Event Title

Major element geochemistry of the Pulo do Lobo metasedimentary rocks affected by the Southern Iberian Shear Zone, Andalusia, Spain

Presenter Information

Nancy Duque
Adam Honts

Mentor 1

Dr. Dyanna Czeck

Location

Union 260

Start Date

27-4-2018 1:00 PM

Description

A shear zone is a narrow band of rocks that are highly strained due to tectonic forces that preserves a detailed record of deformation history. The Southern Iberian Shear Zone (SISZ) is a 60 km long shear zone in southwestern Spain that was active approximately 300 million years ago. On one side of the SISZ, metasedimentary rocks of the Pulo do Lobo (PdL) formation include a mixture of schists and quartzites deformed during shearing. During deformation, fluids may interact with rocks and facilitate or enhance deformation. The fluids themselves are transient, so studying their effects directly in ancient structures is unfeasible. However, the fluids may leave altered rock chemistry, metamorphic reactions, and/or distinctive microstructural evidence. Little is known about the major element geochemical changes across the PdL caused by the SISZ. This project is a preliminary major geochemical analysis of 14 PdL samples taken near the SISZ. The primary goal is to determine whether geochemical changes related to deformation and fluid interaction can be distinguished from initial PdL heterogeneity. Major element geochemical data have been collected using X-Ray Fluorescence. Among the 14 samples, there were 3 distinct groups: high, intermediate, and low silica. We determined that the low silica samples are the best targets for further evaluation. In one of the transects, there were three PdL samples in this group, so we were able to evaluate two altered samples (closer to the SISZ) compared to the least altered sample furthest from the SISZ. Many of the major elements show consistent patterns: MnO, MgO, Fe2O3, K2O, P2O5, and Al2O3 show enrichment, and SiO2, Na2O, and CaO show depletion. 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.

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Apr 27th, 1:00 PM

Major element geochemistry of the Pulo do Lobo metasedimentary rocks affected by the Southern Iberian Shear Zone, Andalusia, Spain

Union 260

A shear zone is a narrow band of rocks that are highly strained due to tectonic forces that preserves a detailed record of deformation history. The Southern Iberian Shear Zone (SISZ) is a 60 km long shear zone in southwestern Spain that was active approximately 300 million years ago. On one side of the SISZ, metasedimentary rocks of the Pulo do Lobo (PdL) formation include a mixture of schists and quartzites deformed during shearing. During deformation, fluids may interact with rocks and facilitate or enhance deformation. The fluids themselves are transient, so studying their effects directly in ancient structures is unfeasible. However, the fluids may leave altered rock chemistry, metamorphic reactions, and/or distinctive microstructural evidence. Little is known about the major element geochemical changes across the PdL caused by the SISZ. This project is a preliminary major geochemical analysis of 14 PdL samples taken near the SISZ. The primary goal is to determine whether geochemical changes related to deformation and fluid interaction can be distinguished from initial PdL heterogeneity. Major element geochemical data have been collected using X-Ray Fluorescence. Among the 14 samples, there were 3 distinct groups: high, intermediate, and low silica. We determined that the low silica samples are the best targets for further evaluation. In one of the transects, there were three PdL samples in this group, so we were able to evaluate two altered samples (closer to the SISZ) compared to the least altered sample furthest from the SISZ. Many of the major elements show consistent patterns: MnO, MgO, Fe2O3, K2O, P2O5, and Al2O3 show enrichment, and SiO2, Na2O, and CaO show depletion. 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.