Reaction fronts, permeability and fluid pressure development during dehydration reactions
Reaction fronts, permeability and fluid pressure development during dehydration reactions
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DOI：
10.1016/j.epsl.2018.05.005
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发表时间：
2018-08
影响因子：
5.3
通讯作者：
H. Leclère;D. Faulkner;S. Llana-Fúnez;J. Bedford;J. Wheeler
中科院分区：
文献类型：
--
作者：
H. Leclère;D. Faulkner;S. Llana-Fúnez;J. Bedford;J. Wheeler
流体释放的变质作用往往被援引来解释一系列地壳过程，从地震触发到交代作用。根据渗透率、反应速率和压实作用之间的相互作用，这些流体可以被捕获和超压，也可以被释放和通道化。实验数据，测量渗透率，孔隙度和微观结构的演变，整个石膏脱水形成石膏。反应前沿，反应主要发生的区域，被用来作为一个框架来解释的结果。实验在115 °C的恒定温度下在60 MPa和110 MPa的两个有效压力和20、40和60 MPa的三个孔隙流体压力下在静水条件下进行。在高有效压力下，石膏固体框架的蠕变导致低孔隙度和渗透率，产生高孔隙流体压力积聚，从而减慢反应速率。一个明确定义的狭窄反应前沿沿样品沿着迁移，平均渗透率保持较低，直到前沿扫过整个样品。相反，在低有效压力下，反应前沿很宽，产生可渗透的排水网络。通过开放孔隙的互连，在仅一小部分反应完成后，平均渗透率显著提高。这项研究表明，反应前沿的宽度，因此渗透率的发展强烈控制压实。反应前沿速度在很大程度上取决于渗透率和反应驱动力。一个简单的定量模型，这些关系的开发。
Fluids released by prograde metamorphism are often invoked to explain a range of crustal processes from earthquake triggering to metasomatism. These fluids can be either trapped and overpressured or released and channelized depending on the interplay between permeability, reaction rate and compaction. Experimental data are presented, measuring permeability, porosity and microstructural evolution throughout the dehydration of gypsum to form bassanite. Reaction fronts, regions over which the reaction largely occurs, are used as a framework to explain the results. Experiments were conducted under hydrostatic conditions at a constant temperature of 115 °C at two effective pressures of 60 MPa and 110 MPa and three pore-fluid pressures of 20, 40 and 60 MPa. At high effective pressure, creep of the gypsum solid framework results in low porosity and permeability, producing high pore-fluid pressure build-up that slows the reaction rate. A clearly defined narrow reaction front migrates along the sample and the average permeability remains low until the front sweeps across the entire sample. Conversely, at low effective pressure the reaction front is wide producing a permeable, drained network. Average permeability is enhanced significantly after only a small fraction of the reaction has completed, by the interconnection of open pores. This study shows that the width of reaction fronts and hence the permeability development is strongly controlled by compaction. The reaction front velocity is broadly dependent on permeability and the reaction driving force. A simple quantitative model for these relationships is developed.