江陵凹陷沙市组上段石盐包裹体测温学研究

Homogenization temperature study of salt inclusions from the upper section of Shashi Formation in Jiangling depression

对江陵凹陷古新统沙市组盐湖沉积中的石盐进行了包裹体显微测温和氢氧同位素测定。测试结果显示,江陵凹陷沙市组上段石盐包裹体均一温度范围为18~50℃,主要集中在22~38℃;包裹体δ18O同位素值变化范围为-1·2‰~9·7‰,均值5·1‰;δD同位素值变化范围为-91·5‰^-63·5‰,均值-79·4‰。这与当时整体热的古气候特点相吻合。同层石盐层的中下部包裹体的均一温度和氢氧同位素值均偏高,上部包裹体的均一温度和氢氧同位素值均偏低。这一认识对研究盐湖演化阶段、石盐成因以及预测钾盐成矿的地质时代和层位都有极为重要的意义。

Owing to Yanshanian and Himalayan movement, a series of downfaulted basins were formed in late Cretaceous-Paleogene, when Paleocene halite of salt lake deposition was formed in Shashi Formation of Jiangling depression. Homogenization temperatures of the inclusions in Paleocene halite of Jiangling depression vary from 18 to 50℃, mainly in the range of 22-38℃ ; the 9180 values of the inclusion are between - 1.2‰ and 9.7‰, with an average of 5. 1‰; the δD values vary from - 91.5‰ to - 63.5‰, - 79.4‰ on average. These data are consistent with the thermal features of paleoclimate in that period. However, the homogenization temperatures of inclusions and the H-O isotope values are relatively high in the middle-lower halite layer and relatively low at the top of the same halite layer. This understanding of paleoclimate has important significance for the study of the evolutionary phase of salt lake, the halite origin and the prediction of geological stages and strata of potash salts.