Age and Geochemistry of the Cape Burks Gabbroids (Russkaya Station Area, West Antarctica)

Resumo

The paper reports first geological, chemical, mineralogical, Sr–Nd chemical–isotope, and geochronological data on the gabbroid massif discovered on the Hobbs coast in the Cape Burks area, West Antarctica. The area is made up of compositionally diverse gabbroids that are intersected by thin vein and dike bodies of mafic, intermediate, and fesic composition. The gabbroids are represented by olivine and olivinefree gabbros and gabbronorites, with sharply subordinate troctolites, gabbro–anorthosites, and anorthosites. The U–Pb SHRIMP–II zircon age of the gabbroids and vein rocks was estimated at 100 ± 1 Ma. The gabbroids were supposedly emplaced in the upper crust in tectonically active conditions. The thickness of the pluton is no less than 2.5–3 km. The rocks were crystallized from a highly fractionated melt. Their composition was mainly determined by accumulation and fractional crystallization. The origin of vein felsic rocks was likely related to an evolved residual liquid. The igneous complex was formed in a within–plate geodynamic setting, and its primary melts were derived from a weakly LILE enriched lithospheric mantle.