THE XIDATAN MELANGE IN THE SOUTHERN MARGIN OF EAST KUNLUN MOUNTAINS
东昆仑南缘西大滩混杂堆积

The Xidatan melange occurs in the fault-compressed zone of the southern margin of the East Kunlun Mountains, near the Kunlun pass, extending both east-and west-wards to a certain degree.The southern side of the melange is covered with the glaciers in the Kunlun Mountains, while the northern one is cut by a granite-porphyry body. It is exposed 1000 m in width and from south to north divided into three layers as follows.1. The exotic block layer of single composition: The exotic blocks are of only one rock type, i. e. sandstone occurring mostly as lens, while the matrices with clear bedding are grey-black argillaceous sandstone or arenaceous shale.2. The exotic block layer of two compositions: The exotic blocks are angular sandstone and limestone, while the matrices are grey-black arenaceous and argillaceous sediments. Both the blocks and matrix have been sheared and broken.3. The exotic block layer of several compositions:Besides sandstone and limestone, the exotic, blocks consist of conglomerate, granite, turbidite and slate. The matrices appear as"match sticks"in shape due to weathering.There are transitional relations between the three melange layers.The authors consider that the Xidatan melange belt is an olistostrome and the melange resulted from plate tectonic movements. According to the fossils found in the blocks and matrices of the Xidatan melange belt, the belt is considered to be formed during the Indo-Sinian period.