Discovery of the Naturally Occurring Pure CaTiO3 Cubic Perovskite from Tazheran Massif.

As the parent compound of the perovskite-structured family and an analogue of davemaoite CaSiO₃ in Earth's lower mantle, CaTiO₃ perovskite is widely used in electronic ceramic materials, immobilizing radioactive waste, and geosciences. Here we report the discovery of a natural pure CaTiO₃ perovskite-C in calc-silicate veins in brucite marble in the Tazheran Massif, Russia. The mean composition of perovskite-C is 97 wt% total CaO and TiO2, and minor impurities of Na, Al, and Zr, yielding the chemical formula CaTi0.97Al0.01Na0.01Zr0.01O3. The cubic crystal structure--Pm3m, Z = 1: a = 3.8301 Å, V = 56.19 (2) Å3 (ρ = 4.019 g/cm3) has been refined to R1 = 0.0451. Compared with the cubic perovskite discovered in Israel, the cubic perovskite discovered in this study is very pure in Ca and Ti. The naturally occurring perovskite-C from Tazheran implies that the host skarn might have experienced high-temperature (> 1247--1374 °C) metamorphism and/or metasomatism at an early stage. Moreover, the discovery of natural perovskite-C also draws attention to considering crystal-structure- related matrix effects in the future of in situ U-Pb geochronology, especially using Tazh international perovskite standards. [ABSTRACT FROM AUTHOR]