鲁西南黄岗潜凹陷岩盐矿地质特征及找矿远景

Geological Characteristics and Prospecting Potentials of Rock Salt Deposit in Huanggang Subdepression in Southwestern Shandong Province

黄岗潜凹陷岩盐矿床是山东省地质科学研究院近年发现的一大型岩盐矿产地,预测岩盐矿总资源量超过240×10^(8)t。本文在总结黄岗潜凹陷岩盐矿勘查成果的基础上,对区内岩盐矿沉积地质特征及成矿规律、岩相分布规律等进行了初步总结分析。岩盐矿赋矿层位为古近纪官庄群大汶口组中段,岩性为深灰色泥岩、粉砂质泥岩与灰白色膏质泥岩、石盐岩互层,是一套含石盐、石膏的浅湖—咸湖相沉积建造,其盖层为新近纪黄骅群和第四系。岩盐矿层赋存形态简单,呈层状产出,产状稳定,走向近EW向,倾向近S向,倾角平缓,一般<3°,局部断层附近可达10°。区内揭露岩盐矿层31层,埋深1079.75~1730.86m,单矿层平均厚度0.25~24.64m,单层最厚53.96m,累计平均厚度175.45m,单孔累计最大厚度320.23m,是山东迄今单孔控制最大的厚度,NaCl平均品位44.11%~96.08%。岩盐矿石矿物成分较为简单,主要盐类矿物成分为石盐和硬石膏,杂质矿物主要为黏土质矿物;矿石主要化学组分为NaCl,其次为CaSO_(4),其他组分含量甚微;矿石结构主要为中粗粒他形—半自形粒状结构,矿石构造主要为块状构造;岩盐矿划分为结晶块状石盐矿石和石膏石盐混生石盐矿石2种自然类型,矿石工业类型初步确定为石膏质石盐矿石。黄岗潜凹陷盆地为一套浅湖—咸湖相沉积,大致反映了含盐水体淡化—浓缩—淡化的蒸发沉积过程;平面上初步划分石盐岩相区和膏泥岩相区2个岩相分布区,其中石盐岩相区靠近成盐盆地局部沉积中心,发育厚层岩盐矿。黄岗潜凹陷西南部含盐地层总体表现为向南倾伏的单斜形态;区域重力资料显示,该区靠近盆地局部沉积中心,具有较大的岩盐矿找矿潜力。区内岩盐矿层厚、质纯、埋深适中,初步评价具备建设盐穴储气储能库的地质条件,矿床开发利用前景广阔。

The rock salt deposit in Huanggang subdepression is a large rock salt producing area discovered by Shandong Institute of Geological Sciences in recent years.It is predicted that the total resources of rock salt deposit will exceed 24 billion tons.On the basis of summarizing the exploration results of rock salt deposits in Huanggang subdepression,sedimentary geological characteristics,metallogenic regularity and lithofacies distribution of rock salt deposits in the area have been preliminarily summarized and analyzed in this paper.The rock salt deposit is located in the middle section of Dawenkou formation of Guanzhuang group in Paleogene.The lithology is the interbedding of dark gray mudstone,silty mudstone,gray white gypsum mudstone and halite.It is a set of shallow lake saline lake sedimentary formation containing halite and gypsum.Its cap rock is Neogene Huanghua group and Quaternary.The occurrence form of rock salt mine is simple,and it occurs in layers with stable occurrence.Its strike is close to EW direction and inclines to S direction with gentle dip angle,generally less than 3°and 10°near local faults.There are 31 layers of exposed rock salt ore in the area.The burial depth is 1079.75~1730.86m,average thickness of single ore bed is 0.25~24.64m,maximum thickness of single layer is 53.96m,cumulative average thickness is 175.45m,and average grade of NaCl is 44.11%~96.08%.The accumulated maximum thickness of single hole is 320.23m,which is the largest thickness controlled by single hole in Shandong so far.The mineral composition of rock salt ore is relatively simple,the main salt minerals are halite and anhydrite,and the impurity minerals are mainly clayey minerals.The main chemical group of the ore is NaCl,followed by CaSO_(4),and the content of other components is very small.The ore structure is mainly medium and coarse-grained anisotomorphic to semi-idiomorphic granular structure,and the ore structure is mainly massive structure.The rock salt ore can be divided into two natural types:crystalline massive rock salt ore and gypsum rock salt mixed with rock salt ore,and the industrial type of ore is preliminarily determined as gypsum halite ore.The basin of Huanggang subdepression is a set of shallow lacustrine and salty lacustrine facies,which roughly reflects the evaporation deposition process of desalination,concentration and desalination of saline water bodies.In the plane,it is preliminarily divided into two lithofacies distribution areas:halite lithofacies area and gypsum mudstone facies area.The halite lithofacies area is close to the local sedimentary center of the salt forming basin,and thick rock salt deposits are developed.It is showed that the salt bearing strata in the southwest of Huanggang subdepression are inclined to the south,and the regional gravity data show that the area is close to local sedimentary center of the basin,so it has great prospecting potential for rock salt deposits.The rock salt deposit in the area is thick,pure in quality and moderate in buried depth.Geological conditions for the construction of salt cavern gas and energy storage are preliminarily evaluated,and the development and utilization prospect of the deposit is broad.