Crustal structure in high deformation zones: Insights from gravimetric and magnetometric studies in the Guacha Corral shear zone (Eastern Sierras Pampeanas, Argentina). (March 2018)

• Record Type: Journal Article
• Authors: Radice, Stefania; Lince Klinger, Federico; Maffini, M. Natalia; Pinotti, Lucio P.; Demartis, Manuel; D´Eramo, Fernando J.; Giménez, Mario; Coniglio, Jorge E.
• Is Part Of: Journal of South American earth sciences. Volume 82(2018)
• Page Start: 261
• Page End: 273
• Publication Date: 2018-03
• Subjects: Eastern Sierras Pampeanas -- Guacha Corral shear zone -- Magnetometry -- Gravimetric model -- 3D geometry; Geology -- Latin America -- Periodicals; Earth sciences -- Latin America -- Periodicals; Geology -- Antarctica -- Periodicals; Earth sciences -- Antarctica -- Periodicals; Geology -- Caribbean Area -- Periodicals; Earth sciences -- Caribbean Area -- Periodicals; Géologie -- Amérique latine -- Périodiques; Sciences de la terre -- Amérique latine -- Périodiques; Géologie -- Antarctique -- Périodiques; Sciences de la terre -- Antarctique -- Périodiques; Géologie -- Caraïbes (Région) -- Périodiques; Sciences de la terre -- Caraïbes (Région) -- Périodiques; Earth sciences; Geology; Antarctica; Caribbean Area; Latin America; Periodicals; 550.5
• DOI: 10.1016/j.jsames.2017.08.012
• Languages: English
• ISSNs: 0895-9811

Abstract

Abstract: The Guacha Corral shear zone (GCSZ) is represented by mylonites that were developed under amphibolites facies conditions from migmatitic protoliths. In this contribution, geophysical, petrological and structural data were combined to determine the 3D geometry of the GCSZ. New gravimetric, magnetometric and structural studies, along an E-W profile, were integrated with existing magnetotelluric and seismological data from a representative regional database of the Eastern Sierras Pampeanas. The zonation of different fabrics across the GCSZ suggests that the pre-existing heterogeneities of the protoliths played a key role in governing the degree of metamorphism of different regions. The low gravity anomalies observed in the GCSZ suggest a transitional boundary zone between the migmatitic and mylonitic domains, where highly deformed shear bands are interspersed with undeformed rocks, presenting gradual contacts. The mylonites in this shear zone show a considerably reduced density when compared to the migmatite protoliths. The density of the rocks gradually increases with depth until it reaches that of the protolith. These changes in the gravity values in response to density changes allowed us to infer a listric geometry at depth of the GCSZ. Low gravity anomalies in the profiles, in regions where high density rocks (migmatites) outcrop at the surface, modeled as buried granitic plutons. Graphical abstract: Image 1 Highlights: The geophysical data allowed determination of the boundaries and geometry of the Guacha Corral shear zone. Deformation of the shear zone reduced the density of the rocks. The Guacha Corral shear zone is listric at depth. Low gravity anomalies suggest an igneous body at depth below the shear zone.