The pre-orogenic detrital zircon record of the Peri-Gondwanan crust

Abstract

We present a statistical approach to data mining and quantitatively evaluating detrital age spectra for sedimentary provenance analyses and palaeogeographic reconstructions. Multidimensional scaling coupled with density-based clustering allows the objective identification of provenance end-member populations and sedimentary mixing processes for a composite crust. We compiled 58 601 detrital zircon U–Pb ages from 770 Precambrian to Lower Palaeozoic shelf sedimentary rocks from 160 publications and applied statistical provenance analysis for the Peri-Gondwanan crust north of Africa and the adjacent areas. We have filtered the dataset to reduce the age spectra to the provenance signal, and compared the signal with age patterns of potential source regions. In terms of provenance, our results reveal three distinct areas, namely the Avalonian, West African and East African–Arabian zircon provinces. Except for the Rheic Ocean separating the Avalonian Zircon Province from Gondwana, the statistical analysis provides no evidence for the existence of additional oceanic lithosphere. This implies a vast and contiguous Peri-Gondwanan shelf south of the Rheic Ocean that is supplied by two contrasting super-fan systems, reflected in the zircon provinces of West Africa and East Africa–Arabia.

New constraints from U–Pb dating of detrital zircons on the palaeogeographic origin of metasediments in the Talea Ori, central Crete

“…Their wall rocks are metasediments which contain a U-Pb age spectrum of detrital zircons with a dominant Ediacaran age peak and two age peaks during the Tonian and one at 1 Ga. Aysal et al (2012b) interpreted the amount of 6 % Mesoproterozoic zircons of the age spectrum of the detrital zircons of the wall rock as Avalonian/Amazonian related, but if we consider the Tonian-and Stenian-aged zircons as one age group (11 %, Grenvillian) then only 3 % zircons with an age between 1.15 Ga and 1.6 Ga are left. Tonian and Stenian zircons are common in the Central and East Sakarya Zone and are similar to the U-Pb age spectra of detrital zircons of NE Africa -Arabia (Stephan et al 2019) and East Gondwana derived terranes (Zulauf et al 2007). Late Devonian granitic-granodioritic gneisses, dated at around 370 Ma from the northern (Sea of Marmara) and southern (Aegean Sea) part of the Biga peninsula (Özmen & Reischmann, 1999; Pb/Pb single-zircon), are slightly older than the U-Pb age peak at 362 ± 4 Ma (n = 4, mean age) of the Late Devonian detrital zircons of the Talea Ori group.…”

Exploratory Analysis of Provenance Data Using R and the Provenance Package

“…For moderately sized datasets, stress values should be less than 10% [40]. For larger datasets, a higher dimensional solution may be necessary, using the optional parameter k of provenance's MDS function [50].…”

Detrital zircons and the interpretation of palaeogeography, with the Variscan Orogeny as an example

“…In the ongoing debate on the Palaeozoic evolution of the north Gondwana margin, summarized evidence for the existence of Armorican microcontinents that, during early Palaeozoic time, were separate from the Gondwana mainland, and refuted one-ocean models for the later Palaeozoic Variscides. In contrast however, Stephan et al (2018) argue for a different model based largely on the distribution of old detrital zircon crystals in the Variscan area: comparable conclusions were reached in a paper by Žák & Sláma (2017) who wrote on the early Palaeozoic detrital zircon record in central Bohemia. However, we reiterate the point here that zircon spectra are unable to detect the separation and drift history of 'suspect' microcontinents, but only reveal the original derivation of their age clusters.…”

“…If and when those microcontinents should ever be reunited with one another and with their original continent of Gondwana, the zircon age signatures of basement blocks and clastic sediments derived from them can be expected to be very similar or even identical. Contrary to the logic of Stephan et al (2018) and Žák & Sláma (2017), such observations of detrital zircon distribution should therefore not be misinterpreted for the Variscan Orogeny to preclude the existence, before collision, of separating oceans, as set out below.…”

“…The publications by Kroner et al (2007), Kroner & Romer (2013) and Stephan et al (2018Stephan et al ( , 2019 have compiled the available U-Pb laser inductively coupled plasma mass spectrometry ages of detrital zircons from various parts of the European Variscides, America, northern Africa and the Middle East (late Neoproterozoic -Early Devonian). They have convincingly demonstrated that those age spectra form very uniform groupings, but from that they concluded that all the sampled areas were part of a broad, contiguous shelf fringing the north of the Gondwana craton during early Palaeozoic time before the start of the main Variscan Orogeny.…”