| Abstract: | Kekexili basin, located in Northern Qinghai—Xizang plateau, has an area of over 4000km\+2 and is the largest Paleogene land facies basin in the plateau. With NWW\|SEE trend, Kekexili basin extends along the north side of the Jinshajiang suture. Its sediments, Fenghuoshan group, formed in E 1—E 3, show a shape of wedge with big thickness in south and small thickness in north. There are four sedimentary facies; fan\|delta and alluvial facies that occur in south, lake and lake\|delta facies, which do in north, in this basin. The north\|dipping Jinshajiang normal faults on the south margin of the basin have controlled the developments of the basin. The S—N compression at the end of E3 strongly folded the basin strata and transformed Jinshajiang normal faults into thrusts. In N1, widespread denudation occurred in the whole plateau. During N 2—Q, Kekexili area uplifted along with the whole plateau, besides, the thrusts in the basin showed coherent activity. We propose a geodynamical model for explaining the basin development. In early E,India plate, due to its colliding Eurasia plate, stopped its ocean crust subduction northward, then the subducted ocean lithosphere breaking away made the south margin area, most possibly to the south of Jinshajiang suture, of Eurasia plate isostatically uplift, so the north\|dipping Jinshajiang suture acted as normal faults and controled the north basin development. In late E, the isostatic uplift finished, the basin also gradually terminated its development .At the end of E, Jinshajiang normal faults became thrusts and the basin strata were folded under the northward compression of India plate. In the N1, India plate started incontinental subduction, the lower crust and lower mantle lithosphere of Qinghai—Xizang area underwent more intensive compression and deformation than its upper crust, and the induced transversal expansion in the lower lithosphere uplifted the upper crust and decreased its horizontal stress, which conduced the upper crust undergo denudation. During N 2—Q, convective removal of the lower mantle lithosphere of Qinghai\|Xizang area led to rapid uplift of this area. |
