Magma reservoir evolution at a slow-spreading mid-ocean ridge

缓慢扩张的洋中脊的岩浆储层演化

• 批准号: NE/X019098/1
• 负责人: Cornelis Lissenberg
• 金额: $ 3.49万
• 依托单位: CARDIFF UNIVERSITY
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX019098%2F1
• 关键词: Magma; reservoir; evolution; slow; spreading

Mid-ocean ridges form the largest magmatic system on Earth. Oceanic crust is formed when the upper mantle wells up and partially melts in response to plate separation. The melts thus formed rise upwards, forming the magma reservoirs of the lower oceanic crust, and erupt to form mid-ocean ridge basalts.The nature of magma reservoirs at mid-ocean ridges remains poorly constrained. Traditional models hold that they are bodies of pure melt in which magma evolution is controlled by fractional crystallisation. This model is increasingly challenged, and a new paradigm in which magma reservoirs are comprised of crystal mush - a mixture of melt and crystals - has now emerged. Melt transport and evolution in mush reservoirs may be controlled by porous flow, which has fundamental implications for the eruption dynamics and geochemical signatures of mid-ocean ridge basalts.This project will reconstruct the architecture and evolution of magma reservoirs at the Mid-Atlantic Ridge. It will capitalise on core that will be recovered from Hole U1309D (30 degrees N) by scientific ocean drilling. Previous drilling at this location has shown that this section contains an excellent record of fossilised magma reservoirs beneath a slow-spreading mid-ocean ridge.This project will integrate core observations with state-of-the-art element mapping and measurements of mineral major- and trace elements to address three challenges:1) The size of magma reservoirs;2) The melt composition and evolution within these reservoirs;3) The thermal histories of the reservoirs.Together, these different components will enable a test of the different end member models for reservoir architecture and melt transport. The outcome is a rigorous assessment of the nature and evolution of magma reservoirs beneath the Mid-Atlantic Ridge, with implications for magma evolution of oceanic basalts, which may serve as a template for mafic igneous systems generally.

大洋中脊形成了地球上最大的岩浆系统。洋壳是在上地幔威尔斯隆起并因板块分离而部分熔融时形成的。由此形成的熔融物向上上升，形成下洋壳的岩浆库，并喷发形成洋中脊玄武岩。传统模型认为它们是纯熔体，其中岩浆演化受分离结晶控制。这一模型正受到越来越多的挑战，一种新的范式，其中岩浆水库是由晶体糊状物-熔体和晶体的混合物-现在已经出现。熔体输运和演化在糊状水库可能是由多孔流，这对喷发动力学和洋中脊玄武岩的地球化学特征具有根本性的影响。它将利用将通过科学海洋钻探从孔U1309 D（北纬30度）中回收的岩心。该项目将把岩心观测与最先进的元素绘图和矿物主元素和微量元素测量相结合，以解决三个挑战：1）岩浆库的规模;2）这些库中的熔体成分和演化; 3）储层的热历史。这些不同的组成部分一起将能够测试储层结构和熔体输送的不同端元模型。其结果是一个严格的评估的性质和演化的岩浆水库下大西洋中脊，与大洋玄武岩的岩浆演化的影响，这可能是一个模板的镁铁质火成岩系统一般。