A precise U-Pb zircon/baddeleyite age for the Jasra igneous complex, Karbi-Analong district, Assam, NE India

Abstract

Five Cretaceous alkaline-carbonatite igneous complexes are reported from the Assam-Meghalaya Plateau, These alkaline intrusions have been interpreted to be coeval and associated with the 117-105 Ma Ra­jmahal-Sylhet flood basalt province. With the existing age information it is possible that this alkaline magmatism may be a late magmatic stage of the Ra­jmahal-Sylhet large igneolls province. Therefore, it is essential to determine high.precision ages for these alkaline complexes in order to understand the de­tailed temporal evolution and genesis of this basaltic and alkaline magmatism. Out of five igneous complexes, Sung Valley, Swangkre and Samchampi have been dated, but tbe emplacement ages of the other two, i.e, Jasra and Barpung, are poorly constrained. The present communication reports a new, high­ precision U-Pb zircon/baddeleyite age for a djfferentiated portion of gabbro phase of the Jasra igneous complex.