High resolution volcanology and geochemistry of mid ocean ridge segments flanking the 9°40'S melt anomaly and the Ascension hot spot

南纬 9°40 融化异常和阿森松热点两侧洋中脊部分的高分辨率火山学和地球化学

• 批准号: 16112887
• 负责人: Professor Dr. Carsten Münker
• 金额: --
• 依托单位: Institut für Geologie und Mineralogie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2005
• 资助国家: 德国
• 起止时间: 2004-12-31 至 2011-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/16112887?language=en
• 关键词: resolution; volcanology; geochemistry; mid; ocean

Mid-ocean ridge volcanism plays a key role in the investigation of melt generation and mantle processes on a global scale. The SPP MARSouth area is particularly suited to investigate the influences of different mantle sources at high resolution, as fertile mantle (9°40'S melt anomaly) and alleged hot spot volcanism (Ascension Island) are both present together with typical depleted MORB. Results from isotope and high-precision HFSE analyses, performed during the first phase of the project, show that previous geodynamic models need to be revised, in particular in the light of new Hf-Nd isotope data. Moreover, our new data for submarine and subaerial volcanism on Ascension demonstrate that distinctive mantle source were tapped that are not related to a rising mantle plume. Based on these promising results we will focus our research during the second phase of the project on erupt ion-scale volcanological and geochemical investigations. The principal aims are to characterize eruption-scale effects of mantle heterogeneities and to unravel the origin of Ascension Island. A second focus will be on the behavior of HFSE (including W) during MORB melting. First result indicate that W-Nb-Ta abundances are little fractionated, which is in marked contrast to experimental predictions. Based on an expanded dataset, we will address this conundrum by trace element modeling.

洋中脊火山作用在全球范围内研究熔体生成和地幔过程中起着关键作用。SPP MARSouth地区特别适合于以高分辨率调查不同地幔源的影响，因为肥沃的地幔（9°40'S熔融异常）和所谓的热点火山作用（Ascension Island）都与典型的亏损MORB一起存在。在项目第一阶段进行的同位素和高精度HFSE分析的结果表明，以前的地球动力学模型需要修订，特别是根据新的Hf-Nd同位素数据。此外，我们关于Ascension的海底和陆上火山活动的新数据表明，独特的地幔来源与上升的地幔柱无关。基于这些有希望的结果，我们将在项目的第二阶段集中研究喷发离子规模的火山学和地球化学调查。主要目的是描述地幔不均匀性的喷发尺度效应，并揭示Ascension岛的起源。第二个重点将是HFSE（包括W）在MORB熔化过程中的行为。第一个结果表明，W-Nb-Ta丰度分馏很小，这与实验预测形成鲜明对比。基于扩展的数据集，我们将通过痕量元素建模来解决这个难题。