青海鄂拉山北段牦牛沟铜金矿辉钼矿Re-Os年龄及其地质意义

陈永福, 张　栋, 路英川, 刘　鹏, 王晓军, 傅　扬, 李文良, 郭晓东

中国人民武装警察部队黄金地质研究所, 河北廊坊 065000



青海鄂拉山北段牦牛沟铜金矿辉钼矿Re-Os年龄及其地质意义

陈永福, 张栋, 路英川, 刘鹏, 王晓军, 傅扬, 李文良, 郭晓东

中国人民武装警察部队黄金地质研究所, 河北廊坊 065000

摘要:鄂拉山是中央造山带西段之东昆仑和西秦岭的结合部位, 由于研究程度不高而影响着大家对其区域印支期成矿作用、成矿地质背景及地球动力学过程的认识。因此, 本文从特定矿床类型时空分布特征反演成矿地质背景和地球动力学过程的方法入手, 以鄂拉山北段的牦牛沟铜金矿为研究对象, 详细研究其矿床地质特征和成矿年代学, 将其与区域东昆仑典型斑岩-矽卡岩型矿床进行时空对比研究, 并结合传统区域大地构造研究和成岩证据, 试图探讨区域成矿地质背景、地球动力学过程以及鄂拉山的归属问题。结果表明, 牦牛沟铜金成矿为小型矽卡岩矿床, 成矿与木勒儿花岗闪长岩关系密切。与铜金成矿有关的矿化主要为硅化、绢云母化、黄铜矿化和黄铁矿化。矿床矿石矿物有黄铜矿、黄铁矿以及辉钼矿等。首次获得有意义的辉钼矿Re-Os加权平均年龄为(238.7±1.4) Ma。同时, 三叠纪鄂拉山与东昆仑具有相似的地质演化特征,属于东昆仑南北向挤压构造背景下的成矿事件。东昆仑三叠纪成矿可能有两个相对峰期: 约237 Ma以矽卡岩矿床为主的铁铜成矿期和约222 Ma的以斑岩为主的铜金成矿期, 前者可能和俯冲碰撞转换期的板块断离有关, 后者则与后碰撞拆沉背景有关。

关键词:辉钼矿Re-Os年龄; 牦牛沟; 鄂拉山; 东昆仑

本文由中国地质调查局地质调查项目“青海省秦岭西段金多金属矿产成矿规律与找矿预测研究”(编号: 1212011220899)资助。收稿日期: 2015-04-26; 改回日期: 2015-08-09。责任编辑: 闫立娟。

受成矿年代学研究的制约, 早期研究(Sawkins, 1990)认为特定矿床类型与其成矿大地构造环境具有一定的关系(Kerrich et al., 2005)。近来研究表明成矿系统是地球动力学过程的有机组成, 特定矿床类型的时空分布可以约束其产出的大地构造环境,并可与传统大地构造研究和成岩证据共同约束区域地球动力学演化(Groves et al., 2007; Pirajno, 2009)。因此, 精确的成矿年代学研究对理解成矿作用及其地质演化至关重要。而辉钼矿Re-Os定年体系由于其高浓度的Re和缺少普通Os而被认为是有效的成矿年代学方法之一(Stein et al., 1997)。

鄂拉山是我国重要铜多金属成矿带之一(宋治杰等, 1995), 区域分布着众多矽卡岩矿床。其中,北段以小型铜金矿为主, 成矿时代初步确定为晚三叠世(青海省地质三队, 1985); 而南段成矿年龄集中于223 Ma左右(刘建平等, 2012; 王辉等, 2015),且部分矿床具有斑岩成矿潜力(李东生等, 2009)。然而, 有限的年代学研究使得学者对鄂拉山三叠纪地质演化的认识存在较大差异, 部分学者(Chen et al., 2012; 杨立功等, 2013)认为鄂拉山作为东昆仑的一部分是布青山—阿尼玛卿洋向北俯冲碰撞的结果;部分学者(孙延贵等, 2001, 2004)则认为是扬子板块或西秦岭有限向西斜向俯冲的结果。而斑岩成矿系统(包括斑岩和矽卡岩矿床)常形成于造山环境, 多见于俯冲或后碰撞阶段(Meinert et al., 2005; Richards, 2009; Hou et al., 2012), 是有效的大地构造环境指标。本文从鄂拉山北段牦牛沟矽卡岩矿床的精确辉钼矿Re-Os年代学研究入手, 综合对比区域东昆仑和鄂拉山成矿年代学数据并辅以少量成岩证据, 试图探讨三叠纪鄂拉山区域归属及地球动力学演化过程。

东昆仑造山带(图1a)是我国中央造山带的重要组成部分(Pan et al., 2012), 是青藏高原内可与冈底斯相媲美的一条巨型构造岩浆岩带(莫宣学等, 2007)。带内花岗岩形成可划分为前寒武纪、早古生代(如, 李瑞保等, 2014)、晚古生代(如, 刘彬等, 2012; 陆露等, 2013)—早中生代和晚中生代—新生代四个时段。其中尤以三叠纪花岗岩最为发育(莫宣学等, 2007), 且240 Ma的幔源岩浆底侵和岩浆混合(刘成东等, 2004; Chen et al., 2012)作用标志着俯冲碰撞转换时期(莫宣学等, 2007; 张智勇, 2008)。

鄂拉山处于秦祁昆复合部位东昆仑东段(图1a),同时也属于东昆仑造山带六个次级构造岩浆带之一的宗务隆—鄂拉山构造岩浆带(Pan et al., 2012)。在晚古生代时期, 鄂拉山构造岩浆带沿宗务隆山—同仁隆务峡及以南的部分地区, 受后碰撞地壳伸展影响形成裂陷盆地或小洋盆, 从而构成布青山—阿尼玛卿古特提斯洋的分支洋(张智勇等, 2004), 向南可能与阿尼玛卿裂陷连通构成三向连结构造, 其中北支为苦海—赛什塘蛇绿混杂岩带, 其北带缺乏陆缘弧火山岩带和蛇绿混杂岩带, 仅有前寒武纪裂解岩块和石炭纪—二叠纪浅海碳酸盐岩块组成的叠置带(孙延贵等, 2004)。早、中三叠世盆地裂陷达高峰, 接受了五千至万余米厚的砂岩、板岩组成的类复理石沉积; 中下三叠统最厚逾两万米, 含多层滑塌堆积和含早二叠世的外来灰岩块, 并在中三叠统上部出现变基性凝灰岩、凝灰质砂岩、流纹质火山角砾凝灰岩、凝灰质砂板岩夹流纹岩等火山—沉积岩(宋治杰等, 1995)。火山岩年龄集中在210~240 Ma, 为钙碱性系列的I型岩浆, 属造山带火山岩(孙延贵等, 2001)。

东昆仑区域成矿主要集中在三叠纪中晚期(丰成友等, 2009b; 吴建辉等, 2010), 以陆陆碰撞或陆内俯冲有关的造山型金矿和矽卡岩型铁多金属矿床为主(丰成友等, 2004), 并呈现出斑岩型成矿带的雏形(丰成友等, 2009b)。而鄂拉山成矿带则呈北西—南东展布(宋治杰等, 1995), 南段产出赛什塘、铜峪沟、索拉沟及日龙沟等中大型铜、锡多金属矿床; 北段有牦牛沟铜金矿以及沙龙瓜孔、占顺南、占顺北、都休玛、阿尕泽等小型铜、铁矿床(点)(图1b)。矿体多沿花岗闪长岩岩体内外接触带发育, 均产于矽卡岩中(青海省地质三队, 1985)。

图1　阿尔金—祁连—昆仑俯冲增生山链平面图(a; 许志琴等, 2006)和牦牛沟铜金矿区域地质图(b; 根据青海省地质三队, 1985修改)Fig. 1　Paleozoic Altun–Qilian–Kunlun mountain chains of subduction accretional type in the western part of the Central Orogenic Belt (a; after XU et al., 2006) and Regional geological map of the Maoniugou Cu-Au skarn ore deposit (b; modified after Qinghai No. 3 Geological Party, 1985)TRMB-塔里木地块; NCB-华北板块; BYSG+QT-巴彦喀拉—松潘甘孜地块+羌塘地块; NQLS-北祁连俯冲杂岩带; QL-祁连地块; SQLF-南祁连走滑断裂; NQDMS-柴北缘俯冲杂岩带; GDM-柴达木地块; QMTGS-祁漫塔格俯冲杂岩带; N.EKL-东昆北地块; CKLS-昆中俯冲杂岩带; S.EKL-东昆南地块; EKLF-东昆仑走滑断裂; ANMQS-阿尼玛卿俯冲杂岩带; ALTF-阿尔金走滑断裂; ALT-阿尔金地体TRMB-Tarim Block; NCB-North China Block; BYSG+QT-Bayan Har–Songpan-Ganzi and Qiangtang terranes; NQLS-North Qilian Subduction Complex Belt; QL-Qilian Terrane; SQLF-South Qilian Strike-slip Fault; NQDMS-Northern Margin of Qaidam Subduction Complex Belt; GDM-Qaidam Terrane; QMTGS-Qimantag Subduction Complex Belt; N.EKL-Northern East Kunlun Terrane; CKLS-CentralEast Kunlun Subduction Complex Belt; S.EKL-Southern East Kunlun Terrane; EKLF-East Kunlun Strike-slip Fault; ANMQS-Animaqin Subduction Complex; ALTF-Altun Strike-slip Fault; ALT-Altun terrane

1　矿床地质特征

牦牛沟(又名泽很错)铜金矿是鄂拉山多金属成矿带北段的一个小型矽卡岩型矿床, 位于木勒尔花岗闪长岩体(γδ51b)北东侧外接触带(青海省地质三队, 1985), 矿床距岩体约3 km(图1b)。矿床容矿围岩为中三叠统古浪提群a组板岩段(T2gla-2), 该段地层自下而上分别为黑云母岩化板岩、变泥岩以及变泥岩与长石石英砂岩互层。其中变泥岩下部夹似层状、透镜状长石石英砂岩, 并见有透镜状、不规则状大理岩零星分布, 铜金矿体产在该层中、下部(图2)。木勒尔岩体北东部花岗闪长岩与围岩地层呈“港湾”状接触, 顶面起伏大, 总体倾向北东, 并产生北东向宽约3 km的黑云母角岩化带。花岗闪长岩具中细粒自形粒状结构、局部呈似斑状结构, 块状构造。岩石的矿物成分为斜长石(45%~60%)、钾长石(10%~20%)、石英(15%~20%)、角闪石(5%~8%)、黑云母(3%~7%), 局部含有辉石。副矿物有磁铁矿、锆石、磷灰石、金红石、榍石等。SiO2含量变化小,介于61.79%~67.86%, 全碱含量较高, Na2O+K2O=6.47%~7.16%, 属钙碱性岩石系列(青海省地质三队, 1985)。

图2　牦牛沟金矿床地质简图(据青海省地质三队, 1985修改)Fig. 2　Sketch geological map of the Maoniugou gold ore deposit(modified after Qinghai No. 3 Geological Party, 1985)

牦牛沟铜金矿主要的矿体为ICu Au、IIAu和IIIAu(图2), 均与矽卡岩相伴产出。由于受近东西向和北东向接触带构造控制, 三个矿体分别呈不规则脉状、囊状和透镜状。矿体走向近东西或北东, 倾向近南或南东, 倾角54º~68º。矿体斜切围岩或者总体与围岩产状一致, 与围岩呈不规则状接触。其中, I号Cu Au矿体较为典型, 长28.7 m, 厚0.16~1.54 m, 平均厚度为0.54 m; 品位较富, Cu为0.38%~12.43%; Au为8~22 g·t-1, 平均12.06 g·t-1(青海省地质三队, 1985)。与铜金成矿有关的矿石矿物有黄铜矿、黄铁矿、辉钼矿等, 呈星点状或细脉状分布。金在矽卡岩中呈自然金产出, 其形态有树枝状、棒状、片状、粒状、板状等(青海省地质三队, 1985)。

与铜金成矿有关的围岩蚀变主要为矽卡岩化,其次是硅化、绢云母化。矽卡岩化主要包括石榴石矽卡岩, 透辉石石榴石矽卡岩和透辉石矽卡岩。主要的矽卡岩矿物有石榴石、透辉石、符山石、阳起石、绿泥石、绢云母、石英、方解石等。牦牛沟铜金矿蚀变矿化可分为矽卡岩期和热液期, 其中热液期分为石英-硫化物阶段(主要形成金属硫化物、绿泥石、绢云母、石英和方解石)和碳酸盐阶段(形成大量方解石和少量石英等)。石英-硫化物阶段为主成矿期。

2　辉钼矿Re-Os同位素年龄测定

6个辉钼矿Re-Os年龄样品均采自牦牛沟铜金矿(经纬度为: 36º05'17"N; 99º37'52"E)矿体(图2), 样品为黄铜矿化、辉钼矿化含矽卡岩矿石, 其中辉钼矿以浸染状和团块状产出(图3)。样品分布均匀, 具有较强的代表性。辉钼矿均采用人工破碎重砂淘洗法进行分离, 并在双目镜下挑纯, 纯度大于99%, 晶体无氧化、无污染。辉钼矿的Re、Os同位素测试在中国地质科学院国家地质实验测试中心进行, 采用美国TJA公司生产的电感耦合等离子体质谱仪TJA X-series ICP-MS测定同位素比值。实验原理和分析流程参见文献(屈文俊和杜安道, 2003; Du et al., 2004)。辉钼矿标准物质为GBW04436 (JDC), 本次试验测得平均年龄为(141.0±2.2) Ma, 与标准物质标准年龄值(139.6±3.8) Ma(Du et al., 2004)相比在误差范围内。测定空白显示Re为1.2 pg, Os为0.4 pg。

牦牛沟铜金矿辉钼矿Re-Os同位素测定数据见表1, 6件辉钼矿中Re的含量较高且比较接近, 水平为(239.7±8.0)~(180.0±1.5) μg·g-1, 总体187Re与1 8 7O s含量比较协调, 辉钼矿模式年龄介于(237.2±3.3) ~(240.7±3.3) Ma之间, 加权平均年龄为(238.7±1.4) Ma(图4)。而等时线年龄为(248±16) Ma(图4), 等时线与187Os轴的截距在不确定度范围内接近于零, 说明187Os不含放射性成因成分。表明辉钼矿Re-Os年龄是可靠的, 可以用t = (1/λ)ln(1+187Os/187Re)方程计算(Stein et al., 1997),但等时性年龄误差相对较大。

表1　牦牛沟矽卡岩型铜金矿中辉钼矿Re-Os同位素数据Table 1　Re-Os isotopic data for molybdenite from the Maoniugou skarn Cu-Au ore deposit

图3　牦牛沟铜金矿床矿石和部分测年样品特征Fig. 3　Features of ores and dating samples of the Maoniugou Cu-Au ore deposita-石榴石矽卡岩; b, c, d-辉钼矿年龄样品; Mo-辉钼矿; Ccp-黄铜矿; Cal-方解石; Grt-石榴石a-garnet skarn; b, c, d-molybdenite dating sample; Mo-molybdenite; Ccp-chalcopyrite; Cal-calcite; Grt-garnet

3　成矿年代学及其地质意义

鄂拉山多金属成矿带北段虽然矿床(点)众多,但至今没有可靠的成矿年代学数据, 这极大限制了区域成矿作用及地球动力学过程研究。本次研究显示辉钼矿Re-Os年龄数据没有初始和普通Os, 其辉钼矿等时线年龄为(248±16) Ma, 误差较大; 而模式年龄非常一致, 其加权平均年龄为(238.7±1.4) Ma,为有意义的成矿年龄数据。且矿物学研究表明, 辉钼矿与黄铜矿、黄铁矿以及矽卡岩共生, 其年龄可代表矿床物质沉淀的时间。

图4　牦牛沟铜金矿辉钼矿Re-Os等时线模式年龄和加权平均年龄Fig. 4　Re-Os isochron diagram and weighted average model age diagram for Maoniugou Cu-Au ore deposit

以牦牛沟铜金矿为代表的鄂拉山北段矿床成矿年龄为238.7 Ma, 而以赛什塘铜矿床为代表的鄂拉山南段成矿年龄约为223 Ma(刘建平等, 2012; 王辉等, 2015), 这预示着鄂拉山多金属成矿带三叠纪可能存在两期成矿事件或者同期成矿事件的不同成矿阶段。资料表明东昆仑西段祁漫塔格成矿带具有同样的特征, 中晚三叠世与花岗岩有关的矽卡岩和斑岩型成矿具有两个峰期, 且矽卡岩成矿早于斑岩成矿约14 Ma(丰成友等, 2010)。基于以上分析, 笔者认为鄂拉山和东昆仑可能具有相同的成矿动力学过程。因此, 对区域东昆仑和鄂拉山较为典型的斑岩型和矽卡岩型矿床成矿年代学和矿床时空分布进行分析。结果(表2; 图5)显示, 区域成矿年龄统计结果相似, 均落在244.2~234.5 Ma和224.7~213 Ma两个范围。其中, 前者以矽卡岩型矿床为主, 后者以斑岩型矿床为主。对相关数据合并统计后, 显示两个峰期年龄分别为约237 Ma和约222 Ma(图6),相差约17 Ma。另外, 与牦牛沟铜金矿有关的木勒尔岩体花岗闪长岩岩石化学数据显示活动陆缘的特征(青海省地质三队, 1985)。共同表明鄂拉山和东昆仑可能具有相似的成矿作用和构造背景(俯冲或者碰撞环境)。

结合传统大地构造研究对约束区域地球动力学过程(Groves et al., 2007; Pirajno, 2009)将有极大帮助。在鄂拉山, 共和盆地周缘存在两期清晰的构造岩浆事件, (235±2) Ma的黑马河岩体岩浆事件和(218±2) Ma的温泉岩体岩浆事件(张宏飞等, 2006)。相邻的东昆仑东部约格鲁花岗闪长岩((242±6) Ma)和角闪辉长岩((239±6) Ma)锆石U-Pb年龄显示相近年龄的岩浆事件(刘成东等, 2004)。对于东昆仑地区,其北侧宗务隆带南侧发育的246 Ma天骏南山花岗岩、238 Ma青海湖南山花岗岩和215 Ma二郎洞花岗岩(郭安林等, 2009), 中东部香日德以北的244 Ma花岗岩类成岩峰期(Chen et al., 2012)和244 Ma的阿斯哈闪长岩锆石U-Pb年龄(李碧乐等, 2012)以及香日德地区的223 Ma的二长花岗岩年龄和220 Ma的花岗闪长岩年龄(罗明非等, 2014), 还有东昆仑山中部的241~236 Ma花岗岩类年龄(张雪亭等, 2005)以及东昆仑西部祁漫塔格地区230~ 237 Ma的发育闪长质暗色微粒包体的中三叠世花岗岩和形成于204~228 Ma的具有斑状或似斑状结构的晚三叠世高分异富钾花岗岩事件(丰成友等, 2012)同样显示东昆仑也存在着相似的两期岩浆事件。另外, 对比中央造山带的秦岭造山带三叠世花岗岩浆活动表明, 也具有两个相对峰期: 分别为235~225 Ma的小规模石英闪长岩和220~210 Ma左

右的大规模高钾钙碱性花岗岩(秦江锋, 2010)。陈衍景(2010)也对秦岭印支期构造背景、岩浆活动及成矿作用进行了详细的总结(在此不做详细讨论), 表明秦岭地区在245~200 Ma期间发生了一次强烈的成矿作用。总体相对晚于东昆仑。这些不完全统计的岩体年龄说明, 包括鄂拉山在内的东昆仑以及秦岭区域地球动力演化过程中, 确实存在着两期和矽卡岩、斑岩成矿有关的岩浆活动。这表明代表第一成矿峰期的237 Ma左右, 东昆仑区域演化至少发展为俯冲或俯冲后环境。而区域沿柴达木微陆块分布的264 Ma左右的早二叠世弧火山岩和267 Ma的纳木龙俯冲型花岗岩表明该时期存在着苦海—赛什塘分支洋的向北俯冲消减(张智勇等, 2004)。同样,东昆仑祁漫塔格地区(284.3±1.2) Ma、(270.9± 0.9) Ma、(261.5±3.7) Ma和(257.1±0.7) Ma的花岗岩类年龄, 东昆仑东段埃坑德勒斯特(268.5±0.8) Ma的二长花岗岩锆石年龄以及白日其利镁铁质岩墙群的(251±2) Ma结晶侵位年龄都表明东昆仑在251 Ma之前仍处于俯冲背景下的大陆边缘弧环境(王秉璋等, 2009; 熊富浩等, 2011; 杨延乾等, 2013; Li et al., 2013)。而260~230 Ma, 东昆仑已处于俯冲向碰撞转换阶段(罗照华等, 2002; 张智勇, 2008; Huang et al., 2014)。那么, 东昆仑矽卡岩、斑岩成矿的两个峰期(约237 Ma和约222 Ma)显然处于俯冲后环境。

表2　东昆仑区域成矿典型矿床年代学Table 2　Mineralization age of representative ore deposits in East Kunlun

图5　东昆仑区域斑岩-矽卡岩型矿床分布及成矿年代学(数据见表2, 底图据潘桂堂, 2004)Fig. 5　Distribution and ore-forming geochronology of porphyry-skarn ore deposits in East Kunlun (for data see Table 2, base map after PAN, 2004)

图6　东昆仑区域斑岩-矽卡岩型成矿年代学直方图(数据见表2)Fig. 6　Histogram for mineralization age of porphyry-skarn ore deposits in East Kunlun (for data see Table 2)

东昆仑多期复合造山决定着区内斑岩-矽卡岩型矿床的时空分布(吴建辉等, 2010)。而区域大地构造研究表明, 包括鄂拉山在内的东昆仑成矿具有俯冲后成矿特征, 约237 Ma的成矿峰期可能与俯冲结束碰撞开始时的板片断离作用有关, 板片断离作用导致软流圈物质上隆并诱发地幔楔的减压熔融,产生镁铁质岩浆, 在下地壳底部造成底侵作用(罗照华等, 2002; Huang et al., 2014), 形成矽卡岩成矿为主的铁铜矿床; 而约222 Ma的成矿峰期则可能与岩石圈拆沉背景有关(张宏飞等, 2006), 主要发育斑岩型铜金矿床。但最新找矿趋势看, 东昆仑区域具有斑岩型矿床的优越地质条件(丰成友等, 2009b),区域斑岩-矽卡岩系统型矿床找矿潜力很大。

4　结论

牦牛沟矿床是东昆仑东段鄂拉山北部的一个小型矽卡岩型铜金矿床。其辉钼矿等时线年龄为(248±16) Ma, 误差较大; 而模式年龄非常一致, 其加权平均年龄为(238.7±1.4) Ma, 为有意义的成矿年龄。

东昆仑和鄂拉山地区发育相近的约237 Ma和约222 Ma的两个相对成矿峰期, 早期以矽卡岩型成矿为主, 而晚期以斑岩成矿为主。区域斑岩-矽卡岩系统型矿床找矿潜力不可忽视。

东昆仑和鄂拉山三叠纪中晚期可能处于相同的俯冲后构造环境并具有相似的地球动力学过程,同受布青山—阿尼玛卿洋向北俯冲作用控制。260~230 Ma由俯冲向碰撞转换及其后, 发育与两个成矿峰期有关的岩浆活动, 前者可能与俯冲碰撞转换期的板块断离有关, 后者与后碰撞拆沉背景有关。鄂拉山应是东昆仑的一部分。

Acknowledgements:

This study was supported by China Geological Survey (No. 1212011220899).

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Re-Os Dating of Molybenite from the Maoniugou Cu-Au Ore Deposit in the Northern Part of the Ngola Mountain, Qinghai Province, and Its Geological Significance

CHEN Yong-fu, ZHANG Dong, LU Ying-chuan, LIU Peng, WANG Xiao-jun, FU Yang, LI Wen-liang, GUO Xiao-dong
Institute of Gold Geology, Chinese Armed Police Force, Langfang, Hebei 065000

Abstract:The Ngola Mountain lies at the conjunction between West Qinling and East Kunlun in the west of Central Orogenic Belt. Owing to its low research level, some problems concerned, such as the regional metallogenesis, geological setting and geodynamic process in Indosinian period, remain unclear. In this study, the authors used the method of temporal and spatial distribution characteristics of specific type deposits to deduce the geological background and geodynamic process. Based on a detailed study of geological features and ore-forming geochronology of the Maoniugou copper-gold deposit in northern Ngola Mountain, and combined with the traditional tectonic study and diagenetic evidence, the authors tried to explore the regional ore-forming geological background, the geodynamic process and the assignment of the Ngola Mountain through a comparison with the typical porphyry-skarn deposits in East Kunlun. The results show that the Maoniugou deposit is a small copper-gold skarn deposit closely related to Muleer granodiorite. Mineralizations associated with Cu-Au mineralization are mainly silicification, sericitization, chalcopyritization and pyritization. Ore minerals arebook=70,ebook=73mainly composed of chalcopyrite, pyrite and molybdenite. The authors measured Re-Os isotopes of representative molybdenite-bearing samples from the main orebody, and the six yielded model ages range from (237±3.3) Ma to (240.7±3.3) Ma with a well-constrained weighted average model age of (238.7±1.4) Ma. Based on these new age data and ages of regional porphyry-skarn ore deposits, the authors have reached the conclusion that the Ngola Mountain and East Kunlun had similar post-subduction settings and geodynamic processes at least in middle and late Triassic, and they belonged to the continental margin settings with the north subduction of Buqing-Anymaqin Mountain. The East Kunlun Triassic mineralization may have two peak periods: Fe-Cu skarn mineralization at about 237 Ma and Cu-Au porphyry mineralization at about 222 Ma, related respectively to break-off of the subducted slab and lithospheric delamination after crustal thickening due to collision between continental plates in Triassic.

Key words:molybdenite Re-Os age; Maoniugou; Ngola Mountain; East Kunlun

作者简介:第一 陈永福, 男, 1980年生。博士, 高级工程师。主要从事黄金地质勘查。E-mail: cyf04@mails.ucas.ac.cn。

中图分类号:P618.4; P597.2

文献标志码:A

doi:10.3975/cagsb.2016.01.07