广西象州—武宣一带泥盆系白云岩化特征

本文通过野外观察和室内镜下研究,就广西象州—武宣—带泥盆系白云岩的分布、类型和白云岩化的阶段特征以及其剖面相序进行了论述,并阐述了白云岩化作用的形成机理,提出处于古地理高部位的生物礁滩、砂屑滩以及浅水潮坪区的成岩白云岩及部分准同生白云岩与混合水白云岩化机理有关;部分泻湖相的准同生白云岩可能与渗滤回流作用有关:台凹相的泥质白云岩与埋藏压实作用机理有关:层纹石白云岩及部分条带(纹)状灰云岩则与生物作用有关:而后生白云岩属热卤水作用等看法。指出成岩及成岩—后生铅锌矿床与生物礁,滩带和潮坪泻湖相带成岩期白云岩化作用关系密切,铅锌矿化或矿体的厚度大小和富集程度往往与含矿白云岩的厚度呈正相关关系。后生铅锌矿床则与后生白云岩作用有关,矿石矿物主要赋存于含矿断裂切穿白云岩的部位,呈网脉状分布于后生脉状白云岩或层间破碎带的角砾白云岩中。

THE CHARACTERISTICS OF THE DEVONIAN DOLOMITIZATION IN XIANGZHOU-WUXUAN COUNTIES, GUANGXI

Based on field observation and microscope studies, this paper describes and discusses the distribution, type and characteristics, mechanism, and facies sequence on profile of olomitization of the Devonian dolostone in Xiangzhou- Wuxuan Counties, Guangxi. It is proposed that the diagenetic dolostone and some penecontemporaneous dolostone in organic reef bank, sandy clastic bank, and tidal flat are genetically related to the mixing of seawater and meteoric water; that some penecontemporaneous dolostone of lagoon facies related to percolating; that the argillaceous dolostone in depression of platform related to burrial and compaction; that laminated dolostone and some banded lime-dolostone relat ed to organism; and that the epigenetic dolostone related to hot brine. In addition, it is pointed out that diagenetic and diagenetic- epigenetic Pb-Zn deposits are closely related to the dolomitization during the diagenetic stages of organic reef, shoal zone, and tidal-la goon facies, and fhat the thickness of Pb-Zn mineralization or orebodies shows positive correlation with the thickness of the ore-bearing dolostone. It has also been discovered that the epigenetic Pb-Zn deposits are related to epigenetic dolomitization, and that the ore minerals mainly occur in dolostone cut by ore-bearing fractures, or as stockworks in net-shaped dolostone, or in breciated dolostone in interformational crush zone.