Cartografía y cinemática de una rampa lateral en el distrito minero Río Blanco, faja plegada y corrida del borde oriental del Famatina (28º43' S), La Rioja

DÁVILA, F.M.; MARTINA, F.; ASTINI, R.A.

Revista de la Asociación Geológica Argentina

Asociación Geológica Argentinha

Lugar: Buenos Aires; Año: 2004 vol. 7 p. 101 - 106

0328-2767

ABSTRACT. Mapping and kinematics of a lateral ramp in the Río Blanco mining district, fold and thrust belt from the eastern border of the Famatina region (28º43'S), La Rioja. On the eastern slope of the Famatina Range (28º43?S), La Rioja, we carried out a geometric description of an oblique/transverse zone fault in order to interpret its kinematics and to discuss possible controls. In this region a fold and thrust belt (FPCF) involving Paleozoic and Cenozoic strata is developed, bounded by opposite-vergent major basement faults. Folds and thrusts strike N-S and dip with high angles (> 50ºW) and allow defining a west-east transport direction. Along the Río Blanco creek (28º43'S - 67º42'O), a major N-striking thrust sheet develops a sharp E-W bend. Fault plane dips 40º and 50ºN. Kinematic analysis suggests a ~NW-SE shortening axis (306º/3º) oblique to the FPCF transport direction. Geometry and kinematic analysis suggest that the Río Blanco thrust is a lateral/oblique ramp, which behaved as a connector between different thrusts sheets. Unfortunately, west termination is cut by a late out-of-sequence thrust. However, this lateral ramp explains the different styles and shortening observed to the north and south of the Río Blanco. It also may be related to the intense hanging wall fracturing. We infer that thrusting on the lateral ramp occurred in the Plio-Pleistocene, after Tertiary volcanism. Occurrence of dacitic bodies aligned with the lateral ramp suggests a lithologic control on its development, arguing the genetic link between the dacitic intrusion and the ramp formation. Mapping and kinematics of a lateral ramp in the Río Blanco mining district, fold and thrust belt from the eastern border of the Famatina region (28º43'S), La Rioja. On the eastern slope of the Famatina Range (28º43?S), La Rioja, we carried out a geometric description of an oblique/transverse zone fault in order to interpret its kinematics and to discuss possible controls. In this region a fold and thrust belt (FPCF) involving Paleozoic and Cenozoic strata is developed, bounded by opposite-vergent major basement faults. Folds and thrusts strike N-S and dip with high angles (> 50ºW) and allow defining a west-east transport direction. Along the Río Blanco creek (28º43'S - 67º42'O), a major N-striking thrust sheet develops a sharp E-W bend. Fault plane dips 40º and 50ºN. Kinematic analysis suggests a ~NW-SE shortening axis (306º/3º) oblique to the FPCF transport direction. Geometry and kinematic analysis suggest that the Río Blanco thrust is a lateral/oblique ramp, which behaved as a connector between different thrusts sheets. Unfortunately, west termination is cut by a late out-of-sequence thrust. However, this lateral ramp explains the different styles and shortening observed to the north and south of the Río Blanco. It also may be related to the intense hanging wall fracturing. We infer that thrusting on the lateral ramp occurred in the Plio-Pleistocene, after Tertiary volcanism. Occurrence of dacitic bodies aligned with the lateral ramp suggests a lithologic control on its development, arguing the genetic link between the dacitic intrusion and the ramp formation.