SODIUM-RICH PHOSPHATE AND SILICATE INCLUSIONS IN TROILITE NODULE IN

DARINSKOE IRON METEORITE (IIC)

Meteorite Darinskoe (1 sample, 11.2 kg) was found in 1984 in Ural’sk

district of Kazakhstan. It is plessitic octachedrite (IIC group)

(Wlotzka, 1995), which contains two troilite nodules (up to 3 cm). In

addition to large troilite nodules, kamacite (Ni – 6.6-7.8, Co – 1.0-1.4

wt.%) and plessite aggregate the Darinskoe iron consists of small

troilite isolations (up to 1 mm), kamacite, chromite, schreibersite

(rhabdite), pentlandite and cobaltpentlandite. According to LA-ICP-

MS data (Chernonozhkin et al., 2014) the bulk composition of the

Darinskoe meteorite is: Ni – 11.4 wt.%; Co – 0.59 wt.%; Cu - 147; Ga

– 44; Ge – 90; As - 5.6; Mo - 18.3; Ru – 25.1; Rh – 1.6; Pd – 2.9; Ir –

12.8; Pt – 13.5; Au – 0.6, Re – 1; W – 3.3 ppm.

Chromite in troilite nodule

Victor V. Sharygin1,2,3

1V.S.Sobolev Institute of Geology and Mineralogy, 3 Akad. Koptyuga pr., Novosibirsk, 630090, Russia, E-mail: sharygin@igm.nsc.ru, 2Novosibirsk State University, 2 Pirogova str., Novosibirsk, 630090, Russia; 3ExtraTerra Consortium, Institute of Physics and Technology, Ural Federal University, 19 Mira str., Ekaterinburg 620002, Russia.

References

Wlotzka F. 1995. Meteoritics 30:792-796.

Chernonozhkin S.M. et al. 2014. Journal of Analytical

Atomic Spectrometry 29:1001-1016.

Darinskoe meteorite

One of large cut-off

Polished surface

Oxidation after polishing

Sulfide nodule

Sample for study

Fragment of

sulfide nodule

Troilite nodule

Kamacite

Plessite

Sch

Plessite

Troilite

Kamacite

Kmc

Sch

Crt

Plessite

Plessite

Kmc

Sch

Plessite

Plessite

Kmc

Sch

Crt The terrestrial alteration phases are

represented by Ni-rich goethite, Cl-

bearing Fe-Ni-hydroxides (akaganeite,

droninoite) and Ni-rich siderite.

Alteration in plessite aggregate

(goethite, akaganeite, droninoite, siderite)

BSE P Fe Ni

Cr Cl O False

Sch

Plessite Kmc

Crt

Plessite

Kamacite

Sch

Sid

Tro + Pn + Co-Pn

BSE S Fe Cu

Ni Co O False

Tro

Co-Pn

Pentlandite and cobaltpentlandite (replacement of troilite ?)

PHOSPHATE AND SILICATE INCLUSIONS IN TROILITE NODULE

MgO Al2O3 TiO2 V2O3 Cr2O3 MnO FeO Sum

n=5 0.34 0.17 0.17 0.24 66.52 0.53 31.87 99.84

Crt Crt

Crt

Crt

Troilite

Schreibersite in troilite nodule

Troilite

Sch

Sch

Pn

Akaganeite

P S Cr Fe Co Ni Cu Sum Mineral

n=4 36.68 0.49 62.70 0.00 99.86 Troilite

n=2 14.32 51.25 0.50 33.20 99.27 Schreibersite

n=1 34.53 0.51 40.64 1.18 20.73 2.96 100.55 Pentlandite

BSE P S Fe

Ca Na O False

Buchwaldite

Ca-P-hydro

Na2O P2O5 SO3 K2O CaO FeO Sum Mineral

n=6 19.57 43.77 0.32 0.17 35.70 1.25 100.77 Buchwaldite

F Na2O MgO SiO2 P2O5 SO3 Cl K2O CaO Cr2O3 MnO FeO SrO BaO Sum Mineral

n=2 0.00 0.40 24.61 0.31 2.38 0.45 1.74 44.93 74.80 Fe-Cl-H2O-phosphate

n=4 0.00 1.16 1.08 0.54 36.29 0.38 0.25 0.31 5.71 1.40 6.71 25.37 0.38 0.30 79.86 Fe-Mn-Ca-H2O-phosphate

n=4 0.24 1.45 49.10 0.35 38.41 1.26 0.37 91.17 Ca-H2O-phosphate

BSE P S Fe Cu

Ni Cr Mn Ca K

Na Cl O C False

Ca

Fe-Cl

Fe-Mn-Ca

Fe-Mn-Ca Djr

Ch

BSE false P S Fe Cu Ni Mn Ca K O

Djr

Ch

Fe-Mn-Ca

Ni-Te

Ca

Ca

Fe Ni Co Cu K Na S Cl Sum Mineral

n=15 44.48 9.31 0.15 3.04 8.90 0.00 34.01 0.00 99.90 Cl-free Djerfisherite

O P S Mn Fe Ni Cu Sum Mineral

n=9 4.19 1.26 32.80 0.30 32.39 0.41 30.13 101.47 Chalcopyrite?

BSE P S Fe Si Ni

Ti Ca K Na O False

Si-glass

Ca-Phosphate

SiO2 TiO2 Cr2O3 Al2O3 FeO MgO CaO Na2O K2O P2O5 SO3 F Sum

n=4 60.74 11.15 3.03 0.11 2.44 0.61 0.36 11.93 3.99 0.56 0.48 0.18 95.56 Si-glass ?

BSE P S Fe Si

Ni Cr Ti Ca K

Na Cu O C False

Si-glass

Ph

Pn

SiO2 TiO2 Cr2O3 Al2O3 FeO MgO CaO Na2O K2O P2O5 SO3 F Sum

n=5 64.49 9.72 3.36 0.12 2.27 0.73 0.39 12.93 2.43 0.49 0.35 0.39 97.66 Si-glass ?

BSE P S

Fe Si Ni

Cr Ti

Ca K Na

Cl O False

Mg

Si-glass

Djr

Altered glass

Chlorite ?

SiO2 TiO2 Cr2O3 Al2O3 FeO MgO CaO Na2O K2O P2O5 SO3 Cl Sum Phase

n=3 35.32 3.37 2.39 39.24 0.94 1.06 2.88 85.19 Chlorite ?

n=3 72.62 3.45 2.19 0.06 2.30 1.28 0.32 9.49 2.35 1.03 0.36 95.43 Si-glass ?

n=3 73.68 3.61 2.49 0.00 3.03 1.19 0.29 2.06 1.95 0.98 1.46 90.72 Altered glass

The studied troilite nodule (2.5 cm) contains rounded chromite grains (50-100 µm), euhedral schreibersite (10-100 µm),

phosphate and silicate inclusions (10-30 µm). Sulfides (Cl-free djerfisherite, pentlandite, chalcopyrite, cubanite) and Ni-Te

phase are sometimes associated with the inclusions. Host troilite is rich in Cr (0.4-1.0 wt.%).

Phosphate inclusions are mainly composed by hydrated Ca-Mn-Fe phosphates (supported by Raman), which seems to be

alteration products of initial alkali-rich anhydrous phosphates in the terrestrial conditions. Only buchwaldite NaCa(PO4) has

been found as a primary phase in some phosphate inclusions.

The silicate inclusions have very specific and variable composition (range in wt.%): SiO2 – 60.7-72.6; TiO2 – 3.5-11.2;

Cr2O3 – 2.1-3.4; Al2O3 – 0.05-0.15; FeO – 2.3-2.4; MgO – 0.3-0.4; CaO – 0.3-0.4; Na2O – 11.5-12.9; K2O - 2.4-4.0; P2O5 –

0.51; SO3 – 0.4-0.5. No similar compositions were found among known mineral species and thus suggest that it maybe a

Na-rich silicate glass.

Polished samples of the Darinskoe meteorite were examined using optical microscope Olympus BX51, scanning

microscope TESCAN MIRA 3MLU SEM with EDS/WDS system and LabRAM HR 800 mm spectrometer.

unidentified micron-sized Ni-Te-phase - Ni - >16, Te - >32 wt.%

This work was supported by the State assignment project (IGM SB RAS 0330-

2016-0005) and the Act 211 of the Government of the Russian Federation,

agreement N 02.A03.21.0006.

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