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.
The over-arching objective of this project is to compare oceanic and continental volcanism in the northwestern Ross Sea, Antarctica, in order to distinguish variations in mantle source and processes responsible for the formation of alkaline magmas in this region of the West Antarctic rift system. Specific purpose of this work include:
To determine the age of oceanic basaltic volcanism within the ... Adare Basin/Trough and adjoining continental shelf in order to compare with previously dated on-land deposits. Questions to be addressed include: Is the oceanic and continental volcanism contemporaneous? What is the timing of volcanism relative to the extensional history of this region? Is there a migration in volcanic activity in this region?
To determine the geochemical and isotopic composition of the basalts within the Adare Basin/Trough and compare these results to previously published and unpublished data from the region. Questions to be addressed include: Is the oceanic basaltic volcanism related, compositionally, to basaltic volcanism found on land? Is there systematic variation in composition from ocean to continent? If yes, then what is the cause of the variation?