The northern boundary of the Iceland plume: Petrology and volcanology of the Tjörnes "fracture zone"

冰岛羽流的北部边界：Tjörnes“断裂带”的岩石学和火山学

• 批准号: 5325332
• 负责人: Professor Dr. Colin Devey
• 金额: --
• 依托单位: GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2001
• 资助国家: 德国
• 起止时间: 2000-12-31 至 2007-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5325332?language=en
• 关键词: northern; boundary; Iceland; plume; Petrology

Heterogeneities in the Earth´s mantle are probably destroyed through time by convective mixing. Some of the strongest convective movements occur close to mantle plumes, and so the nature of their interaction and mixing with the surrounding mantle of their internal compositional zoning is important for placing constraints on mantle mixing processes. The ridge-centred Iceland hotspot allows a unique sampling of compositional boundaries both within and around the supposed mantle plume due to the presence of the spreading axes, which provide a sampling profile across the plume. The present project aims to sample the spreading axis in the Tjörnes region directly north of Iceland, where a clear geochemical boundary occurs between enriched hotspot-like basalts subaerially and depleted mid-ocean ridge-like basalts offshore. Our main aims are to find out how sharp this geochemical boundary is and where it lies at present and back through time. From this we hope to be able to deduce the orientation of the boundary in the mantle. To achieve these aims a joint volcanological, geochemical, geochronological and geophysical approach is required. We wish, in collaboration with the other projects in this package to determine: - the present-day and past distribution of magma-types at Tjörnes; - the eruption history of the Tjörnes spreading axis; - the relationships between seismicity, eruptions and hydrothermalism at Tjörnes. To achieve these aims we propose a ship-based mapping and sampling of the Tjörnes zone using the FS Poseidon in the summers of 2002 and 2003. The development of a dating method using high-resolution ICP-MS and the U and Th decay series will be important, together with detailed side-scan information, for constraining the evolution of the area.

地球地幔的非均质性可能随着时间的推移被对流混合所破坏。一些最强的对流运动发生在地幔柱附近，因此它们与周围地幔的相互作用和混合的性质及其内部成分带对地幔混合过程的限制是重要的。以山脊为中心的冰岛热点允许对地幔柱内部和周围的成分边界进行独特的采样，这是由于扩展轴的存在，从而提供了整个地幔柱的采样剖面。目前的项目旨在对冰岛北部Tjörnes地区的扩展轴进行采样，该地区在海底富集的热点样玄武岩和海上枯竭的洋中脊样玄武岩之间存在明确的地球化学边界。我们的主要目的是找出这个地球化学边界有多尖锐，以及它现在和过去的位置。由此我们希望能够推断出地幔中边界的方向。为了实现这些目标，需要联合采用火山学、地球化学、地质年代学和地球物理方法。我们希望与这一揽子计划中的其他项目合作，确定：- Tjörnes的岩浆类型现在和过去的分布；- Tjörnes扩散轴的喷发历史；-地震活动、火山喷发和热液作用之间的关系，网址为Tjörnes。为了实现这些目标，我们建议在2002年和2003年夏季使用FS Poseidon对Tjörnes区域进行基于船的测绘和采样。使用高分辨率ICP-MS和U和Th衰变系列的测年方法的发展将是重要的，以及详细的侧扫描信息，以限制该地区的演变。