New insights into the Jurassic polyphase strain partition on the patagonian back-arc; constraints from structural analysis of ancient volcanic structures

Abstract

Located in the western Northpatagonian region, Argentina, the Lower Jurassic Cañadón Chileno Complex (CCHC) provides a remarkable opportunity to assess the roles of pre-, syn-, and post-eruptive faulting in felsic diatremes complexes evolution. The structural analyses of fractures, dikes, and folds allow recognition of the occurrence of four different strain partitions (SP1-SP4) developed during the Lower to Middle Jurassic. Recognized strain configurations show equivalent temporal and structural relationships throughout the Jurassic back-arc system of Patagonia and contemporary basins of southern South America. The stratigraphical criteria allow inferring an Upper Sinemurian to Lower Pliensbachian time interval for the initial strain configurations (SP1, SP2, and SP3). WNW, NNE, and NE-oriented extensional phases were defined and correlated with adjoining areas. Particularly, the third strain partition phase is characterized by a significant transpressive deformation. A NE contractional episode characterizes the post-eruptive deformation stage (SP4) during the Bajocian to Callovian interval. Tectonic interpretations were elaborated concerning subduction dynamics, continental drift, and rotation that controlled the regional and local stress configuration throughout the Jurassic Period of Patagonia and central Argentina.