Argon-Lead Isotopic Correlation in Mid-Atlantic Ridge Basalts

Abstract

Step-heating analyses for Mid-Atlantic Ridge glass samples show that maximum 40 Ar/ 36 Ar values correlate with 206,207,208 Pb/ 204 Pb. These correlations hold for the whole Atlantic Ocean and therefore are unlikely to result from shallow-level contamination processes. Instead, they are taken as mixing hyperbolae between the degassed-depleted upper mantle and a recycled component characterized by high 206 Pb/ 204 Pb ratios (19 to 21) and low 40 Ar/ 36 Ar ratios (300 to 1000). These relations imply that argon may also be a tracer of mantle recycling.