Zircon U-Pb dating and petrogenesis of the rhyolitic porphyroclastic lava in Chaihe area, Daxinganling mountains

In order to study the formation age and petrogenesis of the rhyolitic porphyroclastic lava in Chaihe area, Daxinganling mountains, ziron U-Pb isotopic dating and geochemical analysis were used. LA-ICP-MS zircon U-Pb dating results show that Chaihe rhyolitic porphyroclastic lava formed in early cretaceous from 135 to 138 Ma. The geochemical study show that characteristics of the rhyolitic porphyroclastic lava have high silicon and alkalis, poor calcium and magnesium. The total REE abundances ranged from 150.1×10-6~191.5×10-6, highly fractionated LREE from HREE[m(La)/m(Yb)N=11.8~14.45] and negative Eu anomalies (δEu=0.59~0.75). The trace elements are characterized evidently by enrichment of Rb, Ba, K, strong depletion of Nb, P, Ti. The geochemical characteristics show similarity with the I-type granite. The porphyroclastic lava's original magma is chiefly derived from partial melting of crust.