The establishment of Early Carboniferous Wangguoshan Formation in Gangmar Co-Riwanchaka area, central Qiangtang, Tibetan Plateau

The Wangguoshan Formation developed in the Lungmu Co-Shuanghu Lake-Lancang River suture zone is a suite of Early Carboniferous basic-acid volcanic sedimentary strata consisting of volcanic breccia，volcanic tuff，andesite，rhyolite and minor basalt，has the features of polycyclic eruption，and is conformably overlain by the Early Carboniferous Riwanchaka Formation. On the whole, these strata are a set of marine facies volcanic sedimentary strata near the volcanic vent and exhibit Yangtze attribute. The andsesite of the Wangguoshan Formation in the Qingshanliang area has a LA-ICP-MS U-Pb zircon concordia age of 350Ma±1Ma. In combination with the youngest peak numerical value of sandstone detrital zircon in the Early Carboniferous Riwanchaka Formation, the authors hold that the Wangguoshan Formation should have been formed in the Early Carboniferous Tournaisian. The establishment of the Wangguoshan Formation has important geological significance for the completion of the stratigraphic system in Lungmu Co-Shuanghu tectonic-stratigraphic area and the discussion of the evolutionary history of the Lungmu Co-Shuanghu-Lancang River Ocean.