二连盆地阿南凹陷下白垩统腾格尔组湖相云质岩成因

发布时间：2018-06-02 22:15

  本文选题：湖相沉积 + 云质岩　； 参考：《地球科学》2017年02期

【摘要】：二连盆地阿南凹陷下白垩统腾格尔组发育一套湖相的富含致密油云质岩段,包括云质泥岩、云质沉凝灰岩和云质砂岩,但这类云质岩中的白云石岩石学特征及成因尚不明确.通过岩心、薄片、扫描电镜及碳氧同位素分析,将云质岩中的白云石分为两类:(1)分布在纹层状和星点状云质泥岩或云质沉凝灰岩的非平直晶面、半自形微粉晶白云石;(2)分布在块状云质沉凝灰岩或云质砂岩的非平直-平直晶面、自形粉细晶白云石.两类白云石的成因机制不同:(1)半自形微粉晶白云石具偏高的δ~(13)C_(PDB)值(平均为5.4‰),主要受产甲烷菌的代谢活动影响,其δ~(18) O_(PDB)值负偏移量较小(平均为-13.0‰),计算形成温度约50~75℃,推测为成岩早期成因白云石,Mg~(2+)离子主要来源于富火山灰的凝灰物质大量水解.(2)自形粉细晶白云石晶体较大、晶形好,其δ~(13) C_(PDB)值偏低(0.2‰~0.7‰),受产甲烷菌的代谢活动和深层有机质热催化共同影响,其δ~(18) O_(PDB)值较低(平均为-19.4‰),计算形成温度约119℃,推测为成岩晚期埋藏成因白云石,Mg~(2+)离子可能与粘土矿物水解及深部流体上涌有关.
[Abstract]:The lower Cretaceous Tengger formation in Erlian Basin developed a set of lacustrine dense oil-rich dolomite formations, including dolomitic mudstone, cloud-precipitated tuff and dolomite sandstone. However, the petrological characteristics and genesis of dolomite in this type of dolomite are still unclear. By means of core, thin slice, scanning electron microscope and carbon and oxygen isotope analysis, dolomite in the dolomite is divided into two types: 1) distributed on the non-straight crystal plane of laminated and starlike dolomite mudstone or cloud-precipitated tuff. The semi-automorphic micrystalline dolomite is distributed on the flat and flat crystal planes of massive cloud-precipitated tuff or cloud-like sandstone, and self-shaped silt fine-grained dolomite. The genetic mechanism of the two types of dolomite is different: 1) the semi-automorphic micro-powdered dolomite has a high 未 ~ (13) C ~ (-1) PDBs (an average of 5.4 鈥，

本文编号：1970387