黄沙坪矽卡岩型和脉状铅锌矿成矿环境及其对深部找矿的指示

Metallogenic environment of skarn-type and vein-type Pb-Zn ore bodies in Huangshaping deposit and its implications of deep deposit exploration

黄沙坪多金属矿床是湖南最重要的铅锌矿床之一,矿区内岩浆活动和构造运动复杂,成矿元素多样,矿化类型丰富,前人主要针对高温矿化阶段W-Sn成矿过程做了大量的研究,对Pb-Zn矿化过程研究较少,特别是对矽卡岩型和脉状矿体之间的相关型和差异性关注度较低。本文通过电子探针(EMPA)和激光剥蚀电感耦合等离子体质谱仪(LA-ICP-MS)分别对黄沙坪多金属矿床中的闪锌矿主微量元素和黄铁矿中的微量元素进行测试。结果表明:两种矿体中闪锌矿的Fe含量均>10%,属于铁闪锌矿,且矽卡岩矿体中闪锌矿的Fe含量更多。根据计算,矽卡岩矿体中闪锌矿的结晶温度为388~428℃(平均为408℃),而脉状矿体中闪锌矿的结晶温度为350~393℃(平均为371℃),属于中高温成矿体系;闪锌矿和黄铁矿的微量元素特征指示两种类型矿体均形成于低硫逸度的成矿环境,且脉状矿体的氧逸度略高。闪锌矿中In、Ga和黄铁矿中Co、Ni的含量特征显示,两种成矿类型物质来源主要是岩浆。综合矿区地质特征,认为黄沙坪多金属矿床属于燕山期与花岗岩有关的中高温岩浆热液矽卡岩矿床,其深部仍有较大的铅锌矿找矿空间。

The Huangshaping polymetallic deposit is one of the most important Pb-Zn deposits in Hunan Province,China.The magma and tectonic in this deposit are complex,with diverse mineralization elements and rich mineralization types.The W-Sn mineralization at the high temperature mineralization stage has been studied by a lot of previous researchers,while the Pb-Zn mineralization process,especially the correlation and difference between the skarn type and vein type ore bodies are less concerned.This work mainly analyzed the major and trace elements of sphalerite,trace elements of pyrite by EPMA and LA-ICP-MS.The results show that Fe contents of sphalerite in the two ore bodies are upper to10%,which belong to marmatite,and the Fe content of sphalerite in skarn ore bodies is higher than that in vein type ore bodies.It is calculated that the crystallization temperature of sphalerite in the skarn ore body is 388−428℃(the average value is 408℃),while the crystallization temperature of vein-like ore body is 350−393℃(the average value is 371℃),which belongs to medium-high temperature mineralization system.According to the trace element characteristics of sphalerite and pyrite,both types of ore bodies are formed in low-sulfur fugacity ore-forming environments,and the vein type ore bodies have slightly higher oxygen fugacity.The contents of In and Ga elements in sphalerite and Co and Ni elements in pyrite show that the mineralization source of the two types of ore bodies is mainly granite porphyry.Based on the geological characteristics of the deposit area,it is believed that the Huangshaping polymetallic deposit is a medium-high temperature magmatic-hydrothermal skarn deposit related to granites.There is still large prospecting space for lead-zinc ore body in the deep part of Huangshaping polymetallic deposit.