河南桐柏县安棚一带曹庄天然碱矿芒硝矿地质特征及成因分析

Geological characteristics and genesis analysis of Caozhuang natural alkali deposit and mirabilite deposit in Anpeng area,Tongbai County,Henan

泌阳凹陷天然碱矿、芒硝矿位于河南省桐柏县城西北,是近年来我国发现的一重要的盐类矿床。区内矿层结构较简单,呈层状、似层状、条带状产出的高品质矿层为主,垂直和水平分带清晰明显。天然碱矿体平均厚度为2.20m,平均品位为51.75%,主要矿物成分重碳钠石;芒硝矿体平均厚度为8.93m,平均品位为60.14%,主要矿物成分无水芒硝矿石。区内两种矿石矿物均呈柱状结构、半自形晶粒状结构、他形粒状结构,致密块状构造、层状构造。受古地理环境影响矿层厚度在整个矿区内有较大变化:中部埋深大而厚,四周埋藏浅而薄;东部、南部接近盆地边缘埋藏急剧变浅、变薄尖灭。由于凹陷周边物源丰富及高山深盆的古环境,形成封闭的水体,在盆地内堆积了巨厚的沉积物,构成了十分有利的成矿地质背景。在干湿交替的古气候,稳定的静水还原环境中,经过一系列复杂的深水沉积生物化学反应,形成本区典型的湖相蒸发浓缩沉积矿床。

The natural alkali deposit and mirabilite deposit in Biyang Depression is located in the northwest of Tongbai County,Henan Province,which is an important salt deposit discovered in recent years.The structure of ore layers is simple in the area,and the high-quality ore layers are mainly stratified,semi-stratified and banded,and the vertical and horizontal zonation is clear and obvious.The average thickness of natural alkali orebody is 2.20 m,the average grade is 51.75%,and the main mineral composition is nahcolite.The average thickness of mirabilite orebody is 8.93 m,and the average grade is 60.14%.The main mineral composition is anhydrous mirabilite ore.The two ore minerals in the area have columnar structure,semi-hedral grain structure,alloomorphic granular structure,dense massive structure and layered structure.Due to the influence of palaeogeographic environment,the thickness of ore layer varies greatly in the whole mining area.In the central part the orebody is buried deep and thick,and in the periphery the orebody is buried shallow and thin.In the east and south near the edge of the basin the orebody is buried sharply shallow and thin and pinched out.Due to the rich material source around the depression and the paleoenvironment of high mountains and deep basins,closed water body is formed and huge thick sediments are accumulated in the basin,a very favorable geological background is formed for the mineralization.The typical lacustrine evaporative and concentrated deposit is formed through a series of complex biochemical reactions of deep-water deposition in the paleoclimate of dry and wet alternation and stable hydrostatic reduction environment.