Analysis of Mafic and Ultramafic Rocks in the Northern Ivrea-Verbano-Zone

Petrological and geochemical analysis of mafic and ultramafic rocks in the northern Ivrea-Verbano-Zone near Colloro

Student : Dominik Frei

Supervisor: Prof. Dr. Max W. Schmidt, Dr. Andrea Galli

The Ivrea-Verbano-Zone is one of the most studied area in the alps but the building history is already not well understood. In the mafic complex occured many mafic/ultramafic bodies of different sizes. The petrology was defined very well but there exist no geochemical data so far.
The target of this thesis was the detailed mapping of the mafic/ultramafic Basciot body near the village of Colloro, the geochemical characterization with samples of the single lithologies and afterwards the interpretation of all the data. The Basciot body had a concentric form where a peridotite built the centre of it. Around were clinopyroxenites, hornblendites and a calcmetasomatic zone. There was also a orthopyroxene-clinopyroxene-garnet gabbro as the host rock (gabbro of the mafic complex) and a second gabbro occur in the Basciot body. This gabbro is a clinopyroxene-garnet gabbro. The petrography displayed that the clinopyroxenite and the hornblendite in the body were in some samples similar to each other. The gabbros showed a difference in mineralogical composition. The geochemistry displayed, that the original magma had to have a tholeiitic composition. The mafic complex and the Basciot body had also a similar geochemical signal and therefore was one interpretation that the both (mafic complex and mafic/ultramafic body) ha the same geochemical system. Out of the concentric geometrical form, the lithologies in the body had to be cumulates. These cumulates could display a layering in it.