Petit-spot volcanism: A new type of volcanic zone discovered near a trench

• DOI: 10.2343/geochemj.1.0111
• Publication Date: 2013-11-01T06:47:32Z
• Authors: NAOTO HIRANO
• Keywords: Asthenosphere; Hotspot (geology); Pacific Plate; Shield volcano

One extremely young volcano (0.05–1 Ma) and other volcanoes (1.8, 4.2, 6.0, 8.5 composed of strongly alkaline magma were recently discovered on the abyssal plain Early Cretaceous (135 Pacific Plate. These dubbed “petit-spots”. The petit-spot volcanic province represents more than 8 Myr activity over a large area (~600 km along direction plate motion), but with relatively small volume production, thus indicating supply heat inconsistent hotspot. low-flux may be related to occurrence tensional field lithosphere caused by flexure, ascending melt derived from mantle source susceptible partial melting. Rock samples are highly vesicular (up 60%) despite high hydrostatic pressures at 6000 m water depth, volatile-rich magmas. depleted heavy rare earth elements radiometric isotopic ratios noble gases indicate was upper mantle. Nevertheless, low 143Nd/144Nd, 87Sr/86Sr, 206Pb/204Pb, 207Pb/204Pb similar enriched or fertile compositions such as oceanic island basalts. apparently conflicting data explained degree melting recycled materials in degassing asthenosphere, probably carbonate source. volcanoes, therefore, provide unique window into nature underlying asthenosphere prior subduction.