This thesis investigates igneous rocks from northwestern Graham Land, Antarctic Peninsula, in terms of their chemistry and timing of magmatism. In northwestern Graham Land, plutonic and hypabyssal rocks of the Antarctic Peninsula batholith and volcanic rocks of the Antarctic Peninsula Volcanic Group crop out in almost equal proportions. These igneous rocks intrude and unconformably overlie low-grade metasedimentary 'basement' of the Trinity Peninsula Group (?Carboniferous to Triassic). The Mesozoic to Cenozoic subduction-related plutonic rocks range from gabbro to granite, with granodioritic compositions predominating. Mafic to intermediate hypabyssal intrusions cutting the plutonic, volcanic and 'basement' rocks are common. Major and trace element data, as well as petrographical data, from igneous rocks of the Danco Coast and Palmer Archipelago indicate a 'normal' calc-alkaline suite typical of active continental margins. Fractional crystallisation of a mafic parental magma seems to be the dominant process responsible for the range of igneous lithologies observed in the study area.