西藏地球化学填图及其意义

Geochemical Mapping in Xizang (Tibet) and Its Significances

本文介绍谢学锦先生快速进行区域地球化学填图的计划在西藏取得的成果。区域水化学填图可分析66个指标,效率高,成本低,见效快;同时水化学填图的空间定位和分辨率比采集土壤样品的填图会差一些。西藏地球化学填图成果呈现了一定的规律性,例如西藏66种元素的地球化学图中,有三分之二沿雅鲁藏布江缝合带出现异常带。西藏许多元素的分布受雅鲁藏布江缝合带影响,是因为特提斯洋原有的一些元素残留在雅鲁藏布江缝合带两侧。氧化钾、氧化钠沿雅鲁藏布江缝合地带出现含量高的异常带,可见特提斯洋中丰富的钾、钠成分残留在代表大洋封闭的雅鲁藏布江缝合带两侧。沿雅鲁藏布江缝合地带氧化钙出现含量低的异常带,可用特提斯洋中的碳汇作用来解释,即特提斯洋中的钙由于碳汇作用变成碳酸盐岩石,氧化钙出现含量低的异常。西藏的地球化学图对矿产勘查和生态环境研究也具有一定意义。

This paper introduces the efficient geochemical mapping project that was proposed by Prof. XIE Xuejin in 1990s and shows its resulting maps of element distribution. It used water chemical sampling and analysis to obtained 66 geochemical quantities. This method enjoys efficient and fact mapping process, but with lower spatial resolution comparing to the deep soil sampling. The resulting maps in Xizang（Tibet） show some regularity of elements distribution, as 2/3 maps have anomalies located along the Yarlung River Suture . The reason of this elements distribution patterns involved with closing of the Tethys Ocean that contained some rich elements and left along the Yarlung River Suture, causing high contents of K2O and Na2O. On the other hand, it also caused low content of CaO, due to the carbonate deposition in the Tethys Ocean . The resulting maps in Xizang（Tibet） may have significant also for mineral exploration as well as environmental and ecology studies.