The Ladakh Himalayan ophiolites preserve remnants of the eastern part of the Neo-Tethyan Ocean, in the form of Dras, Suru Valley, Shergol, Spongtang and Nidar ophiolitic sequences. In Kohistan region of Pakistan, Muslim Bagh, Zhob and Bela ophiolites are considered to be equivalents of Ladakh ophiolites. In western Ladakh, the Suru–Thasgam ophiolitic slice is highly dismembered and consists of peridotites, pyroxenites and gabbros, emplaced as imbricate blocks thrust over the Mesozoic Dras arc complex along the Indus Suture Zone. The Thasgam peridotites are partially serpentinized with relict olivine, orthopyroxene and minor clinopyroxene, as well as serpentine and iron oxide as secondary mineral assemblage. The pyroxenites are dominated by clinopyroxene followed by orthopyroxene with subordinate olivine and spinel. Gabbros are composed of plagioclase and pyroxene (mostly replaced by amphiboles), describing an ophitic to sub-ophitic textural relationship. Geochemically, the studied rock types show sub-alkaline tholeiitic characteristics. The peridotites display nearly flat chondrite-normalized rare earth element (REE) patterns ((La/Yb)N = 0.6–1.5), while fractionated patterns were observed for pyroxenites and gabbros. Multi-element spidergrams for peridotites, pyroxenites and gabbros display subduction-related geochemical characteristics such as enriched large-ion lithophile element (LILE) and depleted high-field-strength element (HFSE) concentrations. In peridotites and pyroxenites, highly magnesian olivine (Fo88.5-89.3 and Fo87.8-89.9, respectively) and clinopyroxene (Mg no. of 93–98 and 90–97, respectively) indicate supra-subduction zone (SSZ) tectonic affinity. Our study suggests that the peridotites epitomize the refractory nature of their protoliths and were later evolved in a subduction environment. Pyroxenites and gabbros appear to be related to the base of the modern intra-oceanic island-arc tholeiitic sequence.

中文翻译：

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拉达克喜马拉雅印度河缝合带与弧相关的 Suru-Thasgam 蛇绿岩切片的岩石学和地球化学特征

拉达克喜马拉雅蛇绿岩保留了新特提斯洋东部的残余物，以德拉斯、苏鲁谷、舍尔戈尔、斯蓬唐和尼达尔蛇绿岩序列的形式存在。在巴基斯坦的 Kohistan 地区，穆斯林 Bagh、Zhob 和 Bela 蛇绿岩被认为是拉达克蛇绿岩的等价物。在拉达克西部，Suru-Thasgam 蛇绿岩片被高度肢解，由橄榄岩、辉石岩和辉长岩组成，以覆瓦状块体的形式安放在沿印度河缝合带的中生代德拉斯弧复合体上。Thasgam 橄榄岩部分蛇纹石化，有残余橄榄石、斜方辉石和少量单斜辉石，以及作为次生矿物组合的蛇纹石和氧化铁。辉石岩以单斜辉石为主，斜方辉石次之，橄榄石和尖晶石次之。辉长岩由斜长石和辉石组成（大部分被闪石取代），描述了一种蛇绿到亚蛇绿的纹理关系。地球化学上，所研究的岩石类型显示出亚碱性拉斑斑斑岩特征。橄榄岩显示出几乎平坦的球粒陨石归一化稀土元素 (REE) 模式 ((La/Yb)ñ= 0.6-1.5），而辉石岩和辉长岩观察到分馏模式。橄榄岩、辉石岩和辉长岩的多元素蛛网图显示了与俯冲相关的地球化学特征，例如富集的大离子亲石元素 (LILE) 和贫化的高场强元素 (HFSE) 浓度。在橄榄岩和辉石岩中，高镁橄榄石（Fo88.5-89.3和佛87.8-89.9，分别）和单斜辉石（Mg 编号分别为 93-98 和 90-97）表明超俯冲带（SSZ）构造亲和力。我们的研究表明，橄榄岩是其原岩难熔性质的缩影，后来在俯冲环境中演化。辉石岩和辉长岩似乎与现代大洋内岛弧拉斑岩层序的基底有关。