Isotopic Geochronology of the Late Paleozoic Kanggur Gold Deposit of East Tianshan Mountains, Xinjiang, NW China

Abstract: The Kanggur gold deposit lies in East Tianshan mountains, eastern section of Central Asia orogenic belt. The gold mineralization occurs on the northern margin of the Aqishan‐Yamansu Paleozoic island arc in the Tarim Plate. It was hosted mainly in Middle‐Lower Carboniferous calc‐alkaline volcanic rocks, and controlled by the distributions of syn‐tectonic intrusions and ductile shear zones. In order to determine ore‐forming age of the Kanggur deposit, samples were collected from ores, wall rocks, altered rocks and intrusions. The dating methods include Rb‐Sr isochron and Sm‐Nd isochron, and secondly ⁴⁰Ar/³⁹Ar age spectrum, U‐Pb and Pb‐Pb methods. Based on the mineral assemblage and crosscutting relationship of ore veins, five mineralization stages are identified. This result is confirmed by isotope geochronologic data. The first stage featuring formation of pyrite‐bearing phyllic rock, is mineralogically represented by pyrite, sericite and quartz with poor native gold. The Rb‐Sr isochron age of this stage is 2905 Ma. The second stage represents the main ore‐forming stage and is characterized by native gold–quartz–pyrite–magnetite–chlorite assemblage. Magnetite and pyrite of this stage are dated by Sm‐Nd isochron at 290.47.2 Ma and fluid inclusion in quartz is dated by Rb‐Sr isochron at 282.35 Ma. The third mineralization stage features native gold–quartz–pyrite vein. In the fourth stage, Au‐bearing polymetallic sulfide‐quartz veins formed. Fluid inclusions in quartz are dated by Rb‐Sr isochron method at 25821 Ma. The fifth stage is composed of sulfide‐free quartz–carbonate veins with Rb‐Sr age of 2547 Ma. The first and second stages are related to ductile‐brittle deformation of shear zones, and are named dynamo‐metamorphic hydrothermal period. The third to fifth stages related to intrusive processes of tonalite and brittle fracturing of the shear zones, are called magmato‐hydrothermal mineralization period. The Rb‐Sr isochron age of 2905 Ma of the altered andesite in the Kanggur mine area may reflect timing of regional ductile shear zone. The Rb‐Sr isochron age of 28216 Ma of the quartz‐syenite porphyry and the zircon U‐Pb age of 2757 Ma of tonalite in the north of Kanggur gold mine area are consistent with the age of gold mineralization (290‐254 Ma). This correspondence indicates that the tonalite and subvolcanic rocks may have been related to gold mineralization. The Rb–Sr, Sm‐Nd and U‐Pb ages and regional geology support the hypothesis that the Kanggur gold deposit was formed during collisional orogenesis process in Late Variscan.     

辽宁省盖县猫岭金矿床地质特征及成因探讨

猫岭金矿床赋存于早元古代辽河群盖县组变质岩系内,空间上与印支期猫岭似斑状花岗岩体关系密切,两者相距仅0.2km,花岗岩体本身有金矿化及蚀变现象。矿床的成矿热液为一种氧逸度较低、富集碱金属及卤族(特别是Cl)元素的热液,其δD=-77——80‰,δ¹⁸O=6.05-7.38‰,δ³⁴S=6.15-10.3‰。矿床的矿石铅与猫岭花岗岩体长石铅的同位素组成不尽一致。根据上述特征可认为:猫岭金矿床为与中生代花岗岩有关的、典型的岩浆热液型金矿床,但金属成矿物质除成矿热浪本身带来外,部分还由成矿热液萃取自容矿围岩-辽河群盖县组。     

东坪金矿成矿时代研究

东坪金矿是我国在碱性岩中发现的第一个大型金矿,本文在详细野外观察的基础上,用K-Ar法、~(40)Ar/~(39)Ar法测定了成矿期花岗细晶岩脉、主成矿期矿石的同位素年龄,确定东坪金矿成矿时代为燕山期。     

浙江中岙古火山热液金矿多阶段成矿及金的富集规律

本矿产于元古界浅变质火山岩中,受断裂构造控制明显,为浅成中温古火山热液金矿.矿化富集于火山热液期,成矿具多阶段性,并有明显叠加造成金的富化.金的富集具一定规律,对找矿有重要指导意义.     

内蒙古中部大青山新地沟绿岩带型金矿的成矿时代

内蒙古新地沟金矿床产于大青山太古宙花岗岩-绿岩带中,受色尔腾山群柳树沟组中基性火山岩系和韧性剪切带控制.容矿岩石主要是变安山质-英安质火山岩类.为解决主矿体的形成时代,采用石英40Ar/39Ar法,直接测定了含金石英细脉浸染状矿石中石英的形成时代,结果表明新地沟金矿的形成时代为1991.43～1988.93Ma.由此提出新地沟金矿的成因主要与吕梁期韧性剪切带中的变质变形作用有关.     

新疆康古尔金矿成矿阶段及其年代学

根据矿床的地质特征，矿脉穿插关系，矿物共生组合及矿石Rb─Sr等时线，Sm─Nd等时线、40Ar／39Ar年龄谱等年代学资料，认为康古尔金矿热液成矿过程主要经历了4个成矿阶段。Ⅰ为磁铁绿泥蚀变岩成矿阶段；Ⅱ为黄铁矿石英脉成矿阶段；Ⅲ为多金属硫化物石英脉成矿阶段；Ⅳ为碳酸盐石英脉矿化阶段。矿化类型以蚀变岩型为主。     

Geochemical Characteristics of Two Types of Ores from Jinshan Shear Zone—hosted Gold Deposit,Jiangxi,with a Discussion on the Mechanism of Two—stage Mineralization

Two types of gold ores,siliceous mylonite and quartz vein,formed at the first and second stages of mineralization respectively, can be clearly recognized in the shear zone-hosted gold deposit at Jinshan, Jiangxi.Similarity in REE and trace elements between the siliceous mylonite and the country rocks indicates that the ore metals were supplied by the surrounding strata during the first stage of mineralization.On the other hand, as indicated by fluid inclusion data,the ore-forming fluid at the second stage was of meteoric origin and the precipitation of gold was caused by phase separation.     

Relationship of antimony with gold mineralization in the ore districts of Eastern Kazakhstan

In Eastern Kazakhstan, Sb mineralization is the most widespread in the Irtysh and Bakyrchik ore districts of the West Kalba gold-bearing belt. It is spatially related to disseminated gold-sulfide ores at some deposits and is structurally and spatially isolated at others. Disseminated gold-sulfide mineralization is localized in Carboniferous carbonaceous-terrigenous carbonate rocks. It is marked off by zones of dynamic metamorphism and foliation and is characterized by the ribbon-like-lenticular morphology of ore deposits. Later Sb (predominantly, quartz-antimonite) mineralization is formed in an extension setting as brecciated/veined ores. In combination with gold-sulfide ores, Sb mineralization is more diverse. For example, microparageneses with berthierite, native Sb, aurostibite, ullmannite, jamesonite, and tetrahedrite coexist with pocket-vein quartz-carbonate-antimonite mineralization in the gold-sulfide ores of the Suzdal’skoe deposit. Also, Sb-containing minerals such as arsenopyrite and pyrite are observed. Two temperature regimes of mineralization are established here: 418-300 °C for gold-polysulfide mineralization and 280-200 °C for later Sb mineralization. The isotopic composition of antimonite sulfur at the Suzdal’skoe, Zherek, Zhanan, Bakyrchik, and Dal’ny I deposits shows close values within the interval 5³⁴S of -3.8 to 2.5%c, suggesting its great-depth origin. No visible gold is found in the antimonite of the quartz-antimonite veins, but atomic-absorption analysis reveals few ppm or more gold. Point X-ray analysis indicates the possible presence of the so-called “invisible” gold. Microstructural observations, temporal relationships of the parageneses, and studies of gas-liquid inclusions at the Suzdal’skoe deposit permit assigning Sb mineralization to the second productive gold-polysulfide stage of the ore deposition. The late antimonite stage of mineralization is separated from the gold-polysulfide stage by 7 Myr long intramineralization tectonic shifts. Gold-polysulfide mineralization (248.3 ± 3.4 Ma) was synchronous with Triassic tectonomagmatic activity.     

浙西金鸡岩金矿床成矿特征与成矿机理研究

对浙西金鸡岩金矿进行了流体包裹体、岩石和矿石地球化学研究,以阐明其成矿特征和成矿机理．金鸡岩金矿是由多阶段成矿作用形成的,第一阶段以钼矿化为主,成矿温度较高;第二和第三阶段以金矿化为主,成矿温度较低．该金矿的成矿压力小、深度浅．成矿流体具低盐度、弱酸性及较高矿化度的特点,其中尚有大量大气水的混入．区内的前寒武纪浅变质岩系属于原始矿源层,而中生代火山岩,特别是次火山岩属于直接矿源岩．就成矿机理来看,金主要是呈金硫络合物形式迁移的,其次是被硅胶吸附呈胶体状态迁移的,而成矿流体的温度和压力下降、ｐＨ值降低以及溶液的氧化还原电位改变是导致金沉淀的重要因素．区内胶体金的沉淀主要是由于温度的降低和电解质的加入引起凝胶作用,使金随硅胶一同沉淀的．     

青海大场金矿床地质特征及成因探讨

青海大场金矿床位于北巴颜喀拉造山带的中段,为区域印支造山过程晚期Au-Sb成矿作用的产物.该矿床为具有层控性和受断裂构造、隐伏岩浆活动控制的金矿床.矿体主要呈脉状、似脉状和透镜状赋存于三叠系巴颜喀拉群砂岩板岩互层组内,并严格受断裂破碎带的控制.大场金矿床先后经历了金、锑2期矿化,矿化平均成矿深度分别为5.9km和6.9 km,锑矿化深度略浅于金矿化.成矿流体总体属中温、较低盐度、低密度的CO2-H2O-N2-H2S-CH4±CO±有机碳氢化合物体系.该矿床与造山型金矿具有相似的地质地球化学特征,其金矿化属造山型金矿的中成矿化,其锑矿化为造山型金矿的浅成矿化.     

东坪金矿主要地质特征及控矿条件

东坪金矿产于水泉沟偏碱性杂岩体与太古宇桑干群变质岩之内接触带,矿石工业类型为石英脉和蚀变岩型,以前者为主.矿脉带走向为NNE,主要载金矿物为石英、黄铁矿、镜铁矿、黄铜矿和碲金矿,金成色937~990,矿化蚀变主要是钾长石化和硅化;肉红色钾长石化是东坪金矿乃至赋存于水泉沟杂岩体中所有金矿的典型特征.矿化共分5个阶段,其中第2、3两个阶段,即镜铁矿-自然金-石英阶段和多金属硫化物-自然金-石英阶段为主要成矿阶段.水泉沟杂岩体在东坪金矿成矿过程中,不仅提供了热动力,而且提供了成矿物质和矿化剂;太古宙桑干群涧沟河组提供了部分成矿物质,近E-W向尚义-崇礼-赤诚深大断裂控制了水泉沟金矿田的产出,而NNE和NW向两组裂隙则控制了东坪金矿矿体的产出.     

河南桐柏老湾金矿床和花岗岩的年龄及其意义

通过老湾金矿床矿石中石英和花岗岩中的 主要造岩矿物石英、钾长石的40Ar/39Ar定 年,获得成矿年龄为91.5±1.0Ma,成岩期高温坪年龄为104.1±1.0Ma～108.9±0.3Ma,等 时线 年龄为102.8±0.1Ma～108.7±0.1Ma,因此认为成岩成矿具同时性。结 合 秦岭-大别造山带的演化历史,提出老湾金矿床和老湾花岗岩均形成于燕山晚期,成矿略晚 于成岩,构造应力环境为挤压向伸展转化的过渡期或以张应力为主的构造体制。     

小秦岭金矿田典型矿脉矿化趋势面分析与深部预测

小秦岭石英脉型金矿田是我国重要的金矿富集区, 区内一些重要矿山已逐渐成为危机矿山, 深部找矿是当务之急.运用趋势面分析法对3个典型东西向南倾矿脉的矿体厚度及品位进行处理, 分析了断裂构造控矿特征及矿化富集规律.结果表明: 东西向矿脉主要向南西侧伏; 控矿断裂具有由南西向北东斜上左行逆冲的活动性质; 多阶段矿化具有"Ⅰ阶段成脉、Ⅱ阶段金矿化、Ⅲ阶段金铅叠加"的过程; 由矿体侧伏与断裂产状波状起伏联合控制的近平行等间距展布的2组结构线的交汇部位是矿化富集地段; 据此指出了各矿脉深部找矿预测的主要方向.      

西澳大利亚Forrestania绿岩带构造特征及Ni—Cu—Au成矿规律与找矿发现

Forrestania绿岩带（FGB）位于西澳大利亚Yilgarn克拉通东南部,是澳大利亚重要的Ni-Cu-Au成矿带,属于澳大利亚一级Ni、Cu成矿远景区和三级Au成矿远景区。FGB地区的Ni—cu矿床主要与带内的超镁铁质岩墙有关,属于富硫化物接触交代型成矿,主要以巨厚层状产出在基底长英质碎屑沉积岩和上覆的科马提岩之间。FGB地区金矿的形成主要与北北西向和北北东向构造内的石英脉有关,属于石英脉型金矿,是含镍硫化物富集（Ni）、多期后成矿构造运动、岩浆活动、变质作用和热液交代（Au）等多种地质活动长期复杂混合的产物。其形成过程主要分为以下几个阶段：早期Ni的沉积阶段、早期区域构造运动阶段、持续构造活动阶段、Ni矿体解体和Au元素富集阶段、Au矿脉的形成阶段。根据上述理论指导,笔者分析成矿特征后,选出Au成矿远景区,进行物化探综合勘查,圈定出异常区域,并在异常区内发现了较好的矿化线索。通过实践证明了理论推断的可信度。     

内蒙大水清金矿带交代作用及其与金矿化关系

大水清金矿带是华北克拉通中有代表性的改造型绿岩金矿之一。它产于前东武纪绿岩地体中安家营子石英二长岩体内外接触带附近的剪切带中。金矿化交代主要受后阶段张性脆裂控制，而剪切带早阶段韧性剪切作用无明显矿化交代，后者主要为成矿交代提供有益的江游交代构造环，境即成矿交代蚀变作用和剪切带同步的两阶段演化模式。大水清金矿带的交代作用有四个阶段：即用长石化阶段，绿泥石化阶段，黄铁绢英岩化和石英－硫化物阶段以及石英－碳酸盐化阶段。第三阶段由五个亚阶段组成：即黄铁绢英岩化和强硅化－强黄铁矿化，石英－多金属硫化物交代，石英－贫扶矿充填交代和细粒黄铁矿充填交代。其中前四个亚阶段是本区金的主要成矿期．当韧性剪切转化为张性脆裂时产生的骤然扩容和伴随发生的交代体系转变为富硅体系的钾交代和石英－硫化物交代是金矿成矿的关键。本文还研究和探讨了该金矿成矿交代流体的性质及交代的物理化学环境。     

Composition and genesis of the Konevinsky gold deposit,Eastern Sayan,Russia

The Konevinsky gold deposit in southeast Eastern Sayan is distinguished from most known deposits in this region (Zun-Kholba, etc.) by the geological setting and composition of mineralization. To elucidate the cause of the peculiar mineralization, we have studied the composition, formation conditions, and origin of this deposit, which is related to the Ordovician granitoid pluton 445–441 Ma in age cut by intermediate and basic dikes spatially associated with metavolcanic rocks of the Devonian–Carboniferous Ilei Sequence. Four mineral assemblages are recognized: (1) quartz–pyrite–molybdenite, (2) quartz–gold–pyrite, (3) gold–polysulfide, and (4) telluride. Certain indications show that the ore was formed as a result of the superposition of two distinct mineral assemblages differing in age. The first stage dated at ~440 Ma is related to intrusions generating Cu–Mo–Au porphyry mineralization and gold–polysulfide veins. The second stage is controlled by dikes pertaining to the Devonian–Carboniferous volcanic–plutonic association. The second stage is characterized by gain of Hg and Te and formation of gold–mercury–telluride paragenesis.     

The Zaderzhninskoe gold deposit: Mineral composition,fluid inclusions,and age (South Verkhoyansk region)

Based on results of study of the regional position, chemical composition of ores, fluid inclusions, and age relationships between mineralization and igneous rocks, we propose a geological and genetic model for the formation of gold mineralization of the Zaderzhninskoe deposit. Mineralization is located in the tectonic node of the intersection of two regional structures in the supraintrusive zone of a latent granitoid pluton among the terrigenous rocks of the Verkhoyansk complex, which are regionally metamorphosed to the greenschist facies. The sequential deposition of three types of mineralization—Au-quartz (including early low-gold Au-As and late productive Au-Pb-Zn mineralization), Au-rare-metal, and Au-silver—has been established. The Au-Bi (Te) assemblage contains native bismuth, bismuthinite, hedleyite, Bi sulfotellurides, gustavite group minerals, and secondary minerals—Bi oxides and Bi tellurites with low-grade gold. Hg-containing electrum and kustelite, Ag-Sb and Ag-Pb-Sb sulfosalts, stutzite, Te-Pb-containing canfieldite, freibergite, and Au and Ag sulfides are indicator minerals of the Au-Ag (Sb) assemblage. Ore formation occurred at temperatures from 90 to 340 °C, with the participation of lowly and moderately concentrated solutions with CO₂ ± CH₄ ± N₂ gas phase. A decrease in temperature from Au-quartz mineralization (200-220 °C) to the late epithermal one (160 °C) and a slight increase in the concentration of solutions (up to 10 wt.% NaCl equiv.) have been established. The deposit resulted from the intricate multistage geodynamic evolution of the South Verkhoyansk region. Ore-forming processes are associated with the evolution of magmatic objects. Dating of igneous rocks yields the following ages: diorites—130-137 Ma (Rb-Sr), spessartites—126 ± 3 Ma (Rb-Sr), and kersantites—115 ± 1.7 Ma (Ar/Ar). Early concordant Au-quartz (Au-As) mineralization of the deposit is comparable with metamorphic-related Au-quartz veins of the Yur-Bular type, and its age is taken as > 137 Ma. The time of formation of Au-quartz (Au-Pb-Zn) mineralization is estimated at 123.5 ± 1.6 Ma (Ar/Ar) and is coeval with the time of intrusion of the Early Cretaceous granitoids of the South Verkhoyansk region. The imposed low-temperature mineralization undoubtedly has a younger age. Its formation was followed by the successive deposition of Au-rare-metal mineralization at the final stage of formation of granitoid plutons (~ 120 Ma) and Au-Ag mineralization in the period 100 ± 5 Ma, i.e., the time of formation of late-stage granodiorite-granite intrusions.     

Ore-bearing duplexes at the Malomyr orogenic gold deposit, Amur Region

This study made it possible to reconstruct three stages of the structure formation at the large Malomyr gold deposit in the Amur Region: (1) premineral folding and left-lateral strike-slip faulting; (2) synmineral thrust faulting, and (3) postmineral dike and neotectonic stage. The study has shown that the formation of the Malomyr deposit was related to the system of duplexes as the structural traps that are the most favorable for ore deposition. The left-lateral duplex hosts the major orebodies composed of refractory ore at the Central site of the deposit, whereas the highest-grade and readily processable ore from the Quartzitic site is localized in the right-lateral duplex. The development of both duplexes during the same stage of thrust faulting indicates that readily processable and refractory ores were formed almost simultaneously. The type of mineralization depends on structural conditions of ore deposition. Refractory ore with invisible gold was formed under compression, whereas the readily processable ore with free gold was deposited in the extension setting.     

Ar-Ar Dating on the Metallogenesis of the Dongchuang Gold Deposit in the Xiaoqinling Area

The Dongchuang gold deposit in the Xiaoqinling area is an orogenic-type lode gold deposit. It is one of the few superlarge (>100 t Au) deposits in China. Although it has been argued that it was formed in the Mesozoic, related isotopic age data have not been reported in previous studies. Based on detailed geological study, the authors have carried out isotopic dating on various metallogenic generations. The ore-forming process of the Dongchuang gold deposit consists of four stages: coarse-grained pyrite-bearing quartz veins (stage Ⅰ), fine-grained pyrite-quartz veinlets (stage Ⅱ), multi-sulfides (stage Ⅲ) and carbonate-quartz veinlets (stage IV). Ar-Ar dating on mineral separates of stages Ⅰ, Ⅱ and Ⅲ yields plateau ages of 142.9±2.9 Ma, 132.2±2.6 Ma and 128.3±6.2 Ma, respectively. Sericite separates from stage Ⅱ assemblage also yield an Ar-Ar isochron age of 132.6±2.7 Ma, similar to the Ar-Ar plateau age. These results suggest that the Dongchuang gold deposit was mainly formed during 143-128 M     

豫西花山花岗岩北东侧金矿成矿特征

依据地质、地球物理、矿体特征 ,对花山花岗岩北东侧金矿成矿进行了剖析 ,认为成矿物质来源于太古代闪长岩与太古代片麻岩和燕山期花岗岩 ,成矿在半封闭和开放两类构造条件下进行。封闭构造很少有燕山期花岗岩成矿物质的加入 ,但可形成较富的小矿体 ,开放构造有大量的燕山期花岗岩成矿物质的加入 ,可形成规模较大、品位稍低的金矿体。成矿过程表现出持续性、多阶段性和继承性