鲁西沂南金场夕卡岩型金铜矿床矿化时代与成矿流体研究  

Geochronology and ore-forming fluids in the Jinchang skarn gold-copper deposit,Yinan County,western Shandong Province

作　　者：胡芳芳[1] 王永[1] 范宏瑞[1] 郑小礼[2] 焦鹏[3] 

机构地区：[1]中国科学院地质与地球物理研究所矿产资源研究重点实验室,北京100029 [2]山东黄金集团有限公司,莱州264000 [3]山东黄金集团有限公司沂南金矿,沂南276300

出　　处：《岩石学报》2010年第5期1503-1511,共9页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40702016和40625010);国家重点基础研究发展规划项目(2006CB403503);全国危机矿山接替资源找矿项目(20089930)联合资助

摘　　要：沂南金场金铜矿床是鲁西地区夕卡岩型矿床的典型代表,矿床产于燕山期中酸性杂岩体与新太古界-寒武系地层的内外接触带附近,受岩浆岩、地层岩性以及构造的复合控制。由石榴子石和透辉石构成了早夕卡岩阶段矿物组合,而绿帘石+磁铁矿+镜铁矿±透闪石±阳起石±石英构成了晚夕卡岩-磁铁矿阶段矿物组合。利用早夕卡岩期黑云母以及晚夕卡岩期与碳酸盐伴生的黑云母样品进行单颗粒云母超低本底Rb-Sr等时线测试,分别获得了133±6Ma和128±2Ma年龄数据,它们与金场岩体的形成时间十分一致,说明该矿床与侵入体有密切的成因联系。流体包裹体研究表明,沂南金场金铜矿床各成矿阶段矿石中的流体包裹体主要有四种类型:含子矿物三相包裹体、富气包裹体、H2O-CO2包裹体和气液两相包裹体。从早夕卡岩阶段石榴石捕获的含子矿物包裹体中获得了很高的均一温度(530～570℃)和盐度(39.9%～60.4%)值,而晚夕卡岩阶段透辉石中含子矿物包裹体也显示较高的均一温度(451～580℃)和盐度(39.3%～60.7%)值。石英-硫化物阶段石英中包裹体均一温度分为两个区间,分别为320～450℃和108～291℃。石榴石内含子矿物包裹体,其子矿物可能为赤铁矿或磁铁矿,结合该矿床的矿石矿物组成特征,沂南金场为岩浆热液流体形成的氧化型夕卡岩金铜矿床。The Jinchang skarn Au-Cu deposit is located in Yinan County,western Shandong Province,China.It is hosted by Neoproterozoic to Cambrian sedimentary clastic sequences intercalated with limestone and marble units,intruded by adamellite and granitic porphyries.In the skarn facies,andradite and diopside comprise the main prograde skarn minerals,whereas epidote,chlorite,tremolite,actinolite and calcite are the principal retrograde skarn minerals.Single grain and low background Rb-Sr isochrone dating on biotite from prograde and retrograde skarn gives 133 ± 6Ma and 128 ± 2Ma,respectively.Four types of fluid inclusions were distinguished:(1) daughter mineral-bearing inclusions;(2) vapor-rich inclusions;(3) CO2-H2O inclusions,and(4) salt-saturated inclusions.Fluid inclusions associated with garnet(prograde skarn stage) display high homogenization temperatures and high salinities(530 ～570℃;39.9% ～60.4% NaCl equiv.).Fluid inclusions associated with epidote(retrograde skarn stage) also record higher homogenization temperatures and salinities(451 ～ 580℃;39.3% ～ 60.7% NaCl equiv.).Fluid inclusions associated with quartzsulfide stage show two intervals of homogenization,320 ～ 450℃ and 108 ～ 291℃.Some fluid inclusions in garnet contain hematite or magnetite daughters,suggesting an oxidizing magmatic environment.Overall,the Jinchang deposit is interpreted as an oxidized Au-Cu skarn based on the mineralogy and fluid inclusion characteristics.

关 键 词：成矿时代 流体包裹体 金场金铜矿 鲁西沂南 

分 类 号：P618.41[天文地球—矿床学]