The Cuaró Mesozoic doleritic dyke swarm, southern Paraná basin, Uruguay: Examples of superimposed magnetic fabrics?

Abstract : The Cuaró intrusion swarm includes dykes and sills and represents the southern part of the plumbing system of the Paraná Large Igneous Province. Structural analysis reveals that it is emplaced in an overall north­south spreading direction and that extensional tectonics went on during a significant period of hydrothermal activity. Preliminary results of the Anisotropy of Magnetic Susceptibility (AMS) study show several magnetic fabrics, mostly carried by magnetite and maghemite, with typical oblate shapes in the sills and oblate to predominantly prolate shapes in the dykes. Most of the intrusions show superimposed magnetic fabrics in the same sampling zones. Some fabrics support interpretations in terms of magma flow, but objectively, different origins for other fabrics, especially for the superimposed ones, cannot be discarded at this stage. Some magnetic fabrics are consistent with those expected in the tectonic deformation field recorded up to the late hydrothermal event. Thus, we suspect that sub-solidus recrystallisations under tectonic stress and/or under some hydrothermal fluid flow may have induced some of the fabrics in the Cuaró intrusions.