Rubidium-strontium isotopic age measurements of plutonic igneous rocks in eastern Ellsworth Land and northern Antarctic Peninsula, Antarctica

Abstract

Eastern Ellsworth Land plutonic igneous rocks intrusive into folded Jurassic sedimentary rock have been dated at 102 to 109 m.y. At Tisne point on the northwest coast of the Antarctic Peninsula, granodiorite is dated at 96 m.y. Ages are established with Rb-Sr isochrons using whole rock samples and biotite concentrates. A correlation between the igneous rocks of eastern Ellsworth Land and the Andean intrusive suite of the Antarctic Peninsula is deduced from similar trends in triangular variation plots of Fe-(K + Na)-Mg and K-Na-Ca. Field relationships, geochronology, and geochemistry indicate that Cretaceous plutonism of southern South America and of the Antarctic Peninsula extended at least as far south as Ellsworth Land and probably continued into the Ford Ranges near the Ross Sea.