陕西洛川黄土-古土壤剖面中伊利石结晶度——黄土物质来源和古气候环境的指示

CRYSTALLINITY OF ILLITE FROM THE LUOCHUAN LOESS- PALEOSOLSEQUENCE, SHAANXI PROVINCE——Indicators Origin and Paieociimate of Loess

伊利石是我国黄土和古土壤中最主要的粘土矿物。本文选择陕西洛川黄土-古土壤国际典型剖面为研究对象,通过测定伊利石的结晶度(Kubler指数)、Srodon峰强比值(Ir)和2M_1多型含量,发现黄土物质的起源与中高温(>280℃)地质环境有关;黄土样品中伊利石结晶度值为0.25°2θ(Cu Ka),古土壤样品中伊利石结晶度值大于0.27°2θ(Cu Ka);黄土和古土壤中伊利石结晶度值的差别,是由于古土壤中伊利石含少量的膨胀层,而黄土样品中的伊利石不含有膨胀层而引起的。古土壤中伊利石的膨胀层的成因,与伊利石在温湿的气候环境下发生退变有关。伊利石的结晶度值和Ir值可作为研究古气候环境变化的定量指标。

Illite is the most common clay mineral found in Chinese loess and its associated paleosol. The crystallinity (Kubler index), Srodon Ir and 2M1 polytype of illite from the Luochuan loess-pale-osol sequence indicate that the origin of loess-forming materials is related to the intermediate- and high-temperature (>280℃) geological environments. The illite crystallinities of loess and paleosol are 0. 25°△2θ and >0. 27°△2θ, respectively. The difference in illite crystallinity between loess and paleosol is due to the presence of a few expandable layers in illite in paleosol, while illite in loess samples contains no expandable layer. The origin of the expandable layers in illite of paleosol is related to the degradation of illite at a warm-humid climate. Therefore the crystallinity and Srodon Ir can be used as quantitative indicators of paleoclimatic fluctuations.