最近13万年来黄土高原黄土剖面中绿泥石的化学风化与古气候变迁

对黄土高原不同纬度地区的4个黄土—古土壤剖面和lO个现代土壤样品中绿泥石的化学风化进行研究，发现黄土—古土壤剖面中的绿泥石在最近13万年发生了明显的化学风化，其风化程度受剖面位置和气候控制；黄土—古土壤剖面中ω(绿泥石 高岭石)／ω(伊利石)的比值与磁化率之间具有良好的负相关关系，绿泥石的化学风化与古土壤中铁氧化物矿物的形成和磁化率的增强之间有成因联系；黄土高原现代地表样品中ω(绿泥石 高岭石)／ω(伊利石)比值与现代年平均温度和年平均降水量有着良好的相关关系。认为ω(绿泥石 高岭石)／ω(伊利石)的比值可作为新的指示夏季风变化的替代性指标，对于定量重建古气候的变迁历史具有重要意义。

CHEMICAL WEATHERING OF CHLORITE IN CHINESE LOESS-PALEOSOL SEQUENCES IN THE LAST 130 KA AND CLIMATE CHANGE

The weathering of chlorite from four selected loess-paleosol profiles in the last 130 ka and from modern soil samples on the Loess Plateau was studied. The variations of chlorite in clay fractions are quantified by the w(chlorite + kaolinite)/w(illite) ratio, corresponding to the ratio of the height of 0.7 nm peak and 1.0 nm peak in XRD diagrams. The results show that the w(chlorite + kaolinite)/w(illite) ratios recorded loess-paleosol alternations, and are negatively related to magnetic susceptibility. That is, the w(chlorite + kaolinite)/w(illite) ratio was consistently high for loess layers with low susceptibilities,and slightly lower in paleosol samples with higher susceptibilities.Furthermore,a good correlation between w(chlorite + kaolinite)/w(illite) ratio and climate parameters (mean annual temperature and precipitation) indicates a spatial gradient of chemical weathering intensity of chlorite closely related to summer monsoon circulation.It is suggested a dominant climatic control over chlorite distribution in loess-paleosol profiles,and that weathering of chlorite during the interglacial increased pedogenetic iron oxide minerals and thus enhanced magnetic susceptibility signal in paleosol. The w(chlorite + kaolinite)/w(illite) ratio can be used as a new proxy indicator to quantitatively reveal a long climatic history from Chinese loess-paleosol sequences.