Effect of Hotspots on the Evolution of Microplates around the Nazca Plate

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Understanding the variation in the chemical composition of sea-floor volcanic rocks is important to understanding both the processes that produce the oceanic crust and origin of sea-floor magmas in the mantle. Recent research has shown that the major and trace element chemistry can be controlled by both source differences as well as the extent of source melting and subsequent crystallization of the magma during its ascent to the sea-floor. The isotopic composition of lead, neodymium and strontium, however, apparently reflects the original mantle source. By examining the complete chemistry of crustal rocks it should be possible to determine the importance of various mantle sources in the crustal genesis. The objective of the present project is to complete lead, neodynium and strontium isotope measurements on spreading center basalts from the boundaries of the Nazca Plate in the eastern Pacific. Major and trace element analyses have already been completed on these samples. The major goal of the study is to determine the role that mantle hotspots have played in the break- up of major crustal plates in the region. This complex history of plate fragmentation has led to a number of transient microplates during the last 30 million years. Samples to be studied are from the Easter and Juan Fernandez Microplates and the Galapagos Spreading Center. The principal investigator on this project is highly qualified to perform the research and is an authority on the isotope composition of crustal rocks.