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Article

Mineralogy of Silicate-Natrophosphate Immiscible Inclusion in Elga IIE Iron Meteorite

1
V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the RAS, 3 Acad. Koptyuga pr., Novosibirsk 630090, Russia
2
ExtraTerra Consortium, Institute of Physics and Technology, Ural Federal University, 19 Mira str., Ekaterinburg 620002, Russia
The paper was presented at the 81st Annual Meeting of the Meteoritical Society in Moscow, Russia, 22–27 July 2018.
Minerals 2020, 10(5), 437; https://doi.org/10.3390/min10050437
Received: 7 April 2020 / Revised: 21 April 2020 / Accepted: 11 May 2020 / Published: 13 May 2020
(This article belongs to the Special Issue Mineralogy of Meteorites)
Rare type of silicate inclusions found in the Elga iron meteorite (group IIE) has a very specific mineral composition and shows silicate (≈90%)–natrophosphate (≈10%) liquid immiscibility due to meniscus-like isolation of Na-Ca-Mg-Fe phosphates. The 3 mm wide immiscible inclusion has been first studied in detail using optical microscopy, scanning electron microscopy, electron microprobe analysis and Raman spectroscopy. The silicate part of the inclusion contains fine-grained quartz-feldspar aggregate and mafic minerals. The relationships of feldspars indicate solid decay of initially homogenous K-Na-feldspar into albite and K-feldspar with decreasing of temperature. Some mafic minerals in the silicate part are exotic in composition: the dominant phase is an obertiite-subgroup oxyamphibole (amphibole supergroup), varying from ferri-obertiite NaNa2Mg3Fe3+Ti[Si8O22]O2 to hypothetical NaNa2Mg3Fe2+0.5Ti1.5[Si8O22]O2; minor phases are the aenigmatite-subgroup mineral (sapphirine supergroup) with composition close to median value of the Na2Fe2+5TiSi6O18O2-Na2Mg5TiSi6O18O2 join, orthopyroxene (enstatite), clinopyroxene of the diopside Ca(Mg,Fe)Si2O6–kosmochlor NaCrSi2O6-Na(Mg,Fe)0.5Ti0.5Si2O6 series and chromite. The alteration phases are represented by Fe-dominant chlorite, goethite and hydrated Na2O-rich (2.3–3.3 wt.%) Fe-phosphate close to vivianite. Natrophosphate part consists of aggregate of three orthophosphates (brianite, czochralskiite, marićite) and minor Na-Cr-Ti-clinopyroxene, pentlandite, rarely taenite. Czochralskiite Na4Ca3Mg(PO4)4 is rich in FeO (2.3–5.1 wt.%) and MnO (0.4–1.5 wt.%). Brianite Na2CaMg(PO4)2 contains FeO (3.0–4.3 wt.%) and MnO (0.3–0.7 wt.%) and marićite NaFe(PO4) bears MnO (5.5–6.2 wt.%), MgO (5.3–6.2 wt.%) and CaO (0.5–1.5 wt.%). The contact between immiscible parts is decorated by enstatite zone in the silicate part and diopside–kosmochlor clinopyroxene zone in the natrophosphate ones. The mineralogy of the studied immiscible inclusion outlines three potentially new mineral species, which were first identified in meteorites: obertiite–related oxyamphibole NaNa2Mg3Fe2+0.5Ti1.5[Si8O22]O2, Mg-analog of aenigmatite Na2Mg5TiSi6O18O2 and Na-Ti-rich clinopyroxene Na(Mg,Fe)0.5Ti0.5Si2O6. View Full-Text
Keywords: silicate-natrophosphate immiscibility; obertiite; aenigmatite; kosmochlor; brianite; czochralskiite; marićite; Elga meteorite; IIE iron; Yakutia silicate-natrophosphate immiscibility; obertiite; aenigmatite; kosmochlor; brianite; czochralskiite; marićite; Elga meteorite; IIE iron; Yakutia
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MDPI and ACS Style

Sharygin, V.V. Mineralogy of Silicate-Natrophosphate Immiscible Inclusion in Elga IIE Iron Meteorite. Minerals 2020, 10, 437. https://doi.org/10.3390/min10050437

AMA Style

Sharygin VV. Mineralogy of Silicate-Natrophosphate Immiscible Inclusion in Elga IIE Iron Meteorite. Minerals. 2020; 10(5):437. https://doi.org/10.3390/min10050437

Chicago/Turabian Style

Sharygin, Victor V. 2020. "Mineralogy of Silicate-Natrophosphate Immiscible Inclusion in Elga IIE Iron Meteorite" Minerals 10, no. 5: 437. https://doi.org/10.3390/min10050437

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