Original paper

Potassian hastingsite and potassichastingsite from garnet hedenbergite skarn at Vlastejovice, Czech Republic

Žáček, Vladimír


Potassichastingsite (3.05 wt. % K2O) occurs along with K-rich hastingsite (∼2.10 wt. % K2O) as large phenocrysts in metasomatic rims of pegmatite dykes penetrating Ca-Fe skarn at Vlastějovice, in the Variscan amphibolite - facies terrain of the Moldanubian Zone, Bohemian Massif, Czech Republic. The skarn is characterized by the high f (O2) assemblage of grossularite - andradite garnet, Fe3+ - enriched hedenbergite, magnetite, and epidote. Amphibole is characterized by Fe3+ > VIAl (Fe3+ 0.80 to 1.07 apfu, VIAl 0.30 to 0.38 apfu), high XFe (0.83 to 0.72) and low X-site vacancies (0.09 to 0.22). The concentrations of Li, Sr, Rb and Ba are non-essential, and other trace element contents are generally low. Due to the high K content (up to 0.62 apfu) it corresponds to potassichastingsite or potassian hastingsite. The OH content ranges from 1.60 to 1.82 apfu, F from 0.17 to 0.33 apfu, but Cl only from 0.03 to 0.06 apfu. Thus this amphibole belongs to most K-rich chlorine-poor hastingsites reported: (K0.62Na0.28)0.87 (Ca1.95Na0.05)2.00 (Fe2+2.79Mg0.92Mn0.03Fe3+0.80Ti0.05Al0.38)4.96 (Si5.98Al2.02)8.00 O22.05(OH1.71F0.18Cl0.06)1.95.


potassichastingsiteskarnvlastejovicebohemian massifczech republic