Cavitation erosion – a possible cause of the mass loss within thrust zones in the Tatra Mts., Poland

Abstract

In the Tatra Mts., thrust-napping and shearing were multi-stage re-activated processes. Their cyclic character was determined by increases and decreases in pore fluid pressure. During each cycle, new parts of the rheologically heterogeneous wall-rock were selectively destroyed due to hydraulic fracturing, brecciation and mylonitization, and moved out as a solution and/or suspension. As a result of these processes, including pressure solution, considerable mass loss could have taken place. All these processes took place under the considerable influence of fluids. In this paper we consider the possible contribution of cavitation erosion to mass loss processes. Displacement along an uneven thrust surface could create chambers filled with fluid and sudden falls in local pressure promoting the inception of cavitation. Cavitation damage, mainly mechanical in nature, could act synergistically with slurry abrasion and pressure solution processes.

Our work is of a hypothetical character. To prove the possibility of cavitation erosion within shear zones in the Tatra Mts. we conducted an experiment to show the low resistance of rock samples to cavitation erosion. We also discuss and characterize the conditions essential to induce cavitation within thrust zones at the base of nappes.