| Jiangling Sag is the largest secondary tectonic units in Jianghan Basin. It is not only rich in oil and gas resources, but also very rich in salt resources. Thenardite is of great economic value in most salt minerals developed in Jiangling Sag. After years of oil and gas exploration and development, we have built a profound understanding of depression structure, sedimentary and other basic geological problems and accumulated a lot of basic information. But due to the past research work focusing on the exploration and development of oil and gas, the study on distribution and formation of mineral salts in sag is insufficient. In order to clarify the development of thenardite in south of Jiangling Sag and provide a reasonable basis for the next exploration and development, it is necessary to analyze the distribution law and main factors of mineralization of thenardite in this area.By the investigating of typical thenardite deposits in Zengjiahe, Lixian, Hunan, Qianjiang Sag, Xiaoban Sag and Zhaoji, Qingfeng, Huai’an, Jiangsu Province, the paper studied the geological rules of mine thenardite deposit, and summed up the basic characteristics of it. Thenardite is the product of the late sulfate stage in salt-lake facies. Usually, salt minerals sedimentary facies is more clearly in sag. In the plane, the centers of sedimentary facies are usually salt rock, from which outwards were water thenardite-glauberite-plaster, showing the typical "bull’s eye" depositional model of the salt-lake deposit; in the vertical, according to their different solubility, they grow from top to bottom by the rhythm of salt rock-thenardite-glauberite-plaster. The minerals sometimes layered, and sometimes mixed with each other.Based on a study of the typical analyses of thenardite deposits, combined with previous research on salt resources in south of Jiangling Sag, mainly based on drilling, rock core, logging, the paper built a relationship between lithology and electrical response, and created a recognition mode of thenardite and other mineral salts. Use the established thenardite recognition mode to review the wells drilled Shashi Formation and the lower of Xingouzui Formation in south of Jiangling Sag. After a review of the study area, the paper found thenardite mineralization in four wells, the more representative of which are Well Jiangshen2and Gangjia1, Well Jiangshen2has a44-meters continuous thickness of thenardite mineralization, and Well Gangjia1has10.5-meters of that.Based on the review results of thenardite in south of Jiangling Sag, the paper selected15representative wells and drew up comparison charts of eight-well profiles(Shashi Formation(four) and the lower of Xingouzui Formation(four)) in direction of EW (one) and NS(three), which are used to stratigraphic division and correlation. It made clear the development of thenardite and other mineral salts at different times, that in south of Jiangling Sag the thenardite mainly developed in southern slope of Zifusi syncline, eastern slope of Meihuaiqiao syncline and Yanjing-Shenjindu syncline.Referring to the previous study on the structural characteristics of the southern Jiangling Sag, combined with the review results of thenardite and stratigraphic correlation, the paper studied the distribution characteristics of thenardite in south of Jiangling Sag, and prediction of favorable area. Because of the special structure and seasonal climate changes in south Jiangling Sag, as well as the rain and provenance recharge, there are no obvious zonal distribution of salt deposits in the South of Jiangling Sag on a flat, with a incompleted development of facies; it also appeared a variety of rhythmic combinations in the vertical. The favorable area of thenardite deposits are the deep part in the sag and the secondary syncline on Gong’an monocline. |
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