Himalayan detrital chromian spinels and timing of Indus-Yarlung ophiolite erosion

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• 作者：Xiumian Hu^a ; ^{huxm@nju.edu.cn" class="auth_mail} ; Wei An^a ; Jiangang Wang^a ; ^b ; Eduardo Garzanti^c ; Ronghua Guo^a ; ^d
• 关键词：Detrital chromian spinels ; Himalaya ; Indus-Yarlung ophiolite ; Southern Tibet
• 刊名：Tectonophysics
• 出版年：7 May, 2014
• 年：2014
• 卷：621
• 期：Complete
• 页码：60-68
• 全文大小：998 K

文摘

The geochemistry of detrital chromian spinels is commonly used to discriminate provenance from different tectonic settings of mafic and ultramafic igneous rocks. Detrital spinels in Cenozoic foreland-basin successions fed from the Himalaya Orogen were assertively interpreted as sourced from the ophiolitic rocks of the Indus-Yarlung suture zone. This study compares the geochemistry of detrital Cr-spinels from the Tethys Himalaya passive margin and Cretaceous Xigaze forearc successions with those from the Indus-Yarlung ophiolites. Cr-spinels in the Indus-Yarlung ophiolites have low TiO₂ (mostly < 0.2%) and high Al₂O₃ (10-48%). Detrital Cr-spinels from the Tethyan Himalaya have instead high TiO₂ (mostly > 0.2%) and low Al₂O₃ (mainly 6-23%), indicating a rift-related basaltic origin. Detrital Cr-spinels from the Xigaze forearc basin have either low TiO₂ (mostly < 0.2%) and low Al₂O₃ (4-34%), suggesting provenance from a supra-subduction-zone peridotite, or high TiO₂ (> 1.0%), indicating intra-plate basaltic origin. Compositional fingerprints of detrital Cr-spinels from Lower Eocene foreland-basin strata in the central-eastern Himalaya indicate provenance from the Lhasa Block without input from the Indus-Yarlung ophiolites. Only Cr-spinels from the Lower Eocene foreland-basin strata in the north-western Himalaya and the Upper Eocene-Lower Miocene remnant-ocean turbidites of the Bengal basin are mostly ophiolite-derived. The Indus-Yarlung ophiolites were thus emplaced and exposed to erosion since the Early Eocene (> 50 Ma) in the NW Himalaya, but only subsequently (50-38 Ma) in the eastern Himalaya.