Tracing the subduction and accretion history of the trench-arc-basin system in the Chinese Eastern Tianshan: Insights from Paleozoic magmatic and crustal evolution

Abstract

Accretionary orogens function as crucial sites for the generation of arc igneous rocks and continental crust, but the spatial and temporal distribution of arc igneous rocks and the link between the arc magmatic processes and crust generation within individual orogens remains poorly constrained. To address this issue, we have summarized published geochemical and zircon isotopic data for Paleozoic (∼460–280 Ma) mafic–intermediate–felsic igneous rocks within five individual belts from the Chinese Eastern Tianshan of the southern Central Asian Orogenic Belt (CAOB), which aim to explore the variations in magma sources (juvenile or reworked crust) and crustal thickness in response to tectonic and crustal evolution over time. This summary highlights the systematic variation in elemental and isotopic signatures of magmas in the Eastern Tianshan and makes it possible to quantitatively evaluate the crustal evolution and tectonic switch patterns. Repeated tectonic switches of the Eastern Tianshan trench-arc-basin system during subduction of the Kangguer oceanic plate appear to have occurred in two phases of the northern trench advance (ca. 460–381 Ma and 330–301 Ma, respectively) and the intervening trench retreat (ca. 380–331 Ma), as well as seem to have happened in the southern trench of the Kangguer Ocean with trench southward advance and northward retreat at ca. 360–331 Ma and 330–301 Ma, respectively. The estimated crustal growth in the Eastern Tianshan various from trench advance accompanied by significant crustal thickening (i.e., northern trench advance at ca. 460–421 Ma and southern trench advance at ca. 360–331 Ma, respectively) to northern trench retreat with crustal thinning (ca. 380–331 Ma). Most of the magma in the Eastern Tianshan was generated by crustal reworking or mixing.