当前位置: X-MOL 学术Earth Sci. Rev. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Geochemical characterization of ophiolites in the Alpine-Himalayan Orogenic Belt: Magmatically and tectonically diverse evolution of the Mesozoic Neotethyan oceanic crust
Earth-Science Reviews ( IF 12.1 ) Pub Date : 2020-09-01 , DOI: 10.1016/j.earscirev.2020.103258
Harald Furnes , Yildirim Dilek , Guochun Zhao , Inna Safonova , M. Santosh

Abstract Ophiolites are important archives of oceanic crust development and preservation in the rock record, and the Alpine-Himalayan Orogenic Belt (AHOB) is one of the most comprehensive ophiolite depositories in earth’s history. We have compiled published data on the field occurrences and geochemistry from 137 AHOB ophiolites, ranging in age from Triassic through Cretaceous, in order to characterize the nature of the Mesozoic Neotethyan oceanic crust. We have used in this synthesis our recent ophiolite classification approach and applied the most effective geochemical discrimination diagrams to categorize the Neotethyan ophiolites within the AHOB. The subduction-related, Backarc (BA), Forearc (FA), Backarc to Forearc (BA-FA) and Volcanic Arc (VA) ophiolites exhibit different geochemical features, with the BA and FA types defining the end-members with low-high and high subduction influence, respectively. The subduction-related ophiolites constitute 76% of the ophiolite record in the AHOB, with the BA type ophiolites being the most dominant group (43%), followed by the BA-FA (19%) and with FA and VA types as subordinate groups (8% and 6%, respectively). The subduction-unrelated ophiolites, making up 24% of the AHOB ophiolite archive, include Mid-Ocean Ridge (MOR), Continental Margin, and Plume type ophiolites. The MOR type comprises 19% of this total and is the dominant type in the western part of the AHOB. Both major ophiolite categories are commonly associated with tholeiitic to alkaline ocean island basalt (OIB) associations, which represent the remnants of plume-proximal magmatism in different Neotethyan seaways. Subduction-unrelated ophiolites in the westernmost end of the Neotethyan realm were derived from downgoing oceanic plates, and were involved in high-pressure, subduction zone metamorphism prior to their exhumation along the suture zones. Subduction-related ophiolites, derived from the upper plates at Neotethyan convergent margins, escaped such high-pressure metamorphism and extreme fragmentation during their emplacement. Therefore, their complete Penrose ophiolite stratigraphy with greenschist facies metamorphic overprint is commonly well preserved in the collision zones of the AHOB. Different subduction contributions (from zero to 100% in the MOR and FA, respectively) may attest to variable slab dip angles and fluctuations in slab-induced elements and sediments into the mantle melt source of ophiolite–forming magmas.

中文翻译:

高山-喜马拉雅造山带蛇绿岩的地球化学特征:中生代新特提斯洋壳的岩浆和构造多样性演化

摘要 蛇绿岩是岩石记录中海洋地壳发育和保存的重要档案,高山-喜马拉雅造山带(AHOB)是地球历史上最全面的蛇绿岩矿床之一。我们汇编了 137 个 AHOB 蛇绿岩的野外产状和地球化学数据,年龄范围从三叠纪到白垩纪,以表征中生代新特提斯洋壳的性质。我们在此综合中使用了我们最近的蛇绿岩分类方法,并应用了最有效的地球化学鉴别图对 AHOB 内的新特提斯蛇绿岩进行了分类。与俯冲相关的 Backarc (BA)、Forearc (FA)、Backarc to Forearc (BA-FA) 和 Volcanic Arc (VA) 蛇绿岩表现出不同的地球化学特征,BA 和 FA 类型分别定义了具有低俯冲影响和高俯冲影响的末端成员。俯冲相关蛇绿岩占 AHOB 蛇绿岩记录的 76%,其中 BA 型蛇绿岩是最主要的群(43%),其次是 BA-FA(19%),FA 和 VA 型为从属群(分别为 8% 和 6%)。与俯冲无关的蛇绿岩占 AHOB 蛇绿岩档案的 24%,包括大洋中脊 (MOR)、大陆边缘和羽状蛇绿岩。MOR 类型占总数的 19%,是 AHOB 西部的主要类型。两种主要的蛇绿岩类别通常都与拉斑质至碱性海洋岛玄武岩 (OIB) 组合有关,它们代表了不同新特提斯海道中羽状近端岩浆作用的残余物。新特提斯界最西端的与俯冲无关的蛇绿岩来自下沉的大洋板块,在沿着缝合带剥脱之前参与了高压俯冲带变质作用。与俯冲相关的蛇绿岩来自新特提斯会聚边缘的上板块,在它们就位期间逃脱了这种高压变质作用和极端破碎。因此,他们完整的彭罗斯蛇绿岩地层与绿片岩相变质叠印通常在AHOB的碰撞带中保存完好。不同的俯冲贡献(分别在 MOR 和 FA 中从 0 到 100%)可能证明板片倾角的变化以及板片诱发元素和沉积物在蛇绿岩形成岩浆的地幔熔融源中的波动。
更新日期:2020-09-01
down
wechat
bug