Evaluating potential links between ultramafic cumulates and cratonic mantle lithosphere from the Mesoarchaean Akia Terrane, SW Greenland

• Main Authors: Barrett, Natasha, Waterton, Pedro, Liu, Jingao, Woodland, Sarah, Aarestrup, Emil, Pearson, D. Graham, Szilas, Kristoffer
• Format: Conference Object
• Language: English
• Published: 2022
• Subjects: Greenland; Miaggoq; Ulamertoq; Webb; Fiskefjord; North Atlantic
• Online Access: https://curis.ku.dk/portal/da/publications/evaluating-potential-links-between-ultramafic-cumulates-and-cratonic-mantle-lithosphere-from-the-mesoarchaean-akia-terrane-sw-greenland(4ac91b46-d01e-46b1-9983-9d6ff8de5bde).html; https://conf.goldschmidt.info/goldschmidt/2022/meetingapp.cgi/Paper/11898

The Akia Terrane, SW Greenland, is a rare location where it is possible to study both Archean ultramafic magmatism and cratonic mantle-derived peridotite xenoliths from the same geographical area. We present a comprehensive dataset (n=50) of Re–Os isotopes, highly siderophile elements (Os, Ir, Ru, Pd, Pt, Re), and in-situ trace elements of four well-preserved trondjemite–tonalite–granodiorite (TTG)-hosted ultramafic bodies (Amikoq, Miaggoq, Seqi, and Ulamertoq) within the Akia Terrane. We compare our results with new and existing data from North Atlantic Craton (NAC) mantle xenoliths to evaluate the timing and potential genetic links between sub-continental lithospheric mantle (SCLM) evolution and the formation of the Fiskefjord ultramafic cumulate magmas. While similarities exist between cumulate and mantle-derived peridotites based on their major elements, clear differences are observed in their first-row transition elements and isotope systematics, supporting previous studies that propose a magmatic cumulate origin for the Fiskefjord ultramafics [1]. The Fiskefjord ultramafics from this study exhibit a sharp TRD model age peak at ⁓3.1 Ga that significantly pre-dates previously reported TRD model ages for the NAC mantle xenoliths [2]. This rules out the possibility that the parental magmas for the ultramafic cumulates are directly complementary to SCLM residues and requires either lateral motion of lithospheric mantle or large scale overprinting of lithospheric mantle compositions after crust formation had ceased. This highlights some of the complications that arise with simple crust-mantle coupling models and the repercussions of voluminous ultramafic magmatism in the Archean prior to NAC mantle lithosphere evolution. [1] Szilas, K., Van Hinsberg, V., McDonald, I., Næraa, T., Rollinson, H., Adetunji, J., & Bird, D. (2018). Highly refractory Archaean peridotite cumulates: Petrology and geochemistry of the Seqi Ultramafic Complex, SW Greenland. Geoscience Frontiers, 9(3), 689–714. [2] Wittig, N., Webb, M., ...