湘西—黔东下寒武统清虚洞组藻灰岩沉积特征及其找矿意义

Sedimentary characteristics and prospecting significance of algal limestone in Qingxudong Formation of Lower Cambrian in Western Hunan-Eastern Guizhou

铅锌矿是湘西—黔东地区的优势矿种,资源丰富,开发历史悠久,找矿潜力巨大。综合分析前人有关湘西—黔东生物礁的资料,介绍了藻灰岩的沉积特征,并结合大量实际地质资料,对藻灰岩控矿进行了论述。结果表明:成矿物质主要来源于藻类及碳酸盐泥对Pb^(2+)、Zn^(2+)离子的吸取,矿床成因属于沉积成岩矿床类型,兼有成岩期后矿床性质;藻礁灰岩与不同岩性的接合部位及其附近等微地球化学障区,往往就是铅锌富矿体产出部位;藻礁灰岩与礁间通道的薄层泥质白云质灰岩呈指状交叉接触处,也常有铅锌富矿体产出;铅锌富矿体基本上产于清虚洞组灰岩段中,且明显受该段藻礁灰岩控制。为满足国内外对铅锌矿日益增长的消费需要,深入研究区内铅锌矿的地层岩相岩石控矿因素及其富集规律,指导该地区藻灰岩中铅锌矿找矿工作,具有重要的现实意义。

Pb-Zn ore has been listed as a favorable mineral in Western Hunan and Eastern Guizhou,with large reserve,long development history and huge potential. Through comprehensively analyzing the previous bioherm data of Western Hunan and Eastern Guizhou,the authors introduced the sedimentary characteristics of algal limestone,and discussed the ore-controlling mechanism of algal limestone based on a series of geological data. The results show that the ore-forming materials are mainly derived from the absorption of Pb2＋ and Zn2＋ions by algae and carbonate mud. The genesis of the deposit belongs to sedimentary deposit type,which has the characteristics of the post diagenetic stage. The junctions between algal reef limestone and different lithology and the nearby micro geochemical barrier zone are often rich in Pb-Zn ore body. The cross shape area at the point of contact between algal reef limestone and thin argillaceous dolomitic limestone in reef channel,is often rich in Pb-Zn ore body too. Pb-Zn rich bonanza mainly occurs in Qingxudong Formation limestone and is obviously controlled by the algal reef limestone. To meet the increasing needs of Pb-Zn ore at home and abroad,a further study of the controlling factors and enrichment law of stratigraphic lithofacies has important practical significance in guiding ore prospecting in this region.