Abstract
Quartz is able to incorporate trace elements (e.g., H, Li, Al, B) depending on the formation conditions (P, T, and chemical system). Consequently, quartz can be used as a tracer for petrogenetic information of silicic plutonic bodies. In this experimental study, we provide the first data set on the OH defect incorporation in quartz from granites over a pressure/temperature range realistic for the emplacement of granitic melts in the upper crust. Piston cylinder and internally heated pressure vessel synthesis experiments were performed in a water-saturated granitic system at 1–5 kbar and 700–950 °C. Crystals from successful runs were analysed by secondary ion mass spectrometry (SIMS) and Fourier transform infrared (FTIR) spectroscopy, and their homogeneity was verified by FTIR imaging. IR absorption bands can be assigned to specific OH defects and analysed qualitatively and quantitatively and reveal that (1) the AlOH band triplet at 3310, 3378 and 3430 cm−1 is the dominating absorption feature in all spectra, (2) no simple trend of total OH defect incorporation with pressure can be observed, (3) the LiOH defect band at 3470–3480 cm−1 increases strongly in a narrow pressure interval from 4 kbar (220 µg/g H2O) to 4.5 kbar (500 µg/g H2O), and declines equally strong towards 5 kbar (180 µg/g H2O). Proton incorporation is charge balanced according to the equation H+ + A+ + P5+ = M3+ + B3+, with A+ = alkali ions and M3+ = trivalent metal ions.
Highlights
Quartz is the second most abundant mineral in the Earth’s crust and an important rock-forming constituent in igneous, metamorphic and sedimentary rocks as well as unconsolidated sedimentary material (Ronov and Yaroshevski 1969)
IR spectra give rise to absorption bands at specific wavenumbers that can be assigned to particular hydrous defects: (1) the substitution Si4+ = Al3+ + H+ is thermally rather stable and is responsible for the band triplet at 3310, 3378 and 3430 cm−1 (Kats 1962; Bambauer 1963; Aines and Rossman 1984; Rovetta 1989; Stalder and Konzett 2012), (2) the interstitial LiOH defect leads to an absorption band in the range of 3470–3482 cm−1 (Kats 1962; Aines and Rossman 1984; Baron et al 2015), while (3) the absorption band at 3595 cm−1 is related to the substitution Si4+ = B3+ + H+ and called BOH defect (Müller and Koch-Müller 2009), usually associated with late-stage granitic to pegmatitic origin
We present the first systematic experimental data set on the OH defect incorporation in quartz from a natural granitic starting material at 1–5 kbar, representing relevant conditions of granite genesis in upper to mid crustal levels
Summary
Quartz is the second most abundant mineral in the Earth’s crust and an important rock-forming constituent in igneous, metamorphic and sedimentary rocks as well as unconsolidated sedimentary material (Ronov and Yaroshevski 1969). IR spectra give rise to absorption bands at specific wavenumbers that can be assigned to particular hydrous defects: (1) the substitution Si4+ = Al3+ + H+ (referred to as AlOH defect) is thermally rather stable and is responsible for the band triplet at 3310, 3378 and 3430 cm−1 (Kats 1962; Bambauer 1963; Aines and Rossman 1984; Rovetta 1989; Stalder and Konzett 2012), (2) the interstitial LiOH defect leads to an absorption band in the range of 3470–3482 cm−1 (Kats 1962; Aines and Rossman 1984; Baron et al 2015), while (3) the absorption band at 3595 cm−1 is related to the substitution Si4+ = B3+ + H+ and called BOH defect (Müller and Koch-Müller 2009), usually associated with late-stage granitic to pegmatitic origin. A subordinate band at 3585 cm−1 is assigned to a defect analogous to
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