Chronology and geochemistry of Mogutu granite in Inner Mongolia and its effect of crustal extension and thinning

The Mogutu granite pluton is emplaced in the southwest Huanggangliang to Ganzhuermiao tin-polymetal metallogenic belt in Southern Da Hinggan Mountains, which is mainly composed of biotite moyite. The genetic type, magmatic source region and diagenetic tectonic setting of the Mogutugranite were studied by U-Pb dating of zircon in LA-ICP-MS and petrogeochemical analysis. Zircon LA-ICP-MS dating of the biotite moyite yields a concordant age of 148.8-152.7Ma, which means that the Mogutu granite pluton was formed in Late Jurassic. The Mogutu granites is characterized by weak peraluminous and alkaline, high content of SiO₂ (73.64%-80.86%), K₂O(2.6%-6.0%), but low content of Al₂O₃ (10.57%-13.88%), depletion in P、Ti、Ba、Sr, and enrichment Rb、U、Th. The chondrite-normalized patterns of REE are in seagull forms, with strong negative Eu anomalies, with 0.10 to 0.27 of δEu, and higher zircon saturation temperatures(795-911℃), which indicates that the Mogutu pluton is similar to A-type granite. Therefore, the Moguto granites shows highly fractionated A -type granite affinity. Based on the previous research results, it is inferred that the depth of magma source of Mogutu granite pluton is shallow, the magmatic substance was derived from the crust, and the granite pluton was emplaced in the tectonic setting of crustal extension and thinning more likely related to the closure of the Mongol-Okhotsk tectonic belt.