河南省内乡县银洞沟银金多金属矿成矿年龄:热液锆石LA-MC-ICP-MS U-Pb测年

Metallogenic age of the Yindonggou silver-gold-polymetallic deposit in Neixiang,Henan Province:LA-MC-ICP-MS U-Pb dating of hydrothermal zircons

北秦岭构造带广泛发育与古生代洋壳俯冲和碰撞造山有关的岩浆活动以及与造山过程有关的变质作用,但古生代热液脉型矿床在北秦岭构造带少见报道。银洞沟银金多金属矿为北秦岭构造带东部的一处中型热液脉型矿床,本文通过对该矿床赋矿围岩和含矿石英脉中锆石开展LA-MC-ICP-MS U-Pb测年和锆石成因研究,确定了矿床的形成时代,并探讨了矿床的成矿动力学背景。结果表明赋矿围岩黑云母二长花岗岩的形成时代为431.4±2.1 Ma,含矿石英脉中锆石结晶年龄为419.4±5.9 Ma,石英脉中锆石的岩相学、锆石中矿物和流体包裹体及锆石微量元素研究表明419.4 Ma代表矿床的形成时代。结合前人的研究结果,确定银洞沟银金多金属矿为形成于晚志留世的造山型矿床,成矿作用与碰撞期后~420 Ma的变质作用密切相关,成矿流体来源于地层的变质脱水,成矿物质主要来源于秦岭岩群和二郎坪群。

Magmatic activities and metamorphism related to Paleozoic oceanic subduction and collisional orogeny have been widely developed in North Qinling tectonic belt,but the Paleozoic hydrothermal vein-type metal deposits are rarely reported in the North Qinling.The Yindonggou silver-gold-polymetallic deposit is a medium-size deposit in the eastern part of North Qinling.This paper presents the LA-MC-ICP-MS zircon U-Pb age of the ore bearing quartz veins and biotite monzogranite host rock to determine the formation age of the deposit and constrain the metallogenic dynamic setting.It indicated that the biotite monzogranite and ore-bearing quartz vein were emplaced at 431.4±2.1 Ma and 419.4±5.9 Ma,respectively.Based on the study of zircon petrography,mineral and fluid inclusions in zircon,and trace elements of zircon,we constrained that the metallogenic age of the deposit is 419.4 Ma.Considering previous research results,we proposed that the Yindonggou silver-gold-polymetallic deposit is an orogenic-type deposit.The mineralization is closely related to the post-collisional metamorphism process at about 420 Ma.The oreforming fluids were dominantly derived from the metamorphic dehydration of the strata,while the oreforming materials were mainly sourced from both the Qinling Group and the Erlangping Group.