Geochemical signatures of tephras from Quaternary Antarctic Peninsula volcanoes Geoqu赤mica de tefras de volcanes Cuaternarios de la Pen赤nsula Ant芍rtica

作者：Stefan Kraus; Andrei Kurbatov; Martin Yates

来源：Andean Geology, 2013.

• Pleistoceno Tardio
• Holoceno
• Volcanismo explosivo
• Tefra
• Volcan de origen
• Huella geoquimica
• Peninsula Antartica
• Rift de Bransfield
• Rift de Larsen
• Late Pleistocene
• Holocene
• Explosive volcanism
• Tephra
• Source volcano identification
• Geochemical fingerprint
• Antarctic Peninsula
• Bransfield Rift
• Larsen Rift

In the northern Antarctic Peninsula area, at least 12 Late Plelstocene-Holocene volcanic centers could be potential sources of tephra layers in the region. We present unique geochemical fingerprints for ten of these volcanoes using major, trace, rare earth element, and isotope data from 95 samples of tephra and other eruption products. The volcanoes have predominantly basaltic and basaltic andesitic compositions. The Nb/Y ratio proves useful to distinguish between volcanic centers located on the eastern (Larsen Rift) and those situated on the western side (Bransfield Rift) of the Antarctic Peninsula. In addition, the Sr/Nb ratio (for samples with SiO2 %26lt;63 wt%), along with Sr/Y, Ba/La, Zr/Hf and Th/Nb are suitable to unequivocally characterize material erupted from every studied volcanic center. Microprobe analyses on volcanic glass show that the samples are generally very poor in K2O, and that glass from Bransfield Rift volcanoes is enriched in SiO2, while that of Larsen Rift volcanoes tends towards elevated alkali contents. We propose an algorithm for the identification of the source volcano of a given tephra layer using the new geochemical fingerprints. This will contribute to the development of a regional tephrochronological framework needed for future correlations of tephra in climate archives (e.g., marine, lacustrine and ice cores). En la parte norte de la Pen赤nsula Ant芍rtica existen, por lo menos, 12 centros volc芍nicos del Pleistoceno Tard赤o-Holoceno que podr赤an representar las fuentes de horizontes de tefra reconocidos en la regi車n. Se reportan aqu赤 an芍lisis qu赤micos de 10 de estos volcanes, que incluyen an芍lisis de elementos mayores, trazas, tierras raras y composici車n isot車pica de 95 muestras de tefra u otros productos eruptivos. Los volcanes tienen, en su mayor赤a, composici車n bas芍ltica a bas芍ltico-andes赤tica. Las razones Nb/Y resultan 迆tiles para distinguir entre centros volc芍nicos ubicados al lado oriental (Larsen Rift) de aquellos ubicados al lado occidental (Bransfield Rift) de la Pen赤nsula Ant芍rtica. Adicionalmente, las razones Sr/Nb (para muestras con SiO2 %26lt;63 wt%), Sr/Y, Ba/La, Zr/Hf y Th/Nb sirven para caracterizar los productos generados por cada centro volc芍nico. An芍lisis de microsonda en vidrio muestran que las rocas estudiadas tienen bajos contenidos de K2O, y que vidrios de rocas provenientes de volcanes ubicados en el rift de Bransfield son ricos en SiO2, mientras que las de volcanes del rift de Larsen tienden hac赤a contenidos elevados de 芍lcalis. Se propone un algoritmo para la identificaci車n del volc芍n de origen de un horizonte