江陵凹陷古新世地下卤水型硼矿成因研究

中国探明硼资源主要分布于东北和青藏等地区,矿床品位低,共伴生矿物多,开发成本高,开发利用程度低,难以满足产业发展需求。目前,在江汉盆地江陵凹陷勘探中发现卤水中B2O3浓度达3 g/L,Li、K、Br、I、Rb、Cs含量超过工业品位,综合利用价值高。本文在前人研究的基础上,对江陵凹陷新生代卤水型硼矿开展水化学、同位素地球化学及实验地球化学分析,重点研究了古气候、构造和玄武岩等对卤水成矿的影响,探究其成因机制。研究初步认为,不同的储卤层岩性具有不同的地球化学和同位素特征,玄武岩有强烈的蚀变,说明地下流体对火成岩发生了交代作用,玄武岩的水-岩反应是富硼卤水矿的重要物质来源;一定盐度的流体有利于硼离子的活化,高盐度流体是硼成矿元素主要的迁移载体,表生环境下干热的古气候使含矿水体蒸发浓缩是富硼卤水富集成矿的重要形成机制。

A study of the genesis of Paleocene underground brine boron deposits in Jiangling Depression

The proved boron resources in China are mainly distributed in Northeast China, Qinghai, Tibet and some other regions. These deposits have low grade, many associated minerals, high development cost and low development and utilization degree, and hence it is difficult for them to meet the needs of industrial development. At present, exploration in Jiangling Depression of Jianghan Basin shows that the B₂O₃ concentration in the brine reaches 3 g/L, and the content of lithium, potassium, bromoiodide, rubidium and cesium exceeds the industrial grade, with high comprehensive utilization value. On the basis of previous studies, the authors studied hydrochemistry, isotopic geochemistry and experimental geochemistry of Cenozoic brine boron deposits in Jiangling Depression in this paper, with the emphasis placed on the influence of paleoclimate, structure and provenance on brine mineralization as well as the genetic mechanism. It is preliminarily concluded that different halogen lithologies have different geochemical and isotopic characteristics, and basalt has experienced strong alteration, indicating that underground fluid metasomatism of igneous rocks exists, and the water-rock reaction of basalt is an important material source of boron-rich brine deposits. The fluid with a certain salinity is more conducive to the activation of boron ions. The fluid with a high salinity is the main transport carrier of boron ore-forming elements. The evaporation and concentration of ore-bearing water in the dry and hot paleoclimate under the supergenic environment constitute an important process for the enrichment and mineralization of boron-rich brine.