High-temperature ultramafic complexes in the North Norwegian Caledonides: I - Regional setting and field relationships.
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Forkortet.Four major (25-100 km\u00B2) ultramafic complexes were developed in the Sørøy Nappeduring the second phase of Finnmarkian deformation in the North NorwegianCaledonides. They were emplaced into layered mafic intrusions and show broadlysimilar emplacement histories and petrographic variations suggesting a relatedpetrogenesis. The Nordre Bumannsfjord, Melkvann and Kvafjord group ofultramafic complexes developed in part by emplacement of both replacive anddilational ne-normative ultramafic sheets and dykes which progressivelyfragmented the layered olivine gabbro envelope. The Reinfjord ultramaficcomplex contains pronounced, subhorizontal modal layering and evidence of atleast 3 major magmatic events. The intrusive sequences and petrographic variations represented in thecomplexes suggest the succesive emplacement of mantle-derived magmas with adiminishing number of liquidus phases, accompanied by in situ liquid-crystalfractionation, subsidiary hybridization and metasomatism.