Pore Fluid Extraction by Reactive Solitary Waves in 3‐D

Abstract

In the lower crust, viscous compaction is known to produce solitary porosity and fluid pressure waves. Metamorphic (de)volatilization reactions can also induce porosity changes in response to the propagating fluid pressure anomalies. Here we present results from high‐resolution simulations using Graphic Processing Unit parallel processing with a model that includes both viscous (de)compaction and reaction‐induced porosity changes. Reactive porosity waves propagate in a manner similar to viscous porosity waves, but through a different mechanism involving fluid release and trap in the solid by reaction. These waves self‐generate from red noise or an ellipsoidal porosity anomaly with the same characteristic size and abandon their source region to propagate at constant velocity. Two waves traveling at different velocities pass through each other in a soliton‐like fashion. Reactive porosity waves thus provide an additional mechanism for fluid extraction at shallow depths with implications for ore formation, diagenesis, metamorphic veins formation, and fluid extraction from subduction zones.

A New Mechanism for Upper Crustal Fluid Flow Driven by Solitary Porosity Waves in Rigid Reactive Media?

“…Porosity waves, in this view, are restricted to the remotest, hottest, and most ductile regions—this situation is represented in Figure a. In contrast, the equations derived by Omlin et al () indicate that porosity waves may exist through the entire depth regime depicted in Figure (e.g., Figure b). Indeed, as noted above, kinetically controlled porosity waves may be more prominent at shallower depths and cooler temperatures.…”

“…Omlin et al () provide the first cornerstones of a bridge between these various structures. They demonstrate that porosity waves may be generated not only by deformation in the ductile domain but also by kinetic control on the fluid producing reactions.…”

“…Figure illustrates schematically how the conceptual development initiated by Omlin et al () might modify our view of fluid flow within the Earth and the new questions that may emerge. Currently, porosity waves are thought to be prevalent in high temperature, ductile domains at depth.…”

“…The situation is further complicated by the fact that conventional solutions of Darcy's law equations in undeforming media that yield uniform flow regimes and porosity waves may leave very similar signatures in the rock record (e.g., Tian & Ague, 2014). Omlin et al (2017) provide the first cornerstones of a bridge between these various structures. They demonstrate that porosity waves may be generated not only by deformation in the ductile domain but also by kinetic control on the fluid producing reactions.…”

“…Indeed, kinetic controls on processes are generally more dominant at lower temperatures, and therefore, in contrast to the viscous deformation related porosity waves, the kinetically controlled porosity waves may be more prominent in lower temperature, shallower, and more accessible sections of the Earth. Figure 1 illustrates schematically how the conceptual development initiated by Omlin et al (2017) might modify our view of fluid flow within the Earth and the new questions that may emerge. Currently, porosity waves are thought to be prevalent in high temperature, ductile domains at depth.…”