Effect of water on the rheology of experimentally deformed quartzite

Abstract

Empirical flow laws have been determined for Simpson quartzite samples deformed to mechanical steady state in the α‐quartz stability field using Griggs‐Blacic solid‐medium deformation apparatus. Experiments were conducted on samples both as received (“dry”) and with water added via the dehydration of a talc confining medium (“wet”). Best fits of the power law type yield a stress exponent of 2.72±0.19, an activation enthalpy of 134±32 kJ mol−1, and a preexponential constant of 1.16 [+1.15, −0.58] × 10−7 MPa−2.72 s−1 for the dry quartzite law; and are 2.61±0.15, 145±17 kJ mol−1, and 5.05 [±5.00] × 10−6 MPa−2.61 s−1 for the wet quartzite. The enhanced hydrolytic weakening of the wet experiments appears to affect the flow laws mostly in the preexponential constants, possibly as a defect concentration term that is higher in the wet than in the dry law. Over the range of experimental conditions (750°–900°C, 10−7 to 10−4 s−1, and 1.0–1.25 GPa confining pressure), dry specimens are 1.5–2.5 times stronger than wet samples deformed at the same conditions. The microstructures produced are analogous to those observed in many natural quartz tectonites. Recrystallization is well developed in the wet but not the dry specimens. At flow stresses below 500 MPa, microstructures indicative of recovery are well developed. A comparison of our creep activation enthalpies with those determined from diffusion experiments are consistent with deformation of wet Simpson quartzite that is limited by oxygen self‐diffusion. Inconsistencies between the present study and previous studies are probably the result of differences in sample material, sample treatment, and sample assemblies (chemical environment).

Ancient heat flow and crustal thickness at Warrego rise, Thaumasia highlands, Mars: Implications for a stratified crust

“…More felsic rocks could imply a higher thermal conductivity, increasing in turn the maximum permitted crustal thickness. If we make the calculations for a dry quartzite rheology (Koch et al, 1989; these authors use the term ''dry" for samples as received, not dried), and a thermal conductivity of 2.5 W m À1 K…”

Late Cretaceous exhumation history of an extensional extruding wedge (Graz Paleozoic Nappe Complex, Austria)

“…On the basis of rheological behaviour of quartz and carbonates, syndeformational temperature regimes can be estimated using theoretical and experimental calibrations (e.g. Brace and Kohlstedt 1980;Carter and Tsenn 1987;Christie and Ord 1980;Tullis 1992, 1994;Koch et al 1989;Okudaira et al 1995). In our case the rheological behaviour of quartz (see ''Temperature estimates from microstructures of quartz veins'' section) is characterized using the terminology of Passchier and Trouw (1996) and Hirth and Tullis (1992).…”

Grain-size-sensitive flow and shear-stress enhancement at the brittle–ductile transition of the continental crust

“…The values of the constants introduced in Eq. (13) are determined from the experimental flow law for dislocation creep found in Koch et al (1989) for quartz and in Shelton (1981) for anorthite and are presented in Table 2 .…”