Abstract:
Analytical revision of 106 microprobe and chemical analyses of Mg-Fc micas of the well known Talnakh ore deposit has shown that nearly all of them belong to the phlogopitc mineral species, according to the up-to-date classification of this mineral group. With general similarity of their chemical composition, micas from picritic gabbro-dolcrites of Vcrkhnetalnakhskaya intrusion arc distinguished by the lower fcrruginosity and lower content of halogens relatively to micas from taxitie gabbro-dolcrites. It is regarded as a characteristic peculiarity of the Talnakh deposit micas that in taxitie gabbro-doleritcs they contain considerably more halogens than in picritic rocks. Micas connected with massive sulfide ores are enriched there in chlorine, as well as the higher concentrations of fluorine arc typical for micas in zones of the poor-in-sulfidc platinum-bearing mineralization. Formation of micas took place in the similar acidity-alkalinity conditions. One more peculiarity of Talnakh micas is their forming at the high oxidizing potential - nearly two times higher than an average oxidizing potential typical for basic rocks (Korikovsky, 1969). Increase of fcrruginousity in composition of those micas is accompanied by decrease of the Ti02 content, which may be related to lowering temperature of the mica-forming process.