Abstract
Arc magmatism is an important process in the formation and evolution of the continental crust. Various arcs developed in the southern margin of Eurasian continent that recorded the final formation and growth of these micro-continent before the final India-Eurasia amalgamation. We have examined the often neglected Tengchong arc segment in southeastern Tibet using compiled zircon U-Pb-Hf and whole-rock geochemistry with GPS location and lithology control. The aim is to better understand the driving mechanism of spatial migration and temporal evolution of multi-stage high-MAR (magma addition rate) events and its role in formation and growth of Tengchong arc segment.Results indicate three magmatic “flare-ups” during east-to-west arc migration, from ~131–111 Ma (eastern), ~76–64 Ma (central), to ~55–49 Ma (western), during amalgamation of Lhasa-Tengchong and Qiangtang-Baoshan blocks and final collision of India-Asia plate following subduction of Neo-Tethys. Zircon Hf isotopes and geochemical analyses shows the significant increasing juvenile and/or mantle-derived materials and the range of isotopes also broaden during flare-ups, indicating the melting of diverse lithospheric and upper plate domains. Through comparison with geophysical parameters, these pulses are closely coupled with the arc migration along with changes of crustal thickness, but not correlated with angle and rates of convergence. The spatial arc migration of the multi-stage high-MAR events in Tengchong arc segment was potentially driven by slab steepening and break-off following the initial collision, and abrupt changes of subduction slab dynamics. These processes are well coupled with multi-stage interactions of crust-mantle and transitional Moho-depths.
Published Version
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