Relation between Mesozoic magmatism and plate subduction in eastern China: Comparison among Zhejiang-Fujian, Japan arc and Andes arc

The Mesozoic-Cenozoic tectonic background of eastern China is the top concern for geologists in China. After theplate tectonic theory is introduced into China since the 1970s, the Chinese geologists generally accepted the view that eastern China Mesozoic subduction of the Pacific plate to Eurasian plate result in strong tectonic-magmatic activities and corresponding mineralization, and even become generally cognitive theory remains widespread by Chinese and foreign scholars. But, this paper argues that a lot of problems. As is known to all, island arc predominantly basalt exposed, continental arc are composed dominantly of andesite, basalt and andesite are not developed in eastern China. In this paper, according to the thinking way of big data, Japan island arc and the Andean arc Cenozoic magmatic rocks statistics show that the above understanding is basically right: Japan arc mainly basalt, second is andesite; Andean arc mainly is andesite, followed by basalt; And eastern China (represented by Zhejiang-Fujian area), are mainly granite, the second is basalt, a bimodal distribution characteristics. The tectonic background of eastern China is completely different from Japan and the Andean, and there is not clear evidence of subduction in eastern China. Second, island arc and continental arc have obvious composition and structure zoning, such as Japan arc, magmatic activity is starting from the trench, then front-arc, arc, rear-arc to back-arc. Andean arc is less obviously than Japan, eastwards from the trench to the mainland fore-arc trench complex-arc magmatic rocks-back-arc basin. Where is structure and composition zone associated with subduction in eastern China (including the East China Sea continental shelf, China's eastern coastal) ? Our study focused on the Zhejiang-Fujian area 400km width within the scope of the distribution of the Jurassic and Cretaceous magmatic rocks, from age to geochemical (SiO2, MgO style, the change of K2O, the change of the age, etc.), never has the tendency of zonation from east to west, how to link to plate subduction? Island arc magmatic rocks mainly comes from the depleted mantle, oceanic crust, deep sea sediments, and the fluid caused by the subduction zone, therefore, arc magmatic rocks are with obvious oceanic crust features. Continental arc also comes from the mantle, but magma across the continental crust, and brings obvious continental crustal contamination, so the Andean type magmatic rocks have obvious marks of continental crust. If not considering the influence of the subduction zone, Continental magmatic rocks should come from the heat asthenosphere mantle. If the heat asthenosphere stay at the bottom of the lithosphere, partial melting, there should be formed continental flood basalts, and intermediate-acid magmatic rocks is very little; On the contrary, if the heat asthenosphere breakthrough lithospheric block and up to the bottom of the crust, it will heat the bottom of the lower crust of partial melting, forming a lot of acidic granite, basalt and andesite is rarely. Emei Mountain is the former, and eastern China is the latter. What are the differences and similarities of magmatic rocks in eastern China, Andean and Japan should be petrologists' first proposition, we suggested that China's petrologists and geochemists study not only in eastern China, but also in the Japan arc and the Andean magmatic rocks deeply and in detail. Compared with eastern China's situation, we will obtain new knowledge, perhaps may help solve the problem of eastern China's magmatic rocks background.