Subduction is a key element in the carbon cycle between the Earth's surface and deep interior. In addition to pressure (P) and temperature (T), oxygen fugacity (ƒO 2) is an intensive variable that can change the speciation, stability, and mobility of carbon-bearing phases in subduction zones.However, tracking redox evolution and associated …

Pyrite-structured Co 0.2 Fe 0.8 S 2 nano wires with aspect ratio 45:1, synthesized using solution colloid method were studied under high pressure up to 8 GPa using 57 Fe Möss spectroscopy (using diamond anvil cell) and electrical resistivity (using tungsten carbide cell) techniques. Room temperature S K-edge XANES studies at …

Using a Nd-doped Y 3 Al 5 O 12 laser system 7 to heat the sample to 1,800 K in situ at high pressure, the sample became semi-transparent, suggesting that a chemical reaction had occurred.

X-ray diffraction measurements showed that a high-pressure form with a pyrite-type structure, denser than other known silica phases, is stable above 268 giga-pascals and 1800 kelvin. The silicon coordination number increases from 6 in the alpha-PbO2-type phase to 6+2 in the pyrite-type phase, leading to a large increase in density …

The pretreatment of pyrite cinder was studied using high pressure roll grinding (HPRG), which aims to improve the quality of green pellets and reinforce roasting performance of pyrite cinder ...

Pyrite-type FeOOH may stabilize as a solid solution with other hydrous minerals in deeply subducted slabs, and could form in subducted banded iron formations. Deep-seated pyrite-type FeOOH eventually dissociates into Fe 2 O 3 and releases H 2 O when subducted slabs are heated at the base of the mantle. This process may cause the …

The pyrite-type FeO 2 was proposed recently as a new structure that exists in the deep Earth. Taking into account the influence of temperature, we investigated the stability and elastic properties of pyrite-type FeO 2 under high pressure. The obtained lattice constants and bulk modulus agree well with the available experimental and …

The chemical reaction of group-14 elements with molecular nitrogen at pressures above 60 GPa successfully leads to the formation of pyrite-type pernitrides, which offer significant new progress in the solid-state chemistry of nitrides. The chemical reaction of group-14 elements with molecular nitrogen at pressures above 60 GPa …

The Pyrite-Type High-Pressure Form of Silica. sets of parameters. Keeping w± fixed, the L/d are chosen (Fig. 2A) so that all the lines intersect the data point for the …

It is, therefore, important to study the physical and chemical properties of pyrite at high-pressure and high-temperature conditions. Previous studies have shown that, possibly due to the low-spin ...

The pyrite particle was cylindrical and was formed by pressing pyrite powder under high pressure. The pyrite pellet was 6.25 mm in both diameter and length. Based on the observed linear relationship between the unreacted core radius and the reaction time, it was concluded that the decomposition process was controlled by chemical reaction.

the high-pressure behaviour of hydroxides in the deep Earth. FeOOH, AlOOH and SiO 2 have the same CaCl 2 -type crystal struc - ture at high pressure, and SiO 2 and δ-AlOOH transform into pyrite-

X-ray diffraction measurements showed that a high-pressure form with a pyrite-type structure, denser than other known silica phases, …

Over the wide pressure range investigated here, all vibrational frequencies depend nonlinearly on pressure; their pressure dependence is quantified by determining the full set of mode Grüneisen parameters and their pressure derivatives. Plane-wave density functional calculations are used to investigate the pressure dependence of the …

X-ray diffraction measurements showed that a high-pressure form with a pyrite-type structure, denser than other known silica phases, is stable above 268 giga-pascals and 1800 kelvin. The silicon coordination number increases from 6 in the α-PbO2-type phase to 6+2 in the pyrite-type phase, leading to a large increase in density by …

3.2. Simultaneous High-Temperature and High-Pressure Study of Pyrite Water reacts with pyrite as a function of temperature, pressure, and time. To avoid the reaction between water and pyrite, methanol–ethanol (4:1) was used as a pressure medium instead of a 20 wt.% NaCl solution [16] to provide hydrostatic pressure.

An analogous, high-pressure phase transition from CaCl 2-type ϵ-FeOOH (Figure 1a) to pyrite-type FeO 2 H (Figure 1b) was discovered by high-pressure experimentalists in the past few years, but the stoichiometry and properties of this phase remain contested (Hu et al., 2016, 2017; Liu et al., 2017; Nishi et al., 2017; L. Yuan et al., …

Thus, pyrite breakdown to pyrrhotite reactions operating during subduction metamorphism should produce oxidized Fe-depleted peak mineral assemblages in exhumed high-pressure rocks. Additionally, the low solubility of reduced sulfur species in rock-buffered systems suggests that sulfides may continue to persist in the slab (Evans …

Variations in the Raman spectra of pyrite were studied from 113 to 853 K at room pressure with a Linkam heating and freezing stage, and for 297–513 K and pressures up to 1.9 GPa with a hydrothermal …

The changing trends in the lattice energy of the same substance under a high pressure are the same as that of 1/R 0. Under a high pressure, the distance between ions in pyrite decreases due to compression, and the lattice energy increases accordingly. The lattice energy of pyrite shows the most obvious increase between 0–3 GPa (Fig. 3(a ...

Large pyrite grains in the matrix contain inclusions of garnet, omphacite and other HP index minerals. However, magnetite replacing pyrite textures are commonly observed in the retrograded samples. ... Berry RF, Green DH (1991) High pressure experimental calibration of the olivine-orthopyroxene-spinel oxygen geobarometer: …

Our results indicate a phase transition around 70 GPa from the known ε-FeOOH to a new pyrite-type FeOOH (P-FeOOH) phase, and the two phases remain …

Pressure dependence of unit-cell volume and lattice parameters. The left panel shows the plot of unit-cell volume as a function of pressure for phase H with ordered Mg and Si atoms (model-1 ...

Plane-wave density functional calculations are used to investigate the pressure dependence of the geometry and Γ-point phonons of FeS2 pyrite up to 150 GPa. The linear response method is employed to calculate the vibrational properties. Raman-active modes are in excellent agreement with the experimental data available up to 50 GPa,1 and we …

Analogous pyrite-type structures have been experimentally found at high pressure in SnO 2, RuO 2, PbO 2 [56] and GeO 2 [57]. Relative enthalpies of different phases are shown inFig. ...

The pyrite-type high-pressure form of FeOOH. Masayuki Nishi, Yasuhiro Kuwayama, Jun Tsuchiya & Taku Tsuchiya. Nature 547, 205–208 ( 2017) Cite this article. 16k Accesses. 121 Citations....

Request PDF | Sulfur isotope compositions of pyrite from high-pressure metamorphic rocks and related veins (SW Tianshan, China): Implications for the sulfur cycle in subduction zones | A detailed ...

The chemical reaction of group-14 elements with molecular nitrogen at pressures above 60 GPa successfully leads to the formation of pyrite-type pernitrides. These new crystalline group-14 elemental pernitrides were found to show a bulk modulus higher than the other known group-14 elemental nitrides. Our resu

To test the stability of high-pressure phases, we annealed the samples at ambient pressure with flowing nitrogen gas. A pyrite single phase of (Fe, Co, Ni, Cu)S 2 decomposed into pyrite-type phases and the NiAs-type phase after annealing at 400 °C. The phase of the sample prepared at high pressure was not stable at ambient pressure …

The high-pressure behavior of manganese diselenide MnSe2 was investigated by synchrotron angle-dispersive X-ray diffraction (ADXRD) and infrared reflection spectroscopy equipped with a diamond-anvil cell. It was found that MnSe2 with a pyrite-type structure undergoes a transformation into a disordered intermediate phase at …

In this paper, we report an in situ high-temperature X-ray diffraction study of phase transformations in pyrite under variable environmental conditions (atmospheric pressure (1 atm.), low air pressure (<0.001 atm.), inert and carbon dioxide atmosphere). We observe that while heating of pyrite in air promotes the formation of hematite (α-Fe 2 …

33 Citations. 14 Altmetric. Metrics. A drastically altered chemistry was recently discovered in the Fe-O-H system under deep …

Ultrasonic interferometry was utilized in conjunction with synchrotron-based X-ray diffraction and X-radiographic imaging to determine the compressional and shear wave velocities and unit-cell volumes of pyrite (FeS2) at room temperature and pressures up to 9.6 GPa. Fitting all of the experimental volume and velocity data to third-order finite …

The Pyrite-Type High-Pressure Form of Silica. Y. Kuwayama, K. Hirose, +1 author. Y. Ohishi. Published in Science 5 August 2005. Materials Science. TLDR. X-ray …

The pyrite-type high-pressure form of FeOOH. This work reports the formation of a new FeOOH phase with the pyrite-type framework of FeO6 octahedra, which is much denser than the surrounding mantle and is stable at the conditions of the base of the mantle. Expand.

X-ray diffraction measurements showed that a high-pressure form with a pyrite-type structure, denser than other known silica phases, is stable above 268 giga …

The resulting high pressure phase is notably also cubic, and most probably of the pyrite type. Compared with other transitions between isostructural phases, the AV/V=0.16 volume change is strikingly large. Representative examples of the observed EDS patterns for the low- and high-pressure pyrite type modifications of MnTe2 are …

Abstract. Silica (SiO 2) exhibits extensive polymorphism at elevated pressures. X-ray diffraction measurements showed that a high-pressure form with a pyrite-type structure, denser than other known silica phases, is stable above 268 giga-pascals and 1800 kelvin. The silicon coordination number increases from 6 in the α-PbO …