| Summary: | The 475 Ma Vega intrusive complex is part of the Bindal Batholith in north-central Norway. The complex compositionally zoned from east to west and is composed of the Ylvingen biotite granite, Vega granodiorite, and Fugleværet granodiorite units. Intrusive migmatite and quartz diorite are present along the northern contact of the complex where they intrude host rocks to the complex. Granodiorite and granite are peraluminous to strongly peraluminous, calcic-alkali–calcic, and magnesian, contain sillimanite, garnet, and cordierite, and metasedimentary, meta-igneous, mafic magmatic and ultramafic enclaves. Initial 87Sr/86Sr ratios for plutonic and intrusive migmatites range from 0.708 to 0.742 and εNd values range from -7.0 to -11.0. Granitic rock compositions, phases, and isotopic ratios are those of a classic “S-type” intrusion. Disrupted mafic dikes, mafic magmatic enclaves, and amphibolite enclaves are alkali–calcic, magnesian, metaluminous, and have isotopic and trace element abundances indicating a depleted mantle origin. Isotopic mixing models indicate that peraluminous and mafic rocks did not mix although enclave textures suggest that these magmas mingled. Metasedimentary host rocks to the complex are part of the Helgeland Nappe Complex in the Uppermost Allochthon of the Norwegian Caledonides. The polydeformed (D1–D3) rocks contain folded intrusive migmatitic dikes, suggesting that the complex was syntectonically emplaced during regional D3 deformation. Contact migmatitic rocks contain the assemblage muscovite + biotite + quartz + plagioclase+ K-feldspar + kyanite + staurolite + garnet which indicate that the host rocks followed a Barrovian prograde P–T path associated with crustal thickening that began prior to emplacement of the complex. Garnet-aluminosilicate-silica-plagioclase barometry resulted in estimates of emplacement pressures of 750 MPa on the eastern side the complex, whereas cordierite and muscovite on the western side of the complex formed at pressures between 500 MPa and 350 MPa. The range of ...
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