Geochemistry of the mantle source and magma feeding system beneath Turrialba volcano, Costa Rica

摘要: Abstract Turrialba volcano lies in the southern sector of Central American Volcanic Front (CAVF) Costa Rica. The geochemistry major and trace elements, Sr Nd isotopes a selected suite volcanic rocks ranging composition from basaltic andesite to dacite belonging last 10 ka activity is described, together with He-, Ne-, Ar-isotope compositions fluid inclusions hosted olivine pyroxene crystals. Most variability rock chemistry consistent typical trends fractional crystallization, but there an outlying group andesites that displays adakite-like (with depletion high-field-strength elements marked enrichment Sr) low 3 He/ 4 He ratios (7.0–7.2 Ra). trace-element these subduction-related magmas influenced by OIB-like component at source associated subduction Galapagos seamounts. 87 Sr/ 86 (0.703612–0.703678) 143 Nd/ 144 (0.512960–0.512984) bulk vary within narrow ranges, are among least-radiogenic isotope signatures CAVF volcanoes. measured crystals (up 8.1 Ra) highest for CAVF, indicate radiogenic fluids derived subducting slab contribute negligibly mantle wedge. difference between most studied those showing features reasonably reflects two distinct components local mantle: (1) MORB-like component, characterized He-isotope (7.8–8.1 Ra), (2) lower coming An overview regional scale indicates high peculiar extreme sectors (Costa Rica south Guatemala north), whereas central (Nicaragua) magma probably contaminated fluids. For past few years has been unrest phase included series explosions, recent which occurred October 2014 May 2015. subject ongoing safety alert due possibility magmatic eruption. One crucial questions be addressed kind eruption can expected, hence what type likely involved. (7.8–8.0 during 2011 high-temperature fumaroles craters comparable erupted 1864–1866, suggesting currently feeding shallow plumbing system similar geochemical characteristics recently magma.