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Temporospatial variation in the late Mesozoic volcanism in southeast China

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.