First evidence of eclogite facies metamorphism in the Shackleton Range, Antarctica: Trace of a suture between East and West Gondwana?

Abstract

The Shackleton Range in East Antarctica is part of the Pan-African collisional orogen related to the convergence between East and West Gondwana. In the northern Shackleton Range, alpine-type ultramafic rocks occur as lenses in high-grade gneisses. These include peridotite and pyroxenite that contain garnet and/or spinel in addition to olivine, orthopyroxene, and clinopyroxene. Thermobarometric results are in the range of 20–23 kbar and 710–810 °C, corresponding to a peak metamorphic gradient of ∼11 °C/km, typical of subduction-zone metamorphism. This finding is the first evidence of eclogite facies metamorphism in the Shackleton Range and, to our knowledge, the first documented eclogite facies ultramafic rocks in a Pan-African orogen. The ultramafic rocks are clear evidence of a suture zone within the northern Shackleton Range, which probably marks the convergence site between East and West Gondwana.