The results of a research conducted during three years on the characterization of the white Apuan marbles and on the existing relationships between the microstructures and the physical characteristics of the marbles are presented. The examined samples come from Apuan quarries located in the Carrara and Arni basins and in the zones of Renara, Passo del Vestito, Isola Santa. Chemical, mineralogical, petrographical, physical and spectroscopic tests were carried out. The examined marbles show a notably homogeneous chemical-mineralogical composition: from the chemical point of view high CaO, small quantities of SiO2, Al2O3, Fe2O3, and negligible presence of trace elements were evidenced. Chemical analyses were also conducted through EPR, performed on a Bruker 200D spectrometer equipped with ST100/700 variable temperature assembly, interfaced with a Stelar software to a IBM-PC computer. EPR data were collected on powders in pure amorphous silica capillaries. The g-values were refined with reference to Mn-bearing sphalerite, as external standard. The petrographical observations put in evidence that the microfabric varies not only among different basins (es. basin of Arni and basin of Carrara), but also inside the same basin. This is the result of the complex tectonic-metamorphic evolution suffered by the Apuan marbles. Samples characterized by microstructures without orientation and straight grain boundaries up to terms characterized by strong orientation and lobate to strongly sutured grain boundaries were analysed. The study of the microstructural parameters was carried out through a software of image analysis that allows to quantify the mean granulometry, the granulometric distribution, the presence of preferential orientation and the shape of the grain boundaries. The microstructural parameters were plotted with the main physical characteristics of the white marbles: total open porosity, mesoporosity, pore size distribution, imbibition coefficient, trend of the imbibition curves obtained through total immersion and capillarity. Strong relationships were evidenced: marbles with granoblastic structure show higher total open porosity, an unimodal pore size distribution and a higher water imbibition capacity, while marble with xenoblastic structure are characterized by a smaller value of the total open porosity, a bimodal distribution of the porosimetric classes and a smaller water imbibition capacity.
Microfabric and physical characteristics of white Apuan marbles / Cantisani E.; Di Benedetto F.; Fratini F.; Malesani P.; Molli G.; Pecchioni E. - ELETTRONICO. - (2004), pp. 1-1. (Intervento presentato al convegno 32th IGC Florence Italy tenutosi a Firenze nel 20-28 Agosto 2004).
Microfabric and physical characteristics of white Apuan marbles
DI BENEDETTO, FRANCESCO;MALESANI, PIERGIORGIO;PECCHIONI, ELENA
2004
Abstract
The results of a research conducted during three years on the characterization of the white Apuan marbles and on the existing relationships between the microstructures and the physical characteristics of the marbles are presented. The examined samples come from Apuan quarries located in the Carrara and Arni basins and in the zones of Renara, Passo del Vestito, Isola Santa. Chemical, mineralogical, petrographical, physical and spectroscopic tests were carried out. The examined marbles show a notably homogeneous chemical-mineralogical composition: from the chemical point of view high CaO, small quantities of SiO2, Al2O3, Fe2O3, and negligible presence of trace elements were evidenced. Chemical analyses were also conducted through EPR, performed on a Bruker 200D spectrometer equipped with ST100/700 variable temperature assembly, interfaced with a Stelar software to a IBM-PC computer. EPR data were collected on powders in pure amorphous silica capillaries. The g-values were refined with reference to Mn-bearing sphalerite, as external standard. The petrographical observations put in evidence that the microfabric varies not only among different basins (es. basin of Arni and basin of Carrara), but also inside the same basin. This is the result of the complex tectonic-metamorphic evolution suffered by the Apuan marbles. Samples characterized by microstructures without orientation and straight grain boundaries up to terms characterized by strong orientation and lobate to strongly sutured grain boundaries were analysed. The study of the microstructural parameters was carried out through a software of image analysis that allows to quantify the mean granulometry, the granulometric distribution, the presence of preferential orientation and the shape of the grain boundaries. The microstructural parameters were plotted with the main physical characteristics of the white marbles: total open porosity, mesoporosity, pore size distribution, imbibition coefficient, trend of the imbibition curves obtained through total immersion and capillarity. Strong relationships were evidenced: marbles with granoblastic structure show higher total open porosity, an unimodal pore size distribution and a higher water imbibition capacity, while marble with xenoblastic structure are characterized by a smaller value of the total open porosity, a bimodal distribution of the porosimetric classes and a smaller water imbibition capacity.
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