青海察尔汗盐湖别勒滩区段杂卤石成因及其成钾指示意义

The Origin of Polyhalite and Its Indicating Significance for the Potash Formation in the Bieletan Area of the Qarhan Salt Lake,Qinghai

别勒滩区段位于青海察尔汗盐湖西部,前人认为察尔汗盐湖固体钾盐矿物以光卤石为主,在别勒滩区段西部发现有杂卤石,但并未引起足够重视,对杂卤石成因未做详细研究。本文通过对别勒区段七个钻孔样品的矿物鉴定及地球化学分析,发现别勒滩区段杂卤石以原生和准同生交代方式赋存,且以后者为主,多交代石膏等硫酸盐矿物产出,少量出现交代石盐现象。杂卤石主要分布于别勒滩中西部地区,整个别勒滩区段自西向东出现了以杂卤石为主渐变为以钾石盐—光卤石为主的分布规律。结合别勒滩区段晶间卤水的补给条件,研究认为别勒滩区段杂卤石形成是涩聂湖硫酸镁亚型湖水与先期形成的盐类矿物发生交代反应的结果。别勒滩地区杂卤石作为典型的陆相成因,对研究海相蒸发岩矿床中普遍存在的杂卤石成因具有一定的对比借鉴意义,海相蒸发岩矿床中的杂卤石可能是盆地形成的内陆盐湖湖水与早期沉积的盐类矿物发生交代反应形成,对寻找海相钾盐有一定的指示意义。

The Bieletan section is located in western Qarhan Salt Lake,and there are 1.8bt low assay solid potassium in S4 salt layer.This paper studied mineral identification and the geochemical analysis of seven cores samples from the Bieletan section.The polyhalite is in the presence of two modes：primary orign and penecontemporaneous replacement.Polyhalite mineral shows the phenomenon distributing around the lake,and polyhalite was formd by replacement with gypsum and other sulfate minerals,or even with halite.Studies suggest that the formation of polyhalite related to supplies of magnesium sulfate subtype brine.The polyhalite in the Beletan area reveals the mineral polyhalite commonly occurs in marine evaporite deposits formed by metasomatic replacement brine of land facies lake with early formed saline mineral.Therefore,the origin of polyhalite mineral in the Bieletan area has some indication significance for finding marine potash deposit.