Magma-driven hydraulic fracturing and infiltration of fluids into the damaged host rock, an example from Dronning Maud Land, Antarctica

Abstract

Excellent outcrops in Dronning Maud Land, Antarctica, provide unique insight into the mode and extent of fluid infiltration into metamorphic and plutonic rocks in the middle crust. The fluids are liberated from pegmatitic veins and give rise to alteration halos. In the alteration halos, the conspicuous change in colour is correlated with (1) hydration mineral reactions, and (2) high density of microcracks in quartz and feldspar exceeding that observed in the unaltered host rock by an order of magnitude. The field relations indicate that the veins originated as melt-driven hydraulic fractures, sealed by pegmatite and aplite crystallising from volatile-rich melts, with the alteration halo being the wake of the process zone formed at the tip of the propagating fractures. It is proposed that (1) the size of the alteration zone and the width of the vein are correlated, resulting in higher values of both these quantities for cracks propagating at higher velocities and consequently higher crack propagation toughnesses; (2) the damage zone is characterised by a transient state of high permeability which was short-lived due to rapid healing and sealing of microcracks; (3) the infiltration and retrogression of the high-grade rocks can be considered as a quasi-instantaneous process on geologic time scales with a duration of hours to weeks. q

Albitization of Granitic Rocks: The Mechanism of Replacement of Oligoclase by Albite

“…2). Fracturing has been demonstrated as fluid-transport channels in a deep-crustal environment (e.g., austrheim 1987, Pennacchioni 1996, Kostenko et al 2002, and at higher crustal levels (e.g., Bons 2001, Engvik et al 2005, on the outcrop scale as well as the microscale (e.g., Fitz Gerald & Stünitz 1993, Oliver 1996, Engvik et al 2001. the microtextures described from the albitites (Fig.…”

Common Evolution of Mechanical and Transport Properties in Thermally Cracked Westerly Granite at Elevated Hydrostatic Pressure

“…Seismic and velocity field data and its relation to complex, coupled phenomena is important and has a role in many applied engineering fields, such as enhanced oil production methods, hydro-fracturing, and the improved understanding of the stability of underground waste repositories (RUTQVIST et al, 2005;ENGVIK et al, 2005). By performing controlled thermal cracking experiments, we investigate quantitatively the influence of thermal damage on fracture toughness, elastic wave velocity, and permeability.…”

Fracture Toughness and Fracture Roughness Interrelationship in Thermally treated Westerly Granite

“…It has been identified as the cause of reduced strength and enhanced permeability of rock near magmatic intrusions (e.g., ENGVIK et al, 2005), geothermal reservoirs (e.g., PEARSON et al, 1983;GHASSEMI et al, 2007), and underground nuclear waste disposal sites (e.g., HUDSON et al, 2001;RUTQVIST et al, 2005). Furthermore, exposure of fault planes to increased temperature has been found to reduce the coefficient of friction and lead to the stabilization of fault slip (BLANPIED et al, 1998).…”