Variable Impact of the Subducted Slab on Aleutian Island Arc Magma Sources: Evidence from Sr, Nd, Pb, and Hf Isotopes and Trace

• Main Authors: Element Abundances, B. R. Jicha, B. S. Singer, J. G. Brophy, J. H. Fournelle, C. M. Johnson, B. L. Beard, T. J. Lapen, N. J. Mahlen
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2003
• Subjects: Aleutian Island
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.600.5675; http://petrology.oxfordjournals.org/content/45/9/1845.full.pdf

Major and trace element compositions and Sr, Nd, Pb, and Hf isotope ratios of Aleutian island arc lavas from Kanaga, Roundhead, Seguam, and Shishaldin volcanoes provide constraints on the com-position and origin of the material transferred from the subducted slab to the mantle wedge. 40Ar/39Ar dating indicates that the lavas erupted mainly during the last 400 kyr. Along-arc geochemical and isotopic variations are consistent with variable degrees of fluid input to the mantle wedge. Addition of bulk sediment, partially melted sediment, or a combination of sediment and fluid components may also explain the major and trace element and isotopic composi-tions of some Aleutian lavas. Mass-balance modeling suggests that the fluid is derived from subducted sediment (10–25%) and under-lying oceanic crust (75–90%). Hf–Nd isotope data suggest that relative to Nd, little Hf is transferred to the mantle wedge via fluid. Lavas from Seguam Island in the central Aleutian arc have distinctly