Tectonic transition from Late Carboniferous subduction to Early Permian post-collisional extension in the Eastern Tianshan, NW China: Insights from geochronology and geochemistry of mafic–intermediate intrusions

The closure of the Junggar Ocean between the Central Tianshan and Junggar terranes is essential in understanding the final assembly of the southern Central Asian Orogenic Belt. This study presents new whole-rock geochemical, Sr–Nd and zircon U–Pb–Hf isotopic data for mafic–intermediate intrusions from the Central Tianshan block to provide robust constraints on the final closure of the ocean. LA-ICP-MS U–Pb dating on magmatic-type zircons yields weighted mean 206Pb/238U ages of ca. 310Ma and ca. 290Ma, which are interpreted as the crystallization ages of the intrusions. Petrographic and geochemical analyses of the Late Carboniferous mafic–intermediate rocks, characterized by typical subduction-related signatures, low Sm/Yb (