Rotation of crustal domains related to Gondwanide deformation in the Neoproterozoic–Cambrian Sauce Chico Complex (Argentina), southwestern margin of the Río de la Plata Craton: Insights from AMS data

VÁZQUEZ LUCERO, SEBASTIÁN E.; BALLIVIÁN JUSTINIANO, CARLOS A; FAZZITO, SABRINA ; PREZZI, CLAUDIA B.; RUÍZ GONZÁLEZ, VÍCTOR; RODRÍGUEZ, SERGIO; VIZÁN, HAROLDO

PRECAMBRIAN RESEARCH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2024 vol. 406 p. 1 - 20

0301-9268

Thetectonic evolution of the Ventania System fold and thrust belt and the originof its curvature have been the subject of debates for decades. The GondwanideOrogeny generated the mylonitization of its Tonian–middle Cambrian basement(i.e., Sauce Chico Complex), accompanied by an intense hydrolysis whichproduced secondary muscovite (i.e., sericite), and the folding of the overlyingPaleozoic sedimentary cover. To evaluate the structural and tectonic evolutionof the Ventania System as a result of the interaction of its basement with theRío de la Plata Craton, we studied the anisotropy of magnetic susceptibility(AMS) and rock magnetism on samples of the Sauce Chico Complex. Rock magneticstudies suggest that paramagnetic minerals are the main carriers in the entireSauce Chico Complex. We suggest that our results reflect secondary muscovitegeneration due to mylonitization. AMS data reveal that the orientation of themagnetic foliation coincides to a large extent with the rock foliation.However, magnetic and rock foliation orientations are not uniform among thedifferent sampled units, displaying strikes between N 320° (NW) and N 345°(NNW) on average. Localities with different orientations are separated byregional strike-slip structures, referred to as tear faults, which have alsobeen reported and interpreted by previous authors. According to this, wesuggest that the variations detected between the orientation of the magneticand rock foliations of the different basement units may be the result of the rotationof crustal blocks bounded by tear faults. We also propose the existence of anew tear fault not previously recognized. Furthermore, a tear fault of regionalcharacter, known as the Sauce Chico Tear Fault, juxtaposes two distinct crustaldomains. The differential displacement of such domains could have contributednot only to different structural styles between blocks on both sides of theSauce Chico Tear Fault, but also to the curved shape of the Ventania Systemduring the progression of the Gondwanide deformation.