论文部分内容阅读
通过中上扬子地区寒武系野外露头实测、踏勘、前人研究成果整理以及盆地腹地露头缺乏地区的钻井资料的分析,研究了中上扬子地区中寒武世的古地理背景。白云岩的成因、平面上以及垂向上的分布特征都受控于古地理。中寒武统整个台地区为局限台地,在台地发育咸化澙湖、潮坪、局限潮下、浅滩等次一级的古地理单元。中寒武统的膏岩与白云岩不同程度互层。向台地内部,滩相发育愈少,咸化澙湖、潮坪以及局限潮下越发育;越往台地的边缘,滩相越发育。研究区中寒武统白云岩按照晶体大小可以分为泥粉晶白云岩和砂糖状白云岩。泥粉晶白云岩为潮坪准同生白云岩,机理为蒸发泵作用,白云化流体来自于澙湖浓缩的海水。砂糖状白云岩绝大多数为回流渗透白云化成因,白云化流体主要来自于蒸发泵机理富余的高镁钙比流体。回流渗透白云化过程缓慢,白云石结晶较好。寒武系岩性在垂向上有很好的叠置关系,反映古地貌随地质时代的变迁。
The paleogeographic background of the Middle Cambrian in the Middle Upper Yangtze region was studied through the field observation of the Cambrian outcrop in the Upper Yangtze region, the reconnaissance, the previous research results, and the analysis of drilling data in areas lacking in the hinterland of the basin. The genesis, horizontal and vertical distribution of dolomite are controlled by paleogeography. The entire platform area of the Middle Cambrian is a restricted platform, and developed paleogeographical units at the sub-level such as the Limu Lake, the tidal flat, the confined tide and the shoal on the platform. The Middle Cambrian gypsum and dolomite interbedded at varying degrees. To the interior of the platform, the less the development of beach phase, salty Lake, tidal flat and the more tide under the more developed; more to the edge of the terrain, beach more development. The Middle Cambrian dolomite in the study area can be divided into dolomite dolomite and granulite dolomite according to the crystal size. Mudstone dolomite is a prospective symbiotic dolomite in the tidal layer. The mechanism is evaporation pump, and the dolomitization fluid comes from the concentrated seawater from the lagoon. Most of the dolomitic dolomites are caused by reflux infiltration and dolomitization, and the dolomitization fluids are mainly derived from the high-Mg-Ca-specific fluids that are rich in evaporation pump mechanism. Return infiltration dolomization process is slow, dolomite crystallization is better. Cambrian lithology has a good vertical superimposed relationship, reflecting the paleogeomorphology with geological changes.