The hydrostatic compression of eight rocks

Abstract

The hydrostatic compressions (ΔV/V0) of granodiorite, basalt, dolomite, and tuff (all from the Nevada test site), Indiana limestone, two rock salts, and anhydrite were measured to 46 kb at 25°C. A phase transition was observed in anhydrite (CaSO4) at 19.6±0.5 kb with a volume change of 4.1 per cent. The compression data for granodiorite, basalt, dolomite, tuff, and limestone were in good agreement with dynamic results for similar rocks.

X-ray diffraction and infrared spectroscopy of monazite-structured CaSO4 at high pressures: Implications for shocked anhydrite

“…5). For comparison, previous estimates of the volume change of the transition proposed that about a 4% change in volume exists between the two phases [7,8].…”

“…The solid circles and line represent data from this study for the high-pressure phase. The solid square represents the volume of anhydrite at 2.8 GPa measured in this study, while the line with long dashes is a fit to the compressional data for anhydrite of [7] (extrapolated to higher pressures than the maximum pressure of 2.1 GPa for anhydrite in [7]). Accordingly, the difference between the dashed line and the solid line represents the pressure-dependent volume change of the anhydrite-monazite phase transformation.…”

“…Stephens [7] found an unquenchable high-pressure phase with monoclinic symmetry and the monazite structure at pressures above $3 GPa. The compression of this high-pressure phase has been monitored to $16 GPa, with volumetric data reported to 8.8 GPa [8].…”

“…Additionally, CaSO 4 is known to be abundant within the target rocks of the impact event that produced the extinction of the dinosaurs, and is widely inferred to be the source of atmospheric sulfur-rich gasses associated with that event [5]. Indeed, evidence of a high-pressure phase transition in anhydrite was found in postshot cores shocked by the 1964 Salmon nuclear test, which was conducted within a salt dome near Hattiesburg, Mississippi, USA [6]: the presence of anhydrite near this test site provided the motivation for the first study of high-pressure polymorphism in anhydrite under static conditions [6,7].…”

Crystal chemistry of the monazite structure

“…The increase of pressure can yield to the stabilization of the monazite structure. Many authors 315,317,318,335,384 have observed CaSO 4 undergoing phase transitions from its ambient anhydrite structure to the monazite type at P = 2 GPa, then at higher pressure and temperature to crystallize in the baritetype structure. Bradbury and Williams 317 conducted X-ray diffraction and infrared spectroscopy on CaSO 4 to pressures of 28 and 25 GPa, respectively.…”