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Summary: Oxygen isotope evidence for the origin of enriched mantle
beneath the mid-Atlantic ridge§
Kari M. Cooper a;Ã
, John M. Eiler a
, Paul D. Asimow a
,
Charles H. Langmuir b
a
Division of Geological and Planetary Sciences, California Institute of Technology, MC 170-25, Pasadena, CA 91125, USA
b
Department of Geological and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA
Received 15 March 2003; received in revised form 4 September 2003; accepted 12 January 2004
Abstract
Geochemical variations in mid-ocean ridge basalts have been attributed to differing proportions of compositionally
distinct mantle components in their sources, some of which may be recycled crust. Oxygen isotopes are strongly
fractionated by near-surface interactions of rocks with the hydrosphere, and thus provide a tracer of near-surface
materials that have been recycled into the mantle. We present here oxygen isotope analyses of basaltic glasses from the
mid-Atlantic ridge south of and across the Azores platform. Variations in N18
O in these samples are subtle (range of
0.47x) and may partly reflect shallow fractional crystallization; we present a method to correct for these effects.
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