Usseaux ovardite outcrops, Usseaux, Metropolitan City of Turin, Piedmont, Italyi

Regional Level Types
Usseaux ovardite outcrops	Group of Outcrops
Usseaux	Commune
Metropolitan City of Turin	Metropolitan City
Piedmont	Region
Italy	- not defined -

Two ovardite [*] outcrops located near Usseaux.

An ovarditizited crossite schist crops out 300 m NW of Usseaux (see coordinates) in a section of the Schistes lustrés unit. Underneath micaschists a schistose serpentinite is situated. At the contact with underlying crossite-prasinite a tremolite-chlorite schist occurs. The crossite in the prasinite is rigorously oriented and fairly heavily altered into chlorite, except in a vein where crossite is enclosed by apatite. Apart from crossite this rock consists principally of albite and chlorite, but without the characteristic ovardite texture. Below the prasinite lies a layer that contains blocks of crossite schist that are embedded in a matrix of ovardite. Both components of this association exhibit the ovoid ovardite texture. Ellipsoidal lenses of serpentinite, embedded in talc schist, constitute an additional component of this layer.

At another locality near the village of Usseaux a monomictic ovardite breccia occurs. It consists of foliated ovardite fragments set in a coarse-grained,
randomly oriented albite-chlorite-quartz matrix.


Note [*]: Ovardite is a metabasic rock closely affiliated with the characteristically Alpine prasinite family. The name ovardite was coined by Strüver in 1873 for rocks from Torre d'Ovarda between Ala and Viù valleys (Piedmont). Its principal constituents are albite and chlorite, which may be accompanied by considerable amounts of calcite or quartz, and by a selection of minerals typical of the prasinite, blueschist and eclogite families. Their albite metablasts are characteristically ovoid in shape and frequently poiciloblastic, enclosing all other constituents of the rock.

References

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