LA-ICP-MS zircon U-Pb dating and geochemical characteristics of the porphyroclastic lava in Maodeng area of Inner Mongolia

The porphyroclastic lava with the texture of both lava and ignimbrite was found for the first time in Maodeng area of Inner Mongolia. The Maodeng porphyroclastic lava body，occurring as an oval dome，can be divided into internal facies，transitional facies and external facies. Based on the field geological investigation and the LA-ICP-MS zircon U-Pb age，the authors hold that it was produced by volcanic and magmatic activities in Early Cretaceous. The rock is characterized by enriched Si，alkaline and LREE，with relatively strong negative Eu anomaly，high Rb and Th content and low Ba and K. It resembles the liparite of the same period in geochemical characteristics. It is suggested that the porphyroclastic lava body was formed in an intra-plate anorogenic extensional setting.