Examinando por Autor "Marin-Ceron, Maria I."

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    Improved gasoline-powered soft-sediment cutter
    (SEPM-SOC SEDIMENTARY GEOLOGY, 2013-09-01) Sierra, Gloria M.; Marin-Ceron, Maria I.; Ramirez, Jackeline; Uribe, Camilo; Sierra, Gloria M.; Marin-Ceron, Maria I.; Ramirez, Jackeline; Uribe, Camilo; Universidad EAFIT. Departamento de Ciencias; Geología Ambiental y Tectónica
    A device used for paleomagnetic sampling has been improved which allows sampling friable, poorly to moderate lithified sedimentary and volcanic materials. The new device attaches to a portable gasoline drill and employs two steel cutting disks with a 2 cm separation, which cuts two parallel slots in the material being sampled. A second set of cuts orthogonal to the first set produces a square pedestal over which a plastic sample box can be placed and oriented to extract a cubic sample; this procedure permits using the same orientation parameters as for conventionally drilled cylindrical samples. The method allows sampling at localities where conventional drilling fails in weak materials. To test the method, sedimentary sandstones of the Amaga' Formation (Eocene-Miocene) in the NW portion of the Central Colombian Andes were sampled. The anisotropy of magnetic susceptibility (AMS) was measured on samples using the new method and compared with results from conventionally drilled cores at the same sites. Results show better AMS within-site precision for box samples compared with the drilled cores. This device improves on previous battery-powered samplers used for sampling by the double-slot procedure. Also the new device can be used with the same gasoline-powered motor for standard core drilling. Copyright © 2013, SEPM (Society for Sedimentary Geology).
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    Slab decarbonation and CO2 recycling in the Southwestern Colombian volcanic arc
    (PERGAMON-ELSEVIER SCIENCE LTD, 2010-02-01) Marin-Ceron, Maria I.; Moriguti, Takuya; Makishima, Akio; Nakamura, Eizo; Marin-Ceron, Maria I.; Moriguti, Takuya; Makishima, Akio; Nakamura, Eizo; Universidad EAFIT. Departamento de Ciencias; Geología Ambiental y Tectónica
    The contribution of subducted carbonate sediments to the genesis of the Southwestern Colombian arc magmas was investigated using a comprehensive petrography and geochemical analysis, including determination of major and trace element contents and Sr, Nd, Hf and Pb isotope compositions. These data have been used to constrain the depth of decarbonation in the subducted slab, indicating that the decarbonation process continues into the sub-arc region, and ultimately becomes negligible in the rear arc. We propose on the basis of multi-isotope approach and mass balance calculations, that the most important mechanism to induce the slab decarbonation is the infiltration of chemically reactive aqueous fluids from the altered oceanic crust, which decreasingly metasomatize the mantle wedge, triggering the formation of isotopically different primary magmas from the volcanic front (VF) with relatively high Hf-176/Hf-177, high Sr-87/Sr-86, negative values of epsilon Nd and lower Pb isotopes compared to the rear arc (RA). The presence of more aqueous fluids at the volcanic front may increase the degree of decarbonation into carbonate-bearing lithologies. Moreover, with increasing pressure and temperature in the subduction system, the decrease in dehydration of the slab, leads to cessation of fluid-induced decarbonation reactions at the rear arc. This development allows the remaining carbonate materials to be recycled into the deep mantle. (C) 2009 Elsevier Ltd. All rights reserved.