are located in the southeastern part of Yunnan Province in China. A detailed electronic microprobe study has been carried out to document geochemical compositions of tourmalines from the deposits. The results indicate a systematic change of mineral geochemical compositions, which might be used as a mineral geochemical tracer for post-magmatic hydrothermal fluid, basin fluid and their mixture. The tourmalines from granite are schori with Fe/ （Fe＋Mg） ratios of 0.912-1.00 and Na/（Na＋Ca） ratios of 0.892-0.981. Tourmalines as an inclusion in quartz from the ore bodies are dravite with Fe/（Fe＋Mg） ratios of 0.212-0.519 and Na/（Na＋Ca） ratios of 0.786--0.997. Tourmalines from the country rocks are dravite with Fe/（Fe＋Mg） ratios of 0.313--0.337 and Na/（Na＋Ca） ratio of 0.599-0.723. Tourmalines from cassiterite-tourmaline veins that occur in crannies within the country rocks show distinct optical zoning with alternate occurrence of dravite and schorl, Fe/（Fe＋Mg）=0.374-0.843, Na/（Na＋Ca）=0.538-0.987. It suggests that schorl in granite and dravite in carbonatite are related to magmatic fluid and basin fluid respectively. When magmatic fluid rose up and entered into crannies of the country rocks, consisting mainly of carbonatite, basin fluid would be constantly added to the magmatic fluid. The two types of fluid were mixed in structural crannies of the sedimentary basin accompanied with periodic geochemical oscillations to form material records in chemical composition zonings of tourmalines.

Diversity of Mineralization and Spectrum of the Gejiu Superlarge Tin-Copper Polymetallic Deposit,Yunnan,China

The Gejiu （个旧） deposit is a superlarge tin-copper polymetallic ore-forming concentration area characterized by excellent metallogenic geological settings and advantageous ore-controlling factors. The deposit displays diverse mineralization properties due to different minerals and mineral deposit types. Based on the principal metallogenic factors, metallogenic mechanisms, mineralized components, and occurrence of mineral deposits or ore bodies, the Gejiu mineral district can be divided into 2 combinations of metallogenic series, 4 metallogenic series, 8 subseries, and 27 mineral deposit types. Spatial zonality is evident. The distribution regularity of the elements in both plane and section is Be-W, Sn （Cu, Mo, Bi, Be）-Sn, Pb, Ag-Pb, Zn around a granitic intrusion. The metallogenic epoch is mainly concentrated in the late Yanshanian. During this period, large-scale metallogenic processes related to movement caused by tectonics and magmatism occurred, and a series of magmatic hydrothermal deposits formed. The ore-forming processes can be divided into 4 stages： the silicate stage, the oxide stage, the sulphide stage, and the carbonate stage. Based on the orderliness and diversity （in terms of time, space, and genesis） of the mineralization, the authors have developed a comprehensive spectrum of ore deposits in the Gejiu area. This newly proposed diversity of mineralization and the spectrum developed in this work are useful not only for interpreting the genesis of the Gejiu deposit but also for improving mineral exploration in the area, and in particular, for finding large deposits.

Genetic Types and Metallogenic Model for the Polymetallic Copper–Gold Deposits in the Tongling Ore District, Anhui Province, Eastern China

The Tongling ore district is one of the most economically important ore areas in the Middle–Lower Yangtze River Metallogenic Belt, eastern China. It contains hundreds of polymetallic copper–gold deposits and occurrences. Those deposits are mainly clustered(from west to east) within the Tongguanshan, Shizishan, Xinqiao, Fenghuangshan, and Shatanjiao orefields. Until recently, the majority of these deposits were thought to be skarn-or porphyry–skarn-type deposits; however there have been recent discoveries of numerous vein-type Au, Ag, and Pb-Zn deposits that do not fall into either of these categories. This indicates that there is some uncertainty over this classification. Here, we present the results of several systematic geological studies of representative deposits in the Tongling ore district. From investigation of the ore-controlling structures, lithology of the host rock, mineral assemblages, and the characteristics of the mineralization and alteration within these deposits, three genetic types of deposits(skarn-, porphyry-, and vein-type deposits) have been identified. The spatial and temporal relationships between the orebodies and Yanshanian intrusions combined with the sources of the ore-forming fluids and metals, as well as the geodynamic setting of this ore district, indicate that all three deposit types are genetically related each other and constitute a magmatic–hydrothermal system. This study outlines a model that relates the polymetallic copper–gold porphyry-, skarn-, and vein-type deposits within the Tongling ore district. This model provides a theoretical basis to guide exploration for deep-seated and concealed porphyry-type Cu(–Mo, –Au) deposits as well as shallow vein-type Au, Ag, and Pb–Zn deposits in this area and elsewhere.

^(40)Ar-^(39)Ar Isotopic Dating of the Xianghualing Sn-polymetallic Orefield in Southern Hunan,China and Its Geological Implications

The Xianghualing Sn-polymetallic orefield in Hunan Province, southern China, is a largesize tin orefield. Although numerous studies have been undertaken on this orefield, its genesis, mineralization age, and tectonic setting are still controversial, mainly because of the lack of reliable geochronological data on tin mineralization. The ^40Ar^39Ar stepwise heating dating method was first employed on muscovite from different deposits in this orefield. The muscovite sample from the Xianghualing Sn-polymetallic deposit defines a plateau age of 154.4±1.1 Ma and an isochron age of 151.9±3.0 Ma; muscovite from the Xianghuapu W-polymetallic deposit yields a plateau age of 161.3±1.1 Ma and an isochron age of 160.0±3.2 Ma; muscovite from the Jianfengling greisen-type Sn-polymetallic deposit gives a plateau age of 158.7±1.2 Ma and an isochron age of 160.3±3.2 Ma. The tungsten-tin mineralization ages in the Xianghualing area are therefore restricted within 150-160 Ma. The tungstentin mineralization in Xianghualing occurred at the same time as the regional tin-tungsten mineralization including the Furong tin orefield, Shizhuyuan tungsten-tin polymetallic deposit and Yaogangxian tungsten-polymetallic deposit. Thus, the large-scale tungsten-tin metallogenesis in South China occurring at 160-150 Ma, probably is closely related to asthenospheric upwelling and crustmantle interaction under a geodynamic setting of crustal extension and lithosphere thinning during the transformation of tectonic regimes during the Mid-Late Jurassic.

Rare Earth Elements Composition and Constraint on the Genesis of the Polymetallic Crusts and Nodules in the South China Sea

The rare earth elements（REE） composition of the polymetallic crusts and nodules obtained from the South China Sea（SCS） were analyzed through inductively coupled plasma mass spectrometry.Results revealed great differences in the REE abundances（∑REE） of the SCS polymetallic crusts and nodules; the crusts show the highest ∑REE, whereas the nodules exhibit the lowest ∑REE. The similarity in their NASC-normalized patterns, the enriched light REE（LREE）, the markedly positive Ce anomaly（δCe）, and the non-or weakly positive Eu anomaly（δEu）, suggest that the polymetallic crusts and nodules are of hydrogenetic origin. Moreover, the REE contents and their relevant parameters are quite different among the various layers of the crusts and nodules, which probably results from the different marginal sea environments and mineral assemblages of the samples. The growth profiles of the SCS polymetallic crusts and nodules reveal the tendency ∑REE and δCe to slightly increase from the outer to the inner layers, suggesting that the growth environments of these samples changed smoothly from an oxidizing to a relatively reducing environment; in addition, the crust ST1 may have experienced a regressive event（sea-level change） during its growth, although the REE composition of the seawater remained relatively stable. On the basis of the regional ∑REE distribution in the SCS crusts and nodules,the samples collected near the northern margin were influenced by terrigenous material more strongly compared with the other samples, and the REE contents are relatively low. Therefore, the special geotectonic environment is a significant factor influencing the abundance of elements, including REE and other trace elements. Compared with the oceanic seamount crusts and deep-sea nodules from other oceans,the SCS polymetallic crusts and nodules exhibit special REE compositions and shale-normalized patterns, implying that the samples are of marginal sea-type Fe-Mn sedimentary deposits, which are strongly affected by the epicontinental environment, and that they grew in a more oxidative seawater environment. This analysis indicates that the oxidized seawater environment and the special nano property of their Fe-Mn minerals enrich the REE adsorption.

The effect of Fe-Mn minerals and seawater interface and enrich-ment mechanism of ore-forming elements of polymetallic crusts and nodules from the South China Sea

Ferromanganese crusts and nodules are important submarine mineral resources that contain various metal elements with significant economic value. In this study, polymetallic crusts and nodules obtained from the South China Sea （SCS） were determined by using X-ray power diffraction （XRD）, Raman spectroscopy （RS）, Fourier transform infrared spectroscopy （FTIR）, and X-ray photoelectron spectroscopy （XPS） to systematically investigate and analyze the mineralogical and spectral characteristics of the Fe-Mn minerals. XRD measurements revealed that the SCS polymetallic crusts and nodules were composed of vernadite, quartz, and plagioclase. The nodules also contained todorokite. The Fe-phase minerals of the SCS crusts and nodules were composed of amorphous Fe oxide/hydroxide, and the Mn- and Fe-phases minerals exhibited relatively poor degrees of crystallization. FTIR results showed that the Fe-Mn minerals in the crusts and nodules included a large number of surface hydroxyl groups. These surface hydroxyl groups contained protons that could provide reactive sites for complexation of ore-forming elements in seawater. XPS results indicated that the surfaces of the Fe-Mn minerals mainly contained Fe, Mn, and O. Fe was present in the trivalent oxidation state, while Mn, which may contain several bivalent oxidation state, was present in the tetravalent and trivalent oxidation states. The SCS polymetallic crusts and nodules were compared with Pacific seamount crusts, and results showed that the surface hydroxyl （-OH） groups of the SCS crusts and nodules numbered more than the lattice oxygen （O^2-）. But the lattice oxygen of Pacific seamount crusts numbered more than the surface hydroxyl groups. This characteristic indicated that the degree of crystallization of Fe-Mn minerals from the Pacific Ocean was higher than that of minerals from the South China Sea. Comprehensive studies showed that ore-forming elements in the interface between seawater and the Fe-Mn minerals in the submarine ferromanganese crusts and nodules employed the following enrichment mechanisms： （1） the metal ion complexed with the surface hydroxyl of Fe-Mn minerals to form hydroxyl complexes, which were connected by coordination bonds or stable inner-sphere complexes that exchanged protons on the mineral surfaces; （2） the charged surfaces of the minerals and metal cations formed outer-sphere complexes, which made up the electrostatic double layer, through electrostatic adsorption; and （3） the metal cations isomorphously exchanged the Mn and Fe ions of the mineral lattice structure.

Ore Genesis for Stratiform Ore Bodies of the Dongfengnanshan Copper Polymetallic Deposit in the Yanbian Area, NE China:Constraints from LA-ICP-MS in situ Trace Elements and Sulfide S–Pb Isotopes

The Dongfengnanshan Cu polymetallic deposit is one representative deposit of the Tianbaoshan ore district in the Yanbian area, northeast(NE) China. There occur two types of ore bodies in this deposit, the stratiform ore bodies and veintype ones, controlled by the Early Permian strata and the Late Hercynian diorite intrusion, respectively. Due to the ambiguous genetic type of the stratiform ore bodies, there has been controversy on the relationship between them and veintype ore bodies. To determine the genetic type of stratiform ore bodies, laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS) in situ trace elements and S–Pb isotope analysis have been carried on the sulfides in the stratiform ore bodies. Compared with that in skarn, Mississippi Valley-type(MVT), and epithermal deposits, sphalerite samples in the stratiform ore bodies of the Dongfengnanshan deposit are significantly enriched in Fe, Mn, and In, while depleted in Ga, Ge, and Cd, which is similar to the sphalerite in volcanic-associated massive sulfide(VMS) deposits. Co/Ni ratio of pyrrhotites in the stratiform ore bodies is similar to that in VMS-type deposits. The concentrations of Zn and Cd of chalcopyrites are similar to those of recrystallized VMS-type deposits. These characteristics also reflect the intermediate ore-forming temperature of the stratiform ore bodies in this deposit. Sulfur isotope compositions of sulfides are similar to those of VMS-type deposits, reflecting that sulfur originated from the Permian Miaoling Formation. Lead isotope compositions indicate mixed-source for lead. Moreover, the comparison of the Dongfengnanshan stratiform ore bodies with some VMStype deposits in China and abroad, on the trace elements and S–Pb isotope characteristics of the sulfides reveals that the stratiform ore bodies of the Dongfengnanshan deposit belong to the VMS-type, and have closely genetic relationship with the early Permian marine volcanic sedimentary rocks.

Metallogeny of the Baiyangping Lead-Zinc Polymetallic Ore Concentration Area, Northern Lanping Basin of Yunnan Province, China

The Lanping Basin in the Nujiang-Lancangjiang-Jinshajiang （the Sanjiang） area of northeastern margin of the Tibetan Plateau is an important part of eastern Tethyan metallogenic domain. This basin hosts a number of large unique sediment-hosted Pb-Zn polymetallic deposits or ore districts, such as the Baiyangping ore concentration area which is one of the representative ore district. The Baiyangping ore concentration area can be divided into the east and west ore belts, which were formed in a folded tectogene of the India-Asia continental coUisional setting and was controlled by a large reverse fault. Field observations reveal that the Mesozoic and Cenozoic sedimentary strata were outcropped in the mining area, and that the orebodies are obviously controlled by faults and hosted in sandstone and carbonate rocks. However, the oreforming elements in the east ore belt are mainly Pb-Zn -Sr-Ag, while Pb-Zn-Ag-Cu-Co elements are dominant in the west ore belt. Comparative analysis of the C-O-Sr-S-Pb isotopic compositions suggest that both ore belts had a homogeneous carbon source, and the carbon in hydrothermal calcite is derived from the dissolution of carbonate rock strata; the ore- forming fluids were originated from formation water and precipitate water, which belonged to basin brine fluid system; sulfur was from organic thermal chemical sulfate reduction and biological sulfate reduction; the metal mineralization material was from sedimentary strata and basement, but the difference of the material source of the basement and the strata and the superimposed mineralization of the west ore belt resulted in the difference of metallogenic elements between the eastern and western metallogenic belts. The Pb-Zn mineralization age of both ore belts was contemporary and formed in the same metaliogenetic event. Both thrust formed at the same time and occurred at the Early Oligocene, which is consistent with the age constrained by field geological relationship.

Re-Os Isotopic Dating of a W-Be Polymetallic Deposit in the Southern Qinling Region, China

Objective In recent years, a series of tungsten prospecting breakthroughs have been made in the southern Qinling Mountains. Especially, a new deposit type with a scheelite -beryl-molybdenite assemblage in the Zhen＇an area of Shaanxi Province was firstly discovered. This deposit is currently in a detailed investigation stage, and no detailed study has been yet conducted. This work selected one molybdenite sample from the Be （W） ores in this deposit for Re-Os isotope measurements to define the time limit of tungsten and beryllium mineralization, and to further reveal the ore-forming geological setting of rare metals in the southern Qinling region.

Geochemical Characteristics of Rare Earth Elements in Gejiu Tin Polymetallic Deposits, Yunnan Province, China

In order to get a better understanding of metallogeny, the geochemical characteristics of REE and trace element for Gejiu tin polymetallic deposits were studied by comparing concentrations of REE and trace elements in different type ores and rocks, including skarn-type ore, bedded-type ore, vein-type ore, altered granite, country rocks. Results of this study indicated that the metallogenic matters for different type ores in the study area might be derived from the same origin source, which may be mainly related to granitic activities. Furthermore, there are some differences in concentrations of REE in different ores due to their different depositional mechanism during that time. LREE concentrations were enriched relatively in the vein-type ores and the bedded-type ores with relatively low total REE concentrations, whereas total REE concentrations were higher in the skarn-type ores with LREE and HREE concentrations in wide variation ranges.

New Zircon U-Pb Age of the Super-Large Lijiagou Spodumene Deposit in Songpan Garze Fold Belt, Eastern Tibet： Implications for Early Jurassic Rare-Metal Polymetallic Event

Objective The Songpan-Garze Fold Belt(SGFB),located in the eastern part of the Tibet Plateau and west of the Sichuan Basin,is an important pegmatite province in China.Some famous pegmatite type deposits occur in the SGFB,including the Xuebaoding,Jiajika,Keeryin rare metal deposits and Danba muscovite deposit(Li Jiankang et al.,2015).The newly discovered super-large Lijiagou

Quantitative prediction process and evaluation method for seafloor polymetallic sulfide resources

Seafloor polymetallic sulfide resources exhibit significant development potential. In 2011, China received the exploration rights for 10,000 km2 of a polymetallic sulfides area in the Southwest Indian Ocean; China will be permitted to retain only 25% of the area in 2021. However, an exploration of seafioor hydrothermal sulfide deposits in China remains in the initial stage. According to the quantitative prediction theory and the exploration status of seafloor sulfides, this paper systematically proposes a quantitative prediction evaluation process of oceanic polymetallic sulfide resources and divides it into three stages： prediction in a large area, prediction in the prospecting region, and the verification and evaluation of targets. The first two stages of the prediction process have been employed in seafloor sulfides prospecting of the Chinese contract area. The results of stage one suggest that the Chinese contract area is located in the high posterior probability area, which indicates good prospecting potential area in the Indian Ocean. In stage two, the Chinese contract area of 48^-52~E has the highest posterior probability value, which can be selected as the reserved region for additional exploration. In stage three, the method of numerical simulation is employed to reproduce the ore-forming process of sulfides to verify the accuracy of the reserved targets obtained from the three-stage prediction. By narrowing the exploration area and gradually improving the exploration accuracy, the prediction will provide a basis for the exploration and exploitation of seafloor polymetallic sulfide resources.

He-Ar Isotopic Systematics of Fluid Inclusions in Pyrites from PGEpolymetallic Deposits in Lower Cambrian Black Rock Series, South China

He-Ar isotopic compositions of fluid inclusions trapped in pyrites from some representative PGE-polymetallic deposits in Lower Cambrian black rock series in South China were analyzed by using an inert gas isotopic mass spectrometer. The results show that the ore-forming fluids possess a low 3He/4He ratio, varying from 0.43×10-8 to 26.39×10-8, with corresponding R/Ra value of 0.003-0.189. The 40Ar/36Ar ratios are 258-287, close to those of air saturated water (ASW). He-Ar isotopic indicator studies show that the ore-forming fluids were mainly derived from the formation water or basinal hot brine and sea water, while the content of mantle-derived fluid or deep-derived magmatic water might be negligible. The PGE-polymetallic mineralization might be related to the evolution of the Caledonian miogeosynclines distributed along the southern margin of the Yangtze Craton. During the Early Cambrian, the formation water or basinal hot brine trapped in Caledonian basins which accumulated giant thick sediments was expelled and migrated laterally along strata because of the pressure generated by overlying sediments. The basinal hot brine ascended along faults, mixed with sea water and finally deposited ore minerals.

Lead Isotopic Composition and Lead Source in the Bainiuchang Ag-polymetallic Deposit, Yunnan Province, China

The Bainiuchang deposit in Yunnan Province, China, is located geographically between the Gejiu ore field and the Dulong ore field. In addition to the 〉7000 t Ag reserves, the deposit also boasts of large-scale Pb, Zn and Sn reserves with a lot of dispersed elements （In, Cd, Ge, Ga, etc.）. We have determined systematically the Pb isotope composition of the deposit. The Pb isotope ratios of the ores that are of sea-floor exhalative sedimentary origin in the northwest of the mining district, are 206pb/204pb = 17.758-18.537, 207pb/204pb = 15.175-15.862 and 206pb/204pb = 37.289-39.424, while those of ores that are of magmatic hydrothermal superimposition origin in the southeast of the mining district, are 206pb/204pb = 17.264-18.359, 207pb/204pb = 14.843-15.683 and 208pb/204pb = 36.481-38.838, respectively. In terms of the Pb isotope composition of feldspar in magmatic rocks or magmatic whole- rock samples from the mining district, we have determined the Pb isotope composition and acquired the Pb isotope ratios as： 206pb/204pb -- 18.224-18.700, 207pb/204pb -- 15.595-15.797 and 208pb/204pb -- 38.193-39.608. Then, in the light of the Pb isotope composition of metamorphic rock samples from the Proterozoic basement exposed in the Dulong ore field, we have determined the Pb isotope composition and obtained the isotope ratios as： 206pb/204pb -- 18.434-19.119, 207pb/204pb -- 15.644-15.693, and 208pb/204pb = 38.514-38.832. And the Pb isotope ratios of Cambrian sedimentary rocks, which are exposed in the Bainiuchang mining district, are 206pb/204pb = 18.307-19.206, 207pb/204pb = 15.622-15.809, and 208pb/204pb = 38.436-39.932. By comparing the two types of ores with respect to their Pb isotope compositions, it is indicated that lead in the Bainiuchang deposit was derived largely from the lower-crust granulite which is earlier than Neoproterozoic in age, but the Yanshanian magmatic hydrothermal fluids probably provided a part of ore-forming elements such as Sn for the ore blocks in the south of the mining district.

3D Geological Modeling with Multi-source Data Integration in Polymetallic Region:A Case Study of Luanchuan,Henan Province,China

The development of 3D geological models involves the integration of large amounts of geological data,as well as additional accessible proprietary lithological, structural,geochemical,geophysical,and borehole data.Luanchuan,the case study area,southwestern Henan Province,is an important molybdenum-tungsten -lead-zinc polymetallic belt in China.