Reconstructing the metamorphic framework of East Antarctica through campaign-style detrital garnet Lu-Hf geochronology

Detrital garnet grains sampled along the margin of East Antarctica (70°E−175°E) yield laser ablation Lu−Hf dates that record the timing of regional metamorphism related to all major orogenies that built this large segment of the continent. Detrital garnet dates from the Ross Sea margin form a large population at ca. 600 Ma, marking the onset of convergence along the Pacific margin of East Antarctica during the Ross Orogeny. Marine sediments offshore northern Victoria Land and Terre Adélie Land contain minor ca. 600 Ma detrital garnet populations derived from the Ross orogen and large Paleoproterozoic populations at ca. 2000−1700 Ma from the Mawson Craton. The Wilkes Land offshore sediments include a prominent detrital garnet population at ca. 1200 Ma (Albany-Fraser-Wilkes Orogeny) and a minor distribution of ca. 600 Ma grains, possibly derived distally from the Ross orogen. Detrital garnet in marine sediments from Prydz Bay are dominated by Rayner Orogeny (ca. 1000−900 Ma) and Kuunga Orogeny (ca. 500−600 Ma) ages. Detrital garnet Lu-Hf populations tend to be systematically ≥10 m.y. older than the major populations of detrital zircon, titanite, and phosphate dates from the same areas. These age differences reflect the tendency of garnet to record the prograde and peak metamorphic history of orogenesis, rather than anatexis and the retrograde and cooling histories that are typically recorded by other detrital mineral geochronometers. Our findings demonstrate the potential of detrital garnet Lu-Hf geochronology for mapping orogenic provinces at the continental scale and reconstructing more complete metamorphic histories from the sedimentary archive.