New Discovery of the Early Cretaceous Volcanic Rocks on the Barton Peninsula, King George Island,Antarctica and Its Geological Significance

Ages determined with the ⁴⁰Ar/³⁹Ar isotopic system affirms the Early Cretaceous volcanic activity in the Barton Peninsula, King George Island, Antarctica. Two specimens of basaltic andesite collected from the lower‐most volcanic sequence of the peninsula were irradiated and analyzed in different experiments, yielding an identical age spectrum, and two magmatic thermal events of the Early Cretaceous (120.4±1.6 Ma, 119±1 Ma) and Early Tertiary (53.1±1.5 Ma, 52±1 Ma) are distinguished. The former is interpreted to represent the primary cooling age of basaltic andesite, whereas the latter is the thermal reset age caused by the intrusion of granitic pluton. These new ages clearly indicate that volcanism was active during the Early Cretaceous on the Barton Peninsula and that intensive hydrothermal alteration and mineralization of Mesozoic volcanic rocks resulted from Tertiary magmatism.