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。当上地幔因板块分离而隆起并部分融化时，就形成了洋壳。由此形成的熔体向上上升，形成下洋壳的岩浆库，并喷发形成洋中脊玄武岩。洋中脊岩浆库的性质仍然缺乏约束。传统模型认为它们是纯熔体，其中岩浆演化受分步结晶控制。这种模型受到越来越多的挑战，现在出现了一种新的范式，其中岩浆库由晶体糊（熔体和晶体的混合物）组成。糊状储层中的熔体输送和演化可能受到多孔流的控制，这对大洋中脊玄武岩的喷发动力学和地球化学特征具有根本意义。该项目将重建大西洋中脊岩浆储层的结构和演化。它将利用通过科学海洋钻探从 U1309D 孔（北纬 30 度）中回收的岩心。先前在该地点的钻探表明，该剖面包含缓慢扩张的洋中脊下方的化石岩浆储层的良好记录。该项目将岩心观测与最先进的元素测绘和主要矿物测量相结合。和微量元素来解决三个挑战：1）岩浆储层的大小；2）这些储层内的熔体成分和演化；3）储层的热历史。这些不同的组件一起将能够测试不同的端元储层结构和熔体传输模型。结果是对大西洋中脊下方岩浆库的性质和演化进行了严格的评估，对海洋玄武岩的岩浆演化具有影响，这通常可以作为镁铁质火成岩系统的模板。