Tectonic insight in the southwest Gondwana boundary based on anisotropy of magnetic susceptibility

ARZADÚN, G; TOMEZZOLI R.N.; TICKYJ, H.; CRISTALLINI, E.O.; GALLO, L.C.

Tectonics - Problems of Regional Settings

InTech

Año: 2018; p. 13 - 32

The anisotropy of magnetic susceptibility (AMS) is an effective tool to measure the rock petrofabric and it allow to analyze the tectonic stress in samples of zones with deformation. The southwest boundary of Gondwana in South America is the counter-part of the Cape fold belt of South Africa and the geological evolution of this region is still a subject of debate and doubts. Samples of different localities of this sector were analyzed with the AMS technique, the Buenos Aires province to the Mendoza province. For rocks of Permian age there is a clear regional magnetic signature indicating an NW-SE elongation direction and NE-SW shortening. However, the ASM patterns obtained in the oldest rocks are complex, probably as the result of stress interference in the magnitudes, space and time with different pulses of the orogenic activity developed from the Middle Devonian (Cháñica orogenic phase) to the Permian (San Rafael orogenic phase). In the southwest of Gondwana, small continental plates were accreted to the main continent mass during the Middle Devonian. The Permian deformation was interpreted as the consequence of a paleogeographic re-organization of Gondwana that moves to lowest latitudes to makes the Pangea continent during the Triassic. This younger deformation evidencing an attenuation and orogenic front migration to the foreland basin. Local responses related with lithological control in each locality is not ruled out.