Chaerhan Salt Lake Surrounding Sand Sediment Particle Size And Heavy Mineral Characteristics

Qarhan salt lake is the depocenter and catchment of the basin, which is in the central south part of the Qaidam Basin, the southern of Qarhan salt lake near the Kunlun mountains, the northern next to the Xitieshan and the Luliangshan, which are the branch range of Qilian mountains, the west is reaching to Taijinar salt lake, the east is adjacent to the Qaidam river. Its climate is a typical kind of continental desert climate, which is characterized by high altitude, low temperature, rare precipitation. Therefore, the wind-sand activity is frequently which lead to that the distribution of Aeolian landform is widely in Qarhan salt lake area, the important information of the formation and evolution for the Aeolian landform recorded in the characteristic of grain size, which can explore the sources of sedimentary and also analysis the deposited environment. In order to do the research, based on field investigation, the author collected the sedimentary of different regions, different landform types, different positions of landform, according to the theory of Aeolia geomorphology; the author analyzed the characteristic of grain size, mineral composition. The main conclusions are following:(1)The grain size composition analysis shows that the sediments of the area is mainly comprised of medium and fine sand, the frequency curve is unimodal, the peaks, range of grain size is similar in different regions, but it is broad in the different landform types.(2)The grain size parameters shows that the mean grain size of the southern is finer than the northern, the difference of grain size parameters is obviously in different regions and landform types. The trend of grain size parameters varied with the depth is clear.(3)The study of the relation between grain size characteristic and the downwind direction shows that it is unclear in large scale range of different landforms, but with the downwind direction in small scale range, the mean grain size became finer, the sort is better.(4)The deposited environment of the sedimentary in the area is very complicated, the main deposited environment is Aeolian, the following is lacustrine, deltaic, diluvial, lakeshore. The environment of surface sediments is mainly Aeolian and lacustrine facies, its distribution haven, t regional, but with the depth the deposited environment is stratified.(5)The mean content of heavy minerals of the sediments in the Qarhan salt lake area is0.88%,the variation of the heavy mineral content is broad. The types of heavy minerals in the area are various. The assemblage of the stability of heavy minerals is dominated by unstable mineral, the proportion of extremely stable mineral is lest, but the kind is the most. The characteristic index analysis of different regions, different landform types and different positions shows that the heavy mineral is complicated and the distance form the provenance is different. The rock of the provenance is uniform, but is also related to the geological structure of the surrounding mountains.(6)In contrast with Badan Jaran Desert and Tenngger Desert, the sediments in the area surrounding to Qarhan salt lake are finer, but the content of heavy minerals is higher. So it seem that the Aeolian sand in the research area came form the fluvio-lacustrine deposits formed in the tertiary and quaternary period in the Qaidam Basin.