Tuite, γ-Ca3(PO4)2, formed by chlorapatite decomposition in a shock vein of the Suizhou L6 chondrite

Abstract

Tuite, γ-Ca3(PO4)2, was first discovered as the high-pressure phase of whitlockite in shock veins of the Suizhou L6 meteorite. This study reports the finding of tuite in a shock vein of the same Suizhou chondrite as a product of decomposition of chlorapatite, where it coexists with coarse-grained ringwoodite, majorite, lingunite, fine-grained majorite-pyrope solid solution, and magnesiowüstite. Moreover, we also successfully synthesized tuite with a multianvil apparatus from chlorapatite at 15 GPa and 1573 K over 24 h. Both natural and synthetic tuite crystals were examined by means of optical microscopy, scanning electron microscope, electron microprobe analysis, X-ray diffraction, and Raman spectroscopy. Our results suggest that the Na2O, MgO, and Cl contents in natural tuite may serve as good indicators for distinguishing the precursor phosphate mineral, chlorapatite or whitlockite. © The Meteoritical Society, 2013.