^1,2Xiande Xie, ³Xiangping Gu,²Ming Chen
¹Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
²Guangdong Key Laboratory of Mineral Physics and Materials, Guangzhou, China
³School of Geosciences and Info-Physics, Central South University, Changsha, Hunan, China

Tuite is a high-pressure γ-form of Ca3(PO4)2. An occurrence of tuite partly transformed from merrillite and chlorapatite was observed in the chondritic area adjacent to the shock veins in the Suizhou meteorite. Tuite grains are found in contact with both merrillite and chlorapatite, indicating two different transformation pathways. Tuite isochemically transformed from merrillite contains much higher contents of Na2O and MgO than those transformed from chlorapatite. Tuite transformed from merrillite does not contain Cl, but tuite transformed from chlorapatite contains 1.90–3.91 wt% of Cl, hence indicating an incomplete phase transformation from chlorapatite to tuite. P-T conditions of above 12 GPa and 1100 °C are probably required for the transformation from merrillite and chlorapatite to tuite. A temperature gradient from the hot vein at 2000 °C to the surrounding chondritic area at 1000 °C corresponds to the partial phase transitions in the Suizhou phosphates. Fast cooling of the thin shock veins plays a key role in the preservation of phosphates that suffered partial high-pressure phase transformation.

Reference
Xie X, Gu X, Chen M (2015) An occurrence of tuite, γ-Ca3(PO4)2, partly transformed from Ca-phosphates in the Suizhou meteorite. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12577]
Published by arrangement with John Wiley & Sons