关键词: 中国东南部, 侏罗纪, 火山岩, 岩石成因, 俯冲作用早阶段

Abstract: It is widely accepted that the widespread Cretaceous volcanic rocks in SE China were formed at the late stage of the paleo-Pacific subduction. On the contrary, the geological response of the early stage of the subduction remains unclear. This study focuses on the representative Jurassic volcanic sections in eastern Guangdong, which are the most widespread in SE China. Zircon U-Pb dating results reveal that the Jurassic volcanic rocks were formed intermittently at 192-183 Ma (Songling Fm.), 177- 163 Ma (Jilingwan Fm.) and 162-156 Ma (Gaojiping Gp.). Thus, a younging trend along eastern Guangdong to eastern Fujian to southeastern Zhejiang could be identified for the entire Late Mesozoic volcanic rocks in SE China. Zircon Lu-Hf isotopic analyses show that the Jurassic volcanic rocks were mainly derived by remelting of the Paleoproterozoic crustal basement, with decreasing involvement of juvenile components in their origin over time from Early to Late Jurassic. The petrogenesis of the Jurassic volcanic rocks in eastern Guangdong suggests decreasing crustal extension, corresponding to the forward subduction of the paleo-Pacific slab. Thus, the Jurassic volcanic rocks in eastern Guangdong record the early stage of the paleo-Pacific subduction, and further suggest that the subduction started at around Early Jurassic.

Key words: SE China, Jurassic, volcanic rocks, petrogenesis, early stage of subduction