东天山红石金矿床石英Rb-Sr同位素定年

摘要

The Hongshi gold deposit is located in the Qiugemingtashi-Huangshan ductile shear zone in the east Tianshan Mountains, which mainly controlled mineralization of the gold deposit. The gold mineralization age of the Hongshi gold deposit is 254 ~259Ma, analyzed by the sericite Ar-Ar dating technique by former researchers. This article aims to evaluate the feasibility of applying Rb-Sr dating technique to constrain the mineralization age of ductile shear zone type gold deposits, taking the Hongshi gold deposit as an example. The Rb-Sr dating is carried out on the fluid inclusions in quartz from the main mineralization stage, yielding an isochron age of 257 ± 4 Ma, the n(87Sr)/n(86Sr) value of 0. 70997 ±0. 00016. The isochron age of 257 ±4 Ma is highly consistent with the gold mineralization age of 254 ~ 259 Ma, indicating that Rb-Sr dating on fluid inclusions in quartz is adaptive to date the mineralization age of ductile shear zone type gold deposits. The mineralization age, location relationship and ore-forming material source between the Hongshi gold deposit and the Kanggur gold deposit are consistent with each other, indicating that they came from the same mineralization events. The time relationship of mineralization, ductile shearing action, dextral strike-slip and uplift cooling proves that the late dextral strike-slip and subsequent uplift cooling are the main reasons for the gold mineralization of the Hongshi gold deposit and the Kanggur gold deposit, which located in the same ductile shear zone. Further classification of ductile shear zone type gold deposits, the Hongshi gold deposit belongs to the type of earlier ductile shear deformation, latter brittle-ductile deformation and Mineralization superposition.%红石金矿床产于东天山秋格明塔什—黄山韧性剪切带中,其成矿作用主要受韧性剪切带控制.前人通过金矿石绢云母Ar-Ar法将该矿床主成矿时代限定在254 ～ 259Ma之间,本文从讨论Rb-Sr法测年在韧性剪切带型金矿成矿时代研究中的可行性角度出发,对红石金矿主成矿期形成的金矿石进行石英流体包裹体Rb-Sr法测年.Rb-Sr法测年得到等时线年龄为257±4Ma,n(87Sr)/n(86Sr)=0.70997±0.00016.该年龄位于红石金矿床254～259Ma的主成矿时代范围内,说明石英流体包裹体Rb-Sr测年对于解决韧性剪切带型金矿床成矿时代具有很好的可行性.另外,红石金矿床与同一剪切带内的康古尔金矿在成矿时代、空间位置关系以及成矿物质来源等方面均具有一致性,认为红石金矿与康古尔金矿属相同成矿事件的产物.通过分析红石金矿床成矿时代、韧性剪切带作用时代、右行走滑以及后期的冷却降温作用时代的关系,推测红石金矿床及其剪切带内所在的康古尔等金矿床成矿作用主因是秋格明塔什—黄山韧性剪切带内晚期的右行走滑剪切变形及走滑作用后的快速抬升和缓慢冷却作用.从韧性剪切带型金矿成矿类型来看,属于早期韧性剪切变形,后期脆—韧性变形、成矿作用叠加这一类型.