四川北川通口二叠系中二叠统岩石特征

Petrological characteristics of the Middle Permian series of Tongkou section,Beichuan County,Sichuan Province

四川北川通口剖面中二叠统分为栖霞组和茅口组,总厚度为200.82m。该剖面岩石以石灰岩为主,石灰岩可进一步分为生屑石灰岩、生屑质石灰岩、含生屑石灰岩、云斑石灰岩和眼球状石灰岩。分析认为,眼球状石灰岩的沉积环境可能为水体较局限、稍深的碳酸盐岩台地,为沉积作用和成岩作用的共同产物;云质石灰岩为埋藏成因,在埋藏作用引起的压力差的情况下,M g2+聚集到孔隙度较高或者裂缝较发育的栖霞组顶部的石灰岩段流通,同时由于区域性的峨眉山玄武岩喷发引起的局部异常高温得以形成。

The Middle Permian series of Tongkou section at Beichuan County,Sichuan Province is composed of the Qixia and Maokou Formations,with a thickness of 200.82 m.The rock types of this section are limestones.Limestones can be further divided into bioclastic limestones,bioelastics-bearing limestones,cloudy limestones and eyeball shaped limestones.It analysis that the sedimentary environment of eyeball shaped limestones might be the limitation water or deep-water carbonate platform,it was formed by the interaction of sedimentation and diagenesis.It analysis that dolomite limestone formed by burial dolomitization.At the pressure difference of the burial dolomitization,Mg2＋ were aggregated at the top of Qixia Formations,which had higher porosity or fracture development,and it need the high-temperature which was caused by the Emeishan basalts.