鄂尔多斯盆地靖边气田奥陶系马家沟组的阴极发光特征及白云岩化

Cathodoluminescence characteristics and dolomitization of Qrdovician Majiagou Formation in Jingbian Gasfield,Ordos Basin

对鄂尔多斯盆地靖边气田马家沟组白云岩的阴极发光性和岩石地球化学研究发现,白云岩阴极发光强度与Mn、Fe质量分数比值呈正相关性,白云岩微量元素整体具有低Na、Mn、Sr和高Fe含量的特点.泥晶白云岩有序度低,平均0.67,Na含量较高,质量分数平均值为302.3×10^(-6),δ^(13)C分布在0.6‰～-1.58%o,平均值为-0.33‰,反映准同生白云岩化;细晶白云岩有序度平均为0.71,δ^(13)C平均为-1.5%o,Mn含量增加,反映受成岩早期大气淡水淋滤的影响增加;中-粗晶白云岩有序度平均为0.84,Fe含量异常高,质量分数平均为11 617.2×10^(-6),δ^(13)C、δ^(18)O值都偏负,反映白云岩形成于埋藏环境.

By studying the cathodoluminescence and geochemical characteristics of Ordovician Majiagou formation dolomite,it is found that there is a positive correlation between the cathodoluminescence intensity of the dolomite and Mn/Fe ratio and the dolomite is of low content Na,Mn and Sr and high content of Fe as a whole.Micrite dolomite is characterized by low order degree of 0.67 in average, high content of Na(302.3×10^(-6)),δ^(13)C of 0.6‰~ - 1.58‰(PDB)(-1.5‰in average),which indicates that the micrite dolomite is penecontemporaneous dolomitization.Fine crystal dolomite is characterized by the average order degree of 0.71,δ^(13)C average value of - 1.55‰and higher content of Mn than the micrite dolomite,which indicates the great effect of leaching and burial diagenesis. Medium-coarse dolomite has a relative high average degree order of 0.84,anomaly high Fe content of 11 617.2×10^(-6) and relative low values of δ^(13)C andδ^(18)0,which indicates the medium-coarse dolomite is formed in the burial diagenesis.