Late Mesozoic porphyry copper deposits in NE China: Post-collisional versus subduction-related magmatic systems

Recent discoveries of Late Mesozoic porphyry Cu deposits (PCDs) in Northeast (NE) China reveal a distinct spatial metallogenic zonation, with Late Jurassic PCDs in the north dominated by Cu-Mo and Early Cretaceous PCDs in the east marked by Cu-Au mineralization. However, the mechanisms controlling this metallogenic contrast remain unclear. To tackle this issue, we combined geological, geochronological, and geochemical data to determine the genesis of these deposits and the key factors controlling their distinct Cu-Mo and Cu-Au mineralization. Geochronological data show that the Late Jurassic PCDs were formed during a short-lived mineralization event (ca. 150–147 Ma), in contrast to the Early Cretaceous PCDs, which exhibit a prolonged formation history (ca. 120–95 Ma). Geochemical data demonstrate that the northern Cu-Mo PCDs originate from partial melting of thickened juvenile lower crust, whereas the eastern Cu-Au PCDs result from oceanic crust-derived melts contaminated by mantle wedge materials. Integrated analysis suggests that the Cu-Mo PCDs formed in a post-collisional setting after the Mongol-Okhotsk Ocean closure, while the Cu-Au PCDs formed in a subduction setting associated with Paleo-Pacific oceanic plate subduction. Despite the presence of hydrous and oxidized magmas in both regions, the northern PCDs exhibit higher Sr/Y, La/Yb, and Sm/Yb ratios than the eastern PCDs, indicating greater magma differentiation depths controlled by crustal thickness. We therefore propose that the depths of magma differentiation govern the metallogenic zoning of Late Mesozoic PCDs in NE China.