Abstract
The 440±5 Ma Bremanger Granitoid Complex (BGC), west Norwegian Caledonides, comprises tonalites, granodiorites and minor granites. The BGC is coeval with a nearby subduction-related gabbronoritic/dioritic intrusion (the 443±4 Ma Gasoy Intrusion) and an ophiolite complex generated in a back-arc basin (the 443±3 Ma Solund-Stavfjord Ophiolite Complex). The BGC has a restricted isotopic variation (⊂Nd440Ma=+0.04 to –2.21, 87Sr/86Sr440 Ma=0.7045 to 0.7054) indicating a substantial mantle component, but it is enriched in crustal material relative to the primitive parts of the gabbronoritic rocks of the Gasoy Intrusion (⊂Nd440 Ma=+1.67, 87Sr/86Sr440 Ma=0.7048). The chondrite-normalised REE patterns are fractionated [(La/Yb)N ~8 to ~16], smooth or with negative or positive Eu anomalies. Geochemical modelling suggests that the BGC does not represent residual melts produced by fractional crystallisation of basic magma, but is compatible with partial melting of mafic source rocks with various amounts of H2O. Residual garnet is suggested by HREE depletion, indicating a minimum pressure of 9–10 kbar during melting.
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