滇西北兰坪盆地金满脉状铜矿床绢云母^40Ar-^39Ar年龄对成矿时代的约束

处于印度大陆与亚洲大陆主碰撞带北东侧的兰坪盆地西缘的金满铜矿床，产于中生代陆相沉积砂岩、泥岩中，以其属新类型陆相喷流铜矿床而引起人们的关注。关于其成矿时代至今仍然存在争论。采用常规^40Ar/^39Ar阶段升温测年法对金满铜矿床主矿体旁侧的含铜热液蚀变矿物绢云母进行了测试，获得3组视平均年龄分别为88Ma、67Ma、37Ma。结合兰坪盆地区域地质成矿背景，认为金满铜矿成矿经历了早期67Ma的成矿作用和晚期37Ma的成矿叠加作用，后者代表了金满铜矿的主要形成年龄。金满铜矿床的2期成矿年龄可能是印～藏碰撞(古新世)和走滑～拉分(始新世)等重大地质构造事件在矿床中留下的同位素年龄信息．暗示着古新世时期的构造作用和始新世时期的构造-岩浆-成矿活动对兰坪盆地的作用。

Constraints of sericite 40Ar-39Ar ages on the metallogenic epoch of the Jinman vein copper deposit in the Lanping basin, northwestern Yunnan

Located tectonically on the western margin of the Lanping basin on the northeastern side of the main India-Asia collision zone, the Jinman vein copper deposit occurs in Mesozoic terrestrial sandstone and mudstone. It is a new type of copper deposit closely associated with continental exhalation. Its metallogenic epoch is now still in dispute. The copper-bearing hydrothermal alteration mineral sericite beside the principal orebody of the Jinman copper deposit was analyzed using the conventional 40Ar/39Ar stepwise heating dating method, and three 40Ar/39Ar apparent average ages, namely, 88, 67 and 37 Ma, were obtained. According to these ages, combined with the geological setting of ore deposition in the Lanping basin, the authors think that the formation of the Jinman copper deposit underwent mineralization at 67 Ma in the early stage and that at 37 Ma in the late stage, which were superimposed on each other, with the latter representing the main formation age of the Jinman copper deposit. The two mineralization ages of the Jinman copper deposit may be interpreted as the isotopic age information left by major tectonic events such as the India-Tibet collision (in the Paleocene) and strike-slip motion-pulling-apart (in the Eocene) in the ore deposit, implying the effects of the Paleocene tectonism and Eocene tectonomagmatic metallogenesis on the formation of the regional metallogenic zone in northwestern Yunnan.