Minerals of Pohorje marbles

In the Pohorje Mts, mostly outcrops of calcite marble can be found, which in places turn into dolomite marbles. The protolith carbonate rocks contained also detritical minerals, which remained unchanged or formed new minerals during metamorphosis. Minerals in the Pohorje marbles that can be seen as crystals with the naked eye or 10x magnifying loupe and with binocular microscope were investigated. With the aid of Raman microspectroscopy, SEM-EDS analysis and on the basis of morphological characteristics, the presence of 17 different minerals or group of minerals was confirmed. The most numerous and also the most significant were, apart from calcite, tremolite, diopside, grossular and epidote. For the first time, vesuvianite and scapolite were described in the Pohorje Mts. Particularly rich, as far as crystal faces are concerned, were the crystals of quartz that contained needle-like amphiboles. Other minerals that well supplemented the mineral paragenesis were different minerals of mica and chlorite group, feldspars, magnetite, titanite, pyrite and graphite. The determined mineral association revealed the mineral diversity of Pohorje marbles, offering us a new challenge for the investigation of the characteristics and conditions during the origin of this noble rock, which was highly esteemed already by the Romans, while today it is regaining its value and recognisability. GEOLOGIJA 56/1, 049-056, Ljubljana 2013 doi:10.5474/geologija.2013. 004 48 Miha JERSEK, Sabina KRAMAR, Simona SKOBE, Nina ZUPAN^I^ & Viljem PODGORSEK assemblages, and therefore accessory minerals, provide crucial information on temperature and pressure during metamorphism, i.e. metamorphic facies (Best, 2007). Some mineral species are particularly good traces since, alone, they may point to the provenance of the host marble (caPeDri et al., 2004; oriGlia et al., 2011; taelMan et al., 2012). For example, fluorite points at Anatolian marbles, in particular to Marmara, Mugla/Salkim, or Balikesir/Kocoglu; zoisite to Naxos, and rare earth-containing epidote to Mugla/Golkuc; aspidolite is unique to Marmara, whereas margarite occurs at Marmara and Samos, and paragonite at Marmara, Aydin and Iraklia. Plogopite occurs at Marmara and Mugla/Salkim among the Anatolian marbles, and at Thasos, Naxos, Paros and Penteli among the Greek marbles; it may be worth noting that phlogopite is absent from Carrara marble (caPeDri et al., 2004). By contrast, plagioclase is typical of Carrara and Aydin among the white marbles, and of Mani and Mugla/Golkuc among the red coloured marbles (caPeDri et al., 2004). On the other hand, some authors argue (lazzarini et al., 1980) that the accessory minerals themselves do not seem to have much diagnostic value owing to the wide distribution and frequent occurrences of common minerals like quartz, epidote and mica, and because of the absence of rare or special minerals. They may be used successfully in combination with other parameters for the characterisation of the marbles (caPeDri et al., 2004), e. g. geographical distribution as well as metamorphic history of the marble (Bucher & Frey, 2002). Within this study we focused only on determination of minerals, which are large enough to be seen macroscopically or with a 10x magnifying loupe.