Samaniego Pablo auteur aut IRD Martin H. auteur aut IRD Monzier Michel auteur aut IRD Robin C. auteur aut IRD Fornari Michel auteur aut IRD Eissen Jean-Pierre auteur aut IRD Cotten J. auteur aut IRD text journalArticle eng text/pdf reformatted digital access In the Northern Volcanic Zone of the Andes, the Cayambe Volcanic Complex consists of: (1) a basal, mostly effusive volcano, the Viejo Cayambe, whose lavas (andesites and subordinate dacites and rhyolites) are typically calc-alkaline; and (2) a younger, essentially dacitic, composite edifice, the Nevado Cayambe, characterized by lavas with adakitic signatures and explosive eruptive styles. The construction of Viejo Cayambe began > 1.1 Myr ago and ended at similar to 1.0 Ma. The young and still active Nevado Cayambe grew after a period of quiescence of about 0.6 Myr, from similar to 0.4 Ma to Holocene. Its complex history is divided into at least three large construction phases (Angureal cone, Main Summit cone and Secondary Summit cone) and comprises large pyroclastic events, debris avalanches, as well as periods of dome activity. Geochemical data indicate that fractional crystallization and crustal assimilation processes have a limited role in the genesis of each suite. On the contrary, field observations, and mineralogical and geochemical data show the increasing importance of magma mixing during the evolution of the volcanic complex. The adakitic signature of Nevado Cayambe magmas is related to partial melting of a basaltic source, which could be the lower crust or the subducted slab. However, reliable geophysical and geochemical evidence indicates that the source of adakitic component is the subducted slab. Thus, the Viejo Cayambe magmas are inferred to come from a mantle wedge source metasomatized by slab-derived melts (adakites), whereas the Nevado Cayambe magmas indicate a greater involvement of adakitic melts in their petrogenesis. This temporal evolution can be related to the presence of the subducted Carnegie Ridge, modifying the geothermal gradient along the Wadati-Benioff zone and favouring slab partial melting. specialized adakites Ar 40/Ar 39 dating Cayambe volcano Ecuador mantle metasomatism Andes 064 46 11 2225-2252 2005 0022-3530 https://www.documentation.ird.fr/hor/fdi:010044804 10.1093/petrology/egi053 0022-3530 [F B010044804] https://www.documentation.ird.fr/hor/fdi:010044804 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers13-12/010044804.pdf IRD - Base Horizon / Pleins textes 2006-03-29 2024-12-18 fdi:010044804 fre