The `Carta Geologica della Valmalenco' (Montrasio et al., 2005) is the
result of a thirty five-year cooperation between ETH and University of
Zurich and the University and CNR-Italia at Milano. The map covers an
area of about 350 km(2) With the mapping having been carried out by
over fifty people, mostly as part of students' theses. The Valmalenco
area contains one of the largest ultramafic masses of the Alps, which
occurs together with a well preserved, Jurassic to Cretaceous ocean
floor suite. These units are sandwiched in between nappes derived from
the Adriatic microplate and the European plate. The ultramafic rocks
are of subcontinental origin and preserve on their top a Permian,
continental, crust-mantle transition. During Jurassic rifting these
rocks were exposed at the Adriatic margin of the Piemontese-Ligurian
ocean basin. Two orogenic cycles affected the Adriatic margin: the
first is related to Late Cretaceous nappe stacking, whereas the second
is due to the Tertiary continental collision. At the end of collision,
the Malenco rocks were, in their southwestern part, intruded by the
caic-alkaline, Oligocene, Bergell complex. The Bergell rocks present an
exceptionally rich variety of magmatic phenomena and a well-defined
contact aureole. The area affected by contact metamorphism is an
outstanding natural laboratory to study metamorphic and metasomatic
processes. Isograds of prograde metamorphism of serpentinite and of
ophicarbonate rocks were mapped for the first time in the Valmalenco,
and the results integrated into a consistent petrological model.