澜沧江构造带南段变质岩系锆石U-Pb年代学及构造涵义  

Zircon SHRIMP U-Pb geochronology and it tectonic implication of the metamorphic rocks in southern Lancang River tectonic zone West Yunnan Province

作　　者：王丹丹[1,2] 李宝龙[3] 季建清[4] 刘昱恒[5] 

机构地区：[1]中国地质大学能源学院,北京100083 [2]中国地质调查局油气资源调查中心,北京100029 [3]中国地质科学院矿产资源研究所、成矿作用与资源评价国土资源部重点实验室,北京100037 [4]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 [5]中国地质大学地球科学与资源学院,北京100083

出　　处：《岩石学报》2014年第9期2725-2738,共14页Acta Petrologica Sinica

基　　金：国家自然科学重点基金项目(40930419);中国地质调查局地质调查项目(12120114034301)联合资助

摘　　要：澜沧江构造带南段的古老变质岩系因临沧花岗岩基的大面积出露而呈零星分散状出露,该地区是否存在前寒武纪结晶基底和变质岩系的精确时代以及澜沧江构造带变质岩系的变质时限等问题还不是很清楚。本文以变质岩系为研究对象,挑选出锆石颗粒进行U-Pb SHRIMP定年,获得锆石核部U-Pb年龄是1802Ma、1404Ma、1092Ma、906~961Ma、812Ma和727~623Ma,时代为古元古代、中元古代和新元古代,揭示研究区存在前寒武纪的结晶基底,三叠纪（~230Ma）发育区域性岩浆作用事件,破坏改造了其结晶基底;昌宁-耈街剖面近澜沧江岸边花岗质片麻岩的锆石U-Pb谐和年龄为73.9±1.8Ma（MSWD=1.3,N=6）,记录澜沧江构造带变质岩经历了晚白垩世变质事件。综合研究认为澜沧江构造带南段存在区域性前寒武纪结晶基底,构造带中昌宁段之变质岩系的变质时间为晚白垩世（85~74Ma）,并一直持续到36Ma,约32Ma之后构造带发生走滑运动,变质事件明显早于走滑运动事件。The metamorphic rock series located in the southern Lancang River tectonic zone was distributed as sporadic scattered due to large area of the Lincang granite batholiths outcrops. In the study area, several scientific problems are still not very clear such as the Precambrian crystalline basement exists or not, the age of the ancient metamorphic rocks, the metamorphic time of metamorphic rocks in the Lancang River tectonic zone, and so on. In this paper, the metamorphic rocks were taken as the study objects and yielded the U-Pb ages of 1802Ma, 1404Ma, 1092Ma, 1054Ma, 906 -961Ma, 812Ma and 727 ~ 623Ma using the zircon U-Pb SHRIMP dating method. These ages belong to Early Proterozoic, Mesoproterozoic and Neoproterozoic era and also reveal the existence of Precambrian crystalline basement in the study area, and the Precambrian crystalline basement was destroyed or transformed by a period regional Triassic magmatic event （ ~ 230Ma）. The granitic gneiss of Changning-Goujie section cross the Lancang River yielded the zircon U-Pb SHRIMP concordia age of 73.9 ~ 1.8Ma （MSWD = 1.3, N = 6）, which was the record of Late Cretaceous metamorphic event in the Lancang River tectonic zone. Based on this study and combined with the other research data, it is suggested that the southern Lancang River area had the Precambrian crystalline basement existence and the metamorphic time of the Lancang River tectonic zone began in Late Cretaceous （85 ~ 74Ma）. This metamorphic event probably continued until 36Ma, and the strike-slip movements started from ~ 32Ma. So the metamorphic structural event was earlier than the strike-slip geological event in the Lancang River tectonic zone.

关 键 词：变质岩系 锆石U-PB年代学 前寒武纪结晶基底 晚白垩世 澜沧江构造带南段 

分 类 号：P597.3[天文地球—地球化学]