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Kaitianite, Ti³⁺₂Ti⁴⁺O₅, a new titanium oxide mineral from Allende

Ma, Chi and Beckett, John R. (2020) Kaitianite, Ti³⁺₂Ti⁴⁺O₅, a new titanium oxide mineral from Allende. Meteoritics and Planetary Science . ISSN 1086-9379. (In Press)

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Kaitianite, Ti³⁺₂Ti⁴⁺O₅, is a new titanium oxide mineral discovered in the Allende CV3 carbonaceous chondrite. The type grain coexists with tistarite (Ti₂O₃) and rutile. Corundum, xifengite, mullite, osbornite, and a new Ti,Al,Zr‐oxide mineral are also present, although not in contact. The chemical composition of type kaitianite is (wt%) Ti₂O₃ 56.55, TiO₂ 39.29, Al₂O₃ 1.18, MgO 1.39, FeO 0.59, V₂O₃ 0.08 (sum 99.07), yielding an empirical formula of (Ti³⁺_(1.75)Al_(0.05)Ti⁴⁺_(0.10)Mg_(0.08)Fe_(0.02))(Ti⁴⁺_(1.00))O₅, with Ti³⁺ and Ti⁴⁺ partitioned, assuming a stoichiometry of three cations and five oxygen anions pfu. The end‐member formula is Ti³⁺₂Ti⁴⁺O₅. Kaitianite is the natural form of γ‐Ti₃O₅ with space group C2/c and cell parameters a = 10.115 Å, b = 5.074 Å, c = 7.182 Å, β = 112º, V = 341.77 ų, and Z = 4. Both the type kaitianite and associated rutile likely formed as oxidation products of tistarite at temperatures below 1200 K, but this oxidation event could have been in a very reducing environment, even more reducing than a gas of solar composition. Based on experimental data on the solubility of Ti³⁺ in equilibrium with corundum from the literature, the absence of tistarite in or on Ti³⁺‐rich corundum (0.27–1.45 mol% Ti₂O₃) suggests that these grains formed at higher temperatures than the kaitianite (>1579–1696 K, depending on the Ti concentration). The absence of rutile or kaitianite in or on corundum suggests that any exposure to the oxidizing environment producing kaitianite in tistarite was too short to cause the precipitation of Ti‐oxides in or on associated corundum.

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Ma, Chi0000-0002-1828-7033
Alternate Title:Kaitianite, Ti3+2Ti4+O5, a new titanium oxide mineral from Allende
Additional Information:© 2020 The Meteoritical Society. Received 15 December 2019; revision accepted 09 September 2020. SEM, EBSD, and EPMA analyses were carried out at the Caltech GPS Division Analytical Facility, which is supported, in part, by NSF Grants EAR‐0318518 and DMR‐0080065. Tim McCoy and Glenn MacPherson provided basic information on how those USNM sections were prepared at SI‐NMNH. We thank Andrew Davis, Steven Simon, and AE Tim Fagan for their critical and constructive reviews.
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Record Number:CaltechAUTHORS:20201014-121824967
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Official Citation:Ma, C. and Beckett, J.R. (2020), Kaitianite, Ti3+2Ti4+O5, a new titanium oxide mineral from Allende. Meteorit Planet Sci. doi:10.1111/maps.13576
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106060
Deposited By: Tony Diaz
Deposited On:14 Oct 2020 19:38
Last Modified:14 Oct 2020 19:38

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