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Varela M.E.,Institute Ciencias Astronomicas Of La Tierra Y Del Espacio Icate | Sylvester P.,Memorial University of Newfoundland | Sylvester P.,Texas Tech University | Brandstatter F.,Mineralogisch Petrographische Abteilung | Engler A.,University of Graz
Meteoritics and Planetary Science | Year: 2015

Sixteen nonporphyritic chondrules and chondrule fragments were studied in polished thin and thick sections in two enstatite chondrites (ECs): twelve objects from unequilibrated EH3 Sahara 97158 and four objects from equilibrated EH4 Indarch. Bulk major element analyses, obtained with electron microprobe analysis (EMPA) and analytical scanning electron microscopy (ASEM), as well as bulk lithophile trace element analyses, determined by laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS), show that volatile components (K2O + Na2O versus Al2O3) scatter roughly around the CI line, indicating equilibration with the chondritic reservoir. All lithophile trace element abundances in the chondrules from Sahara 97158 and Indarch are within the range of previous analyses of nonporphyritic chondrules in unequilibrated ordinary chondrites (UOCs). The unfractionated (solar-like) Yb/Ce ratio of the studied objects and the mostly unfractionated refractory lithophile trace element (RLTE) abundance patterns indicate an origin by direct condensation. However, the objects possess subchondritic CaO/Al2O3 ratios; superchondritic (Sahara 97158) and subchondritic (Indarch) Yb/Sc ratios; and chondritic-normalized deficits in Nb, Ti, V, and Mn relative to RLTEs. This suggests a unique nebular process for the origin of these ECs, involving elemental fractionation of the solar gas by the removal of oldhamite, niningerite, and/or another phase prior to chondrule condensation. A layered chondrule in Sahara 97158 is strongly depleted in Nb in the core compared to the rim, suggesting that the solar gas was heterogeneous on the time scales of chondrule formation. Late stage metasomatic events produced the compositional diversity of the studied objects by addition of moderately volatile and volatile elements. In the equilibrated Indarch chondrules, this late process has been further disturbed, possibly by a postaccretional process (diffusion?) that preferentially mobilized Rb with respect to Cs in the studied objects. © The Meteoritical Society, 2015. Source

Bayliss P.,College Street | Kolitsch U.,Mineralogisch Petrographische Abteilung | Nickel E.H.,CSIRO | Pring A.,South Australian Museum
Mineralogical Magazine | Year: 2010

Minamiite has been discredited and renamed natroalunite-2c to show a double unit-cell structure and natroalunite can be designated as natroalunite-1c to show a single unit-cell structure. Kintoreite can be designated as kintoreite-1c to show the same single unit-cell structure, and IMA 1993-039 is a new superstructure of kintoreite and can be designated as kintoreite-2c to show a double unit-cell structure. Beaverite has been renamed beaverite-(Cu). The Zn-bearing beaverite of Sato et al. (2008) has been named "beaverite-(Zn) ", but data for the mineralhave not been approved by the CNMNC. Orpheite has been discredited as P-rich hinsdalite. Proposal 07-D was approved by the CNMNC. © 2010 Mineralogical Society. Source

Kurat G.,University of Vienna | Varela M.E.,Institute Ciencias Astronomicas Of La Tierra Y Del Espacio Icate | Zinner E.,Washington University in St. Louis | Brandstatter F.,Mineralogisch Petrographische Abteilung
Meteoritics and Planetary Science | Year: 2010

Tucson is an enigmatic ataxitic iron meteorite, an assemblage of reduced silicates embedded in Fe-Ni metal with dissolved Si and Cr. Both, silicates and metal, contain a record of formation at high temperature (~1800 K) and fast cooling. The latter resulted in the preservation of abundant glasses, Al-rich pyroxenes, brezinaite, and fine-grained metal. Our chemical and petrographic studies of all phases (minerals and glasses) indicate that they have a nebular rather than an igneous origin and give support to a chondritic connection as suggested by Prinz et al. (1987). All silicate phases in Tucson apparently grew from a liquid that had refractory trace elements at approximately 6-20 × CI abundances with nonfractionated (solar) pattern, except for Sc, which was depleted (~1 × CI). Metal seems to have precipitated before and throughout silicate aggregate formation, allowing preservation of all evolutionary steps of the silicates by separating them from the environment. In contrast to most chondrites, Tucson documents coprecipitation of metal and silicates from the solar nebula gas and precipitation of metal before silicates-in accordance with theoretical condensation calculations for high-pressure solar nebula gas. We suggest that Tucson is the most metal-rich and volatile-element-poor member of the CR chondrite clan. © The Meteoritical Society, 2011. Source

Elliott P.,University of Adelaide | Elliott P.,South Australian Museum | Giester G.,University of Vienna | Libowitzky E.,University of Vienna | Kolitsch U.,Mineralogisch Petrographische Abteilung
American Mineralogist | Year: 2010

Liversidgeite, ideally Zn6 (PO4)4· 7H2O, is a new mineral from Block 14 Opencut, Broken Hill, New South Wales, Australia. The mineral occurs as white, thin, bladed crystals and as hemispherical aggregates of radiating crystals in cavities in sphalerite-galena ore. Associated minerals are anglesite, pyromorphite, greenockite, sulfur, and an unknown Zn phosphate sulfate. Individual crystals are up to 0.1 mm in length and 0.05 mm across. Liversidgeite is transparent to translucent, with a vitreous luster and a white streak. It is brittle with an irregular fracture, the Mohs hardness is ∼3-3.5, and the observed and calculated densities are 3.21(2) and 3.28 g/cm3, respectively. Chemical analysis by elec-tron microprobe gave ZnO 54.62, MnO 0.49, PbO 0.18, P2O5 32.62, As2O5 0.65, SO3 0.35, H2O 14.04, total 102.95 wt%, with H2O content derived from the refined crystal structure. The empirical formula calculated on the basis of 23 O atoms is Pb0.01 (Zn5.86Mn0.06)S5.92 (P 4.01As0.05S0.04)S4.10 O16.20·6.8H2O. Liver-sidgeite is triclinic, space group P1, with a = 8.299(1), b = 9.616(1), c = 12.175(1) Å, α = 71.68(1), β = 82.02(1), γ = 80.18(1)°, V = 905.1(2) Å3 (single-crystal data), and Z = 2. The six strongest lines in the X-ray powder diffraction pattern are [d(Å), (I), (hkl)]: 8.438 (80) (011), 3.206 (60) (013̄), 2.967 (75) (21̄2, 114), 2.956 (75) (212̄), 2.550 (85) (233, 21̄3), 2.537 (100) (221̄, 014̄, 311̄). The crystal structure of liversidgeite was refined to an R1 index of 5.95% based on 3054 observed (Fo > 4σFo) reflections measured with MoKα X-radiation. The structure is based on two distinct, infinite zigzag chains of edge-sharing ZnΦ6 (Φ = unspecified anion) octahedra that extend in the a direction. The chains link to each other via common corners and also via corner-sharing PO4 tetrahedra, forming sheets parallel to the (011) plane. The sheets link via [Zn2Φ8] dimeric building units, comprising edge-sharing ZnΦ5 trigonal bipyramids and ZnΦ4 tetrahedra, resulting in an open framework. Large ellipsoidal channels extend along the a direction and are occupied by interstitial H2O groups and the H atoms of the H2O groups that coordinate to the Zn cations. An extensive network of hydrogen bonds provides additional linkage between the sheets in the structure, via the interstitial H2O groups. The topology of the liver-sidgeite structure is identical to that of synthetic, monoclinic Zn2Co4 (PO4)4 (H 2O)5 ·2H2O. Source

Ertl A.,University of Vienna | Mali H.,University of Leoben | Schuster R.,Geologische Bundesanstalt | Korner W.,University of Vienna | And 3 more authors.
Mineralogy and Petrology | Year: 2010

Pale-blue to pale-green tourmalines from the contact zone of Permian pegmatites to mica schists and marbles from different localities of the Austroalpine basement units (Rappold Complex) in Styria, Austria, are characterized. All these Mg-rich tourmalines have small but significant Li contents, up to 0.29 wt% Li2O, and can be characterized as dravite, with FeO contents of ~ 0.9-2.7 wt%. Their chemical composition varies from X(Na0.67Ca0.19 K0.02{ballot box}0.12) Y(Mg1.26Al0.97Fe2+ 0.36Li0.19Ti4+ 0.06Zn0.01{ballot box}0.15) Z(Al5. 31 Mg0.69) (BO3)3 Si6O18 V(OH)3 W[F0.66(OH)0.34], with a = 15.9220(3), c = 7.1732(2) Å to X(Na0.67Ca0.24 K0.02{ballot box}0.07) Y(Mg1.83Al0.88Fe2+ 0.20Li0.08Zn0.01Ti4+ 0.01{ballot box}0.09) Z(Al5.25 Mg0.75) (BO3)3 Si6O18 V(OH)3 W[F0.87(OH)0.13], with a = 15.9354(4), c = 7.1934(4) Å, and they show a significant Al-Mg disorder between the Y and the Z sites (R1 = 0.013-0.015). There is a positive correlation between the Ca content and distance for all investigated tourmalines (r ≈ 1.00), which may reflect short-range order configurations including Ca and Fe2+, Mg, and Li. The tourmalines have XMg (XMg = Mg/Mg + Fetotal) values in the range 0.84-0.95. The REE patterns show more or less pronounced negative Eu and positive Yb anomalies. In comparison to tourmalines from highly-evolved pegmatites, the tourmaline samples from the border zone of the pegmatites of the Rappold Complex contain relatively low amounts of total REE (~8-36 ppm) and Th (0.1-1.8 ppm) and have low LaN/YbN ratios. There is a positive correlation (r ≈ 0.91) between MgO of the tourmalines and the MgO contents of the surrounding mica schists. We conclude that the pegmatites formed by anatectic melting of mica schists and paragneisses in Permian time. The tourmalines crystallized from the pegmatitic melt, influenced by the metacarbonate and metapelitic host rocks. © 2009 Springer-Verlag. Source

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