Abstract

RODRIGUEZ G., GABRIEL  and  ZAPATA G., GILBERTO. COMPARATIVE ANALYSIS OF THE BARROSO FORMATION AND QUEBRADAGRANDE COMPLEX: A VOLCANIC ARC THOLEIITIC-CALCOALCALINE, SEGMENTED BY THE FAULT SYSTEM ROMERAL IN NORTHERN ANDES?. Bol. cienc. tierra [online]. 2013, n.33, pp.39-58. ISSN 0120-3630.

The Barroso formation and the Quebradagrande Complex consist of basaltic and andesitic lava flows, with tuffs, agglomerates, and sedimentary packages of chert, mudstone, siltstone, greywacke and conglomerate that usually lie awkwardly on volcanic rocks or are intercalated with them. Quebradagrande Complex has been affected by the fault system that deforms the rocks Romeral and generates a series of sedimentary and volcanic fragments with propylitic alteration, and ductile and brittle deformation. This is limited by faults east of San Jerónimo and Silvia - Pijao to west. The characteristics of the major oxides, rare earth elements and trace, suggest that the Barroso Complex and the Quebradagrande Formation, where formed in a magmatic arc of suprasubducción. Both formations having affinities tholeiitic and calc-alkaline medium-K. Quebradagrande Complex has higher content of Th and slightly lower content of Hf than the Barroso Formation. But both entities show the same trend in all geochemistry graphs; suggesting the possibility that they were generated in the same magnetic arc. The Barrosos Formation and the Quebradagrande Complex, presented a series of data like radiometric ages date, sequences associated with sedimentary with fossil records and basal conglomerates, as well as intrusive stratigraphic with Cretaceous plutons of Albian to Turonian age. These allow postulating the same age for both units within the Albian-Aptian range. The petrographic, lithologic, litogeoquímica, radiometric information and estratigrágicas relations suggest that both units may have been generated in the same magmatic arc and were subsequently dismembered by Romeral Fault System The magmatic arc that led to the Barroso Formation, Quebradagrande Complex and associated plutons, got emplaced along the weaker zone, or convergence zone of oceanic and continental crust, which were next to each other, or very close together. This is based to the composition of the clusters associated with Quebradagrande Complex, with input from both cortices and the intrusion of plutons as Sabanalarga Batholith, Buritica tonalite and Diorite of Altavista. This suggests that the crash occurred before Albian-Aptian period.

Keywords : Magmatic arc; Romeral Fault System; Complex Quebradagrande; Barroso Formation.

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