The crystal chemistry of whitlockite and merrillite and the dehydrogenation of whitlockite to merrillite

Hughes, John M.; Jolliff, Bradley L.; Rakovan, John

doi:10.2138/am.2008.2683

Cited by 69 publications

(94 citation statements)

References 12 publications

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“…This excess Ca was evidently taken up by subsolidus plagioclase crystals as they developed reverse zoning (Figure 5), as well as by the melt phase, and thence liquidus anorthite microlites (Figures 4d, 4e). The phosphate in these two samples is thus inferred to have been transformed into a different whitlockite-like mineral, of which several are known in both natural and synthetic systems (e.g., Morozov et al, 2002;Kara & Stevens, 2003;Hughes, Jolliff, & Rakovan, 2008). Merrillite [Ca 18 Mg 2 (PO 4 ) 14 ] is one candidate; it also has a CaO/P 2 O 5 (MP) ratio of 2.7 but it contains about twice the amount of magnesia (3.8% MgO) as the phosphate in CSP-2 and CSP-8.…”

Section: Discussionmentioning

confidence: 99%

Microstructures of phosphatic porcelain from sintering to vitrification: Evidence from sherds excavated in Charleston, South Carolina

Owen

Hunter²,

Jellicoe

et al. 2011

Geoarchaeology

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Eight phosphatic porcelain sherds recovered from various historical sites in Charleston were analyzed by electron microprobe. Some sherds contain sulfur (2.3-3.1 wt.% SO 3 ); others contain only traces of this component. The analytical data suggest that the sulfurous sherds are Bow porcelain (London, Bowcock period, ca. 1755-1769). The origin(s) of the low-S samples remains unidentified; one compositionally resembles "gold-anchor period" (phosphatic) Chelsea porcelain (London, ca. 1756-1769) but its decoration is inconsistent with known wares produced by this factory during that era. The degree of vitrification is highly variable, particularly among the SO 3 -poor samples. The melt phase is strongly enriched in incompatible elements (Ti, Fe, Na, K). The phosphate phase [calcined bone ash (hydroxyapatite)] in poorly vitrified samples hosts minute melt blebs, but remains porous. With increasing vitrification, these melt blebs increase in size and begin to coalesce, ultimately forming ameboid patches up to ~10 mm in diameter. In the most vitrified samples, the coalesced melt "leaks" into the matrix, leaving behind a phosphate phase that lacks pores and melt and has a lower CaO/P 2 O 5 ratio (ϭ2.7, molecular proportions) than either hydroxyapatite (3.3) or b-whitlockite (3.0). The two varieties of phosphate occur in some poorly vitrified samples, suggesting the recycling of highfired wasters (as "grog") in their ceramic pastes. Melt compositions vary with contiguous mineralogy, accounting for their divergence from the ternary eutectic in the Ca 3 (PO 4 ) 2 -CaAl 2 Si 2 O 8 -SiO 2 system. The resorption of phosphate by the matrix melt virtually precludes recognition of anorthite formed by the "non-phosphate glass equation."

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Section: Discussionmentioning

confidence: 99%

Microstructures of phosphatic porcelain from sintering to vitrification: Evidence from sherds excavated in Charleston, South Carolina

Owen

Hunter²,

Jellicoe

et al. 2011

Geoarchaeology

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“…Most of the extra-terrestrial phosphates from the whitlockite group are compositionally close to merrillite, i.e., they are dry with variable amounts of Na, Fe and Mg [4][5][6]. Trace abundances of halogens in extra-terrestrial merrillite have also been reported [6,12,50].…”

Section: Phosphate Compositionmentioning

confidence: 99%

“…A comparison between the observed d hkl data and the calculated d-spacings for the merrillite according to the literature [5] is presented in Table 1. Similar to shocked apatite crystals, the bright field photomicrographs of merrillite revealed a set of irregularly spaced, planar defects in the crystals (Figure 8a,e,h), which are typical of high shock pressure.…”

Section: Figure 8 Transmission Electron Microscope (Tem) Photomicrogmentioning

confidence: 99%

“…Phosphates that occur in extra-terrestrial mafic rocks may provide information regarding water (volatiles) content in the environment leading to their formation and transformation (e.g., [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]). The magma source for Martian basalts is the Martian mantle; thus, the basaltic phosphates provide information on the Martian mantle composition as well as its evolution in the course of melting progression [11,[18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

“…The magma source for Martian basalts is the Martian mantle; thus, the basaltic phosphates provide information on the Martian mantle composition as well as its evolution in the course of melting progression [11,[18][19][20][21]. Volatile-bearing apatite (Ca 10 (PO 4 ) 6 (Cl, F, OH) 2 ), volatile-free merrillite (Ca 18 Na 2 Mg 2 (PO 4 ) 14 ) and the high-pressure phase tuite (γ-Ca 3 (PO 4 ) 2 ) are frequently observed in extra-terrestrial bodies ( [1,3,5,6,12,[22][23][24][25] and references therein). These minerals are thought to be of different origins due to their joint or separate occurrence and their chemical and structural transformation processes.…”

Section: Introductionmentioning

confidence: 99%

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Validity of the Apatite/Merrillite Relationship in Evaluating the Water Content in the Martian Mantle: Implications from Shergottite Northwest Africa (NWA) 2975

et al. 2017

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Abstract:Phosphates from the Martian shergottite NWA 2975 were used to obtain insights into the source and subsequence differentiation of the melt/melts. The crystallization of two generations of fluorapatite (F > Cl~OH and F-rich), chlorapatite and ferromerrillite-merrillite were reconstructed from TEM (Transmission Electron Microscopy) and geochemical analyses. The research results indicated that the recognized volatiles budget of the two generations of fluorapatite was related to their magmatic origin. The apatite crystals crystallized from an evolved magma during its final differentiation and degassing stage. In turn, chlorapatite replaced ferromerrillite-merrillite and was not related to, mantle-derived shergottite magma. The relationship between merrillite and apatite indicates that apatite is most probably a product of merrillite reacting with fluids. REE (rare earth elements) pattern of Cl-apatite might point to an origin associated with exogenous fluids mixed with fluids exsolved from evolved magma. The study shows that, among the three types of apatite, only the fluorapatite (F > Cl~OH) is a reliable source for assessing the degree of Martian mantle hydration. The occurrence of apatite with merrillite requires detailed recognition of their relationship. Consequently, the automatic use of apatite to assess the water content of the magma source can lead to false assumptions if the origin of the apatite is not precisely determined.

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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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The crystal chemistry of whitlockite and merrillite and the dehydrogenation of whitlockite to merrillite

Cited by 69 publications

References 12 publications

Microstructures of phosphatic porcelain from sintering to vitrification: Evidence from sherds excavated in Charleston, South Carolina

Microstructures of phosphatic porcelain from sintering to vitrification: Evidence from sherds excavated in Charleston, South Carolina

Validity of the Apatite/Merrillite Relationship in Evaluating the Water Content in the Martian Mantle: Implications from Shergottite Northwest Africa (NWA) 2975

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

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