Chemistry of igneous rocks from, the Celebes Sea basement

Major and trace elements, mineral chemistry, and Sr-Nd isotope ratios are reported for representative igneous rocks of Ocean Drilling Program Sites 767 and 770. The basaltic basement underlying middle Eocene radiolarianbearing red clays was reached at 786.7 mbsf and about 421 mbsf at Sites 767 and 770, respectively. At Site 770 the basement was drilled for about 106 m. Eight basaltic units were identified on the basis of mineralogical, petrographical, and geochemical data. They mainly consist of pillow lavas and pillow breccias (Units A, B, D, and H), intercalated with massive amygdaloidal lavas (Units Cl and C2) or relatively thin massive flows (Unit E). Two dolerite sills were also recognized (Units F and G). All the rocks studied show the effect of low-temperature seafloor alteration, causing almost total replacement of olivine and glass. Calcite, clays, and Fe-hydroxides are the most abundant secondary phases. Chemical mobilization due to the alteration processes has been evaluated by comparing elements that are widely considered mobile during halmyrolysis (such as low-field strength elements) with those insensitive to seafloor alteration (such as Nb). In general, MgO is removed and P2O5 occasionally enriched during the alteration of pillow lavas. Ti, Cs, Li, Rb, and K, which are the most sensitive indicators of rock/seawater interaction, are generally enriched. The most crystalline samples appear the least affected by chemical changes. Plagioclase and olivine are continuously present as phenocrysts, and clinopyroxene is confined in the groundmass. Textural and mineralogical features as well as crystallization sequences of Site 770 rocks are, in all, analogous to typical mid-ocean-ridge basalts (MORBs). Relatively high content of compatible trace elements, such as Ni and Cr, indicate that these rocks represent nearly primitive or weakly fractionated MORBs. All the studied rocks are geochemically within the spectrum of normal MORB compositional variation. Their Sr/Nd isotopic ratios plot on the mantle array (87Sr/87Sr 0.70324-0.70348 with 143Nd/144Nd 0.51298-0.51291) outside the field of Atlantic and Pacific MORBs. However, Sr and Nd isotopes are typical of both Indian Ocean MORBs and of some back-arc basalts, such as those of Lau Basin. The mantle source of Celebes basement basalts does not show a detectable influence of a subduction-related component. The geochemical and isotopic data so far obtained on the Celebes basement rocks do not allow a clear discrimination between mid-ocean ridge and back-arc settings.

Gray de Cerdán, Nelly (2013), Universidad y sector científico trabajando para la reducción del riesgo a desastres. Experiencia de una Cátedra Universitaria con proyección internacional. Buenos Aires, Editorial El Escriba CONICET-CETEM Universidad Nacional de Cuyo, 124 p. ISBN: 978-987-605-480-5

Fil: Quiroga, Silvia. Universidad Nacional de Cuyo. Facultad de Filosofía y Letras

¡Me engañaste, me mentiste! La embajada persa a Atenas (Ar. Ach. 61-124) y sus implicaturas frente al público

Atendiendo a la relación establecida entre la comedia y los ámbitos político- legales que la circundan, se ha podido instituir un vínculo entre la ficción cómica y la realidad política de la Atenas clásica que se percibe fundamentalmente en las primeras comedias de Aristófanes. Dentro de Acarnienses podremos entonces determinar un nuevo punto de análisis si consideramos que en las breves declamaciones del persa se cifra uno de los recursos más notorios de la diplomacia estatal: la manipulación ante la asamblea del discurso de los embajadores de una nación por parte de la voz autorizada de la pólis receptora (Ammendola: 2001-2002). Será nuestro propósito abordar un costado diverso de esta escena definiendo su peso específico, aparentemente secundario, en la trama total de la obra. De ese modo nos interesará detectar la verdadera trascendencia del comportamiento del embajador persa respecto de los ciudadanos atenienses representados en la persona del viejo Diceópolis