Archean inheritance in Paleoproterozoic orogens: Example of the Southeastern Churchill Province, Trans-Hudson Orogen, Canada

Abstract

Deciphering the genesis and evolution of crustal lithotectonic blocks and defining the nature of their boundaries are prerequisites for assessing the nature and duration of crustal assembly processes through time and identifying new ore systems. However, ancient small-scale crustal masses and peripheral areas of large cratons have often been involved in subsequent orogenic cycles, heavily reworking and partially overprinting primary geological records, and hindering straightforward tectonic reconstruction. In this study, we present a new comprehensive summary of the geochronological record of the Southeastern Churchill Province (SECP), Trans-Hudson Orogen, Québec, Canada. New time-space diagrams and distribution maps of the Archean to Paleoproterozoic bedrock units form the foundation of our understanding of the tectonic history and cratonization processes in this region. The SECP records an Archean evolution from c. 2920–2735 Ma TTG magmatism forming a newly defined nucleus crustal block, the Koksoak Domain; c. 2735–2690 Ma orthopyroxene-TTG and hybrid magmatism at the margins of the latter; c. 2690–2620 Ma tholeiitic to calc-alkaline volcanism, partial melting of basement-rocks, and basin development upon extensional tectonics in its core; and a period of tectonic quiescence until c. 1.9 Ga. The units of the Koksoak Domain feature a similar magmatic evolution, in terms of timing and chemistry, as the Douglas Harbour Domain of the NE Superior Craton and perhaps the basement of the Meta Incognita microcontinent, defining the new Ungava Bay Terrane. The Paleoproterozoic record of the SECP provides evidence for the reactivation of inherited structures at the lithospheric scale, limited strike-slip displacement of Archean blocks, and structural control on endowment. These findings align with the previously proposed model of successive accretion of crustal blocks over approximately 100 million years (c. 1900–1800 Ma). Our work emphasizes the necessity of tracking lithotectonic blocks and their boundaries through time, especially in terranes that have been subjected to multiple orogenic cycles.