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1 Institute for Geochemical Research, Hungarian Academy of Sciences, Budapest, Budaörsi út 45., H-1112, Hungary (e-mail: demeny{at}geochem.hu)
2 Dpto. de Edafologia y Geologia, Universidad de La Laguna, Avda. Astrofisico Fco. Sánchez, 38206 La Laguna, Tenerife, Spain
3 Institut de Minéralogie et Géochimie, Université de Lausanne, L'Anthropole, CH-1015 Lausanne, Switzerland
4 Institute for Mineralogy, Petrology and Geochemistry, University of München, Theresienstrasse 41/III, D-80333 München, Germany
5 School of Ocean and Earth Science, Southampton Oceanography Centre, European Way, Empress Dock, Southampton SO14 3ZH, UK
Chemical and isotopic compositions of amphiboles, biotites, pyroxenes and feldspars from gabbros and basalts of La Palma, Canary Islands, were studied to determine primary, plume-related compositions and effects of late-stage water–rock interactions. All the studied amphiboles have Sr isotope ratios close to those typical for the mantle, excluding the possibility of significant seawater influence. The pyroxenes and amphiboles also have stable isotope compositions that are typical for mantle-derived phases, whereas biotites and feldspars show signs of interaction with meteoric water. On the basis of the oxygen isotopic compositions, the infiltrating meteoric water derived from precipitation at an approximate elevation of 3500 m above sea level, indicating that La Palma reached this height when the gabbro complexes were formed. The unaltered hydrogen and oxygen isotope compositions of amphiboles show a trend from normal mantle ranges to –90
and 5.1, respectively; these values are very close to compositions found in other Canary Island complexes by earlier studies, and support the theory that these compositions reflect a plume component originating from depth, rather than local phenomena.
