The Gaoligong orogen is the eastern boundary of the Tengchong block,and the Cenozoic granites outcropped in this orogen are related to the collision of the Indian and Eurasian plates.Here we report a new chronological and petrochemical study for the Eocene granites from the Gaoligong orogen in eastern Tengchong block.The zircon LA-ICP-MS U-Pb dating from three granites yielded weighted mean 206Pb/238U ages ranging from 47Ma to 43Ma.The zircon εHf(t) values show a range of-8.4 ～-0.8 with tDMC of 1317 ～ 1730Ma for Jiujinliang and Dazhongshan granites,and-7.0 ～ + 5.7 with tDMC of 907 ～ 1531Ma for Dongjiayuan granite.These rocks are characteristized by high-K calc-alkaline,high SiO2,K2O and low CaO,P2O5 contents,metaluminous to peraluminous,enrichment of LILE and LREE,with strongly negative Ba,Nb,Sr,P and Ti anomalies,indicating a collision affinity.These features shows that the granitic magmas for the Jiujinliang and Dazhongshan granites are derived from the partial melting of the MidNeoproterozoic metasedimentary rocks,while the Dongjiayuan granite was considered to be derived from melting of metaigneous and metasedimentary rocks.According to petrological and geochemical characteristics of these granites together with the tectonic diagram analysis,all of these granites are formed within a collision-related tectonic setting.The Eocene magmatism is the response to the collision of the Indian and Tengchong blocks.%高黎贡构造带构成腾冲地块的东部边界,其内出露的新生代花岗岩与印度板块和欧亚大陆的碰撞有关.本文通过岩石学、岩石地球化学、锆石LA-ICP-MS U-Pb定年和Lu-Hf同位素示踪对腾冲地块东缘——高黎贡构造带内3个始新世花岗岩体进行了研究,结果表明其形成时代为43 ～ 47 Ma.岩石具有高钾钙碱性、高硅、富钾、低钙、低磷,A/CNK值介于1.05 ～1.14之间,LREE富集以及Eu、Sr、Ba、Nb、P和Ti强烈负异常等特征.锆石Lu-Hf同位素测试结果表明九斤粮岩体和大中山岩体的锆石εHf(t)值特征相近,分布于-8.4～-0.8之间,对应的tDMC值为1317 ～ 1730Ma;董家园岩体的锆石εHf(t)值则分布于球粒陨石线两侧(-7.0～ +5.7),对应的tDMC值为907 ～ 1531Ma.这些特征说明九斤粮岩体和大中山花岗岩岩浆来源于中-新元古代变沉积岩部分熔融的产物,董家园花岗岩岩浆来源于中-新元古代变基性岩和变沉积岩的部分熔融.岩石地球化学特征和构造环境判别图解显示该期花岗岩形成于同碰撞的构造环境,是腾冲地块内晚白垩世和古新世岩浆活动的延续,是对印度板块与欧亚大陆碰撞的响应.
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