Geological mapping and tectonostratigraphy of mineralised mafic bands of the Timmiarmiut region of South-East Greenland. South-East Greenland Mineral Endowment Task Project, SEGMENT 2009-2014

Bands of mafic granulite with local ultramafic and possible meta-sedimentary rocks represent an exposure of the proto-lower crust in the Timmiarmiut region of the Thrym Complex. The mafic bands were intruded by the precursors to an extensive migmatite unit and numerous suites of granitic melts. The Timmiarmiut region has undergone a complex structural and metamorphic history with four Archean deformation events and at least three Proterozoic to Phanerozoic events. The earliest recognised event is the Timmiarmiut orogeny (DT), characterised by isoclinal folding, which resulted in a foliation in the mafic bands and the migmatite. Peak granulite metamorphism occurred pre- to syn-DT and lasted until the end of the Skjoldungen orogeny causing partial melting of mafic granulite and formation of the migmatitic texture. A NE-SW compressional regime termed the Skjoldungen orogeny resulted in isoclinal folding of the earlier foliation and formed a pervasive axial planar foliation traceable across the whole Thrym Complex. The Singertât stage brought about E-W compression and the major control on the present orientation of the mafic bands in the Timmiarmiut region. It is characterised by open to close folds and conjugate northwest trending dextral and northeast trending sinistral shear zones. These shear zones are associated with a retrogression in metamorphic facies to upper amphibolite, lower greenschist which is not seen in other areas. Locally, pyrrhotite, pyrite, chalcopyrite and ilmenite have precipitated along these shear zones and formed matrix-supported breccia. The final Archean deformation stage is coined D4 and gently folds the rocks in an E-W direction.