Lithium isotopic composition of Central American volcanic arc lavas: implications for modification of subarc mantle by slab-derived fluids: correction

Our previously reported lithium isotope data for the least enriched members of the Central American Volcanic Arc were in error due to problems in ion extraction from high MgO rocks. This paper presents reanalyses of the entire suite of the CAVA lavas after a systematic investigation of the elution behavior of Li as a function of the rock composition. The most significant correction pertains to the mantle end members of the Nicaragua and Costa Rica series, which now display MORB-like delta(6) Li values (-4.5parts per thousand) and not much lighter (+ 1parts per thousand to + 3parts per thousand) as previously reported. Also revised is the composition of a peridotite from Zabargad Island (Red Sea), considered to represent undepleted upper mantle, whose corrected delta(6) Li also resembles MORB. These new data therefore remove the speculation that Earth's primitive mantle has extremely light Li isotopic composition and that the mantle beneath CAVA contains such isotopically light domains. The delta(6) Li range for the arc segment from Costa Rica to Guatemala has now been reset to -4.5parts per thousand to -6.4parts per thousand. Despite the narrower range, Li isotopic values remain well correlated with other subduction-related properties, including LILE and fluid-mobile elements. Model calculations show that the isotopic compositions of the lavas are consistent with small additions of slab-derived fluids to the enriched and depleted domains of the subarc mantle. (C) 2002 Elsevier Science B.V. All rights reserved.