Scientific publications

The paper discusses the tectono-thermal evolution of the Bunger Hills granulite complex located in the Circum-East Antarctic mobile belt. The complex comprises a Paleoproterozoic layered suite which consists of foliated and migmatitic garnet cordierite-sillimanite-bearing gneiss and mafic orthogneiss intruded by plutons of gabbro, monzogabbro, monzodiorite, and granite of the charnockite series. The indicative mineral assemblages in metapelitic granulites (paragenesis of Zn-poor hercynite with quartz, intergrowth of exsolved ilmenite and ulvöspinel) as well as geothermobarometry (Grt–Opx, Ti-in-Quartz, ternary feldspar, Ti-Mag–Ilm) records provide evidence for ultrahigh-temperature (>900 °C) metamorphism. The P–T paths modeled by Theriak/Domino reflect two episodes of the metamorphic evolution: (1) isobaric heating at 6–7 kbar up to ~940–1030 °C, (2) near-isobaric or slightly compressive cooling at 5–6 kbar till ~750 °C. Considering previous results on U–Pb zircon and monazite geochronology, both episodes can be matched with two late Mesoproterozoic tectono-thermal events relating to the second stage of the evolution of the Albany–Fraser Orogen, which encompasses the Bunger Hills region as its westernmost extremity. The prograde P–T trajectory is associated with an extensional tectonic regime with isobaric heating of rocks at mid-crustal levels under high-heat flux until the conditions of UHT metamorphism. The retrograde trajectory reflects a late-orogenic event causing crustal thickening. This scenario describes the tectonic development of long-lived accretionary orogens, where crustal thinning alternates with short term thickening periods responsible for synchronous cooling of the lithosphere.