Scisti dei Laghi
Darstellung und Status
- Farbe CMYK
- (0%,0%,0%,100%)
- Rang
- lithostratigraphische Einheit
- Gebrauch
- Element ist in Gebrauch
- Status
- informeller Begriff
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Scisti dei Laghi = Giumello Gneise (Boriani et al. 1990, Dal Piaz et al. 1992a)
Hierarchie und Abfolge
- Hangendes
Alter
- Alter Top
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- Frühes Paläozoikum
- Alter Basis
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- Frühes Paläozoikum
Referenzen
- Erstdefinition
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(1990) :
The evolution of the "Serie dei Laghi" (Strona-Ceneri and Scisti dei Laghi): the upper component of the Ivrea-Verbano crustal section; Southern Alps, North Italy and Ticino, Switzerland. Tectonophysics 182, 103-118
The Scìsti dei Laghi occur over a large area in the Lago d'Orta - southern Lago Maggiore, Verbania and Luino regions. East of Luino. the area of occurrence becomes narrower, due to the pronouneed southward bend of the whole Serie dei Laghi in the Ponte Tresa zone and because of the intersection of the Val Colla-Cremosina fault system. In the Swiss literature. the Scisti dei Laghi are called "Giumello Gneise" (Reinhard. 1964) and are included in the comprehensive "Ceneri Zone" (now Strona-Ceneri Zone; R. Schmid, 1968). They have also been recognized in the Gambarogno area (Borghi. 1987) and in Val Cannobina in the M. Riga Unit (Boriani et aL 1977; unpublished data). If these two attributions are correct, the Scisti dei Laghi are also present in the refolded northern limb of the M. Ceneri syncline (Fig. 2b).
The Scisti dei Laghi mostly consist of amphibolite facies micaschists and paragneisses (Boriani et al.. 1977), locally reequilibrated under greenschist facies conditions. In outcrop they show typical quartz rods and rusty weathering. The most widespread minerai association is quartz, plagioclase (20% An). white mica, biotite and porphyroblasts of garnet, kyanite (surrounded by coronitic margarite) and staurolite. The porphyroblasts are syn- to postkinematic with respect to the main foliation. Garnet also shows synkinematic rotational textures in its inner parts (Boriani, 1970a). Accessory minerals are apatite. zircon, opaques and tourmaline.
The Scisti dei Laghi are the polymetamorphic product of pelitic-arenaceous sediments: their age of sedimentation is unknown. The Sr model age of the overlying Strona-Ceneri is from the Late Proterozoic to Early Paleozoic (700-500 Ma: Hunziker and Zingg. 1980).