下扬子区不同应力场下的成岩作用特征研究

Research on Diagenetic Characteristics of Various Stress Fields in Lower Yangtze Area

通过对下扬子区三叠系青龙组和侏罗系象山组的野外露头观察、普通光学镜下分析、扫描电镜与能谱测试分析、X-衍射分析和包裹体观察等一系列分析测试,研究表明下扬子区构造应力场可分为挤压和拉张两种:挤压应力场对应构造缝合线、泥缝、泥质不均匀富集、分散的微缝合线和局部的重结晶现象等构造成岩作用特征,其不同变形程度的褶皱中岩石构造成岩现象和强度存在差别,随褶皱程度的增强,构造成岩作用强度增大;拉张应力场对应后期形成的构造裂缝和石英张裂缝等构造成岩作用特征。研究证实,不同的应力作用下岩石表现出不同的构造变形特征,成岩强度与变形强度之间存在明显的正相关关系。

Based on the outcrop observation,analysis of optical microscope,SEM inspection and electron energy spectrometry,X-Ray diffractometry and inclusion analysis,the Triassic Qinglong Formation and Jurassic Xiangshan Formation in Lower Yangtze Aera were studied.The research indicates that there were two kinds of stress fields in Lower Yangtze Aera,they were compressional stress field and extensional stress field.The compressional stress field was corresponded to the characteristics of structural diagenesis,such as structural stylolite,mud suture,nonuniform muddy enrichment,discrete microstylolite and regional recrystallization etc.Folds in different deformational levels had different tectonic diagenetic phenomena and intensities,with the increase of fold deformation,the tectonic diagenetic intensity became stronger and stronger.The extensional stress field was corresponded to various post tectonic fractures and tensile cracks of the quartz particles etc.The study demonstrates that rocks and layers under different stresses have various tectonic deformational characters.There is an apparent positive correlation between diagenetic intensity and deformational intensity.