Geochemistry of Detrital Chromian Spinel as a Marker for Cenozoic Multistage Tectonic Evolution of the Alps

Dario Sciunnach (a)
(a) Department for the Environment, Energy and Sustainable Development, Regione Lombardia, Piazza Città di Lombardia, 1, 20124, Milan, Italy. E-mail: Dario_Sciunnach@regione.lombardia.it

In the Cenozoic sedimentary succession of Brianza (Western Lombardy Southern Alps), detrital transparent Cr-spinels are found at well-defined stratigraphic intervals (Lutetian and Serravallian). Distinct clusters based on Cr-spinel geochemistry reflect successive tectonic stages in the tectonic evolution of the Alps: during the Eocene, mantle xenoliths were dragged to the surface by basaltic-andesitic lavas sampling an harzburgite-dominated Supra-Subduction Zone, while during the Serravallian the exhumation path of obducted oceanic mantle lherzolites had been completed. A small population of Ni-rich Cr-magnetites is considered of extraterrestrial origin

Alps, Arenites, Cenozoic, Chromian Spinel, Provenance, Stratigraphy.