滇西澜沧岩群时代归属、物源、古地理位置分析及意义

Analysis of age, provenance and paleogeographic location of Lancang Group in western Yunnan and its significance

为约束澜沧岩群时代、物源、古地理位置,本文进行碎屑锆石U-Pb年代学研究,并综合以往研究成果。澜沧岩群具统计意义最年轻组年龄为432±11 Ma、436±8.9 Ma、464±3.9 Ma、467±4.3 Ma、541±17 Ma、543±22 Ma、574±19 Ma,且D1643-2样品中有3颗泥盆纪锆石,为383 Ma、393 Ma、410 Ma。物源具亲冈瓦纳大陆和亲扬子大陆性质,碎屑锆石年龄谱峰值主要集中在两个阶段:泛非期(650~500 Ma)、晚格林威尔期(990~900 Ma),次级年龄组(2 500 Ma)。结果表明:澜沧岩群古地理位于冈瓦纳大陆北缘,腾冲—保山地块与思茅—印支地块之间,澜沧岩群时代为寒武—泥盆纪。古特提斯洋具继承性扩张。

In order to restrict the age, provenance and paleogeographic location of Lancang Group. In this paper, the U-Pb chronology of detrital zircon of Lancang Group is studied, combined with previous research results. The age of the youngest group of Lancang Group is 432±11 Ma, 436±8.9 Ma, 464±3.9 Ma, 467±4.3 Ma, 541±17 Ma, 543±22 Ma and 574±19 Ma, and there are three Devonian zircons in D1643-2 sample, 383 Ma, 393 Ma and 410 Ma. Its provenance comes from Gondwana and Yangtze continent. The peak of detrital zircon age spectrum is mainly concentrated in two stages: Pan-African period(650~500 Ma), Late Greenville Period(990~900 Ma) and secondary age group(2 500 Ma). Paleogeography is located in the northern margin of Gondwana continent, between Tengchong Baoshan block and Simao Indosinian block. The age of Lancang rock group is Cambrian Devonian. The ancient Tethys Ocean has inherited expansion.