Absolute paleointensities on cretaceous kimberlites in Botswana

博茨瓦纳白垩纪金伯利岩的绝对古强度

• 批准号: 55068635
• 负责人: Professor Dr. Valerian Bachtadse
• 金额: --
• 依托单位: Sektion Geophysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2008
• 资助国家: 德国
• 起止时间: 2007-12-31 至 2008-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/55068635?language=en
• 关键词: Absolute; paleointensities; cretaceous; kimberlites; Botswana

Superchrons provide a remarkable opportunity to test the various theories and models regarding convection in the Earth’s liquid outer core and the generation of the geomagnetic field. To obtain a complete picture of the geodynamo, determination of the paleointensity is crucial in addition to paleodirections, which were mainly determined in the past. So far only few studies have collected intensity data for the last 160 Ma. The great variety of their results led to three different models of long-term paleointensity changes (1: lower mean paleointensity during the Mesozoic than during the Cenozoic; 2: significantly higher intensity in the last 0.3 Ma than prior to that; 3: high mean paleointensity during the Cretaceous Normal Superchron, CNS). Much more high quality data is needed especially for the CNS to be able to confirm or reject these models and to decide between the different theories of the geodynamo. Kimberlites of cretaceous age, which are quite numerous in southern Africa, may provide an opportunity to obtain a high amount of intensity data for the CNS. The target of this study is, thus, to sample a variety of kimberlite pipes in Botswana and to check their suitability for paleointensity determination. Previous studies, which have focused on their paleodirectional characteristics, yielded very reliable data and the resulting paleomagnetic poles form an important part of Africa’s apparent polar wander path. However, alterations, either in situ or during the experiment, complicate paleointensity determination and further problems may arise due to differences in cooling rates, magnetic anisotropy of the remanence and magnetic domain state bias. It is therefore planned to carry out detailed rock magnetic and paleodirectional studies in combination with paleo-intensity determinations in order to gain complete knowledge about remanence acquisition processes in kimberlites. If paleointensity determinations turn out to be possible, we will be able to significantly increase the paleointensity data set.

SuperChron提供了一个非凡的机会，可以测试有关地球液体外部核心会议和地磁领域的各种理论和模型。为了获得Geodynamo的完整图片，除了古偶发时，对古显度的测定至关重要，这主要是过去确定的。到目前为止，只有很少的研究收集了最后160 MA的强度数据。他们的结果多种多样导致三种不同的长期古显着变化模型（1：中生代期间的平均古显着性较低； 2：在最后0.3 mA中的强度比在此之前的强度明显高； 3：高度平均含量的海胆正常中的均值高显着性，CNS，CNS）。需要更多的高质量数据，尤其是使中枢神经系统能够确认或拒绝这些模型并在Geodynamo的不同理论之间进行决定。在南非数量很多的白垩纪时代金伯利特人可能会提供一个机会，以获取中枢神经系统的大量强度数据。因此，这项研究的目标是对博茨瓦纳的各种金伯利岩管进行采样，并检查其适合生长强度测定的性。以前的研究集中在其古分别特征上，得出了非常可靠的数据，而由此产生的古磁杆构成了非洲明显的极地徘徊路径的重要组成部分。但是，无论是原位还是在实验期间的改变，复杂的古显度测定以及进一步的问题可能是由于冷却速率的差异，避孕液的磁各向异性和磁性域状态偏差所致。因此，计划将详细的岩石磁性和形式研究与古强度确定结合使用，以便获得有关金伯利特岛中remanence采集过程的完整知识。如果可能实现了古显着的确定，我们将能够显着增加古显着数据集。