The pyroclastic rocks of "The Crater", South Island, New Zealand belong to the Miocene, alkaline basaltic Dunedin Volcanic Group and represent an individual eruptive center with possible multiple vents. Three pyroclastic units have been separated at the study area based on textural and compositional features as well as their stratigraphic positions. The central part of The Crater comprises basa...

The THz spectrum of density fluctuations, S(Q, ω), of vitreous GeO2 at ambient temperature was measured by inelastic x-ray scattering from ambient pressure up to pressures well beyond that of the known α-quartz to rutile polyamorphic (PA) transition. We observe significant differences in the spectral shape measured below and above the PA transition, in particular, in the 30-80 meV range. Guided...

Single-crystal X-ray diffraction experiments on e-quartz at pressures to 15 GPa reveal structural instabilities that result in its gradual transition to an amorphous state. With increasing pressure the average Si-O distance ( ~ 1.61 + 0.01/~) and S i O 4 tetrahedral volume (,,~2.14 ___ 0.02.~ 3) remain constant. Compression of e-quartz results from a dramatic decrease in Si-O-Si angle and corre...

To predict phase transitions in ceramics and minerals from molecular dynamics simulations, we have developed a force field in which the charges are allowed to readjust instantaneously to the atomic configurations. These charges are calculated using the charge equilibration (QEq) method. In addition to electrostatics, a two-body Morse stretch potential is included to account for shortrange nonel...

The solubility of quartz in H2O-NaCl solutions was measured at 2, 4.35, 10 and 15 kbar and 500–900°C, and at NaCl concentrations up to halite saturation, usually greater than 75 wt.%. Quartz solubility was also measured in CO2-H2O solutions at 10 kbar and 800°C. Solubilities were determined by weight loss of ground and polished quartz crystal fragments which were equilibrated with solutions in ...

The deposition of asphaltenes in porous media, an important problem in science and macromolecular engineering, was for the first time investigated in a transparent packed-bed microreactor (μPBR) with online analytics to generate high-throughput information. Residence time distributions of the μPBR before and after loading with ~29 μm quartz particles were measured using inline UV-Vis spectrosco...

Abstract Elastic geothermobarometry relies on the contrast between thermal expansion and compressibility of a mineral inclusion its surrounding host, leading to residual pressure in ( P inc ) that may differ significantly from external pressure. Quartz-in-garnet (QuiG) inclusion-host systems are widely used elastic estimate entrapment conditions thus rock petrogenesis. To elucidate behaviour Qu...

A chloritoid schist from the Medvednica Mts. (Croatia, Zagorje-Mid-Transdanubian zone) is part of metasedimentary succession a Palaeozoic-Mesozoic Metamorphic Complex. The studied samples show mineral association chloritoid, chlorite, quartz and white mica. P-T pseudosection, combined with modal chemical isopleths, classical thermobarometric calculations yield peak metamorphic conditions 0.8 – ...

– X-ray diffraction (XRD) experiments have been carried out on quartz-like α−GaPO4 at high pressure and room temperature. A transition to a high pressure disordered crystalline form occurs at 13.5 GPa. Slight heating using a YAG infrared laser was applied at 17 GPa in order to crystallize the phase in its stability field. The structure of this phase is orthorhombic with space group Cmcm. The ce...

The Leech River Shear Zone (LRSZ) on southern Vancouver Island separates the metasedimentary schists of Complex (LRC) from accreted oceanic plateau Siletz-Crescent terrane. juxtaposition these rock units suggests a possible origin as subduction plate boundary but tectonic context LRSZ has yet to be fully established. We present field, microstructural, petrological, and geochronological observat...