Abstract

Isotopic and trace element data for basaltic lavas from the Springerville volcanic field, east-central Arizona, define three distinct mantle components involved in magma genesis in this part of the Colorado Plateau-Basin and Range transition zone. Correlated isotopic and trace element variations indicate that Springerville alkalic basalts were derived by mixing between components from a depleted asthenospheric source, an enriched fithospheric source, and a lithospheric source that exhibits radiogenic Pb and relatively nonradiogenic Sr characteristics. Tholeftic basalts from the Springerville field equilibrated in the enriched mantle lithosphere and subsequently interacted with crust. Two of the distinct mantle components correspond to Zindler and Hart's proposed mantle isotopic end members PREMA and EMI, and the third mantle component suggests the possible existence of a HIMU-type reservoir. These observations have implications for the origin of enriched isotopic compositions in oceanic-island magmatism and support the theory that delamination of the subcontinental lithosphere is a feasible mechanism to recycle enriched components back into the mantle to be erupted at "anomalous" oceanic islands.

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