Ar-Ar ages and geochemistry of Late Cretaceous basalts in the Nanxiong Basin, SE China: Constraints on the subduction and rollback of the Paleo-Pacific Plate.

[Display omitted] • 40Ar-39Ar dating results show Nanxiong basalts were erupted during 76.2–69.9 Ma. • Nanxiong basalts are alkaline to calc-alkaline basalts with OIB-like features. • Nanxiong basalts were derived from metasomatized asthenospheric mantle. • Formations of Nanxiong basalts indicate the rollback of subducted Paleo-Pacific Plate. The Cretaceous arc-related and intraplate mafic rocks are widely distributed across Southeast (SE) China, and provide important information for investigating the Cretaceous dynamical processes of the Paleo-Pacific Plate. This study presents new petrological, geochronological, and geochemical analyses for the Late Cretaceous basalts from the Nanxiong Basin in SE China. The Nanxiong basalts yield the 40Ar/39Ar plateaus ages of 76.2–69.9 Ma, they belong to alkaline-calc-alkaline basalts and have OIB-like geochemical patterns with enrichment on LILEs and LREEs. These basalts have initial 87Sr/86Sr ratios of 0.7055–0.7062 and ε Nd (t) values of + 2.5-+3.4. Such signatures suggest that the Nanxiong basalts were the products of partial melting of asthenospheric mantle, which might be metasomatized by slab-derived melts with a proportion of sediments. Our new results, along with the regional reported ages and geological observations, suggest that the Nanxiong OIB-like basalts were formed in an intraplate extensional setting, in response to the rollback of the subducted Paleo-Pacific slab during the Late Cretaceous. [ABSTRACT FROM AUTHOR]