Our previously reported lithium isotope data for the least enriched members of the Cultural 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 δ6Li values ( -4.5‰) and not much lighter (+1‰ to +3‰) as previously reported. Also revised is the composition of a peridotite from Zabargad Island (Red Sea), considered to represent undepleted upper mantle, whose corrected δ6Li 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 δ6Li range for the arc segment from Costa Rica to Guatemala has now been reset to -4.5‰ to -6.4‰. 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.
All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology