THE LIVERPOOL LAND ECLOGITE TERRANE – A PIECE OF BALTICA WITHIN THE EAST GREENLAND CALEDONIDES?

The N-dipping Gubbedalen Shear Zone (GSZ), southern Liverpool Land, East Greenland Caledonides, separates a terrane of eclogites and garnet-amphibolites and minor ultramafics surrounded by granitoid migmatitic gneisses in the footwall from Silurian calc-alkaline intrusives in the hanging wall. Temperatures of c. 800 ^oC and a minimum pressure of 15 Kb for eclogitization are indicated by mineral paragenesis and mineral chemical data. ID-TIMS U-Pb ages of c. 400 Ma and c. 390 Ma on zircon and rutile, respectively, from the eclogites are interpreted as dating the eclogite metamorphism and subsequent exhumation. Pegmatites and granite dykes cutting across the eclogite bodies and their country rocks have been dated to c. 385 Ma. The granite dykes intruded contemporaneously with top-towards-S movement on GSZ and other sub-parallel contractional shear zones. This tectonomagmatic event is not recorded in the hanging wall. Highly discordant, inherited zircons from the eclogites, indicate an age of c. 1600-1650 Ma for the mafic protolith. This age is different from known episodes of Mesoproterozoic magmatism in NE Greenland, but is known from the Western Gneiss Region of South Norway, which was located close to Liverpool Land in most pre-Tertiary paleogeographic reconstructions. Ultramafic rocks (serpentenites), which are not known from the NE Greenland Eclogite Province further north, occur in both the Western Gneiss Region of Norway and Liverpool Land supporting our interpretation that the latter may be an ‘orphaned' block of Baltic basement sutured onto Laurentia.