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Abstract: Camptonites have been discovered at Mount Cameroon. They contain phenocrysts of olivine + clinopyroxene + plagioclase ± kaersutite ± bi and ocelli of nepheline or analcite and carbonates. 87Sr/86Sri values are similar to those of the basalts of Mount Cameroon . The camptonites are interpreted as resulting from fractional crystallization of a basaltic magma generated by a low degree of melting of an infra-lithospheric metasomatized mantle tapped by huge lithospheric cracks. To cite this article: I. Ngounouno et al., C. R. Geoscience 338 (2006). [Copyright &y& Elsevier]

Abstract: Scattered ignimbritic mesas crop out in the Hermosillo region (Sonora, Mexico). These rocks that have been dated at 12.5 Ma (Middle Miocene) have the petrography and chemical characteristics of comendites. Such a flare-up of peralkaline acidic volcanism, after a long period of subduction-related arc volcanism, emphasises an important change in the source of volcanism. It corresponds to the latest stage of continental extension prior to the marine invasion and the development of spreading centres in the Gulf of California. To cite this article: J. Vidal Solano et al., C. R. Geoscience 337 (2005). [Copyright &y& Elsevier]