柴达木盆地东部石炭系葡萄状灰岩缝洞的发现及成因分析

文章采用沉积学、岩石学、地球化学原理，对柴达木盆地石炭系葡萄状缝洞分布特征与成因机理进行了研究，并与四川盆地灯影组缝洞进行了对比分析。研究结果表明：柴达木盆地石炭系东部石炭系葡萄状缝洞与四川盆地灯影组葡萄状缝洞具相似的岩石学特征，可见复式纹层花边皮壳，网状泄水通道，以及大气淡水方解石、陆源砂屑、泥以及硅质自生矿物等缝洞内包卷物等岩石学标志。地化分析显示缝洞皮壳碳酸盐矿物成岩流体为海水，缝洞碳酸盐充填物的成岩流体为大气淡水。最终认为两地葡萄状缝洞皆为大气水作用的产物，柴东石炭系葡萄状灰岩缝洞是四川盆地灯影组葡萄状白云岩缝洞早期形式。二者演化过程如下：由于周期性海退使潮坪相等环境下形成的碳酸盐岩暴露而遭受溶蚀，海侵时溶蚀缝洞内形成针柱状方解石胶结，当海水进一步蒸发，胶结的针柱状方解石在海水中发生模仿交代，形成同生期白云石，这种周期性的海退海侵形成在剖面上的多套葡萄状缝洞旋回。

The discoveryand genetic analysis of grape-shaped hole of the Carboniferous in Eastern Qaidam Basin

This paper uses the principle of sedimentology, petrology and geochemistry to carry on the comparative study of the grape shaped hole between the Carboniferous formation in the Qaidam Basin and the Dengying Formation in the Sichuan Basin. And its formation mechanism and distribution characteristics are discussed in detail. Through the analysis, it shows that grape shaped hole between the Carboniferous formation in the eastern Qaidam Basin and the Dengying Formation in the Sichuan Basin have the similar petrologic characteristics. There are petrologic symbols such as multi lamina crust, mesh drainage channel, fresh water calcite, terrigenous sand, mud, and siliceous authigenic mineral. Geochemical analysis shows that diagenetic fluid of grape shaped crust carbonate mineral could be seawater, diagenetic fluid of carbonate fillings in grape shaped hole could be atmospheric freshwater. It is concluded that the grape shaped hole is the product of atmospheric water, and the early forms of the grape shaped hole on the Carboniferous formation of the Qaidam Basin is the slot hole on the Dengying Formation of the Sichuan Basin. The evolution process is as follows: due to periodic regression, tidal flat environment of carbonate rocks is exposed by dissolution, and stitches columnar calcite cementations take place in dissolution hole during the period of transgression. When the water evaporates further, the imitating replacement happens in needle cylindrical calcite cements in seawater, and forms syngenetic dolomite. The periodic regression and transgression lead to the formation of the multiple cycles of grape shaped holes on the profile.