摘要
Magmatism in SE China was dormant during 204―180 Ma, but was reactivated in 180― 170 Ma (early J2), and then became more and more intensive towards the end of early Cretaceous. The small-scale early J2 magmatism is the incipience to long-term and large-scale magmatism in this region. A near east-west (EW) trend volcanic belt was distributed across south Hunan, south Jiangxi and southwest Fujian was formed during early J2 time. Along this belt from the inland toward the coast, the lithology of basalts changes from alkali into tholeiite, and the amount of erupted volcanic rocks and the proportions of rhyolites coexisting with the basalts increase. On the basis of geochemical char- acteristics of these basalts, we infer that the melting degree of source rocks and the extent of frac- tional crystallization and crustal contamination all increased whereas the depth of mantle source de- creased from the inland to the coast, which led to the variations of geological characteristics of the volcanic belt. In early J2, the western spreading Pacific plate began to subduct underneath SE China continental block, reactivating near EW trend deep fault that was originally formed during the Indos- inian event. The stress of the western spreading Pacific plate and the extent of asthenosphere up- welling increased from the inland to the coast, which is consistent with the generation and evolution of early J2 basalts.
Magmatism in SE China was dormant during 204-180 Ma, but was reactivated in180-170 Ma (early J_2), and then became more and more intensive towards the end of early Cretaceous.The small-scale early J_2 magmatism is the incipience to long-term and large-scale magmatism inthis region. A near east-west (EW) trend volcanic belt was distributed across south Hunan, southJiangxi and southwest Fujian was formed during early J_2 time. Along this belt from the inlandtoward the coast, the lithology of basalts changes from alkali into tholeiite, and the amount oferupted volcanic rocks and the proportions of rhyolites coexisting with the basalts increase. On thebasis of geochemical characteristics of these basalts, we infer that the melting degree of sourcerocks and the extent of fractional crystallization and crustal contamination all increased whereasthe depth of mantle source decreased from the inland to the coast, which led to the variations ofgeological characteristics of the volcanic belt. In early J_2, the western spreading Pacific platebegan to subduct underneath SE China continental block, reactivating near EW trend deep fault thatwas originally formed during the Indos-inian event. The stress of the western spreading Pacificplate and the extent of asthenosphere up-welling increased from the inland to the coast, which isconsistent with the generation and evolution of early J_2 basalts.
作者
XIE Xin1, XU Xisheng1, ZOU Haibo2, JIANG Shaoyong1, ZHANG Ming3 & QIU Jiansheng1 1. State Key Laboratory of Mineral Deposit Research, Department of Earth Sciences, Nanjing University, Nanjing 210093, China
2. Department of Earth and Space Sciences, University of California at Los Angeles, Los Angeles, CA90095-1567, USA.
3. GEMOC ARC National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, Sydney, N.S.W. 2109, Australia
基金
This work was supported by the National Natural Science Foundation of China (Grant Nos. 40125007, 40221301 and 40132010).
