Petrology of pumices of April 1993 eruption of Lascar (Atacama, Chile) |
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| Authors: | Bernard Déruelle Oscar Figueroa A Eduardo Medina T Jose Viramonte G Mario Maragaño C |
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| Institution: | Laboratoire MAGIE, UniversitéPierre et Marie Curie and URA-CNRS 1732, 4, Place Jussieu, 75252 Paris Cedex 05, France;Departamento de Ciencias de la Tierra, Universidad de Concepción, Casilla 3-C, Concepción, Chile;Departamento de Ciencias Geológicas, Universidad Cátolica del Norte, Av. Angamos 0610, Antofagasta, Chile;Facultad de Ciencias Naturales, Universidad Nacional de Salta, Buenos Aires 177, Salta, Argentina |
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| Abstract: | Lascar Volcano (Atacama, Chile) erupted on 18–20 April 1993. Several sub-Plinian explosions occurred, and some were mushroom-shaped. The highest column rose up to 23 km. Ash clouds crossed South America eastwards. Dacite pumice falls made of blocks and ashes were deposited on the flanks of the volcano as a result of collapsed columns. The pumice contains phenocrysts of plagioclase, enstatite, augite, biotite, magnetite and ilmenite and small crystals of apatite. The 1992 previous andesite dome inside the crater was destroyed. Banded blocks resulting from mingling of the dacitic pumice and andesite from the dome are found in the pumice flow. Both the lava dome and the pumice are representative of the Lascar high-K magma unit. Dacitic pumice is a product of crystal fractionation of the andesitic magma. |
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