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Geosciences, Volume 3, Issue 4 (December 2013) – 3 articles , Pages 616-667

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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
by Gary S. Michelfelder, Todd C. Feeley, Alicia D. Wilder and Erik W. Klemetti
Geosciences 2013, 3(4), 633-667; https://doi.org/10.3390/geosciences3040633 - 27 Nov 2013
Cited by 23 | Viewed by 8719
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° [...] Read more.
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. Full article
(This article belongs to the Special Issue Continental Accretion and Evolution)
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Response to Bonfiglio, L. Notes and Discussions on Marra, A.C. Evolution of Endemic Species, Ecological Interactions and Geographical Changes in an Insular Environment: A Case Study of Quaternary Mammals of Sicily (Italy, EU). Geosciences 2013, 3, 114–139.
by Antonella Cinzia Marra
Geosciences 2013, 3(4), 626-632; https://doi.org/10.3390/geosciences3040626 - 12 Nov 2013
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Abstract
In the following discussion, the author replies to the critical notes by Bonfiglio and demonstrates that they did not discredit the reliability and the accuracy of her paper [1]. Full article
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Notes and Discussions on Marra, A.C. Evolution of Endemic Species, Ecological Interactions and Geographical Changes in an Insular Environment: A Case Study of Quaternary Mammals of Sicily (Italy, EU). Geosciences 2013, 3, 114–139.
by Laura Bonfiglio
Geosciences 2013, 3(4), 616-625; https://doi.org/10.3390/geosciences3040616 - 12 Nov 2013
Cited by 2 | Viewed by 5630
Abstract
In her paper, A.C. Marra intends to review the current knowledge on Quaternary mammals of Sicily. As a review, the paper should have presented a clear, updated and rigorous picture of the chosen topic. Actually, most of the paper’s contents come from previous [...] Read more.
In her paper, A.C. Marra intends to review the current knowledge on Quaternary mammals of Sicily. As a review, the paper should have presented a clear, updated and rigorous picture of the chosen topic. Actually, most of the paper’s contents come from previous review papers (quoted with the numbers 1–6, 18, 19 and 50), most of which are dated. Above all, A.C. Marra overlooked recent important data concerning the species contained in the different faunal assemblages of Sicily, as well as previous data concerning the stratigraphy and datings of the faunal deposits. Full article
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