Material composition characteristics of fine particles of eolian sand in Horqin Sandy Land and its indication to provenance
The Horqin Sandy Land is the largest semi-fixed sandy land in northern China.Tracing its material sources is of great importance to understand the formation and evolution of deserts and reconstruct the migration paths of fragments.Therefore,the composition of fine particles(＜63 μm and＜11 μm)of eolian sand in the Horqin Sandy Land was analyzed by petrology,elemental geochemistry,Sr-Nd isotope,TIMA automatic miner-al identification and U-Pb dating of detrite zircon.The material composition of the Horqin Sandy Land was char-acterized and its provenance was quantitatively constrained.The geochemical indicators show that the Horqin Sandy land has experienced low chemical weathering and fractional recycling degree.The heavy mineral assem-blages are mainly ilmenite,epidote,zircon,garnet,magnetite+hematite limonite,which together with the dis-criminant diagram of geochemical motherrock indicate that the sediments in the Horqin Sandy Land are mainly derived from medium acid magmatic mother rocks.Further constrained by Sr-Nd isotopes,the main source areas are the southern margin of the Central Asian orogenic belt and the northern margin of the North China Craton,and a small amount of dust originates from the northern border desert of China.The U-Pb ages of detrital zircons in sandy land are mainly from Mesozoic to Late Paleozoic(200-600 Ma)and Paleoproterozoic(1 518-2 000 Ma and 2 200-2 600 Ma).The comparison with the zircon age spectrum of the potential source area shows that the fine particles in the Horqin Sandy Land contain both near-source material from the Greater Khingan Moun-tains in the southern margin of the Central Asian orogenic belt by wind and river transport,and ancient bedrock from the Yanshan Mountains in the northern margin of the North China Craton by river transport.Quantitative provenance results of inverse Monte Carlo model show that the Central Asian orogenic belt contributes 53.7％and the North China Craton contributes 46.3％.The synergistic effect of wind and river explains the formation of fine particles of wind-sand in the Horqin Sandy Land.
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