CICTERRA 20351
CENTRO DE INVESTIGACIONES EN CIENCIAS DE LA TIERRA
Unidad Ejecutora - UE
artículos
Título:
Geoquímica de las rocas metasedimentarias del Cámbrico medio al Ordovícico temprano de la Sierra de Los Llanos (Sierras Pampeanas, Argentina). Fuente de sedimentos, correlación y ambiente geotectónico
Autor/es:
VERDECCHIA S. O.; MURRA J.; BALDO E, G.; CASQUET C.; PASCUA I.; J. SAAVEDRA,,
Revista:
ANDEAN GEOLOGY
Editorial:
SERVICIO NACIONAL GEOLOGIA MINERVA
Referencias:
Lugar: Santiago de Chile; Año: 2013 vol. 41 p. 380 - 400
ISSN:
0718-7092
Resumen:
The metamorphic complex of Sierra de Los Llanos is composed by low- to high-grade metasedimentary rocks, namely phyllites, schists, gneisses and migmatites that out crop like large septa inside of lower Ordovician magmatic units. Cornubianite associated to intrusive basic bodies are locally recognized. Chemical composition of these metasedimentary rocks is equivalents to pelite and arenite (sublitharenite-subarkose). Chemical ratios of Ti/Zr (5.4-8.4), La/Sc (5.2-8.5), Th/Sc >1 (2.2-3.4), La/Th (2.0-2.5) and Zr/Sc (60-103), along with contents of Hf (7.9 a 12.4 ppm) and Sc (4.4-5.2 ppm) in meta-psammites suggest that the source of the sediments was enriched in felsic components or recycled material and limited participation mafic components. A same composition of source areas for meta-psammites of this complex and Chepes, La Cébila and Pringles metamorphic complexes is suggests from geochemical data. Ti, Zr, Hf, La, Th and Sc concentrations are variable and do not allow to clearly define a specific geotectonic context and suggest that the composition of the protoliths was largely controlled by sedimentary processes rather than compositional heterogeneity of the sources. The integration of geochemical and known geochronological data and the regional correlation of Ordovician metamorphic complexes strengthen the interpretation that defines igneous and metamorphic rocks from Pampean orogenic belt and Río de La Plata craton as the mayor sources of these complexes. Further, this information is consistent with the existence of an extensive continental shelf in the southwestern margin of Gondwana during the Middle Cambrian to Early Ordovician.
