The role of deep processes controls on variation of compositions of adakitic rocks
深部过程对埃达克质岩石成分的制约

There are many geochemical similarities and significant dissimilarities among Adakite, early Archaean TTG suites and Yanshanian intermediate-acid magamtic rocks (" adakitic rocks" or potassic adakite) in eastern China. Simple geochemical parameters, such as silica content, Mg# and K2O content, show that TTG and "adakitic rocks" from eastern China are distinct from adakite, suggesting that they experienced different deep processes. Comparing with slab-melting generated adakite, the early Archaean TTG suites have higher SiO2 and lower Mg# and, potassic adakite from eastern China show lower Mg# and higher K2O. The higher-Mg# adakites imply that the ocean slab melting generated pristine adakite melts interacted with the mantle wedge. There is little convincing evidence for a direct mantle component in TTG, implying that accommodate TTG production through melting of hydrous basaltic material at the base of thickened crust, without modern-style subduction processes. The potassic adakite from eastern China may predominately experienced partial melting of underplated basaltic rocks (lower Mg# potassic adakite) , or delimitation-melting of lower crust and interacted with mantle peridotite ( higher Mg# potassic adakite), and followed assimilation and contamination of crustal intermediate-acid rocks. Potassic adakite might be generated from a basaltic underplated layer that was metasomated by small melt fractions from asthenosphere mantle. Adakitic magmatism is then an accompanying product of Yanshannian lithosphere thinning and magmatism, which may be related to a upwelling of mantle plume.