Petrogenesis and tectonic implications of Early Cretaceous I-type granites from offshore drilling in east of the Fuzhou City, Southeast China

Abstract

The Cretaceous (<115 Ma) granitoid rocks in Southeast China provide critical insights into the role of juvenile materials in their genesis, as evidenced by the presence of I- and A-type granites. This study presents comprehensive geochronological, mineralogical, geochemical, and Sr–Nd–Hf isotopic data for granites collected from the offshore drilling in the western East China Sea, located east of the Fuzhou City (Fujian Province), Southeast China. Zircon, apatite, and titanite U–Pb dating reveal that the granite samples formed at 112–111 Ma. The samples exhibit geochemical characteristics typical of I-type granites, with negative whole-rock ε_Nd(t) values (–4.4) and zircon ε_Hf(t) values ranging from –2.8 to 0.1. These I-type granites were primarily formed through partial melting of mafic igneous protoliths, followed by magma mixing with ancient crustal materials. We propose that the SE China coast underwent a transition from a compressional to a lithospheric extensional environment during the late Early Cretaceous, driven by the slab rollback of the subducted Paleo-Pacific Plate. This lithospheric extension facilitated the underplating of mantle-derived magma, which modified the crustal source and induced melting of continental arc crustal materials.