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- Korstgård, John A., et al.
(författare)
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Magnetic anomalies and metamorphic boundaries in the southern Nagssugtoqidian orogen, West Greenland
- 2006
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Ingår i: Geological Survey of Denmark and Greenland Bulletin. - 1811-4598 .- 1604-8156. ; 11, s. 179-184
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Tidskriftsartikel (refereegranskat)abstract
- Within the southern Nagssugtoqidian orogen in West Greenland metamorphic terrains of both Archaean and Palaeoproterozoic ages occur with metamorphic grade varying from low amphibolite facies to granulite facies. The determination of the relative ages of the different metamorphic terrains is greatly aided by the intrusion of the 2 Ga Kangâmiut dyke swarm along a NNE trend. In Archaean areas dykes cross-cut gneiss structures, and the host gneisses are in amphibolite to granulite facies. Along Itilleq strong shearing in an E-W-oriented zone caused retrogression of surrounding gneisses to low amphibolite facies. Within this Itivdleq shear zone Kangâmiut dykes follow the E-W shear fabrics giving the impression that dykes were reoriented by the shearing. However, the dykes remain largely undeformed and unmetamorphosed, indicating that the shear zone was established prior to dyke emplacement and that the orientation of the dykes here was governed by the shear fabric. Metamorphism and deformation north of Itilleq involve both dykes and host gneisses, and the metamorphic grade is amphibolite facies increasing to granulite facies at the northern boundary of the southern Nagssugtoqidian orogen. Here a zone of strong deformation, the Ikertôq thrust zone, coincides roughly with the amphibolite-granulite facies transition. Total magnetic field intensity anomalies from aeromagnetic data coincide spectacularly with metamorphic boundaries and reflect changes in content of the magnetic minerals at facies transitions. Even the nature of facies transitions is apparent. Static metamorphic boundaries are gradual whereas dynamic boundaries along deformation zones are abrupt.
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| 3. |
- Bonow, Johan M., et al.
(författare)
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A multi-disciplinary study of Phanerozoic landscape development in West Greenland
- 2007
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Ingår i: Geological Survey of Denmark and Greenland Bulletin: Review of Survey activities 2006. - 1604-8156. ; :13, s. 33-36
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Tidskriftsartikel (refereegranskat)abstract
- The western margin of the Greenland craton has been muchless stable in the Phanerozoic than previously thought. Thisnew insight has come from close integration of independentdata sets: geomorphological analysis of large-scale landscapes,apatite fission track analysis (AFTA), onshore and offshorestratigraphy and analysis of onshore fault and fracture sys -tems. Each data set records specific and unique parts of theevent chronology and is equally important to establish a con-sistent model. A key area for understanding the Mesozoic-Cenozoic landscape evolution and into the present is theuplifted part of the Nuussuaq Basin, where remnants of pla-nation surfaces cut across the Cretaceous to Eocene sedimen-tary and volcanic rocks. Our integrated analysis concludedthat the West Greenland mountains were formed by lateNeogene tectonic uplift (Fig. 1) and also provided newinsight into early Phanerozoic development. To understandour model, we present the different methods and the resultsthat can be deduced from them.
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