Oxide-Sulfide-Melt-Bubble Interactions in Spinel-Rich Taxitic Rocks of the Norilsk-Talnakh Intrusions, Polar Siberia

2020 ◽  
Vol 115 (6) ◽  
pp. 1305-1320
Author(s):  
Louise Schoneveld ◽  
Stephen J. Barnes ◽  
Belinda Godel ◽  
Margaux Le Vaillant ◽  
Marina A. Yudovskaya ◽  
...  
Keyword(s):  
Country Rock ◽  
Silicate Melt ◽  
Small Scale ◽  
Sulfide Liquid ◽  
Vapor Bubbles ◽  
X Ray ◽  
Bubble Interactions ◽  
Spherical Structures ◽  
Sulfide Melt

Abstract Oxide-rimmed, spherical structures interpreted as former gas bubbles have been discovered within a chromitiferous taxitic lithology of the Norilsk-Talnakh intrusions. These rocks are represented by variable grain size, presence of reworked country-rock xenoliths and millimeter- to centimeter-scale irregular spinel-rich aggregates, patches, or disrupted seams and stringers. They contain spherical and subspherical agglomerations that we interpret as amygdules, partially or completely filled with low-temperature hydrothermal minerals and locally with magmatic phases including sulfide globules. In places these amygdules form clusters that are interpreted as former bubble foams. The wetting relationships visible between vapor bubbles, silicate melt, sulfide liquid, and oxide were investigated in detail using 3-D μX-ray tomography and detailed 2-D X-ray fluorescence maps. They also reveal short-range spatial variability in silicate and oxide minerals, reflecting small-scale advanced fractionation of silicate melt. Three possible mechanisms are considered for the formation of these bubble-spinel foams: (1) the abundant spinel allows for the in situ nucleation of vapor bubbles, (2) the vapor bubbles ascend through the magma and collect spinel, or (3) the vapor bubbles cause rapid nucleation of chromite within these layers. Although none of these mechanisms can be exclusively ruled out, the texture and chemistry of the Norilsk-Talnakh chromitiferous taxitic lithology is most indicative of in situ nucleation of vapor bubbles on spinel surfaces (i.e., mechanism 1).

Evolution of texture and internal stresses within polycrystalline rock salt using in situ 3D synchrotron computed tomography and 3D X-ray diffraction

2021 ◽  
Vol 54 (5) ◽  
pp. 1379-1393
Author(s):  
Amirsalar Moslehy ◽  
Khalid A. Alshibli ◽  
Timothy J. Truster ◽  
Peter Kenesei ◽  
Wadi H. Imseeh ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Slip System ◽  
Rock Salt ◽  
Small Scale ◽  
Internal Stresses ◽  
X Ray Diffraction ◽  
Crack Network ◽  
X Ray ◽  
Fully Connected

Rock salt caverns have been extensively used as reliable repositories for hazardous waste such as nuclear waste, oil or compressed gases. Undisturbed rock salt deposits in nature are usually impermeable and have very low porosity. However, rock salt formations under excavation stresses can develop crack networks, which increase their porosities; and in the case of a connected crack network within the media, rock salt may become permeable. Although the relationship between the permeability of rock salt and the applied stresses has been reported in the literature, a microscopic study that investigates the properties influencing this relationship, such as the evolution of texture and internal stresses, has yet to be conducted. This study employs in situ 3D synchrotron micro-computed tomography and 3D X-ray diffraction (3DXRD) on two small-scale polycrystalline rock salt specimens to investigate the evolution of the texture and internal stresses within the specimens. The 3DXRD technique measures the 3D crystal structure and lattice strains within rock salt grains. The specimens were prepared under 1D compression conditions and have shown an initial {111} preferred texture, a dominant {110}〈110〉 slip system and no fully connected crack network. The {111} preferred texture under the unconfined compression experiment became stronger, while the {111}〈110〉 slip system became more prominent. The specimens did not have a fully connected crack network until applied axial stresses reached about 30 MPa, at a point where the impermeability of the material becomes compromised due to the development of multiple major cracks.

In situ X-ray experiment on the structure of hydrous Mg-silicate melt under high pressure and high temperature

2007 ◽  
Vol 34 (10) ◽  
Author(s):  
Akihiro Yamada ◽  
Toru Inoue ◽  
Satoru Urakawa ◽  
Ken-ichi Funakoshi ◽  
Nobumasa Funamori ◽  
...  
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Silicate Melt ◽  
X Ray

scholarly journals MgCO3 + SiO2 reaction at pressures to 32 GPa studied using in situ X-ray diffraction and synchrotron radiation

2019 ◽  
Vol 64 (9) ◽  
pp. 1003-1012
Author(s):  
K. D. Litasov ◽  
A. F. Shatskiy
Keyword(s):  
Synchrotron Radiation ◽  
Reaction Temperature ◽  
Eutectic Mixture ◽  
Silicate Melt ◽  
Stability Field ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
X Ray ◽  
Reaction Proceeds

The results of the experimental study of the decarbonation and melting reactions in the MgCO3–SiO2 system at pressures up to 32 GPa using multi-anvil technique, in situ X-ray diffraction and synchrotron radiation have been reported. At 3–7 GPa and 1400–1700 K, the reaction proceeds with the release of carbon dioxide and the formation of enstatite. At 9–13 GPa and 1850–1930 K, clinoenstatite, carbonate-silicate melt, and CO2 were found among the reaction products. At 16 GPa and 1825 K, the reaction is accompanied by the formation of wadsleyite and at higher temperature by the formation of a carbonated melt, with a Mg/Si ratio close to wadsleyite, stishovite and CO2 fluid. At this pressure, which coincides with the wadsleyite-stishovite assemblage stability field in the MgSiO3 phase diagram, a decrease in the reaction temperature by about 100 K is observed. At higher pressures, the reaction proceeds with the formation of the MgSiO3 (akimotoite or bridgmanite) + melt assemblage. The reaction temperature at 25–35 GPa does not change and is about 2000 K. With a further increase in temperature to 2100 K, bridgmanite melts incongruently, reacting with a carbonate-silicate melt to form stishovite. The composition of the eutectic mixture shifts towards MgCO3 with increasing pressure. The studied reaction marks the upper temperature limit of the stability of magnesite and the free phase of SiO2 in the Earth’s mantle and generally coincides with the mantle adiabat at depths of 300–900 km.

Mapping REE distribution in scheelite using luminescence

2000 ◽  
Vol 64 (5) ◽  
pp. 891-903 ◽  
Author(s):  
J. Brugger ◽  
A. A. Bettiol ◽  
S. Costa ◽  
Y. Lahaye ◽  
R. Bateman ◽  
...  
Keyword(s):  
Oscillatory Zoning ◽  
Small Scale ◽  
Nuclear Microprobe ◽  
Inhomogeneous Distribution ◽  
Isotopic Data ◽  
X Ray ◽  
Fundamental Information ◽  
Icp Ms ◽  
Ree Distribution

AbstractIn situ laser ablation high resolution ICP-MS analyses of scheelite from hydrothermal veins at the Archaean Mt. Charlotte gold deposit (Western Australia) show inhomogeneous REE distribution at small scale (<100 μm). In a limited number of samples, variations of the cathodoluminescence (CL) colours from blue to yellow are linked to the REE content of scheelite, and reveal oscillatory zoning of the REE with zone widths between 1 μm and 100 μm. However, CL failed to reveal the zoning in most inhomogeneous scheelite samples. A nuclear microprobe has been used to characterize the distribution of REE in these samples. No reasonable map for the distribution of REE could be obtained by particle induced X-ray emission, because of interferences with W-L lines. However, monochromatic ionoluminescence (IL) maps collected at the wavelength of the main REE3+ luminescence peaks revealed oscillatory zoning. Therefore, IL is a powerful tool for mapping the distribution of REE in natural scheelite. Monochromatic IL maps allow us to determine the nature of the inhomogeneous distribution of REE in scheelite, fundamental information for using the REE in this mineral as a marker for the chemistry of ore-forming fluids, and for interpreting Sm-Nd isotopic data.

Spatial Association Between Platinum Minerals and Magmatic Sulfides Imaged with the Maia Mapper and Implications for the Origin of the Chromite-Sulfide-PGE Association

2021 ◽  
Author(s):  
Stephen J. Barnes ◽  
Chris Ryan ◽  
Gareth Moorhead ◽  
Rais Latypov ◽  
Wolfgang D. Maier ◽  
...  
Keyword(s):  
Close Association ◽  
Spatial Association ◽  
Ore Deposits ◽  
Sulfide Liquid ◽  
X Ray ◽  
Magmatic Sulfides ◽  
Array Technology ◽  
Magmatic Sulfide ◽  
Textural Relationship

ABSTRACT The spatial association between Pt minerals, magmatic sulfides, and chromite has been investigated using microbeam X-ray fluorescence (XRF) element mapping and the Maia Mapper. This lab-based instrument combines the Maia parallel energy dispersive (ESD) detector array technology with a focused X-ray beam generated from a liquid metal source. It proves to be a powerful technique for imaging Pt distribution at low-ppm levels on minimally prepared cut rock surfaces over areas of tens to hundreds of square centimeters, an ideal scale for investigating these relationships. Images of a selection of samples from the Bushveld Complex and from the Norilsk-Talnakh ore deposits (Siberia) show strikingly close association of Pt hotspots, equated with the presence of Pt-rich mineral grains, with magmatic sulfide blebs in all cases, except for a taxitic low-S ore sample from Norilsk. In all of the Bushveld samples, at least 75% of Pt hotspots (by number) occur at or within a few hundred microns of the outer edges of sulfide blebs. In samples from the leader seams of the UG2 chromitite, sulfides and platinum hotspots are also very closely associated with the chromite seams and are almost completely absent from the intervening pyroxenite. In the Merensky Reef, the area ratio of Pt hotspots to sulfides is markedly higher in the chromite stringers than in the silicate-dominated lithologies over a few centimeters either side. We take these observations as confirmation that sulfide liquid is indeed the prime collector for Pt and, by inference, for the other platinum group elements (PGEs) in all these settings. We further propose a mechanism for the sulfide-PGE-chromite association in terms of in situ heterogeneous nucleation of all these phases coupled with transient sulfide saturation during chromite growth and subsequent sulfide loss by partial re-dissolution. In the case of the amygdular Norilsk taxite, the textural relationship and high PGE/S ratio is explained by extensive loss of S to an escaping aqueous vapor phase.

Polymer crystallization studies under processing-relevant conditions at the SAXS/WAXS DUBBLE beamline at the ESRF

2013 ◽  
Vol 46 (6) ◽  
pp. 1681-1689 ◽  
Author(s):  
Giuseppe Portale ◽  
Dario Cavallo ◽  
Giovanni Carlo Alfonso ◽  
Daniel Hermida-Merino ◽  
Martin van Drongelen ◽  
...  
Keyword(s):  
Blow Up ◽  
Simultaneous Thermal Analysis ◽  
Nucleating Agent ◽  
Polymer Crystallization ◽  
Time Frame ◽  
Small Scale ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Recent developments on the experimental infrastructure and the acquisition of new detectors on the Dutch–Belgian beamline BM26B at the ESRF offer novel and promising possibilities for synchrotron X-ray experiments in the field of polymer crystallization under processing-relevant conditions. In this contribution, some of the most recent experiments mimicking conditions similar to those relevant for the plastics processing industry are discussed. Simultaneous thermal analysis and wide-angle X-ray scattering (WAXS) experiments, at the millisecond time-frame level, on β-nucleated isotactic polypropylene (i-PP) samples subjected to ballistic cooling up to 230 K s−1, show that the efficiency of the nucleating agent can be suppressed when quenched cooling rates higher than 130 K s−1are used.In situWAXS experiments using small-scale industrial equipment during a real film blowing process reveal the dependence of the onset of crystallinity (the so-called freeze line) and the crystal orientation as a function of different take-up and blow-up ratios.In situsmall-angle X-ray scattering (SAXS) experiments during high-flow fields reveal the formation of shish and kebab structures in i-PP as a function of the imposed stress. Quantitative analysis of i-PP flow-induced structures is presented. The beamline specifications required to obtain high quality and industrially relevant results are also briefly reported.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

In Situ X-Ray Absorption Studies of the Electrochemical Reduction of Hydroxocobalamin

1997 ◽  
Vol 7 (C2) ◽  
pp. C2-619-C2-620 ◽  
Author(s):  
M. Giorgett ◽  
I. Ascone ◽  
M. Berrettoni ◽  
S. Zamponi ◽  
R. Marassi
Keyword(s):  
Electrochemical Reduction ◽  
X Ray ◽  
Absorption Studies ◽  
X Ray Absorption
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