Der Peridotit-Harzburgit ultramafisches Körper (braunliche, Mitte) bei Alpe d’Albion, Gesero, Tessin.
Der Peridotit Körper bei Alpe d’Albion
Auf dem Weg zum Alpe d’Albion,
Die “Süd-Steil-Zone” wo die hoch metamorph Gesteine stehen tatsächlich sehr steil
Der ultramafisches Körper
Ein Blick auf den “spectakuläre zonierte hydrothermische Metarodingit und Olvin, Talc ± Anthophyllite and Pennine Adern”.
Zur Entwicklung:
“At Alpe Albion, the buff colors of several ultramafic lenses enclosed in the gneiss package stand out (note the flora change). The largest mass (~120×50 m), is harzburgitic, and its main assemblage is spinel- chlorite-enstatite-olivine.
Spectacularly zoned metarodingite veins and pods are abundant, as are hydrothermal veins with olivine, talc ± anthophyllite, and pennine. In the Central Alps, metarodingite veins are not rare in ultramafic rocks (Trommsdorff & Evans, 1980), and their observation is critical, for they indicate a metasomatic origin, linked to serpentinization of peridotite. Metarodingite in high-grade (spinel or garnet) peridotite thus demands a shallow hydration prior to subduction. SHRIMP dating of zircon from plagiogranite veins, indicates a Jurassic magmatic age (146 Ma, Stucky, 2001) and has been interpreted to show an origin from the Piemonte cean for the Alpe Albion ophiolite rocks.”
A polyphase evolution can be inferred:
- early (mantle-origin?) structures (dunite bands, with seams or aggregates of chromite, opx layers, or veins)
- intrusion of gabbroic and sparse plagiogranitic dykes, clinopyroxene veining
- hydration to serpentinite and associated metasomatism (rodingite formation)
- prograde metamorphic dehydration, isoclinal folding, metasomatism (blackwall formation), and late hydrothermal veining (antigorite+talc stable).
Zitiert aus dem “Guide Book to Field Trip B9″, 32nd Intl. Geological Congress
THERMO - MECHANICAL EVOLUTION OF THE ALPINE BELT, FROM THE ENGADINE WINDOW TO THE MATTERHORN
G. Gosso, M. Engi, F. Koller, J.M. Lardeaux, R. Oberhaensli, M.I. Spalla