Quaternary volcanism in Deception Island (Antarctica): South Shetland Trench subduction-related signature in the Bransfield Basin backarc domain

• Main Authors: Gale, C., Ubide, T., Lago, M., Gil-Imaz, A., Gil-Pena, I., Galindo-Zaldivar, J., Rey, J., Maestro, A., Lopez-Martinez, J.
• Format: Article in Journal/Newspaper
• Language: English; Spanish
• Published: Instituto Geologico y Minero de Espana 2014
• Subjects: Bransfield strait; Cenozoic; Magmatism; South Shetland Islands; Volcanism; 1906 Geochemistry and Petrology; 1907 Geology; Bransfield Strait; Deception Island; South Shetland Trench; Antarc*; Antarctica
• Online Access: https://espace.library.uq.edu.au/view/UQ:411147

Deception Island shows a volcanism related to the Phoenix Plate subduction and roll-back under South Shetland Block in the present times. The development of the island is related to the evolution and collapse of a volcanic caldera, and this study is focused on the petrology, mineralogy and geochemistry of the post-caldera rocks. We have made a study of the lava flows, dikes and the youngest historic eruption in 1970. These rocks range from dacite to rhyolite and have a microporphyritic texture with olivine and minor clinopyroxene. A pre-caldera basaltic andesite has also been studied. It has a microporphyritic texture with clinopyroxene. The intermediate and acid compositions alternating in the volcanostratigraphic sequence suggest either mafic recharge events or melt extraction from different levels in the deep magmatic system. All the studied compositions share a subduction-related signature similar to other magmatics from the Bransfield Basin. However, compositional differences between pre-caldera and post-caldera rocks indicate a different magma source and depth of crystallisation. According to the geothermobarometric calculations the pre-caldera magmas started to crystallise at deeper levels (13.5-15 km) than the post-caldera magmas (6.2-7.8 km). Specifically, the postcaldera magmas indicate a smaller influence of the subducting slab in the southwestern part of the Bransfield Basin in respect to the available data from other sectors as well as the involvement of crustal contamination in the genesis of the magmas.