Mantle Origin of Oceanic Carbonatites
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. School of Earth Sciences Senior Theses; 2010
Carbonatites are igneous rocks composed of over 50% carbonate minerals. These unusual rocks are generally associated with rift systems but are also found on ocean islands, namely Fuerteventura in the Canary Islands and islands in the Cape Verde chain. Their origins in rift systems are widely believed to result from intense magma fractionation, but this explanation doesn’t work for oceanic carbonatites. The purpose of this research is to explore the mantle source of the oceanic carbonatite and contrast it with other occurrences. To accomplish this, both stable and radiogenic isotope data from oceanic carbonatite, young carbonatite from the East African Rift, and kimberlites were obtained from the GeoRoc database and analyzed in the program Cohort6. By examining these data, it was found that the carbonatite from Fuerteventura and Cape Verde have a very close genetic relationship and the isotopic signature suggests involvement of recycled oceanic crustal material. It was also observed that while rift carbonatites show the same general range of isotopic compositions as oceanic carbonatite, kimberlites are very different. There needs to be more work done on the stable isotopes with respect to Fuerteventura and kimberlites, but this is simply a matter of data collection. These results fit well with the findings of other research groups and show an interesting relationship between these different carbon-bearing igneous rocks. This will provide a better understanding of the presence of carbon in the mantle as research continues on rare earth elements, trace elements and stable isotopes.