江陵凹陷富钾锂卤水矿田地质特征及成藏模式研究

江汉盆地江陵凹陷内的高温高压高盐度卤水,富含钾、锂、硼、溴、碘、铷、铯等,达到工业品位或超过综合利用品位,构成富钾锂卤水矿,长期以来其矿体定位一直是难题,对于钾锂卤水的富集与矿田构造的关系还没有完全查清。本研究以现代矿田地质学为指导,以地球物理勘探、钻井和野外地质等资料为基础,综合分析江陵富钾锂卤水的矿田建造、矿田构造与矿田成矿作用。江陵凹陷富钾锂卤水矿田建造分为构造沉积岩相矿田和构造火山岩相矿田。江陵凹陷内各地区由于受所处构造位置的影响,在不同时期发育了不同类型的局部构造,这些局部构造在空间上有序的分布与叠置形成了大量的构造圈闭,为钾锂卤水的聚集提供了有利的场所。从古新世沙市组到早始新世新沟嘴组沉积时期,江汉盆地的古气候条件总体为高温干旱,利于古盐湖的蒸发作用,火山活动带来丰富的钾锂物质,从而利于钾锂卤水的富集。江陵凹陷富钾卤水属构造—储层耦合成藏模式:江陵凹陷盐湖沉积特征,决定了有大量卤水储存在其地层中。这些卤水最大的储集体就是砂岩孔隙,而构造产生的大量裂缝大部分位于泥岩和火成岩中,也成为储集卤水的场所。在构造褶皱及埋藏作用下,卤水开始从盐类晶间,首先进入砂岩体孔隙内,而后可能进入裂隙系统及火山岩系统。

Geological Features and Metallogenic Model of K- and Li- rich Brine Ore Field in the Jiangling Depression

High temperature, high pressure and high- salinity brine in the Jiangling depression of Jianghan basin is rich in K, Li, B, I, Rb and Cs elements, contents of which have reached the industrial grade or exceeded the comprehensive utilization grade. But this K- and Li- rich brine deposit has long faced difficulty in locating its position. The relationship between enrichment of K- and Li- rich brine and structure of ore field has not been identified. With the guide of modern ore field geology, the paper analyzed the ore field structure of brine and ore field mineralization based on geophysics, wells and fields data. Affected by tectonic locations, each area of the Jjiangling depression shows very different local structures developed in different periods. The orderly distribution and superimposition of these local structures forms abundant structural traps, which provide favorable places for the enrichment of Li K brine. During the deposition period from Shashi Formation of Paleocene to Xingouzui Formation of Early Eocene, the high temperature and dry paleoclimate of Jianghan basin was favorable for the evaporation of salt lake, and K- and Li- bearing materials from volcanic activities provided base for the enrichment of Li- K brine. Structure reservoir coupling accumuation mode of K- rich brine in the Jiangling depression and deposition characteristic of salt lake have determined that a large amount of brine accumulates in the strata. The biggest reservoir space for brine is sandstone pores. Tectonic movement resulted in the formation of a large amount of fractures in mudstone and igneous rock, which become the ideal places for brine accumulation. Due to structural fold and burial diagenesis, brine migrated from salt crystal to sandstone pores, finally into fractures and volcanic system.