Petrogenesis and magmatic process of Late Cretaceous volcano-intrusive complex from Xiaoxiong Caldrea, Eastern Zhejiang Province

Xiaoxiong Caldera is a well-outcropped Late Cretaceous volcanic apparatus situated in eastern seashore of Zhejiang Province, which indicates the end of Mesozoic large-scale silicic volcanic activity of southeastern China. Rhyolite and syenite-porphyry were two important rock types of the volcano-intrusive complex outcropped in the caldera. Petrologic and geochemical studies showed that both of them had experienced different crystal differentiation processes, of which the syenite-porphyry were controlled by Augi-te+Apatite+Ti-Fe oxide differentiation while the rhyolite controlled by the differentiation of alkaline feldspar+apatite+zircon. Parent magmas of the both were originated from the remelting of the source crustal material but each had undergone a relatively independent evolution process, rather than the continuous magmatic evolution in one magma chamber. It is inferred that there should have some sub-magmatic chambers at different depths which contributed an integrated magmatic system beneath the Xiaoxiong Caldera and resulted in the variety of rock type. Thus it suggests that the intrusive rocks of the Late Mesozoic volcano-intrusive complexes in Southeastern China may probably not be supposed to the accumulate part of the lower magma chamber.