Beckettite, CA < Inf > 2 < /Inf > V < Inf > 6 < /Inf > Al < Inf > 6 < /Inf > O < Inf > 20 < /Inf > , a New Mineral in a Type a Refractory Inclusion From Allende and Clues to Processes in the Early Solar System

Document Type

Article

Publication Date

12-7-2021

Publication Title

Meteoritics and Planetary Science

Volume

56

Issue

12

First page number:

2265

Last page number:

2272

Abstract

Beckettite (Ca2V6Al6O20; IMA 2015-001) is a newly discovered refractory mineral, occurring as micrometer-sized grains intergrown with hibonite and perovskite, and surrounded by secondary grossular, anorthite, coulsonite, hercynite, and corundum. It occurs within highly altered areas in a V-rich, Type A Ca-Al-rich inclusion (CAI), A-WP1, from the Allende CV3 carbonaceous chondrite. The type beckettite has an empirical formula of (Ca1.99Na0.01)(V3+3.47Al1.40Ti4+0.57Mg0.25Sc0.08Fe2+0.04)(Al5.72Si0.28)O20, with a triclinic structure in space group P (Formula presented.) and cell parameters a = 10.367 Å, b = 10.756 Å, c = 8.895 Å, α = 106.0°, β = 96.0°, γ = 124.7°, V = 739.7 Å3, and Z = 2, which leads to a calculated density of 3.67 g cm−3. Beckettite’s general formula is Ca2(V,Al,Ti,Mg)6Al6O20 and the endmember formula is Ca2V6Al6O20. Beckettite is slightly 16O-depleted (Δ17O = −16 ± 2‰) compared to the coexisting hibonite and spinel −24 ± 2‰. Beckettite is a primary high-temperature mineral resulting from igneous crystallization of an 16O-rich V-rich CAI melt together with V-bearing hibonite, perovskite, burnettite, spinel, and paqueite. Subsequently, beckettite experienced an incomplete isotope exchange with an 16O-poor aqueous fluid (Δ17O = −3 ± 2‰) on the Allende parent asteroid.

Controlled Subject

Solar system

Disciplines

Structures and Materials | Thermodynamics

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