新疆表壳元素地球化学特征

Elemental geochemistry characteristics of the supra-crust,Xinjiang,China

本次研究以国家"305"项目新获得积累的新疆地球化学勘查数据为基础,以岩石地层分区为框架,按照岩石地层单元出露情况,利用面积加权方法,在地理信息系统和数理统计分析系统下,对新疆及其三个主要地层区——塔里木地层区、中南天山-北山地层区和北疆地层区进行了39种元素的表壳元素丰度计算。计算结果显示新疆及其三个主要地层区表壳元素丰度总体表现出上陆壳的特点,但又各具差异,反映出新疆地壳的不均一性,塔里木地层区主要表现出成熟上陆壳,北疆地层区表现为年轻上陆壳,中南天山-北山地层区则呈现过渡特点。通过统计、对比,本次研究指出新疆表壳元素丰度受岩石地层单元元素丰度和岩石地层单元地表出露面积控制,其变化是地壳演化历史的产物,总体上并不服从正态分布,前人利用迭代剔除法获得的结果是值得商榷的。

Based on the data of geochemical exploration, accumulated by National 305 Project, the framework of petrological strata, the consideration of the exposed area of petrological strata, the method of area weight average and the support systems of GIS and statistics, the 39 elements area weight averages of Xinjiang supra-crust and its three main petrolical strata regions （Tarim strata region, Beijiang strata region and Mid-south Tianshan strata region） are calculated. The results point out that the supra-crust of Xinjiang and its three main petrological strata all have the characteristics of upper continent crust on element contents, but the three petrological strata regions have their own characteristics. These special characteristics show the crust of Xinjiang is not uniform, Tarim strata region has characteristics of adult upper continent crust, Beijiang strata region has characteristics of young upper continent crust, and Mid-south Tianshan strata region has characteristics between Tarim strata region and Beijiang strata region. In light of the comparison and analysis, it can be pointed that the element contents of supra-crust of Xinjiang are controlled by ptrological strata and the exposed areas of petrological stratum units, the variations reflect the crust evolution, the distribution of element contents mainly are not according to normal distribution, so the results coming from the total sample statistics and iteration pick-out method should be reconsidered.