喜马拉雅东构造结早中新世隆升:锆石和金红石U-Pb年龄约束  

Early Miocene uplift of the eastern Himalayan syntaxis:Constraints from U-Pb ages of zircon and rutile

作　　者：王冬兵 秦雅东 曾纪培 罗亮 唐渊 曾孝文 韩明明 WANG Dongbing;QIN Yadong;ZENG Jipei;LUO Liang;TANG Yuan;ZENG Xiaowen;HAN Mingming(Chengdu Center of China Geological Survey(Geosciences Innovation Center of Southwest China),Chengdu 610281,China)

机构地区：[1]中国地质调查局成都地质调查中心(西南地质科技创新中心),四川成都610281

出　　处：《沉积与特提斯地质》2024年第4期883-896,共14页Sedimentary Geology and Tethyan Geology

基　　金：中国地质调查局项目(DD20240026,DD20221811,DD20190053);国家自然科学基金项目(U2244226);第二次青藏高原综合科学考察研究项目(2019QZKK0702)。

摘　　要：对喜马拉雅东构造结地区岩石开展锆石和金红石U-Pb年代学研究,以揭示喜马拉雅东构造结早期隆升历史。两件角闪石岩的锆石U-Pb年龄分别为(34.0±0.2) Ma和(31.4±0.4) Ma,相同两件样品的金红石U-Pb年龄分别为(23.8±0.9) Ma和(21.8±0.5) Ma。夕卡岩化石榴石大理岩中的金红石包裹体(寄主矿物为石榴子石)U-Pb年龄为(19.5±0.7) Ma。角闪石岩中的锆石和金红石均为岩浆成因,而金红石包裹体为变质成因。研究认为锆石年龄代表岩浆结晶或岩体侵位时间,而岩浆成因和变质成因金红石的年龄代表结晶后的隆升冷却时间。综合分析表明,雅鲁藏布江环绕的喜马拉雅东构造结核心区在早中新世23~19 Ma发生了明显的隆升,上新世5~3 Ma以来隆升加速。此外,推断喜马拉雅东构造结与喜马拉雅东、西构造结之间的中间段,在雅鲁藏布江新特提斯洋闭合至早中新世期间具有一致的隆升历史。Zircon and rutile U-Pb chronology of rocks from the eastern Himalayan syntaxis(EHS)were carried out to reveal the early uplift history of the EHS.The zircon U-Pb ages of two hornblendite samples are(34.0±0.2)Ma and(31.4±0.4)Ma,respectively.The rutile U-Pb ages are(23.8±0.9)Ma and(21.8±0.5)Ma,respectively.The rutile inclusions in the skarn garnet marble(with garnet as the host mineral)yield a U-Pb age of(19.5±0.7)Ma.Both zircon and rutile in the hornblendite are of magmatic origin,while the rutile inclusions are of metamorphic origin.We interpret the zircon age to represent the time of magma crystallization.While the ages of magmatic and metamorphic rutile represent the time of uplift and cooling after intrusion and crystallization.Comprehensive analyses show that the core of the EHS,surrounded by the Yarlung Tsangpo River,underwent significant uplift in the Early Miocene from 23 Ma to 19 Ma,and the uplift has accelerated since the Pliocene,from 5 Ma to 3 Ma.In addition,it is inferred that the EHS and the central Himalaya share a concurrent uplift history during the closure of Neotethys Ocean and the Early Miocene.

关 键 词：喜马拉雅东构造结 隆升 锆石 金红石 U-PB定年 

分 类 号：P597.3[天文地球—地球化学] P542[天文地球—地质学]