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     

甘肃岷县寨上金矿成矿年代及矿床成因探讨SCIEI北大核心CSCD

寨上金矿位于西秦岭大规模卡林-类卡林型金矿床集中地之中,是近二十年来探获的又一超大型金矿。通过对寨上金矿的6件矿石样品中的载金矿物黄铁矿进行Rb、Sr、Re、Os同位素分析,获得Rb-Sr、Re-Os等时线年龄分别为273±10Ma、273Ma±22Ma。该数据大于前人所获的二期成矿阶段年龄,在西秦岭已探明的金矿床中尚无报道,反映了寨上金矿更早一期的成矿年龄为273Ma,这也为该区域寻找金矿床拓宽了时间轴。Sr、Os、S同位素及稀土和微量元素研究表明,寨上金矿成矿物质为深源与壳源物质的混合。二叠纪时位于岷礼前陆盆地的吴家山隆起经历了强烈的隆升延展作用,岩浆热液沿断裂通道上升到有较高Au背景值盆地中的褶皱带,使地层中的Au活化富集,在构造有利部位卸载成矿,形成早期寨上金矿床,后期钨矿化及金矿化叠加在早期金矿床之上。寨上金矿第一期金成矿的年龄在时空上与阿尼玛卿洋盆闭合、共和坳拉谷俯冲碰撞、江里沟及中川喜马拉雅型岩体的侵入时间基本吻合,符合“地壳加厚有利于形成金矿床及喜马拉雅型花岗岩与金矿关系密切”的结论,对在该区域寻找同时代金矿床具有一定的指示意义。     

豫西熊耳山矿集区栾灵金矿床辉钼矿Re-Os同位素年龄及其地质意义

豫西栾灵金矿床地处熊耳山金多金属矿集区南部马超营断裂带北侧,金矿体产于构造破碎带中,呈钾长石石英脉体和蚀变岩产出,为本区一种新的金矿化类型。文章为厘定栾灵金矿床的成矿时代,采用辉钼矿Re-Os同位素定年方法,测得栾灵金矿6件辉钼矿样品的Re-Os同位素模式年龄为(161±3)Ma~(164±2)Ma,加权平均年龄(163±1)Ma(MSWD=0.68),等时线年龄(163±2)Ma(MSWD=1.5),表明栾灵金矿床形成于晚侏罗世早期。与祁雨沟、前河金矿等早白垩世(125 Ma)金矿相比,栾灵金矿的成矿作用早约38 Ma。这些年龄数据表明,该矿床在区域上可能与南泥湖-三道庄、上房沟钼矿等形成于同一成矿系统,它的发现为在熊耳山地区寻找相似成矿地质条件的金、钼矿床提供了依据。     

胶西北东季金矿床钾长石和石英的Ar-Ar年龄及其意义

东季金矿床位于焦家_新城金矿带中 ,其围岩蚀变以钾长石化为特征。作者采用Ar_Ar同位素定年方法对东季金矿床矿脉中的石英及其两侧的蚀变钾长石进行了测试 ,获得钾长石Ar_Ar坪年龄为 (116 .0 7± 0 .30 )Ma ,等时线年龄为 (116 .34± 0 .81)Ma ,石英脉中石英Ar_Ar坪年龄为 (115 .2 2± 0 .2 0 )Ma ,等时线年龄为(114.44± 0 .16 )Ma。这些年龄基本上代表了焦家断裂成矿带的成矿时限。     

甘肃礼县中川地区金矿成岩和成矿年龄的SHRIMP厘定

甘肃省礼县中川地区属于礼（县）岷（县）金矿带的东段,成矿作用与中川花岗杂岩体有密切的关系。运用高分辨率和高灵敏度离子探针（SHRIMP）测试技术,获得了中川花岗杂岩体形成的精确年龄,主侵入时代为210～160 Ma（可信度95%,MSWD=1.4）,该花岗岩体属于燕山早期-印支期造山运动的产物;3颗锆石（4个测点）的SHRIMP测试结果表明,中川地区金成矿的年龄为197～162 Ma,证实礼县中川地区金成矿于中川花岗岩体形成及稍后的时间段。年龄测试和地质剖面测量资料都证实,中川花岗岩体南部地层应该划在中石炭统地层中。与中川花岗杂岩体地质情况类似的碌础坝、 柏家庄、 闾井、 教场坝、 温泉等岩体外接触带仍然有很大的找矿前景。     

Mineralization Ages of the Jiapigou Gold Deposits,Jilin

The Jiapigou gold deposits are typical vein type deposits associated withArchaean greenstone belts in China. According to the crosscutting relationships between dykesand auriferous veins, single hydrothermal zircon U-Pb dating and quartz K-Ar,~(40)Ar-~(39)Ar andRb-Sr datings, the main mineralization stage of the Jiapigou deposit has been determined to be2469-2475 Ma, while mineralization superimposition on the gold deposit occurred in1800-2000 Ma and 130-272 Ma. They form a mineralization framework of one oldermetallogenic epoch (Late Archaean-Early Proterozoic) and one younger metallogenic epoch(Mesozoic) of gold deposits in Archaean greenstone belts in China.     

新疆多拉纳萨依金矿一带花岗岩类形成时代及其对金矿成矿作用的制约

新疆阿尔泰造山带西南缘分布有多拉纳萨依、赛都、哲兰德等大中型金矿床,近年又发现沃多克等小型金矿.这些金矿主要赋存于糜棱岩化石英闪长岩中,岩石地球化学特征表明沃多克和多拉纳萨依金矿含矿石英闪长岩特征基本一致,属同一期岩浆活动的产物,而明显不同于两矿床之间的萨热乌增英云闪长岩.沃多克金矿含矿石英闪长岩和萨热乌增英云闪长岩LA-ICP-MS锆石U-Pb年龄分别为(299.4±4.1) Ma和(317.7±1.5) Ma.二者分别属于后造山和后碰撞花岗岩.沃多克含金石英闪长岩年龄限定了多拉纳萨依一带金矿形成时代不早于300 Ma,结合前人的研究成果分析,表明其主要成矿时期为290 Ma左右.萨热乌增等岩体的形成早于金矿形成时代,金的成矿作用与该期大规模花岗岩体的侵位无关.     

Episodes of Cenozoic Gold Mineralization on the Eastern Margin of the Qinghai-Tibet Plateau:~(40)Ar/~(39)Ar Dating and Implication for Geodynamic Events

A lot of new gold deposits have been found on the eastern margin of the Qinghai-Tibet Plateau during the past two decades. Among them, three main types of gold deposits have been recognized, including quartz-vein-type, shearzone-type and porphyry-type. The former two types of gold deposits are mainly hosted within metamorphic rocks, while the latter is related to Cenozoic magmatism. Although all of these gold deposits are believed to have been formed during the uplift process of the Qinghai-Tibet Plateau in the Cenozoic era (Wang et al., 2002b), precise isotopic age constraints have still been lacking until quite recently. This paper presents new ^40Ar/^39Ar data of some gold deposits on the eastern margin of the Qinghai-Tibet Plateau, which indicate that gold mineralization in the region occurred in response to the episodic stages of the orogenies. Recently obtained ^40Ar/^39Ar data on quartz and feldspars from several gold deposits, such as the Sandiao deposit, the Baijintaizi deposit, the Pusagang deposits, provide new constraints on gold mineralization on the eastern margin of the Qinghai-Tibet Plateau. Geochronological studies of gold deposits along the Daduhe River indicate that there are three stages of gold mineralization. The early two stages occurred as early as 65.1 Ma in the Shuibaiyang deposit and 58.95 Ma in the Ruoji deposit, while the latter stage occurred as late as 25.35 Ma in Baijintaizi and 24.70 Ma in Sandiao. Isotopic dating of three plagioclases from the Beiya deposit, Zhifanggou deposit and Luobodi deposit and a K-feldspar from the Jinchangqing deposit in Yunnan Province indicates that these deposits were formed at two stages. The Zhifanggou and Jinchangqing deposits have early stage records as old as 58.82 Ma in Zhifanggou and 55.49 Ma in Jinchangqing, but all of the above four deposits in Yunnan have late stage records of 23.18 Ma in Jinchangqing, 24.54 Ma in Zhifanggou, 24.60 Ma in Luobodi and 24.56 Ma in Hongnitang. The above results suggest that the gold deposits on the eastern margin of the Qinghai-Tibet Plateau were formed concentratedly at two main episodes, i.e. the end of the Paleocene (about 58 Ma) and the boundary between the Paleogene and the Neogene (about 25 Ma). The later episode appears to be looks like more important and was coupled with the Sichuan movement, which was extensively activated at that period. The beginning of the Cenozoic Era (about 65 Ma) might be another episode of gold mineralization, but only one deposit (Shuibaiyang) in this study has been proved to have been be formed at this stage and might be earlier than the initial collision between the Indian Plate and the Eurasia Plate. In view of geology, the above three episodes of gold mineralization are associated with three events of tectonicmagmatism and/or fluid events. Even though the gold deposits (for example, the Shuibaiyang deposit, Ruoji deposit and Pusagang deposit) were formed at different episodes, all of them are genetically related to tectonic movements in largescale shear zones. It looks like theat tectonic events (including large-scale strike-slip) between Paleogene and Neogene had a wide influence upon gold mineralization, with new deposits formed and old deposits enriched or superimposed to be a higher grade by new stage of mineralization. The above data suggest that gold deposits were not only concentrated in some areas, but also formed mainly at different boundaries of geological times, indicating that there existed some peak stages of gold mineralization (metallogenic episodes), and that the gold deposits were formed mainly by episodic mineralization.     

Metallogeny of the Huaaobaote Ag-polymetallic deposit in Inner Mongolia: Constraints from zircon and cassiterite U-Pb datingSCIEI北大核心CSCD

花敖包特超大型银多金属矿床位于大兴安岭南段,矿体主要呈脉状赋存于二叠系寿山沟组的断裂中,部分矿体呈囊状产于寿山沟组与华力西期蛇绿岩的接触带中。矿体主要包括银铅锌锑矿体、锡铜矿体、铜铅锌矿体、锡矿体和银矿体。花敖包特矿床可划分为4个成矿阶段,分别为石英-锡石-毒砂-黄铁矿阶段(Ⅰ阶段)、石英-绢云母-锡石-黄铜矿-毒砂-磁黄铁矿-闪锌矿-黝铜矿阶段(Ⅱ阶段)、石英-绢云母-萤石-方解石-闪锌矿-方铅矿-黄铁矿-辉锑矿-含银硫盐矿物阶段(Ⅲ阶段)和石英-方解石-黄铁矿-辉银矿-深红银矿阶段(Ⅳ阶段)。对花敖包特矿区2件次流纹岩样品开展了LA-ICP-MS锆石U-Pb定年,分别获得135.4±0.8Ma和134.8±0.8Ma的年龄。对成矿Ⅰ阶段锡矿石和Ⅱ阶段锡铜矿石进行了LA-ICP-MS锡石U-Pb定年,分别获得136.3±2.0Ma和134.3±1.7Ma的加权平均年龄。定年结果表明,花敖包特矿床次流纹岩、锡矿体和锡铜矿体均形成于早白垩世。尽管二者形成时间相近,但脉体穿切关系及矿化分带特征均表明次流纹岩并非成矿物质和成矿流体的主要来源。本文认为,花敖包特矿床真正的成矿地质体为隐伏于矿区深部的次火山岩钟,其矿床成因类型为与次火山岩相关的热液矿床。     

西藏冈底斯成矿带的斑岩-矽卡岩成矿系统:--来自斑岩矿床和矽卡岩型铜多金属矿床的Re-Os同位素年龄证据

笔者通过对冈底斯成矿带驱龙、厅宫斑岩铜矿区和甲马、知不拉等矽卡岩型铜多金属矿区的辉钼矿样品进行的Re-0s法同位素定年研究,获得驱龙、厅宫、甲马和知不拉等矿区的精确成矿年龄。4件驱龙斑岩铜矿区辉钼矿样品的Re-Os模式年龄介于(15.75±0.42)Ma～(16.23±0.90)Ma之间,等时线年龄为(15.99±0.32)Ma;7件厅宫斑岩铜矿矿区辉钼矿样品的Re-Os模式年龄介于(15.5±0.3)Ma～(16.3±0.3)Ma之间,等时线年龄为(15.49±0.36)Ma;在矽卡岩型铜多金属矿区中,7件甲马矿区辉钼矿样品的Re-Os模式年龄介于(15.4±0.2)Ma～(15.5±0.2)Ma之间,等时线年龄为(15.18±0.98)Ma;5件知不拉矿区辉钼矿样品的Re-Os模式年龄介于(16.88±0.28)Ma～(17.06±0.27)Ma之间,等时线年龄为(16.90±0.64)Ma。斑岩铜矿区和矽卡岩型铜多金属矿区所获得的年龄数据基本一致,其年龄明显晚于中生代弧间盆地和碰撞型花岗岩的发育时间,同时矽卡岩型铜多金属矿床在空间上亦分布于斑岩铜矿床的外围。因此笔者认为甲马和知不拉等铜铅锌矿床与冈底斯成矿带新生代晚期大规模成矿形成的斑岩铜钼矿床属于统一的斑岩-矽卡岩成矿系统,是由深源花岗质岩浆的岩浆-热液系统在不同的围岩介质条件成矿的产物。     

熊耳山—外方山矿集区中生代Au-Mo成矿系统

熊耳山—外方山矿集区位于秦岭造山带之华北板块南缘,经历了复杂的碰撞造山过程,成矿时间跨度大,成矿强度高,成矿作用多样。复合造山过程和相应的成矿作用已被深入研究,但成矿系统的划分和叠加成矿作用尚需研究。本文将熊耳山—外方山矿集区发育的Au-Mo矿床划分为造山型Mo矿床、斑岩型Mo矿床、岩浆热液脉型Mo矿床、造山型Au矿床和岩浆热液型Au矿床5个类型,对应5种成矿系统：(1)造山型Mo矿床形成于250~227 Ma的同碰撞环境和227~194 Ma的后碰撞环境,为变质热液萃取壳源Mo成矿;(2)斑岩型Mo矿床形成于163~135 Ma的洋陆俯冲环境和135~116 Ma的岩石圈减薄环境,为岩浆热液携带幔源或壳源Mo成矿;(3)岩浆热液脉型Mo矿床形成于227~194 Ma的后碰撞环境,为岩浆热液携带幔源Mo成矿;(4)造山型Au矿床在三叠纪发生了预富集作用,主要形成于163~135 Ma的洋陆俯冲环境和135~103 Ma的岩石圈减薄环境,为变质热液萃取壳源Au成矿;(5)岩浆热液型Au矿床仅形成于135~103 Ma的岩石圈减薄环境,为岩浆热液携带壳源Au成矿。矿集区主要存在两种叠加成矿作用,即不同构造背景下多种成矿系统的叠加和同一构造背景下不同成矿系统的叠加。     

秦岭造山带柞水-山阳矿集区夏家店金矿床成矿时代及其地质意义

柞水-山阳矿集区位于秦岭造山带中部,区内矿产资源丰富,金矿找矿近年来不断取得突破,发现了多个大-中型金矿床,然而区内金矿成矿时代、成矿地质背景一直存在争议,直接制约矿集区金矿床找矿工作。夏家店金矿床是该区大型金矿床,矿体受断裂构造控制,金矿石类型有角砾岩型、碎裂岩型、糜棱岩型3种。围岩蚀变强烈,主要由硅化、方解石化、绢云母化、高岭土化、萤石化、重晶石化等,与金成矿关系最密切的是硅化、方解石化、萤石化。热液成矿期可划分为石英阶段、石英-方解石-萤石-硫化物阶段、方解石阶段。文章选取夏家店金矿床主成矿期的方解石、萤石等矿物进行了Sm-Nd同位素测试工作,获得等时线年龄为(139.64±0.98)Ma,表明成矿时代为晚侏罗世。结合区域构造-岩浆成矿作用特征,认为夏家店金矿床成矿作用与晚侏罗世—早白垩世构造-岩浆事件有关。据此将柞水山阳矿集区金矿床成矿年龄厘定在140Ma左右,为秦岭造山带伸展的地球动力背景下构造-岩浆热液演化的产物。通过与区内晚侏罗世—早白垩世构造-岩浆成矿事件对比,文章首次提出柞水-山阳矿集区存在140 Ma左右的金矿床成矿事件,为下一步在柞水-山阳矿集区开展金矿床勘查工作提供了重要依据。     

吉林夹皮沟金矿带岩脉和蚀变绢云母定年及金矿成矿时代

吉林夹皮沟金矿床的矿化年龄一直存在争议。采用先进的SHRIMP测年方法测得夹皮沟二道沟金矿床的花岗闪长岩脉锆石的2 0 6Pb/ 2 3 8U年龄为 (2 2 3± 2 )Ma ;八家子金矿床的石英正长斑岩锆石的2 0 6Pb/ 2 3 8U年龄为 (2 41± 6 )～ (2 18± 6 )Ma。这一结果与前人测得的K Ar年龄基本相符。这两条岩脉与含金石英脉同构造空间 ,形成时代相近 ,因此上述岩脉年龄大体反映了金矿化年龄。同时还测得八家子金矿床蚀变绢云母的 4 0 Ar 3 9Ar等时线年龄为(2 0 3 975± 0 5 2 7)Ma ,进一步证明金矿化发生在中生代印支期。矿石中含有大量的方铅矿 ,还存在矿物及元素的分带 ,这些特征表明夹皮沟金矿床不太可能是新太古代或元古代形成的变质热液矿床 ,更大可能是中生代与岩浆活动有关的岩浆热液矿床     

Ore-forming mechanism of Caledonian W-Sn deposit in the Nanling Range: A case study from the Luojiachong deposit,sourthwestern Hunan Province.SCIEI北大核心CSCD

近来南岭地区加里东期钨锡找矿勘查取得较大突破,但其成因机制研究仍相对缺乏。湘西南苗儿山岩体西北部的落家冲矿床是近年新发现的加里东期钨锡矿床,具有良好的钨锡多金属矿找矿前景,其成矿流体的特征和成矿机制有待查明。在详细的野外地质调查基础上,落家冲矿床的成矿过程可划分为四个阶段:蚀变花岗岩-白钨矿阶段(Ⅰ)、云英岩-白钨矿-锡石阶段(Ⅱ)、石英脉-白钨矿阶段(Ⅲ)和石英脉-硫化物阶段(Ⅳ)。本文选取第Ⅰ阶段的锆石和锡石开展了U-Pb定年和锆石Hf同位素分析,对四个成矿阶段的石英矿物进行了流体包裹体以及H-O同位素的研究。获得的锡石U-Pb反等时线年龄(433.0±11Ma)与蚀变花岗岩锆石U-Pb年龄(430.7±2.3Ma)在误差范围内一致,表明矿区的成岩成矿作用均发生于加里东晚期。流体包裹体研究显示第Ⅰ阶段到第Ⅳ阶段,均一温度分别集中在260-380℃、260-320℃、200-320℃和180-220℃之间,呈逐渐降低的趋势,盐度则表现为由第Ⅰ阶段到第Ⅱ阶段陡降,第Ⅱ阶段到第Ⅳ阶段总体变化不大的特点(平均值分别为16.9%、3.9%、4.8%和3.7%NaCleqv)。成岩成矿定年结果、各成矿阶段的成矿流体特征,结合锆石εHf(t)=-7.6--5.0、tDM2=1565-1711Ma,和石英矿物的δ18OH_(2)O值从第Ⅰ阶段(3.97‰-5.34‰)到第Ⅳ阶段(-4.99‰--5.10‰)逐渐降低的特点,以及区域岩体的地球化学特征,本文认为落家冲钨锡矿床是加里东期起源于元古宙地壳重熔的岩浆在经历了高分异演化作用后,流体的沸腾作用以及温度下降造成成矿流体中钨锡等矿质的沉淀所形成。     

兰坪盆地白秧坪铅锌铜银多金属矿床:成矿年代及区域成矿作用

针对沉积岩容矿铅锌矿床的定年难题,选用闪锌矿的Rb-Sr法和成矿阶段方解石的Sm-Nd法,对白秧坪铅锌铜银多金属矿床3个矿段(吴底厂、李子坪、富隆厂)分别测定,取得了较好的定年效果。测得白秧坪铅锌多金属矿床的铅锌成矿年龄为30~29Ma,而且3个矿段结果可互相印证。进而通过成矿年龄的探讨,认为矿区发生过2次矿化事件,一期为以铜为主的矿化,发生于古新世末-始新世初期,印度板块-欧亚板块强烈挤压后的应力松弛阶段成矿;另一期是以铅锌为主的矿化,发生于30~29Ma,对应于始新世末-渐新世早期挤压后应力松弛阶段。两期矿化事件在上千千米的"三江"成矿带上普遍存在,但在不同部位铅锌成矿时代略有不同,印度板块的东北角首先对接欧亚板块,位于岬角处正碰位置铅锌成矿要稍早于两侧的铅锌矿化事件。     

内蒙古东部二连浩特-乌兰浩特地区金矿化特征的初步研究

研究区属含古老地块并经中生代改造的中古生代造山带,存在金、锡等丰度较高的锡林浩特元古宙杂岩、古生代蛇绿岩及板块缝合带、二叠系火山岩、中生代伸展构造背景下的大规模火山-侵入活动及锡多金属成矿作用.本区金矿化类型主要有:韧性剪切带中的石英脉型、蚀变岩型金矿,产于幔源中基性侵入岩中的铜金矿,燕山晚期斑岩型铜金矿,与燕山期次火山岩浆活动有关的脉状铜矿床中的伴生金矿化,微细浸染型金矿化,浅成低温热液型金矿化等.研究区金矿成矿时代可分为242~229Ma、169~161.8Ma、132~159Ma (可能以130~140Ma为主)、127~109.2Ma四个区间.认识到存在印支期成矿、燕山期多阶段成矿等特点对于区内金矿勘查有重要意义.新发现7个矿床(点)的伴生金矿化.毛登、大井等多金属矿床的伴生金矿化具有重要的潜在工业意义.     

新疆东天山红山金矿成矿时代研究

红山金矿区位于秋格明塔什—黄山韧性剪切带东段北缘,矿床成因研究表明,红山金矿的形成严格受该韧性剪切带控制,属于与韧性剪切带有关的糜棱岩型、超糜棱岩型矿床。花岗质糜棱岩中角闪石276.3Ma的Ar-Ar坪年龄给出了红山金矿床成矿事件的时代上限。金矿石样品中绢云母246.9Ma和246.5Ma的Ar-Ar坪年龄记录了金矿床主成矿期的时代。糜棱岩中新生白云母246.5Ma的Ar-Ar坪年龄,在误差范围内和金矿石样品中绢云母的Ar-Ar坪年龄完全一致,不仅为红山金矿床的剪切带型成因提供了进一步的佐证,也对金成矿时代给予了进一步的限定。     

云南大坪金矿新元古代成矿事件——来自热液锆石和闪长岩U-Pb年代学及Hf同位素的约束

大坪金矿是哀牢山-红河韧性剪切带南段最重要的大型金矿床之一,由于其成矿时代和构造背景一直存在争议,不利于带内金矿床成矿模型的建立和进一步找矿勘探。本文利用LA-ICP-MS对矿区内含金石英脉中热液锆石、闪长岩和花岗闪长岩脉中岩浆锆石开展了U-Pb年代学研究,获得热液锆石U-Pb年龄为760±10 Ma,表明大坪金矿区可能存在新元古代金矿化事件;获得闪长岩和花岗闪长岩脉的锆石U-Pb年龄分别为773±9 Ma和766±9 Ma,与区域上Rodinia超大陆裂解和哀牢山地区的晋宁-澄江期大规模火山-岩浆活动事件时代一致。热液锆石与闪长岩、花岗闪长岩脉具有相似的Hf同位素组成特征和在误差范围内一致的年龄,表明新元古代金矿化事件可能与闪长岩和花岗闪长岩脉的侵入有密切的成因联系。本文新元古代成矿事件的厘定,结合前人的新生代始新世—渐新世为大坪金矿主要成矿时期的研究结果,表明大坪金矿可能是新元古代和新生代不同岩浆-构造-热液事件叠加成矿作用的产物。     

Potassium–Argon Ages of the Epithermal Gold–Silver Mineralization in the Haenam–Jindo Area,Southwestern Korea

The Haenam–Jindo area, located on the southwestern margin of the Korean Peninsula, was the site of vigorous volcanic activity during the Late Cretaceous and Early Tertiary periods. Large parts of the area record strong hydrothermal alteration, and there exist many clay–alunite and gold–silver deposits. We undertook potassium–argon (K–Ar) age dating of five mineral samples (including adularia, sericite and alunite) from the Eunsan, Moisan and Gasado epithermal gold–silver deposits in this area. The purities of the samples were confirmed by X‐ray diffraction analysis. The K–Ar ages of adularia from the Eunsan deposit and adularia and sericite from the Moisan deposit (related to gold–silver mineralization) are 75.0 ± 1.6, 74.7 ± 1.6 and 75.1 ± 1.6 Ma, respectively. The similarity of these ages, combined with the close proximity and similar geochemical characteristics of the deposits, indicates that the mineralization occurred as part of a single hydrothermal system. The K–Ar ages of alunite at the surface and adularia at depth within the Gasado deposit are 82.2 ± 1.9 and 70.7 ± 1.9 Ma, respectively, revealing that the clay–alunite and gold–silver mineralization formed at different ages. K–Ar age data indicate that the gold–silver mineralization in this area occurred mainly at 75–70 Ma, resulting from hydrothermal activity in the Haenam–Jindo area (82–70 Ma). This is the first time that the mineralization of precious metals in Korea has been identified during this period.     

安徽沙坪沟斑岩钼矿锆石U-Pb和辉钼矿Re-Os年龄

沙坪沟斑岩钼矿是大别成矿带近年发现的超大型矿床。在对矿化特征分析的基础上,对其进行了成岩成矿年代学研究。采用LA-ICP-MS锆石U-Pb测年技术,得到含矿岩体的成岩年龄。细粒石英正长岩与中粒石英正长岩分别形成于122.51±0.81Ma和121.5±1.3Ma,正长斑岩形成于120.7±1.1Ma。通过矿床辉钼矿Re-Os同位素分析,获得其模式年龄为100±1.8～113.6±1.7Ma。成岩与成矿时差约7Ma,指示含矿热液活动时限较长。长时间的热液活动可能是形成沙坪沟超大型斑岩钼矿床的重要因素。沙坪沟钼成矿时间与大别带钼矿化时间(133～110Ma)高度一致,与东秦岭晚期钼矿化时间相同。大别带钼矿是秦岭-大别成矿带的组成部分,形成于相同构造背景下,是区域构造岩浆作用的产物。