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.

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.

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.

Distribution and existing state of indium in the Gejiu Tin polymetallic deposit, Yunnan Province, SW China

The Gejiu tin polymetallic deposit, located in the southwest margin of the South China Belt bordering on the Yangtze Block, is hosted in Triassic carbonates. This study shows that there is an indium enrichment in the ores.Indium mainly exists in sphalerite-rich massive sulfide ores with a concentration of 198.3–1570 ppm; the indium concentration in sphalerite ranges from 493.3 up to4781 ppm. The inferred indium reserve in the Gejiu Sn deposit is over 4000 t, indicating that the Gejiu tin deposit is a giant In-bearing Sn-polymetallic deposit, similar to the Dachang and Dulong in southwest China. Sphalerite with a high Fe value(8.05–13.27 wt%) is the predominant indium carrier mineral; meanwhile chalcopyrite plays the secondary indium carrier role. EPMA mapping result shows that indium is likely distributed homogeneously and presented as a substitution for Zn in sphalerite.

Helium, lead and sulfur isotope geochemistry of the Gejiu Sn-polymetallic ore deposit and the s ources of ore-forming materials

Studies on the helium, lead and sulfur isotopic composition were performed of the Gejiu super-large Sn-polymetallic ore deposit. The results indicated that the ore-forming materials came from different sources and the deposit is a product of superimposed mineralization. The deposit is characterized by multi-source and multi-period mineralization, which experienced submarine hydrothermal deposition and Late Yanshanian magmatic hydrothermal mineralization. It is held that the Gejiu super-large Sn-polymetallic ore deposit is a multi-genesis deposit.

A Metallogenic Model of Tecto-Geochemistry on Tin-Polymetal Deposit in Malage Orefield of Gejiu Mining Area

By means of multivariance analysis and finite element on the basis of the analysis of generation andevolution of structural systems and structural system of syn-metallogenesis in the orefield,the authorsmade a research into the interrelation between tecto-geochemistry and structural stress field,revealedthe mechanism of metallogenesis by magma and ore-forming fluids driven under dynamic forces,andproposed a tecto-geochemistry model for the formation of the ore deposits,so as to suggest a basis oftheory for the prognoses of location and magnitude of hidden deposits.

The Dynamic Mechanisms for the Formation of Primary Metal Zoning of Cassiterite-Sulfide Deposits in the Gejiu Metallogenic Province, Yunnan

Copper and tin in cassiterite-sulfide deposits of the Gejiu metallogenic province are intimately associatedand show peculiar primary metal zoning. The authors made use of computer techniques to simulatenumerically the zoning of these ore deposits. The study shows that the regular spatial zoning probably resultedfrom the succession of multiple, intermittent and pulsatory mineralizations, The successive transports with di-verse velocities along channelways of the ore-forming solutions, taking place under conditions of definite dif-ference between metal concentrations, in solutions and wallrocks, followed by differential deposition, consti-tute possible dynamic mechanisms for the primary metal zoning.

The Characteristics of Migration of Ore Solutions in No.6 East Tin Deposit of the Songshujiao Orefield, Gejiu

No. 6 East tin deposit in the Songshujiao orefield, Gejiu, is characterized by one-stage hydrothermal activity and monotonous country rocks. The authors selected this deposit and used the multivariate statistical analysis to study the types of association of main ore-forming elements at different temperatures and pressures and their distribution in the deposit. On that basis combined with the structural analysis of the deposit, the recto-geochemical features of No.6 East tin deposit have been revealed and the direction and channel of migration of the ore solutions in faults and the deposit have been deduced. This research can appropriately elucidate the control of faults on the migration of ore solutions and the sites where ore solutions are dispersed and accumulated, thus providing the theoretical basis for the prediction of hydrothermal deposits in question.

云南个旧锡多金属矿集区电气石地球化学组成和硼同位素特征——对成矿流体性质和演化的约束

个旧锡矿集区发育与晚白垩世高分异花岗岩有关的世界级Sn-Cu多金属矿床,其成矿物质的来源及流体演化过程一直是研究的热点和难点。个旧地区电气石广泛发育于碳酸盐岩、花岗岩及矽卡岩中,但对电气石尚未进行系统研究,电气石与成矿之间的关系尚未明确。本文对不同类型电气石开展了系统的岩相学观察和电子探针(EPMA)、LA-ICP-MS微量元素和硼同位素分析。结果表明,所有电气石都属于碱性电气石,TurⅠ、TurⅡ、TurⅣ为热液成因,TurⅢ为岩浆成因。岩浆电气石相比于热液电气石具有更低的Mg、Ca等元素,TurⅠ电气石高含量的Sr表明受到了围岩的混染。电气石的微量元素变化表明,从似斑状花岗岩到等粒花岗岩,随着岩浆分异程度逐渐增加,Sn在岩浆中逐渐富集,在似斑状花岗岩和接触带矽卡岩中沉淀卸载。个旧不同类型电气石具有均一的δ11B值(−15.2‰~−12.8‰),与花岗岩的组成范围一致,表明成矿物质来源均来源于花岗质岩浆。

云南个旧卡房铜多金属矿床流体包裹体特征及其地质意义

卡房铜多金属矿床位于云南省个旧锡多金属矿集区,作为该区南段典型的铜多金属矿床,其深入的成矿流体性质及成矿物质来源研究尚为薄弱,限制了对该矿床成因的深入认识。本文对产于玄武岩中的似层状铜多金属矿体(主要成矿类型)开展了精细的野外岩相学、矿物学、C-H-O同位素及流体包裹体原位成分分析。结果显示,流体包裹体主要为气液两相水溶液包裹体,石英流体包裹体均一温度为264.5~330.5℃、盐度w(NaCleq)为16.24%~18.20%、密度为0.853~0.924 g/cm^(3);萤石流体包裹体均一温度为199.8~339.1℃、盐度w(NaCleq)为8.81%~18.88%、密度为0.822~0.955 g/cm^(3);方解石流体包裹体均一温度为112.1~199.4℃、盐度w(NaCleq)为4.96%~10.86%、密度为0.910~1.011 g/cm^(3),表明卡房铜多金属矿床成矿流体具有中低温、中低盐度、低密度特征,且早阶段到晚阶段,成矿温度和流体盐度明显降低。与Cu矿共生的石英δDV-SMOW值为–83.9‰~–78.9‰,δ18OH_(2)O值为4.63‰~12.14‰,方解石δ^(13)CV-PDB值为–7.11‰~0.64‰;同时,石英单个流体包裹体原位分析结果显示流体包裹体富集大离子亲石元素,如Na、K、Rb、Cs、Sr等。这些特征暗示了流体可能来源于与花岗质岩浆有关的热液流体,热液流体上升过程中与围岩碳酸盐岩发生强烈的水-岩反应;该过程可能萃取了玄武岩层中的Cu物质,诱发了Cu的富集并最终成矿。

云南个旧卡房矽卡岩型铜(锡)矿Re-Os年龄及其地质意义

云南个旧超大型锡多金属矿田是一个驰名中外的超大型锡多金属矿田,卡房是该矿田的一个重要的铜(锡)矿床。本文利用 Re-Os 同位素定年方法对卡房矽卡岩型矿体中5件辉钼矿样品进行了成矿时代测定,获得辉钼矿 Re-Os 同位素模式年龄为82.95±1.16Ma～83.54±1.31Ma,等时线年龄为83.4±2.1 Ma。该年龄和老卡岩体的 LA-ICP-MS 锆石 U-Pb 年龄85±0.85Ma 相吻合,表明成岩和成矿关系密切。辉钼矿 Re 含量显示成矿过程有地壳和地幔的共同参与。该 Re-Os 定年结果显示个旧卡房矽卡岩型铜(锡)矿床与云南都龙锡锌矿床、云南白牛厂银多金属矿床、广西大厂锡多金属矿床以及广西王社铜钨矿床的成矿年龄接近,表明这些矿床的形成受控于相同的地球动力学背景,同为华南中生代晚期大规模成矿作用的产物。

个旧西凹铜-锡多金属矿床花岗岩蚀变带稀土元素特征及意义

通过分析西凹铜-锡多金属矿床蚀变岩的稀土元素特征,研究该矿的成矿物质、成矿流体来源及成矿环境等。研究结果表明:蚀变花岗岩的稀土元素配分模式与未蚀变花岗岩类似,但也存在一定的差异。相对于未蚀变花岗岩,钾化花岗岩稀土总量增高,重稀土元素(HREE)的富集程度比轻稀土元素(LREE)的大,轻稀土元素中的La,Ce的富集程度比Pr和Nd的大,次生钾长石继承了蚀变流体的稀土元素特征,可能与蚀变流体温度较高有关,且富含F,Cl和CO2有关,成矿流体来源于岩浆期后热液。绿帘石-绿泥石化花岗岩稀土总量略有降低,LREE亏损而HREE略微富集,由流体蚀变、云母类矿物的吸附作用及早期钾化蚀变共同造成。Eu异常和Ce异常,表明钾化处于相对高温氧化条件下,而绿帘石-绿泥石化则处于相对低温和还原的环境中。蚀变花岗岩中REE与成矿元素关系密切,对岩体内部找矿具有一定的指示意义。

云南个旧富锡铜矿床表层土壤近红外光谱分析及其意义

在个旧卡房矿区矿体上部的覆盖层中均匀采集土壤样,用近红外光谱分析技术对样品进行测试分析。结果表明,近红外光谱技术能较好的识别出土壤中的矿物,包括蚀变矿物大致组合。将这些矿物组合与矿床的特征对比发现,土壤中的一些成分与深部矿体组份有一定程度的相关性,尤其是蚀变矿物,其与该区的蚀变条件是基本一致的。因此,推测土壤中的矿物成分可以用于指示深部矿体的一些信息,能为找寻该类型铜矿床提供一些依据。此外,矿床表层土壤近红外光谱信息是可以提供找矿依据的一种快速有效的研究手段,可以将其用于其他矿床类型的研究,尤其是为深部隐伏矿床以及地质环境较为脆弱的地区提供初步找矿依据。

云南个旧锡矿田：矿床模型及若干问题讨论

云南个旧是全球最大的锡多金属矿田，近20年来关于其成矿作用有多种认识，除了传统上与燕山期花岗岩有关外，还有海底喷流成矿和玄武岩成矿的新认识。通过野外调查和对比国内外相关研究的进展，指出尽管在个旧地区存在与海底喷流和玄武岩成矿可对比的一些现象，但缺少充要证据，进而在前人工作基础上提出了个旧锡矿田的矿床模型：即以白垩纪花岗岩（包括等粒花岗岩和斑状花岗岩）的隆起部位为核心，出现云英岩型、矽卡岩型、锡石硫化物型和脉状-网脉状石英电气石型矿化；成矿元素分带有：Sn—W—Mo—Bi，Sn-Cu，Sn—Pb—Zn；当围岩是三叠纪玄武岩时，沿玄武岩层内裂隙或与三叠纪法郎组碳酸盐岩的接触界面发育铜矿化，从白垩纪岩体向外元素分带为：Sn—Cu-W—Mo，Cu-Sn，Cu，Cu—Pb—Zn，铜主要来自玄武岩，而铅锌来自碳酸盐岩。此外，还进一步指出包括个旧锡矿田在内的滇东南和桂西80～90Ma锡钨多金属成矿可能是华南白垩纪岩石圈大规模伸展与成矿的组成部分。

云南个旧卡房碱性火山岩地球化学特征及意义

个旧地区印支期的火山作用主要有三期,即中三叠世安尼期、拉丁尼克早期和拉丁尼克晚期-诺利克期。通过对与成矿关系密切的卡房铜锡矿安尼期碱性火山岩的岩相学、地球化学研究发现： SiO2含量为42.22%~46.61%, MgO含量为8.61%~18.19%, K2O＋Na2O值为3.52%~7.52%, K2O/Na2O值为0.28~25.95, TiO2含量为2.03%~3.51%,属于碱性超基性火山岩；富集高场强元素（Nb、Ta）,大离子亲石元素（Rb、Ba、Sr、Cs）,稀土元素表现为LREE富集、HREE相对亏损的右倾稀土配分模式,δEu异常不明显,弱δCe负异常。卡房碱性火山岩成岩过程主要受地幔部分熔融作用,未经明显的地壳混染作用,源区可能来自于富含金云母（或角闪石）地幔橄榄岩部分熔融。卡房火山岩具有洋岛玄武岩（OIB）地球化学特征,形成于弧后裂谷盆地,并为铜锡矿提供了原始矿源层。

个旧—大厂地区地质构造演化及锡多金属成矿

个旧—大厂锡多金属矿床不是简单的燕山晚期地台环境的"花岗岩岩浆期后气液矿床",矿区地处三大板块的交接部位附近的个旧-大厂锡矿,前泥盆纪区域构造岩浆活动及锡多金属成矿作用强烈,泥盆纪—三叠纪裂谷作用和锡多金属成矿特点突出。泥盆纪受北西向同沉积断裂控制,在南丹 河池一带裂谷作用明显,发生了海底喷流成矿,加上印支—燕山期构造岩浆改造,形成了大厂锡矿。三叠纪受北东向个旧—兴义—晴隆同沉积断裂控制,在个旧、兴义一带发生的裂谷作用,伴随基性火山成矿、喷流热水沉积成矿和燕山晚期花岗岩改造(叠加)成矿,从而形成了个旧锡矿。

云南个旧锡矿的成矿时代

云南个旧锡矿经历了印支期海底基性火山—沉积成矿、海底喷流—沉积成矿和燕山晚期的花岗岩叠加改造成矿的作用。用ArAr、KAr和PbPb法分析了3个成矿系列的成矿年龄,结果表明,成矿系列Ⅰ的ArAr法坪年龄和等时线年龄为95.93±5.41～123.91±15.41Ma,KAr法表观年龄为112.50±2.25Ma,普通铅法年龄为210～240Ma;成矿系列Ⅱ的ArAr法坪年龄和等时线年龄为191.81±2.26～205.11±4.38Ma,KAr法表观年龄为186.01±3.72Ma,普通铅法年龄为200～230Ma;成矿系列Ⅲ的ArAr法坪年龄和等时线年龄为83.23±2.07～85.22±2.38Ma,KAr法表观年龄为43.49±0.87Ma,普通铅法年龄为83～116Ma。

云南个旧老厂细脉带型锡矿白云母^40Ar-^39Ar年龄及其地质意义

细脉带型锡矿是云南个旧矿田老厂矿区的主要矿床类型之一。文章利用40Ar-39Ar同位素测年方法对老厂细脉带型锡矿床白云母-电气石-石英脉中的白云母进行了年龄测试。结果显示,该白云母的40Ar-39Ar同位素坪年龄为(82.7±0.7)Ma,表明其形成时代为晚白垩世。进一步结合区域资料,指出包括个旧锡多金属矿床在内的右江褶皱带内与岩浆作用有关的矿床具有相同的成矿地质背景,为华南晚中生代岩石圈大规模伸展的产物。

云南个旧卡房铜矿床地质地球化学特征及其成因探讨

云南个旧是世界上最大的锡多金属矿田,卡房铜矿是个旧矿田主要的产铜区。卡房铜矿主要的矿床类型有两类:玄武岩层中或玄武岩与大理岩层间的似层状矿体以及花岗岩与围岩接触带矿体。围岩蚀变主要有夕卡岩化、阳起石化和金云母化。电子探针分析结果显示,卡房铜矿夕卡岩中的辉石主要为透辉石-钙铁辉石系列,石榴子石端元组分以钙铝榴石-钙铁榴石为主。流体包裹体及氢、氧同位素研究显示,从主成矿期到后成矿期,流体温度有显著降低(从260～360℃到160～280℃),而流体盐度则基本保持不变(从1.74%～12.51%到1.74%～11.93%)。氢、氧同位素组成表明,早期成矿流体主要以岩浆水为主,而晚期成矿流体可能在上升过程中与地层中的大气降水相混合。硫同位素分析结果表明,卡房铜矿似层状矿体中硫化物的硫来源于三叠系玄武岩,而燕山期花岗岩和三叠纪玄武岩共同为卡房铜矿接触带矿体提供了成矿所需的大部分的硫。铅同位素分析结果显示,卡房铜矿似层状矿体的成矿物质主要来源于三叠系玄武岩,而接触带矿体的铅可能主要来源于燕山期花岗岩。

云南个旧锡矿的玄武岩成矿

个旧锡矿产于个旧东区，是一个以锡铜为主的超大型多金属矿床，具有火山沉积成矿的某些特征。因遭受燕山期花岗岩的叠加改造，区内个旧组卡房段中玄武岩遭受强烈的变质，它又具有花岗岩热液成矿的特征。区内玄武岩的地质地球化学特征表明，印支期玄武岩中的Sn、Cu、Pb、Zn、Ag和Au的质量分数大多数高于世界玄武岩平均值的若干倍；矿石硫化物的硫同位素δ^34S为-1．5‰～4．0‰，平均＋0．207‰，在幔源硫附近；铅同位素模式年龄分为两组：第一组为180～240Ma，反映了印支期的火山沉积成矿作用；第二组为80～140Ma，反映了燕山期花岗岩的叠加改造成矿作用。区内印支期玄武岩为个旧锡铜多金属矿床的形成提供了主要的成矿物质，与成矿有直接联系。