MNR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China.
Oil & Gas Survey, China Geological Survey, Beijing 100083, China.
J Nanosci Nanotechnol. 2021 Jan 1;21(1):310-325. doi: 10.1166/jnn.2021.18564.
Scanning electron microscopy (SEM) was used to analyze and study micron-nanometer evaporite samples collected from Paleocene and Eocene drill cores in the Jiangling Depression. Accordingly, seven beds of potassium-bearing solid rocks were accurately identified. Sylvite, carnallite, syngenite, dolomite, thenardite, anhydrite, glauberite, halite, barite, celestite, and other solid salt minerals were found, and carnallite, syngenite, and thenardite were found for the first time in the Jiangling Depression. Sylvite, syngenite, and carnallite indicate that the Paleogene salt lakes in the Jiangling Depression had evolved to the sylvite stage and that prospecting for solid sylvite would be satisfactory. Micron-nanometer celestite is contained in the evaporites, from which we can infer that strontium may have been provided by deep formation water (or oil-field water). This finding is of great significance to studying the genesis of sylvite sediment in the Jiangling Depression. From the extensive development of primary glauberite beds typical of warm salt minerals in the Shashi Formation, it can be inferred that the late Paleogene paleoclimate in the Jiangling Depression of the Jianghan Basin was dry and hot. Based on the extensive distribution of micron-nanometer pyrite, siderite, iron and Fe₂O₃/FeO ratios in evaporite sediments and color analysis of mudstones, the evaporites in the study area formed in an underwater anoxic, reducing environment during sedimentation. Therefore, the evaporite sediments in the Paleocene-Eocene interval of the Jiangling Depression are proposed to have formed in a saltwater lake sedimentary environment, and the ancient lake was characterized by a deep-water salt lake sedimentary model.
扫描电子显微镜（SEM）用于分析和研究从江陵凹陷古近系和新近系岩心采集的微米-纳米级蒸发岩样品。据此，准确识别出了 7 层含钾固体岩。发现了钾盐、光卤石、水氯镁石、白云石、芒硝、硬石膏、泻利盐、石盐、重晶石、天青石等固体盐矿物，首次在江陵凹陷发现了光卤石、水氯镁石和芒硝。钾盐、水氯镁石和光卤石表明江陵凹陷古近系盐湖已演化到钾盐阶段，寻找固体钾盐将是令人满意的。蒸发岩中含有微米-纳米级天青石，从中可以推断出锶可能是由深部地层水（或油田水）提供的。这一发现对研究江陵凹陷钾盐沉积的成因具有重要意义。从广泛发育的典型暖盐矿物原生无水芒硝层可以推断，江汉盆地江陵凹陷晚古近纪古气候干燥炎热。根据蒸发岩沉积物中广泛分布的微米-纳米级黄铁矿、菱铁矿、铁和 Fe₂O₃/FeO 比值以及泥岩颜色分析，研究区蒸发岩在沉积过程中形成于水下缺氧、还原环境。因此，提出江陵凹陷古近系-新近系蒸发岩形成于咸水湖沉积环境，古湖泊具有深水盐湖沉积模式。
