四川南充盐盆下中三叠统杂卤石形成条件及找钾意义

Formation conditions of Lower-Middle Triassic polyhalite in Nanchong Salt Basin, Sichuan and its potassium prospecting significance

杂卤石(K_(2)SO_(4)·MgSO_(4)·2CaSO_(4)·2H_(2)O)是一种复盐,为盐类矿产中分布较为广泛的一种含钾矿物,在四川盆地三叠纪蒸发岩中广泛发育,并经常和其它钾镁盐矿物密切共生。由于杂卤石较其它钾镁盐矿物的溶解度低,易于残存保留,因此常被作为寻找钾盐矿床的重要标志和线索。其中南充盐盆嘉陵江组五段-雷口坡组一段(T_(1)j^(5)-T_(2)l^(1))的杂卤石分布面积最广,剖面揭露较完整,主要和纹层状硬石膏及菱镁矿、岩盐、"绿豆岩"等岩类共生,组成各种韵律层,根据岩矿鉴定、化学分析杂卤石还往往伴有微量的硫镁矾、无水钾镁矾等钾镁盐矿物。因此研究四川盆地三叠纪杂卤石分布特征、形成条件,对进一步寻找钾盐和指出找钾方向具有重要实际意义。

Polyhalite(K_(2)SO_(4)·MgSO_(4)·2 CaSO_(4)·2 H_(2)O)Magnesium salt minerals are in close symbiosis.Because polyhalite has lower solubility than other potassium-magnesium salt minerals and is easy to remain and remain,it is often used as an important sign and clue to search for potassium salt deposits.Among them,the polyhalite from the fifth member of the Jialingjiang Formation to the first member of the Leikoupo Formation(T_(1)j^(5)-T_(2)l^(1))in the Nanchong Salt Basin has the widest distribution area,and the profile exposure is relatively complete.It is mainly associated with Lamellar Anhudrite,magnesite、Rock Salt“Mung Bean Rock”and other rocks,forming various rhythmic layers.According to rock and mineral identification and chemical analysis,polyhalite is often accompanied by traces of magnesia,anhydrous magnesia and other potassium magnesium salt minerals.Therefore,studying the distribution characteristics and formation conditions of Triassic polyhalite in the Sichuan Basin has important practical significance for further searching for potash and pointing out the direction of potash.