共轭被动大陆边缘的基本类型及其特征

Basic types and characteristics of conjugate passive continental margin

随着被动大陆边缘勘探的需求日益增加,为了更好的概括全球共轭被动大陆边缘的基本特征,本文试图在广泛调研全球具有代表性的12对大陆边缘的基础上,从大地构造背景、裂解时限、空间变化3个方面,系统总结12对共轭被动大陆边缘,进而得到4种基本类型:伊比利亚—纽芬兰型、加蓬—巴西南部型、新斯科舍—摩洛哥型、几内亚湾—巴西东北部型。伊比利亚—纽芬兰型是最常见且分布最广泛的类型,具有板缘造山带型、窄边缘型、长裂谷期型特征,地壳厚度及沉积物厚度小。结构呈明显分段性特征,裂谷时间充足,地幔剥露并发生蛇纹石化。加蓬—巴西南部型以板缘造山带型为主,具有窄边缘型、中裂谷期型特征,沉积厚度大,盆地发育大型高角度正断层控制沉积,并发育丰富的盐构造,边缘与古缝合带不重合。新斯科舍—摩洛哥型以板缘造山带型为主,具有宽边缘型、中裂谷期型特征,具有不对称裂解模式和洋盆生长模式,地壳结构和沉积物在共轭边缘呈现明显不对称性;发育反转构造,生长断层,走滑断层等多种类型构造。几内亚湾—巴西东北部型以板缘非造山带型为主,具有窄边缘型、短裂谷期型特征,发育多个转换边缘盆地,受张剪性的深大断层控制,地壳厚度及沉积物厚度的变化很大,具有裂谷—剪切边缘过渡特征。

As the demand of the passive continental margin exploration is increasing,in order to sum up the basic characteristics of the passive continental margins,this paper tries to use the 12 global representative continental margins,on the basis of the tectonic background and time-space changes,to get four basic types:the Iberia-Newfoundland,S Brazil-Gabon,Nova Scotia-Morocco,Gulf of Guinea-NE Brazil.The Iberia-Newfoundland type is the most common and widely distributed type,with the characteristics of the plate margin orogenic belt type,narrow margin,and long rift stage,and the crustal thickness and sediment thickness are small.The margin is obviously segmented,the rift time is sufficient,the mantle is exhumed and serpentinization occurs.The S Brazil-Gabon type is characterized by the plate margin orogenic belt type,narrow margin and middle rift stage.The large high-angle normal faults control the deposition and the sedimentary thickness is large with abundant salt structure.The margin is not coincident with the ancient suture.The Nova Scotia-Morocco type is characterized by the plate margin orogenic belt type,with the wide margin and middle rift stage type.Because of the asymmetric break-up model and ocean crust growth model.There are many types of structures,such as inverted structure,growth fault and strike-slip fault.The gulf of Guinea-NE Brazil type is dominated by the plate margin non-orogenic belt type,with the characteristics of narrow margin and short rift stage.There are several reverse marginal basins,which are controlled by deep and large shear faults,and the crustal thickness and sediment thickness vary greatly,with the transitional characteristics of rift-shear margin.