Discovery of meteoritic baghdadite, Ca_3(Zr,Ti)Si_2O_9, in Allende: The first solar silicate with structurally essential zirconium?

Abstract

During an ongoing nanomineralogy investigation of the Allende CV3 carbonaceous chondrite, baghdadite, Ca_3(Zr,Ti)Si_2O_9, has been identified in a V-rich, fluffy Type A Ca-Al-rich refractory inclusion (CAI), AWP1, in USNM 7617. Reported here is the first meteoritic occurrence of baghdadite, as an ultra-refractory silicate mineral in a CAI from a primitive meteorite, among the first solid materials formed in the solar system. Field-emission scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), electron back-scatter diffraction (EBSD) and electron probe microanalyzer (EPMA) were used to characterize baghdadite and associated phases. Three new minerals burnettite (IMA 2013-054; CaV^(3+)AlSiO_6), paqueite (IMA 2013-053; Ca_3TiSi_2(Al_2Ti)O_(14)) and beckettite (IMA 2015-001; Ca2V^(3+)_6Al_6O_(20)), were also discovered in A-WP1 [1-4].