柴达木盆地西部膏盐岩发育特征与成因分析

Characteristics and genesis of gypsum-salt rocks in western Qaidam Basin

通过对柴达木盆地狮子沟地区膏盐岩的岩石学及纵向和横向的分布和发育特征进行研究,探讨该区膏盐岩的沉积环境和成岩条件,总结成因模式。研究发现,狮子沟地区膏盐岩层发育在内陆咸化湖半深湖—深湖相中,该时期处于温度由炎热向温暖转变,半干旱向干旱过渡的古气候环境。狮子沟地区膏盐岩纵向上具有4种沉积序列,横向上与砂岩呈"此消彼长"的关系,与泥岩呈"同增同涨"的关系。该区膏盐岩沉积的成因模式为"深水成盐"模式。在渐新世(E3),地下深部热卤水通过处于活动期的深大断裂上涌,盐类物质在狮子沟地区遇冷过饱和,快速堆积成岩。

Through the study on petrology and distribution characteristics of gypsum-salt rocks, with sedimentary environment and diagenetic condition of gypsum-salt rocks, genetic model of gypsum-salt rocks was ana- lyzed in Shizigou area of Western Qaidam Basin. Gypsum-salt rocks have four sedimentary sequences vertically, they had inversely proportional relationship with sandstone, and had proportional relationship with mudstone in the lateral. The genetic model of gypsum-salt rocks is salt deposited in deep water. There were sub- tropical climate to temperate climate in depositional stage of gypsum-salt rocks in Qaidam basin, the tempera- ture reduced and humidity changed from semiarid to arid at that stage. It was low-lying areas of lake basin in Shizigou area, there was interval and systole of the water volume. Deep fault was active sharply, as channel of deep brine upwelling in quantity, evaporite materials were sedimentation with cold weather and saturation.