The Cause For Nuna Breakup In The Early To Middle Mesoproterozoic

The dynamic mechanism responsible for the breakup of Nuna supercontinent (1.6-1.3 Ga) is a key for understanding the early to middle Mesoproterozoic environment, life and mineralization on Earth. Although much research has been done to unravel the dispersion of young supercontinents (e.g., Pangea), efforts by sorting out critical geological records to disclose the driving force for Nuna breakup are still rare. Here we focus on this issue by integrating new whole-rock geochemical data, zircon U-Pb ages, Hf-in-zircon and Nd isotopes for Mesoproterozoic granitoids in the Chinese Central Tianshan (CTB) at the Central Asian Orogenic Belt (CAOB). Moreover, global geological data in the early to middle Mesoproterozoic are compiled to place further constraints. The studied granitoids are I-type granites emplaced at ca. 1480-1450 Ma. They were formed in an active continental margin of CTB that once belonged to the Fennoscandia in the margin of Nuna. These results, together with the available geological records in CTB, CAOB and Fennoscandia, indicate a subduction system existed along the periphery of these domains in the early to middle Mesoproterozoic. This subduction system was temporally and spatially linked to the 1.6-1.3 Ga accretionary belts in the peripheral blocks of Nuna supercontinent, suggesting an encircling subduction system surrounding Nuna supercontinent. The encircling subduction system was accompanied by intermittent Mesoproterozoic plume magmatism, some of which were geochemically overprinted with subduction-related signatures, suggesting a dominant continuous circumsupercontinent subduction operating on the breakup of Nuna supercontinent. Moreover, these episodic plumerelated magmatism are temporally and geodynamically linked to the exterior subduction surrounding the Nuna supercontinent. Our study therefore demonstrates that the development of an exterior subduction system gave rise to the breakup of Nuna supercontinent, which was accompanied by subordinate plume activities.