Lead isotopic systematics for native copperchalcocite mineralization in basaltic lavas of the Emeishan large igneous province, SW China： Implications for the source of copper

The Emeishan continental flood basalt, which is widespread in Yunnan, Guizhou and Sichuan provinces of Southwest China, is the volcanic product of a Permian mantle plume, and native copper-chalcocite mineralization associated with the basalt is very common in the border area of Yunnan and Guizhou provinces. The mineralization occurred in the tuff intercalation and terrestrial sedimentary rock intercalation which were formed during the main period of basalt eruption. The orebodies are controlled by the stratigraphic position and faults. Metal ore minerals in the ores are mainly native copper, chalcocite and tenorite, with small amounts of chalcopyrite, bomite, pyrite and malachite, and sometimes with large amounts of bitumen, carbon and plant debris. Several decades of ore deposits are distributed in the neighboring areas of the two provinces, while most of them are small-scale deposits or only ore occurrences. By comparing the lead isotopic composition of the ores with that of the wall-rocks, cover and basement rocks of various periods, the source of copper in this type of ore deposits was studied in this paper. The results showed that: (1) The Pb isotopic composition of the ores from ten deposits is absolutely different from that of sili-ceous-argillaceus rocks of the Upper Permian Xuanwei Formation, limestones of the Lower Permian Series and Carboniferous, Cambrian sandstone-shale and recta-sedimentary rock and dolomite from the upper part of the Meso-Proterozoic Kunyang Group, This indicates that ore lead was derived neither from the cover rock nor from the basement rocks; (2) Although the Neo-Proterozoic Siman dolomite and silicalite, and dolomite in the lower part of the Kunyang Group are similar in Pb isotopic composition to the ores, lead and copper contents in these rocks are very low and they have not made great contributions to copper mineralization; (3) The ores have the same Pb iso-topic composition as the basalt, the latter being enriched in copper. These facts indicate that lead and copper were derived from the basalt. According to the regional geological data and the geological-geochemical characteristics of the ore deposits, it is suggested that ore-forming materials were leached out from the basalt. The thickness and buried depth of the basalt and regional tectonic dynamics can affect the formation of large-scale copper deposits. Therefore, exploration for this type of ore deposits should be conducted in the areas from western Yunnan to western Sichuan, where there are developed basalts of great thickness, with extensive tectonic movement and magmatic activity.     

浙江省诸暨至龙泉一带金矿床的铅同位素地球化学研究

本文研究了浙江省诸暨至龙泉一带金矿床的铅同位素地球化学特征。通过研究铅同位素组成、源区特征值和模式年龄,对该区金矿床得出以下两点认识:1.该区金矿床铅同位素组成在区域上具有一定的变化趋势,并可分为二大类,即正常铅和弱放射性成因异常铅,它们反映了一定的物源特征;2.该区金矿床的区域成矿时代为400—700Ma,结合区域成矿地质特征,可以证明该区金矿床主要为变质热液矿床。     

云南兰坪盆地西缘脉状铜多金属矿床硫、铅同位素组成及成矿示踪

云南兰坪盆地西缘脉状铜多金属矿床主要赋存于由砂岩、粉砂岩和页岩组成的碎屑岩建造中.为了查明兰坪盆地西缘脉状铜多金属矿床成矿物质来源,对盆地西缘四个典型脉状铜多金属矿床(科登涧、连城、金满和水泄)的硫、铅同位素的组成进行了分析和对比研究.结果表明,这些矿床的铅同位素组成总体变化较小,且大部分落在盆地沉积地层铅范围内,金满、连城铜矿床可能有部分深源铅的加入.硫同位素特征表明,兰坪盆地西缘脉状铜多金属矿床的硫主要来源于地层硫酸盐的还原作用,其中金满铜矿床和连城铜钼多金属矿床可能有深源硫的混入.各矿床硫同位素不同的特点,除反映各矿床源区硫同位素组成的差异外,可能还与各矿床成矿时不同的物理化学条件(温度、氧逸度、pH 值和离子强度等)差异有关     

Pb isotope fingerprinting of mesothermal gold deposits from central Victoria, Australia: implications for ore genesis

New Pb isotope data from three major mesothermal lode gold deposits (Ballarat West, Tarnagulla, Maldon) in central Victoria support a model whereby the metals derived from a large reservoir with a long residence time in the crust below the Palaeozoic Lachlan Fold Belt. The Pb isotopic ratios of least radiogenic samples from these deposits are in close agreement with published Pb signatures for turbidite-hosted gold deposits, and for Devonian granites, elsewhere in the Lachlan Fold Belt. Despite their spatial distribution and variations in the geological setting, the Pb signatures point to the extraction and transport of metals from a crustal source area by long-lasting, large-scale hydrothermal systems, resulting in the prominent homogenisation of Pb isotopic ratios. The enduring interaction between large hydrothermal systems and an extensive crustal source reservoir were a vital pre-requisite in the formation of the Victorian gold province. In this regard, the prospectivity of Victoria is analogous to world-class ore provinces elsewhere, such as the Archaean Yilgarn Block in Western Australia. Received: 10 February 1998 / Accepted: 28 April 1998     

The potential source of lead in the Permian Kupferschiefer bed of Europe and some selected Paleozoic mineral deposits in the Federal Republic of Germany

New lead isotopic compositions have been measured for Paleozoic bedded and vein ore deposits of Europe by the high precision thermal emission (triple filament) technique. Eleven samples have been analyzed from the Upper Permian Kupferschiefer bed with representatives from Poland to England, three samples from the Middle Devonian Rammelsberg deposit and one from the Middle Devonian Meggen deposit, both of which are conformable ore lenses and are in the Federal Republic of Germany (FRG); and also two vein deposits from the FRG were analyzed, from Ramsbeck in Devonian host rocks and from Grund in Carboniferous host rocks. For Kupferschiefer bed samples from Germany, the mineralization is of variable lead isotopic composition and appears to have been derived about 250 m.y. ago from 1700 m.y. old sources, or detritus of this age, in Paleozoic sedimentary rocks. Samples from England, Holland, and Poland have different isotopic characteristics from the German samples, indicative of significantly different source material (perhaps older). The isotopic variability of the samples from the Kupferschiefer bed in Germany probably favors the lead containing waters coming from shoreward (where poor mixing is to be expected) rather than basinward (where better mixing is likely) directions. The data thus support the interpretation of the metal source already given by Wedepohl in 1964. Data on samples from Rammelsberg and Meggen tend to be slightly less radiogenic than for the Kupferschiefer, about the amount expected if the leads were all derived from the same source material but 100 to 150 m.y. apart in time. The vein galena from Ramsbeck is similar to that from Rammelsberg conformable ore lenses, both in rocks of Devonian age; vein galena from Grund in Upper Carboniferous country rocks is similar to some bedded Kupferschiefer mineralization in Permian rocks, as if the lead composition was formed at about the same time and from similar source material as the bedded deposits. Although heat has played a more significant role in the formation of some of these deposits (veins and Rammelsberg-Meggen) than in others (Kupferschiefer), there is no indication of radically different sources for the lead, all apparently coming from sedimentary source material containing Precambrian detritus. One feldspar lead sample from the Brocken-Oker Granite is not the same in isotopic composition as any of the ores analyzed.Publication authorized by the Director, U.S. Geological Survey     

浙赣若干火山岩型铀矿床成矿模式及找矿勘探方向

本系统介绍了浙赣各类火山岩型铀矿床的地质特征，分析了各类火山岩型铀矿床的同位素组成、成矿物质来源以及成矿的物理化学条件，提出以次火山岩体为先导，热液柱(体)为主导所控制的地下水-火山岩成矿体系，是该区火山岩型铀矿成矿的主要模式，并以此对浙赣火山岩地区寻找火山岩型铀矿床提出勘探建议。     

海南抱板金矿铅同位素化探评价

通过对海南抱板金矿几个切穿矿脉剖面的矿石和围岩的铅同位素组成分析。发现铅同位素组成与矿的产出具有相关关系。铅同位素的异常可能反映了成矿物质来源深度的差异，据此可进行铅同位素化探评价，提出了“正异常以深部找矿为主。负异常注意扩大横向找矿”的原则，土外山地区是地表的浅层金矿化，而二甲，北牛为深源金矿化，在土外山地区深部应可能找到对应于二甲，北牛的深源金矿化层。     

新疆北部主要金矿床的成矿地球化学特征

主要依据成矿作用方式,基本成矿特点及关键控矿标志等,将新疆北部的主要原生金矿新划分为７个矿床类型,分别是浅成低温热液型金矿、韧性剪切带蚀变岩型金矿、微细粒浸染型金矿、浅成岩－构造蚀变岩型金矿、变质热液型金矿、石英脉型金矿及铜、金伴生型矿床。通过分析比较各矿床类型典型金矿的ＲＥＥ分布型式、其矿石的微量元素含量与分布型式、硫与铅同位素组成及流体包裹体成分等资料,探讨了其成矿地球化学特征。     

简论中国层控铜铅锌矿床的稳定同位素地球化学特征

摘要：层控矿床是构造运动、岩浆活动和沉积作用的综合产物,按其大地构造环境和沉积建造可划分为４大类、１３个亚类。层控矿床的稳定同位素组成按这一分类呈明显的规律性。不同建造中硫化物的硫同位素组成与其来源有关,并随后期叠加改造作用的增强而趋于均一。铅同位素组成反映了时代由老变新,由正常铅－混合铅－异常铅的演化规律,μ值也有增大的趋势,由幔源铅逐渐向壳幔混合型过渡。其含矿流体氢、氧同位素组成为建造水,显示了岩浆水与大气降水的混合,在不同建造类型中存在着较大差异,并随后期叠加改造作用的增强向混合含矿流体方向演化。总之,层控矿床的稳定同位素组成,其背景值反映了原始沉积环境,并明显地受沉积建造类型控制,后期叠加改造作用也可造成同位素组成的不同程度的变化。     

Recent geological advances concerning the H.Y.C. and associated deposits,McArthur river,N.Y.

Recent mineral exploration in the McArthur River District, Northern Territory, has found new areas of base‐metal mineralization and has resulted in a reinterpretation of the geological setting of the previously discovered mineral deposits. The geology along the eastern margin of the H.Y.C. sub‐basin has been revised. The Cooley Dolomite Member of the Barney Creek Formation is interpreted as a talus‐slope breccia lying adjacent to a syndepositionally uplifted fault block (Western Fault Block) of lower McArthur Group sediments. The Western Fault Block was the source of the majority of the fragments in breccia horizons in the H.Y.C. sub‐basin and its uplift played an important role in the development of the sub‐basin. Within the Western Fault Block, the sequence hosting the Cooley II copper mineralization is the Mara Dolomite Member of the Emmerugga Dolomite, and not the Cooley Dolomite Member of the Barney Creek Formation as previously thought. New mineral discoveries include the substantial extension of the Coxco deposit, a coarse‐grained zinc‐lead stratabound deposit showing affinities with the Mississippi Valley‐type deposits; and an area of stratiform fine‐grained zinc‐lead mineralization in the Emu Plains sub‐basin of the Bulburra Depression.     

华南陆块铜的地球化学块体与成矿省的关系

在区域化探全国扫面计划1∶20万水系沉积物样品Cu含量的基础上,描述了华南陆块铜地球化学块体的空间分布特征,并分析了它们与地质体、已知的铜成矿省(矿集区)在空间上的对应关系。发现华南陆块的铜地球化学块体主要分布于扬子地块西南缘,长江中下游、西秦岭、三江地区和湘粤桂交界区。其中扬子地块西南缘铜地球化学块体主要与峨眉山玄武岩的铜高背景值有关,其他异常与海西期镁铁质超镁铁质岩有关的铜矿和层控型铜矿有关;长江中下游地球化学块体与长江中下游成矿带吻合;西秦岭铜地球化学块体与岩体、铜矿和以铜为伴生元素的矿床有关;三江、湘粤桂交界区的铜地球化学块体也有与之对应的铜矿床或铜为伴生元素的矿床。通过这些地球化学块体与已知的地质体、成矿省(矿集区)的对比得出如下结论,铜地球化学块体的形成可能与岩石的高背景值、铜成矿省(矿集区)或铜为伴生元素的矿床有关。巨量的成矿物质的供应只是形成大型、超大型矿床的必要条件,如长江中下游铜地球化学块体为铜成矿省提供物质来源;但每个地球化学块体并不一定都有与之对应的矿集区,如峨眉山玄武岩铜地球化学块体与玄武岩高背景值有关,并没有形成大型的铜矿床。     

佛子冲火山岩区隐伏铜锌矿床的类型归属及成矿远景

佛子冲铅锌成矿带包括两种矿床类型,即佛子冲式夕卡岩型矿床和牛卫式热液充填（交代）型矿床,这两类矿床矿体产状,围岩蚀变,矿物组合,以及单矿物中微量元素分布特征等方面区别明显,但硫化矿物的硫,铅同位素组成相同,并且均表现出强烈的均一化的特点,反映出两者的成矿条件及成矿方式虽然不同,但具有相同的物源－燕山期钙碱性火山岩系,在佛子冲矿带南部火山岩覆盖区,铅锌矿化组合空间展布呈“三层楼”结构,并且构造控矿作用明显：矿点主要分布于佛子冲隐伏背斜的轴部（“龙脊”）,特别是在隐伏背斜被NE向断裂切割部位,火山岩铅锌矿化大多属于佛子冲式矿床类型,即佛子冲矿带内主要的矿床类型,具有较大的找矿前景。     

Application of Lead Isotopes to Geochemical Exploration of Gold Deposits in Baoban , Hainan Province, China

Lead isotopes have been widely applied in geochemical exploration and evaluation of ore deposits, as well as in ascertaining the age of mineralization and the source of ore fluids.Long-term practice showed that the method of lead isotope targeting is somewhat efficient for macroscopic evaluation of forecasting areas, but not powerful enough for for ecasting concealed orebodies. As the contents of U and the variation of U/Pb ratio sharply decrease with depth in the lithosphere, U-Th-Pb isotopic differentiation must have occurred during the crust-mantle e-volution. Lead isotopic ratios show a wide variation range, varying in the front of mineralizationand shallow-derived ores, but maintaining very stable in the major orebody and being usuallyclose to the average isotopic composition of the crust and mantle of the continent block fromwhich the ores were derived. Therefore, the lead isotopic composition can serve as a measure for identifying the position of mineralization. The lead isotope geochemistry was applied to the ex-ploration and evaluation of the Baoban gold deposits of Hainan Province, China. The an alyticalresults of ore veins and adjacent rocks showed that there is a correlation between the lead isotopedata and the position of orebody. Based on the experience from the Baoban gold deposits and other ore deposits in Yunnan Province, an exploration principle has been established, that is,positive anomalies of lead isotope eigenvectors for prospecting deep-seated orebodies and nega-tive anomalies of eigenvectors for enlarging lateral exploration surrounding the known deposit.The ore beds in the Erjia and Beiniu mining districts should be as signed to the deep part of the orebody and those in the Tuwaishan mining district should be the shallow part, so ore beds cor-responding to those in the Erjia and Beiniu mining districts may be found in the Tuwaishan min-ing district.     

Magmatism, Deep Processes and Gold Deposits in Eastern Hebei, China

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保山镇康地块矽卡岩型铅锌矿床成因初探

保山镇康地块是"三江"南段重要的铅锌多金属成矿区之一,地质构造复杂,铅锌成矿地质条件优越,其中核桃坪与芦子园是近年发现的两个大型铅锌矿床,矿床受近NE向断裂、背斜轴部和地层控制明显,上寒武统核桃坪组与沙河床组大理岩化灰岩为主要赋矿地层,近矿围岩矽卡岩化强烈,流体包裹体,Pb、S、H、O同位素和微量元素等地球化学对比研究表明:核桃坪和芦子园铅锌矿床均经历了中温、高温两个矿化阶段;核桃坪铅锌矿床矿石铅同位素较芦子园铅锌矿床有较高的比值和较大的变化范围,均以高μ值为特征,属于放射性成因铅,暗示其成矿物质以壳源铅为主;硫化物硫同位素均多为较低正值并呈塔式分布,具有岩浆硫特征,两者均无生物硫酸盐热化学还原作用的参与,其中硫同位素分馏已达平衡;与硫化物共生的石英δDH2O(-109‰~-91‰)和δ18OH2O(-4.3‰~2.3‰)同位素研究表明核桃坪矿床成矿流体主要来自深部岩浆水,并遭受后期大气降水或地层水的混合;核桃坪矿床与芦子园矿床的微量元素具有岩浆热液型矿床特征,不同于VMS型、MVT型铅锌矿床。因此,笔者认为两个矿床应属于与深部隐伏岩体有关的中-高温矽卡岩型铅锌矿床,矿区深部隐伏岩体的侵入产生岩浆热液并携带Pb、Zn等成矿物质与地层水或大气降水混合,在背斜轴部与NE向断裂的交汇处形成该类型矿床。     

Gold mineralization in China: Metallogenic provinces,deposit types and tectonic framework

We present a review of major gold mineralization events in China and a summary of metallogenic provinces, deposit types, metallogenic epochs and tectonic settings. Over 200 investigated gold deposits are grouped into 16 Au-metallogenic provinces within five tectonic units such as the Central Asian orogenic belt comprising provinces of Northeast China and Tianshan-Altay; North China Craton comprising the northern margin, Jiaodong, and Xiaoqinling; the Qinling-Qilian-Kunlun orogenic belt consisting of the West Qingling, North Qilian, and East Kunlun; the Tibet and Sanjiang orogenic belts consisting of Lhasa, Garzê-Litang, Ailaoshan, and Daduhe-Jinpingshan; and the South China block comprising Youjiang basin, Jiangnan orogenic belt, Middle and Lower Yangtze River, and SE coast. The gold deposits are classified as orogenic, Jiaodong-, porphyry–skarn, Carlin-like, and epithermal-types, among which the first three types are dominant.The orogenic gold deposits formed in various tectonic settings related to oceanic subduction and subsequent crustal extension in the Qinling-Qilian-Kunlun, Tianshan-Altay, northern margin of North China Craton, and Xiaoqinling, and related to the Eocene–Miocene continental collision in the Tibet and Sanjiang orogenic belts. The tectonic periods such as from slab subduction to block amalgamation, from continental soft to hard collision, from intracontinental compression to shearing or extension, are important for the formation of the orogenic gold deposits. The orogenic gold deposits are the products of metamorphic fluids released during regional metamorphism associated with oceanic subduction or continental collision, or related to magma emplacement and associated hydrothermal activity during lithospheric extension after ocean closure. The Jiaodong-type, clustered around Jiaodong, Xiaoqinling, and the northern margin of the North China Craton, is characterized by the involvement of mantle-derived fluids and a temporal link to the remote subduction of the Pacific oceanic plate concomitant with the episodic destruction of North China Craton. The Carlin-like gold metallogenesis is related to the activity of connate fluid, metamorphic fluid, and meteoric water in different degrees in the Youjiang basin and West Qinling; the former Au province is temporally related to the remote subduction of the Tethyan oceanic plate and the later formed in a syn-collision setting. Porphyry–skarn Au deposits are distributed in the Tianshan-Altay, the Middle and Lower Yangtze River region, and Tibet and Sanjiang orogenic belts in both subduction and continental collision settings. The magma for the porphyry–skarn Au deposits commonly formed by melting of a thickened juvenile crust. The epithermal Au deposits, dominated by the low-sulfidation type, plus a few high-sulfidation ones, were produced during the Carboniferous oceaic plate subduction in Tianshan-Altay, during Early Cretaceous and Quaternary oceanic plate subduction in SEt coast of South China Block, and during the Pliocene continental collision in Tibet. The available data of different isotopic systems, especially fluid D–O isotopes and carbonate C–O systems, reveal that the isotopic compositions are largely overlapping for different genetic types and different for the same genetic type in different Au belts. The isotopic compositions are thus not good indicators of various genetic types of gold deposit, perhaps due to overprinting of post-ore alteration or the complex evolution of the fluids.Although gold metallogeny in China was initiated in Cambrian and lasted until Cenozoic, it is mainly concentrated in four main periods. The first is Carboniferous when the Central Asian orogenic belt formed by welding of micro-continental blocks and arcs in Tianshan-Altay, generating a series of porphyry–epithermal–orogenic deposits. The second period is from Triassic to Early Jurassic when the current tectonic mainframe of China started to take shape. In central and southern China, the North China Craton, South China Block and Simao block were amalgamated after the closure of Paleo-Tethys Ocean in Triassic, forming orogenic and Carlin-like gold deposits. The third period is Early Cretaceous when the subduction of the Pacific oceanic plate to the east and that of Neo-Tethyan oceanic plate to the west were taking place. The subduction in eastern China produced the Jiaodong-type deposits in the North China Craton, the skarn-type deposits in the northern margin (Middle to lower reaches of Yangtze River) and the epithermal-type deposits in the southeastern margin in the South China Block. The subduction in western China produced the Carlin-like gold deposits in the Youjiang basin and orogenic ones in the Garzê-Litang orogenic belt. The Cenozoic is the last major phase, during which southwestern China experienced continental collision, generating orogenic and porphyry–skarn gold deposits in the Tibetan and Sanjiang orogenic belts. Due to the spatial overlap of the second and third periods in a single gold province, the Xiaoqinling, West Qinling, and northern margin of the North China Craton have two or more episodes of gold metallogeny.     

滇中铅锌矿床地球化学与成因研究

滇中地层铅锌丰度高,成矿元素对于地层有继承性和一致性;硫同位素分散,富重硫;铅同位素稳定,多为单阶段演化正常铅,模式年龄与地层时代大体一致,矿质来自地层,矿床为层控型。同生沉积形成矿源层,后期改造(叠加)形成矿体。为中低温度的地下水热液成矿。     

辽宁青城子铅锌矿成矿流体特征和成矿物质来源示踪

青城子铅锌矿地处辽东-吉南裂谷带西端,是中国东北地区著名的铅锌矿床,其成矿作用复杂。为了深入揭示该矿床的成矿流体特征和成矿物质来源,本文在对青城子铅锌矿床(喜鹊沟、甸南、本山)地质特征研究的基础上,开展了流体包裹体测温和激光拉曼成分分析,H、O、C、S、Pb同位素分析,并进行了多元同位素体系的综合示踪。青城子铅锌矿床发育富液相包裹体,局部发育H_2O-CO_2三相包裹体。成矿温度范围大,是多阶段成矿作用发展演化的反映(至少两期成矿),成矿温度主要在190℃~310℃之间,应属中温成矿,成矿流体为中温低盐度的水盐流体。激光拉曼成分特征,成矿流体总体属于含CH_4的H_2O-CO_2-NaCl体系,属于还原性流体,具有深源的特征。氢氧同位素结果显示,成矿热液主要来源于岩浆水和大气降水。硫同位素特征表明,矿体中的硫可能主要来自海水硫酸盐的还原。碳氧同位素特征表明,成矿物质可能起源于地层,后期发生岩浆热液改造。铅同位素结果表明,矿石中铅是地层与岩浆岩的混合源铅。     

巴西巴伊亚圣弗朗西斯科克拉通北部地质构造背景、矿床类型及其成矿作用

通过建立描述成矿作用特征的构造和时间框架,探讨圣弗朗西斯科克拉通北部矿床的成因。许多太古宙的矿化作用发生在克拉通形成以前。铬铁矿、镍、金和祖母绿矿床是古元古代造山旋回形成的,那时克拉通合并到大西洋古陆。在中—新元古代,即罗迪尼亚(Rodinia)超级大陆的裂解期间,有拉张事件发生,其与磷矿和铀矿有关。金伯利岩金刚石矿化和金矿化是巴西利亚(Brasiliano)造山旋回形成的,其与西冈瓦纳大陆拼合同期。在寒武纪,该区存在长期和均一的地应力记录。同位素和磁性系统的重置,影响了在520Ma时候的依列斯(Irecê)盆地的新元古代沉积作用。这种重置归因于巴西利亚造山旋回结束时区域尺度流体的迁移和矿化作用。