塔里木盆地下古生界白云岩类型及成因*

塔里木盆地下古生界白云岩勘探潜力巨大。在下古生界构造演化、沉积背景分析的基础上, 结合前人的白云岩分类方案, 首先根据形成时期将塔里木盆地下古生界白云岩分为准同生白云岩和准同生后白云岩两大类。在此基础上, 综合运用岩心、薄片、阴极发光、扫描电镜、碳氧稳定同位素资料, 对上述两类白云岩进一步细分。其中准同生白云岩, 可进一步分为云坪型准同生白云岩、潟湖型准同生白云岩与微生物白云岩, 云坪型、潟湖型准同生白云岩是在准同生阶段由蒸发泵白云化形成的；本次研究首次在膏模孔内发现完整哑铃状白云石, 拓宽了微生物白云岩的存在范围。准同生后白云岩包括浅埋藏白云岩、中—深埋藏白云岩和热液白云岩3类, 浅埋藏白云岩由调整白云化及渗透回流白云化形成；中—深埋藏白云岩主要为埋藏白云化的产物；热液白云岩由沿断裂或裂缝的热液白云化所形成。

Type and origin of the Lower Paleozoic dolostones in Tarim Basin

There was a huge exploration potential in the Lower Paleozoic dolostones of Tarim Basin. In a combination of former classification schemes and based on the analysis of tectonic evolution and sedimentary background, the Lower Paleozoic dolostone was classified into two types (penecontemporaneous dolostones and post-penecontemporaneous dolostones) according to its forming time. Furthermore, more detailed subtypes were divided through combining the data of cores, thin sections, cathodoluminescence(CL), scanning electron microscope(SEM) and stable isotopes (δ¹³, C and δ¹⁸, O). And penecontemporaneous dolostones could be divided into three subtypes, including penecontemporaneous dolostones in supratidal flat environments, penecontemporaneous dolostones in lagoons, and microbial dolostones. The former two subtypes were dolomitized by evaporating seawater in arid environment and complete dumbbell-like dolomite was firstly found in gypsum moldic pore, which expanded the existence area of the microbial dolomite. While post-penecontemporaneous dolostones could be divided into three subtypes: shallow burial dolostones, middle-deep burial dolostones and hydrothermal dolomites. Shallow burial dolostones were dolomitized by adjusting|pore water and infiltrating reflux of brine. Middle-deep burial dolostones were occurred in middle-deep burial. The hydrothermal dolomites|were dolomitized by hydrothermal fluids along faults/fractures.