Transient Porosity Resulting from Fluid–Mineral Interaction and its Consequences
Transient Porosity Resulting from Fluid–Mineral Interaction and its Consequences
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DOI：
10.2138/rmg.2015.80.01
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发表时间：
2015
影响因子：
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通讯作者：
A. Putnis
中科院分区：
文献类型：
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作者：
A. Putnis
孔隙度这个术语在地学中被广泛使用，通常指的是岩石中矿物颗粒或有机物质之间的空间，以总体积的一部分来衡量。这些空间可能充满气体或流体，因此讨论孔隙度最常见的背景是沉积岩的水文地质学和石油地质学。孔隙度是衡量岩石包括流体相的能力的指标，渗透率是衡量流体通过岩石流动的能力的指标，因此取决于孔隙空间的相互联系程度、孔隙分布和孔颈大小，以及驱动流动的压力。本章将主要讨论反应性流体如何通过固有渗透率非常低的致密岩石，以及次生孔隙度是如何由流体-矿物反应产生的。关于标题的意义，几句话将有助于解释本章的范围：1.“流体-矿物相互作用”：当矿物与流体失去平衡时，它会倾向于溶解，直到流体相对于固体矿物饱和。我们将流体视为水溶液，尽管这里描述的许多原理也适用于熔体。通过简单地溶解岩石中的一些矿物来产生孔隙度是增强流体流动的一种明显方式。碳酸盐被低pH溶液溶解以产生洞穴甚至洞穴就是一个例子。然而，当考虑到变质作用中流体-矿物反应的作用时，流体提供了使岩石重新平衡的机制，即通过用更稳定的组合取代一组矿物。这不仅涉及母矿物相的溶解，而且还涉及…
The term porosity is very widely used in geosciences and normally refers to the spaces between the mineral grains or organic material in a rock, measured as a fraction of the total volume. These spaces may be filled with gas or fluids, and so the most common context for a discussion of porosity is in hydrogeology and petroleum geology of sedimentary rocks. While porosity is a measure of the ability of a rock to include a fluid phase, permeability is a measure of the ability for fluids to flow through the rock, and so depends on the extent to which the pore spaces are interconnected, the distribution of pores and pore neck size, as well as on the pressure driving the flow. This chapter will be primarily concerned with how reactive fluids can move through ‘tight rocks’ which have a very low intrinsic permeability and how secondary porosity is generated by fluid–mineral reactions. A few words about the meaning of the title will help to explain the scope of the chapter: 1. “Fluid–mineral interaction”: When a mineral is out of equilibrium with a fluid, it will tend to dissolve until the fluid is saturated with respect to the solid mineral. We will consider fluids to be aqueous solutions, although many of the principles described here also apply to melts. The generation of porosity by simply dissolving some minerals in a rock is one obvious way to enhance fluid flow. Dissolution of carbonates by low pH solutions to produce vugs and even caves would be one example. However, when considering the role of fluid–mineral reaction during metamorphism the fluid provides mechanisms that enable re-equilibration of the rock, i.e., by replacing one assemblage of minerals by a more stable assemblage. This not only involves the dissolution of the parent mineral phases, but the …