地质学
岩浆作用
裂谷
地震学
中国
变化(天文学)
古生物学
构造学
政治学
天体物理学
物理
法学
作者
Chun‐An Fan,Shaohong Xia,Jianyu Cao,Fang Zhao,Jianbao Sun,Keshu Wan,H. Xu
标识
DOI:10.1016/j.margeo.2018.12.007
摘要
The northeastern margin of the South China Sea experienced continental rifting followed by magmatism in the Cenozoic. This evolution has strongly influenced the heterogeneity of its crustal structure. To gain insights into the spatial variation in crustal structure, data from 30 ocean bottom seismometers were used to forward model ten P-wave velocity models along both dip and strike directions. The Cenozoic strata (1.7–3.5 km/s), the Mesozoic strata (3.5–5.5 km/s), the crystalline crust (5.5–7.5 km/s) and high velocity lower crust (7.0–7.5 km/s) were identified based on P-wave velocities. Overall, the crust thins from ~25 km on the continental shelf to ~15 km on the slope, with thicker crust underneath the Dongsha Basin (a Mesozoic basin) but thinner crust underneath the pre-Cenozoic NW-trending fault zones. This difference in thickness is possibly controlled by different strength of inherited structures, i.e., the Dongsha Basin and the fault zones. Furthermore, a widespread high velocity lower crust layer, which resulted from the intrusion of a mafic sill complex, was observed over the shelf to slope. Mafic intrusions within the lower crust have uplifted the caprock on the shelf, and magma eruptions have formed many post-rift seamounts on the slope. The evidence suggests that post-rift magmatism overprinted the vertical crustal structure. We therefore propose that the heterogeneous crustal structures in this passive margin are an integrated result of segmental extension followed by magmatic overprinting.
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