Tectonic evolution of the South Atlantic passive continental margin based on onshore structural data

基于陆上构造资料的南大西洋被动大陆边缘构造演化

• 批准号: 172738503
• 负责人: Professor Dr. Cornelis Passchier, Ph.D., since 11/2010
• 金额: --
• 依托单位: Institut für Geowissenschaften
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2014-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/172738503?language=en
• 关键词: Tectonic; evolution; South; Atlantic; passive

This work will deal with the opening of the South Atlantic and the tectonic development of its margins with special emphasis on the Parána LIP’s (Large Igneous Province) in Brazil and the Etendeka LIP’s in Namibia. We will study the effects of deep-seated mantle processes, far-field plate stresses and local margin dynamics on the passive margin. Our first hypothesis is that the margins on both sides of the South Atlantic experienced a very different development following LIP extrusion, since hot-spot activities on both margins vary and the Brazilian margin is influenced by the Andean orogeny (being currently under compression in an E-W direction). Our second hypothesis states that the passive continental margin is segmented onshore along the large Florianopolis/Rio Grande Fracture Zone and associated faults and experiences different block movements through time. The second hypothesis is based on new thermochronologic data assembled in the first SAMPLE phase, which shows margin segmentation. Our third hypothesis is that reactivation of basement faults plays an important role in the margin dynamics. The Parána and Etendeka LIP’S and their contact to the basement rocks are an ideal archive of the post-rift development of the margin. Detailed field-work on reactivation of basement faults will be followed by a fault slip analysis in order to determine local paleo-stress states (directions of principal stresses and relative ratios of differential stresses). We will use a new powerful method (SVS-method, Sippel et al. 2009) that allows us to separate different stress states and test them thoroughly. Finally we will try to fit the determined stress states in time frames using relative fault intersections, fault dyke relations where we will date important volcanics and thermochronological data from the accompanying project. We aim to produce a new tectonicthermochronologic model of the dynamics of the South Atlantic margins, their differences and segmentation. Our work tackles important SAMPLE questions, will be compared and adjusted to offshore studies and builds an ideal basis for large-scale numerical models.

这项工作将涉及南大西洋的开放及其边缘的构造发展，特别强调巴西的Parána LIP（大火成岩省）和纳米比亚的Etendeka LIP。我们将研究深部地幔过程、远场板块应力和局部边缘动力学对被动边缘的影响。我们的第一个假设是，南大西洋两岸的边缘在LIP挤压之后经历了非常不同的发展，因为两个边缘的热点活动不同，而巴西边缘受到安第斯造山运动的影响（目前处于东西向的挤压之下）。第二种假设认为，被动大陆边缘沿Florianopolis/里约热内卢大断裂带及其相关断层向陆上分割，并经历不同的地块运动。第二个假设是基于在第一个SAMPLE阶段收集的新的热年代学数据，它显示了边缘分割。我们的第三个假设是基底断层的再激活在边缘动力学中起着重要作用。Parána和Etendeka LIP及其与基底岩石的接触是裂谷后边缘发育的理想档案。在对基底断层重新激活进行详细的野外工作之后，将进行断层滑动分析，以确定当地的古应力状态（主应力方向和差应力的相对比率）。我们将使用一种新的强大的方法（SVS-method, Sippel et al. 2009），它允许我们分离不同的应力状态并彻底测试它们。最后，我们将尝试在时间框架内使用相对断层交叉点、断层脉关系来拟合确定的应力状态，我们将对相关项目中的重要火山和热年代学数据进行定年。我们的目标是建立一个新的南大西洋边缘动力学的构造-热年代学模型，它们的差异和分割。我们的工作解决了重要的SAMPLE问题，将与离岸研究进行比较和调整，并为大规模数值模型建立理想的基础。