四川盆地东部三叠系嘉陵江组海相钾盐成矿分析及靶区预测

四川盆地是我国重要的成盐盆地,但是否能形成一定规模的钾盐矿床一直存在争议。本文以四川盆地三叠纪杂卤石成因-海相钾盐成钾条件分析-次级凹陷圈定-钾盐成钾靶区圈定为主线,利用光薄片鉴定、扫描电镜、Sr同位素、大地电磁测深及地震解译等手段分析了四川盆地三叠纪钾盐成矿潜力,并进行了资源量预测。四川盆地东部早三叠世嘉陵江期岩盐中赋存的杂卤石是自生的,是海水高度浓缩的产物,暗示岩盐沉积时古卤水浓缩已达到钾镁盐析出阶段,长寿双龙-合兴一带和垫江董家场一带可能存在有利于钾盐沉积的次级凹陷,后期构造运动对钾盐改造较小,保存条件较好。利用地震解释和大地电磁测深等结果初步圈定了长寿双龙-保合村勘查靶区,估算了资源量,为开展钻孔验证提供了科学依据。

Metallogenic conditions and target prediction of potash deposits in the Triassic Jialingjiang Formation, eastern Sichuan Basin

The Sichuan Basin is one of the most important salt basins in China; nevertheless, whether it can produce industrial marine potash deposit or not remains a problem of much controversy. In this study, with the source of polyhalite, the forming condition, the sub-depression and the prediction of targets of potash deposits as main lines, and on the basis of microscopic identification, scanning electron microscope, strontium isotopic composition, seismic interpretation and magnetotelluric sounding, the authors systematically analyzed the potential of marine potash resources in the Lower-Triassic Formation, and made a prospecting breakthrough of marine potash exploration in eastern Sichuan Basin. The authors hold that the polyhalite existent in halite in eastern Sichuan Basin is authgenic, and the seawater was highly concentrated and had reached the critical point of the potassium and magnesium salts precipitation in the early Triassic period. Two sub-depressions exist in the Diangjiang salt basin, i.e. the Hexing and Dongjiachang, and the potash salt in the sub-depression was well preserved and subjected to be less reconstructed by later tectonic movements. The results of the seismic interpretation and magnetotelluric sounding were used to delineate the exploration target area of Shuanglong-Baohe Village, and resources of potash salt were predicted, which should be useful for drilling verification.