Investigation of Ancient and Modern Melting Processes Preserved in Sub-oceanic Island Mantle

发生在地表的板块构造过程最终由地幔内发生的对流控制。了解地幔对流过程需要更全面地了解地幔的成分和热力变化。 该项目旨在通过研究加那利群岛熔岩中喷发的地幔碎片，即所谓的“捕虏体”，探讨地幔成分的变化。这些捕虏体保存的证据表明，他们起源的地幔经历了古老的熔融事件（1 Ga），但这些事件的化学证据已部分被后来修改的捕虏体在合并和喷发的熔岩。 该项目的目标是开发方法来识别保存在海洋岛屿（如加那利群岛）下的海洋地幔中的古代和现代熔融过程，并利用这些新信息来了解地球上地幔的成分变化。熔体组成和地幔的物理行为。科学问题将通过测量Nd-Hf-Os同位素，高度亲铁元素和主要和微量元素丰度在一套捕虏体，以了解长期的演化和HSE分布在地幔中，并检查过程中涉及的生成和保存的非均质地幔。新的数据也将用于评估样品中的熔体相互作用和交代作用。我们的方法将测试假设的形成，演化和破坏的亏损地幔域在海洋或大陆环境。这将包括比较现代熔融过程中的岛屿与可能的古代熔融过程中保存的捕虏体，以评估在俯冲带，羽或脊设置，或作为全球规模的熔融事件的耐火地幔的生成模型，并探讨高度亏损，耐火地幔域的模式，作为不同的同位素和元素的签名记录在一些板内岩浆的来源。

Plate tectonic processes occurring at the surface are ultimately governed by convection occurring within Earth's mantle. Understanding mantle convection processes requires a fuller understanding of both compositional and thermal variations in the mantle. This project aims to address compositional variations in the mantle, through the study of mantle fragments, known as "xenoliths", erupted in lavas from the Canary Islands. These xenoliths preserve evidence that the mantle from which they originated experienced ancient melting events (1 Ga), but that the chemical evidence for these events have been partly obscured by later modification of the xenoliths during incorporation and eruption within the lavas. Goals of the project are to develop methods to identify ancient and modern melting processes preserved in oceanic mantle beneath ocean islands, like the Canary Islands, and to use this new information to understand compositional variation in the Earth's upper mantle.A more refined understanding of when and how mantle heterogeneities are formed and, in some cases, destroyed has profound impact on our understanding of mantle melting processes, melt composition and physical behaviour of the mantle. Science questions will be addressed by measuring Nd-Hf-Os isotopes, highly siderophile elements and major- and trace-element abundances in a suite of xenoliths to understand the long-term evolution and HSE distribution in the mantle and to examine processes involved in generation and preservation of heterogeneous mantle. The new data will also be used to evaluate melt interactions and metasomatism in samples. Our methods will test hypotheses for the formation, evolution and destruction of depleted mantle domains in oceanic or continental environments. This will include comparison of modern melting processes in the islands with possible ancient melting processes preserved in the xenoliths, to assess models for the generation of refractory mantle in subduction-zone, plume or ridge settings, or as global-scale melting events, and to explore models for highly-depleted, refractory mantle domains as sources of distinct isotopic and elemental signatures recorded in some intraplate magmas.