Hobq Desert is located at the north of Yimeng Uplift of Ordos Plateau,facing the Hetao Plain.So the terrain is relative low in the north and high in the south.It is surrounded by the Yellow River from the east,north and west,and with narrow banding shape of east-west direction.It is 400km in length from east to west and 20～30km and 100km in width from north to south for the east and west part,respectively.The provenance of the Hobq Desert is still under great debates with views of ranging from erosion of surrounding mountains to desertification of local bedrocks,and to material supply from the Yellow River.The U-Pb age of detrital zircon is a powerful tool for source tracing.Totally 900 zircon grains from 9 samples,including 3 surface aeolian sand,2 lake shore sand,2 modern river bed sand and 2 Mesozoic sandstone,were collected to correlate the U-Pb ages provenance to trace the possible source of the Hobq Desert.The 2 samples from paleo-lake were dated by OSL and have age of 62.1± 8.9ka for KD-2 and 22.4±2.4ka for KD-4,which can be compared to the Hetao paleo-lake exposed below the desert.The results show that zircon U-Pb ages of the Hobq Desert sand are mainly distributed around 2.5Ga,1.9Ga,960Ma,450Ma and 280Ma.The zircon age distribution show obvious spatial variation pattern,which reflect eastward decreasing contribution (KD-1:41.6％,KD-3:40.2％ and KD-8:28.4％) of ＜450Ma peaks from the Yellow River and accordingly increasing contribution (KD-1:34.4％,KD-3:42.4％ and KD-8:56.8％) of ＞ 1.4Ga peaks from local sandstone material.The Hetao paleo-lake may have played an important role in mixing and holding the local source and the Yellow River contribution together for the eastern desert,which may be eroded and contribute the mixed material to the eastern Hobq Desert after its dying.By contrast,the western desert is sourced more from Yellow River contribution.In all,paleo-lake,rivers and wind activities have played their own roles in the formation of Hobq Desert.%库布齐沙漠的物源一直存在很大的争议,并存在周缘山脉侵蚀、就地起沙、黄河补给等诸多观点.碎屑锆石U-Pb年龄谱是物源示踪的有效手段.本研究在野外考察的基础上,通过对比沙漠不同地区地表沙及其潜在物源碎屑锆石的U-Pb年龄谱解析库布齐沙漠的物源.本研究采集了包括河套古湖的滨湖相细砂、沙漠底部基岩、黄河及其二级支流河道砂、沙丘表面沙等在内的9个样品,测试了其中900粒碎屑锆石的U-Pb年龄;同时还测定了2个古滨湖相样品的光释光年代.结果显示,库布齐沙漠碎屑锆石U-Pb年龄主要有5个谱峰,分别为2.5Ga、1.9Ga、960Ma、450Ma和280Ma,且在沙漠内部显示一定的空间分带性.其中3个沙漠沙样品显示了＞1.4Ga的古老锆石组分从自西向东逐渐增加的现象(KD-1:34.4％;KD-3:42.4％;KD-8:56.8％);同时,＜450Ma的年轻锆石存在自西向东逐渐减少的现象(KD-1:41.6％;KD-3:40.2％;KD-8:28.4％),这可能反映了库布齐沙漠东部地区本地物质的贡献大,而库布齐沙漠西部地区黄河沉积物的贡献较大.湖盆干枯后经风化剥蚀产生的沙粒,以及黄河携带的泥沙为库布齐沙漠提供了主要物质,湖泊、河流和风力活动在沙漠形成过程中可能各自扮演了重要的角色.
展开▼
