用泥岩中碳酸盐氧同位素组成确定柴达木盆地东部第四系剥蚀厚度

Calculation of tectonic uplift of eastern Qaidam basin in Quaternary: Depending on the oxygen isotopic compositions within mudstone.

泥岩是一种较好的“封闭体系”，当孔隙水中有大量的ＨＣＯ－３来源时，其中的碳酸盐沉淀形成自生方解石矿物。因此，利用这些自生矿物中的氧同位素组成（δ１８Ｏ值），来推算其形成时的地温及深度，再综合其它资料，可定量计算构造的相对抬升量和剥蚀的厚度。柴达木盆地东部在喜马拉雅造山运动的作用下，第四系形成了一系列背斜构造，其顶部受到了不同程度的剥蚀。将氧同位素地球化学方法运用于该地区，计算出的构造相对抬升量和剥蚀的厚度与大地构造背景相符，可以为研究该区天然气的聚集成藏史、聚集程度和寻找勘探目标提供依据。

Carbonate could be precipitated as authigenic calcite mineral in the pores in case of that pore has enough HCO 3 - ions since mudstone should be an enclosed system. Our studies suggest that the depth and geotemperature when and where the authigenic mineral generated should be inferred depending upon the stable isotopic compositions ( δ 18O values) within the minerals, meanwhile, the relative lift and denudated thickness of the structures could be quantitatively calculated by using other information comprehensively. Under the effect of Himalayan orogeny, a series of anticlinal structures were formed and their tops were denuded in a different degree in Quaternary, in eastern Qaidam basin, Northwest China. The oxygen isotopic geochemistry has been used as a tool for calculating in this area and the results suggest that the calculated relative lift and denuded thickness of the structures correspond to the geological background of tectonic system. The research would afford useful and advantageous information for studying natural gas accumulation and trap forming history, accumulation extent, and for searching exploration targets.