Crustal architecture and metallogeny associated with the Paleo-Tethys evolution in the Eastern Kunlun Orogenic Belt, Northern Tibetan Plateau

Abstract

The Eastern Kunlun Orogenic Belt (EKOB) in the Northern Tibet Plateau hosts a wide variety of metal deposits related to the Late Paleozoic to Mesozoic magmatism. In this study, we investigate the spatio-temporal distribution of the Late Paleozoic to Mesozoic granitic rocks and associated metal deposits in the EKOB and provide a comprehensive compilation of the geochronological, geochemical and isotopic data on these rocks. We compute regional zircon Hf isotope and crustal thickness maps from the data, based on which a comprehensive model is proposed involving subduction (ca. 270–240 Ma), continental collision (ca. 240–224 Ma), and post-collisional extension (ca. 224–200 Ma) for the Late Paleozoic to Mesozoic Paleo-Tethys evolution in the EKOB.

Zircon Hf isotopic and crustal thickness mapping of Late Paleozoic to Mesozoic magmatic rocks was carried out to evaluate their spatio-temporal and genetic links with the regional metallogeny. The polymetallic Fe-skarn and porphyry Cu (Mo) deposits in the EKOB are located above the Moho uplift region, featuring a comparatively thin crust. Granites associated with porphyry Cu (Mo) and polymetallic Fe skarn mineralization are commonly characterized by high εHf(t) and younger TDMc values, whereas granite related to Cu-Mo-Sn skarn deposits exhibit more variable εHf(t) values, TDMc ages, and the crust thickness, which suggest that more crustal materials contributed to the formation of Cu-Mo-Sn skarn deposits than those for porphyry Cu (Mo) and polymetallic Fe skarn mineralization. In contrast, vein-type Au deposits are located primarily where the Moho surface displays a depression, i.e., where the continental crust is relatively thick. The magmatic rocks associated with Au mineralization are characterized by low εHf(t) and high TDMc values, representing reworked ancient crustal components, similar to those associated with porphyry Mo and epithermal Ag-Pb-Zn-(Au) deposits. Our study indicates that the emplacement of magmatic-hydrothermal deposits was controlled by the crustal structure and magma sources.