EGU21-10229
https://doi.org/10.5194/egusphere-egu21-10229
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

The corundum conundrum: Constraining the compositions of fluids involved in metasomatic corundum formation.

Vincent van Hinsberg1, Chris Yakymchuk2, Christopher Kirkland3, and Kristoffer Szilas4
Vincent van Hinsberg et al.
  • 1Earth and Planetary Sciences, McGill University, Montreal, Canada (hinsberg@gmx.net)
  • 2Earth and Environmental Sciences, University of Waterloo, Canada (Chris.Yakymchuk@uwaterloo.ca)
  • 3Timescales of Mineral Systems Group, School of Earth and Planetary Sciences, Curtin University, Australia (C.Kirkland@curtin.edu.au)
  • 4Department of Geosciences and Natural Resource Management, University of Copenhagen, Denmark (krsz@ign.ku.dk)

Corundum, including the variety ruby, is found in numerous locations in the Archaean North Atlantic Craton of southern Greenland. Corundum owes its occurrence to fluid-induced interaction among high-grade metamorphic lithologies of contrasting chemistry. Here, we present constraints on the conditions of corundum formation and the compositions of the fluids involved for the Storø and Maniitsoq ruby localities. We use thermodynamic modelling of mineral and mineral-fluid equilibria, and complement these with experimentally obtained data on mineral solubility to show that metasomatism took place at 650-725˚C and 7 kbar, involving a boron-rich, acidic fluid of low fO2 and low X(CO2). Aqueous concentrations of aluminium are low and indicate that corundum saturation is the result of residual aluminium enrichment rather than aluminium mobilisation. Intrusion of the ca. 2.55 Ga Qôrqut granite and associated fluid release is the likely source of boron, and U-Pb dating of rutile inclusions is consistent with a temporal link between ruby formation and granite emplacement. Interaction with meta-dunite and Fe-sulfides modified the oxidized magmatic fluid, introduced SO4, and produced the reduced, high XMg and K-rich fluid recorded by the corundum-bearing samples. These results highlight a complex interplay among lithologies involved in corundum-formation, but also demonstrate that corundum formation is a predictable part of the geological history where a magmatic intrusion expels a pulse of fluid through its lithologically heterogeneous carapace.

How to cite: van Hinsberg, V., Yakymchuk, C., Kirkland, C., and Szilas, K.: The corundum conundrum: Constraining the compositions of fluids involved in metasomatic corundum formation., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10229, https://doi.org/10.5194/egusphere-egu21-10229, 2021.

Corresponding presentation materials formerly uploaded have been withdrawn.