Subduction-related volcanism in the Gula Nappe, southeastern Trondheim Nappe Complex, Central Norway
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Field and geochemical evidence from two meta-igneous complexes that occur in the Einunnfjellet-Savalen area, southeastern Trondheim Nappe Complex, indicates that both complexes formes in an arc-related setting. Metabasalts of the Lomsjødalen complex, that have been correlated with the Gula greenstone are primitive arc tholeites. Overlying metalliferous sediments suggest a spreading-ridge environment, however, which may signify either an opening marginal basin or the earliest stages of island-arc development. Mafic rocks of the Bangardsvola complex, previously correlated either with the Fundsjø Group or with rocks equivalent to the structurally lower Seve Nappe, have boninitic affinities uniquely characteristics of subduction-related settings. Meta-igneous rocks of the Einunnfjellet-Savalen area are lithologically and geochemically similar to Early Ordovician Norwegian ophiolites that formed in a suprasubduction-zone environment. In this study, the Lomsjødalen and Bangards- vola complexes are interpreted as components of an internally imbricated thrust sheet initially emplaced prior to or during the earliest Ordovician, then further translated and deformed during the Scandian orogeny. The associaition of primitive IAT, Boninite, and Fe- and Mn-rich metalliferous sediments is strongly analogous to the upper parts of the Troodos ophiolite, Cyprus.