大巴山地区早古生代黑色岩系岩相古地理及页岩气地质意义

发布时间：2019-02-22 10:12

【摘要】：大巴山地区早古生代发育下寒武统水井沱组(巴山组—鲁家坪组)和上奥陶统五峰组—下志留统龙马溪组2套黑色岩系。沉积学研究表明,2套黑色岩系均发育于扬子北缘被动大陆边缘盆地之上,早期快速海侵,沉积环境以深水陆棚为主,晚期随着海平面下降逐渐变为浅水陆棚沉积,局部发育滩礁沉积。早寒武世和晚奥陶世—早志留世,研究区均处于被动大陆边缘盆地,基底不平整,陆架边缘呈现多个小岛阻隔的古地理格局,但两者的形成机制却完全不同:早寒武世的构造格局沿袭了陡山沱期的地堑和地垒分布格局,地垒处表现为局部隆起或水下潜隆;晚奥陶世—早志留世的构造格局则与扬子板块向华北板块俯冲有关,是在扬子北缘被动大陆边缘基础上发育起来的前陆隆起。这种受限的滞留海域有利于形成厚度大、有机碳含量高(2%~6%)、脆性矿物含量高(40%~65%)的富有机质页岩,虽然其是页岩气勘探的有利目标层系,但仍需加强构造保存条件的研究。
[Abstract]:The Lower Cambrian Jingtuo formation (Bashan formation-Lujiaping formation) and the Upper Ordovician Wufeng formation and Lower Silurian Longmaxi formation developed two sets of black rock series in the Dabashan area. Sedimentological studies show that the two sets of black rock series are developed on the passive continental margin basin in the northern margin of Yangtze, and the early rapid transgression, the sedimentary environment is dominated by deep-water shelf, and the late stage becomes shallow water shelf deposition with the sea level falling. Locally developed beach reef deposits. In the early Cambrian and the late Ordovic-early Silurian, the study area is located in the passive continental margin basin, the basement is uneven, and the continental shelf margin presents the paleogeographic pattern of several small islands. However, the formation mechanism of the two is completely different: the early Cambrian tectonic pattern follows the Doushantuo graben and the distribution pattern of the Horst, which appears as local uplift or submerged uplift; The late Ordovician early Silurian tectonic pattern is related to the subduction of the Yangtze plate to the North China plate and is a Foreland uplift developed on the basis of the passive continental margin of the northern margin of Yangtze. This confined area is conducive to the formation of organic shale with large thickness, high organic carbon content (2%) and brittle mineral content (40% 65%), although it is a favorable target series for shale gas exploration. However, it is necessary to strengthen the study of structural preservation conditions.
【作者单位】：成都理工大学地球科学学院;中国地质调查局成都地质调查中心;国土资源部沉积盆地与油气资源重点实验室;山东省物化探勘查院;
【基金】：国家自然科学基金项目(编号:41672112,41372124)资助~~
【分类号】：P618.13

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