Solidification in mafic magma chambers

当一种化学复杂的液体凝固时，它会在一定的温度范围内凝固。在凝固过程中形成糊状层，早期形成的固体晶粒被剩余的液体包围。这种液体与固体物质的成分不同，如果这种液体在糊状物中移动，就会产生许多可能性。如果它流到与它不处于化学平衡的糊状物的一部分，那么两者之间就会发生复杂的相互作用。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，因此渗透率也可能发生变化——就地球而言，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高度复杂的，有许多相互依存的同时发生的过程。提出的工作旨在解决这一复杂问题的第一部分-固化糊状内孔隙结构的逐步发展。我们要用硅酸盐岩浆作为天然实验室。岩浆在岩浆房的边缘凝固，最初形成一种晶体糊状，由于压实作用或岩浆房的补充作用，岩浆会融化。凝固的岩浆以固体颗粒组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存下来。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，从而提供必要的关键信息，以了解其他不易接近的环境中的反应性流动。

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.