Collision-induced subduction jump recorded by initiation of a >6000-km-long Cambrian subduction zone within the Paleo-Asian Ocean

Abstract

Subduction is the main driver of plate tectonics. The initiation of subduction zones is a foundational step in this context, but remains elusive because no present example of subduction initiation exists. Ophiolites formed over nascent subduction zones in the past provide the key to constraining the processes of subduction initiation. In this study, we document three Cambrian ophiolites with supra-subduction zone affinity within the southern part of the Central Asian Orogenic Belt. These ophiolites likely reflect the inception of a plate-boundary scale subduction zone within the Paleo-Asian Ocean. Our findings, together with a comprehensive compilation of Cambrian ophiolites in the Central Asian Orogenic Belt, indicate diachronous subduction initiation(s) along a >6,000 km zone within the Paleo-Asian Ocean between 536-528 Ma. The timing of subduction initiation of the Paleo-Asian Ocean coincides with the closure of the Mirovoi Ocean following the collision of a series of microcontinents with the Siberia Craton. Accordingly, the widespread Cambrian subduction initiation of the Paleo-Asian Ocean most likely represents a typical record of collision-induced subduction jump. Our study provides a new scenario that subduction initiations would locate at oceanic weak zones rather than the passive margins of the accreted microcontinents during the collision-induced subduction jump process.