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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.
In the Lower Cretaceous Tengger Formation in the Anan Sag of Erlian Basin, a set of lacustrine rich and dense oil-bearing dolomites, including cloud-like mudstone, cloud-like tuff, and cloud-like sandstone, are developed. However, The petrological characteristics and causes of lithostratigraphy are still unclear. The dolomite in dolomite can be divided into two types by core, thin slice, SEM and carbon and oxygen isotope analysis: (1) Non-flattened and semi-self-crystalline dolomite of mudstone or cloud-like tuff; (2) non-flattened and flattened crystal planes distributed in massive cloud-like tuff or cloud-like sandstone, Dolomite.The two types of dolomite have different mechanism of formation: (1) The δ ~ (13) C PDB values (average 5.4 ‰) of semi-self-shaped dolomite dolomite are mainly caused by methanogenic The δ ~ (18) O PDB value has a small negative offset (-13.0 ‰), and the formation temperature is about 50 ~ 75 ℃. It is presumed that dolomite, Mg ~ (2) +) Ions mainly come from hydrolysis of ash-rich tuffaceous matter. (2) The crystal of self-shaped fine crystalline dolomite is large and the crystal form is good. The δ ~ (13) C PDB value is low (0.2 ‰ ~ 0.7 ‰), by the production of methane The δ ~ (18) O_ (PDB) value was lower (-19.4 ‰) on average, and the formation temperature was about 119 ℃. It was presumed that dolomite was burial genetic dolomite, Mg ~ (2+) ions may be related to the hydrolysis of clay minerals and the upwelling of deep fluids.