Isotopic Compositions of Sulfur in the Jinshachang Lead–Zinc Deposit, Yunnan, China, and its Implication on the Formation of Sulfur-Bearing Minerals

The Jinshachang lead-zinc deposit is mainly hosted in the Upper Neoproterozoic carbonate rocks of the Dengying Group and located in the Sichuan-Yunnan-Guizhou （SYG） Pb-Zn-Ag multi- metal mineralization area in China. Sulfides minerals including sphalerite, galena and pyrite postdate or coprecipitate with gangue mainly consisting of fluorite, quartz, and barite, making this deposit distinct from most lead-zinc deposits in the SYG. This deposit is controlled by tectonic structures, and most mineralization is located along or near faults zones. Emeishan basalts near the ore district might have contributed to the formation of orebodies. The j34S values of sphalerite, galena, pyrite and barite were estimated to be 3.6‰-13.4‰, 3.7‰-9.0‰, -6.4‰ to 29.2‰ and 32.1‰34.7‰, respectively. In view of the similar δ34S values of barite and sulfates being from the Cambrian strata, the sulfur of barite was likely derived from the Cambrian strata. The homogenization temperatures （T ≈ 134--383℃） of fluid inclusions were not suitable for reducing bacteria, therefore, the bacterial sulfate reduction could not have been an efficient path to generate reduced sulfur in this district. Although thermochemical sulfate reduction process had contributed to the production of reduced sulfur, it was not the main mechanism. Considering other aspects, it can be suggested that sulfur of sulfides should have been derived from magmatic activities. The δ34S values of sphalerite were found to be higher than those of coexisting galena. The equilibrium temperatures calculated by using the sulfur isotopic composition of mineral pairs matched well with the homogenization temperature of fluid inclusions, suggesting that the sulfur isotopic composition in ore-forming fluids had reached a partial equilibrium.

Sulfur isotopic composition of seafloor hydrothermal sediment from the Jade hydrothermal field in the central Okinawa Trough and its geological significance

Eighteen samples of hydrothermal sediments from the Jade hydrothermal field in the central Okinawa Trough have been analyzed. Sulfur isotopic values for 10 sulfide samples vary from 5.2× 10^(-3)to 7.2× 10^(-3), δ^(34)S values for 7 sulfate samples vary from 16.3 × 10^(-3) to 22.3 × 10^(-3), and 1 native sulphur sample has a δ^(34)S value of 8.2 × 10^(-3). The major sources of sulfur for hydrothermal sediment are intermediate to acid volcanic rocks and sea water sulfate, and it is possible that the partial sulfur of hydrothermal sediment is from the pelagic sediment by the interaction between hydrothermal fluid and sediment. The reasons of causing the distinct differences in sulfur isotopic values for sulfide samples from hydrothermal sediment ( compared with other hydrothermal fields), are the differences in the sources of sulfur, the magmatic activity and the tectonic evolution in different hydrothermal fields. The sulfur evolution is a long and complex process in the seafloor hydrothermal system, involving the ascending of heating sea water, the interaction between fluid and volcanic rocks, the mixing of sea water sulfate and sulfur from intermediate to acid volcanic rocks, and the fluid/pelagic-sediment interaction. And the interaction between sea water and intermediate to acid volcanic rocks is an important mechanism for the sulfur evolution in the Jade hydrothermal field.

Origin of natural sulfur-metal chimney in the Tangyin hydrothermal field,Okinawa Trough:constraints from rare earth element and sulfur isotopic compositions

For the first time,we present the rare earth element (REE)and sulfur isotopic composition of hydrothermal precipitates recovered from the Tangyin hydrothermal field (THF),Okinawa Trough at a water depth of 1206 m.The natural sulfur samples exhibit the lowest ∑REE concentrations (∑REE= 0.65×10^-6-4.580×10^-6)followed by metal sulfides (∑REE=1.71×10^-6-11.63×10^-6).By contrast,the natural sulfur-sediment samples have maximum ∑REE concentrations (∑REE=1 1.54×10^-6-33.06×10^-6), significantly lower than those of the volcanic and sediment samples.Nevertheless,the δEu,δCe,(La/Yb)N, La/Sm,(Gd/Yb)N and normalized patterns of the natural sulfur and metal sulfide show the most similarity to the sediment.Most hydrothermal precipitate samples are characterized by enrichments of LREE (LREE/HREE=10.09-24.53)arid slightly negative Eu anomalies or no anomaly (δEu=0.48-0.99),which are different from the hydrothermal fluid from sediment-free mid-oceanic ridges and back-are basins,but identical to the sulfides from the Jade hydrothermal field.The lower temperature and more oxidizing conditions produced by the mixing between seawater and hydrothermal fluids further attenuate the leaching ability of hydrothermal fluid,inducing lower REE concentrations for natural sulfur compared with metal sulfide;meanwhile,the negative Eu anomaly is also weakened or almost absent.The sulfur isotopic compositions of the natural sulfur (δ^34S=3.20‰-5.01‰,mean 4.23 ‰)and metal sulfide samples (δ34S=0.82‰-0.89‰,mean 0.85‰)reveal that the sulfur of the chimney is sourced from magmatic degassing.

The Background of Regional Lead Isotopic Compositions and Its Application in the Lower and Middle Reaches of the Yangtze River and Neighbouring Areas

The paper systematically deals with the background of regional isotopic compo-sitions in the lower and middle reaches of the Yangtze River and neighbouring areas. It isshown that the lead isotopic compositions of different geological formations and units are con-trolled by the primary mantle heterogeneity, dynamic process of crust-mantle interchange,abundances of uraninm, thorium and lead of various layers of the earth and timing. Studies onthe background of regional isotopic compositions may offer significant information forgeochemical regionalization, tracing of sources of ore-forming materials, and regionalprognosis of ore deposits.

Sulfur isotopic composition of modern seafloor hydrothermal sediment and its geological significance

A total of 1 264 sulfur isotopic values for modern seafloor hydrothermel sediments from different hydrothermal fields have been collected.On this basis,combining our sulfur isotpic data for surface hydrothermal sediments from the Jade hydrohtermal field in the Okinawa Trough and the TAG hydrothermal field in the Mid-Atlantic Ridge,respectively,and comparing the sulfur isotopic compositions and analyzing their sources of sulfur in seafloor hydrothermal sediments from different geologic-tectonic setting,the results show that:(1) sulfur isotopic values of sulfides and sulfates in modern seafloor hydrothermal sediments are concentrated in a narrow range,δ 34S values of sulfides vary from 1×10 -3 to 9×10 -3,with a mean of 4.5×10 -3 (n=1042),δ 34S values of sulfates vary from 19×10 -3 to 24×10 -3,with a mean of 21.3×10 -3(n=217);(2) comparing the sulfur isotopic compositions of hydrothermal sediments from the sediment-hosted hydrothermal fields,the range of sulfur isotopic values for hydrothermal sediments from the sediment-free hydrothermal fields is narrow relatively;(3) the differences of sulfur isotopic compositions in sulfides from different hydrothermal fields show the differences in the sources of sulfur.The sulfur of hydrothermal sulfides in the sediment-free mid-ocean ridges is mainly from mid- ocean ridge basalt,and partially from the reduced seawater sulfate,and it is the result of partially reduced seawater sulfate mixed with basaltic sulfur.In the sediment-hosted mid-ocean ridges and the back-arc basins,the volcanics,the sediments and the organic matters also can offer their sulfur for forming hydrothermal sulfides;(4)the variations of sulfur isotopic compositions and the different sources of sulfur for hydrothermal sediments may be attributed to the various physical-chemical characteristics of hydrothermal fluids,the magmatic evolution and the different geologic-tectonic settings of seafloor hydrothermal systems.

Lead Isotopic Composition and Lead Source of the Huogeqi Cu-Pb-Zn Deposit,Inner Mongolia,China

The Huogeqi orefield located on the northern side of Mt. Langshan, Inner Mongolia occurs in the Middle Proterozoic Langshan Group metamorphic rocks, and the orebodies arc stratiform. In the past twenty years, many Chinese geologists have conducted researches on the Huogeqi Cu-Pb-Zn deposit, but there has been still a controversy on its origin. Some advocate that the deposit is of sedimentary-metamorphic rcworking origin, some hold that it is of sea-floor SEDEX origin, and others have a preference for magmatic superimposition origin. The crux of the controversy is that there is no common understanding about the source of ore-forming materials. In this paper, the Pb isotopic compositions of regional Achaean-Early Proterozoic basement rocks, various types of sedimentary- metamorphic rocks and volcanic rocks in the mining district, Late Proterozoic and Hercynian magmatic rocks arc introduced and compared with the orc-lead composition, so as to constrain the source of the ore lead. The result indicates that （1） sulfides in the ores have homogeneous Pb isotopic compositions, showing a narrow variation range. Their ^206pb/^204pb ratios arc within a range of 17.027- 17.317; ^207Pb/^204pb ratios, 15.451-15.786 and ^208Pb/^204pb ratios, 36.747-37.669; （2） the Pb isotopic compositions of the regional Achaean-Early Proterozoic basement rocks arc characteristic of the old Pb isotopic composition at the early-stage evolution of the Earth, which varies over a wider range, reflecting significant differences in Pb isotopic compositions of the ores. All this indicates that the source of ore lead has no bearing on the basement rocks; （3） the sedimentary-metamorphic rocks in the mining district arc characterized by highly variable and more radiogenic Pb isotopic compositions and their Pb isotopic ratios arc obviously higher than those of ores, demonstrating that ore lead did not result from metamorphic rcworking of these rocks; （4） Pb isotopic compositions of Late Proterozoic diorite-gabbro and Hercynian granite are higher than those of ores. Meanwhile, the Pb isotopic compositions of sulfides in the small-sized strata-penetrating mineralized veinlets formed at later stages arc completely consistent with that of sulfides in stratiform-banded ores, suggesting that these veiniets arc the product of autochthonous rcworking of the stratiform-banded ores during the period of metamorphism and the late magmatic superimposition-mineralization can be excluded; （5） amphibolite, whose protolith is basic volcanic rocks, has the same Pb isotopic compositions as ores, implying that ore lead was derived probably from basic volcanism. So, the source of ore-forming materials for the Huogeqi deposit is like that of the volcanic massive sulfide （VMS） deposits. However, the orebodies do not occur directly within the volcanic rocks, and instead they overlie the volcanic rocks, showing some differences from those typical VMS-type deposits.

Sulfur isotopic composition of the Tianqiao Pb-Zn ore deposit,Northwest Guizhou Province,China:Implications for the source of sulfur in the ore-forming fluids

The Tianqiao Pb-Zn ore deposit of Guizhou Province, China, is located in the mid-east of the Sichuan-Yunnan-Guizhou Pb-Zn-Ag multi-metallic mineralization area, which is representative of the Pb-Zn ore de-posits in this area. It consists of three main orebodies, whose Pb+Zn reserves are more than 0.2 million ton. This paper analyzes the sulfur isotopic composition of these orebodies. The data show that the ore minerals (galena, sphalerite, pyrite) in these orebodies are enriched in heavy sulfur, with δ34SV-CDT values varying between 8.35‰ and 14.44‰, i.e. the δ34SV-CDT values of pyrite are between 12.81‰ and 14.44‰, the mean value is 13.40‰; the δ34SV-CDT values of sphalerite are range from 10.87‰ to 14.00‰, the mean value is 12.53‰; the δ34SV-CDT values of galena are range from 8.35‰ to 9.83‰, the mean value is 8.84‰, and they have the feature of δ34Spyrite>δ34Ssphalerite>δ34Sgalena, which indicates the sulfur isotope in ore-forming fluids has attained equilibrium. The δ34S V-CDT values of the deposit are close to those of sulfates from carbonate strata of different ages in the ore-field (15‰), which suggests that the sulfur in the ore-forming fluids should be derived from the thermo-chemical sulfate reduction of sulfates from the sedimentary strata.

Sulfur isotopic composition of the Bainiuchang super-large Ag polymetallic deposit,Yunnan Province,China: Implications for the source of sulfur in ore-forming fluids

The Bainiuchang deposit in Yunnan Province, China, is located geographically between the Gejiu ore field and the Dulong ore field. In addition to >7000 t Ag reserves, the deposit possesses large-scale Pb, Zn, Sn reserves and a mass of dispersed elements (i.e., In, Cd, Ge, Ga, etc.). Based on systematic studies of sulfur isotopic composition, the authors conclude: The Bainiuchang deposit experienced two epochs of metallogenesis, i.e., the Middle-Cambrian sea-floor exhalative sedimentary metallogenic epoch and the Yanshanian magmatic hydrothermal superimposition metallogenic epoch. In the two metallogenic epochs, the δ34S values of sulfides were all near 0, showing a tendency of being enriched slightly in heavy sulfur. The δ34S values of sulfides in the early metallogenic epoch are within the range of 2‰–5‰ with a peak value range of 2‰–3‰ and an average of 3.0‰, and those of sulfides in the late metallogenic epoch are within the range of 2‰–6‰ with a peak value of 3‰–4‰ and an average of 3.9‰. For the single metallogenic epoch, sulfur in the ore-forming fluids in the early epoch already reached isotopic equilibrium and was derived mainly from underneath the magma chamber or basement metamorphic igneous rocks. Sulfur in the sulfides in the late epoch was derived mainly from magmatic hydrothermal fluids formed in the process of remelting of the basement metamorphic igneous rocks.

Textures, trace element compositions, and sulfur isotopes of pyrite from the Honghai volcanogenic massive sulfide deposit:Implications for ore genesis and mineral exploration

In this paper, we present textures, trace element compositions, and sulfur isotope data for pyrite from the Honghai volcanogenic massive sulfide deposit to place new constraints on the source and evolution of the ore-forming fluids and provide insights into the ore genesis with implications for future exploration. The Honghai deposit consists of upper lenticular ores comprising massive sulfides that are underlain by stockwork and disseminated sulfides. The textural and isotopic characteristics of the synsedimentary framboidal pyrite(Syn-Py) indicate its formation by biogenetic processes. Coarse-grained pyrite generations(M-Py1, M-Py2, and M-Py3) from the massive sulfides have high Au, Ag, Cu, Zn, Pb, Sb, and Tl concentrations and low Co, Se, Te, Ti, and Sn concentrations, indicating that they precipitated from metal-rich, low-to intermediate-temperature,oxidizing fluids. The high Te, Ti, and Sn concentrations and high Co/Ni ratios in the massive pyrite(M-Py4) associated with magnetite in the massive sulfide lenses, as well as the high Ti, V, Cr, and Ni concentrations and low Al, Mn, and Zn concentrations in the magnetite, suggest that the coexisting M-Py4 and magnetite precipitated under oxidizing and hightemperature(300℃ to 500℃) conditions. In contrast, pyrite grains from the underlying stockwork and veins(V-Py1, V-Py2, and V-Py3) are characterized by low Au, Ag, Cu, Zn, Pb, Sb, and Tl concentrations coupled with high Co, Se, Te, and Ti concentrations and high Co/Ni ratios, which are interpreted in terms of reducing and high-temperature ore-forming fluids. The large variations in δ^(34)S values from-6.4‰ to +29.9‰ suggest that the ore-forming fluids were derived from magmatic source that were significantly modified by seawater. The spatial variations of trace element assemblages of pyrite from different levels of the main massive orebodies can be used as an indicator for mineral exploration of Cu-Zn ores in the Honghai deposit.Although no significant difference in δ34S values is observed between the upper massive sulfide lenses and lower stockwork/vein zone, the spiky δ34S pattern noted in the massive pyrite can be used as a marker for the main massive orebodies.

Sulfur isotopic composition of Yellow and Yangtze rivers and uplift of the Qinghai-Xizang Plateau

THE sulfur isotopic composition of dissolved sulfate in any rivers has been recognized as a mixture of thesulfur derived from the soil, bedrock and the atmosphere. The measurement of the sulfur isotopic composition in a river water can provide background information on the biogeochemical cycling of sulfur in theriver basin. So far, however, little work has been done on sulfur isotope in the watersheds of the majorrivers of the world. In particular, no information of the sulfur isotope of the major rivers in Asian conti-

Source of ore-forming materials in Laowangzhai gold deposit, Yunnan. Evidence from lead isotopic composition

THE Laowangzhai superlarge gold deposit was found in 1984. Although studies on regional structure, geology of deposits and lamprophyres, which are temporally and spatially related to gold mineralization,have been carried out, the views on the source of ore-forming materials have been different. Thisnote summarized the characteristics of lead isotopic composition of the deposits, and probed further intothe source of ore-forming materials. 1 Geological setting The Laowangzhai gold deposit, located in the north of the Ailaoshan fault zone, consists of Donggualin and Laowangzhai ore block. The strata in the orefield include Paleozoic （Pz3） epimetamorphic ma-

Sulphur and Lead Isotope Compositions of the Dajiangping Deposit in Western Guangdong Province

The Dajiangping pyrite deposit located in the middle sector of the Yunkai uplift in western Guangdong is a stratiform sulphide deposit occurring in Sinian marine clastic and fine clastic rocks. The formation of the deposit was related to submarine exhalation and hot brine deposition. A part of it was reformed by late-stage hydrothermal solution. The δ34S values of pyrite vary from - 25.55‰ to +21.07‰, which are inversely proportional to the content of organic carbon in ore and pyrite. Passing from striped fine-grained pyrite ore to massive coarse-grained pyrite ore, i.e. from south to north, the sulphur isotopic composition changes from the light sulphur-enriched one to the heavy sulphur-enriched one. The lead isotopic composition of striped ore is consistent with that of the country rocks of orebodies and the lead is radiogenic lead derived from the upper crust. The lead isotopic composition of massive ore is relatively homogeneous and its 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios are a bit lower than those of striped ore;the lead result from mixing of synsedimentary ore lead with that derived from basement migmatlte brought by late-stage hydrothermal solutions.

The Relationship Between Mineralogical Characteristics and Isotopic Composition of Sphalerite,as Exemplified by the Huxu Deposit, China

The relationship between mineralogical characteristics and isotopic compo-sition of suffides has not received its proper share of attention from geologists, althoughmany references are available concerning the application of sulfur isotopes to geologicalproblems.Located in the vicinity of the contact region between the Yangtze Platform and theSouth China Caledonian Folding Zone, the Huxu deposit is hosted in a structural zone inquartz-diorite-porphyrite emplaced in Jurassic volcanic rocks. Sphalerite and galena arethe principal ore minerals in the deposit. (1) Sphalerite is highiy variable in color and thisvariation can be related to its chemical composition and sulfur isotopic characters. Darkcolored sphalerites are poor in Zn and Ni, rich in Pb, Cu, Fe, Ag and Au and have high δ34Svalues, while the opposite is true for light-colored ones. (2) δ34S of sphalerite is negativelycorrelated with the contents of Zn and Ni and positively correlated with the contents of Pb,Cu, Ag and Au, with the absolute values of the correlation coefficients being greater than0.7. The above two characters suggest that the suthe isotopic composition of sphalerite iscontrolled not only by the physicochemical conditions under which the mineral was formed,but also by mineralogical characteristics of the host mineral. (3) Apparent correlationsexist among the constituent elements in the sphalerite. For example, Zn is negativelycorrelated with Cu, Pb, Fe, Ag and Au and positively correlated with Ni. (4) Sphaleritesof the same color in the same hand specimen always show similar characters with respect totrace element and sulfur isotopes. (5) Two distinct trends of evolution can be recognizedbetween Zn and Cu, Zn and Pb, Zn and Ag and between these elements on one handand δ34S on the other, reflecting that the ore-forming solutions may have resulted frommixing of fluids of different origins. (6) Pb is uniformly distributed in sphalerite and showspositive correlations with Cu, Fe, Ag and δ34S, suggesting isomorphic substitution in thesphalerite lattice.

沉积岩中黄铁矿含量及其硫同位素组成连续测定方法研究

沉积岩中黄铁矿的含量和硫同位素组成研究可以用于判断沉积环境特征,反演成岩成矿过程。设计了一套多通道的黄铁矿硫提取装置,确定了装置的加热温度为130℃,实验时间为2h,优化了实验流程,实现一次提取同时满足黄铁矿含量及其同位素组成测定需要。采用亚甲基蓝分光光度法测定硫含量和元素分析仪-气体同位素质谱法测定黄铁矿硫同位素组成。亚甲基蓝分光光度法的标准曲线的线性相关性R^(2)=0.9999,黄铁矿样品的加标回收率介于94%~100%之间,10次测量的相对标准偏差为1.9%。黄铁矿经过铬还原法提取生成的硫化银的硫同位素组成的测试结果和本身的测试结果在误差范围内一致,精度≤0.2‰,可以满足沉积岩中黄铁矿硫同位素测试需求。

北山成矿带老硐沟金多金属矿床S-Pb-C-O同位素特征及其对矿床成因的约束

老硐沟金多金属矿床是北山成矿带内蒙古段最为典型的金矿床之一,其矿床成因存在较多争议,矿床成矿物质来源方面的研究几近空白。文章基于详细的野外实地调查,选取不同成矿阶段的硫化物和方解石,开展原位S-Pb同位素和C-O同位素测试。研究结果表明,老硐沟金多金属矿床δ34S值为-0.56‰~5.54‰,^(206)Pb/^(204)Pb比值为18.326~18.390,207Pb/^(204)Pb比值为15.563~15.645,^(208)Pb/^(204)Pb比值为38.226~38.390,铅同位素μ值变化范围为9.40~9.55,ω值变化范围为35.77~36.85,方铅矿二阶段模式年龄为232~270 Ma,δ^(13)C值介于-0.04‰~2.93‰之间,表明老硐沟金多金属矿床成矿物质具有岩浆和地层混合来源性质,成矿流体以岩浆来源为主,成矿作用晚期流体中混入了地层变质水。文章从矿床稳定同位素研究方面,结合前人对北山造山带构造演化的认识,提出老硐沟金多金属矿床成因为岩浆热液型。

甘肃毕家山铅锌矿床中镉的赋存状态及矿床成因:来自硫化物LA−ICP−MS微量元素和原位硫同位素的证据

甘肃毕家山铅锌矿床是西秦岭造山带西成矿田发现的首个铅锌矿床,累计探明铅锌资源量120×10^(4)t,Pb和Zn的品位分别为1.86%和5.42%。矿床中发育2类矿体,分别是赋存于灰岩中的灰岩型和赋存于千枚岩中的千枚岩型。2类矿体的矿石矿物组合均为闪锌矿+方铅矿±黄铁矿±黄铜矿。毕家山铅锌矿床镉的赋存状态尚不明确。通过激光剥蚀电感耦合等离子质谱仪(LA-ICP-MS)分别对灰岩型和千枚岩型矿石中的硫化物(闪锌矿、方铅矿、黄铁矿和黄铜矿)进行了微量元素及原位S同位素分析。研究结果显示,灰岩型和千枚岩型矿石中闪锌矿的Cd平均含量分别为2076×10^(-6)和1695×10^(-6),高于矿产工业一般标准(1000×10^(-6)),而方铅矿、黄铁矿和黄铜矿中的Ga、Ge、Se、In、Tl含量均低于矿产工业一般标准(100×10^(-6))。结合岩相学和LA-ICP-MS分析发现,毕家山铅锌矿床无Cd的独立矿物和以吸附形式存在的Cd,Cd主要以Cd^(2+)↔Zn^(2+)类质同象形式赋存于闪锌矿中,其次为Cd^(2+)+Fe^(2+)↔2Zn^(2+)。通过闪锌矿微量元素温度计获得灰岩型和千枚岩型矿石中闪锌矿的形成温度分别为198~254℃(平均值为227℃)和203~245℃(平均值为230℃),与前人通过流体包裹体和矿物对温度计的研究结果一致,表明其成矿温度为中温。此外,原位硫同位素分析结果显示,该矿床中灰岩型和千枚岩型矿石的δ34S平均值分别为+13.64‰和+17.72‰,表明硫来源于海相硫酸盐。综合闪锌矿微量元素数据、同位素地球化学、成矿温度、岩相古地理和矿床地质特征对比分析,推测毕家山铅锌矿床的成因类型属于SEDEX型。

Source Identification of Sulfur in Uncultivated Surface Soils from Four Chinese Provinces

The analysis of stable isotopes of sulfur(δ34S) is a useful tool for identifying sources of sulfur in soils. Concentrations and sulfur(S)isotopes of water-soluble sulfate(WSS), adsorbed sulfate(AS), residual sulfur(RS), and total sulfur(TS) in uncultivated surface soils of four Chinese provinces were systematically analyzed for identifying sources of S in the soils. Green and healthy mosses(Haplocladium microphyllum) were sampled as bioindicators. The mean WSS concentration(27.8 ± 23.4 mg kg-1) in the surface soils was lower than those of AS(101.4 ± 57.0 mg kg-1) and RS(381.5 ± 256.7 mg kg-1). The mean δ34S values of WSS and AS were very similar(about2.0‰), lower than those of RS(8.0‰) and TS(6.1‰). A significant linear correlation was found between the δ34S values of AS and WWS(y = 1.0002x- 0.0557, P < 0.0001), indicating that sulfate adsorption in the soils did not markedly fractionate S. All S species in the soils of Guizhou Province were characterized by the lowest δ34S values, consistent with the most34S-depleted rainwater sulfate reported at Guiyang of Guizhou Province. The δ34S values of sulfate in mosses and rainwater previously reported were significantly linearly correlated with those of both WWS and AS in surface soils, suggesting that atmospheric S input was an important source for soil WSS and AS. However, there were no significant correlations between isotopic composition of rainwater sulfate and RS or TS.The slopes of all these significant linear correlations(soil/rainwater or soil/moss isotopic ratio) were 0.4–0.6, indicating that inorganic sulfate in the surface soils should be a result of mixing of deposited atmospheric sulfate with a more34S-depleted sulfate component possibly from mineralization of RS.

Genesis of the Sinongduo Carbonate-hosted Pb-Zn-Ag Deposit in the Central Lhasa Terrane,Tibet

The Sinongduo mining region includes two types of mineralizations:the epithermal and the carbonate-hosted PbZn-Ag deposits.Despite being studied for many years,the ore formation process and genesis of the carbonate-hosted Pb-Zn-Ag deposits remain poorly understood.The Pb-Zn-Ag ore bodies occur as veins and are hosted by limestone and dolostone of the Permian Xiala Formation.Three sulfide mineralization substages have been identified at the Sinongduo carbonatehosted deposit.Indium coupled with Cu,Co and Sn was incorporated into sphalerite as substitutions:2Zn^(2+)?Cu^(+)+In^(3+),(3n/2+1)Zn^(2+)?Co^(2+)+n In^(3+)or(2n+1)Zn^(2+)?Co^(2+)+n(Cu^(+)+In^(3+))(n>1)and 4Zn^(2+)?Sn2++2In^(3+).Sphalerite and pyrite in the mineralization stage displayδ^(34)S values in a narrow range of+5.7‰to+11.3‰,which are similar to those of Palaeocene igneous rocks,indicative of a magmatic source of sulfur.We present systematic carbon-hydrogen-oxygen isotope results that further support a magmatic source for the ore-forming fluids that were influenced by meteoric water.Furthermore,the Pb isotope compositions of sulfide minerals in the Sinongduo carbonate-hosted deposit overlap with the values of coeval Linzizong volcanic rocks and are similar to those of Indian Ocean sediments,indicating upper crustal sources of metals.We conclude that the Sinongduo carbonate-hosted Pb-Zn-Ag deposit is a medium-to low-temperature magmatic-hydrothermal deposit related to Linzizong magmatism.

冲绳海槽唐印热液区中硬石膏的化学及其硫同位素组成

硬石膏是最早构成热液烟囱体壁的矿物之一,其对于了解流体-海水混合以及海底热液系统中元素的迁移与循环具有重要的意义。为此,对西太平洋冲绳海槽唐印热液区中的硬石膏,进行了微区原位元素以及硫同位素组成分析。根据硬石膏的结晶形态,可以将硬石膏分为两种类型:较早形成的I型硬石膏,其呈半自形或他形晶,似针状、放射状及不规则晶的集合体产出;较晚形成的II型硬石膏,其呈自形晶,以板状及粒状晶的集合体产出。当热液流体初次遇到海水时,将快速沉淀形成I型硬石膏,并构成了热液烟囱体的壁。随后,II型硬石膏经历了一个相对充分的生长阶段。同时,硬石膏中的Ba、Al、Sr、Ni、Fe、Mn和Cr含量明显高于海水,表明产生硬石膏沉淀的热液流体来自于海底面以下,是经历了流体-岩石和/或沉积物相互作用的流体。硬石膏的Mg含量明显分别低于海水和高于喷口流体,表明其是流体-海水混合的结果。I型硬石膏,其Sr含量明显低于II型硬石膏,表明在形成自形、板片状或粒状硬石膏的期间,来自热液流体的Sr,主要进入II型硬石膏中。硬石膏的Fe、As、Sr、Ba和Pb含量,明显高于冲绳海槽喷口流体的,则表明这些来自流体中的元素更容易随着硬石膏的沉淀而进入硬石膏中,并导致硬石膏富集该类元素。硬石膏的稀土元素组成及其配分模式,具正Ce和负Eu异常的特征,其是流体在海底面以下从火山岩和/或沉积物中淋滤出来,并经历了流体-海水混合作用的结果。此外,在流体-海水混合期间,硬石膏中的硫主要来自海水。