特提斯喜马拉雅带内95Ma基性岩浆活动——印度板块北缘晚白垩世伸展作用  

The 95Ma mafic magmatism in the Tethyan Himalaya:Late Cretaceous extension and rifting in the northern margin of the Indian plate

作　　者：王亚莹[1] 曾令森[1,2] 邸英龙 赵令浩 董汉文[1,2] 唐灼[1] 费镕泽 宋昱霆 WANG YaYing;ZENG LingSen;DI YingLong;ZHAO LingHao;DONG HanWen;TANG Zhuo;FEI RongZe;SONG YuTing(Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;SinoProbe Laboratory,Chinese Academy of Geological Sciences,Beijing 100094,China;The Seventh Geological Brigade of Hubei Geological Bureau,Yichang 443100,China;National Research Center for Geoanalysis,Beijing 100037,China)

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]自然资源部深地科学与探测技术实验室,北京100094 [3]湖北省地质局第七地质大队,宜昌443100 [4]国家地质实验测试中心,北京100037

出　　处：《岩石学报》2024年第12期3699-3716,共18页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(42102059、92055202、U2344219、42172261);中国地质调查局地质调查项目(DD20221817、DD20221630);中国地质科学院地质研究所基本科研业务费项目(J2204)联合资助。

摘　　要：自从晚侏罗世由东冈瓦纳超大陆裂解以来,印度板块经历了长距离的北向漂移直至与亚洲大陆南缘碰撞。作为印度板块的最北缘,喜马拉雅地区在随着印度板块漂移过程中经历的构造事件和动力学机制至今仍未明确。本文报道了特提斯喜马拉雅带中部拉轨岗日和东部打隆地区出露的两处辉绿岩体,它们均具有~95Ma的锆石U-Pb年龄,共同揭示出喜马拉雅中、东部地区晚白垩世统一的一期伸展事件。系统的岩石成因分析表明,它们均属于板内拉斑系列,然而东部和中部样品的地球化学组成具有如下差异:(1)东部打隆岩体具有高Ti含量(TiO_(2)>3.5%),微量元素呈OIB型特征,与卡达地区同时期玄武岩类似,为未受地壳混染的软流圈物质熔融形成;(2)中部拉轨岗日地区基性岩具有低Ti含量(TiO_(2)<2.0%),稀土元素类似MORB型,微量元素特征指示其源区为富集岩石圈地幔组分。根据PRIMACALC2软件恢复的原始岩浆组成显示东部样品熔融源区较浅,而中部样品熔融源区较深。我们认为在~95Ma印度大陆北缘伸展减薄过程中,东部薄弱岩石圈伸展引起了软流圈物质的直接熔融,而中部由于岩石圈较厚,在大陆伸展过程中软流圈物质上涌加热岩石圈底部,引起上覆富集岩石圈物质熔融。结合冈底斯岛弧带晚白垩世岩浆峰期指示的新特提斯洋俯冲异常事件,特提斯喜马拉雅带约95~90Ma基性岩浆和大陆伸展可能由俯冲的特提斯板块回撤产生的对印度北缘增强的板片拉力引起。这期被动大陆边缘伸展事件与印度板块~90Ma加速北移耦合,与前人提出的地幔柱推动等机制不同,本文数据表明俯冲板块拉力可能在印度板块北移中起到重要作用。Since separating from the Eastern Gondwana supercontinent in the Late Jurassic,the Indian plate drifted northward long-distance until it collided with the southern margin of Asia.The tectonic evolution of the Indian plate and its dynamic mechanisms during this long drift are still debated.In this paper,we report two diabase plutons located in the middle and the east parts of the Tethyan Himalaya,the northernmost part of the Indian plate.They both have zircon U-Pb ages of~95Ma,suggesting one Late Cretaceous extension event in the northern margin of the Indian plate.They belong to the tholeiite series with intraplate affinity,but their contrasting geochemical features from east to central indicate different mantle sources.In the east,the Dalong diabases have high Ti content(TiO 2>3.5%)and OIB-like trace element characteristics,similar to the~92Ma basalts in the Kada area.This feature suggests that they are formed by partial melting of asthenosphere material without crustal contamination.In the central,mafic rocks in the Lhagoi Kangri area have low Ti content(TiO 2<2.0%)and MORB-like REE features,and the characteristics of trace elements indicate that their source area is the enriched lithospheric mantle.The primary magma compositions recovered by the PRIMACALC2 software show that source melting depth of the eastern samples is shallower than that of the central samples.We propose that during the rifting process in the northern margin of the Indian plate at~95Ma,the extension of the thin east lithosphere caused partial melting of asthenosphere material;while in the central,the melting of asthenosphere material was prevented due to the thick lithosphere.Thus,the upwelling asthenosphere heated the bottom of the lithosphere and caused the melting of the overlying enriched lithosphere mantle materials during this continental rifting process.Considering the Late Cretaceous magmatic peak in the Gangdese arc belt,the ca.95~90Ma mafic magmatism and continental extension in the Tethyan Himalaya should have been caused by the

关 键 词：特提斯喜马拉雅 被动大陆边缘岩浆作用 晚白垩世 印度板块 特提斯动力学 

分 类 号：P542[天文地球—构造地质学] P588.124[天文地球—地质学] P597.3