From genesis to juxtaposition: the evolution of the Ivisârtoq greenstone belt, southwest Greenland

• Main Author: Mader, Marianne M.
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2005
• Subjects: Greenland; Godthåbsfjord; North Atlantic
• Online Access: https://research.library.mun.ca/6668/; https://research.library.mun.ca/6668/1/MarianneMader.pdf; https://research.library.mun.ca/6668/3/MarianneMader.pdf

The Ivisârtoq greenstone belt is situated ~40 km south of the Isua greenstone belt within the Godthåbsfjord region of southwest Greenland. This region is part of the Archean gneiss complex of Greenland, a major component of the 3800-2500 Ma North Atlantic Craton. Compared to the Isua greenstone belt, which has been the focus of intense study because it contains some of the oldest known (~ 3.8-3.7 Ga) rocks on Earth, little work has been carried out on the Ivisârtoq greenstone belt. The Ivisârtoq greenstone belt is exceptionally well-exposed in three dimensions with relief of 1200m, and primary features are better preserved here than in any other Archean greenstone belt in Greenland. Consequently, this belt provides an exceptionally good opportunity to characterise early to middle Archean magmatism, deformational processes, and tectonic environments. -- The Ivisârtoq greenstone belt was multiply deformed and metamorphosed at amphibolite facies. The belt forms an upright southwest-closing, V-shaped synform. This study concentrated on the 3 km thick southern limb of the synform, where the most complete section of the supracrustal rocks is preserved, and where there are pillow lava structures with way-up indicators. The southern limb was found to comprise a tectonostratigraphy made up of two main components, termed the northern and southern parts. These composite rock units differ in composition and intensity of deformation and are separated by a major high strain zone. -- The northern part of the belt is generally less deformed than the southern part and is characterized by heterogeneously deformed amphibolite, derived from variolitic and homogeneous basaltic pillow lavas, interlayered with boudins of olivine-bearing ultramafic rocks and quartz-feldspar-mica gneiss and schist. The southern part consists predominantly of strongly deformed rocks including banded amphibolite, homogeneous granitoid, gabbroic rocks, and a thick layer of predominantly quartz-feldspar-biotite- schist. -- New major and trace element ...