塔西南坳陷中新生代蒸发岩沉积初探

通过资料搜集、蒸发岩野外露头地质调查、石盐岩沉积特征分析及盐类矿物学研究,对塔里木盆地塔西南坳陷中新生代蒸发岩的分布、层位、盐类矿物组合、成因进行了初步探讨。塔西南坳陷石盐岩沉积呈透镜体状,主要沿西昆仑山前分布,常含有褐红色、灰绿色泥砾,泥砾岩性与吐依洛克组下段岩性一致,推测应为吐依洛克组沉积晚期海退期成盐,其层位应归属于吐依洛克组上段。石盐岩透镜体在横向分布上不连续,反映了当时塔西南坳陷内部可能存在多个古盐湖次级凹地,其在干旱气候条件下经浓缩蒸发成盐。蒸发岩矿物除石盐、石膏外,还见有杂卤石、钙芒硝等,其中杂卤石可能为后期富钾卤水交代原生石膏的产物,而乌泊1井石盐表面大量的次生钙芒硝可能为盐湖后期石盐析出阶段含钙地下水缓慢持续补给盐湖的产物。

Preliminary study of evaporites deposition from the Mesozoic to Cenozoic in southwestern Tarim Depression

Based on the previous data,the fieldwork on evaporite outcrops,the halite sedimentary characteristics and the salt mineralogy study,it preliminarily discussed the distribution,the occurrence strata,and the salt mineral assemblages and genesis of the Meso-Cenozoic evaporites in the southwestern Tarim Depression. The Lens-shaped halite mainly distributed along the front of west Kunlun Mountain,and usually contained maroon or celadon muddy gravel. The lithology of halite is the same as that of the lower member of Tuyiluoke Formation. So,the halite is speculated to form during the regression of late depositional period of Tuyiluoke Formation,and its strata belonged to the upper member of Tuyiluoke Formation. The laterally-discontinuous halite lenses indicated the possible existence of multiple sub-depressions of palaeo-salt-lakes,which were evaporated and formed halites under an arid climate. The evaporite minerals were mainly halite and gypsum,as well as some polyhalite and glauberite. The polyhalite in gypsum may be the products of primary gypsums replaced by late potassium-rich brine;while the secondary glauberites,discovered on the halite surface in Well Wubo 1,were probably formed during the supply of calcium-rich groundwater to the salt lakes after its precipitation of halites.