老挝万象平原含钾地层的岩相古地理

老挝万象平原的钾镁盐矿主要赋存在塔贡组下段膏盐岩亚段(E1 tg1-1)中。经对6条实测剖面、53个钻孔的岩石组合、沉积构造、岩石特征、地层厚度分析,塔贡组下段(E1 tg1)岩相古地理具如下特征:①含钾地层可划分为半深湖亚相、浅湖亚相、滨湖亚相、湖泊三角洲亚相。滨湖亚相可进一步划分出内带和外带;②钾镁盐矿产于半深湖亚相、浅湖亚相、湖泊三角洲亚相中,前者厚度较大;③万象成钾盆地为东深西浅的不对称盆地,盆地的古地理特征与现在的万象平原较为相似;④在沉积过程中,盆地基底由持续下降到逐步趋于稳定,卤水由逐步浓缩到迅速淡化,古气候由持续干燥炎热到湿热多雨,水体由弱还原向弱氧化环境变迁。

Lithofacies and Paleogeography of Potassium-bearing Strata in Vientiane Plane of Laos

The Kalium-magnesium deposits in Vientiane plain of Laos mainly exist in the lower segment of Thangon and the subsegment of salt-gypsum beds(E1tg1-1). After the analysis of rock association, sedimentary structure, rock characteristics and the formation thickness of 6 measured geological profiles and 53 drilling holes, its paleogeography has followed features: ①The potassium-bearing strata can be divided into four subphases, they are semi-deep lake, shallow lake, lakeshore, lake delta; and lakeshore subphase can be further divided into inner part and outer zone. ② Kalium-magnesium deposits exist in semi-deep lake subphase, shallow lake subphase, lakeshore subphase and lake delta subphase, the former one has larger thickness. ③The Vientiane Basin is asymmetric with its deeper east and shallower west, and its paleogeography characteristics is similar extremely to nowadays. ④In the deposition prosess,basin basement deceased continuously until gradually it tended to be stable. Brine is desalinated rapidly from it concentrated gradually, paleoclimate gets damp-heat and rainy from its early drying and hot, water changes from weak reduction to weak oxidation.