Volatile abundances in basaltic glasses from seamounts flanking the East Pacific Rise at 21 degrees N and 12 -14 degrees N

Volatiles in glasses from seamounts flanking the East Pacific Rise (EPR) in the vicinity of 21°N and 12–14°N were analyzed by high-temperature mass spectrometry. Compared to mid-ocean ridge basalt (MORB) magmas erupted at the spreading axis of the EPR at 21°N, the seamount magmas are commonly enriched in H2O, Cl, F and S (at the same Mg{\#}). Water and Cl abundances range from 0.111 to 1.021 wt.{%} and 0.003 to 0.226 wt.{%}, respectively. The wide range in abundances is consistent with the diversity of magmas erupted by these seamounts as indicated previously from major and rare-earth element data. H2O shows a strong linear positive correlation with K2O content [H2O = 0.45 (±0.04) K2O + 0.22 (±0.03) with RMS error of 0.09]. Based on -ratios and K2O abundances the glasses separate into three distinct groups: highly volatile-enriched alkalic/transitional, enriched tholeiitic, and depleted tholeiitic. Ratio-ratio plots of incompatible elements ( vs. ) indicate that these seamount magmas can all be related by the mixing of enriched and depleted source materials.