One hundred fifty million years of intrusive activity in the Sør Rondane mountains (East antarctica): Implications for gondwana assembly

New U-Pb zircon ages for the younger phase of magmatism in the Sør Rondane Mountains (East Antarctica) are combined with published igneous and metamorphic zircon ages and show evidence for at least four thermal pulses: at 650–600 Ma, 580–550 Ma, ca. 530 Ma, and a magmatic tail between 510 and 500 Ma. No igneous U-Pb ages younger than 500 Ma have been found, in contrast to the situation in central and western Dronning Maud Land. Zircon Lu-Hf isotopic data are best explained as reflecting both crustal reworking and juvenile input, with the latter more obvious during the 580–550 Ma period. The Hf isotopic data, together with the presence of mafic and silica-undersaturated intrusives, argue against purely intracrustal melting as a petrogenetic process. Apart from the observed temporal trend, there is also a geographic trend in Hf isotopic compositions, with lower initial ε Hf values toward the northeast. However, the Hf isotopic shifts are gradual and do not show evidence for a dramatic change between the two previously defined metamorphic terranes. This observation, together with the long duration of magmatism, suggests that the Sør Rondane Mountains may be a collage of several different (sub-)terranes that were amalgamated over a longer period of time.