Denison Scientific Association: Dowsing the shear zone: Deciphering patterns of fluid flow in fault zones

Plate tectonics involves massive forces across immense time scales. Energy from the growth and collapse of mountains is concentrated in narrow zones. These zones of immense strain manifest as fault networks. At sufficient depths, rocks no longer generate earthquakes. Rather, rocks predominantly deform via crystal-plastic mechanisms. Fluids in these faults promote weakening, enhance fracturing, and prompt metamorphic reactions. The isotopic composition of silicate minerals in crystal-plastic shear zones often confirm the presence and provenance of these fluids. In contrast, the absence of an aqueous fluid signature argues for hot, impermeable crust. However, evidence for or against aqueous fluids in the plastic crust is often elucidated across time and space from sparse evidence. Mobilizing fluids, particularly surface derived fluids within rocks at these pressures is mechanically challenging.

Here, I will present the most comprehensive hydrogen and oxygen stable isotope dataset collected to date from a young, enigmatic shear zone in the Peruvian Andes. Pairing isotopic data with radiometric dating and kinematic analysis of features across scales informs the mechanical processes allowing fluid to move in high pressure scenarios and the influence of thermal structure on crystal-plastic fault zones.