首页|Early Palaeogene mafic-intermediate dykes, Robert Island, West Antarctica: Petrogenesis, zircon U-Pb geochronology, and tectonic significance
Early Palaeogene mafic-intermediate dykes, Robert Island, West Antarctica: Petrogenesis, zircon U-Pb geochronology, and tectonic significance
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NSTL
Wiley
Geochemical, geochronological, and Lu-Hf isotopic data for mafic-intermediate dykes on Robert Island, West Antarctica, are systematically investigated in order to decipher their petrogenesis and the genetic relationship between the South Shetland Islands and the north-western Antarctic Peninsula. These dykes are enriched in large-ion lithophile elements with significantly negative Nb and Ta anomalies, and low (Hf/Sm)(N) and (Nb/La)(N) and high Ba/La and Ba/Th ratios, with high epsilon(Hf)(t) values of +8.2 to +14.2. They were derived from partial melting of depleted mantle metasomatized by slab-derived fluids. Precise ages of 55-54 Ma for the dykes confirm the occurrence of Early Eocene magmatism on Robert Island, corresponding to the final peak of subduction-related magmatism. The available data suggest that Early Palaeogene (62-54 Ma) igneous rocks on the South Shetland Islands and the north-western Antarctic Peninsula are products of contemporaneous and different lithofacies magmatism with precursors originating from depleted mantle in a magmatic arc setting. Furthermore, the Early Palaeogene igneous activities were most likely associated with slab rollback and extension in fore-arc regions resulting from the decreasing convergence rate for the subduction of the Phoenix Plate beneath the Antarctic Plate at similar to 60 Ma.
NSTL
Wiley
