Detrital zircon in a supercontinental setting: locally derived and far-transported components in the Ordovician Natal Group, South Africa

Abstract

U-Pb and Lu-Hf signatures of detrital zircon from conglomerates and sandstones of the Ordovician Natal Group, South Africa were determined using LA-ICPMS. The basal conglomerates are dominated by Palaeo-to Mesoarchaean detrital zircon with ε Hf-values from +3 to-4 with minor Mesoproterozoic input, indicating a proximal source in the Kaapvaal Craton and minor input from rocks of the Natal Sector of the Mesoproterozoic Namaqua-Natal province. The sandstones are all dominated by a combination of juvenile Mesoproterozoic zircon and Neoproterozoic zircon derived from Mesoproterozoic rocks that were reworked during the Pan-African Orogeny. Several sedimentary sequences from former Gondwana with Neoproterozoic to Permian depositional ages show similar detrital zircon signatures. Sedimentary sequences of such vast temporal and geographical distribution are unlikely to have been fed by a single source, making it more likely that these sequences were fed by several different (Pan-Gondwana) source terranes with closely similar U-Pb and Lu-Hf zircon signatures. The results show that source terrane non-uniqueness can make ascertaining sedimentary provenance from detrital zircon impossible, and should be taken as a reminder when using detrital zircon as evidence for far reaching conclusions in basin evolution studies and palaeogeography.

Review of the Cambrian Pampean orogeny of Argentina; a displaced orogen formerly attached to the Saldania Belt of South Africa?

“…typical of southern Gondwanan sources in general (Kristoffersen et al, 2016). One source probably was in the Brasiliano-Pan-African orogenic belt that resulted from the closure of the Adamastor Ocean (Frimmel et al, 2013;Rapela et al, 2011) and references therein); another source probably was in the EAAO (Rapela et al, 2007(Rapela et al, , 2016).…”

Visualizing, interpreting and comparing detrital zircon age and Hf isotope data in basin analysis – a graphical approach

“…Even so, the approach is less than straightforward, at least as long as ‘source’ is equated with protosource. We have argued elsewhere that protosource signatures are not necessarily sufficiently specific to be related to an identifiable rock unit in crystalline basement (Kristoffersen et al ., ), and in particular that formation of supercontinents in the geological past may have led to large‐scale and long‐lived sedimentary homogenization systems in intra(super)continental basins (Andersen, ; Andersen et al ., ). Multiple cycles of erosion‐transport‐deposition and post‐depositional modification followed by supercontinental breakup may separate the detrital zircon found in any sand or sandstone from the protosource(s) in which the zircon originally crystallized.…”

Detrital Zircon U-Pb Data for Jurassic–Cretaceous Strata from the South-Eastern Verkhoyansk-Kolyma Orogen—Correlations to Magmatic Arcs of the North-East Asia Active Margin

“…Detrital and Magmatic zircon U-Pb analytical results tables are provided in Supplementary Materials. Histograms were constructed using the detzrcr software (version 1.0, University of Oslo, Oslo, Norway) [104].…”