Event Title

Major Element Geochemical Changes Across a Transect of the Southern Iberian Shear Zone

Presenter Information

Dulce Hernandez- Blanchard

Mentor 1

Dyanna Czeck

Location

Union Wisconsin Room

Start Date

27-4-2018 1:00 PM

Description

Interactions of tectonic plates cause deformation in rocks. A shear zone is a tabular zone of rocks that has a measurable thickness in which strain is localized when two sections of rock smear against each other at depth. Water and other fluids can change the deformation style of shear zones, strongly influencing the heterogeneity of deformation in the Earth’s crust. Fluids in deformation zones are transient, so are difficult to study in situ, but they may leave behind their signatures by altering rock chemistry or enabling metamorphic reactions and showing microstructural evidence. The research I am participating in is investigating the major geochemical changes across one shear zone, the Southern Iberian Shear Zone (SISZ), located in southwest Spain. The rocks analyzed in this study are the Acebuches Metabasites which are found on the north side of the SISZ. Prior to deformation and metamorphism, the metabasites were midocean ridge basalts, rocks with homogeneous chemistry and mineralogy. During deformation, the rocks metamorphosed to banded amphibolites; near the shear zone, the rocks underwent a second retrograde metamorphic event to locally change them into chlorite greenschists. The SISZ largely affects rocks with relatively simple geochemistry, metabasites, so shear zone related changes in chemistry are relatively easy to identify. Major element geochemistry was conducted across transects from outside to inside the SISZ. Major element geochemical changes in the rocks induced by fluid interaction were primarily responsible for deformation localization and strain softening.

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Apr 27th, 1:00 PM

Major Element Geochemical Changes Across a Transect of the Southern Iberian Shear Zone

Union Wisconsin Room

Interactions of tectonic plates cause deformation in rocks. A shear zone is a tabular zone of rocks that has a measurable thickness in which strain is localized when two sections of rock smear against each other at depth. Water and other fluids can change the deformation style of shear zones, strongly influencing the heterogeneity of deformation in the Earth’s crust. Fluids in deformation zones are transient, so are difficult to study in situ, but they may leave behind their signatures by altering rock chemistry or enabling metamorphic reactions and showing microstructural evidence. The research I am participating in is investigating the major geochemical changes across one shear zone, the Southern Iberian Shear Zone (SISZ), located in southwest Spain. The rocks analyzed in this study are the Acebuches Metabasites which are found on the north side of the SISZ. Prior to deformation and metamorphism, the metabasites were midocean ridge basalts, rocks with homogeneous chemistry and mineralogy. During deformation, the rocks metamorphosed to banded amphibolites; near the shear zone, the rocks underwent a second retrograde metamorphic event to locally change them into chlorite greenschists. The SISZ largely affects rocks with relatively simple geochemistry, metabasites, so shear zone related changes in chemistry are relatively easy to identify. Major element geochemistry was conducted across transects from outside to inside the SISZ. Major element geochemical changes in the rocks induced by fluid interaction were primarily responsible for deformation localization and strain softening.