TY - JOUR

T1 - Discovery of dmisteinbergite (hexagonal CaAl2Si2O8) in the Allende meteorite

T2 - a new member of refractory silicates formed in the solar nebula

AU - Ma, Chi

AU - Krot, Alexander N.

AU - Bizzarro, Martin

PY - 2013

Y1 - 2013

N2 - Dmisteinbergite, CaAlSiO with P63/mcm structure, was identified in a rounded coarse-grained igneous Type B2 Ca-,Al-rich inclusion (CAI) STP-1 from the Allende CV3 carbonaceous chondrite. STP-1 belongs to a very rare type of refractory inclusions, Fractionation and Unknown Nuclear effects (FUN) CAIs, which experienced melt evaporation and crystallization at low total gas pressure (P <10bar) in a high-temperature (>1200 °C) region, possibly near the proto-Sun and were subsequently radially transported away from region, possibly by a disk wind. The Allende dmisteinbergite occurs as irregular single crystals (100-600 mm in size) in contact with gehlenitic melilite and Al,Ti-diopside, poikilitically enclosing euhedral spinel, and rare anorthite. It is colorless and transparent. The mean chemical composition, determined by electron microprobe analysis, is (wt%) SiO 42.6, AlO 36.9, CaO 20.2, MgO 0.05, sum 99.75, giving rise to an empirical formula of CaAl SiO. Its electron backscatter diffraction patterns are a good match to that of synthetic CaAl SiO with the P6/mcm structure and the unit cell a = 5.10 Å, c = 14.72 Å, and Z = 2. Dmisteinbergite could have crystallized from a silicate melt at high temperature (∼1200-1400 °C) via rapid cooling. Dmisteinbergite in Allende, the first find in a meteorite, is a new member of refractory silicates, among the first solid materials formed in the solar nebula.

AB - Dmisteinbergite, CaAlSiO with P63/mcm structure, was identified in a rounded coarse-grained igneous Type B2 Ca-,Al-rich inclusion (CAI) STP-1 from the Allende CV3 carbonaceous chondrite. STP-1 belongs to a very rare type of refractory inclusions, Fractionation and Unknown Nuclear effects (FUN) CAIs, which experienced melt evaporation and crystallization at low total gas pressure (P <10bar) in a high-temperature (>1200 °C) region, possibly near the proto-Sun and were subsequently radially transported away from region, possibly by a disk wind. The Allende dmisteinbergite occurs as irregular single crystals (100-600 mm in size) in contact with gehlenitic melilite and Al,Ti-diopside, poikilitically enclosing euhedral spinel, and rare anorthite. It is colorless and transparent. The mean chemical composition, determined by electron microprobe analysis, is (wt%) SiO 42.6, AlO 36.9, CaO 20.2, MgO 0.05, sum 99.75, giving rise to an empirical formula of CaAl SiO. Its electron backscatter diffraction patterns are a good match to that of synthetic CaAl SiO with the P6/mcm structure and the unit cell a = 5.10 Å, c = 14.72 Å, and Z = 2. Dmisteinbergite could have crystallized from a silicate melt at high temperature (∼1200-1400 °C) via rapid cooling. Dmisteinbergite in Allende, the first find in a meteorite, is a new member of refractory silicates, among the first solid materials formed in the solar nebula.

UR - http://www.scopus.com/inward/record.url?scp=84879948711&partnerID=8YFLogxK

U2 - 10.2138/am.2013.4496

DO - 10.2138/am.2013.4496

M3 - Letter

AN - SCOPUS:84879948711

VL - 98

SP - 1368

EP - 1371

JO - American Mineralogist

JF - American Mineralogist

SN - 0003-004X

IS - 7

ER -