Tectonostratigraphic development of the Permian Choiyoi Group along the western margin of the Gondwana continent (32°–33° S)

The Choiyoi Group in the Cordillera Frontal and Precordillera of Mendoza Province, Argentina, rests on an irregular erosional surface due to the Lower Permian San Rafael Diastrophic Phase. These rocks are organized into eight lithostratigraphic units in three main sections. The lower section includes both high-energy sedimentation and basaltic to andesitic volcanism, with a probable age of 291.2 Ma. The geochemical features of these rocks resemble magmas generated in subduction zones. The middle section, dated at 276.4 Ma, includes lava flows and domes of dacitic composition and pyroclastic flow deposits. The geochemical signatures suggest a subduction-related magmatic origin. Transitionally, the upper section continues with lacustrine deposits, high-welded tuff related to rhyolitic subvolcanic bodies dated at 273.1 Ma, with geochemical characteristics typical of magmas emplaced in intraplate settings. A model of the evolution of the Choiyoi Group indicates a transition from subduction-related activity to intraplate-related volcanism in the western margin of the Gondwana Continent.