Titanium and barium incorporation into the phyllosilicate phases: The example of phlogopite-kinoshitalite solid solution

Abstract
Extremely high abundances of BaO (up to 21.46 wt. % ) and TiO₂ (up to 13.85 wt. % ) are reported from brown phlogopite in calcite carbonatite inclusions from Jbel Saghro, Anti-Atlas Morocco. The substitution of Ba into the phlogopite structure can be explained by the scheme ^[12]Ba + ^[4]Al ^[12]K + ^[4]Si. At least 50 % of the K on the interlayer sites of phlogopites from Saghro is replaced by Ba. The incorporation of Ba into phlogopite allow the occurence of kinochitalite phases. Al compensates for tetrahedral Si deficiencies, and Ti is probably limited to octahedral substitution for Mg and Fe. A substitution scheme of the type Ba²⁺ + 2Ti⁴⁺ + 3Al K⁺ + 3(Mg, Fe)²⁺ + 3Si⁴⁺ is proposed.