The First Occurrence of Asbestiform Magnesio-Riebeckite in Schists in the Frido Unit (Pollino Unesco Global Geopark, Southern Italy)

Abstract

In this paper, new mineralogical and petrographical data of asbestiform Magnesio-riebeckite from ophiolite cropping out in the Pollino Unesco Global Geopark (southern Italy) are presented. Magnesio-riebeckite schists with HP-LT index mineral assemblage recorded metamorphic events in blueschist facies in the Frido Unit. Previous toxicological studies showed that asbestiform Magnesio-riebeckite species exhibited high carcinogenicity in previous intraperitoneal injection experiments with rats. The results have been obtained using different analytical techniques such as X-ray fluorescence (XRF), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), and electron probe micro analysis (EPMA). Results show that all the samples contain fibrous Magnesio-riebeckite and/or prismatic, acicular crystals in aggregates. The concentration of elements in Magnesio-riebeckite crystals is: Na2O (4.12−6.26 wt%), MgO (8.22−10.87 wt%), FeO (19.07−23.81 wt%), SiO2 (52.05−56.06 wt%), CaO (1.12−4.53 wt%), Al2O3 (1.34−1.93 wt%), and MnO (0.10−0.34 wt%). Magnesio-riebeckite crystals are documented in the Pollino Unesco Global Geopark for the first time. For this reason, the aim of this paper is the characterization of Magnesio-riebeckite to improve the knowledge of this mineral in the studied area, because the release of fibers into the environment is dangerous for human health.

Keywords

• magnesio-riebeckite
• asbestos minerals
• schists
• blueschist facies
• Pollino Unesco Gobal Geopark