Original paper

Indialite-rich paralava from a coalmine waste-dump, Sosnowiec, Poland

Gawęda, Aleksandra; Janeczek, Janusz; Kierepka, Mirosław; Kądziołko-Gaweł, Mariola; Krzykawski, Tomasz

Abstract

High-temperature (>1000 °C) melting and pyrometamorphism of Carboniferous psammitic-pelitic rocks caused by spontaneous combustion of coal in a coal mine waste dump, Sosnowiec, Poland, produced paralava and clinker. Local differences in oxygen fugacity, melt density and viscosity led to the formation of two varieties of paralavas both with andesitic composition: reduced (dark grey) and oxidized (red). Abundant Fe-rich idiomorphic indialite (XFe = 0.47–0.63) occurs in reduced paralava together with spinel, magnetite, hematite, rare phosphides, minor Fe-rich sapphirine and relic pyrite, monazite, xenotime, and zircon. Only few acicular crystals of indialite, skeletal spinel, and hematite occur in the oxidized paralava in addition to abundant partially resorbed quartz inherited from the sedimentary protolith. Partial melting of monazite under reducing conditions did not reset its U-Th-Pb ages despite mobilization of P and subsequent precipitation of secondary (Fe, Mn, Mg, Ca)-phosphides. Fractional crystallization combined with redox conditions was a major mechanism controlling mineral and chemical compositions of paralava.

Keywords

indialiteoxygen fugacityparalavapyrometamorphism