【摘要】：本論文在前人研究的基礎上,以巖石學、地球化學為指導,充分利用薄片觀察、陰極發(fā)光、流體包裹體、碳氧穩(wěn)定同位素測試等資料,對巢湖地區(qū)二疊系棲霞組和三疊系南陵湖組灰?guī)r內方解石脈進行了研究,并結合大地構造演化背景,從宏觀和微觀的角度分析了裂縫的活動和方解石脈形成的耦合關系。安徽巢北地區(qū)在漫長的地質歷史中經(jīng)歷了多期構造運動,二疊系棲霞組和三疊系南陵湖組灰?guī)r內主要發(fā)育三種類型脈體:張性(張扭性)脈體、“X”型剪切脈、雁列脈。在宏觀描述的基礎上,結合薄片鏡下觀察和陰極發(fā)光技術,分析脈體內部微觀結構。方解石脈晶體形態(tài)主要有塊狀、拉長塊狀、纖維狀和擴展狀。生長方向以及排列形式的不同,將脈體的生長方式分為對向生長脈、背向生長脈、擴展脈,不同生長模式具有相應的晶體形態(tài)。脈體的形成主要包括兩個方面,成脈物質在溶液中運移和成脈物質的沉淀結晶。成脈物質以擴散流、流體流的形成在裂縫空間中運移。大部分脈體的生長都伴隨裂縫的裂開,但并不是必須的,如壓力裙在無裂縫條件下同樣可以形成纖維狀方解石晶體。通過碳氧同位素、流體包裹體測試分析,認為棲霞組和南陵湖組在流體來源和性質方面差異并不顯著,流體主要來源于圍巖,且可能有大氣淡水的交換作用。南陵湖組方解石脈均一溫度范圍56.8~97.1℃,可分出兩期不同溫度的流體分別為65~80℃范圍內和80~100℃;棲霞組方解石脈溫度范圍為52.3~117.3℃,可大致分出三期不同均一溫度,最主要的兩期分別位于60~80℃、90~100℃范圍內,與南陵湖組具有一致性,反映淺埋藏環(huán)境;第三期為100~120℃,溫度較高但分布較少。由冰點測試經(jīng)溫度-鹽度轉換得到兩組地層成脈流體鹽度大部分小于8%,以中低鹽度為主。
[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，

本文編號：2502731