2026 Undergraduate Research Showcase

Asymmetric Stress Haloes Around Micro-inclusions in Metamorphic Garnet: Magnitudes and Implications

Document Type

Student Presentation

Presentation Date

4-24-2026

Faculty Sponsor

Dr. Matthew Kohn

Abstract

Theoretically, inclusions of one mineral inside another should develop either homogeneous stresses (in the inclusion) or radially symmetric stress gradients (in the host crystal). These stresses can be inferred from Raman peak position shifts and used to determine pressures and temperatures of crystal formation. In this study, we collected Raman spectroscopic maps across zircon inclusions in garnet to infer stress distributions both within the inclusions and in the surrounding garnet. Unlike theory, inclusions do not have homogeneous stress distributions. Considering four quadrants (NW, NE, SE, SW), opposing quadrants (e.g., NW-SE) have the same stress but differ from the opposing quadrant pair (e.g., NE-SW). Stress differences between NE-SW vs. NW-SE quadrants may reach ~1 kbar. Stresses in the host crystal parallel stresses in the inclusion – lowest in the NW-SE quadrants surrounding the inclusion and highest in the NE-SW quadrants. Stress heterogeneities should be quantitatively considered when trying to determine pressures and temperatures of mineral formation. These heterogeneities may additionally help explain why single-point analyses of multiple different mineral inclusions in the same host crystal often yield different stresses.

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