Diffusion and kinetic control of weathering layer development
Diffusion and kinetic control of weathering layer development
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风化层发育的扩散和动力学控制
DOI：
10.1111/gfl.12056
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发表时间：
2014
期刊：
影响因子：
1.7
通讯作者：
D. Rothman
中科院分区：
文献类型：
--
作者：
D. Reeves;D. Rothman
岩石外部多孔风化壳（化学蚀变层）的形成是孔隙内矿物-流体界面处发生的矿物溶解和沉淀的结果。发达的果皮前进的速度是由动力学反应速率和运输的反应产物远离孔隙空间到外部流体控制。我们表明，使用反应扩散理论和数值，扩散限制下，风化率取决于样品的大小和曲率。这导致了果皮厚度δ和年龄t之间的关系。随着外壳变厚，三维的结果与一维的结果有很大的不同。我们描述的条件下，一维和扩散限制近似适用，以及它们如何演变为岩石风化。在化学动力学的限制下，果皮以恒定的速率dδ/dt = v前进。我们捍卫应用球形近似不规则的非球形岩石，并将我们的研究结果应用于文献中报道的现场观测，以显示与既定方法的一致性。最后，我们认为，在尺寸上的变化，以及在矿物学上，超过合奏的颗粒有助于异质风化率。我们证明，这种异质性可以有助于老化，或随着时间的推移逐渐减少，以前在实验室和现场测量中观察到的风化率。
The formation of porous weathering rinds (layers of chemical alteration) on the exterior of rocks is a consequence of dissolution and precipitation of minerals occurring at the mineral–fluid interface within the pores. The speed at which the developed rind advances is controlled by both kinetic reaction rates and the transport of reaction products away from the pore spaces into the outside fluid. We show, using both reaction-diffusion theory and numerics, that under diffusion limitations, the weathering rate depends on the size and curvature of the sample. This leads to a relationship between rind thickness, δ, and age, t. As the rind thickens, the result in three dimensions differs substantially from the one-dimensional result of δ˜t. We describe the conditions under which the one-dimensional and diffusion-limited approximations apply and how they evolve as the rock weathers. Under chemical kinetic limitations, the rind advances at a constant rate, dδ/dt = v. We defend the application of a spherical approximation to irregular non-spherical rocks and apply our results to field observations reported in the literature to show consistency with established methods. Finally, we argue that the variability in size, as well as in mineralogy, over ensembles of grains contributes to heterogeneous weathering rates. We demonstrate that this heterogeneity can contribute to the aging, or gradual decrease with time, of weathering rates previously observed in laboratory and field measurements.