Mississippian lamprophyre dikes in western Sierras Pampeanas, Argentina: Evidence of transtensional tectonics along the SW margin of Gondwana. (April 2018)

• Record Type: Journal Article
• Authors: Martina, Federico; Canelo, Horacio N.; Dávila, Federico M.; de Hollanda, María Helena M.; Teixeira, Wilson
• Is Part Of: Journal of South American earth sciences. Volume 83(2018)
• Page Start: 68
• Page End: 80
• Publication Date: 2018-04
• Subjects: Famatina range -- Lamprophyre dike swarm -- Structural analysis -- 40Ar/39Ar geochronology -- Mississippian -- SW Gondwana; Geology -- Latin America -- Periodicals; Earth sciences -- Latin America -- Periodicals; Geology -- Antarctica -- Periodicals; Earth sciences -- Antarctica -- Periodicals; Geology -- Caribbean Area -- Periodicals; Earth sciences -- Caribbean Area -- Periodicals; Géologie -- Amérique latine -- Périodiques; Sciences de la terre -- Amérique latine -- Périodiques; Géologie -- Antarctique -- Périodiques; Sciences de la terre -- Antarctique -- Périodiques; Géologie -- Caraïbes (Région) -- Périodiques; Sciences de la terre -- Caraïbes (Région) -- Périodiques; Earth sciences; Geology; Antarctica; Caribbean Area; Latin America; Periodicals; 550.5
• DOI: 10.1016/j.jsames.2018.02.006
• Languages: English
• ISSNs: 0895-9811

Abstract

Abstract: In the Famatina range, Sierras Pampeanas of Argentina (SW Gondwana), subvertical calc-alkaline lamprophyric dike swarms crop out through >300 km. The dikes cut Ordovician units with a prominent NW-SE trending and are covered by continental sedimentary successions of Pennsylvanian to Permian age. The dikes show a strong structural control associated with Riedel fault systems. Detailed field analysis suggested a ∼N-S opening direction oblique to the attitude of dike walls and a left-lateral transtensional tectonics during the emplacement. 40 Ar/ 39 Ar geochronology of a lamprophyric sample defined a crystallization age (plateau; whole rock) of 357.1 ± 7.1 Ma (MSWD = 2.3). Coetaneous ductile zones with dominant strike-slip motion, documented along western Argentina for >600 km, suggest a regional event in SW Gondwana during the Mississippian. We propose that this deformation was the result of the counterclockwise fast rotation of Gondwana between 365 and 345 Ma, when the Famatina range and western Argentina occupied a sub-polar position. A transform margin along SW Gondwana better explains our (and others) data rather than a subduction margin. This scenario is also consistent with the occurrence of A-type granites and normal-fault basins within the foreland as well as bimodal volcanics. Highlights: Ar-Ar whole-rock dating of a lamprophyre dike from W Argentina yields 357 Ma. The dikes emplacement was strongly controlled by development of NW Riedel fractures. Calculated opening direction is ∼N-S, oblique to dike walls and σ3. Kinematic indicators suggest a sinistral transtensional tectonics. The dikes were result of the coetaneous counterclockwise rotation of SW Gondwana.