黄土高原黄土物源区的同位素证据

摘要

系统采集了黄土高原马兰黄土、河西走廊和青藏高原东北部黄土、河床沙和湖泥样品.用酸淋洗去除方解石后,黄土高原马兰黄土ε_(Nd)(0)值从-9.2到-11.3, ~(87)Sr/~(86)Sr比值从0.717 84到0.719 44,都落在同位素B区内,与青藏高原东北部、巴丹吉林沙漠和腾格里沙漠的值一致.黄土高原马兰黄土白云石的δ~(13)C值从1.2‰到1.5‰,与青藏高原东北部和河西走廊黄土,巴丹吉林沙漠的白云石的值类似.这些表明青藏高原东北部、巴丹吉林沙漠和腾格里沙漠可能是黄土高原黄土的源区,从而排除了其他沙漠(古尔班通古特沙漠、塔克拉玛干沙漠、毛乌素沙漠、库布齐沙漠、浑善达克沙地、科尔沁沙地和呼伦贝尔沙地)作为黄土物源区的可能性.同位素研究结果和野外调查进一步揭示,黄土高原黄土、巴丹吉林沙漠和腾格里沙漠物质可能最终都是来源于青藏高原东北部.%We have systematically collected the samples of the Malan loess in the Chinese Loess Plateau(CLP), the sand of ten deserts, the loess of the Hexi corridor, and the loess and sediments of riverbed and lake bottom on the northeast part of the Qinghai-Tibet Plateau. After removing calcites, the determined Nd and Sr isotopes of the Chinese Loess Plateau show that ε_(Nd)(0) from -9.2 to -11.3 and ~(87)Sr/~(86)Sr from 0.71784 to 0.71944. They fall within the B region of Nd-Sr isotope plot of provenances and are identical to those of the Badain Jaran Desert, the Tengger Desert and the northeast part of the Qinghai-Tibet Plateau. The determined C isotopes of dolomites of the Chinese Loess Plateau show that δ~(13)C from 1.2‰ to 1.5‰. They are identical to those of the Qaidam Desert, the Hexi corridor and the northeastern part of the Tibetan Plateau. These imply that the northeastern part of the Tibetan Plateau, the Badain Jaran Desert and the Tengger Desert may be the source areas of loess materials of the Loess Plateau, and that the possibility of the other deserts and sandy lands being the provenances of the loess is excluded, among them including the Gurbantunggut Desert, the Hunlun Buir sandy land, the Onqin Daga sandy land, the Horqin sandy land, the Hobqi Desert, the Mu Us Desert and the Taklimakan Desert. The field surveys further reveal the possibility that the materials of the Chinese Loess Plateau, the Badain Jaran Desert and the Tengger Desert are derived ultimately from the northeast part of the Qinghai-Tibet Plateau.