Evolution of the Subsurface K‐Rich Brines in the Triassic Carbonates in the Sichuan Basin of China
Evolution of the Subsurface K‐Rich Brines in the Triassic Carbonates in the Sichuan Basin of China
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DOI：
10.1111/gwat.12614
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发表时间：
2018-09
期刊：
影响因子：
2.6
通讯作者：
Xun Zhou;Xiaocui Wang;Jiajun Han;Qin Cao;Changlong Jiang;Juanhan Guo;Haiyan Zhou
中科院分区：
文献类型：
--
作者：
Xun Zhou;Xiaocui Wang;Jiajun Han;Qin Cao;Changlong Jiang;Juanhan Guo;Haiyan Zhou
地下富钾卤水是肥料生产的重要矿物资源，而这种卤水的演变记录很少。在中国西南部的四川盆地，它们主要分布在中、下三叠统海相碳酸盐岩含水层中。卤水的总溶解固体为176 - 378 g/L，钾浓度为1.9 - 53.3 g/L。我们发现卤水主要为Cl‐Na型，而Ba在卤水中不存在。将盐水样品与离子轨迹和新提出的蒸发海水离子比轨迹进行比较表明，盐水富含Ca、Sr、Li和I，贫SO 4和Mg，既不富集也不贫Cl和Na。这些卤水经历了四个演化阶段：（1）海相岩石沉积阶段，（2）陆相碎屑岩沉积阶段，（3）构造变形阶段，（4）岩石侵蚀阶段。前两期盐矿物的沉淀、结晶作用、硫酸盐还原和重结晶作用是卤水化学成分富集和贫化的主要原因。两口采自中三叠统雷口坡碳酸盐岩含水层的威尔斯井中钾浓度极高，是由于卤水向古近纪第三纪形成的背斜运移过程中钾盐的地下溶解所致。由于第四期含盐碳酸盐岩的不一致溶解，盆地东部一些背斜的河谷中出露的碳酸盐岩中产生了盐和咸泉。
Subsurface K‐rich brines are important mineral resources for fertilizer production while the evolution of such brines is poorly documented. In the Sichuan Basin in southwest China, they are found mainly in the Middle and Lower Triassic marine carbonate aquifers. Total dissolved solids of the brines range from 176 to 378 g/L and K concentrations, from 1.9 to 53.3 g/L. We found that the brines are mainly of Cl‐Na type, while Ba is absent in the brines. Comparison of the brine samples with both the trajectories of ions and the newly proposed trajectories of ion ratios of evaporated seawater suggests that the brines are enriched in Ca, Sr, Li, and I, depleted in SO4 and Mg, and neither enriched nor depleted in Cl and Na. These brines underwent four evolutionary periods: (1) deposition of marine rocks, (2) deposition of continental clastics, (3) tectonic deformation, and (4) rock erosion. Precipitation of salt minerals, dolomitization, sulfate reduction, and recrystallization during the first two periods are responsible for the enrichment and depletion of the chemical constituents of the brines. Extremely high K concentrations in two wells, both tapping the Middle Triassic Leikoupo carbonate aquifers, are attributed to the subsurface dissolution of potash salts during the migration of the brines to the anticlines formed during the third period in the Paleogene age. Saline and salty springs emanate from the outcropping carbonates in the river valleys in some anticlines in the eastern basin due to incongruent dissolution of the salt‐bearing carbonates during the fourth period.