Rio di Valle, Calizzano, Savona Province, Liguria, Italyi

Regional Level Types
Rio di Valle	Alluvials
Calizzano	Commune
Savona Province	Province
Liguria	Region
Italy	Country

Rio di Valle is a small stream that cuts through multiple lithotypes, the most abundant of which is the Monte Spinarda amphibolite. Along the riverbed, clasts of amphibolite are abundant. In addition to amphibolite clasts, elements of Mereta paragneiss, Bardineto orthogneiss, Vetria orthogneiss, and, more rarely, erratics from the Eze Formation can also be found.
The Monte Spinarda amphibolites originated from a basaltic protolith of Middle to Upper Cambrian age, as inferred from pre-Alpine deformation and their association with granitoids. These amphibolites have undergone two pre-Alpine metamorphic events in amphibolite facies, associated with Paleozoic foliations, and were later overprinted by Alpine metamorphism in greenschist facies.

The first pre-Alpine paragenesis is represented by hornblende (I) + garnet + plagioclase + rutile and plagioclase (An > 30) + diopside + clinozoisite + rutile. The second pre-Alpine paragenesis includes hornblende (II) + oligoclase (An ~25) ± clinozoisite ± biotite + titanite. The Alpine metamorphic overprint in greenschist facies is characterized by actinolite, epidote, and chlorite.

Rare relicts of eclogite can be found within the Monte Spinarda amphibolites. Their paragenesis consists of omphacite (Jd40–45), garnet (Alm30–40, Grs15–45, Prp3–10, Adr10–20, Sps1–10), zoisite, and rutile. Less frequently, granulitic bands are associated with the eclogites, composed of garnet, orthopyroxene, plagioclase, and clinopyroxene.

The Alpine metamorphic overprint on both eclogites and granulites is expressed through partial chloritization of garnet rims and the overgrowth of actinolite + albite at the expense of clinopyroxene and plagioclase.

Other Regions, Features and Areas containing this locality

References