滇南新元古代的岩浆作用:来自瑶山群深变质岩SHRIMP锆石U-Pb年代学证据  

Neoproterozoic Magmatism in South Yunnan: Evidence from SHRIMP Zircon U-Pb Geochrological Results of High-Grade Metamorphic Rocks in the Yaoshan Group

作　　者：李宝龙[1] 季建清[2] 王丹丹[3] 马宗晋[2] 

机构地区：[1]中国地质科学院矿产资源研究所成矿作用与资源评价重点实验室,北京100037 [2]北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室,北京100871 [3]中国石化胜利油田地质科学研究院,山东东营257015

出　　处：《地质学报》2012年第10期1584-1591,共8页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号40872149)资助的成果

摘　　要：滇南瑶山—哀牢山地区出露一套呈NW—SE向狭长条带状展布的深变质岩系——下元古界瑶山群和哀牢山群,并认为存在前寒武纪的结晶基底。本文选取瑶山群眼球状花岗质糜棱岩和金平阿得博的片麻状花岗岩作为研究对象,进行SHRIMP锆石U-Pb定年。结合阴极发光图像,获得岩浆锆石的结晶年龄为828±6.2Ma(N=11,MSWD=1.8)和748～801Ma。同时,作者在墨江-元江剖面的哀牢山群黑云母花岗闪长质片麻岩中获得SHRIMP锆石核部U-Pb年龄为769～893Ma。研究揭示滇南的瑶山和哀牢山地区存在新元古代岩浆作用。瑶山群中古老残余锆石核部的984Ma年龄和哀牢山群中古老残余锆石核部年龄1104～1353Ma及2655Ma,表明该区存在中元古代或太古代的结晶基底,研究区很可能位于南华裂谷与康滇裂谷的交汇部位,新元古代的岩浆活动可能与Rodinia超大陆聚合——裂解过程有关。这为构筑Rodinia超大陆聚散过程和揭示华南大地构造演化史提供年代学方面证据。The Lower Proterozoic Yaoshan Group and Ailao Shan Group, composed of high-grade metamorphosed rocks, is a long, narrow belt striking NW-SE direction along the Red River fault, and are considered the Precambrian crystalline basement. In this paper, the SHRIMP zircon U-Pb dating have been conducted on the augen granitic mylonite （08HK-1） from the Yaoshan Group （Lianhuatan, Hekou County） and gneissic granite （08JP-5, Adebo,Jinping County）, and ages of two magmatic zircon groups are 828-6.2Ma （N=11, MSWD=1. 8） and 748-801Ma, respectively. In addition, the SHRIMP zircon U-Pb ages of 769 - 893Ma were obtained on biotite granodioritic gneiss from the Ailao Shan Group in Mojiang-Yuanjiang section. Combined with the crystal features, CL images and concordant of U-Pb age, 828 6.2Ma and 748-801Ma should present the crystal age. These ages suggested that there should have the Neoproterozoic magmatism in the study area. The SHRIMP zircon U-Pb dating on old core from sample 08HK-1 has the age of 984Ma, and the 08JP-5 sample has the old core zircon U-Pb age of 1104~ 1353Ma and even 2655Ma. The old core zircon age show that the Yaoshan area and southern part of Ailao Shan should be a Mesproterozoic or Archea basement. Based on these isotopic geochronological data above and regional geological tectonic evolution, the Yaoshan area and southern part of Ailao Shan should located in the cross region of the Nanhua Rift and the Kangdian Rift during breaking-up of the Rodinian Super- continent in the Neoproterozoic.

关 键 词：新元古代岩浆活动 SHRIMP锆石U-PB定年 瑶山群 滇南 

分 类 号：P597.3[天文地球—地球化学]