Tracking halogen recycling and volatile loss in kimberlite magmatism from Greenland: Evidence from combined F-Cl-Br and δ37Cl systematics

Kimberlite magmatism occurs as a result of volatile fluxed melting the convecting upper mantle underlying cratonic lithospheric regions. During passage to Earth's surface, proto-kimberlite magma can interact with, and assimilate, variably enriched producing hybrid melts consisting asthenospheric components including contributions from metasomatic domains. The halogen elements (F, Cl, Br, I) chlorine isotope ratios (37Cl/35Cl) are increasingly used tracers recycled crustal materials within yet only rarely reported in analyses kimberlites. As result, origin distribution halogens kimberlite magmas is poorly constrained. Here, we present novel, combined elemental Br) isotopic (δ37Cl) data for 14 fresh samples North Atlantic Craton (NAC) West South-West Greenland. F composition kimberlites NAC appears be controlled by with minimal effect interaction metasomatized or loss during after emplacement. By contrast, Cl Br studied have undergone significant devolatilization dyke emplacement post-emplacement processes, whereby up 99% original budget was removed. Whilst all broadly follow same geochemical pattern, there exists some regional variability their systematics. northern Majuagaa mantle-like δ37Cl values −0.2 −0.5‰ [versus SMOC (standard mean ocean chloride)]. In dykes Nigerdlikasik Pyramidefjeld near southern craton margin display positive +0.4‰ +1.3‰, addition relative enrichment, which consistent assimilation crust-derived magmas. support scenario were sampled either an OIB-type reservoir through subduction-modified eruption. We prefer ascending assimilated Cl-rich, regions lithosphere.