DOI: http://dx.doi.org/10.5027/andgeoV19n1-a03

Variaciones geoquimicas, locales y regionales, en el frente volcanico cuaternario de los Andes centrales (17°30'-22°00'S), norte de Chile

Gerhardt Worner, Leopoldo Lopez-Escobar, Stephen Moorbath, Susan Horn, Jürgen Entenmann, Russel S. Harmon , Jon D. Davidson

Abstract


ABSTRACT. Local and regional geochemical variations in the quaternary volcanic front of the central Andes (17°30'-22°00'S), northern Chile. Geochemical data, obtained in samples from the 17°30'-22°00'S sector of the Quaternary volcanic front of the Central Andes, suggest a significant involvement of the continental crust in the magmagenesis of this region. A regional segmentation in the composition of the volcanic centers and a gap in the Quaternary volcanism between 19°10' and 20°40'S (Altos de Pica zone) are important features in this Andean sector. Centers north of the Altos de Pica (16°00'-19"09'S) differ from those south of it (20"40'-28°00'S) in the abundance of incompatible trace elements and in the behaviour of the Sr- and Pb- isotopic ratios with degree of differentiation. Since the mean age and composition of the crust are the only important geophysical variables between 17°30' and 22°00'S, the regional segmentation seems to reflect an interaction of subcrustal magmas with crust of different age and composition. This interaction is interpreted as a MASH-type process occurring in the lower crust. Local variations in magma composition suggest a MASH zone that evolved in response to crustal thickening during the lower to middle Miocene. The isotopic composition of southern monogenetic con e lavas is similar to those of the northern region lavas and is interpreted to result from interaction of subcrustal magmas with northern type lower crust extending southward at depth.

How to cite this article Worner, G., Lopez-Escobar, L., Moorbath, S., Horn, S., Entenmann, J., Harmon , R., and Davidson, J., 1992, Variaciones geoquimicas, locales y regionales, en el frente volcanico cuaternario de los Andes centrales (17°30'-22°00'S), norte de Chile: Revista Geológica de Chile v. 19, no. 1, p. 37-56., doi:http://dx.doi.org/10.5027/andgeoV19n1-a03