The first cave occurrence of orpiment (As₂S₃) from the sulfuric acid caves of Aghia Paraskevi (Kassandra Peninsula, N. Greece)

Authors

Georgios Lazaridis, Department of Geology, Aristotle University of Thessaloniki, Thessaloniki, GR-54124, GreeceFollow
Vasilios Melfos, Department of Mineralogy, Petrology and Economic Geology, Aristotle University of Thessaloniki, Thessaloniki, GR-54124, GreeceFollow
Lambrini Papadopoulou, Department of Mineralogy, Petrology and Economic Geology, Aristotle University of Thessaloniki, Thessaloniki, GR-54124, Greece

Abstract

Orpiment, tamarugite and pickeringite occur in close association above the surface of thermal water cave pools in the active sulfuric acid caves of Aghia Paraskevi on the Kassandra peninsula, northern Greece. Gypsum also occurs as small interstitial crystals or encrustations. Orpiment is of high significance since it has not previously been reported as a cave mineral. In addition, tamarugite and pickeringite rarely occur in karst caves. Water from a borehole and a spring is of Na-Cl type and contains traces of CO₂ and H₂S. The B/Cl ratios indicate seawater participation with a possible mixing with geothermal water of meteoric origin. Oxidation of fumarolic H₂S and incorporation of seawater is a possible cause for the deposition of tamarugite. Orpiment accumulated from vapors under sub-aerial conditions at low temperatures in acidic conditions through an evaporation-condensation process. Fluid cooling and/or acidification of the solution resulting from H₂S oxidation were responsible for orpiment precipitation. Oxidation of H₂S to sulfuric acid dissolved the limestone bedrock and deposited gypsum.

DOI

http://dx.doi.org/10.5038/1827-806X.40.2.6

Recommended Citation

Lazaridis, Georgios; Vasilios Melfos; and Lambrini Papadopoulou. 2011. The first cave occurrence of orpiment (As₂S₃) from the sulfuric acid caves of Aghia Paraskevi (Kassandra Peninsula, N. Greece). International Journal of Speleology, 40: 133-139.
Available at: https://digitalcommons.usf.edu/ijs/vol40/iss2/6