青藏高原碰撞造山带Pb-Zn-Ag-Cu矿床新类型：成矿基本特征与构造控矿模型  

Thrust-controlled,sediments-hosted Pb-Zn-Ag-Cu deposits in eastern and northern margins of Tibetan orogenic belt:Geological features and tectonic model

作　　者：侯增谦[1] 宋玉财[1] 李政[1] 王召林[1] 杨志明[1] 杨竹森[2] 刘英超[2] 田世洪[2] 何龙清[3] 陈开旭[3] 王富春 赵呈祥 薛万文 鲁海峰 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质科学院矿产资源研究所,北京100037 [3]中国地质调查局宜昌地质矿产研究所,湖北宜昌443003 [4]青海地质调查院,青海西宁810012

出　　处：《矿床地质》2008年第2期123-144,共22页Mineral Deposits

基　　金：国家基础研究计划973项目(2002CB412600);中国博士后科学基金(20070420418);国家科技支撑计划项目(2006BAB01A08)的资助

摘　　要：地处青藏高原东、北缘的兰坪、玉树及沱沱河地区，广泛发育包括金顶超大型矿床在内的大量新生代Pb、Zn、Cu多金属矿床。这些矿床均产于该高原东缘晚碰撞构造转换环境，主体赋存于第三纪前陆盆地内部，以沉积岩容矿，与岩浆活动无关，受逆冲推覆构造系统控制，显著区别于世界已知的各类以沉积岩容矿的贱金属矿床。研究表明，伴随印度-亚洲大陆碰撞造山而产生一系列逆冲断裂系，将前陆盆地侧缘的中生代地层切割成叠置的构造岩片，并推覆叠置于盆地沉积地层之上，形成单冲式或对冲式逆冲推覆构造系统，并控制了Pb-Zn-Ag-Cu矿床的形成与发育。根据逆冲推覆构造控矿式样和矿化特征，可以识别出4种矿床式：①产于逆冲推覆构造系统前锋带“构造穹隆＋岩性圈闭”内的金顶式Zn-Pb矿床；②受控于前锋带冲起构造的河西-三山式Pb-Zn-Ag-Cu矿床；③产于主逆冲断裂带派生-的次级断层或平移断层内的富隆厂式Ag-Cu或Cu矿床；④产于主逆冲断裂上盘灰岩层间破碎带内的东莫扎抓式Pb—Zn矿床。这些矿床的矿体多受不同级次的断裂控制，多孔砂岩、白云岩化灰岩及构造破碎带是有利矿化部位。多数矿体显示开放空间充填成矿特点，少数显示层控性，属后生成矿。金属矿物组合主要为低Fe闪锌矿＋方铅矿＋黄铁矿组合及低温Cu硫化物（黝铜矿系列为主）＋Ag硫化物（辉银矿、黝银矿、汞银矿）＋方铅矿±闪锌矿组合，脉石矿物组合主要为方解石＋重晶石±萤石±白云石±天青石，局部见沥青。成矿流体以盐水体系为主，盐度w（NaCleq）变化于1％～28．0％之间，成矿温度较低，通常在80～190℃，显示盆地卤水±大气降水的特点。逆冲推覆构造系统对矿床的控制主要体现在：其深部拆离滑脱带可能是流体流长距离侧向迁移的优选通道，主逆冲断裂Numberous of Pb-Zn-Ag-Cu ore deposits with significant economic values occur in Lanping basin and Yushu and Tuotuohe areas on the eastern and northern margins of Tibetan orogenic belt. Being hosted by sediments and having no obvious affinity to igneous ac- tivities, these deposits occur in continent-eontinent （Indo-Asian） collisional orogen and are controlled by thrust-nappe structures, thus obviously different from the well-known sediments-hosted base metal deposits in the world. They were formed in Tertiary foreland basins developed from Paleo-Tethyan rifting basins and Mesozoic depression basins. During mineralization, thrust-nappe structures juxtaposed Mesozoic strata over Tertiary strata through a series of parallel reverse/thrust faults in the basins. The deposits are strictly controlled by thrust-nappe structures. There exist four types of ore deposits： the Jinding-type deposits is formed in a thrusting-related dome structure combined with lithologic trap, the Hexi-Sanshan-type deposit is controlled by a pop up structure, the Fulongchang- type deposits are located in thrusting-related second-order faults within elastics, and the Dongmozhazhua-type deposits are hosted by second-order faults within limestone of the hanging-walls of major thrust faults. Their ore bodies are controlled by faults, where sandstone, dolomitized limestone and structural cracking zones are favorable loci of ore concentration. Ores were mainly derived from openspace filling and replacement, resembling epigenetic mineralization. Metal sulfides are present as low-Fe sphalerite ＋ galena ＋ pyrite or Cu-sulfides （tetrahedrite, bornite, chalcopyrite, chalcocite） ＋ Ag-bearingsulfides （argentite, freibergite, Ag-tetrahedrite） ＋ galena ＋ sphalerite. Gangue minerals are calcite ＋ fluorite ＋ barite ＋ dolomite ＋ celestine ＋ quartz, with rare bitumen. Fluid inclusions contain mainly salt aqueous solutions and locally and subordinately CO2 and hydrocarbons, with homogenization temperatures predominately of 80-190

关 键 词：地质学 Pb-Zn-Ag-Cu矿床 成矿特征 构造控矿模型 逆冲推覆构造系统 碰撞造山带 青藏高原 

分 类 号：P618.42[天文地球—矿床学] P618.43[天文地球—地质学]