Gas geochemistry as a tool to investigate the Earth's degassing through volcanic and seismic areas: The soul of the 8th International Conference on Gas Geochemistry

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• 作者：F. Italiano ; W. D'Aless ; ro ; M. Martelli
• 关键词：White Island ; Antarctica ; McMurdo Volcanic Group ; basanite– ; tephriphonolite ; tuff cones ; mantle and deep crustal nodules ; diffuse magmatism
• 刊名：Journal of Volcanology and Geothermal Research
• 出版年：2007
• 期刊代码：53_03770273
• 类别：ear
• 出版时间：15 August 2007
• 卷：165
• 期：1-2
• 页码：1-4
• 文件大小：119 K

摘要

White Island, Ross Sea, Antarctica is a Plio-Pleistocene basanite to tephriphonolite shield volcano, forming part of the Erebus Province, McMurdo Volcanic Group. Four new ⁴⁰Ar/³⁹Ar dates extend the age of surface volcanism from a previously determined 0.17 Ma to 5.05 ± 0.31 Ma. A U/Pb age on zircon in an anorthoclasite nodule extends White Island magmatism back to 7.65 ± 0.69 Ma.

Volcanism was predominantly subaerial with eruption of agglutinated spatter-clast breccias and lava flows from vents with a NNE structural alignment. An early phase of inferred subaqueous/subglacial activity formed pillow breccias. Two nunataks in the southern part of the island comprise basanitic tuff cones, composed of poorly bedded pyroclastic deposits dominated by sideromelane lapilli, and containing horizons rich in accretionary and armoured lapilli.

Many of the basanites have compositions of near-primary magmas and contain an assortment of Cr-diopside and Al-augite suite mantle nodules, lower crustal gabbros, mafic granulites, and assorted megacrysts. Peridotites are dominated by spinel facies inclusions, but include plagioclase–spinel lherzolites derived from shallow mantle beneath the tectonically thinned and attenuated Ross Sea lithosphere. Mantle nodules contain accessory amounts of pale brown, metasomatic amphibole. Volcanic geochemistry is compatible with fractionation of olivine, pyroxene, titano-magnetite and minor apatite from a basanite parent yielding tephriphonolite residual liquids. Magmatism is focused along, or at the termination of, Cenozoic rift basins in the Ross Sea. The regional McMurdo Volcanic Group distribution and tectonic setting, and the history of Erebus Province volcanic centres are difficult to reconcile in terms of active mantle plumes. Instead, more randomly distributed magmatism is inferred to result from rift-related decompression melting of previously enriched mantle that may have been fertilized by plume interaction prior to Gondwana fragmentation.