Asbestos and other fibrous minerals contained in the Gimigliano-Mount Reventino Unit (Calabria Region, Southern Italy).

The study concerns the investigation on asbestos and other fibrous minerals in 25 specimens of serpentinites and metabasalts collected in the metaophiolitic sequence of the Gimigliano-Mount Reventino Unit (GMRU). For this purpose, mineralogical studies of serpentinites and metabasalts are currently being carried out by PLM, XRPD, SEM/EDS, TG/DSC, TEM/EDS investigations. PLM and XRPD studies show that metabasalts, which are either massive and banded, consist of (in order of decreasing abundance): chlorite, epidote, albite, amphiboles (actinolite, tremolite and riebeckite), quartz, muscovite, calcite and serpentine. Serpentinite samples contain (in order of decreasing abundance): serpentine minerals, magnetite, tremolite, chlorite, calcite (this latter occurring as veins) and minor clay minerals. At the microscope scale serpentinites are characterised by the typical mesh texture, with pseudomorphs replacing olivine and bastitic texture on orthoand clino-pyroxenes, with rare relics in the inner portions. Moreover, widespread serpentine veins are characterised by fibres grown either at low angle (“slip” serpentine) and perpendicular (“cross” serpentine) respect to the vein elongation. SEM and TEM/EDS investigations show asbestos tremolite, asbestos actinolite, asbestiform and massive antigorite, lizardite and chrysotile. Chrysotile shows mainly the classical cylindrical fibres, antigorite is characterized by lamellar and fibrous shape, lizardite exhibits only plate-like morphology. At the SEM observation, the tremolite and actinolite fibres appear thin, rigid and approximately 30 μm in length. The DSC patterns of all serpentinitic samples show: a main peak in a T range of 625-650 °C, due to the chrysotile breakdown; an endothermic peak in a T range of 697-765 °C, diagnostic of lizardite and antigorite. A sharp exothermic peak is recognised at 820-826 °C in all samples, which indicates the crystallization of forsterite. The DSC curve for metabasalt samples showed the characteristic endothermic peaks of serpentine minerals and tremolite-actinolite ranging from 612 to 643 °C and from 964 to 969 °C, respectively. Other investigations to deeply characterize the fibrous phases are going on.