滇西北保山核桃坪铅锌矿床成矿流体来源的同位素地球化学证据  

Isotope geochemical evidence for ore-forming fluid resources in Hetaoping Pb-Zn deposit,Baoshan,northwestern Yunnan

作　　者：薛传东[1] 韩润生[1] 杨海林[1] 杨志明[2] 田世洪[3] 刘勇强[1] 郝百武[1] 

机构地区：[1]昆明理工大学地球科学系,云南昆明650093 [2]中国地质科学院地质研究所,北京100037 [3]中国地质科学院矿产资源研究所,北京100037

出　　处：《矿床地质》2008年第2期243-252,共10页Mineral Deposits

基　　金：云南省自然科学基金项目(编号:2006D020M);国家自然科学基金项目(编号:40772067);国家基础研究计划“印度-亚洲大陆主碰撞带成矿作用”973项目综合课题(编号:2002CB412610)资助

摘　　要：滇西北核桃坪铅锌矿是保山地块内沿澜沧江断裂带发育的一个大型铅锌多金属矿床,矿体严格受近SN向的断裂带及层间破碎带控制,赋存于上寒武统核桃坪组和沙河厂组大理岩化灰岩及矽卡岩中。文章在分析矿床地质特征的基础上,通过对V1矿体的氢、氧、碳、硫、硅和铅同位素地球化学的示踪研究,探讨了成矿溶液中水、碳、硅、硫和铅的来源以及成矿流体的演化问题。研究表明,V1矿体中矿石的石英δ18O水值变化范围为6·1‰~7·6‰,平均为6·7‰,其δDV-SMOW值变化范围为-100‰^-108‰,平均为-104‰,说明成矿流体主要来自深部岩浆分异水,并在后期成矿作用过程中有地层建造水和大气降水的加入;矿石中方解石的δ13CV-PDB和δ18O水值分别为-6·6‰^-5·9‰和5·0‰~5·2‰,反映成矿流体的碳、氧具有深部流体与围岩发生交代反应的特征。硅、硫和铅同位素具深部岩浆或地幔来源的特点,但遭受后期壳源物质的混染。据此提出该矿床是与深部岩浆热液或幔源流体贯入有关的构造热液脉型矿床,其成矿作用受控于深部过程的驱动和控制,可为指导地质找矿提供依据。Located in the Baoshan massif along the Lancangjiang tectonic-metallogenic belt in northwestern Yunnan Province, the Hetaoping Pb-Zn deposit is one of the typical hydrothermal polymetallic orefields with many unique features. The stratified and vein-type Pb-Zn-polymetallic ore bodies exist in skarn and marbleized lime- stone of the Upper Cambrian strata, and are controlled exclusively by approximately SN-trending compresso-ten- sional interstratal faults and associated faults. Based on analyzing geological characteristics, this paper mainly studied geochemistry of hydrogen, oxygen, carbon, sulfur, silicon and lead isotopic compositions of No. V1 orebody in this ore deposit. The results show that oxygen isotopic compositions of quartz in ores range from 6.1‰ to 7.69‰ with an average of 6.7‰, and hydrogen isotopic compositions of quartz range from - 100‰ to - 108‰ with an average of - 104‰, suggesting that metallogenic fluids were mainly derived from deep concealed magmatic activities and mixed with meteoric water and shallow-seated water. Carbon and oxygen isotopic compositions of calcite range from - 6.6‰ to - 5.9‰ and 5.0‰ to 5.2‰, respectively, quite similar to the carbon and oxygen isotopic compositions of magmatic fluids mixed with crust-derived water, implying that hydrothermal ore-forming fluids were mainly derived from magmatism or mantle fluids. Silicon, sulfur and lead isotopes are also similar to those in magmatic hydrothermal solutions or mantle fluids, but might have been sub- jected to the mixture with crust-derived matter during the late ore-forming process. Therefore, all the evidence supports the argument that the deposit is a typical tectonic-skarn-bound hydrothermal deposit, whose sources were mainly derived from magmatic hydrothermal solution or mantle fluids through fault belts and were mixed with shallow-seated fluids during the ore-forming process. Ore-forming elements were carried by tectonic-fluids from magma or mantle to orogenic belts, and were most likely driven and

关 键 词：地球化学 岩浆热液 成矿流体 幔源流体 核桃坪铅锌矿床 滇西北 

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