Geological structure and petrology of the Late Cretaceous Chelopech volcano, Srednogorie magmatic zone

Abstract

The Chelopech volcano is the host of one of the largest Au-Cu deposits in Europe. The volcano, part of the Srednogorie Late Cretaceous island arc includes three phases: dome-like bodies (andesites and latites to trachydacites), lava to agglomerate flows (andesites, latites, dacites to trachydacites) and a lava breccia neck (andesites to shoshonites and latites). The age of the volcano is probably Turonian. The volcanic rocks are porphyric with plagioclase and amphibole phenocrysts, rarely quartz (in the dome-like bodies) and biotite. The groundmass is microlitic. The lava flows contain fully crystallized fine grained inclusions with more basic compositions indicating mingling between two parental magmas. The chemical evolution from more acid to more basic lavas, and the absence of an Eu anomaly probably indicate a chemically zoned magmatic chamber. The trace element content is similar to that of the active continental margin (Andean type). Sr isotopic compositions display a small range between 0.7049 and 0.7054 (corrected for 90 Ma)