Late Carboniferous-Early Permian high- and low-Sr/Y granitoids of the Xing'an Block, northeastern China: Implications for the late Paleozoic tectonic evolution of the eastern Central Asian Orogenic Belt

This study presents new zircon U-Pb geochronological, whole-rock geochemical, and zircon Hf isotopic data along with regional geological observations for five late Paleozoic granitic plutons within the Xing'an Block of northeastern China. These data provide insights into the petrogenesis of these granitoids and the late Paleozoic tectonic evolution of the region. The geochronological and geochemical data indicate that the intrusions were emplaced during two separate periods, with the resulting granites having distinct geochemical features. The early Late Carboniferous (321-310 Ma) granitic Lizishan (US), Xiaonangou (XNG), and Dabeigou (DBG) plutons have high Sr/Y values (33.15-126.73), with low concentrations of Y and heavy rare earth elements (HREE), indicating adakitic affinities. However, the XNG granodiorites contain higher concentrations of MgO, Cr, and Ni, and have higher Mg# values (57-59) than the other plutons. The latest Carboniferous-Early Permian (301-296 Ma) granitic Weilegesi (WLGS) and Wuyi (WY) plutons are high-K calc-alkaline, with low Sr/Y ratios (0.18-24.15), and show petrological and geochemical characteristics of I-type granites. In addition, the magmatic zircon crystals within these plutons yield positive epsilon(Hf)(t) values (+4.1 to +12.9) and juvenile two-stage model (T-DM2) ages (1056-499 Ma). The timing of emplacement and geochemical and isotopic compositions of the LZS and DBG granitoids are indicative of derivation from magmas generated by the partial melting of thickened lower crustal material, whereas the XNG granitoids were most likely formed from magmas generated by the partial melting of delaminated lower crustal material that subsequently interacted with mantle material during ascent. The latest Carboniferous-Early Permian low-Sr/Y granitoids may have formed from magmas generated by the partial melting of a dominantly juvenile amphibolite-facies crustal source under relatively low-pressure conditions, with these magmas subsequently undergoing variable degrees of fractional crystallization. Combining these new data with the results of previous research indicates that the terminal collision between the Xing'an and Songliao blocks occurred between the late Early and early Late Carboniferous, and the voluminous Late Carboniferous to Early Permian granitoids in the Xing'an Block are most likely related to post-collisional delamination. (C) 2018 Published by Elsevier B.V.