Seminar Details:

• Date: Wednesday, August 28, 2024
• Time: 11 am – 12 pm AEDT
• Location: Room 449 (Conference Room), Madsen (F09) – School of Geosciences
• Zoom Link: https://uni-sydney.zoom.us/j/81762246983?from=addon

Advances in Integrating Petrochronological and Numerical Models of High-Grade Metamorphic Systems

Abstract

Petrochronological data (constraints on the pressure-temperature–time (P–T–t) evolution of metamorphic rocks) provide key constraints on the evolution of high-grade, lower crustal rock systems such as granulites. However, these datasets only ever capture a snapshot of the complete journey of a single particle through an orogenic cycle. Integrating petrochronological data with numerical models, from the kilometre (plate) to micron (mineral) scale, enables the development of a more holistic view of the large-scale evolution of these systems. By combining analytical data from rock samples with modelling, we can better contextualise and refine the models and move towards a better understanding of how the lower crust responds. To achieve this, several workflows are currently in development to integrate the petrological modelling software MAGEMin within the geodynamic modelling software Underworld. This integration will allow for the simultaneous consideration of mineral and plate scale numerical models anchored by geological data to better understand regional evolution.

These tools are applied to the granulite facies metagabbros found in the Fraser Zone in the Albany-Fraser orogen to shed light on the region’s evolution. The modelling work includes reconstructing the extension of the area prior to collision and simulating the emplacement of the Fraser zone metagabbro to understand its large-scale evolution. Additionally, diffusion, decay, and ingrowth modelling of uranium-lead isotopes in metamorphic and detrital zircons provide insights into age variations, while diffusion modelling of garnet compositional zoning in metagabbro and metapelites helps constrain the P–T evolution, which is then compared to existing and newly acquired geological datasets. The models also provide insights into how sedimentation and magmatism interact – a key relationship that has been speculated to be important in the formation of the nickel deposits found in this region. This integrated approach not only enhances our understanding of specific regions like the Fraser Zone but also lays the groundwork for future advancements in combining geodynamic and petrological modelling, constrained by geological data.