Per citar aquest document: http://ddd.uab.cat/record/86019
Magmatic and geotectonic significance of Santa Elena Peninsula, Costa Rica
Gazel, E. (Universidad de Costa Rica. Escuela Centroamericana de Geología)
Denyer, P. (Universidad de Costa Rica. Escuela Centroamericana de Geología)
Baumgartner, P.O. (Université de Lausanne. Institut de Géologie et Paléontologie)

Data: 2006
Resum: We present a new integrated interpretation of the geochemistry and geotectonic significance of the Santa Elena Peninsula, which is divided in three units: 1) an overthrust allocthonous unit of ultramafic and mafic rocks, the Santa Elena Nappe; 2) an autochthonous basaltic sedimentary suite, resting immediately below the overthrust, the Santa Rosa Accretionary Complex; and 3) Islas Murciélago pillow and massive basaltic flows. In the Santa Elena Nappe three petrological affinities have been recognized: 1) the ultramafic complex, that corresponds to depleted (MORB-like) mantle serpentinizated peridotites, with very low TiO2 and high Ni and Cr; 2) the pegmatitic gabbros, layered gabbros and plagiogranites and basaltic dikes with low TiO2 (< 0. 89%) contents and high LREE depletions; and 3) the doleritic dykes with higher TiO2 (>0. 89%). These mafic associations have geochemical signatures that suggest an island arc origin and petrographic evidences of low grade metamorphism and hydrothermal alteration. The Santa Rosa Accretionary Complex includes pelagic and volcanoclastic sediments, tuffs and alkaline magmatic rocks, originated by low degree melting of enrichment OIB mantle source, and probably related with seamount portions incorporated into the accretionary prism. Islas Murciélago pillow and massive basalts show no clear structural relationship with the rest of the units, but are geochemically similar to the dolerites of the Santa Elena Nappe. Sr, Nd, and Pb isotopic ratios of the Santa Elena Nappe and the Santa Elena Accretionary Complex samples do not correspond to the Galapagos Mantle array, and have different mantle reservoirs and geochemical characteristics than the Nicoya Complex.
Drets: Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l’obra i la creació d’obres derivades, fins i tot amb finalitats comercials, sempre i quan aquestes es distribueixin sota la mateixa llicència que regula l’obra original i es reconegui l’autoria de l’obra original. Creative Commons
Llengua: Anglès.
Document: article ; recerca ; publishedVersion
Matèria: Santa Elena Peninsula ; Oceanic assemblages ; Ultramafic Complex ; Geochemistry ; Accretionary complex
Publicat a: Geologica acta, Vol. 4, Núm. 1-2 (2006) , p. 193-202, ISSN 1696-5728

Adreça alternativa: http://www.raco.cat/index.php/GeologicaActa/article/view/82398
DOI: 10.1344/105.000000365


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