四川盆地东部垫江盐盆三叠系海相钾盐成钾有利区圈定： 地球物理和地球化学方法综合应用

垫江盐盆是四川盆地三叠纪时期重要的一个成盐成钾次级盆地,在早三叠世嘉陵江组四段岩盐中发现了大量含钾矿物,具备成钾潜力,但海相钾盐成矿有利区还需要进一步研究.本文通过系统收集垫江盐盆内已有钻孔资料,对嘉陵江组四段岩盐厚度进行统计,对嘉陵江组四段钻井岩盐样品进行化学成分分析,结果表明在双龙地区和五洞地区岩盐厚度大,岩盐钾含量较高,可能是古盐湖蒸发浓缩中心;对垫江盐盆内3条地震剖面进行重新解译,并开展了7条大地电磁测深剖面测量工作,结果显示早三叠世嘉陵江期在垫江盐盆北段的五洞地区和南段的双龙地区可能存在有利于钾盐沉积的凹地,地球物理和地球化学结果较为一致.综合分析认为,早三叠世嘉陵江期,垫江盐盆北段的五洞镇一带和南段的双龙一带是海相钾盐成矿的有利区,研究结果可为进一步开展钻孔验证提供科学依据.

Delineation of favorable potash forming areas of the Triassic marine potash in the Dianjiang salt basin, eastern Sichuan: application of geophysical and geochemical methods

The Dianjiang salt basin is one of the most important Triassic Potash- forming sub- basins in the eastern Sichuan basin, where a large number of potassium- bearing minerals have been found within the halite in the fourth member of the Jialingjiang Formation (T 1 j 4). Nevertheless, the favorable potash- forming areas of marine potash still remain elusive and need further study. Based on the systematic collection of the drilling well datain the Dianjiang salt basin, this paper calculated the salt thickness of the T 1 j 4 and analyzed the chemical components of the halite samples. Results show that the salt thicknesses of the Shuanglong area and the Wudong area are the highest. Within these two areas, the potassium content of halite shows a distinctive high level, suggesting that the probable ancient salt lake evaporation and concentration centers of the Dianjiang salt basin were in the Changping and the Wudong areas. Moreover, we reinterpreted three seismic profiles across the Dianjiang salt basin, and employed the magnetotelluric sounding studies on another seven sections. These reveal that the significant sub- depressions favouring potash deposition during the period of Jialingjiang Formation likely exist in the Wudong part in the northern Dianjiang salt basin and in the Shuanglong part in the southern Dianjiang salt basin. This geophysical observation is in good agreement with the geochemical result. In short, comprehensive analyses show that the Wudong area in the northern Dianjiang basin and the Shuanglong area in the southern Dianjiang salt basin may be the favorable potash- forming areas of marine potash during the period of Jialingjiang Formation in the early Triassic. The results of this study may be verified by drilling.