The Formation Of Mesozoic Adakitic Rocks On North China Craton:Theoretical Discussions And Sample Considerations

This paper collected and summarized the latest published geochemical data(more than 700 sets of data)of adakite and adakitic rocks in the North China Craton,and the corresponding age data of these rocks with the specific location,summed up the temporal and spatial distribution and rock characteristics of the adakite and adakitic rocks in North China Craton,and discussed the corresponding diagenetic process.Adakitic rocks in the North China Craton in Indosinian period are generally acidic intrusive rocks,with low Mg O content(< 4%),mainly concentrated in the northern part of the North China Craton;200-180 Ma period,adakite rocks are barely exist in the North China Craton;180-145 Ma period,the North China Craton adakites and adakitic rocks are still mainly consist of intermediate-acid rock with low magnesium,and concentrated in the northern part of North China Craton and Jiaodong Peninsula;145-135 Ma period,high magnesium(Mg O ? 4%)adakites and adakitic rocks began to appear,and the number of neutral magmatite increases;After135 Ma,more adakites and adakitic rocks began to appear in the Dabie Mountain area the central North China craton.This paper argues that the Mesozoic adakitic rocks in North China is likely to have multiple diagenetic processes: separation and crystallization of mafic magma may can explain most of neutral intrusive rocks with adakitic geochemical characteristics in the North China Craton;Diagenetic process of the neutral volcano rock formation with adakitic geochemical characteristics is very complex,overall,this kind of adakite and adakitic rock show a relationship with the ancient rocks in the lower crust of the North China,reasonable diagenetic processes are as follows: a thickened lower crust melting,delamination and melting of the lower crust or mixing or separation and crystallization of mafic magma;Acid intrusive rocks with adakitic geochemical characteristics may come into being through partial melting of mafic lower crust under high pressure(P = 1.5 GPa);A typical acid extrusive example from Li Wuping(2011)reports of late Cretaceous rhyolite in Yixian,Daxingzhuangand,which considered formed by partial melting of thickened lower crust.