局部白云岩化作用研究:以塔里木盆地阿克苏地区蓬莱坝剖面鹰山组为例  

Study on Structural Dolomitization:Taking the Yingshan Formation of the Penglaiba Section in Aksu Area as An Example

作　　者：谭聪 刘策[1] 王铜山[1] 李秋芬[1] 朱玺 付景龙 姜华[1] TAN Cong;LIU Ce;WANG Tongshan;LI Qiufen;ZHU Xi;FU Jinglong;JIANG Hua(Research Institute of Petroleum Exploration&Development,CNPC,Bejing 100083,China;Liaoning Chenical Geology Exploration Institute Co.,Ltd.,Jinzhou,Liaoning 121007,China;Research Instiute of Petroleum Exploration and Derelopment,Huabei Oilfield Company,CNPC,Renqiu,Hebei 062550,China)

机构地区：[1]中国石油勘探开发研究院,北京100083 [2]辽宁省化工地质勘查院有限责任公司,辽宁锦州121000 [3]中国石油华北油田分公司勘探开发研究院,河北任丘062550

出　　处：《现代地质》2023年第5期1182-1193,共12页Geoscience

基　　金：中国石油天然气股份有限公司前瞻性基础性科技重大专项(2021DJ05,2023ZZ0201)。

摘　　要：通过对塔里木盆地阿克苏地区蓬莱坝剖面鹰山组的系统野外测量、岩性描述、样品采集、薄片观察以及地球化学分析,对鹰山组小规模局部发育的白云岩的成因进行详细分析。蓬莱坝剖面鹰山组可划分为上下两段,整体岩性为灰岩,下段为亮晶藻砂屑灰岩,具有明显的高能颗粒滩相沉积特征,上段为球粒泥晶灰岩,以低能滩及滩间海沉积为主。剖面被多条断层切割,局部白云岩主要发育在鹰山组下段断裂附近,呈透镜状、准层状分布,白云岩化程度具有以断裂为中心沿层面向周边逐渐减弱的特点。白云岩地球化学分析结果显示其Fe、Mn含量低,与周边灰岩相重叠,Na、K含量与灰岩之间也没有区分,反映白云岩化流体为海水源;Sr元素含量明显高于周边灰岩,表明白云岩化作用并非发生在表生环境下;稀土元素则具有轻稀土元素富集、重稀土元素亏损的特征,Eu表现出明显负异常,Ce元素轻微亏损,表现出与现代海水相似的特征。白云岩样品碳-氧同位素相比于灰岩更轻,指示流体的蒸发性质。综合研究认为,蓬莱坝剖面鹰山组围绕断裂发育的局部白云岩的形成阶段可能发生在浅埋藏阶段,白云岩化流体可能来源于由断裂沟通的中上寒武统蒸发卤水,是一类不同于典型构造-热液白云岩的小型构造白云岩。Through systematic field survey,lithology descriptions,sample collection,thin-section observation and geochemical analysis of the Yingshan Formation in the Penglaiba section of Aksu area in Tarim Basin,the local small-scale genesis of dolomite in the Yingshan Format ion is analyzed in detail.The results show that the Yingshan Formation in Penglaiba section can be divided into upper and lower segments,and the overall lithology is limestone.The lower section comprises sparry algal arenaceous limestone,which has clear sedimentary char-acteristics of high-energy granular beach facies.The upper section is globular micrite limestone,which is domi-nated by low-energy beach and intertidal marine sediments.The profile is cut by several faults,and dolomite is locally developed near the fault of the lower segment of Y ingshan Formation,distributed in lenticular or semilayered form.The degree of dolomitization decreases gradually along the layer and away from the fault.Geo-chemical analysis of the dolomite shows that the rock has low Fe and Mn contents,overlapping with the sur-rounding limestone,and there is no distinction on Na and K contents from the limestone,reflecting that the do-lomitization fluid is of marine origin.The Sr content is obviously higher than that of the surrounding limestone,indicating that the mica alteration was not supergene related.The REE compositions are characterized by en-richment of LREEs and depletion of HREEs.Eu shows obviously negative anomaly,while Ce shows slight de-pletion,similar to modern seawater.Carbon-oxygen isotopes of the dolomite samples are lighter than those of the limestone,indicating the evaporite property of the fluid.Through comprehensive research,we considered that the local dolomitization around the fault in the Yingshan F ormation(Penglaiba section)may have occurred in the shallow burial stage.The dolomitizat ion fluid may have come from the evaporated brine of the Middle-Up-per Cambrian strata connected by the fault,which is a kind of small structural dolomite different f

关 键 词：白云岩化作用 鹰山组 蓬莱坝剖面 塔里木盆地 

分 类 号：P588.245[天文地球—岩石学]