Solidification in mafic magma chambers

镁铁质岩浆室中的凝固

• 批准号: NE/F018789/1
• 负责人: Elisabetta Mariani
• 金额: $ 3.28万
• 依托单位: University of Liverpool
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FF018789%2F1
• 关键词: Solidification; mafic; magma; chambers

When a chemically complex liquid solidifies it does so over a range of temperatures. During the solidification process a mushy layer develops, in which early-formed solid grains are surrounded by the remaining liquid. This liquid will have a different composition to the solid material, giving rise to numerous possibilities if that fluid were to move within the mush. If it flows to a part of the mush with which it is not in chemical equilibrium there is a complex interaction between the two. The fluid can dissolve the solid, or crystallise in the pore spaces, thus changing the permeability of the matrix and the composition of the solid phase. There may also be changes in pore structure, and thus permeability, due to deformation of the matrix - in the case of the Earth such deformation is most commonly caused by compaction, as the fluid is expelled under the influence of gravity. The problem of flow of reactive fluid is thus highly complex, with many interdependent simultaneous processes. The proposed work is aimed at tackling the first part of this complex problem - that of the progressive development of pore structure within the solidifying mush. We are going to use silicate magmas as a natural laboratory. Magma solidifies on the margins of magma chambers and initially forms a crystal mush through which melts move due to the effects of compaction or replenishment of the chamber. Solidified magmas preserve a record of pore geometry in the way the solid grains fit together. They can also preserve a record of the thermal history via details of the grain boundary orientations. The effects of reaction and diffusive exchange between the solid and the migrating liquid may also be preserved as compositional gradients within mineral grains. It is therefore possible to tease apart the various interacting processes which occurred during the solidification of the magma - thus providing the critical information necessary to understand reactive flow in other, less accessible, environments.

当一种化学复杂的液体在一定的温度范围内凝固时。在凝固过程中，形成一层糊状层，早期形成的固体颗粒被剩余的液体包围。这种液体的组成将与固体物质不同，如果这种液体在糊状物中移动，就会产生许多可能性。如果它流到与之不处于化学平衡的混合体的一部分，两者之间就会发生复杂的相互作用。这种流体可以溶解固体，或在孔隙空间中结晶，从而改变基质的渗透率和固相的组成。由于基质的变形，孔隙结构也可能发生变化，因此渗透率也会发生变化--在地球的情况下，这种变形最常见的原因是压实，因为流体在重力的影响下被排出。因此，反应性流体的流动问题是非常复杂的，有许多相互依赖的同时过程。拟议的工作旨在解决这一复杂问题的第一部分--即固化泥中气孔结构的逐渐发展。我们将使用硅酸盐岩浆作为天然实验室。岩浆在岩浆房的边缘凝固，最初形成晶体泥浆，由于压实或补给岩浆室的影响，熔体在其中流动。凝固的岩浆以固体颗粒结合的方式保存了孔隙几何结构的记录。它们还可以通过晶界取向的细节来保存热历史的记录。固体和迁移液体之间的反应和扩散交换的影响也可以保存为矿物颗粒内的成分梯度。因此，有可能梳理出在岩浆凝固过程中发生的各种相互作用过程，从而提供必要的关键信息，以了解其他较难进入的环境中的反应流动。