湘西—黔东地区寒武系清虚洞组地层特征与铅锌成矿关系

湘西—黔东地区寒武系发育完整,是一套从黑色岩系到碳酸盐岩的沉积序列。下寒武统清虚洞组由灰岩段和白云岩段组成,纵向上构成总体向上海水变浅的沉积相序列,同时反映了缓坡型碳酸盐岩台地的发育过程。该组空间上从北西至南东可识别出潮坪相、局限台地相粉细晶云岩、台地边缘浅滩相粉细晶灰岩和台地边缘(滩)丘相微晶灰岩、浅-深缓坡相、陆棚相泥灰岩、台地前缘盆地等沉积。研究表明,地层岩性、岩相古地理对铅锌矿具有明显的控制作用,微晶丘是主要容矿层,与微生物和海底热水关系密切。铅锌成矿明显与浊流沉积和风暴沉积等事件沉积相关,浊积岩、微晶丘、砾(粒)屑灰岩构成一完整的铅锌控矿序列。

Stratigraphic characteristics of the Cambrian Qingxudong Formation in relation to lead-zinc mineralization in western Hunan-eastern Guizhou area

In the western Hunan-eastern Guizhou area,the Cambrian strata are well developed and characterized by sedimentary succession from black shale to carbonate rocks.Vertically,the limestone segment and dolomitite segment constitute the Qingxudong Formation made up of an upward-shoaling succession of sedimentary facies and demonstrates a growth process of the ramp carbonate platform.Horizontally,the principal lithofacies palaeogeographic units in the study area have been recognized,which include carbonate tidal flat,subtidal facies of restricted platform,platform marginal bioherm(or bank) facies and shallow ramp—deep ramp facies as well as shelf-basin facies in southward succession.All these data suggest that the formation of the lead-zinc deposits was controlled by stratigraphy,lithologic character and lithofacies-palaeogeographic framework and related to turbidite and tempestite.The host rocks(reservoir beds) were micrite mounds(mud mounds) formed by CO2-bearing hydrothermal solution and bio-process.The assemblage made up of turbidite and micrite mounds(algal bioherm) and rudstone was a well developed succession favorable for the formation of lead-zinc deposits.