广西大厂黑水沟矽卡岩型锌铜矿床符山石的地质意义

The geological significance of vesuvianite in the Heishuigou Zn-Cu deposit in the Dachang area,Guangxi Autonomous Region,China

广西大厂黑水沟锌铜矿床的发现是深部找矿工作取得的重大成果,该矿床的围岩蚀变以矽卡岩化为主,研究工作中发现了围岩中典型的矽卡岩矿物符山石,这对该矿床的形成及下一步的找矿工作具有重要的指示意义。符山石主要分布在退化蚀变阶段,属于含水矽卡岩产物,并与矿床的Zn-Cu矿化密切相关,可作为矿床矿化的找矿标志,利用原位LA-ICP-MS技术对符山石的主微量和稀土元素组成进行了分析。结果表明,区内符山石均富铝,并与区内矽卡岩及深部花岗岩富铝的特征一致;微量元素结果显示符山石中富集大量成矿元素,如Zn、Sn、Bi、W、Ga、Sr等,它们以类质同象的方式置换了晶格中的Mg^(2+)、Fe^(2+),推测在退化蚀变时期的成矿流体已富集大量的成矿元素,从而为后期的成矿作用提供了有利的环境。稀土元素研究发现,所有符山石均具有与深部隐伏花岗岩近似平行的稀土配分模式,暗示该矿床的形成与深处隐伏岩体具有紧密的联系。

The discovery of the Heishuigou Zn-Cu polymetallic deposit in the Dachang area,Guangxi Zhuang Autonomous Region is a crucial achievement of the deep ore prospecting.Skarnization is the major hydrothermal alteration of wall rocks in the deposit.Vesuvianite,a typical skarn mineral in the wall rock has been discovered during the research work.It has important indicative significances for revealing the formation of the Heishuigou deposit and for guiding the further mineral prospecting in the area.Vesuvianite was mainly formed in the degeneration alteration stage.As a water-bearing skarn mineral,it is closely related to the Zn-Cu mineralization of the deposit.It can be used as a indicator for prospecting the mineral resources in the deposit.In situ LA-ICP-MS technology was used to have analyzed major,trace and rare earth elements of the vesuvianite in this paper.The results show that all vesuvianites from our study area are rich in aluminum,with similar Al-enriched characteristics of skarn and granite in depth;They are enriched in ore-forming elements such as Zn,Sn,Bi,W,Ga,Sr and others which replaced the Mg^(2+)and Fe^(2+)in the crystal lattice of vesuvianite in the form of isomorphism.It is implied that a large amount of ore-forming elements,which were enriched in the ore-forming fluid during the degeneration and alteration period,provided a favorable condition for the mineralization in late stage.In addition,all vesuvianites and samples of the concealed granite intrusion in the Heishuigou deposit have consistently sub-parallel REE patterns,suggesting that the formation of this deposit is closely related to the concealed granite intrusion.