三江特提斯兰坪盆地构造-流体-成矿系统

发布时间：2018-04-26 11:49

  本文选题：成矿流体 + 构造控矿　； 参考：《岩石学报》2017年07期

【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 leqv之间,成矿温度较低,通常在80~190℃,显示以低温高盐度的盆地卤水为主的特征,可能有大气降水的贡献。文章最后解析了兰坪盆地构造-流体-成矿过程。研究对兰坪地区盆地卤水 岩浆热液型铅锌铜银成矿系统认识,为大陆碰撞过程及叠加成矿作用进一步研究提供理论支撑。
[Abstract]:The Lanping area in the middle part of the Sanjiang River in the southwest has experienced a complicated collision orogenic process, which has resulted in a long metallogenic time, a large strength, a variety of functions, and a combination of superimposed metallogenic outburst, and the temporal and spatial evolution framework of collision orogeny and the metallogenic process have been deeply explored. However, the superposition mineralization and its response to collision orogeny, structural ore-controlling style, and the mechanism of metal enrichment need to be studied. Based on the study of collision orogenic process and metallogenic system, the Jinding and Jinman deposits are selected as the main anatomical objects, the brine and hydrothermal lead-zinc-copper-silver mineralization in the basin are taken as the main line, and zircon LA-ICP-MS U-Pb and fluid inclusion testing and analysis methods are used. Analysis of tectonic-fluid-metallogenic system in Lanping Basin. Using zircon U-Pb isotopic dating, the upper intersection age and weighted mean age of granitic granites and monzomorphic granites on the west side of the Lanping basin are 1067 卤20Ma and 206 卤1 Ma, respectively, representing the ages of the Precambrian metamorphic events in the basement rocks. And the age of the post-collision orogenic events in Changning-Montaigne. On this basis, the Precambrian basin basement of Lanping basin, the Middle Permian-Middle Triassic Foreland basin, the late Triassic rift basin, the Jurassic-Cretaceous depression basin, the middle Permian-Middle Triassic Foreland basin, the late Triassic rift basin and the Jurassic Cretaceous depression basin were constructed. Paleocene-early Oligocene Foreland basin and late Oligocene-Miocene strike-slip pull-apart basin. In Sanjiang Tethys Lanping basin, there are three Pb-ZnCu-Ag-Au-Sb-Hg metallogenic systems related to collisional orogenic basins: (1) Cu-Ag polymetallic ore-forming systems of hydrothermal vein type, represented by the Jinmen-Liancheng Cu-Mo deposit. The mineralization of copper and lead-zinc is superimposed in the early Eocene (56 ~ 46 Ma) and Oligocene ~ Miocene ~ (32) ~ (21) Ma. The salinity of ore-forming fluid varies between 0.88%~20.51%NaC leqv and the ore-forming temperature is relatively low, usually at 210 ~ 270 鈩，

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