江陵凹陷古新统盐类矿物沉积特征及其成钾指示意义  

Paleocene mineral assemblage characteristics of Jiangling Depression and their significance for potash formation

作　　者：沈立建[1] 刘成林[1] 徐海明[1] 王春连[1] 王立成[1] 刘宝坤[2] 张林兵[2] 

机构地区：[1]中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室,北京100037 [2]中国地质大学地球科学与资源学院,北京100083

出　　处：《矿床地质》2014年第5期1020-1030,共11页Mineral Deposits

基　　金：国家重点基础研究发展计划项目(编号:2011CB403000);中央级公益性科研院所基本科研业务费项目(编号:K1415);国家自然科学基金青年基金(编号:41202059)联合资助

摘　　要：在对江陵凹陷中GK1、GK2、SK3和B103井岩芯进行详细观察的基础上,借助X射线衍射、扫描电镜、薄片鉴定等手段,确认了在古新统有多种盐类矿物存在,并对盐类矿物特征和矿物组合特征进行了分析。江陵凹陷含盐系地层的矿物种类、组合比较简单,目前发现的盐类矿物有碳酸盐、硫酸盐、氯化物三大类。古新统沙市组沉积时期,出现了大量的盐类矿物,主要为石盐、硬石膏、钙芒硝及无水芒硝,此外,应有少量—微量的钾石盐。作为干热指示矿物的钙芒硝和无水芒硝在沙市组广泛发育,可以推断出江陵凹陷在古新统沙市组时期的古气候属于干热型,此时湖水蒸发作用显著增高,导致古盐湖演化程度较高,向干盐湖阶段发展;而到了新沟嘴组沉积时期,发生湖侵,盐湖水体变深、盐度降低,盐湖遭受淡化。初步判断江陵凹陷古近系沙市组具有较好的成钾条件。Based on detailed observations and descriptions of GK1, GK2, SK3 and B103＇ s drilling cores in the Jiangling Depression, the authors confirmed the existence of various sorts of salt minerals in Paleocene by such means as X-ray diffraction, SEM and thin section identification, and analyzed the individual and assemblage characteristics of salt minerals. The mineral species and assemblages of salt-bearing strata in the Jiangling Depression are simple, comprising three types, i.e., carbonate, sulfate, and chloride. The sequence of salt precipitation is as follows： （1） calcite ＋ dolomite; （2） gypsum; （3） glauberite; （4） halite to thenardite; （5） sylvite. Plenty of salt minerals have deposited in Shashi Formation, comprising mainly halite, anhydrite and glauberite with minor sylvite, indicating that the water body＇s salinity of depression was increasing notably. As warm facies indicators, glauberite and thenardite are widely developed in Shashi Formation, suggesting that the Paleocene paleoclimate of Shashi Formation in the Jiangling Depression was dry and warm. Therefore, the evolution of the salt lake was at a higher level, and entered inter the stage of playa at that time; then, lake transgression happened in Xingouzui Formation, the water body became less salty and more freshly; subsequently, the precipitation of some salt minerals caused by tectonic movements shallowed the water depth. It is thus preliminarily held that the Pa- leocene Shashi Formation in the Jiangling Depression has fairly favorable potash-forming conditions.

关 键 词：地质学 江陵凹陷 古新统 盐类矿物 矿物组合 成钾指示 

分 类 号：P619.211[天文地球—矿床学]