The discovery of Early Triassic volcanic rocks in Zhanhongshan area of Qinghai Province in the eastern section of East Kunlun Mountain and its geological significance

During 1:25000 regional geological and mineral resources survey in Zhanhongshan area of Gouli Township, Dulan Country, Eastern Kunlun Mountain, conducted by the authors, a set of Early Triassic volcanic rocks was mapped.The rocks consist mainly of a set of acidic volcanic rocks with local limestone assemblage, characterized by marine eruption.The main elements of volcanic rocks suggest weakly peraluminous rocks such as medium-K to high-K calc-alkaline series, assuming LREE-enriched pattern.The REE distribution pattern shows medium Eu anomaly, enrichment of LILE K, Rb, Ba and Th and depletion of HFSE Ti, Nb and Ta.The tectonic environment shows characteristics of island arc volcanic rocks.The zircon LA-ICP-MS U-Pb age of rhyolite is 244.1±1.8 Ma.It is believed that the volcanic rocks were formed in the Early Triassic.Combined with regional tectonic evolution of East Kunlun, it is considered that the acidic volcanic rocks in the Zhanhongshan area were associated with large-scale island-arc granites in the eastern part of East Kunlun, and they were formed by magmatic activity during the northward subduction of the Early Triassic in Animaqin of Paleo-Tethys Ocean.It seems to be a fine example of volcanic activity during the Late Permian to Early Triassic in the East Kunlun area after the discovery and establishment of the Late Permian Dazaohuo Formation in the middle part of the East Kunlun Mountain.