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Solidification in mafic magma chambers

镁铁质岩浆室中的凝固

基本信息

批准号：
NE/F020325/1
负责人：
Marian Holness
金额：
$ 23.97万
依托单位：
University of Cambridge
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2009
资助国家：
英国
起止时间：
2009 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FF020325%2F1
关键词：
Solidification mafic magma chambers

项目摘要

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.

当一种化学成分复杂的液体在一定温度范围内凝固时。在凝固过程中，形成糊状层，其中早期形成的固体颗粒被剩余的液体包围。这种液体将具有与固体材料不同的成分，如果该流体在糊状物中移动，则会产生多种可能性。如果它流到糊状物的一部分，而它与糊状物不处于化学平衡，则两者之间存在复杂的相互作用。流体可以溶解固体，或在孔隙中结晶，从而改变基质的渗透性和固相的组成。由于基质的变形，孔隙结构也可能发生变化，因此渗透率也可能发生变化-在地球的情况下，这种变形最常见的是由压实引起的，因为流体在重力的影响下被排出。因此，反应流体的流动问题是高度复杂的，具有许多相互依赖的同时过程。拟议的工作是为了解决这个复杂的问题的第一部分-孔结构内的固化糊状物的逐步发展。我们将把硅酸盐岩浆作为天然实验室。岩浆在岩浆房的边缘凝固，最初形成一种晶体糊状物，由于岩浆房的压实或补充作用，熔体在其中移动。凝固的岩浆以固体颗粒结合在一起的方式保存了孔隙几何形状的记录。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作为矿物颗粒内的成分梯度保留。因此，有可能梳理出岩浆凝固过程中发生的各种相互作用过程-从而提供了解其他不易进入的环境中的反应流所需的关键信息。