恩施剖面G-L界线自生石膏与钠长石成因

Origin of Authigenic Gypsum and Albite at G-L Boundary in Enshi Section

为探讨恩施剖面自生石膏和钠长石的成因,对样品开展了X射线荧光光谱、薄片镜下观察和能谱分析。采用Sr/Ba法和计算Al/(Al+Fe+Mn)及绘制Al-Fe-Mn三角图,分析了恩施剖面G-L界限中自生石膏与钠长石赋存的沉积环境中元素地球化学特征所指示的沉积构造环境。研究表明,构造背景主要为被动大陆边缘,且沉积环境为典型的海相特征。吴家坪组底部的石膏为成岩作用成因,其形成过程主要由于黄铁矿氧化产生硫酸根及酸性环境,后者引发火山物质蚀变产生钙离子,导致钙离子和硫酸根离子浓度升高而生成石膏。吴家坪组泥质灰岩中的自生钠长石是由于成岩过程中热液流体交代生物骨骼而成。

In order to discuss the origin of authigenic gypsum and albite in Enshi section, rock samples have been studied by XRD, electron microscope and energy spectrum. Using Sr/Ba, Al/（ Al ＋ Fe ＋ Mn） method and Al-Fe-Mn triangular diagram, analyzing the tectonic setting of G-L boundary containing authigenic gypsum and albite. Results show that tectonic setting was passive continental margin, and the sedimentary environment of sedimentary rock was typical marine characteristics. The gypsum in the lower Wuchiaping Formation was diagenetic in origin. It was formed due to the oxidization of pyrite, producing sulfate and acid setting. The latter yield the alter- ation of volcanic material and produce Ca^2＋ , resulting in high concentration SO4^2- and Ca^2＋ , and thus forming gypsum. The authigenic albite in the marlstone in the lower Wuchiaping Formation was formed via the replacement of bio-skeleton by hydrothermal activity.