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Raman spectroscopy of high-pressure phases in shocked L6 chondrite NWA 5011

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1. Title Title of document Raman spectroscopy of high-pressure phases in shocked L6 chondrite NWA 5011
2. Creator Author's name, affiliation, country K. D. Litasov; V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences; Novosibirsk State University ; Russian Federation
2. Creator Author's name, affiliation, country D. D. Badyukov; V.I. Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences ; Russian Federation
3. Subject Discipline(s)
3. Subject Keyword(s) meteorite; chondrite; ringwoodite; majorite; akimotoite; bridgmanite; shock metamorphism
4. Description Abstract

In the paper we present results of studies of thick shock melt veins in NWA 5011 L6 chondrite. The veins contain a wide variety of high-pressure phases that correspond to contrast values of pressure-temperature parameters on equilibrium phase diagrams. Olivine was transformed to ringwoodite and wadsleyte, orthopyroxene to majorite, akimotoite, and bridgmanite glass, maskelenite is converted to jadeite (+SiO2) and lingunite, apatite to tuite, and chromite to the phase with the calcium ferrite (mCF-FeCr2O4) structure. ) The peak PT shock parameters for NWA 5011 seem highest among the ones for other shocked chondrites according to wide occurrence of lingunite and bridgmanite glass and are considerable higher than 25 GPa and 2500 K. Akimotoite crystals in a quenched matrix of shock melt veins were found for the first time. Probably, they initially crystallized as bridgmanite, since akimotoite is not a liquidus phase in related systems. Plagioclase-chromite aggregates have been established, which characterize the late stages of the shock process and are formed during successive crystallization from isolated pockets of the impact melt.
5. Publisher Organizing agency, location The Russian Academy of Sciences
6. Contributor Sponsor(s) Russian Foundation of Basic Research (Array)
Programme of the Bureau of the RAS (Array)
7. Date (DD-MM-YYYY) 03.09.2019
8. Type Status & genre Peer-reviewed Article
8. Type Type Research Article
9. Format File format
10. Identifier Uniform Resource Identifier https://journals.eco-vector.com/0016-7525/article/view/15883
10. Identifier Digital Object Identifier (DOI) 10.31857/S0016-7525648848-858
10. Identifier Digital Object Identifier (DOI) (PDF (Rus)) 10.31857/S0016-7525648848-858-12503
11. Source Title; vol., no. (year) Геохимия; Vol 64, No 8 (2019)
12. Language English=en ru
13. Relation Supp. Files Fig. 1. Images of shock-melt veins (SMV) in NWA 5011 chondrite in reflected electrons: (a) fine-crystalline core matrix, consisting mainly of majorite and ringwoodite; (b) a fragment of a core with fragments of high-pressure phases; (c) chondrule at the core contact with minerals completely converted to ringwoodite, lingunite and akimotoite with bridgmanite glass. Rgt - ringwood, Lin - lingunite, Ol - olivine, BrdG - bridgmanite (glass), Opx - orthopyroxene. The scale is 100 microns. (667KB) doi: 10.31857/S0016-7525648848-858-14270
Fig. 2. Fragments of shock-melt veins (SMV) in reflected electrons: (a, b) tempered crystals of ringwoodite (Rgt) and akimotoite (Akm) with patches of bridgmanite glass (BrdG); (c, d) orthopyroxene grains recrystallized into akimotoit-bridgmanite aggregate. Lin is lingunite. (591KB) doi: 10.31857/S0016-7525648848-858-14271
Fig. 3. (a) Remelted areas of maskeline (Msk) with abundant inclusions of fine-grained chromite (Chr); (b) the same in contact with orthopyroxene (Opx) grains containing chromite lamellas; (c) fragments of tuite (Tu) and (d) unchanged phosphates - apatite (Ap) and merrillite (Mer) in shock-melt veins (SMV). Rgt - ringwood, Maj - major. (729KB) doi: 10.31857/S0016-7525648848-858-14272
Fig. 4. Raman spectra of olivine and ringwood. The ringwoodite spectrum contains weak wadsleite lines at 712 and 920 cm-1. (125KB) doi: 10.31857/S0016-7525648848-858-14273
Fig. 5. Raman spectra of apopyroxene aggregates. BrdG - glass bridgmanite composition. The dashed lines show the main peaks of orthopyroxene (Opx) (1012 cm-1), majorite (Maj) (930 cm-1) and akimotoite (Akm) (799 cm-1). (181KB) doi: 10.31857/S0016-7525648848-858-14274
Fig. 6. Raman spectra of high pressure phases by plagioclase. Unidentified lines are shown in italics. (139KB) doi: 10.31857/S0016-7525648848-858-14275
Fig. 7. Raman spectra of chromite from the matrix of chondrite (X) and inclusions in shock-melt veins (A and B). Spectrum B probably corresponds to the high-pressure phase mCF, the spectra of which are given for comparison according to the data (Rout et al., 2017). The gray dashed line shows the position of the xiite main line at 605 cm-1 (Chen et al., 2008). (134KB) doi: 10.31857/S0016-7525648848-858-14276
Fig. 8. Raman spectra of phosphates (a). The right side shows the position of the main absorption lines of the phosphate ion at 900-1050 cm-1 on an enlarged scale (b). Italic lines of apatite are shown. (152KB) doi: 10.31857/S0016-7525648848-858-14277
Fig. 9. PT-conditions for the formation of high pressure phases according to static experiments. Numbers show the main associations in chondrite NWA 5011: 1 - majorit-bridgmanit; 2 - akimotoit-bridgmanite; 3 - major-akimotoit; 4 - lingunitis; 5 - olivine-ringwoodite and ringwoodite-wadsleite; 6 - tuit; 7 - mCF chromite. (a) solid black lines — solidus, liquidus, and ringwoodite transition (Rgt) = bridgmanite (Brd) + ferropericlase (Fper) for peridotite KLB-1 (Herzberg and Zhang, 1996); black dotted lines are the phase boundaries Ol / (Ol + Rgt) and (Rgt + Wds) / Rgt for the composition Fo75 (Akaogi et al., 1989); gray solid lines are the stability fields of majorite (Maj) and akimotoite (Akm) in the MgSiO3 system (Gasparik, 2003); black dashed lines are the phase boundaries in the NaAlSi3O8 system (Bell, Roseboom Jr, 1969; Liu, 2006; Zhou et al., 2017). (b) black solid and dashed lines are the stability boundaries of F- and OH-apatite, respectively (Murayama et al., 1986); black dotted lines are the stability fields of apatite and tuite in P-containing peridotite (Konzett et al., 2012); solid gray lines are the phase boundaries in the FeCr2O4 system (Ishii et al., 2014); gray bold letters indicate the synthesis parameters of chromite phases CF, CT (Chen et al., 2003) and mCF (Rout et al., 2017); the gray dashed line — the coesite (Coe) –stishite (Sti) boundary in the SiO2 system (Zhang et al., 1996). Ab is albite; Jd is jadeite; Lin is lingunite; Ca-Prv — Ca-perovskite; Esk - escolite; chromite with the structure of calcium titanate (CT), calcium ferrite and its modified analogue (CF and mCF); mLd - Fe2Cr2O5 with a modified ludwigite structure.   (218KB) doi: 10.31857/S0016-7525648848-858-14278
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