ISSN 1028-334X, Doklady Earth Sciences, 2016, Vol. 471, Part 2, pp. 1273–1276. © Pleiades Publishing, Ltd., 2016. Original Russian Text © Yu.V. Erokhin, V.A. Koroteev, V.V. Khiller, E.V. Burlakov, K.S. Ivanov, D.A. Kleimenov, 2016, published in Doklady Akademii Nauk, 2016, Vol. 471, No. 5, pp. 579–582.
GEOCHEMISTRY
The Ozernoye Meteorite: New Data on Mineralogy Yu. V. Erokhina*, Academician V. A. Koroteeva, V. V. Khiller a, E. V. Burlakovb, K. S. Ivanova, and D. A. Kleimenovb Received February 24, 2016
Abstract—New data on the mineral composition of the Ozernoye meteorite, found in the Kurgan region in 1983, are presented. It has been found that that the meteorite’s matter is composed of olivine (chrysolite), orthopyroxene (bronzite), clinopyroxene (augite), maskelynite, chromite, ilmenite, metals Fe and Ni (kamasite, taenite), sulfides (troilite, pentlandite), chlorapatite, and merrillite. Augite, taenite, pentlandite, and merrillite were identified in the Ozernoye meteorite for the first time. The chemical compositions are given for all these minerals. The meteorite itself is an ordinary chondrite stone belonging to petrological type L5. DOI: 10.1134/S1028334X16120096
A shepherd, N.L. Hismatullin, found the Ozernoye meteorite in 1983, 4 km north of the Ozernoye site of Zauralskii Farm in Almenevskii District of the Kurgan region (about 100 km southwest of Kurgan) [1, 2]. In 1985, he also found a second piece of identical chondrite near the village of Ozernoye in the same area. The total mass of these two fragments is about 3.66 kg. Both fragments were transferred for study to the Ural Commission on Meteorites: currently a small fragment from the first piece is stored in the Ural Geological Museum. This specimen has been studied. Both fragments of the meteorite have been assigned to a single chondrite “Ozernoye” [3], while Ural researcher Loginov has suggested that they are different from each other and proposed to call them “Ozernoye-I” and “Ozernoye-II” [1, 2]. In this case, we studied a sample from the Ozernoye-I chondrite. Simultaneously with discovery of the second piece of the Ozernoye chondrite, a larger fragment of a meteorite weighing 22.4 kg (also collected close to the village of Ozernoye) was discovered, but for some reason it was not handed over to professionals and soon its existence was forgotten. In 2007, this piece appeared in Kurgan and in a short time (2008) it had been sold to the well-known meteorite collector S.P. Vasil’ev (resident of Prague) and taken to the Czech Republic [4]. This fragment of the meteorite is not available for study (at least to Russian scientists). The studied meteorite is defined as an ordinary chondrite of class L5 (sometimes LL5) [1, 2] or L6 [3]. a Institute
of Geology and Geochemistry, Ural Branch, Russian Academy of Sciences, Yekaterinburg, Russia b Ural State Mining University, Yekaterinburg, Russia *e-mail:
[email protected]
It was subjected to weathering, and thus acquired a brown color (inside and outside). Its surface in some places preserves melting zones. The mineral composition is the following: olivine, orthopyroxene, plagioclase, maskelynite (feldspar glass), chromite, ilmenite, phosphate (apatite, whitlockite) troilite, kamasite, schreibersite, and secondary hypergene minerals (goethite and hydrogoethite) [1, 2, 5]. Recently, we conducted an inspection of Urals meteorites, which resulted in acquiring new data on the mineralogy of the Ozernoye chondrite substantially complementing previously published data. Olivine in the chondrite matrix is the main rockforming mineral composing chondrules and fractured grains up to 1 mm in size. It is characterized by a steady chemical composition (Table 1, analyses 1–3) and relates to forsterite with 26–27% of fayalite minal. Orthopyroxene occurring in chondrules (up to 2 mm in diameter) and in the rock matrix (0.5 mm grain) corresponds to 22% of enstatite ferrosilite minal (Table 1, analyses 4–6). Clinopyroxene occurs much less frequently; its grains up to 25 mm in size are associated with clusters of enstatite. It has a stable composition (Table 1, analyses 7–9). All analyzes fall into the augite field (En46–47Wo45Fs8–9) almost at the boundary with the diopside field. We did not found any plagioclase, instead only maskelynite was revealed (Table 1, analyses 10–12), which fills interstices between grains of the rock-forming minerals. Chrome–spinel is present throughout the matrix of the meteorite in the form of anhedral grains up to 200 μm in size. According to its microprobe analysis (Table 1, analyses 13–15), it relates to chromite with minals of hercynite (13%), ulvospinel (9%), and magnesium chromite (17%). The chrome–spinellides consistently contain an admixture of zinc (ZnO up to
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Table 1. Chemical composition (wt.%), silicates and oxides of the Ozernoye meteorite No.
SiO2
TiO2
Al2O3
Cr2O3
NiO
FeO
MnO
MgO
CaO
Na2O
K2O
Sum
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
38.07 37.88 37.63 55.09 55.21 55.17 53.15 53.41 53.25 65.40 65.67 65.35 – – – – 0.03 0.02
– – 0.02 0.15 0.22 0.19 0.56 0.45 0.49 0.08 0.05 0.02 2.13 3.38 3.37 28.57 55.21 55.41
– – – 0.17 0.18 0.18 0.55 0.54 0.54 22.55 22.71 22.78 6.35 5.41 5.60 2.60 0.04 0.05
0.08 0.04 0.02 0.10 0.19 0.25 0.95 0.91 0.97 0.03 0.10 0.38 57.22 57.48 56.69 27.83 0.40 0.42
0.06 – 0.06 – 0.02 0.01 0.05 0.01 0.01 – 0.02 0.04 0.04 – 0.01 – 0.01 –
23.56 23.98 24.20 14.35 14.52 14.60 5.50 5.23 5.63 0.35 0.62 0.42 29.59 29.33 29.57 32.58 38.71 38.08
0.44 0.50 0.44 0.46 0.49 0.48 0.20 0.27 0.20 0.01 – – 0.37 0.45 0.36 0.65 0.86 0.95
37.31 37.26 37.14 27.95 27.80 27.79 16.01 16.16 16.06 – 0.03 0.06 2.69 3.17 2.86 4.40 5.61 5.53
0.04 0.02 0.02 0.80 1.08 1.13 21.54 21.73 21.74 2.46 2.42 2.65 0.01 – – 0.01 0.03 0.03
– – 0.01 0.02 0.02 0.06 0.59 0.60 0.62 3.40 2.07 2.11 0.02 0.01 0.04 0.02 – 0.02
– 0.01 0.02 – – – 0.01 0.01 0.02 0.93 1.32 1.37 0.01 – – 0.01 – –
99.56 99.69 99.56 99.09 99.73 99.86 99.11 99.32 99.53 95.21 95.01 95.18 98.43 99.23 98.50 96.67 100.90 100.51
This and subsequent analyses were performed using Cameca SX 100 microprobe at the Institute of Geology and Geochemistry, Ural Branch, Russian Academy of Sciences; 1–3, olivine, 4–6, orthopyroxene; 7–9, clinopyroxene; 10–12, maskelynite; 13–15, chromite; 16, spinel; 17–18, ilmenite.
0.3 wt %). Occasionally at the edge of chromite sections, small isometric grains (not more than 20– 30 μm) of spinels of unusual composition, rich in Ti, Cr, and Fe have been noted (Table 1, analyses 16). It is not correlated to any known composition, and therefore, we believe we have found a new, previously
Apatite is dispersed across the entire chondrite matrix and composes anhedral grains up to 200 μm across (Fig. 1). This mineral corresponds to chlorapatite (Table 2, analyses 1–5): crystallochemical calculations demonstrate variation in the anionic group from (Cl0.43F0.29OH0.28) to (Cl0.60F0.26OH0.14). In general, the phosphate by its chemical composition is comparable with apatite from chondrites of the L-type [6]. Earlier study of the Ozernoye meteorite [5] reported hydroxyapatite along with chlorapatite, but our study did not confirm this claim.
Gth Opx
Opx
Ap Msk
Tr
unknown, mineral. Study of it will continue. Ilmenite forms anhedral grains up to 100 μm in size. According to microprobe analysis (Table 1, analyses 17, 18) it has a uniform composition and relates to ilmenite containing minals of geikielite (20%) and pyrophanite (2%).
Ol 100 µm
Matrix of the Ozernoye chondrite. Photo of scattered electrons, Cameca SX 100. Ol, olivine; Opx, orthopyroxene; Msk, maskelynite; Tr, troilite; Ap, chlorapatite, Gth, goethite.
Merrillite also forms anhedral grains up to 250 μm in size dispersed across the rock matrix, but does not gravitate to apatite. It is characterized by a steady composition (Table 2, analyses 6–10) and reliably defined as merrillite. In general, this phosphate is often found in ordinary stone chondrites and is characterized by approximately the same composition [7], etc. Earlier study of the Ozernoye meteorite [5], etc. reported a find of whitlockite, but our study did not confirm this claim. Apparently, merrillite was mistaken for whitlockite, as their compositions are somewhat similar. DOKLADY EARTH SCIENCES
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THE OZERNOYE METEORITE
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Table 2. Chemical composition (wt %) of phosphate from the Ozernoye meteorite No
SO3
P2O5
SiO2
MgO
1 2 3 4 5
0.05 0.04 – 0.01 0.08
41.47 42.38 42.38 42.45 42.16
– – – – –
– – – – –
6 7 8 9 10
– – – – –
45.91 44.24 45.26 46.07 45.88
0.05 0.08 0.12 0.01 0.04
3.41 3.07 3.38 3.27 3.32
FeO Chlorapatite – – – – – Merrillite 0.96 0.87 0.93 0.85 0.67
The presence of merrillite in the chondrite indicates a low content of phosphorus in the surrounding metals, and, on the contrary, its absence in the rock presumes the presence of schreibersite or other phosphides of iron [8]. Metallic Fe and Ni in the Ozernoye meteorite compose rounded or, less often, irregular grains up to 50 μm in size, dispersed throughout the matrix of the chondrite. Metal grains are presented by kamasite and taenite. They occur separately, with kamasite dominating. It is characterized by low contents of Ni—6– 16 wt % (Table 3, analyses 1–4), while taenite has, respectively, higher Ni at 22–35 wt % (Table 3, analyses 5–8). The metals contain an admixture of Co and Cr with the total absence of P. Troilite composes individual grains up to 0.5 mm and clusters. Quantitatively, it sharply predominates over metals. It is characterized by a steady chemical composition and contains no impurities (Table 3, analyses 9–12). Its marginal parts demonstrate increased Ni and Co contents up to formation of pentlandite rims (Table 3, analyses 13, 14). By its composition the mineral is referred to the ferriferous type and to pentlandite proper (classification after [9]); it contains a significant admixture of Co (up to 2.4 wt %) and Cu (up to 1 wt %). The entire chondrite matrix is “sectioned” by a fine goethite network, which, apparently, similarly to the Chelyabinsk [10] and Kunashak meteorites [11], previously represented troilite veinlets. Apart from this, goethite fills larger later fractures, forms clusters after ore minerals, and is characterized by a high content of Ni (NiO up to 9 wt %). In the classification chart of the iron content in olivine and orthopyroxene for stone chondrites [12], the Ozernoye meteorite is located on the border of fields of the L- and LL-types. Taking into account the average concentration of Co in kamasite (0.5–0.8 wt %), DOKLADY EARTH SCIENCES
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CaO
Na2O
Cl
F
Sum
53.55 54.73 54.57 54.66 54.27
– – – – –
4.09 2.93 2.91 2.96 3.09
0.96 0.97 1.04 0.98 0.84
100.12 101.06 100.90 101.05 100.44
47.57 48.07 47.40 47.61 47.71
2.83 2.52 2.86 2.76 2.80
0.15 0.57 0.08 0.37 0.24
0.07 0.09 0.04 0.04 0.06
100.95 99.52 100.08 100.98 100.73
the meteorite can be attributed to the L-type (classification [13]). Chondrules in the rock matrix are seen, but not very clearly. According to the classification of ordinary chondrites [14], the petrological type of the meteorite is defined as L5 (with less distinct chondrules). Apparently, the Ozernoye meteorite had a heterogeneous structure, as the chondrite fragments studied by us almost completely correspond to the descriptions of some authors [1, 2] and are a bit different from another [3]. Table 3. The chemical composition (wt %) of metals and sulfides from the Ozernoye meteorite No.
Cr
Fe
1 2 3 4
0.46 0.55 0.79 1.00
92.13 90.85 84.10 81.98
5 6 7 8
0.55 0.59 0.44 0.73
76.03 75.06 73.00 64.17
9 10 11 12
0.06 0.06 0.05 0.03
63.45 63.87 64.00 63.49
13 14
0.05 32.70 0.05 35.49
Co
Ni
Zn
Kamasite 0.75 5.71 0.01 0.81 6.87 0.01 0.45 13.59 0.05 0.66 15.59 0.02 Taenite 0.28 21.70 0.01 0.30 23.11 0.01 0.19 26.09 0.02 0.12 34.65 0.04 Troilite – – 0.02 – 0.02 – – 0.06 – – 0.02 – Pentlandite 1.81 31.13 0.02 2.39 27.38 0.02
Cu
S
Sum
0.09 – 0.07 0.01
0.13 – 0.03 0.02
99.28 99.09 99.08 99.28
0.21 0.06 0.07 0.09
0.04 0.09 0.08 0.02
98.82 99.22 99.89 99.82
0.06 – 0.01 –
36.06 35.94 35.87 35.91
99.66 99.90 99.99 99.48
0.97 32.54 99.22 0.61 33.14 99.08
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Thus, we studied at the modern analytical level the mineralogy of the Ozernoye meteorite. We discovered the following new minerals: augite, pentlandite, taenite, and merrillite. Perhaps, a completely new mineral, spinel with an unusual composition containing a large amount of Ti, Cr, and Fe, has been discovered. The presence of chlorapatite has been confirmed, while previously described schreibersite, hydroxyapatite, and whitlockite can be considered as questionable results. The petrological type of the meteorite is defined by us as L5. ACKNOWLEDGMENTS This study was supported by the Russian Foundation for Basic Research, project no. 14-05-00464-a “Composition and Structure of Ural Meteorites.” REFERENCES 1. V. N. Loginov, Extended Abstract of Doctoral Dissertation in Geology and Mineralogy (Yekaterinburg, 1991). 2. V. N. Loginov, Ural Meteorites (Ural State Mining Univ., Yekaterinburg, 2004) [in Russian]. 3. A. L. Graham, Meteoritics 23, 171–173 (1988). 4. A. K. Stanyukovich, Rodnaya Starina, No. 1, 42–48 (2008).
5. V. V. Kholodnov, N. A. Artemenko, V. A. Vilisov, and V. N. Loginov, in Yearbook-1989 (Zavaritsky Inst. Geol. Geochem. Ural Branch USSR Acad. Sci., Sverdlovsk, 1990), pp. 55–57 [in Russian]. 6. J. A. Lewis and R. H. Jones, in Proc. 44th Lunar Planet. Sci. Conf. (Woodlands, TX, 2013), Abstr. No. 2722. 7. R. P. Lozano and T. Martin-Crespo, Meteorit. Planet. Sci. 39 (8), 157–162 (2004). 8. A. Ruzicka, M. Killgore, D. W. Mittlefehldt, and M. D. Fries, Meteorit. Planet. Sci. 40 (2), 261–295 (2005). 9. N. N. Shishkin, A. M. Karpenkov, E. A. Kulagov, and G. A. Mitenkov, Dokl. Akad. Nauk SSSR 217 (1), 194–197 (1974). 10. V. A. Koroteev, S. V. Berzin, Yu. V. Erokhin, K. S. Ivanov, and V. V. Khiller, Dokl. Earth Sci. 451 (2), 839– 842 (2013). 11. Yu. V. Erokhin, V. A. Koroteev, V. V. Khiller, E. V. Burlakov, K. S. Ivanov, and D. A. Kleimenov, Dokl. Earth Sci. 464 (2), 1058–1061 (2015). 12. A. J. Bearley and R. H. Jones, in Reviews in Mineralogy and Geochemistry, Vol. 36: Planetary Materials, Ed. by J. J. Papike (Am. Min. Soc., Washington, DC, 1998), pp. 35–38. 13. R. J. Reisener and J. I. Goldstein, Meteorit. Planet. Sci. 38 (11), 1679–1696 (2003). 14. W. R. Van Schmus and J. A. Wood, Geochim. Cosmochim. Acta 31 (5), 747–765 (1967).
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Translated by A. Larionov
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