The Formation Age And Geochemistry Characteristics Of The Late Mesozoic Volcanic Rock In Tuliemaodu Area,Inner Mongolia

This passage presents the Late Mesozoic era in the area of Inner Mongolia, Manketou, Obo Formation, Manitu Formation and Baiyingaolao Formation, Meiletu Formation volcanic rocks, the research of petrology, zircon u-pb dating, chronology, geochemistry, and finds the composition of the rock, the distribution and the timing of forming for the volcanic rocks, and also talk about the environment of forming the Late Mesozoic era volcanic rocks, provide the evidence for the study of Great Xing’an Range Mesozoic volcanic rocksThe results of zircon u-pb dating show Manketou Obo Formation,Manitu Formation, Baiyingaolao Formation, Meiletu Formation volcanic rocks have formed in 140±2Ma、127±2Ma、130±2.7Ma、128±3~130±1Ma independently, Which reflects the tuliemaodu area exists in the late Mesozoic volcanic magmatic activity and magmatic activity time from Late Jurassic to early Cretaceous.Volcanic rocks of Tuliemaodu area in Late Mesozoic are acidic-intermediate to acidic volcanic rocks, pyroclastic rock, rhyolite, andesite, dacite etc, which show in calc-alkalinelight, rare earth rich macroion lithophile element, Lack of high field strength elements of Nb、Ta、P、Ti in petrology. The demonstrations in geochemistry are continental margin arc, which shows the forming environment of these rocks are active continental margin.Four group of volcanic rocks forming in the Tuliemaodu area were all affected by the subduction of Paleo-Pacific Plate. Late Jurassic, subduction of Paleo-Pacific Plate makes the crust thicker. Early cretaceous, the tectonic setting of the study area is transformed from compression to extension. The thicken lithosphere mantle become thinner, which results the asthenosphere mantle rise and become the large scaled magmatism.