Evolution of the transtensional Barreirinhas pull-apart system in the Brazilian Equatorial margin and its correlation with the African conjugate counterpart

IF 2.7 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS Tectonophysics Pub Date : 2024-08-15 DOI:10.1016/j.tecto.2024.230470
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Abstract

The Barreirinhas pull-apart system encompasses marginal basins in divergent and transform margin segments in the central sector of the Brazilian Equatorial Margin and its African conjugate counterpart. This ancient pull-apart system evolved through transtensional strike-slip motion within a highly heterogeneous crystalline basement affected by multiple rift phases. The geometry and development of pull-apart structural elements during the final rifting phase before continental breakup and the mechanisms and extent to which they were influenced by preexisting crustal heterogeneities are comprehensively addressed using an extensive database of potential field (magnetic and gravity) and 2D seismic reflection data. We also assess the lithospheric thermomechanical conditions and their influence on transtensional extension throughout Curie Point Depth, Heat Flow, and Moho depth, derived from potential field data and published seismological models. Plate reconstruction of Brazilian and African equatorial margins based on gravity patterns and comparison with sandbox analog models allow a 3D synoptic model to reveal the Barreirinhas pull-apart system evolution during the Equatorial Atlantic opening. During the rift phase I, the location of major grabens was controlled by favorably oriented Neoproterozoic shear zones, while the cooler, stronger, and thicker crust beneath cratonic areas formed the western barrier to strike-slip rift activity during rift phase II. This same geological domain anchored the onset of the pull-apart system in the last rift phase III, whose principal displacement zones developed along the extensive oceanic fracture zones linked by sigmoidal fault systems. Toward the end of the rift phase, a large asymmetric lozangle to a lazy-Z-shaped, pull-apart basin developed above low overlapping ∼90°, releasing stepover in oblique transtensional strike-slip motion.

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巴西赤道边缘横向巴雷里尼亚斯拉分系统的演变及其与非洲共轭对应系统的相关性
巴雷里尼亚斯拉-分系统包括巴西赤道边缘及其非洲共轭对应物中部分异和转换边缘区段的边缘盆地。这一古老的拉-褶系统是在受多重断裂阶段影响的高度异质结晶基底中,通过横向拉伸击滑运动演化而成的。我们利用广泛的势场(磁力和重力)数据库和二维地震反射数据,全面探讨了大陆断裂前最后断裂阶段拉裂构造元素的几何形状和发展,以及它们受先前存在的地壳异质影响的机制和程度。我们还评估了岩石圈的热力学条件及其对整个居里点深度、热流和莫霍深度的横断延伸的影响,这些数据来自势场数据和已公布的地震学模型。根据重力模式对巴西和非洲赤道边缘进行板块重建,并与沙箱模拟模型进行比较,从而建立了一个三维同步模型,揭示了赤道大西洋开裂期间巴雷里尼亚斯拉裂系统的演化过程。在断裂第一阶段,主要地堑的位置受控于方向有利的新新生代剪切带,而在断裂第二阶段,板块地区下方较冷、较坚固和较厚的地壳则形成了阻碍走向滑动断裂活动的西部屏障。在最后的断裂第三阶段,同样是这一地质区域支撑了拉裂系统的开始,其主要位移带沿着由弧形断层系统连接的大洋断裂带发展。在裂谷阶段的末期,一个大型的非对称菱形至懒散的 Z 形拉裂盆地在低∼90°重叠的上方发育,在斜向横断走向滑动运动中释放出台阶。
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来源期刊
Tectonophysics
Tectonophysics 地学-地球化学与地球物理
CiteScore
4.90
自引率
6.90%
发文量
300
审稿时长
6 months
期刊介绍: The prime focus of Tectonophysics will be high-impact original research and reviews in the fields of kinematics, structure, composition, and dynamics of the solid arth at all scales. Tectonophysics particularly encourages submission of papers based on the integration of a multitude of geophysical, geological, geochemical, geodynamic, and geotectonic methods
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