云南易门狮子山铜矿床黄铜矿-斑铜矿Re-Os定年与S同位素组成

易门狮子山铜矿床是康滇地区元古宙昆阳裂谷中的典型铜矿床之一,受狮子山背斜北西翼次级构造控制明显,矿石以脉状、浸染状、块状为主,少量呈层纹状。为厘定构造改造成矿时代,开展与石英、方解石脉共生的富黄铜矿、斑铜矿脉岩相学研究,挑选黄铜矿、斑铜矿单矿物,进行高精度的Re-Os同位素定年测试,获得了三组模式年龄,从早到晚依次为:(1)1749±18-1761±18Ma、(2)1358±14-1549±16Ma、(3)449.4±4.7Ma,其中获得第二组模式年龄的样品等时线年龄为1538±130Ma。据Re-Os同位素、硫同位素组成分析,落雪组中铜矿的成矿物质主要来源于地壳,部分来源于深源。结合矿区和区域构造-岩浆事件分析,认为矿区在古元古代发生了小规模岩浆热液成矿事件,形成了少量铜的硫化物;中元古代为矿区的主要成矿时期,该期成矿事件可能与刺穿构造形成时发生强烈的构造热事件作用有关;在早古生代早期也发生过小规模成矿事件,可能与加里东运动在该区的响应有关。

Re- Os dating and S isotopic composition of chalcopyrite and bornite in the Shizishan copper deposit, Yimen, Yunnan Province

The Shizishan copper deposit in Yimen is one of the typical copper deposit in the Proterozoic Kunyang rift of the Kangdian area. Orebodies in the deposit are obviously controlled by the secondary structure of the northwest wing of the Shizishan anticline. The ore textures mainly include vein, disseminated, massive and a small amount of lamination.In order to determine the age of tectono-hydrothermal mineralization, the porphyrical chalcopyrite and bornite coexisting with quartz and calcite vein are selected for petrographic study, and chalcopyrite and bornite for high-precision Re-Os dating. Three groups of model ages were obtained from early to late:(1) 1749±18-1761±18 Ma;(2)1358±14-1549±16 Ma;(3) 449.4±4.7 Ma. An isochron age of 1538±130 Ma was obtained for the samples in second model ages range. According to the analysis of sulfur isotopic compositions, the ore-forming materials of the copper deposits hosted in the Luoxue Formation mainly come from the crust, and some from the deep earth. Combined with the regional tectonic magmatic events, it is considered that a small-scale magmatic hydrothermal metallogenic event occurred in Paleoproterozoic, forming a small amount of copper sulfides. The Mesoproterozoic is the main metallogenic period of the mining area, which may be related to the strong tectonic thermal event of the piercing structure. The small-scale metallogenic event also occurred in early Paleozoic, which may be related to the response of Caledonian movement in this area.