Individual grains of calcian fayalite and ferroan kirschsteinite, as well as fayalite-kirschsteinite intergrowths are observed in the groundmass of basic crystallised melts, o parabasalts, from burned spoil-heaps of the Chelyabinsk brown-coal basin. Exsolved fayalite and kirschsteinite rims surround the grains of fayalite and early Mg-Fe olivine. The chemical study of the olivines has shown that during their crystallisation they were becoming enriched in fayalite and larnite and depleted in forsterite. The intergrowths of ferroan kirschsteinite (> 20 wt.% of CaO) and calcian fayalite (< 8.5 wt.% of CaO) are the exsolution products of an initially homogeneous Ca-Fe olivine with CaO > 8.5 wt.%. The exsolution temperatures were estimated to 980–800 °C. The main reasons for the appearance of the Ca-Fe olivine in the parabasalts are the composition of the initial melt enriched in FeO and CaO, fractional crystallisation resulting in further enrichment in iron of the residual low-silica melt, and reducing conditions during olivine crystallisation and exsolution.

You do not have access to this content, please speak to your institutional administrator if you feel you should have access.