巢北地区二叠系、三叠系碳酸盐岩方解石脉的微观特征与裂缝活动关系研究
发布时间:2019-06-19 23:47
【摘要】:本论文在前人研究的基础上,以岩石学、地球化学为指导,充分利用薄片观察、阴极发光、流体包裹体、碳氧稳定同位素测试等资料,对巢湖地区二叠系栖霞组和三叠系南陵湖组灰岩内方解石脉进行了研究,并结合大地构造演化背景,从宏观和微观的角度分析了裂缝的活动和方解石脉形成的耦合关系。安徽巢北地区在漫长的地质历史中经历了多期构造运动,二叠系栖霞组和三叠系南陵湖组灰岩内主要发育三种类型脉体:张性(张扭性)脉体、“X”型剪切脉、雁列脉。在宏观描述的基础上,结合薄片镜下观察和阴极发光技术,分析脉体内部微观结构。方解石脉晶体形态主要有块状、拉长块状、纤维状和扩展状。生长方向以及排列形式的不同,将脉体的生长方式分为对向生长脉、背向生长脉、扩展脉,不同生长模式具有相应的晶体形态。脉体的形成主要包括两个方面,成脉物质在溶液中运移和成脉物质的沉淀结晶。成脉物质以扩散流、流体流的形成在裂缝空间中运移。大部分脉体的生长都伴随裂缝的裂开,但并不是必须的,如压力裙在无裂缝条件下同样可以形成纤维状方解石晶体。通过碳氧同位素、流体包裹体测试分析,认为栖霞组和南陵湖组在流体来源和性质方面差异并不显著,流体主要来源于围岩,且可能有大气淡水的交换作用。南陵湖组方解石脉均一温度范围56.8~97.1℃,可分出两期不同温度的流体分别为65~80℃范围内和80~100℃;栖霞组方解石脉温度范围为52.3~117.3℃,可大致分出三期不同均一温度,最主要的两期分别位于60~80℃、90~100℃范围内,与南陵湖组具有一致性,反映浅埋藏环境;第三期为100~120℃,温度较高但分布较少。由冰点测试经温度-盐度转换得到两组地层成脉流体盐度大部分小于8%,以中低盐度为主。
[Abstract]:On the basis of previous studies, guided by petrology and geochemistry, this paper makes full use of thin slice observation, cathodoluminescence, fluid inclusions, carbon and oxygen stable isotope testing and other data to study the calcite veins in the limestone of Qixia formation and Nanlinghu formation in Chaohu area, and combined with the background of tectonic evolution. The coupling relationship between fracture activity and calcite vein formation is analyzed from macro and micro points of view. Chaobei area of Anhui Province has experienced multiple tectonic movements in its long geological history. Three main types of veins are developed in the limestone of Permian Qixia formation and Triassic Nanlinghu formation: tensioned (tensioned) vein, "X" shear vein and Yanli vein. On the basis of macroscopic description, the internal microstructure of pulse body was analyzed by means of thin sheet mirror observation and cathodoluminescence technique. The crystal morphology of calcite vein is mainly block, elongated block, fibrous and extended. With the different growth direction and arrangement, the growth mode of pulse body can be divided into opposite growth vein, backward growth vein, extended pulse and different growth modes have corresponding crystal morphology. The formation of pulse body mainly includes two aspects: the migration of pulse-forming material in solution and the precipitation and crystallization of vein-forming material. The veined material is diffused and the fluid flow is formed in the fracture space. The growth of most veins is accompanied by cracks, but it is not necessary. For example, pressure skirts can also form fibrous calcite crystals without cracks. Through the test and analysis of carbon and oxygen isotopes and fluid inclusions, it is considered that there is no significant difference in the source and properties of fluid between Qixia formation and Nanlinghu formation. The fluid mainly comes from surrounding rock and may have the exchange of atmospheric fresh water. The homogenization temperature range of calcite veins in Nanlinghu formation is 56.8 鈮,
本文编号:2502731
[Abstract]:On the basis of previous studies, guided by petrology and geochemistry, this paper makes full use of thin slice observation, cathodoluminescence, fluid inclusions, carbon and oxygen stable isotope testing and other data to study the calcite veins in the limestone of Qixia formation and Nanlinghu formation in Chaohu area, and combined with the background of tectonic evolution. The coupling relationship between fracture activity and calcite vein formation is analyzed from macro and micro points of view. Chaobei area of Anhui Province has experienced multiple tectonic movements in its long geological history. Three main types of veins are developed in the limestone of Permian Qixia formation and Triassic Nanlinghu formation: tensioned (tensioned) vein, "X" shear vein and Yanli vein. On the basis of macroscopic description, the internal microstructure of pulse body was analyzed by means of thin sheet mirror observation and cathodoluminescence technique. The crystal morphology of calcite vein is mainly block, elongated block, fibrous and extended. With the different growth direction and arrangement, the growth mode of pulse body can be divided into opposite growth vein, backward growth vein, extended pulse and different growth modes have corresponding crystal morphology. The formation of pulse body mainly includes two aspects: the migration of pulse-forming material in solution and the precipitation and crystallization of vein-forming material. The veined material is diffused and the fluid flow is formed in the fracture space. The growth of most veins is accompanied by cracks, but it is not necessary. For example, pressure skirts can also form fibrous calcite crystals without cracks. Through the test and analysis of carbon and oxygen isotopes and fluid inclusions, it is considered that there is no significant difference in the source and properties of fluid between Qixia formation and Nanlinghu formation. The fluid mainly comes from surrounding rock and may have the exchange of atmospheric fresh water. The homogenization temperature range of calcite veins in Nanlinghu formation is 56.8 鈮,
本文编号:2502731
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