Asbestos nucleation and concentration in rocks are mostly associated with mechanisms of fibre formation, combined with the water-dependent mineralogical alteration produced during serpentinisation of ultramafic masses. Very little is known about the structural settings and tectonic histories that influence and control asbestos occurrence in non-serpentinised rocks, which are diffusely embedded within tectonised ophiolitic suites. Focussing on a case history provided by a tectonised metagabbro from the Ligurian Alps (northern Italy), a multiscale structural-petrographical approach is used to investigate the relationships between rock fabric and fibrous amphibole growth within the metagabbro. Meso- to micro-structural observations are used to document the role of structurally controlled fluid-rock interactions in localising the fibrous amphibole growth during ductile-to-brittle shearing (mylonitic foliation to shear veins). A qualitative structural scenario is here provided for illustrating the growth of asbestos amphiboles in shear veins during the progression of shear deformation towards semi-brittle rheological conditions. The mechanisms of structurally controlled growth of fibrous amphibole in non-serpentinised rocks imply an examination of the tectonic boundary conditions that are at the origin of the asbestos concentration in ophiolitic rocks involved in orogenic belt construction.

Rossetti, F. (2019). Structurally controlled growth of fibrous amphibole in tectonised metagabbro: constraints on asbestos concentration in non-serpentinised rocks. JOURNAL OF THE GEOLOGICAL SOCIETY [10.1144/jgs2018-235].

Structurally controlled growth of fibrous amphibole in tectonised metagabbro: constraints on asbestos concentration in non-serpentinised rocks

federico rossetti
2019-01-01

Abstract

Asbestos nucleation and concentration in rocks are mostly associated with mechanisms of fibre formation, combined with the water-dependent mineralogical alteration produced during serpentinisation of ultramafic masses. Very little is known about the structural settings and tectonic histories that influence and control asbestos occurrence in non-serpentinised rocks, which are diffusely embedded within tectonised ophiolitic suites. Focussing on a case history provided by a tectonised metagabbro from the Ligurian Alps (northern Italy), a multiscale structural-petrographical approach is used to investigate the relationships between rock fabric and fibrous amphibole growth within the metagabbro. Meso- to micro-structural observations are used to document the role of structurally controlled fluid-rock interactions in localising the fibrous amphibole growth during ductile-to-brittle shearing (mylonitic foliation to shear veins). A qualitative structural scenario is here provided for illustrating the growth of asbestos amphiboles in shear veins during the progression of shear deformation towards semi-brittle rheological conditions. The mechanisms of structurally controlled growth of fibrous amphibole in non-serpentinised rocks imply an examination of the tectonic boundary conditions that are at the origin of the asbestos concentration in ophiolitic rocks involved in orogenic belt construction.
2019
Rossetti, F. (2019). Structurally controlled growth of fibrous amphibole in tectonised metagabbro: constraints on asbestos concentration in non-serpentinised rocks. JOURNAL OF THE GEOLOGICAL SOCIETY [10.1144/jgs2018-235].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11590/355279
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