Precambrian sources of Early Paleozoic SE Gondwana sediments as deduced from combined Lu–Hf and U–Pb systematics of detrital zircons, Takaka and Buller terrane, South Island, New Zealand

Abstract

Combined U–Pb–Lu–Hf isotope investigations on small detrital zircons (30–120 μm) using solution ID-MC-ICPMS and ID-TIMS were carried out on Cambrian–Ordovician sedimentary rocks from the Buller and Takaka terranes of the northeastern South Island of New Zealand. The sediments in these two terranes are considered correlatives of voluminous sedimentary belts in the Lachlan and Adelaidian fold belts of southeastern Australia and in the Wilson and Bowers terranes of Antarctica (SE Gondwana). In order to constrain the sources of these sediments, we use combined U–Pb and Lu–Hf data from detrital zircons, enabling the calculation of Lu–Hf model ages that date the crustal residence time of the zircon protoliths. The Lu–Hf age information is combined with Nd model ages for the bulk sediments. U–Pb systematics of the detrital zircons show age maxima at 0.5–0.6 Ga, 0.8 Ga, and 1.0–1.2 Ga, with initial εHf values for the New Zealand detrital zircons ranging from + 14.9 to − 27.6. These zircon age populations broadly agree with age patterns for sediments found elsewhere in SE Gondwana, confirming a link between the Paleozoic belts of New Zealand and Australia–Antarctica. Lu–Hf model ages obtained from the detrital zircon populations range from 0.9 to 3.7 Ga with an age maximum at ~ 1.5 Ga. A comparison with average crustal residence ages of potential source regions indicates that the Ross-Delamerian orogen of present day Eastern Australia and Antarctica, and crustal provinces in Western Australia are likely sources. The presence of sources as distant as Western Australia suggests long transport pathways for the zircons, possibly via large river systems. A comparison of model age distributions for sediments from Australia, Antarctica, and New Zealand indicate that the Australian sediments have been fed by an additional Archean source (~ 2.8–3.1 Ga), in contrast to sedimentary rocks from New Zealand and Antarctica that lack an Archean model age peak.