Fayalite and kirschsteinite solid solutions in melts from burned spoil-heaps, South Urals, Russia
Sokol, Ella; Sharygin, Victor; Kalugin, Valery; Volkova, Nina; Nigmatulina, Elena
European Journal of Mineralogy Volume 14 Number 4 (2002), p. 795 - 807
published: Jul 17, 2002
ArtNo. ESP147051404013, Price: 29.00 €
Individual grains of calcian fayalite and ferroan kirschsteinite, as well as fayalite-kirschsteinite intergrowths are observed in the groundmass of basic crystallised melts, or 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.%. 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.