Barnes, Calvin G.Reid, KristinFrost, Carol D.Barnes, MelanieAllen, Charlotte MYoshinobu, Aaron S2015-12-080029-196Xhttp://hdl.handle.net/1885/32597The structurally lowest parts of the Upper Nappe of the Helgeland Nappe Complex consist primarily of migmatitic quartzofeldspathic gneiss with intercalated calc-silicate gneiss. Detrital zircons in the gneiss indicate an Ordovician depositional age. Migmatization via biotite dehydration reactions occurred at ~480 Ma at pressures of ~700 MPa; some migmatites were mobilized into cross-cutting diatexites. Diverse gabbroic to granitic plutons and dikes of the Bindal Batholith were emplaced from 448-424 Ma. They range from calc-alkaline to alkalic and most have initial 87Sr/86Sr <0.707 and εNd from 0 to -4. Pressures of emplacement were ca. 300 MPa. Shear zones with reverse shear sense cut 437 Ma intrusions, suggesting that contraction accompanied magmatism.Keywords: allochthon; batholith; dehydration; depositional sequence; emplacement; gneiss; magmatism; migmatization; nappe; Ordovician; shear zone; Silurian; zircon; Helgeland; Nordland; Norway20112016-02-24