Journal articles on the topic 'Olivine and pyroxene thermodynamics'
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1
Matas, J., Y. Ricard, L. Lemelle, and F. Guyot. "An improved thermodynamic model of metal-olivine-pyroxene stability domains." Contributions to Mineralogy and Petrology 140, no. 1 (November 2000): 73–83. http://dx.doi.org/10.1007/s004100000177.
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Abdeyazdan, Hamed, Maksym Shevchenko, Peter C. Hayes, and Evgueni Jak. "Integrated Experimental and Thermodynamic Modeling Investigation of Phase Equilibria in the PbO–MgO–SiO2 System in Air." Metallurgical and Materials Transactions B 53, no. 2 (February 8, 2022): 954–67. http://dx.doi.org/10.1007/s11663-022-02440-6.
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AbstractMagnesium oxide-based refractory materials are used industrially to contain the chemically aggressive slags present in lead smelting systems. In the present study an integrated experimental and thermodynamic modeling approach was taken to provide fundamental information on the chemical reactions taking place in these systems. New experimental phase equilibria and liquidus data were obtained for the PbO–MgO–SiO2 system in air in the temperature range 750 °C to 1740 °C. In the MgO–SiO2 binary, new experimental results were obtained at 1550 °C to 1740 °C and compared to the available thermodynamic data in the literature. The experiments were carried out using the high-temperature equilibration of oxide powder mixtures followed by rapid quenching of the samples. Electron probe X-ray microanalysis (EPMA) was used to determine the compositions of the solid and liquid phases present at equilibrium conditions. Phase equilibria and liquidus isotherms in the cristobalite and tridymite (SiO2), pyroxene (protoenstatite MgSiO3), olivine (forsterite Mg2SiO4), barysilite (Pb8MgSi6O21), massicot (PbO) and periclase (MgO) primary phase fields were measured, and the extent of the high-silica two-liquid immiscibility gap in equilibrium with cristobalite was determined. The experimental results were used to optimize the parameters in a thermodynamic database that was subsequently used to describe this multi-component, multi-phase system and predict the liquidus for the PbO–MgO–SiO2 system. The new data were used to characterize the chemical interactions of magnesia-based refractory with PbO–MgO–SiO2 slags.
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Komatsu, Mutsumi, Timothy J. Fagan, Alexander N. Krot, Kazuhide Nagashima, Michail I. Petaev, Makoto Kimura, and Akira Yamaguchi. "First evidence for silica condensation within the solar protoplanetary disk." Proceedings of the National Academy of Sciences 115, no. 29 (July 2, 2018): 7497–502. http://dx.doi.org/10.1073/pnas.1722265115.
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Calcium-aluminum–rich inclusions (CAIs) and amoeboid olivine aggregates (AOAs), a refractory component of chondritic meteorites, formed in a high-temperature region of the protoplanetary disk characterized by approximately solar chemical and oxygen isotopic (Δ17O ∼ −24‰) compositions, most likely near the protosun. Here we describe a 16O-rich (Δ17O ∼ −22 ± 2‰) AOA from the carbonaceous Renazzo-type (CR) chondrite Yamato-793261 containing both (i) an ultrarefractory CAI and (ii) forsterite, low-Ca pyroxene, and silica, indicating formation by gas–solid reactions over a wide temperature range from ∼1,800 to ∼1,150 K. This AOA provides direct evidence for gas–solid condensation of silica in a CAI/AOA-forming region. In a gas of solar composition, the Mg/Si ratio exceeds 1, and, therefore, silica is not predicted to condense under equilibrium conditions, suggesting that the AOA formed in a parcel of gas with fractionated Mg/Si ratio, most likely due to condensation of forsterite grains. Thermodynamic modeling suggests that silica formed by condensation of nebular gas depleted by ∼10× in H and He that cooled at 50 K/hour at total pressure of 10−4 bar. Condensation of silica from a hot, chemically fractionated gas could explain the origin of silica identified from infrared spectroscopy of remote protostellar disks.
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Murphy, William M., and Harold C. Helgeson. "Thermodynamic and kinetic constraints on reaction rates among minerals and aqueous solutions. III. Activated complexes and the pH-dependence of the rates of feldspar, pyroxene, wollastonite, and olivine hydrolysis." Geochimica et Cosmochimica Acta 51, no. 12 (December 1987): 3137–53. http://dx.doi.org/10.1016/0016-7037(87)90124-4.
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Murphy, W. M., and H. C. Helgeson. "Thermodynamic and kinetic constraints on reaction rates among minerals and aqueous solutions; IV, Retrieval of rate constants and activation parameters for the hydrolysis of pyroxene, wollastonite, olivine, andalusite, quartz, and nepheline." American Journal of Science 289, no. 1 (January 1, 1989): 17–101. http://dx.doi.org/10.2475/ajs.289.1.17.
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Huang, Ruifang, Xing Ding, Weidong Sun, and Xiuqi Shang. "Contrasted Effect of Spinel and Pyroxene on Molecular Hydrogen (H2) Production during Serpentinization of Olivine." Minerals 11, no. 8 (July 22, 2021): 794. http://dx.doi.org/10.3390/min11080794.
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Serpentinization produces molecular hydrogen (H2) and hydrocarbons that can feed the colonies of microbes in hydrothermal vent fields, and therefore serpentinization may be important for the origins of life. However, the mechanisms that control molecular hydrogen (H2) production during serpentinization remain poorly understood. Here the effect of pyroxene minerals and spinel on molecular hydrogen (H2) generation during serpentinization is experimentally studied at 311–500 °C and 3.0 kbar, where olivine, individually and in combinations with pyroxene and/or spinel, is reacted with saline solutions (0.5 M NaCl). The results show a contrasting influence of spinel and pyroxeneon molecular hydrogen (H2) production. At 311 °C and 3.0 kbar, spinel promotes H2 generation by around two times, and pyroxene minerals decrease molecular hydrogen (H2) production by around one order of magnitude. Spinel leaches aluminum (Al) and chromium (Cr) during hydrothermal alteration, and Al and Cr enhance molecular hydrogen (H2) production. This is confirmed by performing experiments on the serpentinization of olivine with the addition of Al2O3 or Cr2O3 powders, and an increase in molecular hydrogen (H2) production was observed. Pyroxene minerals, however, not only leach Al and Cr, but they also release silica (SiO2) during serpentinization. The sharp decline in molecular hydrogen (H2) production in experiments with a combination of olivine and pyroxene minerals may be attributed to releases of silica from pyroxene minerals. With increasing temperatures (e.g., 400–500 °C), the effect of spinel and pyroxene minerals on molecular hydrogen (H2) production is much less significant, which is possibly related tothe sluggish kinetics of olivine serpentinization under these T-P conditions. In natural geological settings, olivine is commonly associated with spinel and pyroxene, and molecular hydrogen (H2) during serpentinization can be greatly affected.
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Radomsky, Patrick M., and Roger H. Hewins. "Formation conditions of pyroxene-olivine and magnesian olivine chondrules." Geochimica et Cosmochimica Acta 54, no. 12 (December 1990): 3475–90. http://dx.doi.org/10.1016/0016-7037(90)90299-z.
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Bradley, J. P. "Physical and Mineralogical Properties of Anhydrous Interplanetary Dust Particles in the Analytical Electron Microscope." International Astronomical Union Colloquium 126 (1991): 63–70. http://dx.doi.org/10.1017/s0252921100066495.
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AbstractThe fine grained mineralogy and petrography of anhydrous “pyroxene” and “olivine” classes of chondritic interplanetary dust have been investigated by numerous electron microscopic studies. The “pyroxene” interplanetary dust particles (IDPs) are porous, unequilibrated assemblages of mineral grains, metal, glass, and carbonaceous material. They contain enstatite whiskers, FeNi carbides, and high-Mn olivines and pyroxenes, all of which are likely to be well preserved products of nebular gas reactions. Solar flare tracks are prominent in most “pyroxene” IDPs, indicating that they were not strongly heated during atmospheric entry. The “olivine” IDPs are coarse grained, equilibrated mineral assemblages that have probably experienced strong heating. Since most “olivine” IDPs do not contain tracks, it is possible that this heating occurred during atmospheric entry.
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Morse, S. A., Brent E. Owens, and Alan R. Butcher. "Origin of finger structures in the Rhum Complex: phase equilibrium and heat effects." Geological Magazine 124, no. 3 (May 1987): 205–10. http://dx.doi.org/10.1017/s0016756800016241.
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AbstractThe finger structures described earlier by Brown and later by Butcher, Young & Faithfull involve dissolution of troctolite during crystallization of olivine, followed by crystallization of pyroxene around olivine grains in the fingers. However, the ingestion of troctolite takes the liquid away from pyroxene saturation rather than toward it. The pyroxene field can be encountered metastably, and pyroxene caused to crystallize, by supercooling the olivine-rich liquid against the troctolite. The melt corrosion represented by the fingers, and other field relations, suggest that the mafic layers were emplaced as sills of mafic magma into nearly solid troctolites. Melting at the base of mafic liquid layers was impeded by a bed of olivine crystals releasing light solute upward, causing compositional convention and rapid heat transfer to the top of the layer, where melting demonstrably occurred. Recognition of this process introduces the novel concept of a magmatic heat pump driven by compositional convection. The crystallization path ol–px–pl(–sp) is also found next to xenoliths in the Kiglapait Intrusion where the magma was normally saturated only in ol+pl, directly demonstrating the effect of supercooling on the crystallization sequence.
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Kretz, Ralph, Peter Jones, and Ron Hartree. "Grenville metagabbro complexes of the Otter Lake area, Quebec." Canadian Journal of Earth Sciences 26, no. 2 (February 1, 1989): 215–30. http://dx.doi.org/10.1139/e89-018.
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Metagabbro complexes in a portion of the Grenville Province lying northwest of Ottawa occur as sheets, cylinders, and irregular bodies within a medium- to high-grade marble–gneiss–amphibolite terrane. The largest bodies (0.5–10 km in greatest dimension) consist principally of felsic metagabbro, mafic metagabbro, and minor metapyroxenite. Major-element and select trace-element analyses show that different complexes contain distinctly different amounts of K and other elements resulting in different interelement trends.Microstructure and microprobe mineral analyses provide evidence that the following metamorphic changes have occurred: (i) recrystallization of Ca pyroxene, orthopyroxene, and plagioclase; (ii) reaction of Mg-rich olivine with plagioclase to produce reaction zones consisting of orthopyroxene and a hornblende–spinel intergrowth; (iii) reaction of Mg–Fe olivine with plagioclase to produce garnet and hornblende; (iv) production of anthophyllite and hornblende from orthopyroxene and plagioclase; (v) production of hornblende (locally as rims about Ca pyroxene) from Ca pyroxene and plagioclase; (vi) crystallization of biotite, possibly by reaction between orthopyroxene and K-feldspar; and (vii) crystallization of small inclusions of spinel and ilmenite in Ca pyroxene and of spinel and biotite in plagioclase.With regard to the reaction olivine + plagioclase = orthopyroxene + hornblende + spinel, the anorthite and locally the forsterite components were extracted preferentially from plagioclase and olivine; K and Ti (for hornblende) and Zn (for spinel) were evidently obtained from the surrounding minerals; and H, F, and Cl (for hornblende) were obtained from beyond the gabbro bobies. Locally the reaction occurred within large crystals of Ca pyroxene where embedded olivine and plagioclase crystals were in contact.The production of hornblende rims about Ca pyroxene evidently involved plagioclase as a reactant, but the rims formed regardless of the contacting minerals. For example, rims were locally produced where Ca-pyroxene crystals were embedded in large crystals of orthopyroxene.Application of five geothermometers to crystals of both igneous and metamorphic origin yield temperatures of about 700 °C, similar to temperatures recorded for the enclosing marble and gneiss.
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Wieser, Penny, Maurizio Petrelli, Jordan Lubbers, Eric Wieser, Sinan Ozaydin, Adam Kent, and Christy Till. "Thermobar: An open-source Python3 tool for thermobarometry and hygrometry." Volcanica 5, no. 2 (November 9, 2022): 349–84. http://dx.doi.org/10.30909/vol.05.02.349384.
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We present Thermobar, a new open-source Python3 package for calculating pressures, temperatures, and melt compositions from mineral and mineral-melt equilibrium. Thermobar allows users to perform calculations with >100 popular parametrizations involving liquid, olivine-liquid, olivine-spinel, pyroxene only, pyroxene-liquid, two pyroxene, feldspar-liquid, two feldspar, amphibole only, amphibole-liquid, and garnet equilibria. Thermobar is the first open-source tool which can match up all possible pairs of phases from a given region, and apply various equilibrium tests to identify pairs from which to calculate pressures and temperatures (e.g. pyroxene-liquid, two pyroxene, feldspar-liquid, two feldspar, amphibole-liquid). Thermobar also contains functions allowing users to propagate analytical errors using Monte-Carlo methods, convert pressures to depths using different crustal density profiles, plot mineral classification and mineral-melt equilibrium diagrams, calculate liquid viscosities, and convert between oxygen fugacity values, buffer positions and Fe speciation in a silicate melt. Thermobar can be downloaded using pip and extensive documentation is available at https://thermobar.readthedocs.io/.
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Chang, Rui, Wei Yang, Honglei Lin, Rui Xu, Sheng Gou, Rong Wang, and Yangting Lin. "Lunar Terrestrial Analog Experiment on the Spectral Interpretations of Rocks Observed by the Yutu-2 Rover." Remote Sensing 14, no. 10 (May 11, 2022): 2323. http://dx.doi.org/10.3390/rs14102323.
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A visible and near-infrared imaging spectrometer (VNIS) loaded by the Chang’e-4 rover is the primary method for detecting the mineral composition of the lunar surface in the landing region. However, different data processing methods yield inconsistent mineral modes in measured lunar soil and rocks. To better constrain the mineral modes of the soil and rocks measured by Chang’e-4 VNIS, a noritic-gabbroic rock with a mineral composition similar to that of the lunar highland rocks is measured by scanning electron microscopy (SEM), the spare flight model of Chang’e-4 VNIS and TerraSpec-4 of ASD. Backscattered electron and energy dispersive spectrometry show that olivine, pyroxene, and plagioclase modal mineral abundances are 12.9, 35.0, and 52.2%, respectively. The estimated results of the spectrum by the Hapke radiative transfer model are 7.5, 39.3, and 53.2% for olivine, pyroxene, and plagioclase, respectively, which is consistent with to those of SEM mapping within error. In contrast, the estimated results of the modified Gaussian model are 29 and 71% for olivine and pyroxene, respectively, indicating the absence of plagioclase. Based on our implemented Hapke model, we decode the data of the two rocks detected by the rover on the 3rd and 26th lunar days of mission operations. The obtained results suggest that both rocks are norite or gabbro with noticeable differences. The first rock, with more olivine and pyroxene, may have been excavated from the Finsen crater. The second rock, with more plagioclase, may have been ejected from the southwestern edge of the Von Kármán crater, indicating the initial lunar crust.
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Ejima, T., M. Akasaka, T. Nagao, and H. Ohfuji. "Occurrence of Fe3+ and formation process of precipitates within oxidized olivine phenocrysts in basalt lava from Kuroshima volcano, Goto islands, Nagasaki, Japan." Mineralogical Magazine 79, no. 7 (December 2015): 1833–48. http://dx.doi.org/10.1180/minmag.2015.079.7.08.
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AbstractThe oxidation state of Fe and precipitates within olivine phenocrysts from an olivine-basalt from Kuroshima volcano, Goto Islands, Nagasaki Prefecture, Japan, were determined using electron microprobe analysis, 57Fe Mössbauer spectroscopy, Raman spectroscopy and transmission electron microscopy, to examine the formation process of the Fe-bearing precipitates.The average Fo content of the olivine phenocrysts is 76.2 mol.%. The olivine phenocrysts occasionally have precipitate minerals at their rims, especially on rims near vesicles. The 57Fe Mössbauer spectrum of olivine separates consists of two doublets assigned to Fe2+ at the octahedral M1 and M2 sites, and a Fe3+ doublet at the M1 and M2 sites. The Fe2+:Fe3+ ratio is 90(5):10(1). The precipitates at the rims of the olivine phenocrysts consistof magnetite and enstatite showing coaxial relations with host olivine, and grow parallel to the olivine c axis. Moreover, clusters consisting of nanoscale domains of a few tens of nm in size occur in the host olivine. Their rounded form and appearance in transmission electron microscope images are similar to those of the magnetite precipitates, but they have an olivine structure and can be regarded as embryos of magnetite within the olivine.The oxidation process of olivine phenocrysts under cooling conditions is: (1) formation of magnetite embryos on the rims of olivinephenocrysts; (2) formation of enstatite-like pyroxene domains by depletion of Fe in olivine due to the generation of magnetite embryos; (3) crystallization of magnetite and enstatite-like pyroxene precipitates.
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Boudreau, Alan E. "The Stillwater Complex, Montana – Overview and the significance of volatiles." Mineralogical Magazine 80, no. 4 (June 2016): 585–637. http://dx.doi.org/10.1180/minmag.2016.080.063.
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AbstractThe geology of the 2.7 Ga Stillwater Complex in South-Central Montana is reviewed with a focus on the role of volatiles in locally modifying both the crystallization sequence of the evolving parent magma and the initially precipitated solid assemblages to favour olivine ± chromite. A secondary origin for these two minerals is particularly probable for the olivine-bearing rocks of the Banded series and, at a minimum, also increasing their modal abundance in the Peridotite zone of the Ultramafic series. Direct evidence for volatiles includes the presence of high-temperature fluid inclusions in pegmatoids and hydrous melt inclusions (now crystallized) in chromite and olivine from both the Ultramafic and the Banded series rocks. Indirect evidence includes the boninitic character of the parent magma, the presence of volatile-bearing minerals including high-temperature carbonates, rock textures, and Cl / F variations in apatite. Mechanisms which favour the formation of olivine (± chromite) over pyroxene include volatile phase boundary shifts induced by added H2O, incongruent melting of pyroxene by hydration of a partly-molten mush, and the near- to sub-solidus replacement of pyroxene by olivine and chromite by silica-undersaturated fluids. These mechanisms cast doubt that magmas with different liquid lines of descent were involved in the crystallization of the Stillwater Complex. A dry Stillwater magma would have been mineralogically and modally much less varied and lacking in high-grade platinum-group element and chromium deposits.
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Farahi, Farzaneh, Saeed Taki, and Mojgan Salavati. "Mineral chemistry and geothermobarometry of gabbroic rocks from the Gysel area, Alborz mountains, north Iran." Nexo Revista Científica 33, no. 02 (December 31, 2020): 392–408. http://dx.doi.org/10.5377/nexo.v33i02.10779.
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The gabbroic rocks in the Gysel area of the Central Alborz Mountains in north Iran are intruded into the Eocene Volcano-sedimentary units. The main gabbroic rocks varieties include gabbro porphyry, olivine gabbro, olivine dolerite and olivine monzo-gabbro. The main minerals phases in the rocks are plagioclase and pyroxene and the chief textures are sub-hedral granular, trachytoidic, porphyritic, intergranular and poikilitic. Electron microprobe analyses on minerals in the rock samples shows that plagioclase composition ranges from labradorite to bytonite, with oscillatory and normal chemical zonings. Clinopyroxene is augite and orthopyroxene is hypersthene to ferro-hypersthene. Thermometry calculations indicate temperatures of 650˚C to 750˚C for plagioclase crystallization and 950˚C to 1130˚C for pyroxene crystallization. Clinopyroxene chemistry reveals sub-alkaline and calc-alkaline nature for the parental magma emplaced in a volcanic arc setting.
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Jamieson, H. E., P. L. Roeder, and A. H. Grant. "Olivine-Pyroxene-PtFe Alloy as an Oxygen Geobarometer." Journal of Geology 100, no. 1 (January 1992): 138–45. http://dx.doi.org/10.1086/629577.
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Stolz, A. J. "Fluid activity in the lower crust and upper mantle: mineralogical evidence bearing on the origin of amphibole and scapolite in ultramafic and mafic granulite xenoliths." Mineralogical Magazine 51, no. 363 (December 1987): 719–32. http://dx.doi.org/10.1180/minmag.1987.051.363.13.
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AbstractXenoliths in an olivine nephelinite from the McBride Province, North Queensland, include Cr-diopside lherzolites, spinel and garnet websterites, felsic, 2-pyroxene and garnet granulites, and hornblendites. The spinel and garnet websterites are interpreted as crystal segregations from olivine basalt or alkali olivine basalt magma at ∼ 12 kbar followed by isobaric cooling (to approximately 900–1000°C) and subsolidus reequilibration. Garnet and 2-pyroxene granulites are mineralogically and texturally distinct and are considered to represent relatively large degrees of crystallization of basaltic magmas at comparable or slightly lower pressures (8–12 kbar). Mafic and ultramafic xenoliths have been modified to varying degrees following the relatively recent influx of a H2O- and CO2-bearing fluid. Variable amounts of amphibole and mica developed in response to the introduced fluid and it is argued that some hornblendites are the end-products of this process acting on spinel websterites. Felsic and 2-pyroxene granulite xenoliths display only minor evidence of increased PH2O. Mineralogical and textural evidence indicates high-sulphur Ca-rich scapolite in several garnet granulites did not form in response to the increased fluid activities. It is proposed the scapolite was a primary cumulate phase precipitated from alkali basaltic magma under elevated fo2 and fso2 conditions.
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Imamverdiyev, Nazim A., Minakhanym Y. Gasanguliyeva, Vagif M. Kerimov, and Ulker I. Kerimli. "Petrogeochemical features of the Neogene collision volcanism of the Lesser Caucasus (Azerbaijan)." Journal of Geology, Geography and Geoecology 29, no. 2 (July 8, 2020): 289–303. http://dx.doi.org/10.15421/112027.
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The article is devoted to the petrogeochemical features of Neogene collision volcanism in the central part of the Lesser Caucasus within Azerbaijan. The main goal of the study is to determine the thermodynamic conditions for the formation of Neogene volcanism in the central part of the Lesser Caucasus using the available petrogeochemical material. Using factor analysis, as well as the “IGPET”, “MINPET”, “Petrolog-3” programs, material balance calculations were performed that simulate the phenocryst fractionation process, the crystallization temperature, pressure, and figurative nature of the rock-forming minerals of the formation rocks were calculated. It was determined that at the early and middle stages of crystallization of the rocks of the andesite-dacite-rhyolite formation, the fractionation of amphibole played an important role in the formation of subsequent differentiates. Based on computer simulation, it was revealed that rocks of the andesite-dacite-rhyolite formation were formed by fractional crystallization of the initial high-alumina basaltic magma of high alkalinity in the intermediate magma foci. The calculations of the balance of the substance, simulating the process of fractionation of phenocrysts, as well as magnetite, confirmed the possibility of obtaining rock compositions from andesites to rhyolites as a result of this process. In this case, the process of crystallization differentiation was accompanied by processes of contamination, hybridism and mixing. Based on the geochemical features of rare and rare-earth elements, changes in their ratios, the nature of the mantle source and the type of fractionation process are determined. It was revealed that the enrichment of formation rocks by light rare earths, as well as by many incoherent elements, is associated with the evolution of enriched mantle material. Under high water pressure, as a result of the fractionation of olivine and pyroxene, high-alumina basalts are formed from primary high-magnesian magma, which can be considered parental magma. It was established that, in contrast to the elevated Transcaucasian zone in the more lowered East Caucasus, under conditions of increased fluid pressure and reduced temperature, the melt underwent fractional crystallization in the intermediate centers, being enriched with alkaline, large-ion lithophilic elements, light REEs, etc. This is evidenced by the presence of large crystals of feldspars, the contamination of these minerals by numerous crystals of biotite, magnetite, several generations of these minerals, zonality, as well as the presence of related “water” inclusions, such as hornblendites, hornblende gabbro, etc. The physicochemical conditions for the formation of Neogene volcanic rocks of the Lesser Caucasus are determined.
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Yin, Feng, and Deqiu Dai. "Petrology and mineralogy of the Viñales meteorite, the latest fall in Cuba." Science Progress 104, no. 2 (April 2021): 003685042110198. http://dx.doi.org/10.1177/00368504211019859.
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The new Cuban chondrite, Viñales, fell on February first, 2019 at Pinar del Rio, northwest of Cuba (22°37′10″N, 83°44′34″W). A total of about 50–100 kg of the meteorite were collected and the masses of individual samples are in a range 2–1100 g. Two polished thin sections were studied by optical microscope, Raman spectroscopy and electron microprobe analysis in this study. The meteorite mainly consists of olivine (Fa24.6), low-Ca pyroxene (Fs20.5), and troilite and Fe-Ni metal, with minor amounts of feldspar (Ab82.4-84.7). Three poorly metamorphosed porphyritic olivine-pyroxene and barred olivine chondrules are observed. The homogeneous chemical compositions and petrographic textures indicate that Viñales is a L6 chondrite. The Viñales has fresh black fusion crust with layered structure, indicating it experienced a high temperature of ∼1650°C during atmospheric entry. Black shock melt veins with width of 100–600 μm are pervasive in the Viñales and olivine, bronzite, and metal phases are dominate minerals of the shock melt vein. The shock features of major silicate minerals suggest a shock stage S3, partly S4, and the shock pressure could be >10 GPa.
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Greenfield, A. M. R., E. D. Ghent, and J. K. Russell. "Geothermobarometry of spinel peridotites from southern British Columbia: implications for the thermal conditions in the upper mantle." Canadian Journal of Earth Sciences 50, no. 10 (October 2013): 1019–32. http://dx.doi.org/10.1139/cjes-2013-0037.
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Spinel lherzolite xenoliths within alkali basalts exposed at Rayfield River and Big Timothy Mountain, south-central British Columbia, represent samples of the underlying lithospheric mantle. Electron microprobe analysis shows that most xenoliths comprise compositionally homogeneous grains of olivine, orthopyroxene, clinopyroxene, and spinel. We applied the following mineral-pair geothermometers to these rocks: orthopyroxene–clinopyroxene, spinel–orthopyroxene, and spinel–olivine. Temperatures calculated using the Brey and Köhler calibration of two-pyroxene thermometry were constrained in pressure by being required to lie on a model geotherm we develop for this region of B.C. The model geotherm is constrained to produce a temperature at the Moho (33 km) of 825 ± 25 °C to match the lowest temperature peridotite xenoliths recovered in this study. Although the overall effect of pressure on the temperature calculations is negligible (∼2 °C for 0.1 GPa), the simultaneous solution of the model geotherm and the pressure-dependent Brey–Köhler two-pyroxene thermometry removes the need for adopting an arbitrary pressure. We take these temperatures to represent peak mantle lithosphere temperatures. Fourteen Rayfield River xenoliths return two-pyroxene temperatures between 841 and 962 °C corresponding to depths of 34–42 km. Orthopyroxene–spinel and olivine–spinel results are 889 ± 60 and 825 ± 88 °C, respectively. Five Big Timothy xenoliths have two-pyroxene temperatures spanning 840–1058 °C and corresponding to depths of 34–48 km. Mean orthopyroxene–spinel and olivine–spinel temperatures are 844 ± 63 and 896 ± 232 °C, respectively. We argue that the differences in ranges of temperature do not represent closure temperatures imposed during cooling either in the mantle or during transport by the magma. Rather, these differences reflect differences in the original calibrations of the geothermometers or different degrees of equilibration in exchange reactions in dry rocks. Isochemical phase diagrams (pseudosections) constrain the pressure–temperature (P–T) field in which spinel is stable. These diagrams suggest that the spinel-bearing peridotites equilibrated at pressures ranging from ∼9.6 to 14 kbar (10 kbar = 1 GPa).
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Bui, Ngoc Kim, Hieu Trung Pham, Minh Pham, and Phuc Duc Le. "Mineral characteristics of metacarbonat in Sa Thay, Kon Tum and potential use for gemstone." Science and Technology Development Journal - Natural Sciences 5, no. 2 (March 14, 2021): first. http://dx.doi.org/10.32508/stdjns.v5i2.962.
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Metacarbonates located in Sa Thay, Kon Tum massif are distributed in ultramafic marble assemblage from Kham Duc (NP-e1kđ) complex.The main rock-formingminerals arecalcite and dolomite (40÷85%), olivine (5÷20%), pyroxene (5÷15%), and serpentine (5÷25%). Accessory minerals aretalc and epidote. Chemical composition of pyroxene in metacarbonate was determined by EPMA method: the composition of pyroxene is diopsite (Wo49.5 En50.1Fs0.4 to Wo50.8En48.9Fs0.2). The rim of pyroxene grains generally have higher wollastonite than core(49.9÷50.8%).Metacarbonates originated from metamorphic sources with three main stages: regional metamorphism, superimposed metamorphismand hydrothermal metamorphism stages. With each stage, they have different color characteristicsto create a variety of color. Metacarbonateshave quality characteristicsofcolor, durability, pattern, diversity, and low radioactivity. These make the metacarbonates suitable for gemstone applications.
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Mustard, J. F. "Olivine and Pyroxene Diversity in the Crust of Mars." Science 307, no. 5715 (March 11, 2005): 1594–97. http://dx.doi.org/10.1126/science.1109098.
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LI, Chan, XiaoPo ZHENG, FuJiang LIU, Ying ZHANG, DengChao LI, and Le QIAO. "Lunar pyroxene and olivine abundance analysis of Sinus Iridum." SCIENTIA SINICA Physica, Mechanica & Astronomica 43, no. 11 (October 1, 2013): 1387–94. http://dx.doi.org/10.1360/132013-294.
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Thompson, Stephen P., Anna Herlihy, Claire A. Murray, Annabelle R. Baker, and Sarah J. Day. "Crystallisation of amorphous Mg-Fe silicates produced from microwave-dried sol-gels." Proceedings of the International Astronomical Union 15, S350 (April 2019): 408–9. http://dx.doi.org/10.1017/s1743921319009360.
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AbstractAmorphous Mg-Fe silicates are produced from microwave-dried sol-gels and their thermal crystallisation is studied via in situ synchrotron X-ray powder diffraction. Mg-pyroxene crystallised to forsterite, enstatite and cristobalite. The inclusion of 10% Fe formed only forsterite at much higher temperature, while pure Mg-olivine crystallised at a lower temperature than Mg-pyroxene. Cristobalite is observed as a high-temperature crystallite in the pure-Mg compositions. Crystallisation activation energies are derived and discussed in relation to protoplanetary disks.
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Huang (黄俊), Jun, Zhiyong Xiao (肖智勇), Long Xiao (肖龙), Briony Horgan, Xiaoyi Hu (胡晓依), Paul Lucey, Xiao Xiao (肖潇), et al. "Diverse rock types detected in the lunar South Pole–Aitken Basin by the Chang’E-4 lunar mission." Geology 48, no. 7 (April 29, 2020): 723–27. http://dx.doi.org/10.1130/g47280.1.
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Abstract The South Pole–Aitken (SPA) basin, located between the South Pole and Aitken crater on the far side of the Moon, is the largest confirmed lunar impact structure. The pre-Nectarian SPA basin is a 2400 × 2050 km elliptical structure centered at 53°S, 191°E, which should have exposed lower crust and upper mantle due to the enormous excavation depth. Olivine, the dominant mineral in Earth’s mantle, has only been identified in small and localized exposures in the margins of the SPA basin, and the dominant mafic component is, instead, pyroxene. These mineralogical characteristics could be explained by the recent hypothesis that the lunar upper mantle is dominated by low-calcium pyroxene, not olivine. Here, we present observations from imaging and spectral data from China’s Chang’E-4 (CE-4) lunar mission in the first 4 synodic days, especially the first in situ visible/near-infrared spectrometer observations of an exposed boulder. We identified a variety of rock types, but not the recently reported olivine-rich materials in the landing region. The results are consistent with orbital observations. The obtained mineralogical information provides a better understanding of the nature and origin of SPA materials.
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MOMME, PETER, and J. RICHARD WILSON. "The Kraemer Island macrodyke, East Greenland: solidification of a flood basalt conduit." Geological Magazine 139, no. 2 (March 2002): 171–90. http://dx.doi.org/10.1017/s0016756801006070.
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The Kraemer Island macrodyke that is exclusively exposed on Kraemer Island about 7 km west of the Skaergaard Intrusion belongs to a regional dyke swarm termed the ‘Skaergaard-like dykes’ (or FG-1 dykes). Weakly modally layered olivine gabbros dominate the exposed parts of the intrusion that has a width of 650 m to 1000 m. Plagioclase (core An68±2) and Ca-rich pyroxene (core Mg no. 79±1) grains are normally zoned, whereas olivine grains (Fo50–65) are homogeneous. Calculated mineral–magma equilibria, based on experimentally determined Mg–Fe magma–olivine and magma–clinopyroxene partition coefficients, suggest that the observed olivine and clinopyroxene compositions in the gabbros cannot have formed from a common parental magma. The unzoned nature of olivine grains and their iron-rich com-positions relative to clinopyroxene suggest post-cumulus Mg–Fe exchange between olivine and interstitial melt. A gabbroic pegmatite is developed in the centre of the intrusion along its entire exposed 5 km strike length. Here, mineral zonation is limited and compositions are similar to rims of cumulus minerals in the enveloping olivine gabbros. The pegmatite could therefore represent interstitial melt mobilized from gabbroic cumulates that later accumulated and crystallized at its present stratigraphic location. Cumulus olivines in the gabbros are close to equilibrium with Ca-rich pyroxene in the pegmatite. This is interpreted as reflecting interstitial melt mobility during the late stages of solidification of the macrodyke. Chilled margins are well preserved at the intrusion margins and are rich in Fe (14–15.3% FeOTOT), Ti (3–3.3% TiO2) and light rare-earth elements ([La/Sm]N = 1.2–1.3), similar to magmas well represented in the overlying sequence of contemporaneous High-Ti Series flood basalts. It is therefore likely that extensive wall-rock melting adjacent to the macrodyke reflects continuous feeding of the overlying flood basalts through the Kraemer Island macrodyke.
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Hall, R. P., D. J. Hughes, and C. R. L. Friend. "Complex sequential pyroxene growth in tholeiitic hypabyssal rocks from southern West Greenland." Mineralogical Magazine 50, no. 357 (September 1986): 491–502. http://dx.doi.org/10.1180/minmag.1986.050.357.12.
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AbstractChemically complex pyroxenes which occur in early Proterozoic tholeiitic dolerite dykes in southern West Greenland have been investigated using back-scattered electron (BSE) imagery, X-ray mapping and electron microprobe analysis. A wide variety of compositions occur within individual pyroxene grains in these rocks. They can be explained by simultaneous nucleation of different pyroxenes, the evolution of domains around these nucleii as a response to differential chemical gradients and the sequential precipitation of different pyroxenes at progressively lower temperatures. As an example, the individual grains in one dyke sample contain domains of bronzite, hypersthene, magnesium pigeonite, augite, and subcalcic augite. Olivine in this sample varies in composition from Fo70to Fo33, although individual grains are only weakly zoned. The wide variation in pyroxene and olivine compositions suggests ranges of crystallization temperatures fromc.1250° to as low as 825°C. Such compositionally variable pyroxenes are possibly characteristic of hypabyssal tholeiitic rocks.
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Dasgupta, Somnath, Pulak Sengupta, A. Mondal, and M. Fukuoka. "Mineral chemistry and reaction textures in metabasites from the Eastern Ghats belt, India and their implications." Mineralogical Magazine 57, no. 386 (March 1993): 113–20. http://dx.doi.org/10.1180/minmag.1993.057.386.11.
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AbstractThree types of mafic granulites, namely two pyroxene-plagioclase granutite (MG), two pyroxeneplagioclase-garnet granulite (GMG) and spinel-olivine-plagioclase-two pyroxene granulite (SMG) are exposed at Sunkarimetta, Eastern Ghats belt, India. The marie granulites exhibit a foliation concordant with that in associated granulite facies quartzofeldspathic gneisses. Textural characteristics and mineral chemical data suggest the following mineral reactions: olivine + plagioclase = spinel + orthopyroxene + clinopyroxene (SMG), orthopyroxene + plagioclase = garnet + quartz (GMG), clinopyroxene + plagioclase = garnet + quartz (GMG) and plagioclase + hemoilmenite + quartz = garnet + ilmenite + 02 (GMG). Geothermobarometry indicates maximum P-T conditions of metamorphism at c. 8.5 kbar, 950°C The marie granulites later suffered nearly isobaric cooling to c. 7.5 kbar, 750°C Bulk compositional characteristics suggest that SMG is of cumulate origin. The protoliths of the mafic granulites, emplaced at c. 32 km depth, are probably responsible for thermal perturbation causing granulite facies metamorphism of the enclosing rocks.
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Wirth, R. "Nucleation of pyroxene and amphibole in glassy veins along interfaces and cracks in ultramafic inclusions from San Carlos, Arizona." Proceedings, annual meeting, Electron Microscopy Society of America 53 (August 13, 1995): 384–85. http://dx.doi.org/10.1017/s0424820100138294.
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Ultramafic inclusions occur in ellipsoidal bombs in basalt flows. The inclusions of the San Carlos ultramafic inclusion locality have been described in detail by Frey & Prinz (1978). They mainly consist of olivine, orthopyroxene (opx), clinopyroxene (cpx) and Cr-spinel. Ultramafic inclusions are important because they are samples of the upper mantle material, and thus they provide direct insight into the upper mantle processes and composition. Glassy veins are fairly abundant along mineral interfaces and cracks. The glass apparently results from incongruent melting of hydrous phases. The glassy veins are between a few nanometer and several microns wide. Veins with a width > 1 μm exhibit crystals of olivine, pyroxene and feldspar. The narrow veins (< 1 μm) only occasionally show crystallization of small crystals (several hundred nanometer). The early stages of crystallization of pyroxene and amphibole and the chemical composition have been investigated by HRTEM and analytical TEM.Glassy veins along interfaces: small grains (several hundred nanometer) of opx have nucleated at an opx/glass interface.
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Hitchings, R. S., M. S. Paterson, and J. Bitmead. "Effects of iron and magnetite additions in olivine-pyroxene rheology." Physics of the Earth and Planetary Interiors 55, no. 3-4 (June 1989): 277–91. http://dx.doi.org/10.1016/0031-9201(89)90076-9.
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Lunning, Nicole G., Harry Y. McSween, Travis J. Tenner, Noriko T. Kita, and Robert J. Bodnar. "Olivine and pyroxene from the mantle of asteroid 4 Vesta." Earth and Planetary Science Letters 418 (May 2015): 126–35. http://dx.doi.org/10.1016/j.epsl.2015.02.043.
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Koike, Chiyoe, and Akira Tsuchiyama. "The Infrared Spectra of Synthesized Amorphous Silicates with Compositions of Olivine and Pyroxene." International Astronomical Union Colloquium 126 (1991): 95–98. http://dx.doi.org/10.1017/s0252921100066550.
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AbstractAmorphous olivines synthesized by evaporation method show two very broad bands at 10-11 μm and 17.5-19 μm, which resemble the spectra of symbiotic stars. On the other hand, amorphous pyroxenes produced by the same method show two broad bands at 9.5-10.3 μ and 20-22 μ which are narrower than that of amorphous olivine. The features of amorphous olivine were easily altered by heating or hydration, and the peak wavelength of 18 μm band was easily shifted to longer wavelengths.
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Bial, J., and C. A. Trepmann. "The microstructural record of porphyroclasts and matrix of partly serpentinized peridotite mylonites – from brittle and crystal-plastic deformation to dissolution–precipitation creep." Solid Earth 4, no. 2 (October 11, 2013): 315–30. http://dx.doi.org/10.5194/se-4-315-2013.
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Abstract. We present microfabrics in high-pressure, metamorphic, partly serpentinized peridotite mylonites from the Voltri Massif, in which porphyroclasts and matrix record independent deformation events. The microfabrics are analysed using polarization microscopy and electron microscopy (SEM/EBSD, EMP). The mylonites contain diopside and olivine porphyroclasts originating from the mantle protolith embedded in a fine-grained matrix consisting mainly of antigorite and minor olivine and pyroxene. The porphyroclasts record brittle and crystal-plastic deformation of the peridotite at upper-mantle conditions and differential stresses of a few hundred MPa. After the peridotites became serpentinized, deformation occurred mainly by dissolution–precipitation creep resulting in a pronounced foliation of the antigorite matrix, crenulation cleavages and newly precipitated olivine and pyroxene from the pore fluid at sites of dilation, i.e. in strain shadows next to porphyroclasts and folded fine-grained antigorite layers. Antigorite reveals a pronounced associated shape preferred orientation (SPO) and crystallographic preferred orientation (CPO) with the basal (001) cleavage plane oriented in the foliation plane. In monomineralic antigorite aggregates at sites of stress concentration around porphyroclasts, a characteristically reduced grain size and deflecting CPO as well as sutured grain boundaries indicate also some contribution of crystal-plastic deformation and grain-boundary migration of antigorite. In contrast, the absence of any intragranular deformation features in newly precipitated olivine in strain shadows reveals that stresses were not sufficiently high to allow for significant dislocation creep of olivine at conditions at which antigorite is stable. The porphyroclast microstructures are not associated with the microstructures of the mylonitic matrix, but are inherited from an independent earlier deformation. The porphyroclasts record a high-stress deformation of the peridotite with dislocation creep of olivine in the upper mantle probably related to rifting processes, whereas the serpentinite matrix records dominantly dissolution–precipitation creep and low stresses during subduction and exhumation.
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Zolensky, Michael, and Ruth Barrett. "The genetic relationship between hydrous and anhydrous interplanetary dust particles." Proceedings, annual meeting, Electron Microscopy Society of America 50, no. 2 (August 1992): 1720–21. http://dx.doi.org/10.1017/s0424820100133230.
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It is a fundamental goal of interplanetary dust particle (IDP) research to determine the sources and histories of these primitive extraterrestrial materials. Chondritic IDPs have been divided into anhydrous and hydrous varieties, with sub-classification being made on the grounds of the dominant anhydrous (olivine or pyroxene) or hydrous (smectite or serpentine) present. The presumption is that hydrated IDPs experienced aqueous alteration on parent bodies (hydrous asteroids or possibly comets); we wish to discover whether the anhydrous IDPs were the initial raw materials for these reactions. We report here analyses of olivines and pyroxenes from 22 large (>15 um) chondritic IDPs: 18 anhydrous and 4 hydrous; olivines and pyroxenes are scarce in most hydrous IDPs, when present at all Finally, we compare anhydrous to hydrous IDPs, and both to chondritic meteorites.Figure 1 shows our results for this study. We find there to exist no significant difference in the compositions of olivines from olivine vs. pyroxene dominated IDPs, which are therefore plotted together (in contrast to our preliminary results for a smaller data set).
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Huo, Yonglin, Guilu Qin, Jichuan Huo, Xingquan Zhang, and Yongchang Zhu. "Crystallization Kinetics of Basalt Glass-Ceramics Produced from Olivine Basalt Rock." Crystals 12, no. 7 (June 24, 2022): 899. http://dx.doi.org/10.3390/cryst12070899.
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Glass-ceramics acquired from the melting of rocks have a vast application marketplace. In this study, an olivine basalt rock from Zhangjiakou in China was selected as a raw material to prepare basalt glass-ceramics, and the crystallization kinetics of olivine basalt glass was investigated using differential thermal analysis. Polarizing microscope and X-ray diffraction (XRD) analysis results revealed that the main mineral compositions of olivine basalt are plagioclase, pyroxene, olivine, and iron oxide(s). Three crystallization peaks were observed in the DSC curve of the olivine basalt glass. The Avrami exponent (n), apparent activation energies for the crystallization, and glass transition of basalt glass were determined using the Owaza method based on data obtained from isothermal measurements. The crystallization activation energies (E) of the three crystallization peaks of olivine basalt glass were 314.20 kJ/mol, 1232.49 kJ/mol, and 696.89 kJ/mol, respectively. In addition to this, the crystal growth index indicated that the crystallization mode in the olivine basalt glass was surface crystallization. The crystallization phases and microstructure of the olivine basalt glass heated at 860 °C, 1100 °C, and 1180 °C were also studied. The conclusions obtained offer some useful information for the preparation of basalt glass-ceramics from olivine basalt rocks.
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Ankushev, M. N., D. A. Artemyev, and I. A. Blinov. "Formation conditions of the bronze age metallurgical slags of the South Urals and Kazakhstan." МИНЕРАЛОГИЯ (MINERALOGY), no. 3 (October 28, 2020): 54–73. http://dx.doi.org/10.35597/2313-545x-2020-6-3-5.
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Four main mineralogical types are identifed among a wide variety of metallurgical slags from the bronze Age sites of the South Urals and Kazakhstan: chromite-bearing olivine, sulfde-bearing olivine, glassy sulfde-bearing and pyroxene. The slag types signifcantly difer in morphology, major and accessory minerals and composition of melt inclusions. The temperature of melt and the dynamics of its changes are estimated from phase diagrams and experimental studies. Crystallization models are proposed on the basis of ontogeny of newly formed minerals, relict inclusions, and possible temperatures for all slag types. Figures 15. Tables 3. References 46.
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Hodson, Mark. "Post-crystallisation modification of the igneous layering in the Nunarssuit and West Kûngnât syenites, South Greenland." Mineralogical Magazine 61, no. 407 (August 1997): 467–83. http://dx.doi.org/10.1180/minmag.1997.061.407.01.
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AbstractThe chemistry and textures of the minerals in the layered syenites of Nunarssuit and West Kûngnât record a complex post-crystallisation history. The initial cumulus phases were alkali feldspar, pyroxene and olivine, apatite and opaque oxides. Grain size distributions of the pyroxenes and olivines have been modified since crystallisation, possibly during transport of these grains in a density current, prior to deposition in layers. Olivines and pyroxenes re-equilibrated with intercumulus melt. The lower ratio of mafic phases to intercumulus fluid in leucocratic layers has resulted in pyroxene and olivine in these layers undergoing more re-equilibration that in melanocratic layers, consequently pyroxenes and olivines in leucocratic layers are more ferroan. Pyroxenes reacted with either intercumulus or deuteric fluid to form amphibole. In West Kûngnât pyroxene and amphibole re-equilibrated via a later fluid. Olivines reacted with deuteric fluid to produce biotites, probably at temperatures < 550°C. After crystallisation alkali feldspars exsolved, the exsolution textures coarsened in the presence of deuteric fluids with a magmatic origin, possibly at temperatures as low as 450°C. Zoning patterns of apatites and zircons were modified during interactions with either, or both intercumulus or deuteric fluids. Leucocratic layers underwent more modification than melanocratic ones, probably due to the higher concentration of intercumulus melt in the former leading to a higher concentration of deuteric fluids as water exsolved from the magma during cooling. The syenites underwent little compaction during solidification.
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Cheng, Zhiguo, Tong Hou, Jakob K. Keiding, Ilya V. Veksler, Vadim S. Kamenetsky, Marko Hornschu, and Robert B. Trumbull. "Comparative Geothermometry in High-Mg Magmas from the Etendeka Province and Constraints on their Mantle Source." Journal of Petrology 60, no. 12 (December 1, 2019): 2509–28. http://dx.doi.org/10.1093/petrology/egaa016.
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Abstract There is still debate whether Large Igneous Provinces (LIPs) are caused by high mantle temperatures induced by thermal plumes or by other factors that enhance melt production from the mantle. A prerequisite for assessing the thermal plume model is a reliable estimate of liquidus temperatures of the magmas produced, preferably based on more than one method of geothermometry. The study reported here compares multiple geothermometers for the Etendeka LIP, which is among the largest Phanerozoic examples and one that shows several features suggestive of a plume origin (continental flood basalt province linked via an age-progressive volcanic ridge to an active hotspot). Magnesium (Mg)-rich magmas emplaced as dikes in NW Namibia are the most primitive rocks known from this province and are thus best suited to determine the composition and melting conditions of their mantle source. Earlier studies of the Etendeka Mg-rich dikes reported high liquidus temperatures based on olivine-melt Mg–Fe equilibria. We extend that work to a larger set of samples and compare the results of olivine-melt Mg–Fe thermometry with other methods based on spinel-melt and spinel–olivine equilibria (Al-in-olivine thermometry), as well as olivine-melt trace-element exchange (Sc/Y thermometry and V oxybarometry). All methods used the same starting assumptions of nominally anhydrous melts and a crystallization pressure of 0·5 GPa. Only mineral-melt or mineral-mineral pairs consistent with compositional equilibrium were used for calculating temperatures. The trace-element compositions of olivine are also used to discuss the relative proportion of peridotite and pyroxenite in the mantle source for these magmas. Twelve dike samples were studied, with whole-rock MgO concentrations ranging from 8·4 to 19·4 wt %. Diagnostic element ratios of transition metals in olivine (e.g., Mn/Fe, Mn/Zn, Zn/Fe) indicate a peridotite-dominated mantle source for the magmas, which is consistent with the other indicators based on whole-rock data e.g., 10 000×Zn/Fe, CaO–MgO trend, FeO/MnO and FC3MS (FeO/CaO–3×MgO/SiO2). The temperature variations show a positive correlation with the Fo-content of host olivines, and values from high-Fo olivine agree well with olivine and spinel liquidus temperatures calculated from thermodynamic models of bulk-rock composition. All methods and most samples yielded a temperature range between 1300 °C and 1400 °C. An exceptional few samples returned temperatures below 1300 °C, the minimum being 1193 °C, whereas several samples yielded temperatures above 1400 °C, the upper range being 1420–1440°C, which we consider to be a robust estimate of the maximum liquidus temperatures for the high-Mg magmas studied. The conversion to mantle potential temperatures is complicated by uncertain depth and degree of melting, but the functional relationship between Tp and primary melt MgO contents, using melt inclusions from olivine phenocrysts with of Fo > 90, indicate a Tp range from 1414 to 1525 °C ( 42 °C), which is 100–150°C higher than estimates of ambient upper mantle Tp in the South Atlantic today.
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Koike, C., H. Shibai, and A. Tuchiyama. "Extinction of olivine and pyroxene in the mid- and far-infrared." Monthly Notices of the Royal Astronomical Society 264, no. 3 (October 1, 1993): 654–58. http://dx.doi.org/10.1093/mnras/264.3.654.
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Leshin, Laurie A., Alan E. Rubin, and Kevin D. McKeegan. "The oxygen isotopic composition of olivine and pyroxene from CI chondrites." Geochimica et Cosmochimica Acta 61, no. 4 (February 1997): 835–45. http://dx.doi.org/10.1016/s0016-7037(96)00374-2.
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de León, J., J. Licandro, R. Duffard, and M. Serra-Ricart. "Spectral analysis and mineralogical characterization of 11 olivine–pyroxene rich NEAs." Advances in Space Research 37, no. 1 (January 2006): 178–83. http://dx.doi.org/10.1016/j.asr.2005.05.074.
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Ibhi, Abderrahmane, Hassane Nachit, El Hassan Abia, and Jean Hernandez. "Intervention of carbonate components in petrogenesis of the pyroxene nephelinites from the Jbel Saghro (Anti-Atlas, Morocco)." Bulletin de la Société Géologique de France 173, no. 1 (January 1, 2002): 37–43. http://dx.doi.org/10.2113/173.1.37.
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Abstract Introduction. – The Jbel Saghro alkaline complex was emplaced close to the eastern edge of the Moroccan Anti-Atlas. Within the northern part, two types of nephelinite were recognized [Ibhi and Nachit, 1999 and Ibhi, 2000]. The first type (olivine-rich nephelinite) constitutes the main volcanic mass south of the Bou Gafer granit (fig. 1), where the volcanism had been active at least during 2 Ma, between 9.6 and 7.5 ± 0.1 Ma [Berrahma et al., 1993]. The second group outcrops in the north (Foum El Kouss). It consists of pyroxene nephelinites which are younger (2.9 ± 0.1 Ma) [Berrahma et al., 1993], and bears carbonatitic xenoliths, melteigitic pyroxenites and metasomatised peridotite xenoliths. Geochemically, the pyroxene nephelinite is highly enriched in LILE compared with the first one. The mineralogical and geochemical characteristics may be explained by the incorporation of carbonatitic and melteigitic pyroxenite segregates of carbonatitic affinity. Petrology and mineralogy. – Nephelinites. – The chemical analyses of minerals were done using the microprobe SX 50 of the micro-analysis laboratory (University of Nancy I) and of CAMPARIS (Paris VI). Chemical compositions of minerals are presented in table I. The petrographical and mineralogical studies show that these nephelinites could be subdivided into two groups : – olivine nephelinites (according to the terminology of Le Bas [1987]) are more or less rich in coloured minerals : olivine (Fo80–85), Ti-rich augite (3.8 to 4.5 wt. % TiO2) with relatively low Na2O (0.5 to 0.9 wt. %) and oxide (Ti-magnetite). Olivine phenocrysts are always present while augite exists only in the form of micro-phenocrysts. The groundmass is made up of augite, nepheline and Fe-Ti oxide micro-crystals; – clinopyroxene-rich nephelinites with strongly zoned phenocrysts;the green core of phenocrysts is Fe-rich diopside (11.4 to 13.4 wt % FeO and high Na2O up to 2,2 % wt. %). The rim is Ti-rich augite, similar to the augite micro-phenocrysts from olivine nephelinites. The olivines (Fo78–82) are present in the form of sub-automorph crystals of a composition less magnesian than that of the lower flow. The groundmass is formed by nepheline, plagioclase, sanidine and Ti-magnetite micro-crystals. Nature of enclaves Carbonatites. – Pyroxene nephelinite are characterized by the presence of calcite carbonatitic xenoliths. Their size is variable (a few millimeters to a few centimeters) and their texture is generally granular to micro-granular. Carbonate (table II) is a low-Mg (less than 0.4 wt. % MgO) calcite with high SrO (up to 3.4 wt. %) and relatively high BaO (1.2 wt. %). Rare Ba-Ti biotite, containing up to 21.5 wt. % BaO and 13.8 wt. % TiO2, occurs in the groundmass of most samples, along with SrO-rich (1.8 wt. %) fluorapatite (4 wt. % F). The pyrochlore is a niobozirconolite of a structural formula CaZr(Ti, Fe, Nb)2O7, generally associated to the magnetite and the apatite [Williams, 1996]. The mean for Nb2O5 of 4 analyses is 20.1 wt. % (range 17.5 to 20.9 wt. %), and for Zr O2 the mean is 23.2 wt. % (range 21.7 to 25.5 wt.). The clinopyroxene is diopside with Na2O up to 0.7 wt. % and Al2O3 up to 1.5 wt. % (table II). The presence of Sr-rich calcite and pyrochlore establish the carbonatitic nature of the xenolith [Ngwenya and Bailley, 1990]. According to the geothermometers of Stormer and Carmichael [1971], revised by Andersen and Austrheim [1991], the temperatures calculated for the exchange reaction F / OH between biotite and apatite, are situated between 650 and 665°C. Mineralogical studies do not allow the pressure of inhaduction for carbonatites, however the absence of dolomite suggests that their crystallization took place at pressures lower than to 3 kbar, according to the remarks by Le Bas [1987]. Peridotites. – The peridotite xenoliths contained in the nephelinites of Jbel Saghro are all, according to Hart’s [1977] nomenclature, of a porphyroclastic texture with a granuloblastic tendency. Two types can be mineralogically distinguished (table III) : – the first one does not contain any trace of destabilisation. It is characterized by an assemblage of minerals in equilibrium and with composition typical of mantle lherzolites : olivine (Fo90–91), orthopyroxene (En90–92), diopside (Ca46–59 Fe05–07 Mg43–47) and spinelle (mg* = 82 and 100 × Cr / (Cr+Al) = 10), which can be considered as primary ; – the second type, which occurs only in pyroxene nephelinites, is characterized by the presence of millimetric and pale-green reactional aggregates which are scattered throughout the sample and filled by a microgranular mineral assemblage. These aggregates are interconnected by a microveinlet network. The microgranular mineral assemblage consists of green diopside (containing up to 0.67 wt. % Al2O3 and 2,2 % wt. Cr2O3) rich in fluid inclusions of CO2, olivine (Fo90 – 91), chromite (100 × Cr / (Cr+Al) = 72 to 79) and interstitial anorthoclase (Ab52–56 , Or41–45 , An01–02). The scanning electronic microscope equally shows the presence of very small apatite crystals in these aggregates. Melteigitic pyroxenite cumulates. – A melteigitic pyroxenite inclusion has been found in a pyroxene nephelinite. Major phases are Na, Fe rich (4 wt. % Na2O and 20 wt. % FeO) diopside, nepheline (Ne69 – Ks27 – Qz04) and SrO rich (1.5 wt. %) fluorapatite (3.5 wt. % F). Carbonate globules are common in these xenoliths. The carbonate is SrO rich (2.3 to 5.0 wt. %), FeO, MgO and LREE barely detectable with the electron microprobe. Geochemistry. – Major and trace element analyses for Jbel Saghro nephelinite and carbonatite xenoliths are presented in table IV. Major elements were analyzed by ICP and trace elements by ICP-MS with LabRobStation system (rocks and minerals analysis service, Nancy). The nephelinites are strongly SiO2 undersaturated (< 43 wt. %) and they contain 15 to 25 % of normative nepheline. Globally, the two types of nephelinites show similar trends, which suggests a possible common source. According to this hypothesis, the LILE increase observed in the pyroxene nephelinites can be explained by a decrease of partial melting rate, which would be in agreement with its higher under-saturation in SiO2. However, in comparison with the olivine nephelinites, the pyroxene nephelinites are clearly enriched in HREE (fig. 2) and in the less incompatible elements (fig. 3) while the Th, U, Rb, and K concentrations are similar. This observation argues against the previous hypothesis and suggests a more complicated petrogenetic process for the pyroxene nephelinite. Discussions and conclusions. – The petrological study of peridotite xenoliths from the pyroxene nephelinite shows that the lithospheric mantle of this region was metasomatised. Metasomatism is represented by extensive petrological and mineralogical changes [Ibhi et al., 1999c]. The reactions produce aggregates, which are predominantly composed of high-Cr diopside, alkali feldspar, chromite and apatite. The paragenesis described in these samples and the experimental data on the peridotite-carbonate systems [Brey et al., 1983] suggest that the reacting fluid was carbonate rich. The abundance of CO2 inclusions observed in these peridotites also favours this interpretation. It remains to be seen whether a carbonatitic origin is possible for these pyroxenite cumulates. Their mineralogy (diopside + apatite + Ti-magnetite + nepheline + calcite) is well known in the pyroxenites of carbonatitic complexes [Le Bas, 1977; Bouabdli, 1994], they can be considered as melteigitic. The petrogenetic relationship between carbonatites and pyroxene nephelinites has been previously emphasised by Le Bas [1987]. Globally, the pyroxene nephelinites are caracterized by: (i) the presence of phenocrysts of highly reverse zoned clinopyroxene : green core of Na, Fe rich diopside partially resorbed and pink rim of augite (table I), this one is rich fluid CO2 inclusions; (ii) the presence of small carbonatite xenoliths, (iii) a considerable enrichment in HREE and in the less incompatible elements while the Th, U, Rb, and K concentrations are similar. This shows that there is an intervention of carbonatite segregates in the petrogenesis of these pyroxene nephelinite. The intervention of a carbonatitic component during the petrogenesis of the Jbel Saghro pyroxene nephelinite can be geochemically evidenced by the variations of ratios implying trace elements fractionated by carbonates [Hamilton et al., 1989; Brenan and Watson, 1991]. Thus, the decrease of Hf / Sm and the increase of Ba / Th and Sr / Th between olivine nephelinite and pyroxene nephelinite are in good agreement with this carbonatitic influence.
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McCausland, Phil J. A., Roberta L. Flemming, Graham C. Wilson, Jim Renaud, David Dillon, and David W. Holdsworth. "The Wood Lake, Ontario, H4 ordinary chondrite, a new Canadian meteorite." Canadian Journal of Earth Sciences 50, no. 1 (January 2013): 32–43. http://dx.doi.org/10.1139/e2012-037.
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The Wood Lake meteorite was found in the Muskoka region of Ontario in July 2003. We examine the mineralogy, physical properties, shock, and weathering state of this recently reported Canadian meteorite. Bulk physical properties for Wood Lake (bulk density 3.57 ± 0.10 g/cm3, grain density 3.64 ± 0.01 g/cm3, and magnetic susceptibility log χ = 5.17) are typical of slightly weathered H chondrite falls and consistent with visual observations of its observed low weathering state (W1). Reconnaissance X-ray micro computed tomography of a Wood Lake fragment yields a similar bulk density (3.56 g/cm3) and allows for a three-dimensional description of the meteorite. Petrographic and electron probe microanalysis examination of the Wood Lake meteorite reveal sharp definition of chondrule margins, occasional mesostasis chondrule glass, only minor development of recrystallized matrix feldspar, and little variation in silicate chemical compositions, indicating Wood Lake to be an H4 ordinary chondrite. Mineral chemistry for Wood Lake olivine (Fa18.6 ± 0.7, n = 26) and low-Ca pyroxene (Fs17.5 ± 2.6, n = 16) agrees well with H chondrite averages for these minerals. The bulk of the stone has undergone a low to moderate level of shock (S3), as indicated in thin section by undulose optical extinction and the presence of planar dislocations in olivine and pyroxene grains. Moderate distortion of olivine crystal structures observed using in situ micro X-ray diffraction quantifies the shock deformation as a full width half maximum (FWHMχ) of 3.38° ± 1.13° (16 reflections from seven olivine grains), consistent with shock stage S3 ordinary chondrites. Wood Lake is confirmed as a new Canadian meteorite find that likely arrived on Earth not long before it was recovered.
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Bernstein, Stefan, Minik T. Rosing, C. Kent Brooks, and Dennis K. Bird. "An ocean-ridge type magma chamber at a passive volcanic, continental margin: the Kap Edvard Holm layered gabbro complex, East Greenland." Geological Magazine 129, no. 4 (July 1992): 437–56. http://dx.doi.org/10.1017/s001675680001952x.
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AbstractThe gabbros of the Tertiary Kap Edvard Holm Layered Serieshave a stratigraphic thickness of more than 5000 m. Earlier work has shown that the range in cumulus mineral compositions is restricted (plagioclase An81—An51; olivine Fo85—Fo66; pyroxenes Ca43Mg46Fe11 to Ca43Mg37Fe20). Field evidence of magma injections is common, which together with the restricted range in mineral chemistry suggests that the magma chamber was frequently replenished by a less fractionated magma. A detailed study of a 600 m section (900–1500 m) in the Lower Layered Series reveals a period of crystallization when the magma chamber behaved as a closed system (900–1300 m). The rocks formed during this periodare well-laminated olivine–gabbros (900–110 m), which evolved to well-laminated oxide-gabbros (1100–1300 m). Compositional trends in the cumulusminerals are towards more evolved compositions (plagioclase An64—An58, pyroxene Mg# from 80 to 76) with stratigraphic height. From 1300 m to 1500 m, granular olivine-gabbros dominate, with moreprimitive mineral compositions (plagioclase An67—An76, pyroxene Mg# from 78 to 82). The transition olivine–gabbro to oxide-gabbro at 1100m is a consequence of fractional crystallization, and it is shown how changes in activities of FeO and Fe203 in the magma are reflected in the total iron content of plagioclases.The transition from oxide-gabbro to olivine-gabbro at 1300 m results from replenishment by less evolved basaltic magma. On the basis of calcic pyroxene chemistry and the mineral crystallization sequence it is concluded that the Kap Edvard Holm Layered Series crystallized from a tholeiitic magma similar to MORB. Melanogabbroic units occur throughout the intrusion as discordant to subconcordant sill-like bodies 0.2–2.0 m thick. The melanogabbroic units consist of Cr-rich augite-olivine-plagioclase heteradcumulates and contain deformed mica crystals of pre-emplacement origin. These units crystallized from a wet, MgO-rich magma which was injected into the layered host gabbros after the formation of the cumulus pile, but before the magma was completely solidified.The Kap Edvard Holm Layered Series has several parallels with the plutonic part of ophiolite sequences. These include: cumulus mineral assemblage, compositions of the minerals and the restricted range in compositions with stratigraphic height; field evidence of repeated replenishment of basaltic magma; dyke swarms overlying the roof zone of the magma chamber; and the existence of a late intrusive suite of wet, MgO-rich magma. These parallels suggest that the processes involved in the formation of the Kap Edvard Holm Layered Series were similar to those involved in the formation of the crustalpart of many ophiolites and beneath present-day spreading ridges. The Kap Edvard Holm Layered Series is therefore believed to represent a shallow-level magma chamber which acted as a reservoir for basaltic flows at the continental margin during the opening of the North Atlantic Ocean.
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Huang, Ruifang, Weidong Sun, Maoshuang Song, and Xing Ding. "Influence of pH on Molecular Hydrogen (H2) Generation and Reaction Rates during Serpentinization of Peridotite and Olivine." Minerals 9, no. 11 (October 28, 2019): 661. http://dx.doi.org/10.3390/min9110661.
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Serpentinization produces molecular hydrogen (H2) that is capable of supporting communities of microorganisms in hydrothermal fields, which suggests that serpentinization may be closely related to the origin of life at the early history of the Earth and possibly other planets. In this study, serpentinization experiments were performed at 300 °C and 3.0 kbar with natural olivine and peridotite as starting reactants to quantify the influence of acidic and alkaline solutions on the processes of serpentinization. The results reveal that acidic and alkaline solutions greatly influence molecular hydrogen (H2) generation and the rates of serpentinization. Acidic (pH = 2.50) and alkaline solutions (pH = 13.5) increased H2 production and the rates of peridotite serpentinization. Highly acidic solutions (2 M HCl), however, decreased the production of H2 after peridotite serpentinization by around two orders of magnitude. The decrease in H2 production was associated with a sharp decline in the rates of reaction; e.g., when peridotite was reacted with neutral solutions (0.5 M NaCl), 88% of reaction progress was achieved after an experimental duration of 27 days, and the reaction extent decreased by ~50% for experiments with highly acidic solutions (2 M HCl) over the same period. In contrast, for experiments with solely olivine, highly acidic solutions (2 M HCl) promoted the rates of olivine serpentinization and H2 production. The contrasting effect of highly acidic solutions (2 M HCl) on the processes of olivine and peridotite serpentinization may reflect the influence of pyroxene minerals, which could release SiO2 during peridotite serpentinization and, consequently, hydrogen generation and reaction rates may decrease. The experimental results of this study suggest that H2 production and the rates of serpentinization can be greatly influenced by acidic and alkaline solutions and co-existing minerals (e.g., pyroxene).
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Wang, Bao Hua, Shi Jie Li, and Bing Kui Miao. "The Mineral Chemistry and Classification of New Ordinary Chondrites Collected in Antarctica." Advanced Materials Research 621 (December 2012): 125–29. http://dx.doi.org/10.4028/www.scientific.net/amr.621.125.
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Petrography and mineral chemistry of ninety-eight ordinary chondrites from Grove Mountains, Antarctica, have been studied, in order to assign their chemical-petrographic types. The chemical-petrographic types of these meteorites are presented below: 36 H-groups (21 H4, 9 H5, 6 H6) and 62 L-groups (25 L5, 37 L6). The compositions of olivines and low-Ca pyroxenes in the all these ordinary chondrites have similar composition, respectively, reflecting some degree thermodynamics equilibration in them. The weathering degrees of all the ordinary chondrites, consisting of predominant weathering degrees of W1, suggest lightly weathered among them. More than 30% meteorites experienced severe shock metamorphism, as indicated by the presences of shock-induced melt veins and pockets. These heavily shocked meteorites provide us with natural samples for study of high-pressure polymorphs of minerals.
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Khisina, N. R., R. Wirth, and M. A. Nazarov. "Lamellar pyroxene-spinel symplectites in lunar olivine from the Luna 24 regolith." Geochemistry International 49, no. 5 (May 2011): 449–58. http://dx.doi.org/10.1134/s0016702911050041.
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Klöck, W., K. L. Thomas, D. S. McKay, and H. Palme. "Unusual olivine and pyroxene composition in interplanetary dust and unequilibrated ordinary chondrites." Nature 339, no. 6220 (May 1989): 126–28. http://dx.doi.org/10.1038/339126a0.
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Liu, Fujiang, Rong Yang, Ying Zhang, Le Qiao, Shun Wang, Yang Yang, and Xiaopan Wang. "Distribution of olivine and pyroxene derived from Clementine data in Crater Copernicus." Journal of Earth Science 22, no. 5 (September 30, 2011): 586–94. http://dx.doi.org/10.1007/s12583-011-0209-2.
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Boesenberg, Joseph S., and Roger H. Hewins. "An experimental investigation into the metastable formation of phosphoran olivine and pyroxene." Geochimica et Cosmochimica Acta 74, no. 6 (March 2010): 1923–41. http://dx.doi.org/10.1016/j.gca.2009.12.008.
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