Major element geochemistry of the Pulo do Lobo metasedimentary rocks affected by the Southern Iberian Shear Zone, Andalucia, Spain
Mentor 1
Dyanna Czeck
Location
Union Wisconsin Room
Start Date
5-4-2019 1:30 PM
End Date
5-4-2019 3:30 PM
Description
A shear zone is a zone that is comprised of rocks that are more highly strained than adjacent rocks. The Southern Iberian Shear Zone (SISZ), formed during collision of two tectonic plates, extends across the northwestern parts of Andalucia, southwestern Spain into Portugal. Metasedimentary rocks including a mixture of schists and quartzites in the Pulo do Lobo (PdL) formation are found on the south side of the SISZ. During shear zone deformation, fluids interact with rocks and enhance or facilitate deformation processes. The fluids themselves are transient, but they may leave signatures of altered rock chemistry, metamorphic reactions, and/or distinctive microstructural evidence. For this project, X-Ray Fluorescence was used on 20 samples in the PdL near the SISZ to determine the major element geochemical changes related to deformation and fluid interaction. We determined that the intermediate silica samples are the best targets for further evaluation. In one transect, there were ten PdL samples in this group, so we were able to evaluate nine altered samples (closer to the SISZ) compared to the least altered sample furthest from the SISZ. In an isocon plot, many of the major elements show consistent patterns: MnO, MgO, Fe2O3, K2O, P2O5, and CaO show enrichment, and SiO2, Na2O, and Al2O3 show depletion. The major elements were plotted versus distance from the SISZ and compared to qualitative strain magnitude, determined by the degree of fabric formation. Several of the major elements show a pattern with strain. At the transition to the strongly foliated highly strained samples, K2O, P2O5,MnO, MgO, and CaO increase and Na2O and SiO2decrease. These trends suggest the deformation related geochemical signature in the PdL may be separated from heterogeneity of the PdL itself, and the PdL warrants further study for fluid/rock interaction during shear zone deformation.
Major element geochemistry of the Pulo do Lobo metasedimentary rocks affected by the Southern Iberian Shear Zone, Andalucia, Spain
Union Wisconsin Room
A shear zone is a zone that is comprised of rocks that are more highly strained than adjacent rocks. The Southern Iberian Shear Zone (SISZ), formed during collision of two tectonic plates, extends across the northwestern parts of Andalucia, southwestern Spain into Portugal. Metasedimentary rocks including a mixture of schists and quartzites in the Pulo do Lobo (PdL) formation are found on the south side of the SISZ. During shear zone deformation, fluids interact with rocks and enhance or facilitate deformation processes. The fluids themselves are transient, but they may leave signatures of altered rock chemistry, metamorphic reactions, and/or distinctive microstructural evidence. For this project, X-Ray Fluorescence was used on 20 samples in the PdL near the SISZ to determine the major element geochemical changes related to deformation and fluid interaction. We determined that the intermediate silica samples are the best targets for further evaluation. In one transect, there were ten PdL samples in this group, so we were able to evaluate nine altered samples (closer to the SISZ) compared to the least altered sample furthest from the SISZ. In an isocon plot, many of the major elements show consistent patterns: MnO, MgO, Fe2O3, K2O, P2O5, and CaO show enrichment, and SiO2, Na2O, and Al2O3 show depletion. The major elements were plotted versus distance from the SISZ and compared to qualitative strain magnitude, determined by the degree of fabric formation. Several of the major elements show a pattern with strain. At the transition to the strongly foliated highly strained samples, K2O, P2O5,MnO, MgO, and CaO increase and Na2O and SiO2decrease. These trends suggest the deformation related geochemical signature in the PdL may be separated from heterogeneity of the PdL itself, and the PdL warrants further study for fluid/rock interaction during shear zone deformation.
