| 中二叠统茅口组白云岩发育机理:以川中-川东地区为例 |
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| 引用本文： | 黎霆,诸丹诚,李海平,杨明磊,李涛,李平平,邹华耀.中二叠统茅口组白云岩发育机理:以川中-川东地区为例[J].现代地质,2020,34(2):345-355. |
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| 作者姓名： | 黎霆 诸丹诚 李海平 杨明磊 李涛 李平平 邹华耀 |
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| 作者单位： | 中国石油大学(北京) 地球科学学院,北京 102249 |
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| 基金项目： | 中国科学院战略性先导科技专项“四川盆地重点地区深层油气运移机理与富集规律”(XDA14010306);重点自然基金项目“四川盆地二叠系-三叠系白云岩储层差异演化与油气差异聚集”(U1663210);国家科技重大专项“南方海相碳酸盐岩油气成藏差异性及油气分布规律”(2017ZX05005-003-003)。 |
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| 摘 要： | 白云岩储层是茅口组一种重要的储层类型,其成因是研究重点。为此,以川中-川东地区茅口组白云岩为例,通过露头观测、岩心观察、岩石薄片鉴定及岩石地球化学分析的方法,分析了茅口组白云岩(石)的成因。结果表明:茅口组白云岩(石)可划分为层状粉晶白云岩、层状细-中晶白云岩、灰岩中零散分布的白云石、透镜状中-粗晶白云岩和鞍形白云石胶结物5种类型。其中,层状粉晶白云岩原始结构保存较好,地球化学特征与原始灰岩相似,是早期埋藏环境下形成的产物;层状细-中晶白云岩与层状粉晶白云岩相伴生,δ18O值较灰岩偏负,包裹体均一温度大于正常地层埋藏温度,部分样品可见Eu正异常,是由层状粉晶白云岩在热液作用下重结晶形成;灰岩中零散分布的白云石则与矿物的稳定化有关;透镜状中-粗晶白云岩和鞍形白云石胶结物镜下可见白云石晶面弯曲和波状消光,其δ18O值可达-10‰,包裹体均一温度高于正常地层埋藏温度,Eu正异常明显,是典型的热液白云岩(石)。
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| 关 键 词： | 茅口组 白云岩 地球化学特征 成因机理 |
| 收稿时间： | 2019-05-20 |
| 修稿时间： | 2019-09-07 |
Genetic Mechanism of Dolomite in Middle Permian Maokou Formation:Case Study of Central and Eastern Sichuan Basin |
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| LI Ting,ZHU Dancheng,LI Haiping,YANG Minglei,LI Tao,LI Pingping,ZOU Huayao.Genetic Mechanism of Dolomite in Middle Permian Maokou Formation:Case Study of Central and Eastern Sichuan Basin[J].Geoscience——Journal of Graduate School,China University of Geosciences,2020,34(2):345-355. |
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| Authors: | LI Ting ZHU Dancheng LI Haiping YANG Minglei LI Tao LI Pingping ZOU Huayao |
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| Institution: | College of Geosciences, China University of Petroleum, Beijing 102249, China |
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| Abstract: | Dolomite reservoir is important in the Maokou Formation,and its genetic mechanism is a hot topic of research.Therefore,outcrop and well core observation,thin-section identification and geochemical analysis are conducted to unravel the dolomite genetic mechanism of the Maokou Formation(Fm.).The results show that the Maokou Fm.dolomite can be divided into five types:(1)layered powdered,(2)layered fine-medium crystalline,(3)scattered in limestone,(4)lentoid medium-coarse-grained and(5)saddle cement,each with different genetic origins.The layered powdered dolomite has similar geochemical characteristics to original limestone.Its original structure is well preserved whereas gas-liquid inclusions are not developed,and appears dark red in cathodoluminescence(CL)images,suggesting that the layered powdered dolomite was formed in an early burial environment.The layered fine-medium crystalline dolomite is generally developed under the layered powdered dolomite and remaining grain apparition,whilst theδ18O value(-7.31‰)is more negative than that of the limestone(-3.77‰).Its homogenization temperature(116.9℃)is higher than the normal burial temperature(100℃),and it appears as partially bright red in CL images,suggesting that the layered fine-medium crystal dolomite was formed by hydrothermal recrystallization of layered powdered dolomite.Genesis of the scattered dolomite in limestone was likely related to the mineral stabilization processes.Both the lentoid mediumcoarse dolomite and the saddle dolomite cement,in which hydrothermal minerals(quartz,pyrobitumen,pyrite)are discovered,show a curved crystal edge and undulating extinction under the microscope.Both of them have markedly negativeδ18O value(-10‰),high homogenization temperature(120℃)and positive Eu anomaly.It appears bright red in CL images,which indicates that these two kinds of dolomite are typically hydrothermal. |
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| Keywords: | Maokou Formation dolomite geochemical characteristics genetic mechanism |
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