【摘要】 古尔班通古特、腾格里和鄂尔多斯三个沙漠不同粒级组分的风成沙具有不同的εNd(0)和87Sr/86Sr比值:古尔班通古特沙漠中分别为-3~-5.3和0.712452~0.716895;腾格里沙漠中分别为-9.9~-12.3和0.716753~0.723033;鄂尔多斯沙漠中分别在-13.1~-18和0.714028~0.71678。三个沙漠不同的Sr-Nd同位素特征,表明它们可能有各自的物质源区。Nd同位素主要受各沙漠所处的地质、地貌单元所控制,Sr同位素还要受气候变化诱导的矿物差异风化与粒度分选作用的影响。同位素组成在古尔班通古特、腾格里沙漠风成沙不同粒度组分中有相似的变化规律,但在鄂尔多斯沙漠中明显不同。鄂尔多斯沙漠风成沙粗、细颗粒组分有不同的物质来源,细颗粒组分,特别是<2μm组分可能有沙漠区外远源的贡献,而其他沙漠各自的风成沙不同颗粒组分则来自相同的物源区,沙漠区外远源输入的可能性较小。这一研究对深入认识北方沙漠物质的成因机制有重要的理论意义。更多还原

【Abstract】 Sr-Nd isotopic compositions of different grain-size fractions of eolian sand samples collected from Gurbantunggut, Tengger and Ordos deserts are investigated in detail. TheεNd(0)and Sr/86Sr values vary from -3 to -5.3 and from 0.712452 to 87 0.716895, respectively in the Gurbantunggut desert, between -9.9 ~ -12.3 and 0.716753 ~ 0.723033, respectively in the Tengger desert, and between -13.1 ~ -18 and 0.714028 ~ 0.716780, respectively in the Ordos desert. These desert sands with different Sr-Nd isotopic ratios imply their distinct provenances. The Nd isotopic values of eolian sands are dependent on geology and relief of the deserts. The Sr isotopic ratios of eolian sands are affected not only by geology and relief of the deserts, but also by particle sorting and mineral weathering. The isotopic compositions of different particle-size fractions of eolian sands in the Gurbantunggut desert have similar variations to those in the Tengger desert, but distinct from those in the Ordos desert. Fine and coarse sands in the Ordos desert have different sources, of which, the fine sand (especially the < 2 μm fraction) perhaps came partially from foreign sources. However, different grain-size fractions of eolian sands in other deserts have same provenances without the input of foreign sources.更多还原