Large-scale granitic composite batholite - the evidence of Pacific plate from subduction to extension

Large-scale granitic composite batholite - the evidence of Pacific plate from subduction to extension

Jiuhuashan rock body is the largest Yanshanian composite granite rock body in lower Yangtze area. The main body consists of two stages of magmatic activities, occurring at 141-145 Ma and 121-130 Ma respectively. The early formed rocks are mainly granodiorite and monzogranite, the rocks formed in the later stage are mainly miarolitic syenogranite, mafic dykes and syenogranite porphyry dykes. According to the research, the early granite is I-type rock which is closely related to the westward subduction of Pacific plate in late Mesozoic, while the later granite is A-type rock,which represents the magmatic product from extension stage of Pacific plate after subduction.

Syenogranite dykes intruding granodiorite

Abundant dark micrograined enclaves in granodiorite

Partial mixing of enclaves and granodiorite compositions