Geosciences 2013, 3(4), 633-667; doi:10.3390/geosciences3040633
Article

Modification of the Continental Crust by Subduction Zone Magmatism and Vice-Versa: Across-Strike Geochemical Variations of Silicic Lavas from Individual Eruptive Centers in the Andean Central Volcanic Zone

Received: 2 May 2013; in revised form: 8 November 2013 / Accepted: 14 November 2013 / Published: 27 November 2013
(This article belongs to the Special Issue Continental Accretion and Evolution)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: To better understand the origin of across-strike K2O enrichments in silicic volcanic rocks from the Andean Central Volcanic Zone, we compare geochemical data for Quaternary volcanic rocks erupted from three well-characterized composite volcanoes situated along a southeast striking transect between 21° and 22° S latitude (Aucanquilcha, Ollagüe, and Uturuncu). At a given SiO2 content, lavas erupted with increasing distance from the arc front display systematically higher K2O, Rb, Th, Y, REE and HFSE contents; Rb/Sr ratios; and Sr isotopic ratios. In contrast, the lavas display systematically lower Al2O3, Na2O, Sr, and Ba contents; Ba/La, Ba/Zr, K/Rb, and Sr/Y ratios; Nd isotopic ratios; and more negative Eu anomalies toward the east. We suggest that silicic magmas along the arc front reflect melting of relatively young, mafic composition amphibolitic source rocks and that the mid- to deep-crust becomes increasingly older with a more felsic bulk composition in which residual mineralogies are progressively more feldspar-rich toward the east. Collectively, these data suggest the continental crust becomes strongly hybridized beneath frontal arc localities due to protracted intrusion of primary, mantle-derived basaltic magmas with a diminishing effect behind the arc front because of smaller degrees of mantle partial melting and primary melt generation.
Keywords: across-strike geochemical variation; Central Volcanic Zone; Aucanquilcha; Ollagüe; Uturuncu
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MDPI and ACS Style

Michelfelder, G.S.; Feeley, T.C.; Wilder, A.D.; Klemetti, E.W. Modification of the Continental Crust by Subduction Zone Magmatism and Vice-Versa: Across-Strike Geochemical Variations of Silicic Lavas from Individual Eruptive Centers in the Andean Central Volcanic Zone. Geosciences 2013, 3, 633-667.

AMA Style

Michelfelder GS, Feeley TC, Wilder AD, Klemetti EW. Modification of the Continental Crust by Subduction Zone Magmatism and Vice-Versa: Across-Strike Geochemical Variations of Silicic Lavas from Individual Eruptive Centers in the Andean Central Volcanic Zone. Geosciences. 2013; 3(4):633-667.

Chicago/Turabian Style

Michelfelder, Gary S.; Feeley, Todd C.; Wilder, Alicia D.; Klemetti, Erik W. 2013. "Modification of the Continental Crust by Subduction Zone Magmatism and Vice-Versa: Across-Strike Geochemical Variations of Silicic Lavas from Individual Eruptive Centers in the Andean Central Volcanic Zone." Geosciences 3, no. 4: 633-667.

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