Late Paleozoic geodynamic evolution of the western North Patagonian Massif and its tectonic context along the southwestern Gondwana margin
MARCOS, PAULO; PIVETTA, CECILIA PAVÓN; BENEDINI, LEONARDO; GREGORI, DANIEL A.; GERALDES, MAURO C.; SCIVETTI, NICOLAS; BARROS, MERCEDES; VARELA, MARIA E.; SANTOS, ANDERSON DOS
ELSEVIER SCIENCE BV
In this study, we propose a geodynamic model covering sedimentation,metamorphism, magmatism, and exhumation processes for the western NorthPatagonian Massif basement. The youngest detrital zircon population ages (ca.369 ± 8 Ma) obtained in a schist sample constrains the sedimentation stage to theCarboniferous Period. A first prograde metamorphic stage (M1-D1) produced themain foliation (S1) under greenschist conditions (~ 500 °C; < 4.5 Kbars). This stagewas possibly linked to the regional Carboniferous magmatism event (330 ? 300Ma). The Permian magmatism (ca. 290 Ma) likely induced partial melting andmigmatization of the deepest metasedimentary suite. This event corresponds tothe second prograde metamorphic stage (M2) that reached amphibolite conditions(690 °C and 6.5 Kbars). The beginning of the basement uplift corresponds to thefirst retrograde metamorphic stage possibly developed during Permian ? Triassictimes (265 - 235 Ma). This event was triggered by NE-SW compression (σ1) anddeveloped folds (D2-F2), second foliation (S2), micro-textural quartz deformation,and a retrograde evolution path for the garnet-bearing lithofacies. The final stage ofthe basement exhumation corresponds to the second retrograde metamorphicstage (D3) developed by NNW-SSE compression and linked to open folds (F3) inthe Cushamen Formation. The characteristics of the western North PatagonianMassif geodynamic evolution and the adjacent basement regions suggest apaleotectonic subduction setting for the southwestern Gondwana margin during thelate Paleozoic times.