Geochemistry of Calc-alkaline Volcanic Rocks in relation to deep Structure of Ecuador and Southern Colombia
Vanková, Vera; Vanék, Jiri; Hanus, Václav; Fiala, Jiri; Chalupský, V.
published: Jan 1, 1993
ArtNo. ESP136000403001, Price: 19.00 €
Geochemistry of 104 samples of young volcanic rocks from the Western and Eastern Cordilleras of Ecuador and Southern Colombia was correlated with the deep structure of the region between parallels 1.5 °N and 2 °S and meridians 77 °W and 79 °W. The geochemical zonation of volcanic products was confirmed in dependence on the depth of the primary source of calc-alkaline magma in the partially melted part of the subduction zone. It was found that the contents of K2O, U, Th, Rb, Sr, Sa, Zr. V. TiO2 and P2O5 in andesites significantly increase with the depth of the upper boundary of the intermediate depth aseismic gap in the Andean Wadati-Senioff zone. The differences of the average element abundances for volcanic centres in Southern Colombia manifest that recent calc-alkaline volcanism in Ecuador and Southern Colombia is bound to different subducted lithospheric plates. The analysis of the geographical distribution of andesite and dacite samples with anomalous enrichment of both the compatible and incompatible elements in relation to the subduction-dependent pattern of deep-seated fracture zones showed that the geochemistry of volcanic products may be considerably influenced by the deep tectonic structure and does not need to be identical with the geochemistry of the primary magma.