Natural high-pressure polymorph of merrillite in the shock veins of the Suizhou meteorite

Xie, Xiande; Minitti, M. E.; Chen, Ming; Mao, H. K.; Wang, Deqiang; Shu, Jinfu; Fei, Yingwei

doi:10.1016/s0016-7037(02)00833-5

Cited by 85 publications

(68 citation statements)

References 20 publications

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“…The P-T conditions for synthesizing the CT phase are coincident with the estimation based on the high-pressure mineral assemblage of shock veins of the Suizhou meteorite (20,23,24). Both high-pressure phases are quenchable on releasing P-T to ambient conditions.…”

Section: Resultssupporting

confidence: 53%

“…Both olivine and pyroxene display moderate mosaic texture, and plagioclase was partially shock-melted and quenched to maskelynite, a plagioclase glass. The shock veins contain abundant highpressure minerals (ringwoodite, majorite, magnesiowüstite, NaAlSi 3 O 8 -hollandite, and majorite-pyrope garnet solid solution) for which the shock-produced pressure and temperature of 20-22 GPa and Ϸ2,000°C is inferred (20,(22)(23)(24). …”

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confidence: 99%

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Natural occurrence and synthesis of two new postspinel polymorphs of chromite

Chen

Shu

Mao

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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112

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A high-pressure polymorph of chromite, the first natural sample with the calcium ferrite structure, has been discovered in the shock veins of the Suizhou meteorite. Synchrotron x-ray diffraction analyses reveal an orthorhombic CaFe 2O4-type (CF) structure. The unit-cell parameters are a ‫؍‬ 8.954(7) Å, b ‫؍‬ 2.986(2) Å, c ‫؍‬ 9.891(7) Å, V ‫؍‬ 264.5(4) Å 3 (Z ‫؍‬ 4) with space group Pnma. The new phase has a density of 5.62 g͞cm 3 , which is 9.4% denser than chromitespinel. We performed laser-heated diamond anvil cell experiments to establish that chromite-spinel transforms to CF at 12.5 GPa and then to the recently discovered CaTi 2O4-type (CT) structure above 20 GPa. With the ubiquitous presence of chromite, the CF and CT phases may be among the important index minerals for natural transition sequence and pressure and temperature conditions in mantle rocks, shock-metamorphosed terrestrial rocks, and meteorites. F orty years ago, in search of denser polymorphs of the then newly discovered silicate spinel (ringwoodite) and modified spinel (wadsleyite) that are stable at the pressure and temperature (P-T) conditions of the Earth's transition zone, Ringwood (1, 2) proposed orthorhombic CaFe 2 O 4 -type (CF) and CaTi 2 O 4 -type (CT) structures as the top candidates for ''postspinel'' transitions in the Earth's mantle (Fig. 1). Although ferromagnesian silicate spinels were later found to break down to simple oxides (3) or stishovite plus perovskite (4), several postspinel oxides convert to a single phase with the CF or CT structure (1, 2, 5-12). Neither dense postspinel polymorphs nor silicate perovskites, however, have been discovered in nature and confirmed as new minerals. Many natural high-pressure minerals presumably predominating in the Earth's mantle have been found mainly in the shock-metamorphosed meteorites, which include ringwoodite, wadsleyite, silicate ilmenite, magnesiowüs-tite, (Na,K)AlSi 3 O 8 -hollandite, and poststishovite polymorphs (13-19). Special P-T conditions developed in the impacted meteorites, for instance, a long duration of high-pressure and -temperature up to several seconds and quenching under pressure, play an important role in the formation and preservation of high-pressure phases (16). It makes the naturally shockmetamorphosed meteorites a window for discovery of new high-pressure minerals and for investigation of the constituents in the deep Earth. Preliminary examination of the Suizhou meteorite has recently revealed a shock-metamorphosed CT polymorph of chromite composition (20). In this article, we report the identification of a previously uncharacterized CF polymorph of chromite in the same meteorite. High P-T experiments demonstrate that both CF and CT are indeed quenchable polymorphs of chromite formed above 12.5 and 20 GPa, respectively.The Suizhou meteorite is a moderately shock-metamorphosed L6-chondrite, and a shock stage S5 was estimated for the meteorite according to the classification of shock metamorphism (21). The meteorite contains shock-produced melt veins ranging...

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Section: Resultssupporting

confidence: 53%

mentioning

confidence: 99%

Natural occurrence and synthesis of two new postspinel polymorphs of chromite

Chen

Shu

Mao

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

112

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“…These bands are associated with the n 1 symmetric stretching mode of (PO 4 ) 3-ions. [14][15][16] In some fragments such as in the Nuevo Mercurio-c case, we detected by MRS both Ca-phosphate phases, anhydrous merrillite and hydrous chlorapatite-hydroxyapatite associated with the hydrated or metasomatized areas. The panchromatic CL plot shows in pale grey-tones the cathodoluminescent minerals plagioclase (albite-oligoclase) and merrillite (Fig.…”

Section: Resultsmentioning

confidence: 99%

Spectra Luminescence of Extraterrestrial Calcium Phosphates in Mexican Chondrites

Aldave

Guinea

Tormo

2011

Spectroscopy Letters

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“…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%

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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Natural high-pressure polymorph of merrillite in the shock veins of the Suizhou meteorite

Cited by 85 publications

References 20 publications

Natural occurrence and synthesis of two new postspinel polymorphs of chromite

Natural occurrence and synthesis of two new postspinel polymorphs of chromite

Spectra Luminescence of Extraterrestrial Calcium Phosphates in Mexican Chondrites

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

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