The Gubbedalen Shear Zone; a terrane boundary in the East Greenland Caledonides : A structural and geochronological study

• Main Author: Augland, Lars Eivind
• Other Authors: Arild Andresen og Fernando Corfu
• Format: Master Thesis
• Language: English
• Published: 2007
• Subjects: geokjemi tektonikk petrologi eologi eklogitt granitoider ØstGrønland Grønland; VDP::450; Greenland; Hodal; Hurry Inlet; Liverpool Land; Storefjord; East Greenland; Grønland; Østgrønland
• Online Access: http://hdl.handle.net/10852/12437; http://urn.nb.no/URN:NBN:no-16029

Late Ordovician-Early Silurian magmatism, probably in a continental arc setting, was responsible for the generation of the Hurry Inlet Granite batholith of Liverpool Land, East Greenland. The emplacement of this batholith occurred in at least two phases, one at c. 445 Ma, and one at c. 438 Ma. A major pluton, the Hodal-Storefjord Monzodiorite was emplaced at c. 424 Ma, possibly related to delamination of a suprasubduction mantle wedge. Eclogites on Liverpool Land were metamorphosed at c. 399 Ma, possibly as a part of the Baltic subducted slab. It is here proposed that uplift and initial exhumation took place by buoyancy-driven imbrication of the subducted crust. Later exhumation is proposed to have occurred in a transpressional setting, where thrusting under amphibolite facies conditions on a restraining bend was the main mechanism of uplift. This thrusting was initiated no later than c. 386 Ma, as constrained by intrusion of syntectonic granite dikes. Simultaneous extensional displacements of the Upper Plate led to extrusion. This, together with erosion, contributed to exhumation. A rutile cooling temperature from the dated eclogite show that exhumation of the high grade terrane to a crustal level with temperatures below c. 400 °C (c. 15 km if an average geotherm is considered) was not achieved earlier than c. 370 Ma. Much of the exhumation was also achieved by extensional displacement on the Gubbedalen Extensional Detachment Fault.