Temporospatial variation in the late Mesozoic volcanism in southeast China

Abstract

Abstract. The magmatism (including volcanism) in East Asia (or China) could provide key clues and age constraints for the subduction and dynamical process of the Paleo-Pacific Plate. Although many absolute isotope ages of extrusive rocks have been published in the 1980s–2000s, large uncertainties and large errors prevent the magmatism in southeast (SE) China from being well understood. In this study, we investigate the zircon geochronology of extrusive rocks and temporospatial variations in the late Mesozoic volcanism in SE China. We reported zircon U–Pb ages of new 48 extrusive rock samples in the Shi-Hang tectonic belt. Together with the published data in the past decade, ages of 291 rock samples from ∼40 lithostratigraphic units were compiled, potentially documenting a relatively complete history and spatial distribution of the late Mesozoic volcanism in SE China. The results show that the extrusive rocks spanned ∼95 Myr (177–82 Ma), but dominantly ∼70 Myr (160–90 Ma), within which the volcanism in the early Early Cretaceous (145–125 Ma) was the most intensive and widespread eruption. We propose that these ages represent the intervals of the Yanshanian volcanism in SE China. Spatially, the age geographic pattern of extrusive rocks shows that both the oldest and youngest age clusters occur in the coastal magmatic arc (eastern Zhejiang and Fujian), and the most intensive and widespread age group (145–125 Ma) occurs in a back arc or rifting basin (eastern Jiangxi, central Zhejiang, and northern Guangdong), implying that the late Mesozoic volcanism migrated northwest and subsequently retreated southeast. This volcanic migration pattern may imply that the Paleo-Pacific Plate subducted northwestward and the roll-back subduction did not begin until the Aptian (∼125 Ma) of the mid-Cretaceous.