Solubility and diffusional uptake of hydrogen in quartz at high water pressures: Implications for hydrolytic weakening

Abstract

Attempts to introduce molecular water into dry, natural quartz crystals by diffusive transport and thus weaken them hydrolytically at T = 700°-90(JOC and Pu,o = 400-1550 MPa have failed. Infrared spectroscopy of hydrothermally annealed single crystals of natural quartz reveals the diffusive uptake of interstitial hydrogen (resulting in hydroxyl groups) at rates similar to those previously proposed for intracrystalline water at high water pressures. The solubility of interstitial hydrogen at these conditions is independent of temperature and pressure; instead, it depends upon the initial aluminum concentration by the local charge neutrality condition [H, "] . Deformation experiments following hydrothermal annealing show no mechanical weakening, and the lack of any detectable broadband absorption associated with molecular water shows that the diffusion rates of structural water are much lower than those of hydrogen. These results are consistent with the available oxygen diffusion data for quartz and with the failure to observe weakening in previous studies of quartz deformation at pressures of 300-500 MPa; they call into question the rapid rates of diffusion originally suggested for the hydrolytic weakening defect. It is suggested that the observed weakening in many previous experiments was complicated by microcracking processes in response to nonhydrostatic stresses and low effective confining pressures. Extensive microcracking may prm:ide a mechanism for molecular water to enter quartz and allow local plastic deformation to occur. It does not appear that molecular water can diffuse far enough into uncracked quartz to allow hydrolytic weakening over annealing times that are feasible in the laboratory.

Synchrotron FTIR imaging of OH in quartz mylonites

“…We know little of this early brittle deformation, but these fluid inclusion arrays have microstructures similar to those generated during hydrothermal diffusional healing of cracks (Smith and Evans, 1984;Beeler and Hickman, 2015). As a result, early brittle deformation, infiltration of water along open cracks, and crack healing appear to be important to the early introduction of water to quartz grain interiors (Kronenberg et al, 1986FitzGerald et al, 1991;Diamond et al, 2010;Tarantola et al, , 2012Stünitz et al, 2017).…”

“…The large and variable water contents of quartz mylonites are far above equilibrium solubilities (e.g., Paterson, 1986;Kronenberg et al, 1986;Cordier and Doukhan, 1989), and the variations in non-equilibrium OH content probably reflect some part of the history of water migration during deformation. Images of contoured OH absorbances of the broad 3400 cm −1 band for quartz and the 3600 cm −1 bands of micas constructed for MT and MCT samples show relationships with optical deformation and recovery microstructures that suggest mechanisms by which water is incorporated in quartz grain interiors, how water becomes redistributed during deformation and recovery, and how water is lost from quartz grain interiors.…”

Spectroscopic Estimation of Geometrical Structure Elucidation in Natural SiO<SUB>2</SUB> Crystal

“…Information about structural defects in quartz crystals can be obtained from Fourier-transform infrared (FTIR) spectroscopy [6][7][8][9][10][11]. The crystal structure analysis discussed here is necessary to investigate the correlation between the trace oxide inclusions; characteristic infrared band shift and crystal face size in the crystal growth [12].…”

The infrared absorption band at 3596 cm−1 of the recrystallized quartz from Mt. Takamiyama, southwest Japan

“…An absorption band at 3596 cm -1 has been observed in amethyst (Chakraborty and Lehmann, 1976a, b;Rovetta et al, 1989), clear Brazilian single crystals (Kronenberg et al, 1986), chalcedony (Frondel, 1982), synthetic quartz crystals (Kats, 1962;Chakraborty and Lehmann, t976a,b) and in synthetic smoky quartz (Pankrath, 1991). In these cases, the 3596 cm -1 bands were either very weak or faint.…”

“…Figure 8 shows the plot of the trace elements of Li, Na, A1, K and Fe (atom/106Si) in the quartz previously reported (Kats, 1962;Kronenberg et al, 1986;Rovetta et al, 1989;Pankrath, 1991) vs the absorbance of the 3596 cm -1 band. Although there seems to be no correlation between the trace element content and the absorbance, all the samples have low A1 contents.…”