Isotopic and thermochronologic evidence of extremely cold lithosphere associated with a slab flattening in the Central Andes of Argentina

COLLO, GILDA; DÁVILA, FEDERICO M.; TEIXEIRA, WILSON; NÓBILE, JULIETA C.; SANT? ANNA, LUCY G.; CARTER, ANDREW

BASIN RESEARCH

WILEY-BLACKWELL PUBLISHING, INC

Año: 2017 vol. 29 p. 16 - 40

0950-091X

We present mineralogic, isotopic and thermochronologic analyses on psammopelitic and tuffaceous levels from the Bermejo and Vinchina basins ? both foreland depocentres of the Central Andes of Argentina ? that define a low-temperature regime for the crust akin to a slab shallowing and flattening process. The contents of illite in illite/smectite interstratified (I/S) show a progressive illitization into the deeper parts of both basins. The distribution of I/S is compatible with theoretical simulations and predicted heat flow values of ca. 26 mW m−2 in the 8?3.4 Ma interval for the Vinchina Basin and ca. 42 mW m−2 since 9 Ma for the Bermejo Basin. The latter shows heat flow values that are comparable to those reported by magnetotelluric analysis (36?40 mW m−2) in agreement with previously published heat flow calculations along the modern Andean foreland. The Rb?Sr isochrones in psammopelites (