三江特提斯兰坪盆地构造-流体-成矿系统  

Tectonic-fluid-mineral system in the Lanping basin,Sanjiang Tethys

作　　者：王长明[1] 陈晶源[1] 杨立飞[1] 张端[1] 杜斌[1] 石康兴 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083

出　　处：《岩石学报》2017年第7期1957-1977,共21页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划(2015CB452603;2009CB421008);高等学校学科创新引智计划(B07011);中央高校基本科研业务费(2652016341)联合资助

摘　　要：西南三江中段兰坪地区经历了复杂的碰撞造山过程,导致成矿时间长、强度大、作用多样,复合叠加成矿突出;碰撞造山时空演化格架和成矿作用已有深入探索,而叠加成矿作用及其对碰撞造山过程的响应,构造控矿样式,及金属富集机理尚需研究。本文以碰撞造山过程与成矿系统研究为基础,选取金顶和金满等矿床为重点解剖对象,以盆地卤水和热液铅锌铜银成矿作用为主线,利用锆石LA-ICP-MS U-Pb和流体包裹体测试分析手段,解析兰坪盆地构造-流体-成矿系统。利用锆石U-Pb同位素定年获得兰坪盆地西侧片麻质花岗岩和二长花岗岩的上交点年龄和加权平均年龄为1067±20Ma和206±1Ma,分别代表了基底岩石前寒武时期变质事件的年龄,以及昌宁-孟连古特提斯洋后碰撞造山事件的年龄。在此基础上,构建了兰坪盆地的前寒武盆地基底形成、中二叠世-中三叠世前陆盆地、晚三叠世裂谷盆地、侏罗纪-白垩纪坳陷盆地、古新世-早渐新世前陆盆地和晚渐新世-中新世走滑拉分盆地等复杂的转化过程。三江特提斯兰坪盆地发育3个与碰撞造山盆地有关的Pb-ZnCu-Ag-Au-Sb-Hg成矿系统:(1)中低温热液脉型Cu-Ag多金属成矿系统,以金满-连城铜钼矿床为代表。成矿铜和铅锌矿化两期叠加,集中于早始新世(56~46Ma)和渐新世-中新世(32~21Ma)。成矿流体盐度变化于0.88%~20.51%NaC leqv之间,成矿温度较低,通常在210~270℃,显示以低温高盐度的盆地卤水为主的特征,可能受到来自富CO2的变质流体影响;(2)浅成低温热液Sb-Au-Hg-As多金属成矿系统,以笔架山锑矿床为代表。成矿时间集中于中-晚始新世。成矿流体盐度<6.0%NaC leqv,成矿温度较低,通常在145~200℃,显示以大气降水为主的特征;(3)密西西比河谷型Pb-Zn多金属成矿系统,以金顶超大型铅锌矿床为代表。成矿时间集中于32~21Ma之间。成矿流体盐度变化于1.6%~18%NaC leThe Lanping area in the middle part of western Sanjiang Tethys experienced a complex collisional process,resulting in prolonged and extensive metal depositions from diverse types of mineralization and the consequent superimposed metallogenesis. Despite extensive research carried out on spatio-temporal framework of collisional orogeny and the related mineralization,the superimposed mineralization,fault-controlling types,and metal enrichment is still not well addressed. This paper,we will aim at the collisional orogeny and superimposed mineralization such as the Jinding and Jinman deposits,focusing on the basin brines and hydrothermal fluids,analyzing tectonic-fluid-mineral system by LA-ICP-MS zircon U-Pb and fluid inclusion. Zircon U-Pb dating of the gneissic granite and monzogranite from the western margin of Lanping basin yield the upper intercept and weighted mean ages of 1067 ± 20 Ma and 206 ± 1Ma,representing the metamorphic age from the Precambrian basement and post-collisional age of Changning-Menglian Tethys Ocean,respectively. The tectonic history of the Lanping basin is a complex process,involving the earliest formation of basement,the Middle Permian-Middle Triassic foreland-basin,the Late Triassic post-collision extension and rift basin,JurassicCretaceous depression-basin,Paleocene-Early Oligocene foreland-basin,and Late Oligocene-Miocene strike-slip and pull-apart basin.There exist three types of Pb-Zn-Cu-Ag-Au-Sb-Hg mineral systems related to the Lanping orogenic basin：（ 1） Mesothermal vein type Cu-Ag mineral system,as examples of Jinman and Liancheng deposits. Paleocene-Early Eocene（ 56 - 46Ma） Cu mineralization were superimposed by Oligocene-Miocene（ 32 - 21Ma） Pb-Zn mineralization. Fluid inclusions have characterized by homogenization temperatures predominately of 210 - 270℃ and salinities of 0. 9% - 20. 5% NaC leqv,indicative of basinal brines as the source of oreforming fluids with contribution from a minor metamorphic fluids;（ 2） Epithermal Sb-Au-Hg-As mineral system,as an

关 键 词：成矿流体 构造控矿 成矿系统 大陆碰撞 兰坪盆地 三江特提斯 

分 类 号：P542[天文地球—构造地质学] P611[天文地球—地质学]