白云岩化作用类型及机理——以歧口凹陷古近系沙河街组一段为例

发布时间：2019-01-01 17:54

【摘要】：通过镜下鉴定和地球化学分析对歧口凹陷古近系沙一段白云岩进行了研究,综合分析了研究区发育的岩石类型及其成因。结果表明:研究区发育泥-微晶白云岩、灰质白云岩、白云质灰岩及少量颗粒白云岩;Sr/Ba值为0.44.9,V/Ni值为1.37.1,Z值(盐度指数)分布在122.6162.5;87Sr/86Sr值和同期海水极为接近,因此推断湖盆遭受了海侵作用,海侵为白云岩化作用提供了Mg~(2+);有序度分布在0.22 0.53,整体较低;Mg/Ca值为0.730.91,反映了富钙低镁的特征,表明白云岩形成于准同生阶段。碳氧同位素分析表明,研究区白云岩形成于浅埋藏环境,并且受到了发酵作用的影响,异常高的Sr值也反映了微生物活动的存在。通过以上证据推断本区白云岩是在准同生期、浅埋藏环境、经渗透回流作用形成的,并且受到了发酵作用的影响。
[Abstract]:The dolomite of the first member of the Paleogene in Qikou Sag was studied by means of microscopic identification and geochemical analysis. The types of rocks developed in the study area and their genesis were comprehensively analyzed. The results show that mud-microcrystalline dolomite, lime-dolomite, dolomitic limestone and a small amount of granular dolomite are developed in the study area, and the Sr/Ba value is 0.44.9V / Ni = 1.37.1Z (salinity index) distributed in 122.6162.5; The 87Sr/86Sr value is very close to that of the seawater in the same period, so it is inferred that the lake basin suffered transgression, which provided Mg~ (2) for dolomization, and the order distribution was 0.22 0.53, which was relatively low. The Mg/Ca value is 0.730.91, which reflects the characteristics of rich calcium and low magnesium, indicating that dolomite was formed in the quasi-syntectic stage. Carbon and oxygen isotopic analysis shows that dolomite was formed in shallow burial environment and affected by fermentation. The abnormal high Sr value also reflects the existence of microbial activity. It is inferred from the above evidence that the dolomite in this area was formed by osmotic reflux and was influenced by fermentations in the quasi-syntectic and shallow burial environment.
【作者单位】：吉林大学地球科学学院;大港油田勘探开发研究院;长春工程学院勘查与测绘工程学院;辽宁省地震局;
【基金】：国家自然科学基金项目(41502145) 吉林省教育厅“十三五”科学技术研究规划项目(2016-0313)~~
【分类号】：P618.13

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