PRZEOBRAŻONE RYTMITY SIARCZKOWE W PIASKOWCU BIAŁEGO SPĄGOWCA Z KOPALNI RUDNA

Abstract

ALTERED RHYTHMIC SULPHIDE BANDS IN THE WEISSLIEGEND SANDSTONE IN THE RUDNA MINE (FORE-SUDETIC MONOCLINE, POLAND)Abstract. Two cross-sections of Weissliegend sandstones with copper sulphide rhythmic banding from the Rudna Mine were studied. Analyses were performed using optical polarizing (PLM) and scanning electron (SEM-EDS) microscopy and XRD. The rhythmites have different sulphide compositions and they have undergone different alterations. In the RZA cross-section, the rhythmites are composed of copper sulphides, mainly digenite, strongly altered to covellite and atacamite by secondary processes. Primary rhythmites were probably formed via a reaction between hydrogen sulphide from the overlying shale and copper-bearing solutions in the sandstone. Weathering and mining waters were probably responsible for extensive atacamite formation, although other possibilities are also considered. In the RGM cross-section, the rhythmites are composed of Cu–Fe sulphides (bornite and chalcopyrite) and pyrite. This distinct mineralogy may result from a reaction of hydrogen sulphide from the overlying shale with copper- and iron-bearing solutions. Dissolution of pyrite or iron monosulphides present in the sandstone could enrich the solutions in iron. Primary ore mineralization was overlapped by secondary mineralization of slightly different composition.