『Abstract
　This work is part of the project study for a road tunnel bypassing the town of Genova and was aimed at evaluating the amount of asbestos fibres in the metaophiolites belonging to the Voltri Group and the Sestri-Voltaggio Zone (Liguria, Northern Italy). The 85 studied rock samples (mainly mafic and ultramafic rocks) derive from exposed outcrops and prospecting boreholes. The study of field relations and petrographic/microtextural investigations under the optical microscope allowed for the identification and characterisation of asbestos-bearing settings and lithotypes. Mineralogy and concentration of asbestos fibres in powdered specimens were determined by means of a scanning electron microscope equipped with an energy-dispersive X-ray spectroscopy device. These investigations were combined with petrography on thin-section, X-ray diffraction analysis and phase contrast optical microscopy on rock powders. Mafic and ultramafic rocks commonly contain asbestos in concentrations below 1,000 mg/kg (considered as the contamination threshold under Italian law). However, the fibre concentration raises abruptly within localised zones, where the metaophiolite sequences were involved into late ductile to brittle tectono-metamorphic events. Two groups of asbestos-bearing settings have been so far identified in the area: (a) fracture networks within serpentinites (dominated by fibrous chrysotile), and (b) boudins of chlorite-tremolite schists, likely deriving from dynamic recrystallisation of mafic rocks under greenschist facies conditions (dominated by fibrous amphibole). Even considering the low volumetric incidence of these settings (metres to few tens of metres), their high asbestos content locally controls the total fibre amount in the excavation products, thus requiring special prevention measures during excavation, management and final storage of the contaminated debris.

Keywords: Asbestos fibres; Metaophiolite; Voltri Group; Tunnel debris』

Introduction
Approach and problems
Analytical methods
　XRD and PCM analyses
　SEM-EDS analyses
Geological setting
　Voltri Group
　Sestri-Noltaggio Zone and Apennine Flysched
Petrography and asbestos content
　Ultramafic rocks of the Palmaro-Caffarella and Voltri Unit
　　Serpentinised peridotites
　　Serpentinite
　　Veins and fractures with serpentine filling
　Mafic rocks of the Palmaro-Caffarella and Voltri Unit
　　Prasinite
　　Metagabbro mylonites, tectonic breccias and cataclasites
　　Tremolite-chlorite schists
　Sediments, netasediments and metabasalts
Discussion
　Forecasting the asbestos-bearing levels on geological profiles
　　Genesis and occurrence of asbestos minerals
　　Localisation of the asbestos-bearing settings
　Total amount of fibres in the studied lithotypes
　Variables influencing the amount of asbestos fibres in the tunnel debris
Concluding remarks
Acknowledgments
References