TY - JOUR

T1 - Botuobinskite and mirnyite, two new minerals of the crichtonite group included in Cr-pyrope xenocrysts from the Internatsionalnaya kimberlite

AU - Rezvukhin, Dmitriy I.

AU - Rashchenko, Sergey V.

AU - Sharygin, Igor S.

AU - Malkovets, Vladimir G.

AU - Alifirova, Taisia A.

AU - Pautov, Leonid. A.

AU - Nigmatulina, Elena N.

AU - Seryotkin, Yurii V.

N1 - SEM-EDS examinations, crystal data collection and structure refinement studies were supported by the Russian Science Foundation project No. 18-77-10062-P (https://rscf.ru/en/project/21-77-03004/). Electron microprobe WDS-analyses were performed within the Russian Science Foundation project No. 18-77-00249. Sample preparation, Raman and FTIR studies were carried out within the state assignment project of IGM SB RAS. Публикация для корректировки.

PY - 2023/6/10

Y1 - 2023/6/10

N2 - Two new mineral species of the crichtonite group: botuobinskite, ideally SrFe 2+ (Ti 4+ 12 Cr 3+ 6 )Mg 2 [O 36 (OH) 2 ] and mirnyite, ideally SrZr(Ti 4+ 12 Cr 3+ 6 )Mg 2 O 38 , occur as inclusions in mantle-derived Cr-pyrope xenocrysts from the Internatsionalnaya kimberlite pipe, Mirny field, Siberian craton. Botuobinskite forms needle- and blade-like acicular crystals up to 1 mm in length and up to 30 μm in diameter, a large platy inclusion (700 × 700 × 80 μm) and roughly isometric grains (up to 80 μm). Mirnyite occurs as needle-and blade-like elongated inclusions (up to 1 mm). Both minerals are jet-black, opaque and exhibit a metallic lustre. In plane-polarised reflected light, botuobinskite and mirnyite are greyish-white with a weak brownish tint. Between crossed polars, the new species show distinct anisotropy in shades of bluish grey to greenish-brown. Neither bireflectance nor pleochroism is observed. Calculated densities for botuobinskite and mirnyite are 4.3582(5) and 4.3867(3) gm/cm 3 , respectively. The crystal structures of botuobinskite and mirnyite have been refined ( R = 0.0316 and 0.0285, respectively) from single crystal X-ray diffraction data. The minerals are trigonal, crystallise in the space group R $\bar{3}$ (No. 148) and are isostructural with other members of the crichtonite group. The unit cell parameters are a = 10.3644(8) Å, c = 20.6588(11) Å and V = 1921.9(2) Å 3 for botuobinskite and a = 10.3734(8) Å, c = 20.6910 (12) Å and V = 1928.2(2) Å 3 for mirnyite, with Z = 3 for both. The Raman spectra of the minerals show strong peaks at 133, 313 and 711 cm –1 . Infrared spectroscopy data for botuobinskite indicates H–O stretching of the hydroxyl groups. Botuobinskite and mirnyite have been approved by the IMA–CNMNC under the numbers 2018-143a and 2018-144a, respectively. Botuobinskite and mirnyite are named after the Botuobinskaya exploration expedition and Mirny town, respectively. The minerals may be considered as crystal-chemical analogues of other crichtonite-group species occurring in the lithospheric mantle (i.e. loveringite, lindsleyite and mathiasite). Both species commonly occur in intimate association with Cr-pyrope as well as other peridotitic minerals and exert an important control on the partitioning of incompatible elements during mantle metasomatism.

AB - Two new mineral species of the crichtonite group: botuobinskite, ideally SrFe 2+ (Ti 4+ 12 Cr 3+ 6 )Mg 2 [O 36 (OH) 2 ] and mirnyite, ideally SrZr(Ti 4+ 12 Cr 3+ 6 )Mg 2 O 38 , occur as inclusions in mantle-derived Cr-pyrope xenocrysts from the Internatsionalnaya kimberlite pipe, Mirny field, Siberian craton. Botuobinskite forms needle- and blade-like acicular crystals up to 1 mm in length and up to 30 μm in diameter, a large platy inclusion (700 × 700 × 80 μm) and roughly isometric grains (up to 80 μm). Mirnyite occurs as needle-and blade-like elongated inclusions (up to 1 mm). Both minerals are jet-black, opaque and exhibit a metallic lustre. In plane-polarised reflected light, botuobinskite and mirnyite are greyish-white with a weak brownish tint. Between crossed polars, the new species show distinct anisotropy in shades of bluish grey to greenish-brown. Neither bireflectance nor pleochroism is observed. Calculated densities for botuobinskite and mirnyite are 4.3582(5) and 4.3867(3) gm/cm 3 , respectively. The crystal structures of botuobinskite and mirnyite have been refined ( R = 0.0316 and 0.0285, respectively) from single crystal X-ray diffraction data. The minerals are trigonal, crystallise in the space group R $\bar{3}$ (No. 148) and are isostructural with other members of the crichtonite group. The unit cell parameters are a = 10.3644(8) Å, c = 20.6588(11) Å and V = 1921.9(2) Å 3 for botuobinskite and a = 10.3734(8) Å, c = 20.6910 (12) Å and V = 1928.2(2) Å 3 for mirnyite, with Z = 3 for both. The Raman spectra of the minerals show strong peaks at 133, 313 and 711 cm –1 . Infrared spectroscopy data for botuobinskite indicates H–O stretching of the hydroxyl groups. Botuobinskite and mirnyite have been approved by the IMA–CNMNC under the numbers 2018-143a and 2018-144a, respectively. Botuobinskite and mirnyite are named after the Botuobinskaya exploration expedition and Mirny town, respectively. The minerals may be considered as crystal-chemical analogues of other crichtonite-group species occurring in the lithospheric mantle (i.e. loveringite, lindsleyite and mathiasite). Both species commonly occur in intimate association with Cr-pyrope as well as other peridotitic minerals and exert an important control on the partitioning of incompatible elements during mantle metasomatism.

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85148612131&origin=inward&txGid=747dd2e7223bdbd084799f8405abeeee

UR - https://www.mendeley.com/catalogue/b55e6a50-8607-3c78-96cf-1b037b0d842b/

U2 - 10.1180/mgm.2023.10

DO - 10.1180/mgm.2023.10

M3 - Article

VL - 87

SP - 433

EP - 442

JO - Mineralogical Magazine

JF - Mineralogical Magazine

SN - 0026-461X

IS - 3

ER -