Graftonite-(Mn), ideallyM1MnM2,M3Fe2(PO4)2, and graftonite-(Ca), ideallyM1CaM2,M3Fe2(PO4)2, two new minerals of the graftonite group from Poland

Pieczka, Adam; Hawthorne, Frank C.; Ball, Neil A.; Abdu, Yassir A.; Gołębiowska, Bożena; Włodek, Adam; Żukrowski, J.

doi:10.1180/minmag.2017.081.109

Cited by 4 publications

(2 citation statements)

References 38 publications

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“…The interstices are mainly filled with rock-forming cristobalite or locally with small dendritic plagioclase and K-Na feldspar in small zones of high-silica Krich peraluminous glass. Accessory phases include fluorapatite and Fe-Mn-Ca phosphate, presumably from the graftonite-group (Figure 3f), with ideal crystal chemical formula (Fe 2+ MnCa) 3 (PO 4 ) 2 [19,20]. Vugs in the matrix are filled with supergene secondary phases: goethite, jarosite, calcite, and unidentified Si-Fe-P-H 2 O-bearing phases.…”

Section: Cristobalite-fayalite Paralavamentioning

confidence: 99%

Melting Processes of Pelitic Rocks in Combustion Metamorphic Complexes of Mongolia: Mineral Chemistry, Raman Spectroscopy, Formation Conditions of Mullite, Silicate Spinel, Silica Polymorphs, and Cordierite-Group Minerals

Peretyazhko,

Savina

2023

Geosciences

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Melted rocks (clinkers and paralavas) of the Mongolian combustion metamorphic (CM) complexes were formed during modern and ancient (since the Quaternary) wild-fires of brown coal layers in the sedimentary strata of the Early Cretaceous Dzunbain Formation. According to XRD, Raman spectroscopy, and SEM-EDS data, cordierite, sekaninaite, indialite, ferroindialite, silica polymorphs, mullite, Fe-mullite, anhydrous Al-Fe-Mg silicate spinel (presumably new mineral), and other phases were identified. It has been established that isomorphic impurity of potassium in the cordierite-group minerals does not correlate with their crystal structure (hexagonal or orthorhombic). Indialite and ferroindialite retained their hexagonal structure in some fragments of the CM rocks, possibly due to the very fast cooling of local zones of sedimentary strata and the quenching of high-temperature K-rich peraluminous melt. Clinkers, tridymite–sekaninaite, and cristobalite–fayalite ferroan paralavas were produced by partial melting of Fe-enriched pelitic rocks (mudstone, siltstone, and silty sandstone) in a wide temperature range. The formation of mullite, Fe-mullite, and Al-Fe-Mg silicate spinel in clinkers developed from dehydration–dehydroxylation and incongruent partial melting of Fe-enriched pelitic matter (Al-Mg-Fe-rich phyllosilicates, ‘meta-kaolinite’, and ‘meta-illite’). Large-scale crystallization of these minerals in the K-rich peraluminous melts occurred, presumably, in the range of T > 850–900 °C. The subsurface combustion of coal layers heated the overburden pelitic rocks from sedimentary strata to T > 1050 °C (judging by the formation of cordierite-group minerals) or locally till the melting point of detrital quartz grains at T > 1300 °C and, possibly, till the stability field of stable β-cristobalite at T > 1470 °C. Ferroan paralavas were formed during the rapid crystallization of Fe-rich silicate melts under various redox conditions. From the analysis of the liquidus surface in the Al2O3–FeO–Fe2O3–SiO2 major-oxide system, it follows that the least high-temperature (<1250 °C) and the most oxidizing conditions occurred during the crystallization of mineral assemblages in the most-enriched iron silicate melts parental for cristobalite–fayalite paralava.

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Section: Cristobalite-fayalite Paralavamentioning

confidence: 99%

Melting Processes of Pelitic Rocks in Combustion Metamorphic Complexes of Mongolia: Mineral Chemistry, Raman Spectroscopy, Formation Conditions of Mullite, Silicate Spinel, Silica Polymorphs, and Cordierite-Group Minerals

Peretyazhko,

Savina

2023

Geosciences

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“…A mineralogical and metallographic description of the meteorite is given by Buchwald [9] who mentioned the enrichment of the Augustinovka in centimeter-sized troilite nodules of nearly spherical shape, which are clearly visible at the front cut of the main meteorite mass [10]. Millimeter-sized phosphate inclusions in troilite from the Augustinovka were first encountered by Olsen and Fredriksson [11,12] who identified them as being composed of sarcopside, (Fe,Mn) 3 (PO 4 ) 2 , with minor amounts of Ca-free graftonite (the latter mineral is now classified as graftonite-(Mn) [13]).…”

Section: The Augustinovka Meteoritementioning

confidence: 99%

Xenophyllite, Na4Fe7(PO4)6, an Exotic Meteoritic Phosphate: New Mineral Description, Na-ions Mobility and Electrochemical Implications

et al. 2020

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Xenophyllite, ideally Na4Fe7(PO4)6, is a rare meteoritic phosphate found in phosphide-phosphate assemblages confined to troilite nodules of the Augustinovka iron meteorite (medium octahedrite, IIIAB). The mineral occurs as tiny lamella up to 0.15 mm long cross-cutting millimeter-sized grains of sarcopside, Fe3(PO4)2, associated with schreibersite, chromite and pentlandite. Xenophyllite is translucent, has a bluish-green to grey-green color and vitreous lustre. Moh’s hardness is 3.5–4. Cleavage is perfect on {001}. Measured density is 3.58(5) g/cm3. The mineral is biaxial (−), 2V 10–20°, with refractive indexes: α 1.675(2), β 1.681(2), γ 1.681 (2). Chemical composition of the holotype specimen (electron microprobe, wt.%) is: Na2O 10.9, K2O 0.4, MnO 5.8, FeO 42.1, Cr2O3 0.8, P2O5 40.7, total 100.7, corresponding to the empirical formula (Na3.67K0.09)Σ3.76(Fe2+6.12Mn2+0.85Cr0.11)Σ7.08P5.99O24.00. Xenophyllite is triclinic, P1 or P-1, a 9.643(6), b 9.633(5), c 17.645(11) Å; α 88.26(5), β 88.16(5), γ 64.83(5)°, V 1482(2) Å3, Z = 3. The toichiome C-centered subcell has the following dimensions: a 16.257(9), b 10.318(8), c 6.257(9) Å, β = 112.77(9)°, V 968(2) Å3, Z = 2. Xenophyllite is structurally related to synthetic phosphate Kna3Fe7(PO4)6 having a channel-type structure, and galileiite, NaFe4(PO4)3. The variations of chemical composition of xenophyllite ranging from Na4Fe7(PO4)6 to almost Na2Fe8(PO4)6 are accounted for by Na-ions mobility. The latter property makes xenophyllite a promising prototype for cathode materials used in sodium-ion batteries.

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Cristobalite Clinker and Paralavas of Ferroan and Melilite–Nepheline Types in the Khamaryn-Khural–Khiid Combustion Methamorphic Complex, East Mongolia: Formation Conditions and Processes

Savina,

Peretyazhko

2023

Russian Geology and Geophysics

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—Rock samples from the Khamaryn-Khural–Khiid combustion metamorphic (CM) complex, including cristobalite clinker, ferroan tridymite–sekaninaite and cristobalite–fayalite paralavas, which are rock types new to the complex, as well as clinker xenoliths in melilite–nepheline paralava, have been studied in terms of chemistry and mineralogy. The obtained data on rock-forming, minor, accessory, and rare phases (silica polymorphs, cordierite-group minerals, fayalite, Fe and Ti oxides, ferrosilite, etc.) have implications for the formation conditions and processes of the CM rocks. The Raman spectra of sekaninaite, indialite, ferroindialite, mullite, and anhydrous Fe–Ca–Mn phosphate, presumably from the graftonite group, have several specific features. The diversity of mineral assemblages in the CM rocks is due to heterogeneous lithology of the sedimentary protolith and to local effects in the multistage history of the Khamaryn-Khural–Khiid complex. According to geochemical data, all CM rocks of the complex are derived from the Early Cretaceous Dzunbain Formation, their protolith molten to different degrees. The cristobalite clinker and tridymite–sekaninaite and cristobalite–fayalite paralavas were produced by partial melting of pelitic rocks containing different amounts of iron in a wide temperature range. The formation of mullite developed from dehydration–dehydroxylation and incongruent partial melting of amorphous pelitic matter. Large-scale crystallization of mullite in clinker, occurred from the high-silica potassic aluminosilicate melt at >850 °C. Combustion of subsurface coal seams heated the overburden to >1050 °C or locally to >1300–1400 °C (melting point of detrital quartz) or even, possibly, to >1470 °C corresponding to the stability field of β-cristobalite. Melilite–nepheline paralava was formed by incongruent melting of silicate (pelitic) and carbonate (calcite) components of marly limestone under elevated CO2 partial pressure. Oxygen fugacity (fO2) during combustion metamorphism changed from strongly reducing conditions favorable for crystallization of Fe phosphides (barringerite, schreibersite) and metallic iron from silica-undersaturated melts parental to melilite–nepheline paralava to high fO2 values that can maintain the formation of hematite in Fe-rich CM rocks.

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Graftonite-(Mn), ideally^M1Mn^M2,M3Fe₂(PO₄)₂, and graftonite-(Ca), ideally^M1Ca^M2,M3Fe₂(PO₄)₂, two new minerals of the graftonite group from Poland

Cited by 4 publications

References 38 publications

Melting Processes of Pelitic Rocks in Combustion Metamorphic Complexes of Mongolia: Mineral Chemistry, Raman Spectroscopy, Formation Conditions of Mullite, Silicate Spinel, Silica Polymorphs, and Cordierite-Group Minerals

Melting Processes of Pelitic Rocks in Combustion Metamorphic Complexes of Mongolia: Mineral Chemistry, Raman Spectroscopy, Formation Conditions of Mullite, Silicate Spinel, Silica Polymorphs, and Cordierite-Group Minerals

Xenophyllite, Na4Fe7(PO4)6, an Exotic Meteoritic Phosphate: New Mineral Description, Na-ions Mobility and Electrochemical Implications

Cristobalite Clinker and Paralavas of Ferroan and Melilite–Nepheline Types in the Khamaryn-Khural–Khiid Combustion Methamorphic Complex, East Mongolia: Formation Conditions and Processes

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