Collaborative Research: Geochemical transect from oceanic Adare Basin to adjacent continental Adare Peninsula: implications for the origin of intraplate (HIMU-like) alkaline magmas

Detailed analytical studies are still being conducted on Adare Basin samples, but preliminary results for their major element, trace element and Sr-Nd-Pb isotopic compositions resemble those of volcanic rocks from ocean islands with a distinct, hotspot compositional affinity. Combined with literature data for volcanic rocks from the adjacent continental margin of West Antarctica, the volcanic rocks show a remarkable orderly compositional variation toward the continent, suggesting they were generated from a common heterogeneous mantle source at progressively greater melt fractions from ocean to continent. Small degree partial melting preferentially taps the more easily fusible, hotspot-like component of the mantle whereas higher degree melting incorporate greater proportions of the adjacent ambient mantle. Significantly, new oxygen and osmium isotopic results for both continental and oceanic samples are consistent with such a partial melting scenario although they also suggest a small, but steady increase in crustal contamination toward the continent. Thus, although preliminary results do not clearly suggest a major role of hotspot magmatism in the rifting process, they do not preclude it either.