Sulphur and chlorine geochemistry of mafic to intermediate tephras from the Chilean Southern Volcanic Zone (33-43°S) compared with those from the Central American Volcanic Arc.

Wehrmann, Heidi, Hoernle, Kaj, Jacques, Guillaume, Garbe-Schönberg, Dieter, Schumann, Kai, Mahlke, Julia and Lara, Luis (2012) Sulphur and chlorine geochemistry of mafic to intermediate tephras from the Chilean Southern Volcanic Zone (33-43°S) compared with those from the Central American Volcanic Arc. [Poster] In: The Lübeck Retreat, Collaborative Research SFB 574 Volatiles and Fluids in Subduction Zones: Climate Feedback and Trigger Mechanisms for Natural Disasters. , 23.-25.05.2012, Lübeck . The Lübeck Retreat: final colloquium of SFB 574; May 23-25, 2012: program & abstracts. ; pp. 37-38 .

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Abstract

Here we present the first systematic investigation of volatile geochemistry along the Southern
Volcanic Zone (SVZ) of Chile. Holocene olivine-hosted melt inclusions in the most mafic tephras
sampled from 16 volcanoes along the volcanic front of the SVZ were analysed for pre-eruptive
sulphur, chlorine and major element contents. These results are combined with trace element
compositions of the host whole rocks. The highest fractionation-corrected gas contents occur in the
least-degassed melt inclusions from small peripheral cones from both the transitional and the
southern-central SVZ, reaching ~3000 μg/g S and 1400 μg/g Cl, while the lowest abundances of
~1000 μg/g S and ~600 μg/g Cl were found in the central SVZ at Volcán Lonquimay, Volcán Llaima,
and Volcán Villarrica. Chlorine co-varies with trace element indicators for the degree of melting and/or
source enrichment. The highest Cl enrichment is present in the melts with least degree melting,
underscoring its incompatible behaviour. The lowest Cl contents are found in high-degree melts from
the most depleted mantle sources. The size of the volcanic edifices correlates inversely with Cl
abundances in the melt.
In comparison with other subduction zones, the SVZ melt inclusions exhibit Cl abundances in the
same range as most of those from the Central American and those from the Marianas arcs. In
contrast, S concentrations are lower at the SVZ, with the exception of small peripheral cones of Los
Hornitos next to Cerro Azul, Cabeza de Vaca near Osorno, and Apagado. The lower S contents are
likely to be related to the generally more evolved nature of the SVZ lavas, compared to those from
Central America and the Marianas.

Document Type: Conference or Workshop Item (Poster)
Keywords: Geodynamics
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS Magmatic and Hydrothermal Systems
OceanRep > SFB 574 > B6
OceanRep > SFB 574 > C2
OceanRep > SFB 574
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Kiel University
Related URLs:
Date Deposited: 21 Sep 2012 11:20
Last Modified: 22 Sep 2012 03:56
URI: http://oceanrep.geomar.de/id/eprint/15339

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