Cretaceous Volcanic Geology And Tectonic Significance Of Dogarmo, Qinghai

Dogarmo area of Qinghai Province is located the intersection of Qilian, western Qinling, East Kunlun orogenic belt in northeastern edge of Qinghai-Tibet Plateau. The study of petrology, petrography and geochemistry in volcanic rocks of Dogarmo Basin investigated the basin tectonic settings, provided the information and evidence to reveal the northeastern margin of Tibetan Plateau evolution and the response process of deep.The volcanic rocks of study area is alkaline basalt, pyroclastic rocks and first discovered magnesian carbonatite. Paper initially defined the volcanic rocks are Early Cretaceous in age. Volcanic facies of study area are divided into effusive phases, overflow facies, intrusive facies, volcanic-deposition facies. The widespreaded overflow facies interbed with continental deposited red beds, so they are the contemporary resultant of eruption and sedimentary, and volcanic and sedimentary rocks showed a complete volcanic-sedimentary strata. According to the distribution of the characteristics of volcanic facies, combined with precision ground magnetic data, the whole volcanic apparatus presents the characteristics that individuals are small in scale, but larger in number, controlled by regional faults and has fracture-center eruption. Through the analysis of the major elements, REE and trace element of the data to the Dogarmo volcanic, combining with the applicable discrimination diagrams, paper determine the rocks belong to Na-rich alkaline volcanic series. They only have a small amount of crustal material contamination, and the formation of the tectonic environment is continental rift. So Dogarmo basin is a continental rift basins, because of the northward subduction of Tethys oceanic crust, the basin was squeezed in north-south and pulled in east-west. The location of the basin firstly formed north-south rift, with the deepening of fracture, the upwelling mantle material formed basalt at the surface. After the cessation of volcanism and the heat supply disruptions, the rock occurring shrink cause the magma chamber empty and settlement, so the Dogarmo Basin with depression in late properties.