An Investigation of Magnetic Fabrics Using Anisotropy of Magnetic Susceptibility on the Pulo do Lobo Metasedimentary Unit across the South Iberian Shear Zone
Mentor 1
Dyanna Czeck
Start Date
28-4-2023 12:00 AM
Description
The Southern Iberian Shear Zone (SISZ), found in southwestern Spain, is a north-northwest/south-southeast trending suture zone of Variscan age related to an ocean closure during the collision between Gondwana and Laurussia which resulted in the formation of Pangea. A shear zone is a structure at which ductile deformation occurs as rocks slide past each other, equivalent to a fault, but deeper within the crust. After subsequent erosion, shear zones can be studied on the surface. The past motions of shear zones can be partially interpreted through measurement of the orientation of structural fabrics, or mineral alignments, that formed in response to deformation. The Southern Iberian Shear Zone followed the boundary between and affected two neighboring lithological packages: the Beja-Acebuches Metabasites (BAM), and the Pulo do Lobo metasedimentary unit (PdL). While more extensive studies have been conducted on the BAM, much less is known about the PdL in part due to a relative lack of tectonic lineations, a key structural fabric. AMS, or anisotropy of magnetic susceptibility, is a technique that can be applied to rocks that contain any magnetic minerals to provide a proxy for the absent tectonic fabrics. The technique involves applying a magnetic field to rock samples to obtain the magnitude and orientation of the magnetic signals induced in the rocks, as well as the shape and alignment of the magnetic grains that may form the fabrics. Thus, AMS can be used as a proxy for the lineations to help interpret the motion the PdL underwent during shear zone deformation. In turn, understanding the motions of the SISZ provide a foundation for further interpretation of the large-scale tectonics that formed the Iberian Peninsula.
An Investigation of Magnetic Fabrics Using Anisotropy of Magnetic Susceptibility on the Pulo do Lobo Metasedimentary Unit across the South Iberian Shear Zone
The Southern Iberian Shear Zone (SISZ), found in southwestern Spain, is a north-northwest/south-southeast trending suture zone of Variscan age related to an ocean closure during the collision between Gondwana and Laurussia which resulted in the formation of Pangea. A shear zone is a structure at which ductile deformation occurs as rocks slide past each other, equivalent to a fault, but deeper within the crust. After subsequent erosion, shear zones can be studied on the surface. The past motions of shear zones can be partially interpreted through measurement of the orientation of structural fabrics, or mineral alignments, that formed in response to deformation. The Southern Iberian Shear Zone followed the boundary between and affected two neighboring lithological packages: the Beja-Acebuches Metabasites (BAM), and the Pulo do Lobo metasedimentary unit (PdL). While more extensive studies have been conducted on the BAM, much less is known about the PdL in part due to a relative lack of tectonic lineations, a key structural fabric. AMS, or anisotropy of magnetic susceptibility, is a technique that can be applied to rocks that contain any magnetic minerals to provide a proxy for the absent tectonic fabrics. The technique involves applying a magnetic field to rock samples to obtain the magnitude and orientation of the magnetic signals induced in the rocks, as well as the shape and alignment of the magnetic grains that may form the fabrics. Thus, AMS can be used as a proxy for the lineations to help interpret the motion the PdL underwent during shear zone deformation. In turn, understanding the motions of the SISZ provide a foundation for further interpretation of the large-scale tectonics that formed the Iberian Peninsula.
