滇东南老寨湾金矿床地质及同位素特征  

Characteristics of geology and isotopic geochemistry of the Laozhaiwan gold deposit in southeastern Yunnan Province China

作　　者：张静[1] 苏蔷薇 刘学飞[1] 和中华[2] 周云满[2] 李智[1] 赵凯[1] 

机构地区：[1]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 [2]云南黄金矿业集团股份有限公司,昆明650000

出　　处：《岩石学报》2014年第9期2657-2668,共12页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划项目(2009CB421006);国家自然科学基金项目(41030423);中央高校基本科研业务费专项资金(2652013017)联合资助

摘　　要：滇黔桂地区位于扬子板块西南缘,是我国重要的卡林型(微细浸染型)金矿集中区之一,区内弥勒-师宗、南盘江、富宁等深大断裂等控制了区域构造变形的发生和发展以及矿床的分布。该金三角内的老寨湾金矿床是目前在云南境内发现的唯一一处大型卡林型金矿床,已探明储量31.40t,具有矿石物质组成简单、金微细浸染分布、品位低、储量大的特点。该矿床目前划分为袁家坪矿段、椿树湾矿段和老鹰山矿段三个矿段,矿体的产出主要受不整合面和构造的双重控制。赋矿地层主要是加里东不整合面之上的下泥盆统坡松冲组的灰色、灰白色及褐黄色厚层块状细粒石英砂岩。最大的V3矿体分布在椿树湾矿段,后期辉绿岩脉沿着北西向的F7断层侵入,紧邻脉岩的矿体金品位明显增高。热液成矿过程可以划分为早、中、晚三个阶段,分别以石英-黄铁矿、石英-黄铁矿-绢云母、辉锑矿-方解石为典型矿物组合特征。论文对脉石矿物和流体包裹体开展了H-O同位素研究,对不同阶段的矿石矿物开展了S-Pb同位素研究。成矿流体的δDH2O值介于为-109‰^-93‰,而不同成矿阶段流体的δ18OH2O值略有变化,早阶段3个硅化的石英砂岩中的δ18OH2O值变化于7.8‰~9.2‰,中阶段流体的δ18O值=5.9‰~7.0‰,晚阶段δ18OH2O值为2.70‰,在投影图中位于不同的区域内,表明早阶段成矿热液来源于区域变质水和/或部分地层建造水,主成矿阶段岩浆流体的参与对局部的金矿化富集起到了重要作用,在成矿晚期有大气降水的参与。不同阶段、不同类型矿石或蚀变岩中硫化物δ34S值变化范围较大(2.096‰~32.289‰),早阶段蚀变岩中的2个黄铁矿样品的δ34S值为6.115‰和6.412‰;晚阶段的5个辉锑矿的δ34S值集中在2.096‰~4.691‰;而中阶段的不同矿石中黄铁矿的硫同位素变化较大;暗示了硫的多来源特征。但总体上矿石硫同位素The Dian-Qian-Gui area, located in the southwestern Yangtze craton, is one of the most important Carlin-type （disseminated） gold concentration areas in China. The regional Mile-Shizong fault, Nanpanjiang fault and Fu＇ ning fault etc. controlled the tectonic deformation and the deposit location. In the Dian-Qian-Gui gold triangle area, the Laozhaiwan gold deposit, owning 31.40t proven gold reserves at present, is the only large Carlin-type gold deposit discovered in Yunnan Province and possesses the features of simple ore minerals, disseminated gold, low gold grade and large tonnage. This gold deposit includes three ore sections, i. e. , the Yuanjiaping, Chunshuwan and Laoyingshan sections. The occurrence of ore bodies are mainly controlled by the unconformity surface and fold or fault structures in the ore district. The ore bodies are dominantly hosted in the Lower Devonian Posongchong Formation which is above the Caledonian unconformity and mainly consists of gray, brown and yellow thick fine sandstone. The largest orebody V3 occurs in the Chunshuwan section; and the gold grade obviously increases where the later diabase dyke invaded along the NW-trending F＇/ fault. The hydrothermal ore-forming process can be divided into early, middle and late three stages, which are characterized by the quartz-pyrite, quartz-pyrite-sericite and stibnite-calcite assemblages respectively. In this paper, we analyzed the H-O isotopic composition of the quartz and ore-forming fluid and S-Pb isotopic composition of the sulfides from different ores at Laozhaiwan. The 8DH2o values ranges between - 109%o and -93%0, while the 8TM OH2ovalues of the early, middle and late stage are 7. 8%0 ~ 9. 2%0, 5.9%0 ~ 7. 0%0 and 2. 70%0 respectively and plotted in the different origin area. The H-O isotopic study indicates that the ore-forming fluid in early stage was initially sourced from metamorphic devolatilization or partial formation water from the sedimentary strata, in middle stage the magmatic water played an important role for the s

关 键 词：同位素地球化学 矿床地质 卡林型矿床 老寨湾金矿床 滇黔桂地区 

分 类 号：P597.2[天文地球—地球化学] P818.51[天文地球—地质学]