川西锦屏山地区庙顶Cu-Au矿床地球化学特征与成矿机制探讨

Geochemical characteristics and metallogenic mechanism of Miaoding coppergold deposit in Jinpingshan area,western Sichuan Province

庙顶Cu-Au矿床是近年来在四川省冕宁县锦屏山地区新发现的中型铜金矿床,其位于扬子板块西缘NNE向锦屏山深大断裂与近SN向箐河-程海断裂交汇部位所夹的锐角区域内。文章在总结矿床地质特征的基础上,通过对矿床开展系统的C、H、O、S稳定同位素地球化学和流体包裹体的研究及成矿机制的探讨,初步认为庙顶铜金矿床的成矿流体应为岩浆热液来源,岩浆热液流体在运移过程中与围岩发生了一定程度的水岩反应,从而导致围岩玄武岩中的Au、Cu等成矿元素遭受淋滤而进入成矿流体,并在后期还有少量大气降水的加入。矿床的形成经历了高温到中温,最后到低温的演化过程,矿床成因类型属岩浆热液交代矿床。

The Miaoding deposit is a newly discovered copper-gold deposit in Jinpingshan area,Mianning county,Sichuan Province,located at acute angle district at the intersection between the NNE-trending Jinpingshan deepseated fault and the nearly SN-trending Jinghe-Chenghai fault on the western margin of the Yangtze Block.Based on detailed descriptions of geology of the Miaoding copper-gold deposit,this paper presents new C,H,O,and S stable isotope data along with the results of fluid inclusion studies,thus providing significant constraints on the origin of this deposit.These data indicate that the ore-forming fluid was probably a magmatic hydrothermal fluid which interacted with surrounding rocks to some extent during migration upward,leaching copper and gold from basalt into the ore-forming fluid;meanwhile there also existed a small amount of meteoric waters mixed with easier magmatic hydrothermal fluid at the later stage.The formation of the Miaoding deposit underwent the evolution process from high to medium,then to lower temperature,and it should be classified as a magmatic hydrothermal metasomatic deposit.