Crustal structure in high deformation zones: insights from gravimetric and magnetometric studies in the Guacha Corral shear zone (Eastern Sierras Pampeanas, Argentina)

RADICE, STEFANIA; LINCE KLINGER, FEDERICO; MAFFINI, MARÍA NATALIA; PINOTTI, LUCIO PEDRO; DEMARTIS, MANUEL; D'ERAMO, FERNANDO JAVIER; GIMÉNEZ, MARIO ERNESTO; CONIGLIO, JORGE ENRIQUE

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2017 vol. 82 p. 261 - 273

0895-9811

TheGuacha Corral shear zone (GCSZ) is represented by mylonites that were developedunder amphibolites facies conditions from magmatitic protoliths. In thiscontribution, geophysical, petrological and structural data were combined todetermine the 3D geometry of the GCSZ. New gravimetric, magnetometric andstructural studies, along an E-W profile, were integrated with existingmagnetotelluric and seismological data from a representative regional databaseof the Eastern Sierras Pampeanas. The zonation of different fabrics across theGCSZ suggests that the pre-existing heterogeneities of the protoliths played akey role in governing the degree of metamorphism of different regions. The lowgravity anomalies observed in the GCSZ suggest a transitional boundary zonebetween the migmatitic and mylonitic domains, where highly deformed shear bandsare interspersed with undeformed rocks, presenting gradual contacts. Themylonites in this shear zone show a considerably reduced density when comparedto the migmatite protoliths. The density of the rocks gradually increases withdepth until it reaches that of the protolith. These changes in the gravityvalues in response to density changes allowed us to infer a listric geometry atdepth of the GCSZ. Low gravity anomalies in the profiles, in regions where highdensity rocks (migmatites) outcrop at the surface, modelled as buried graniticplutons.