Samples from the Horqin sandy land were exposed to a series of wind velocities,and sink particles were collected at the end of the diffusion section of a wind tunnel.Grain sizes of collected samples show great variation because of the granularity difference of the surface samples.The original samples show lower average content of SiO_(2) and higher average content of Al _(2)O_(3),Fe_(2)O_(3),MgO,CaO,Na_(2)O,and K_(2)O than collected samples.Compared with other dust source areas in China,the Horqin sandy land had higher content of Zr,Ba,SiO_(2),Al_(2)O_(3) and K_(2)O.Compared with the average upper continental crust(UCC)composition,surface samples were rich in the content of Y,Zr,Nb,Ba,La,Nd.Geochemistry characteristics of fine grain components of the Horqin sandy land differ from those from other dust source regions,because fine-grained particles in the Horqin sandy land were mostly derived from various local deposits formed in its unique depositional environments influenced by several tectonic activities.
The varicolored hills in the northern foothills of the Qilian Mountains of northern China,in the Hexi Corridor of Gansu Province's Sunan Yugur Autonomous County,have given this region a unique geomorphology.In this paper,we describe the elemental composition,lithological characteristics,and source type of the sediments that formed the varicolored hills.We found that the major oxides that make up their sediments are Si O2,Al2O3 and Na2 O.These sediments had higher Fe2O3,Mg O,Ca O,and Na2 O contents and lower Si O2,Al2O3,K2 O,and Ti O2 contents than in the major Fangyan rock group of the Jianglang Mountains Danxia landform and the red paleosols that have accumulated in the Yaojia Formation of the Songliao Basin.The varicolored hills have developed their strong coloration as a result of oxidation or reduction of Fe.Our data suggest that the sediments developed from terrestrial detrital deposits.
