Geological and geophysical methods relevant to decipher the structure and emplacement of granites: Insights from the Calmayo pluton (Eastern Sierras Pampeanas, Argentina)

PINOTTI, LUCIO; D'ERAMO, FERNANDO; GEUNA, SILVANA; RADICE, STEFANIA; GÓMEZ-ORTÍZ, DAVID; VEGAS, NÉSTOR; CONIGLIO, JOAQUÍN; BOFFADOSSI, ALEJANDRA; MURATORI, M. EUGENIA; DEMARTIS, MANUEL; KOSTADINOFF, JOSÉ

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2021

0895-9811

In this paper, the evolution of the fabric and 3Dgeometry of the Calmayo trondhjemitic pluton (512.1±3.4 Ma; Sierra Chica,Córdoba, Argentina) is analyzed using Anisotropy of Magnetic Susceptibility(AMS) measurements combined with structural and microstructural data. Gravitydata reveal that the pluton is a funnel-shaped body resting on one main rootzone detected below the central portion of the pluton. The microstructural observationsin the trondhjemite rocks show a progressive textural overprint from magmatic,through high-T to low-T solid-state deformation textures. This overprint is interpretedto be a consequence of the dynamic emplacement and local deformation, particularlyclose to the adjacent Soconcho shear zone. Late oxidation of the magnetic mineralassemblage (martitization of magnetite) is more intense in the central andsouthern sectors close to the root zone, explaining the flat magnetic responseof this area, and contrasting with a noisy domain to the northeast wheremagnetite is preserved. We propose that the Calmayo pluton was constructed byseveral pulses that ascended through a root zone or main conduit. This rootzone represents feeder dykes that exploited tension fractures linked to theSoconcho shear zone. Fluids responsible for the late oxidation would havefollowed similar paths through this protracted shear zone.