东川蓑衣坡硅质岩型铜矿床的地质地球化学特征及成因  

Geological-geochemical characteristics and genesis of Suoyipo silicalite type copper deposit

作　　者：李毅[1] 李赋屏[2] 何国朝[3] 

机构地区：[1]中南大学地学与环境工程学院,湖南长沙410083 [2]中国地质大学地学院,北京100083 [3]桂林矿产地质研究院,广西桂林541004

出　　处：《矿床地质》2005年第1期71-80,共10页Mineral Deposits

基　　金：原中国有色金属工业总公司生产矿山周边二轮找矿专项(中色铜矿字第1992023号文);科学技术部大型锡矿山接替资源探查技术与示范项目(2004BA615A_03)资助

摘　　要：蓑衣坡硅质岩型铜矿床产于元古宙裂谷带,矿化主岩为块状硅质岩和条纹(带)状硅质岩;块状硅质岩的SiO2含量为85.66%～96.74%,条纹(带)状硅质岩的SiO2含量为74.83%～87.52%;在TiO2_Al2O3和(K2O+Na2O)_Al2O3关系图上和(Co+Ni)_(As+Cu+Mo+Pb+V+Zn)关系图上,其成分投影点均落入与海底热水系统有关或热水沉积岩区的硅质岩区;蓑衣坡矿区矿石的稀土元素总量变化大,且显示轻稀土元素富集,叠加的成矿作用引起轻稀土元素含量升高;并具铈负异常、铕异常不明显的特点。矿石内矿物流体包裹体的均一温度为121～257℃,盐度w(NaCleq)为6.2%～8.3%,成矿流体属K+_Ca2+_SO2-4型和K+_Mg2+_SO2-4型。矿石的δ34S值为-14.8‰～+17.2‰,δ18O值为4.9‰,矿石中石英的δ18O值为12.4‰～16.3‰,位于热泉型石英的δ18O值变化区间(12.2‰～23.6‰)。矿石中黄铁矿内流体包裹体的δD值为-116.2‰,其δ18OH2O值为-5.7‰,接近美国黄石公园酸性热泉的δD值和δ18O值。含矿硅质岩的206Pb/204Pb比值为17.947～18.951,207Pb/204Pb比值为15.606～15.711,208Pb/204Pb比值为36.466～38.496。根据矿床地质地球化学特征,笔者认为,蓑衣坡硅质岩型铜矿床的成因类型属裂谷处于拉张裂陷阶段发生的喷流沉积作用形成的硅质岩型铜矿床。Hosted mainly in massive and banded siliceous rocks, the Suoyipo copper deposit is located in a Proterozoic rift. The SiO_2 contents of massive and banded siliceous rocks are 86.66%～ 96.74% and 74.83%～87.52%, respectively. In the TiO_2_Al_2O_3,(K_2O+Na_2O)_Al_2O_3 and (Co+Ni)_(As+Cu+Mo+Pb+V+Zn) diagram for siliceous rocks, the projection points of siliceous rocks in the Suoyipo copper deposit fall in the region related to the submarine hydrothermal system or hydrothermal sedimentary rock. ∑REE values of ores from the Suoyipo copper deposit vary remarkably and show enrichment of LREE and negative δCe anomalies. The homogeneous temperature and salinity of fluid inclusions in ores are in the range of 121°～ 257°C and 6.2%～8.3%〔w(NaCl_~eq )〕, respectively. The ore_forming fluids are of K+_Ca^2+ _SO^2- _4 and K+_Mg^2+ _SO^2- _4 types. The δ~34 S values of ores are-14.8‰～+17.2‰, whereas δD and δ~18 O_~H2O values of fluid inclusions in pyrite of ores are ^-116.2‰ and-5.7‰, respectively. δ~18 O values of quartz in ores are 12.4‰～16.3‰ and fall in the region of thermal spring type quartz. ~ ~206 Pb/~204 Pb, ~ ~207 Pb/~204 Pb and ~ ~208 Pb/~204 Pb ratios of ore_bearing siliceous rocks are 17.947～18.951, 15.606～15.711 and 36.466～38.496, respectively. According to the geological_geochemical characteristics, it is considered that the Suoyipo copper deposit is an exhalation_type copper deposit.

关 键 词：地质学 硅质岩型铜矿床 地质地球化学特征 蓑衣坡 

分 类 号：P618.41[天文地球—矿床学]