Switching from advancing to retreating subduction in the Neoproterozoic Tarim Craton, NW China: Implications for Rodinia breakup

Abstract

Geodynamic drivers for the supercontinent cycle are generally attributed to either top-down (subduction-related) or bottom-up (mantle-related) processes. Compiled geochemical data and U–Pb ages and Hf isotopic signatures for magmatic and detrital zircons from the Tarim Craton reveal a distinct change in subduction style during the Neoproterozoic. The subduction cycle is recorded in increasing and decreasing intensity of subduction-related magmatic rocks and time-equivalent sedimentary successions, and converse trends of εHf(t) values and corresponding changes in crustal incubation time. These trends are consistent with a switch from advancing to retreating subduction. The switch likely occurred at ca. 760 Ma when zircon εHf(t) values increase and crustal incubation times decrease following a transitional shift between 800 ​Ma and 760 ​Ma. A switch at this time is consistent with Rodinia breakup and may have resulted in the late Neoproterozoic Tarim rift basin. The long-lived (ca. 500 Ma) subduction recorded in the Tarim Craton suggests the predominance of a top-down process for Rodinia breakup on this part of its margin.

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