Determining magma sources for Jan Mayen Island and environs using strontium isotopes

Robin Chernow

Volcanic rocks from the Jan Mayen Island hotspot and its environs (including the adjacent Northern Kolbeinsey and Southern Mohns Ridge segments) provide an opportunity for geochemists to study the mantle heterogeneity of the region. Analyzing heterogeneous mantle melting and hotspot-ridge interactions allows for a greater understanding of mantle dynamics and of how new ocean crust is produced. The characteristics of the magmas fingerprint the types and origins of solid mantle reservoirs (e.g., subducted crust or mantle rocks depleted in incompatible elements). The Jan Mayen region contains magma enriched in incompatible elements, suggesting the magma derives from a source containing subducted crust and subcontinental lithospheric mantle rifted from Greenland.  An inductively-coupled plasma mass spectrometer will be used to evaluate the 87Sr/86Sr isotope ratios after chemically extracting the strontium from subaerial volcanic whole rock powders and fresh glass separates from submarine basalts. Low 87Sr/86Sr ratios would suggest the mantle source has experienced melt extraction, depleting it in incompatible elements, similar to the upper mantle that globally produces mid-ocean ridge magmas. High 87Sr/86Sr ratios indicate a mantle source containing recycled subducted crustal material, which some models suggest derives from a deep-seated mantle plume source.