Abstract

The East Kunlun Orogenic Belt in the northern Tibetan Plateau can be divided into, from north to south, the Northern, Central and Southern Kunlun Belts by the Qimantagh-Xiangride, Aqikekulehu-Kunzhong and Muztagh-Buqingshan sutures. The Yazidaban ophiolitic mélange, located in the westernmost of Qimantagh-Xiangride suture between the Northern and Central Kunlun Belts, consists predominantly of serpentinite, basalt, diabase and andesite. The serpentinites are characterized by low ΣREE contents and depletion of mid-REE showing an ophiolitic ultramafic affinity. The basalts display low ΣREE contents, slightly enrichment of LREE, depletion of LILE and insignificant fractionation of HFSE, which are attributed to E-MORB. Both diabases and andesites are characterized by high ΣREE, strong enrichment of LREE, depletion of Nb, Ta, P and Ti, and significant fractionation of HFSE. These geochemical characteristics indicate that the diabases and andesites were mostly generated in a subduction-related setting. Igneous zircons from the diabase yielded a 206Pb/238U age of 421.5 ± 2.2 Ma (MSWD=0.44), representing the formation time of subduction-related rocks. Together with regional geology, all above constraints on the ultramafic rocks, basalts, andesites and diabases suggest that the Yazidaban ophiolitic mélange represents the remnants of oceanic crust of a back-arc basin and associated subduction-related magmatic rocks.

Supplementary material:https://doi.org/10.6084/m9.figshare.c.4283219

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