华北克拉通典型拗拉槽中—新元古界沉积体系与古地理演化

Meso-Neoproterozoic sedimentary system and palaeogeographic evolution of typical aulacogens in the North China Craton

中—新元古界的油气资源潜力业已引起国际地质界的密切关注。近年来,新的钻探资料证实,华北克拉通中—新元古代发育多个克拉通内拗拉槽,且拗拉槽内发育多套优质烃源岩及生储盖组合,显示具有巨大的油气勘探潜力。本文以华北克拉通东北缘燕辽拗拉槽和南缘熊耳拗拉槽中—新元古代地层为研究对象,以6条典型基干剖面实测、9条重点辅助剖面观察、3口单井岩芯观察与描述,主要从岩石颜色、岩石组合类型、岩石结构、沉积构造、地球化学等众多方面,对华北克拉通典型拗拉槽中—新元古界的沉积体系类型和特征以及古地理环境的整体演化进行了全面、系统的研究。结果表明:(1)研究区中—新元古界发育障壁型海岸相、无障壁型海岸相、浅海陆棚相、碳酸盐台地相、生物礁相、扇三角洲相以及冰川相等7种沉积相、15种亚相及21种微相。(2)在研究区不同时期岩相古地理格局具有明显差异;中元古代,研究区由长城纪晚期海相碎屑沉积体系转变成蓟县纪海相碳酸盐沉积体系,再向待建纪早期海相碎屑沉积体系、海相碳酸盐沉积体系共存转变;新元古代,研究区由青白口纪海相碎屑沉积体系转变到仅熊耳拗拉槽发育震旦纪冰川-碎屑岩沉积体系,且南北差异明显。

The potential of oil and gas resources in the Meso-Neoproterozoic has attracted close attention of the international geological community. Proterozoic high-quality source rocks in other countries also developed in the North China Craton basin in China at the same time, indicating that the Meso-Neoproterozoic in North China also has great exploration potential. This paper considers Meso-Neoproterozoic strata in Yanliao Aulacogen and Xiong’er Aulacogen of the north-eastern margin of North China Craton as the research object. Based on 6 field backbone profile measurements and 9 key auxiliary profile observations, the types and characteristics of Meso-Neoproterozoic sedimentary systems and the overall evolution of palaeogeographic environment in the typical aulacogens of North China Craton are systematically studied from the aspects of rock color, rock association type, rock structure, sedimentary structure and geochemistry. The results shows that: 1) the Meso-Neoproterozoic in the study area can be divided into seven sedimentary facies of barrier-type coastal facies, barrier-free coastal facies, neritic shelf facies, carbonate platform facies, biohermal facies, fan delta facies and glacial facies. According to its sedimentary characteristics, fifteen subfacies and twenty one microfacies are further divided. 2) The lithofacies and palaeogeographic characteristics in different periods of the study area are obviously different. In Mesoproterozoic, the study area sedimentary systems changed from clastic rock sedimentary system of the later Changcheng System to carbonate rock sedimentary system of the Jixian System, and then to the coexistence of clastic rock sedimentary system and carbonate rock sedimentary system of the early Daijian System. In Neoproterozoic, the study area changed from clastic rock sedimentary system of the Qingbaikou System to glacial-clastic rock sedimentary system of the Sinian System developed only in Xiong’er aulacogen, and the difference between north and south is obvious.