西藏中西部风成沙的地球化学特征

 研究区位于青藏公路以西、雅鲁藏布江以北。这里存在着明显的风成沙搬运和堆积现象。大部分地区的风成沙中缺失-2～+0.9 mm粒级段，优势粒级出现在-0.3 mm粒级段中，比例高达85%以上。多数样品中元素含量分布均表现出从粗至细粒级逐渐降低，在-0.45～+0.3 mm或-0.3～+0.2 mm粒级降至最低；然后，向细粒级方向含量再次升高。Hg则从粗向细粒级含量逐渐增高，中间变化很小。但在风成沙来源地有矿区存在时，则出现相应元素的明显升高。藏北双层风成沙丘中两层沙子各粒级中元素含量没有明显差异（Hg除外）；推测两次堆积的风成沙来源地是一致的。

Geochemical Features of Eolian Sand in Central and Western Tibet

The study area locates in the west to Qinghai-Tibet highway and in the north to Yarlung Zangbo River.There are a great of eolian sand distributing in the area.The grain feature of the eolian sand is that the main grain section appears in 60 meshes with a high proportion of 85%,and the shortage grain section in -10~ 20 meshes in most area.The trace element content in most eolian sand firstly decreases gradually as the grain size of eolian sand decreases,and reaches at the lowest in -40~ 60 mesh or -60~ 80 mesh,then lightly increases when the grain sizes are less than -40~ 60 meshes or -60~ 80 meshes.Whereas the Hg content in eolian sand generally shows an increasing tendency from coarser grade to finer grade.Occasionally,when mining area occurs in the source area of eolian sand,the indicator element content obviously increases.In the double-deck eolian sand hillock located in the Northern Tibet, the trace element contents in the two layers have not obvious discrepancy except Hg element,which indicates the two layers probably come from the same source.