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MINERALOGY of INCLUSION with SILICATE-NATROPHOSPHATE IMMISCIBILITY, METEORITE ELGA (IIE) Victor V

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MINERALOGY of INCLUSION with SILICATE-NATROPHOSPHATE IMMISCIBILITY, METEORITE ELGA (IIE) Victor V MINERALOGY OF INCLUSION WITH SILICATE-NATROPHOSPHATE IMMISCIBILITY, METEORITE ELGA (IIE) Victor V. Sharygin1,2,3 1V.S.Sobolev Institute of Geology and Mineralogy, 3 Akad. Koptyuga pr., Novosibirsk, 630090, Russia, E-mail: [email protected], 2Novosibirsk State University, 2 Pirogov str., Novosibirsk, 630090, Russia; 3ExtraTerra Consortium, Institute of Physics and Technology, Ural Federal University, 19 Mira str., Ekaterinburg 620002, Russia. Iron meteorite Elga (group IIE) from Yakutia is a fine-grained octahedrite with silicate inclusions (up to 15 vol.%) and with clear features of local Different types of inclusions in metal, meteorite Elga Fragment of the Elga meteorite shock metamorphism melting (Plyashkevich, 1962; Kvasha et al., 1974; Osadchii et al., 1981; Khisina et al., 2017). The inclusions are rounded or Elga-3 Elga-11 Tro Elga-8 oval; sizes – 1-5 mm, sometimes up to 10-15 mm. Their mineral composition strongly varies. Most inclusions are gray-green and consist of glass (45-70%), diopside (25-50%) and enstatite (1-5%), rarely phosphates (fluorapatite, merrillite, panethite), olivine, chromite and rutile. Spheric milky-white inclusions contain glass or quartz-feldspathic aggregate with minimal mafic silicates. Schreibersite and troilite commonly occurs Gl+Cpx Tro Cpx around all inclusions. Inclusions with equal content of silicates and troilite as well as troilite-schreibersite segregations were also observed in Fe- Gl+Cpx Gl+Cpx Sch Ni-metal. Sch List of mineral phases found in the Elga meteorite Sch Tro Mineral Formula Mineral Formula Mineral Formula Mineral Formula Sch 2 Sch Graphite sp -C Czochralskiite Na4Ca3Mg(PO4)4 Eskolaite Cr2O3 K-feldspar KAlSi3O8 Tro Kamacite α-(Fe,Ni) Brianite Na2CaMg(PO4)2 Quartz SiO2 Glass > 70 wt.% SiO2 Taenite γ-(Fe,Ni) Maricite NaFe(PO4) Goethite α-FeOOH Chlorite Fe5Al[AlSi3O10](OH)8 Tetrataenite FeNi Chladniite Na Ca(Mg,Fe) (PO ) Forsterite (Mg,Fe) SiO Serpentine Fe Si O (OH) 2 7 4 6 2 4 3 2 5 4 Elga-1 Elga-5 Elga-6 Kfs Schreibersite (Fe,Ni)3P Na-Fe-Mg-phosphate Na2(Fe,Mn)(Mg,Ca)(PO4)2 Enstatite (Mg,Fe)2Si2O6 Sch Kfs 2+ Melliniite (Fe,Ni)4P Na-Fe-H2O-phosphate Na-rich Fe 3(PO4)2•8H2O Diopside Ca(Mg,Fe)Si2O6 Opx Troilite FeS Siderite (Fe,Ni)(CO3) Kosmochlor NaCrSi2O6 Pentlandite (Fe,Ni) S Rutile TiO Ti-clinopyroxene Na(Mg,Fe) Ti Si O Gl 9 8 2 0.5 0.5 2 6 Gl Gl 3+ Fluorapatite Ca5(PO4)3F Chromite FeCr2O4 Ferri-obertiite NaNa2Mg3Fe Ti[Si8O22]O2 Merrillite Ca NaMg(PO ) Magnetite FeFe O «Ferro-obertiite» NaNa Mg Fe2+Ti [Si O ]O Cpx 9 4 7 2 4 2 2.5 1.5 8 22 2 Cpx Tuite Ca (PO ) Ilmenite FeTiO Aenigmatite Na (Fe2+,Mg) TiSi O O Pan+Mer Sch 1cm 3 4 2 3 2 5 6 18 2 Sch Panethite (Na,Ca,K)2(Mg,Fe)2(PO4)2 Armalkolite (Mg,Fe)Ti2O5 Albite NaAlSi3O8 Data from: Plyashkevich, 1962; Kvasha et al., 1974; Osadchii et al., 1981; Teplyakova et al., 2012; Khisina et al., 2017; Litasov, Podgornykh, 2017; Sharygin, 2017. Silicate inclusion with silicate-natrophosphate immiscibility in metal BSE Si Al Ti Cr Elga13-decay Elga12-decay Elga-4 Sch Km Elga-4 Fe Ni Mg Ca Na Tro Ab+Or+Qu PG K S P O False Quenched texture of Fe-Ni-P-S in metal (kamacite + schreibersite + troilite) Sch Tro Impact melting event 0.5 mm 0.5 cm Silicate part of inclusion Natrophosphate part of inclusion BSE Si Al Ti Cr BSE Ksm Tro Si Al Ti Cr Opx NFP Ab+Or+Qu Ab+Or+Qu Obr Bri Obr Obr Bri Czo Obr NFP Ab+Or+Qu Sch Obr Ab+Or Aen Pn Qu Ksm Ab+Or+Qu +Qu Opx Opx Sch Kmc Bri Chl Opx Bri Qu Aen Opx Obr NFP Czo Opx Sch Ab+Or Obr Chl Tro Fe Ni Mn Mg Ca Opx Esk Sch Obr Fe Ni Mn Mg Ca Kmc Czo Pn Pn Composition of Ti-oxyamphibole varies: Opx 2+ 3+ 3+ from (K0.1Na0.9)(Na1.6Ca0.4)(Mg3.0Fe 0.45Fe 0.4Ti1.15)[Fe 0.15Al0.05Si7.8O22]O1.9F0.1 2+ 3+ 3+ to (K0.15Na0.85)(Na1.8Ca02)(Mg2.3Fe 1.15Fe 0.05Ti1.5)[Fe 0.2Al0.1Si7.7O22]O1.95F0.05 Na K O P False 15 µm Ab+Or+Qu Ab+Or Na K S P False Gl NFP Aen Ksm Ab Czo+Bri Qu Ksm NFP NFP Ksm Ab+Or+Qu Chl Qu Silicate part of the studied immiscible inclusion is free in silicate glass; now it is fine-grained Obr Bri Bri Czo aggregate of feldspars and quartz.The relationships of feldspars indicate solid decay of initially Opx Ab+Or+Qu homogenous K-Na-feldspar into albite and K-feldspar with temperature decreasing. Mafic Obr 5 µm 30 µm Ab+Or 10 µm Individual isolations of phosphates in outer part s of the inclusion minerals in silicate part are very specific: dominant phase is an obertiite–group oxyamphibole, Mar 2+ Kmc “ferro-obertiite” NaNa2Mg2.5Fe Ti1.5[Si8O22]O2; minor phases are aenigmatite 2+ Tro Na2(Fe ,Mg)5TiSi6O18O2, clinopyroxene of the diopside Ca(Mg,Fe)Si2O6 – kosmochlor Symbols: Kmc – kamacite; Tro – troilite; Sch – schreibersite; Ab+Or+Qu (Gl) – Bri Opx Opx NaCrSi2O6 - Na(Mg,Fe)0.5Ti0.5Si2O6 series, enstatite and Fe-Zn-eskolaite. Three last minerals are completely crystallized aggregate of albite + K-feldspar + quartz (former glass); commonly confined to the boundary between silicate and natrophosphate parts. The alteration Pn – pentlandite; Opx – enstatite; Obr – “ferro-obertiite”; Aen – aenigmatite; 10 µm phases are represented by Fe-chlorite and hydrated phosphate close to vivianite Sch Ksm – clinopyroxene with composition diopside-kosmochlor - Sch 2+ Obr Fe 3(PO4)2•8H2O and with Na2O (2.3-3.3 wt.%). Na(Mg,Fe)0.5Ti0.5Si2O6; Czo – czochralskiite; Bri – brianite; Mar - maricite; Bri Opx Czo Ab+Or+Qu NFP – Na-Fe-H2O phosphate; Chl – Fe-chlorite; Esk – eskolaite; PG – Chl Ab+Or+Qu natrophosphate globule. Obr Bri Pn Czo Ab+Or+Qu Czo Chemical composition (WDS, wt.%) of mafic minerals from silicate part of the inclusion Czo Obr Минерал n SiO2 TiO2 Cr2O3 V2O3 Al2O3 FeO MnO MgO CaO Na2O K2O F Sum References Czo “Ferro-obertiite” 20 53.51 11.65 0.18 0.01 0.38 8.58 0.43 12.96 2.22 8.99 0.74 0.27 99.91 Plyashkevich L.N. 1962. Meteoritica 22:51-60. Chemical composition (EDS+WDS,wt.%) of phosphates in natrophosphate part Kvasha L.G. et al. 1974. Meteoritica 33:143-147. Aenigmatite 5 46.17 10.09 0.23 0.00 0.09 20.70 0.56 14.17 0.01 8.76 0.00 0.00 100.78 Ksm Osadchii E.G. et al. 1981. LPS 12:1049-1068. Mineral n SiO2 P2O5 TiO2 FeO MnO MgO CaO SrO Na2O Sum Enstatite 6 55.71 0.28 0.35 0.00 0.07 11.25 0.75 31.20 0.43 0.10 0.00 0.00 100.13 Khisina N.R. et al. 2017. Geochem. Inter. 55:317-329. Czochralskiite 27 0.11 44.95 0.02 3.44 0.64 4.91 26.03 0.27 19.58 99.94 Bri Kosmochlor 3 53.21 10.43 11.21 0.10 0.93 2.92 0.16 4.36 3.56 12.63 0.00 0.00 99.52 Litasov K.D., Podgornykh N.M. 2017. J. Raman Spectr. 48:1518-1527. 18 0.07 46.88 0.00 3.48 0.49 10.92 17.49 0.52 20.00 99.85 Kosmochlor 3 54.22 3.96 11.36 0.00 0.40 3.65 0.18 8.52 9.91 7.79 0.00 0.00 99.98 Brianite Sharygin V.V. 2017. V conference “Meteorites, 2 µm Kosmochlor 4 53.85 3.89 16.94 0.00 0.38 2.60 0.21 5.50 6.49 10.08 0.00 0.00 99.93 Asteroids. Comets.”, Ekaterinburg, pp. 153-157. Maricite 13 0.09 41.96 0.01 26.66 5.89 5.52 0.77 0.21 18.72 99.82 .
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