Geology and Metallogenesis of the Sawayaerdun Gold Deposit in the Southwestern Tianshan Mountains, Xinjiang, China

The Sawayaerdun gold deposit, located in Wuqia County, Southwest Tianshan, China, occurs in Upper Silurian and Lower Devonian low‐grade metamorphic carbonaceous turbidites. The orebodies are controlled by a series of NE‐NNE‐trending, brittle–ductile shear zones. Twenty‐four gold mineralized zones have been recognized in the Sawayaerdun ore deposit. Among these, the up to 4‐km‐long and 200‐m wide No. IV mineralized zone is economically the most important. The average gold grade is 1–6 g/t. Gold reserves of the Sawayaerdun deposit have been identified at approximately 37 tonnes and an inferred resource of 123 tonnes. Hydrothermal alteration is characterized by silicification, pyritization, arsenopyritization, sericitization, carbonatization and chloritization. On the basis of field evidence and petrographic analysis, five stages of vein emplacement and hydrothermal mineralization can be distinguished: stage 1, early quartz stage, characterized by the occurrence of quartz veins; stage 2, arsenopyrite–pyrite–quartz stage, characterized by the formation of auriferous quartz veinlets and stockworks; stage 3, polymetallic sulfide quartz stage, characterized by the presence of auriferous polymetallic sulfide quartz veinlets and stockworks; stage 4, antimony–quartz stage, characterized by the formation of stibnite–jamesonite quartz veins; and stage 5, quartz–carbonate vein stage. Stages 2 and 3 represent the main gold mineralization, with stage 4 representing a major antimony mineralization episode in the Sawayaerdun deposit. Two types of fluid inclusion, namely H₂O–NaCl and H₂O–CO₂–NaCl types, have been recognized in quartz and calcite. Aqueous inclusions show a wide range of homogenization temperatures from 125 to 340°C, and can be correlated with the mineralization stage during which the inclusions formed. Similarly, salinities and densities of these fluids range for each stage of mineralization from 2.57 to 22 equivalent wt% NaCl and 0.76 to 1.05 g/cm³, respectively. The ore‐forming fluids thus are representative of a medium‐ to low‐temperature, low‐ to medium‐salinity H₂O–NaCl–CO₂–CH₄–N₂ system. The δ³⁴S_CDT values of sulfides associated with mineralization fall into a narrow range of ?3.0 to +2.6‰ with a mean of +0.1‰. The δ¹³C_PDB values of dolomite and siderite from the Sawayaerdun gold deposit range from ?5.4 to ?0.6‰, possibly reflecting derivation of the carbonate carbon from a mixed magmatic/sedimentary source. Changes in physico‐chemical conditions and composition of the hydrothermal fluids, water–rock exchange and immiscibility of hydrothermal fluids are inferred to have played important roles in the ore‐forming process of the Sawayaerdun gold–antimony deposit.     

同位素填图与深部物质探测(Ⅱ)：揭示地壳三维架构与区域成矿规律

地球深部是大规模成矿作用的“驱动机”、“供应源”和“传输带”。深入揭示深部物质组成与分布、物质循环与能量转换、三维架构与动力过程,对理解成矿作用至关重要。岩浆岩“探针”及区域同位素(如全岩Nd、锆石Hf)填图是探索深部物质组成与演化过程的主要手段,可以探测地壳深部物质组成的三维架构,揭示新生地壳/古老地壳/再造地壳的空间分布与时空演变,从而为提升区域成矿规律认识提供深部物质制约证据,有助于成矿潜力的定量半定量评价及其区域成矿预测。文章重点总结和探讨了岩浆岩全岩Nd同位素和锆石Hf同位素区域填图在解决地壳三维架构与成矿规律方面的应用成果,深入探讨了巨量岩浆岩发育的深部驱动机制及其成矿制约,对比总结了不同类型造山带(如中亚增生造山带、青藏高原碰撞造山带、秦岭复合造山带等)和不同克拉通的地壳深部组成结构与成矿制约特色。研究显示：不论是什么造山带和克拉通,深部年轻地壳分布区制约了铜金、铜镍等矿床的形成分布;古老地壳控制了大型钼矿、铅锌矿、稀有金属等矿产;两者过渡地带常常发育铁矿等。这些研究不仅揭示了区域成矿规律,而且对成矿预测与成矿潜力评价有潜在的应用价值,有可能成为成矿规律研究特别是深部物质探测及成矿背景研究的新方向。     

老挝万象省爬立山（PHaLek）铁矿床地质特征及成矿作用分析

爬立山铁矿床位于长山褶皱带北西端,是长山成矿带内与岩浆作用有关的一个大型铁矿床。根据野外地质观察及室内对含矿岩体、赋矿围岩和矿石开展的岩相学和地球化学研究发现：与成矿作用有关的花岗质岩石属钙碱系列准铝质的I型花岗岩,成岩的构造环境为火山弧。矿区内发育致密块状磁铁矿、孔洞状赤铁矿、砂砾土状铁矿等3种铁矿石。结合岩（矿）石微量元素分析,认为爬立山铁矿具有复合成矿作用特征,主要可分为3个成矿阶段：早期以与华力西期岩浆侵入作用有关的接触交代成矿作用为主,形成矽卡岩型磁铁矿;其后,在褶皱造山后形成的断陷盆地中,由于火山喷发（溢）作用形成孔洞状熔岩型赤铁矿;最后随着新生代地壳抬升,发生表生物理化学风化成矿作用,形成如今的砂砾土状型铁矿。     

大坪里—向阳坪地区铀成矿条件分析

从岩体特征、构造条件、围岩蚀变,以及矿石类型等方面总结了大坪里—向阳坪地区铀成矿特征,开展了铀成矿条件分析。并与沙子江铀矿床铀成矿特征相比较,确定找矿类型为受脆-韧性走滑断裂带控制的硅质脉型热液铀矿,为今后的工作奠定了基础。     

滇西马厂箐钼铜金矿床深部地质过程的系列成矿效应

[摘 要] 马厂箐钼铜金矿床是金沙江-哀牢山断裂带上与喜马拉雅期富碱斑岩有关的典型矿床之一,其成矿作用具有特殊性。本文应用透岩浆流体成矿理论,重点探讨了马厂箐钼铜金矿床深部地质过程中成岩与由地幔流体作用引发壳幔混染并形成系列成矿的关系。通过对马厂箐矿床成岩成矿时代的厘定、岩矿石稀土和微量元素、稀有气体及Pb-Sr-Nd 同位素研究,论证了成矿流体和岩浆流体均来自于富集地幔,这种成矿流体是包含于富碱岩浆并与其互不混溶的地幔流体。在上升运移过程中,地幔流体可随富碱岩浆的结晶成岩过程对岩体进行同步自交代蚀变而在斑岩体内或其深部形成矿床;也可与岩浆分离而独立运移,在岩体与围岩的接触带及地层围岩中进行交代蚀变成矿。在这一成岩成矿过程中, 引发并促进壳幔物质混染和叠加成矿,由此导致了马厂箐矿区成矿分带表现为从岩体到围岩、从高温到低温的不同矿种和不同类型的系列成矿效应。     

宁夏中南部铁矿地质特征及成矿规律探讨

宁夏中南部主要包括中卫市和固原市,该区属香山一卫宁北山一固原铜、金、铁、铅锌多金属成矿带,也是宁夏重要的金属矿产矿集区。研究区大地构造位于北祁连褶皱系走廊过渡带东段。铁矿床类型主要有中低温热液充填交代型和地表浅部氧化淋滤型;含矿层位主要为下石炭统前黑山组、臭牛沟组以及上石炭统土坡组,其沉积建造主要为粉砂岩一泥岩建造、石英砂岩建造、碳酸盐岩建造;矿体主要沿断裂分布,呈脉状、透镜状和似层状;具有原生矿石和氧化矿石两种矿石类型。成矿物质主要来源于地层;褶皱和断裂构造为成矿流体提供了有利的运移通道和淀积空间,从而对矿体的空间展布起到了控制作用;岩浆热液和围岩蚀变对成矿物质的聚集以及重新分配、改造起到了重要的作用。     

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华南燕山晚期构造-岩浆事件与成矿作用——来自广西大瑶山龙头山金矿床的地球化学约束

广西贵港大瑶山成矿带位于华南东南沿海成矿带西南端,对矿带内龙头山金矿黄铁矿化斑岩进行定年的结果为96.1±3.0 Ma,与区域内邻近的平天山侵入岩体(96.2±0.4 Ma)相同.龙头山矿床的Sr同位素组成与其锆石的REE特征表明,成矿作用伴随有大量的流体参与;矿化斑岩与区内侵入相岩石相同的形成时代以及矿化斑岩中锆石C...     

新疆阿尔泰铁矿:地质特征、时空分布及成矿作用

在前人工作基础上,文章综述了新疆阿尔泰铁矿地质特征和成矿背景.新疆阿尔泰铁矿赋矿地层主要为上志留统一下泥盆统康布铁堡组、中上泥盆统阿勒泰镇组和中泥盆统北塔山组,少数为下石炭统和下古生界.成因类型可划分为火山岩型、矽卡岩型、伟晶岩型、与花岗岩有关的热液型、与基性岩体有关的钒钛磁铁矿型和砂矿型6种,其中火山岩型和矽卡岩型为...