Condiciones y tiempo de formación de los óxidos de hierro en las volcanitas alcalinas cretácicas de la Sierra Chica de Córdoba, determinadas a partir de sus propiedades magnéticasMineralogía y Metalogenia 2000

GEUNA, SILVANA; LAGORIO, SILVIA

La Plata

Congreso; Congreso de Mineralogía y Metalogenia; 2000

The oxide mineralogy and magnetic properties were examined in a suite of 21 lava flows and dike samples from Sierra de los Cóndores Group in an attempt to elucidate their magnetic petrology. Unless the characteristic remanence is carried by fine-grained oxidized (titano)magnetite, we found that most of the studied rocks show a significative proportion of hematite as a magnetic carrier too. The natural remanent magnetization (NRM) unblocked below 590ºC during thermal demagnetization was assigned to magnetite and that unblocked above 610ºC to hematite. Magnetite and hematite appeared to retain different directions of magnetization, and field tests proved that: 1) magnetite component of magnetization was primary in origin, probably related to high-temperature oxidation process on cooling of lava flows, and 2) hematite component of magnetization was secondary in origin; we interprete this component related to martitization process, product of weathering or hydrothermal alteration around intrusive bodies or near top flows.