Continental palaeorift reactivations drive...

Continental palaeorift reactivations drive kimberlitic and alkaline magmatism: a case study from the Superior province of the Canadian shield.

Abstract

Kimberlites, carbonatites and alkaline silicate rocks occur in intraplate settings across all continents, with emplacement ages ranging from Mesoproterozoic to Quaternary. Their geodynamic nature remains a subject of vigorous debate, with various models linking them to development of subduction zones, rifts, plumes, and edge-driven convection. In this work, we demonstrate that emplacements of the Jurassic – Cretaceous kimberlites and alkaline intrusions of the Superior craton were controlled by a Mesozoic reactivation of the Neoproterozoic St. Lawrence paleorift system (SLPRS) in response to the development of the Atlantic Ocean. We draw parallels with kimberlite provinces of Baltica and Siberia, showing that kimberlitic magmatism there was similarly associated with Proterozoic paleorift systems subjected to Phanerozoic reactivations.We use regional aeromagnetic data to demonstrate that the Mesozoic kimberlites of the Kirkland Lake and Timiskaming fields and alkaline intruisons of the Monteregian Hills alkaline province are confined to the limbs of the SLPRS – Timiskaming and Ottawa-Bonnechere grabens, respectively. We reconstruct the Mesozoic evolution of the stress field in the Superior province via stress inversions of tensile fracture sets’ orientations measured at 22 sites in the Ordovician – Silurian carbonates present in south-eastern Superior. We apply fault slip and dilation tendency analyses to assess reactivation potentials of SLPRS normal faults under the calculated stress tensors. We analyze available geochronological data and depth-to-basement maps of Baltica and Eastern Siberia to constrain the structural settings of Arkhangelsk and Yakutia kimberlite provinces.We demonstrate that the intraplate intrusions of the Superior province were emplaced into sequentially reactivated SLPRS segments in response to the Mesozoic counter-clockwise rotation of the main extension axis (σ3) of the stress field from W-E to NW-SE. This sequential re-activation explains apparent age progression of magmatism in SLPRS along the NW- SE trend. In Arkhangelsk province, the kimberlites are associated with parallel N-S trending Proterozoic Kandalaksha and Leshukov paleorifts and are coeval with the Late Devonian development of the Timan – Pechora rift system along the eastern boundary of Baltica. In Siberia, the late Devonian kimberlites are emplaced in the then-active Viluy (in the south) and limbs of the West Verkhoyan (in the north) rift systems. The Mesozoic kimberlitic magmatism in Siberia seems to be mostly confined to the Sukhanov continental rift system and occurred in several pulses from Middle Triassic to Early Cretaceous, corresponding to the development of West Verkhoyan passive margin. The timing of kimberlitic magmatism cessation coincides with the docking of the Oloy volcanic arc, when Siberian stress field transitioned into a compressional state.We conclude that kimberlitic magmatism across the Laurasian platforms was primarily controlled by reactivations of the Proterozoic continental paleorift systems throughout the Phanerozoic in response to extensional stress orthogonal to the paleorifts’ axes. The results of numerical modelling of fault stress response validate this model for the Superior province of the Canadian shield. A similar quantitative approach is required to further validate this conclusion for other provinces of intraplate magmatism around the world.

Authors

Koptev E; Peace A

Publication Date

March 13, 2026

DOI

10.5194/egusphere-egu26-901

Associated Experts

Alexander Peace

Associate Professor, Faculty of Science

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