The Eoarchaean foundation of the North Atlantic Craton
Penelope J. Lancaster, Craig D. Storey, Chris J. Hawkesworth, 2015. "The Eoarchaean foundation of the North Atlantic Craton", Continent Formation Through Time, N. M. W. Roberts, M. Van Kranendonk, S. Parman, S. Shirey, P. D. Clift
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The Archaean North Atlantic Craton underpins much of North America, Greenland and northern Europe, and incorporates the Earth’s oldest extant continental crust. This paper reviews the current understanding of the region’s crustal evolution, and considers our ability to investigate interrelationships between different fragments of the North Atlantic Craton. Detrital zircons from Mesoproterozoic to Cambrian basal sediments in NW Scotland have been re-examined in light of new data from the Archaean Tarbet supracrustal unit and the Palaeoproterozoic Rubha Ruadh granite. Hf model ages are recorded from 4160 to 1410 Ma, peaking at c. 3350 Ma, and are associated with U–Pb crystallization ages from 3670 to 1070 Ma, peaking at c. 2700 and 1700 Ma. The Rubha Ruadh granite is consistent with partial melting of Northern Region basement without contamination by juvenile magmas or supracrustal material, while the Tarbet Supracrustals record a minimum model age of c. 3200 Ma. Each of these units records Hf model ages that imply remelting of Eoarchaean (4000–3600 Ma) crust. Similar distributions of crystallization and model ages have been identified around the North Atlantic Craton, suggesting that Eoarchaean crust was once extensive in the region and constitutes the foundation of both Scotland and the North Atlantic Craton.
All new zircon U–Pb-Hf-O data from this study are available at www.geolsoc.org.uk/SUP18776.
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The continental crust is our archive of Earth history, and the store of many natural resources; however, many key questions about its formation and evolution remain debated and unresolved:
What processes are involved in the formation, differentiation and evolution of continental crust, and how have these changed throughout Earth history?
How are plate tectonics, the supercontinent cycle and mantle cooling linked with crustal evolution?
What are the rates of generation and destruction of the continental crust through time?
How representative is the preserved geological record?
A range of approaches are used to address these questions, including field-based studies, petrology and geochemistry, geophysical methods, palaeomagnetism, whole-rock and accessory-phase isotope chemistry and geochronology. Case studies range from the Eoarchaean to Phanerozoic, and cover many different cratons and orogenic belts from across the continents.