Refinement of the α–β quartz phase boundary based on in situ Raman spectroscopy measurements in hydrothermal diamond‐anvil cell and an evaluated equation of state of pure H₂O

Abstract

In this study, we determined the α–β quartz phase transition temperatures (Ttrs; up to ~924°C for a total of 23 obtained under 0.1 MPa and elevated pressures) in a hydrothermal diamond‐anvil cell (HDAC) at H2O pressures up to ~1310 MPa by using in situ Raman spectroscopy. When compared with the commonly used α‐quartz Raman band near 465 cm−1 (at 24°C and 0.1 MPa), the one near 128 cm−1 is much more sensitive for detecting Ttr. The corresponding phase transition pressure (Ptr) at each measured Ttr was calculated from three equations of state (EoS) of pure H2O. The corresponding three α–β quartz phase boundaries were compared with those derived from previous experimental results. The best fitted one can be represented by: Ptr (±5.6 MPa) = 0.0008·Ttr2 + 2.8056·Ttr − 1877.5, where 574°C ≤ Ttr ≤ 889°C with R2 = 0.9998. Our results agree, within experimental uncertainties, with most of previous experimental data, and our newly determined α–β quartz Ptr–Ttr phase boundary can be used as a reliable pressure calibrant in HDAC. Furthermore, the experimental procedures used in this study, including the use of Raman spectroscopy criterion for Ttr determination, can be easily applied to obtain improved EoS of geologically important aqueous solutions containing salt(s) at pressure–temperature conditions up to ~1.2 GPa–900°C.

Alkali-Induced Phase Transition to β-Spodumene along the LiAlSi2O6-LiAlSi4O10 Join

“…The υ s (T-O-T) Raman band of β-spodumene ss shifts from 495 cm −1 in LiAlSi 2 O 6 to 492 cm −1 in LiAlSi 2.9 O 7.8 (Figure 11a). In the case of β-quartz ss (Figure 11b), a band at 483 cm −1 , consistent with the υ s (T-O-T) frequency observed for LiAlSi 2 O 6 composition [38], also moves to lower frequency with increasing silica and the associated progressive growth of a shoulder at 455 cm −1 , more akin to the frequency observed in pure SiO 2 endmember β-quartz [44], may indicate a growing contribution of oxygen bridging two Si cations (Si-O-Si) relative to Si-O-Al linkages [40]. The observed strong preferential partitioning of sodium in β-spodumeness indicates that a slight increase in its concentration can minimize the extent of β-quartzss formation.…”

Water Recycling in the Deep Earth: Insights From Integrated μ‐XRF, THz‐TDS Spectroscopy, TG, and DCS of High‐Pressure Granulite

“…As the phase transformation of α‐β quartz occurs at a temperature range of ca. 574–890°C, quartz in the studied high‐pressure mafic granulite might have been stabilized at a temperature range of <850–1,000°C (Figure 8), indicating phase transformation and water release during the subduction dehydration process (Li & Chou, 2022; Mechie et al., 2004; Y. Wang et al., 2021; Wu et al., 2023). Therefore, quartz from the rutile‐bearing garnet amphibolite might contain only minor contents of water.…”