西天山吐拉苏盆地塔吾尔别克金矿床成因探讨:来自同位素年代学和稳定同位素证据  

Genesis of the Tawuerbieke gold deposit in the Tulasu basin,western Tianshan: Evidence from geochronology and stable isotopes

作　　者：彭义伟[1] 顾雪祥[2] 程文斌[1] 邹存海 米登江 牛春良 

机构地区：[1]成都理工大学地球科学学院,成都610059 [2]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [3]中国冶金地质总局新疆地质勘察院,乌鲁木齐830006 [4]伊犁正元矿业有限责任公司,伊犁835000

出　　处：《岩石学报》2016年第5期1361-1378,共18页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41572062;U1303292);国家科技支撑计划项目(2011BAB06B02-02);中央返还两权价款资金综合研究项目(Y15-1-LQ04)联合资助

摘　　要：塔吾尔别克金矿床是新疆西天山吐拉苏盆地浅成低温热液金矿集区中的重要金矿床之一,赋存于晚古生代的大哈拉军山组火山岩和花岗斑岩中。矿体多呈脉状-透镜状不连续产出,受近NS向和NNW向断裂及其交汇部位控制。本文对赋矿安山岩进行了LA-ICP-MS锆石U-Pb定年,获得其加权平均年龄为367.1±3.2Ma,表明其喷发时代为晚泥盆世,代表了晚古生代北天山洋向哈萨克斯坦-伊犁板块俯冲消减背景下的岩浆产物。含金石英的氢、氧同位素组成表明,塔吾尔别克金矿床的成矿流体主要来源于大气降水;矿石中热液黄铁矿的δ34S值介于0.6‰~4.7‰之间,铅同位素组成与赋矿岩浆岩相似,指示成矿物质具有壳幔混合特征且以幔源为主,并很可能来自幔源的大哈拉军山组火山岩及其同时同源的花岗斑岩。另外,本文测得穿插矿体和赋矿安山岩的闪长细晶岩脉的锆石LA-ICP-MS U-Pb年龄为315.2±3.5Ma,从而将塔吾尔别克金矿床的成矿时代限定在367~315Ma之间,推测矿床形成于晚泥盆世-早石炭世北天山洋向哈萨克斯坦-伊犁板块俯冲消减的陆缘弧环境中。综合矿床地质特征、稳定同位素组成和成矿时代,认为塔吾尔别克金矿床具有浅成低温热液型向斑岩型矿床过渡的性质。The Tawuerbieke gold deposit is one of the important gold deposits in the Tulasu basin,which is to be known as an epithermal gold ore cluster in Chinese western Tianshan. The orebodies are hosted by volcanic rocks of the Late Paleozoic Dahalajunshan Formation and granitic porphyries. The orebodies occur as discontinuous veins and lenses,which are controlled by the nearly NS-and NNW-trending faults and their intersections. LA-ICP-MS U-Pb dating on zircons in hosting andesite by this study gave weighted average age of 367. 1 ± 3. 2Ma,indicating that its eruption happened in the Late Devonian during the subduction on the North Tianshan Ocean under the Kazakhstan-Yili plate. The hydrogen and oxygen isotopes of fluid inclusions in auriferous quartz indicate that the ore-forming fluids were sourced from the meteoric water. The δ34S values of the hydrothermal pyrites in ores range from 0. 6‰ to4. 7‰,and the compositions of Pb isotopes are similar to those of hosting magmatic rocks,indicating that the ore-forming materials were derived from the mantle-derived volcanic rocks of the Dahalajunshan Formation and the contemporaneous granitic porphyries.Furthermore,LA-ICP-MS U-Pb dating on zircons in dioritic aplite dike crosscuting the orebody and hosting andesite gave weighted average age of 315. 2 ± 3. 5Ma,suggesting that the timing of the mineralization could be constrained between 367 and 315 Ma. It is further suggested that this deposit formed in a continental-arc setting when the North Tianshan ocean crust subducted southward beneath the Kazakhstan-Yili plate during the Late Devonian-Early Carboniferous. Combined evidence from the geological features,stable isotopic compositions and mineralization age of the Tawuerbieke gold deposit indicates that it has the transitional nature between epithermal and porphyry deposits.

关 键 词：稳定同位素 成矿时代 浅成低温热液金矿 斑岩型金矿床 塔吾尔别克金矿 新疆西天山 

分 类 号：P597.2[天文地球—地球化学]