Mineralogical and geochemical (stable C and O isotopes) variability of marbles from the Moldanubian Zone (Bohemian Massif, Czech Republic): implications for provenance studies

Abstract

Metacarbonates of the Moldanubian Zone (Bohemian Massif, Czech Republic) were studied to obtain qualitative and quantitative mineralogical-petrographic as well as stable isotopic data for the purpose of stone provenance studies, potentially applicable in material research studies of cultural heritage artefacts. Twenty-six samples from twelve different historical quarries, as well as two samples from historical artefacts, were analysed by both mineralogical-petrographic and geochemical methods including: polarizing microscopy, cathodoluminescence, scanning electron microscopy with microanalysis, petrographic image analysis, powder X-ray diffraction, and isotope ratio mass spectrometry. The petrographic characteristics allowed for the discrimination of groups of (1) calcitic marbles, (2) dolomitic marbles, and (3) carbonate–silicate rocks. These groups exhibit characteristic features such as (1) the presence/abundance of major rock-forming minerals, (2) grain geometric characteristics (specifically, mean carbonate grain size and index of grain size homogeneity), and (3) the presence of specific accessory phases. The content of non-carbonate minerals, some rock fabric parameters, as well as the carbon and oxygen isotope data exhibited significant variability, even within a single quarry in the case of some impure marbles and carbonate–silicate rocks. Although the carbon and oxygen isotopic ranges displayed overlaps among the quarries studied, the isotopic signatures throughout the Moldanubian Zone allowed for discrimination of a group of white calcitic marbles with high carbon and oxygen depletion, as well as white dolomite–calcitic marble with higher carbon isotope values when compared with other marble resources of the Bohemian Massif. A combination of the isotopic signature with detailed mineralogical-petrographic characteristics seems to provide sufficient information for discrimination of the Moldanubian marbles from one another. The provenance of the Vrchotovy Janovice artefact is very probably from the Rabi quarry, among the Moldanubian marbles. The provenance of the artefact from the Prague Klementinum was not definitively assigned; however, the Nehodiv quarry was considered its probable source locality.