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The significance of Upper Jurassic felsic volcanic rocks within the incipient, intraoceanic Dras Arc, Ladakh, NW Himalaya
Gondwana Research ( IF 6.1 ) Pub Date : 2021-02-01 , DOI: 10.1016/j.gr.2020.11.007
Jessica M.J. Walsh , Solomon Buckman , Allen P. Nutman , Renjie Zhou

Abstract The Dras Arc is an island arc terrane located along the Indus Suture within the Ladakh Himalaya. To the north it is juxtaposed against the Eurasian Ladakh Batholith and to the south it is thrust over the Lamayuru Complex and Indian passive margin. Establishing the timing of inception and final collision of the Dras Arc is imperative to reconstructions of the Neotethyan Ocean and timing of arc-continent collisions, prior to the terminal India-Asia continental collision. We describe and date felsic tuffs and adakitic felsic volcanic rock interbedded within the dominantly basaltic-andesitic Dras volcanic complex. These felsic volcanic units yield Upper Jurassic zircon U Pb ages of 160 ± 3 and 156 ± 1 Ma respectively, making these the oldest reported units within the Dras Arc. We also report zircon U Pb geochronologic and whole rock geochemical results for the Kargil Intrusive Suite which intrudes the volcanic complex. Previous ages for the intrusives have been reproduced (102 ± 2 Ma and 101 ± 2 Ma), and a second, much younger phase (80 ± 1 Ma) has been identified as one of the youngest igneous phases within the Dras Arc. The presence of felsic, adakitic volcanism early in the evolution of the Dras Arc is consistent with the adolescent stages of island arc systems, in which dehydration melting of underplated arc or subducted oceanic crust generates small volumes of felsic magmas. Thus, the intraoceanic Dras Arc initiated in the Neotethyan Ocean during the Upper Jurassic, much earlier than previously reported, and possibly was active right up to collision during the late Palaeocene between 60 and 50 Ma. It is likely that the Dras Arc developed together with the Spongtang Ophiolite-Spong Arc complex and the intraoceanic Zedong terrane of Tibet, before first colliding and accreting onto the passive margin of India, prior to the terminal continental collision.

中文翻译:

上侏罗统长英质火山岩在初期、洋内德拉斯弧、拉达克、喜马拉雅西北部的意义

摘要 德拉斯弧是一个岛弧地体,位于拉达克喜马拉雅山脉的印度河缝合线上。北面与欧亚拉达克基石并列,南面则位于拉马尤鲁复合体和印度被动边缘之上。确定德拉斯弧开始和最终碰撞的时间对于重建新特提斯洋和弧-大陆碰撞时间,在印度-亚洲大陆碰撞末期之前是必不可少的。我们描述了长英质凝灰岩和埃达克质长英质火山岩夹在主要玄武质-安山质 Dras 火山复合体中并确定了年代。这些长英质火山单元产生的上侏罗统锆石 U Pb 年龄分别为 160 ± 3 和 156 ± 1 Ma,使这些单元成为 Dras 弧内最古老的报告单元。我们还报告了侵入火山复合体的 Kargil Intrusive Suite 的锆石 U Pb 年代学和全岩地球化学结果。先前侵入岩的年龄已被重现(102±2 Ma 和 101±2 Ma),第二个更年轻的阶段(80±1 Ma)已被确定为 Dras 弧内最年轻的火成岩阶段之一。在德拉斯弧演化早期,长英质、埃达克质火山活动的存在与岛弧系统的青春期阶段一致,在该阶段,下板弧或俯冲洋壳的脱水熔化产生少量的长英质岩浆。因此,在上侏罗纪,新特提斯洋中的洋内 Dras 弧比先前报道的要早得多,并且可能一直活跃到 60 至 50 Ma 之间的晚古新世碰撞。
更新日期:2021-02-01
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