辽宁本溪牛毛岭马家沟组顶部剖面的成岩作用

Diagenesis in the top profile of Majiagou formation inNiumaoling area, Benxi city, Liaoning province

本文以阴极发光为主要研究手段,通过胶结物形态和结构以及接触关系的观察,对本溪市牛毛岭马家沟组顶部剖面成岩作用进行研究,重建成岩历史和孔隙演化过程。研究结果表明,该剖面成岩作用主要包括机械压实、胶结、白云岩化、溶蚀、早期破裂作用;同生成岩阶段的成岩作用多样:分层①、②和⑤经受较强压实作用,分层③—⑤白云岩化特征符合回流渗透模式,分层④由于溶蚀形成溶塌角砾;早成岩阶段主要为胶结作用,主要发生于浅埋藏环境:分层①的掘穴和破裂等大孔隙被铁方解石充填,分层③—⑤中晶间孔隙、小窗状孔隙、溶塌裂缝、硬石膏晶体铸模等孔隙被白云石充填;中、晚成岩阶段的成岩作用很少。该剖面的成岩作用主要发生在同生—早成岩阶段,这与鄂尔多斯盆地中部中奥陶统埋藏史相似。

This paper deals with diagenesis of the top profile of Majiagou formation and reconstruct the diagenetic history and pore evolution based on cathodoluminescence testing data,observation of morphology and texture of cementing materias and contact relationship of the rocks.Diagenesis in the profile is diversified including mainly mechanical compaction,cementing,dolomitization,dissolution and early fracturing characterized by relatively strong compaction in sublayer①,②and⑤,dolomitization in sublayer③-⑤coinciding with reflux-seeping model,dissolution-collapsed breccia in sublayer④.In the early diagenesis cementing dominated at shallow depth.In the big openings of sublayer①,such as burrows and fractures are filled with ferran calcite,in openings in sublayer③-⑤,interstitial pores,fenestra,dissolution-collapsed fractures and anhydrite crystal molds with dolomite.In middle-late diagenesis the obove mentioned phemominan is rare.Burial history here is similar to that of Middle Ordovician Series in central Oreos basin.