The low‐high quartz and quartz‐coesite transition to 40 kbar between 600° and 1600°C and some reconnaissance data on the effect of NaAlO₂ component on the low quartz‐coesite transition

Abstract

The phase relations of low quartz, high quartz, and coesite were reinvestigated using extremely pure SiO2. The study was conducted with a piston-cylinder apparatus employing low-friction cells. While the low quartz-coesite transition between 600 ø and 1100øC was determined by conventional quench techniques, the greater portion of this study relied on in situ methods (differential thermal analysis and a volumetric method referred to as differential pressure analysis). The agreement with previous results is good; however, the precision of present data is considerably higher. A comparison of our salt-cell data with the raw data of previous studies shows a pressure loss due to friction of about 10% for talc cells. A discussion of thermochemical aspects of the low quartz-coesite transition indicates improved agreement between thermodynamic and experimental data. Reconnaissance data on the influence of the NaAIO2 component show above 600øC in the absence of H20 a considerable shift of the quartz-coesite boundary toward higher pressure (4 kbar at 1100øC). In the presence of H20 a partial liquid is formed, and the shift is reversed; the transition boundary is reduced 3 kbar and lies between 680 ø and 1000øC at even lower pressure than that of the pure SiO2 modifications.

Raman mapping of coesite inclusions in garnet from the Kokchetav Massif (Northern Kazakhstan)

“…They found that Raman shift of most intense quartz band at 1081 and 464 cm −1 is about 1.5 and 3.7 cm −1 /GPa. Pressure estimates for quartz, using their calibration are 3-3.6 GPa, significantly higher than the equilibrium pressure of P eq = 2.0-2.2 GPa [37]. In our case quartz occurs as polycrystalline aggregates with lattice-preferred orientation and Raman shift of such quartz should be about 5-6 cm −1 /GPa to satisfy equilibrium conditions at room temperature.…”

OH defects in quartz in granitic systems doped with spodumene, tourmaline and/or apatite: experimental investigations at 5–20 kbar

“…Based on the present results most of the shift in the reaction seems to occur at a rather narrow pressure interval, namely between 10 and 15 kbar. In this pressure interval falls the transition from high-quartz to low-quartz (Mirwald and Massonne 1980). If the high-/low-quartz transition were relevant for the preferred incorporation of LiAl defects, we would expect lower LiAl defects at high pressure, because LiAlSi 2 O 6 can crystallize in high-quartz structure (London 1984), which is stable below 13 kbar.…”

Aragonite-calcite-dolomite relationships in UHPM polycrystalline carbonate inclusions from the Kokchetav Massif, northern Kazakhstan

“…Experimental study (L) of Luth (2001) on the reaction dolomite (dol) ¼ aragonite (ara) þ magnesite (mag). Graphite-diamond and coesite-quartz transitions are from Kennedy & Kennedy (1976) and Mirwald & Massonne (1980). The retrograde evolution shown as (A)-(C) is taken from .…”