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| Titel |
Controls on the location of arc volcanoes: an Andean study |
| VerfasserIn |
Erin Scott, Mark B. Allen, Kenneth J. W. McCaffrey, Colin G. Macpherson, Jon P. Davidson, Christopher Saville |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250122397
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| Publikation (Nr.) |
 EGU/EGU2016-1421.pdf |
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| Zusammenfassung |
| Depth corrected data of earthquake hypocentres from South America are used to generate
new models of depth to the subducting Nazca slab. This new slab model shows a general
correlation between the 100 km depth to the slab, the western edge of the Altiplano-Puna
Plateau (defined by the 3500 m elevation contour) and the frontal volcanic arc. Across the
entire Altiplano-Puna Plateau, volcanic centres are found to be either at or above the 3500 m
critical elevation contour, which also defines the cut off for seismogenic thrusting. Normal
faults are only found above this critical elevation contour, suggesting that there may be a
change in the stress regime associated with high elevations in the plateau. The Salar de
Atacama basin (23-24oS) defines a major break in topography on the west side of the
Puna Plateau. Here, the volcanism deviates around the eastern edge of the basin,
approximately 80 km inland from the general trend of the arc, remaining above the 3500 m
elevation contour. The volcanoes bordering the Salar de Atacama have a depth to
slab approximately 30 km deeper than those in the adjacent arc segment 200 km
to the north of the basin. Across this distance there is no significant difference in
subduction parameters such as the slab dip, subduction rate and age of the oceanic
plate entering the trench. It is likely, therefore, that melt forms at the same depth
in both locations, as the factors affecting the melt source are constant. However,
in the case of the Salar de Atacama region, magma is diverted to the east due to
preferential emplacement under the higher elevations of the plateau. We suggest that
although mantle and subduction processes have a primary control on the location of arc
volcanoes, shaping the general trend of the arc, they cannot explain anomalies from the
trend. Such anomalies, such as the arc deviation around the Atacama basin, can be
explained by the influence of structures and stress regime within the overriding plate. |
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