Chemical composition and crystal structure of merrillite from the Suizhou meteorite

Xie, Xiande; Yang, Hexiong; Gu, Xiangping; Downs, Robert T.

doi:10.2138/am-2015-5488

Cited by 30 publications

(22 citation statements)

References 18 publications

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“…It was suggested that REE‐poor merrillite has doublet in the region of ν 1 vibrations, similarly to those in present work; however, REE‐bearing merrillite has only one asymmetric peak at 968–970 cm −1 , indicating that incorporation of REE to Ca(B)‐site results in a more uniform bonding environment for all phosphate groups . In contrast to apatite, the doublet in ν 1 region may correspond to averaged P‐O vibrations in non‐equivalent P(B1) and P(B2) positions in the crystal structure suggested by X‐ray refinement . It should be noticed also that recently structural refinement of Fe‐endmember ferromerrillite was reported …”

Section: Discussionmentioning

confidence: 89%

Raman spectroscopy of various phosphate minerals and occurrence of tuite in the Elga IIE iron meteorite

Litasov

Podgornykh

2017

J Raman Spectroscopy

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The Raman spectra of phosphate minerals: apatite, merrillite, panethite, brianite, czochralskiite, maricite, new phosphate with composition of Na2Fe(Mg,Ca)(PO4)2 and high‐pressure phase tuite from the Elga IIE iron meteorite are characterized. Panethite, brianite, czochralskiite and new Na‐Fe phosphate were described for the first time. The basic features of all studied phosphates include strong ν1 symmetric stretching mode of PO43− ions at 950–990 cm−1, antisymmetric ν3 vibrations in the 1000–1175 cm−1 region and weak bands in the 400–500 cm−1 region, which correspond to ν2 bending mode and in the 550–640 cm−1 region, related to ν4 bending mode. Weak bands at less than 300 cm−1 represent lattice modes. Most of the studied phosphates have three non‐equivalent positions of phosphorus atoms in the crystal structures and can be derived from glaserite, K3Na(SO4)2, arrangement. Two or three of non‐equivalent [PO4] tetrahedra typically correspond to two or three strong bands in the region of ν1 vibrations. High‐pressure mineral tuite has similar composition and was formed after merrillite. P‐O vibrations in equivalent [PO4] tetrahedra produce major Raman band of tuite at 972 cm−1. The Elga parent‐body experienced a shock pressure of at least 12–15 GPa according to minimum pressures of tuite formation in the static high‐pressure experiments. This is the first finding of tuite in iron meteorites and the only second finding of high‐pressure mineral in them. Copyright © 2017 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 89%

Raman spectroscopy of various phosphate minerals and occurrence of tuite in the Elga IIE iron meteorite

Litasov

Podgornykh

2017

J Raman Spectroscopy

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“…Merrillite was indexed against a trigonal symmetry (Xie et al. ), with parameters of a = 10.3444, b = 10.3444, c = 37.0182, α = 90°, β = 90°, γ = 120°. The interaction volume for diffracted electrons using these parameters is estimated to be a few tens of nanometers in width and depth (Darling et al.…”

Section: Analytical Techniquesmentioning

confidence: 99%

“…Generated apatite diffraction patterns were matched to a hexagonal unit cell using crystal lattice parameters of (Wilson et al 1999) a = 9.4555, b = 9.4555, c = 6.8836, and a = 90°, b = 90°, c = 120°. Merrillite was indexed against a trigonal symmetry (Xie et al 2015), with parameters of a = 10.3444, b = 10.3444, c = 37.0182, a = 90°, b = 90°, c = 120°. The interaction volume for diffracted electrons using these parameters is estimated to be a few tens of nanometers in width and depth (Darling et al 2016).…”

Section: Electron Backscatter Diffractionmentioning

confidence: 99%

“…; Xie et al. ), but it has been found to contain a small amount of volatile species in some meteorites (e.g., McCubbin et al. ).…”

Section: Introductionmentioning

confidence: 99%

“…Composition of apatite from mare basalts is close to pure fluorapatite (e.g., Jolliff et al 1993) with minor amounts of OH and Cl, whereas apatite in highlands samples can contain significantly more Cl (e.g., Barnes et al 2014). Merrillite is a nominally anhydrous phosphate mineral with an ideal composition of Ca 9 Na(Fe,Mg)(PO 4 ) 7 crystallizing in trigonal R3c symmetry Xie et al 2015), but it has been found to contain a small amount of volatile species in some meteorites (e.g., McCubbin et al 2014). In lunar rocks, merrillite is found to accommodate significant amounts of REEs in its structure, resulting in a very complex stoichiometric formula Jolliff et al 2006).…”

Section: Introductionmentioning

confidence: 99%

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Shock‐induced microtextures in lunar apatite and merrillite

Černok

White

Darling

et al. 2019

Meteorit & Planetary Scien

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Apatite and merrillite are the most common phosphate minerals in a wide range of planetary materials and are key accessory phases for in situ age dating, as well as for determination of the volatile abundances and their isotopic composition. Although most lunar and meteoritic samples show at least some evidence of impact metamorphism, relatively little is known about how these two phosphates respond to shock‐loading. In this work, we analyzed a set of well‐studied lunar highlands samples (Apollo 17 Mg‐suite rocks 76535, 76335, 72255, 78235, and 78236), in order of displaying increasing shock deformation stages from S1 to S6. We determined the stage of shock deformation of the rock based on existing plagioclase shock‐pressure barometry using optical microscopy, Raman spectroscopy, and SEM‐based panchromatic cathodoluminescence (CL) imaging of plagioclase. We then inspected the microtexture of apatite and merrillite through an integrated study of Raman spectroscopy, SEM‐CL imaging, and electron backscatter diffraction (EBSD). EBSD analyses revealed that microtextures in apatite and merrillite become progressively more complex and deformed with increasing levels of shock‐loading. An early shock‐stage fragmentation at S1 and S2 is followed by subgrain formation from S2 onward, showing consistent decrease in subgrain size with increasing level of deformation (up to S5) and finally granularization of grains caused by recrystallization (S6). Starting with 2°–3° of intragrain crystal‐plastic deformation in both phosphates at the lowest shock stage, apatite undergoes up to 25° and merrillite up to 30° of crystal‐plastic deformation at the highest stage of shock deformation (S5). Merrillite displays lower shock impedance than apatite; hence, it is more deformed at the same level of shock‐loading. We suggest that the microtexture of apatite and merrillite visualized by EBSD can be used to evaluate stages of shock deformation and should be taken into account when interpreting in situ geochemically relevant analyses of the phosphates, e.g., age or volatile content, as it has been shown in other accessory minerals that differently shocked domains can yield significantly different ages.

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Original and alteration mineral phases in the NWA 10628 Martian shergottite determined by micro‐Raman spectroscopy assisted with micro‐energy dispersive X‐ray fluorescence imaging

Prieto‐delaVega

García‐Florentino

Torre‐Fdez

et al. 2022

J Raman Spectroscopy

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NorthWest Africa 10628 (NWA 10628) is a shergottite found in Tindouf (Algeria) in 2014. Little is known on this meteorite apart from the Meteoritical Bulletin report. In this work, original and altered mineral phases of NWA 10628 were characterised by micro‐Raman spectroscopy assisted with micro‐energy dispersive X‐ray fluorescence imaging. The matrix of the meteorite is dominated by high‐Ca pyroxenes, augite ((Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6) and diopside (CaMgSi2O6). Olivine and feldspars appeared as small crystals all along the matrix. Merrillite (Ca9NaMg(PO4)7) was found as big crystals in inclusions. As whitlockite (Ca9NaMg(PO4)6(HPO4)) can be transformed into merrillite at high temperature and pressure, we suggest that merrillite in the meteorite was originally whitlockite, before its ejection from Mars. Gypsum (CaSO4·2H2O) was found as small crystals and in fractures; this last one could come from terrestrial weathering because it was associated with calcite (CaCO3). Small anhydrite (CaSO4) crystals are shown in the bulk together with gypsum, probably from the partial dehydration of original Martian gypsum by the high‐pressure/temperature of ejection. Pyrite and marcasite (FeS2 polymorphs) minerals were detected, as well as their oxidation products, goethite (α‐FeO (OH)) and rozenite (FeSO4·4H2O), due to their terrestrial weathering. The identification of hematite (Fe2O3), magnetite (Fe3O4), ilmenite (FeTiO3) and anatase (TiO2) suggested that ulvospinel (Fe2TiO4) was the precursor on Mars, because ulvospinel is transformed into ilmenite by pressure and later ilmenite can be altered to magnetite/hematite and anatase by oxidative weathering on Earth. This non‐destructive analytical methodology provides deep mineralogical characterisation adequate for scarce samples like those returning from the Mars Sample Return mission.

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Chemical composition and crystal structure of merrillite from the Suizhou meteorite

Cited by 30 publications

References 18 publications

Raman spectroscopy of various phosphate minerals and occurrence of tuite in the Elga IIE iron meteorite

Raman spectroscopy of various phosphate minerals and occurrence of tuite in the Elga IIE iron meteorite

Shock‐induced microtextures in lunar apatite and merrillite

Original and alteration mineral phases in the NWA 10628 Martian shergottite determined by micro‐Raman spectroscopy assisted with micro‐energy dispersive X‐ray fluorescence imaging

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