151-1 Titanite Misorientation Records Deformation in Tuolumne Intrusive Suite, Sierra Nevada Batholith, CA

Session: Chronology of Orogenesis: Unlocking the Timelines of Mountain Building (Posters)

Presenting Author:

Authors:

Abstract:

Shear zones may make room for pluton emplacement by weakening the crust and facilitating the movement of magma. How the crust accommodates pluton emplacement, especially in the absence of active shearing, is not fully understood. Electron backscatter diffraction (EBSD) analysis of titanite can be used to recognize and characterize deformation in sheared plutons. Titanite readily (re)crystallizes in response to changes in temperature, pressure, and differential stress and records deformation as crystal lattice distortion. 

To understand how titanite is recording deformation during magmatic to submagmatic stages of pluton emplacement, we analyzed >200 titanite grains from three granodiorite samples of the Tuolumne Intrusive Suite in the Sierra Nevada batholith, California. Though these samples were characterized as non-deformed in the field, we find evidence for deformation in approximately 5% of the titanite grains. This deformation manifests as low angle boundaries and lattice distortion. To understand the fidelity of the titanite geochemical record from these misoriented zones, we use laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) to measure the geochemistry and U-Pb ages of titanite. We then compare the titanite ages to LA-ICPMS U-Pb zircon ages to assess the timing of deformation relative to pluton emplacement. Our results suggest that titanite is a sensitive enough recorder of deformation to be used to identify non-pervasive submagmatic deformation in nominally non-deformed plutons.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-5928

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