The Andes

Part of the series Frontiers in Earth Sciences pp 459-474

Partial Melting in the Central Andean Crust: a Review of Geophysical, Petrophysical, and Petrologic Evidence

  • Frank R. SchillingAffiliated withDepartment 4 Chemie der Erde, GeoForschungsZentrum Potsdam
  • , Robert B. TrumbullAffiliated withDepartment 4 Chemie der Erde, GeoForschungsZentrum Potsdam
  • , Heinrich BrasseAffiliated withFachrichung Geophysik, Institut für Geologische Wissenschaften, Freie Universität Berlin
  • , Christian HaberlandAffiliated withInstitut für Geowissenschaften, Universität Potsdam
  • , Günter AschAffiliated withGeoForschungsZentrum Potsdam
  • , David BruhnAffiliated withGeoForschungsZentrum Potsdam
  • , Katrin MaiAffiliated withGeoForschungsZentrum Potsdam
  • , Volker HaakAffiliated withGeoForschungsZentrum Potsdam
  • , Peter Giese
    • , Miguel MuñozAffiliated with
    • , Juliane RamelowAffiliated withDepartment 4 Chemie der Erde, GeoForschungsZentrum Potsdam
    • , Andreas RietbrockAffiliated withDepartment of Earth and Ocean Sciences, University of Liverpool
    • , Edgar RicaldiAffiliated withDepartamento de Física, Universidad Mayor de San Andrés
    • , Tim VietorAffiliated withGeoForschungsZentrum Potsdam

* Final gross prices may vary according to local VAT.

Get Access


The thickened crust of the Central Andes is characterized by several first-order geophysical anomalies that seem to reflect the presence of partial melts. Magnetotelluric and geomagnetic deep-sounding studies in Northern Chile have revealed a high conductivity zone (HCZ) beneath the Altiplano Plateau and the Western Cordillera, which is extreme both in terms of its size and integrated conductivity of > 20000 Siemens. Furthermore, this region is characterized by an extremely high seismic attenuation and reduced seismic velocity. The interrelation between the different petrophysical observations, in combination with petrological and heat-flow density studies, strongly indicates a huge area of partially molten rocks that is possibly topped with a thin, saline fluid film. The average melt fraction is deduced to be ∼20 vol.%, which agrees with typical values deduced from eroded migmatites. Based on the distribution and geochemical composition of Pliocene to Quaternary silicic ignimbrites in this area, this zone is thought to be dominated by crustally-derived rhyodacite melts with minor andesitic contribution. An interconnected melt distribution — typical for migmatites - would satisfy both the magnetotelluric and seismic observations. The high melt fraction in this mid-crustal zone should lead to strong weakening, which may be a main cause for the development of the flat topography of the Altiplano Plateau.