Along- and Across-Arc Variations in the Southern Volcanic Zone, Chile

Jacques, Guillaume, Hoernle, Kaj A., Wehrmann, Heidi, Garbe-Schönberg, Dieter, van den Bogaard, Paul, Hauff, Folkmar and Lara, L. (2010) Along- and Across-Arc Variations in the Southern Volcanic Zone, Chile [Talk] In: SFB 574 Subduction Workshop, 04.-07.11.2010, Pucon, Chile.

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We present new trace element and isotope data from olivine-bearing volcanic rocks along the volcanic front of the Southern Volcanic Zone (SVZ) in Chile and in the backarc in Argentina. Samples from the volcanic front (VF) have
typical trace element signatures of subduction zone volcanic rocks, characterized by negative Nb and Ta anomalies and positive Pb anomalies on incompatible element diagrams. The northern Southern Volcanic Zone (NSVZ) samples from Tupungatito and San José have the most enriched
highly to moderately incompatible element ratios. We observe systematic variations in Sr and Nd isotopic compositions along the arc with the NSVZ showing the most enriched signatures, which is where the crust begins to
thicken significantly. The Pb isotopic composition of the VF appears to be dominated by continental-derived sediments present in the trench, rather than by Pacific pelagic sediment. The NSVZ samples require the presence of a
second enriched component that could reflect assimilation of lower crust or addition of lower crust through subduction erosion into the mantle wedge. Quaternary backarc samples in Argentina also show subduction signatures in their incompatible elements, but generally show lower fluid signatures than the VF samples, consistent with a decreasing influence of the subduction signature into the backarc. A third enriched component is required to explain the backarc samples, possibly reflecting an older arc signature in the lithosphere beneath the backarc.

Document Type: Conference or Workshop Item (Talk)
Keywords: Geodynamics; subduction; volcanic arc; Chile; volcanology
Research affiliation: OceanRep > GEOMAR
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS Magmatic and Hydrothermal Systems
OceanRep > SFB 574 > C2
OceanRep > SFB 574
Kiel University
Date Deposited: 10 Dec 2010 13:23
Last Modified: 23 Feb 2012 05:57

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