Fosfohedyfán z opuštěného železnorudného ložiska Hraničná (Slezsko, Česká republika)

Abstract

Abandoned iron skarn deposit Hraničná is located 16 km NW of Jeseník, Silesia, Czech Republic. It is situated in the Staré Město Crystalline Complex, belt of high grade metamorphic rocks, which suppose to be a meta-ophiolite of the initial Cambro-Ordovican rifting. The deposit itself is formed by two stratiform magnetite-hematite bands within the marbles and quartz-rich biotite gneisses. Marbles containing silicates are rich in Zn and Pb and give evidence for sedimentary of volcanosedimentary origin of the ore accumulation. We collected several samples at the adit and +20 m levels of the mine which yielded phosphohedyphane. Mineral forms irregular aggregates up to 100 μm within the calcite-dolomite-magnetite skarn. Its average chemical formula from 7 WDS spots is (Ca2.07Sr0.03Ba0.01Mg0.02Pb3.23Zn0.01Fe0.09Al0.01)Σ5.47[(PO4)2.53(AsO4)0.03(SO3)0.01(SiO4)0.24]Σ2.81[Cl1.05F0.20]Σ1.25 based on 13 O+Cl+F. Use of the normalization to Ca1 + Ca2 = 5 and employing the charge balance could lead to the possible presence of (CO3)2- up to 0.60 apfu, resp. 3.61 hm. % CO2; this possible content do not have any effect on mineral classification. It is, therefore, fifth reported occurrence of this mineral in the territory of the Czech Republic and the Bohemian Massif.