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Jean-Paul Liégeois
Earth Sciences
Geodynamics and mineral resources
Geodynamics and mineral resources
Publication details
Linnemann, U., Herbosch, A., Liégeois, J.P., Pin, C., Gärtner, A. & Hofmann, M. 2012. ‘The Cambrian to Devonian odyssey of the Brabant Massif within Avalonia: A review with new zircon ages, geochemistry, Sm-Nd isotopes, stratigraphy and palaeogeography’. Earth Science Reviews 112: 126-154. Amsterdam : Elsevier. DOI: http://dx.doi.org/10.1016/j.earscirev.2012.02.007. URL: http://dx.doi.org/10.1016/j.earscirev.2012.02.007 I.F. 6.942.
Article in a scientific Journal / Article in a Journal
This study provides an up-to-date and comprehensive review of the Early Palaeozoic evolution of the Brabant
Massif belonging to the Anglo-Brabant Deformation Belt. Situated at the southeastern side of Avalonia
microplate, it is the only well-known part of the northern passive margin of the Rheic Ocean. The Cambrian–
Silurian sedimentary pile is >13 km thick,with >9 km for the Cambrian only. The unraveling of this continuous
registration re!ects the successive rifting and drifting of Avalonia from the Gondwana mainland, followed by
soft-collisional processes with Baltica and "nally the formation of Laurussia. Based on recently established detailed
stratigraphy, sedimentology and basin development, on U–Pb LA-ICP-MS analyses of igneous and detrital
zircon grains along with geochemical data including Sm–Nd isotopes, a new geodynamic and palaeogeographic
evolution is proposed. Brabant Megasequence 1 (lower Cambrian to lowermost Ordovician,>9 km thick) represents
an embayment of the peri-Gondwanan rift from which the Rheic Ocean has evolved. Detrital zircon
ages demonstrate that the Brabant is a typical peri-Gondwanan terrane with a major Pan-African (Neoproterozoic
age) and a mixed West African and Amazonian source (Palaeoproterozoic, Archaean and some
Mesoproterozoic age). The transition towards the Avalonia drifting is marked by an unconformity and a
short volcanic episode. The northward drift of Avalonia towards Baltica is recorded by the Megasequence
2 (Middle to Upper Ordovician, 1.3 km thick). The source for Mesoproterozoic zircons vanished, as the result
of the Rheic Ocean opening and the isolation from Amazonian sources. The transition to Megasequence
3 is marked by a drastic change in palaeobathymetry and an important (sub)volcanic episode during a tectonic
instability period (460–430 Ma), re!ecting the Avalonia–Baltica soft docking as also shown by the
reappearance of Mesoproterozoic detrital zircons, typical of Baltica. Unradiogenic Nd isotope signature
(epsNd −4/−5) and TDM model ages (1.3–1.7 Ga) for Brabant magmatic rocks indicate an old recycled component.
Megasequence 3 (uppermost Ordovician to lowermost Devonian; >3.5 km thick) includes the
onset of a Silurian foreland basin that re!ects the tectonic inversion of the core of the massif (Brabantian
orogeny) in response to the Baltica–Avalonia–Laurentia collision. Finally, the comparison with the strikingly
similar Cambrian successions of the Harlech Dome (Wales, Avalonia) and theMeguma terrane (Nova Scotia,
peri-Gondwana) allows the construction of a new Early Cambrian palaeogeographic model for the
whole Avalonia microplate, in which the Meguma terrane is included.