scholarly journals The Krummedal supracrustal sequence around inner Nordvestfjord, Scoresby Sund, East Greenland

1974 ◽  
Vol 67 ◽  
pp. 1-34
Author(s):  
A.K Higgins
Keyword(s):  
Amphibolite Facies ◽  
Fold Belt ◽  
East Greenland ◽  
Facies Metamorphism ◽  
Sedimentary Succession ◽  
Middle Proterozoic

The Krummedal supracrustal sequence is a lower to middle Proterozoic sedimentary succession widely represented in the Caledonian fold belt of the Scoresby Sund region. Around inner Nordvestfjord laterally variable sequences of pelitic, semipelitic and psammitic rocks occur. The sequences of different areas ranging from 2500 m to more than 8000 m in thickness are described but no formal subdivision is attempted. High amphibolite facies metamorphism, migmatisation, emplacement of granite intrusions and several phases of deformation appear to relate to an orogenic episode giving dates in the range 900-1200 m.y. Caledonian orogenesis is represented by a relatively weak retrogressive metamorphic phase, westward displacements on major thrusts and emplacement of granite intrusions.

scholarly journals A high-pressure granulite facies complex in north-west Payers Land, East Greenland fold belt

1981 ◽  
Vol 29 ◽  
pp. 161-174
Author(s):  
Hans Christian Larsen
Keyword(s):  
High Pressure ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Geochemical Data ◽  
Fold Belt ◽  
East Greenland ◽  
North West ◽  
Gneiss Complex ◽  
High Pressure Granulite ◽  
Facies Metamorphism

Aeromagnetic, geological and geochemical data demonstrate the presence of a high-pressure, granu­Iite-facies gneiss complex about 400 km2 in area within a previously almost unexplored nunatak region between latitudes 74°30 and 75°N in northern East Greenland. The gneiss complex is surrounded and in part overthrust by supracrustal rocks of very high amphibolite facies, including garnet-clinopyroxene rocks of eclogitic affinity. A magnetically anomalous area is related to exposures of granulite facies rocks, whereas the surrounding supracrustals give rise to a magnetic smooth zone. Several, independent sets of observations indicate that the granulite facies metamorphism and the high amphibolite facies metamor­phism were related to the same metamorphic event. Maximum temperatures of about 740°C and maximum pressures of about 12.5 kb were reached (kyanite formation) later decreasing to about 10 kb (sillimanite formation). Comparisons with other parts of the East Greenland fold belt suggest a probable Archaean origin for the central gneiss complex and an early or middle Proterozoic age for the granulite and amphibolite facies metamorphism. There are no indications of Caledonian metamorphic events, in contrast to the previously assumed Caledonian origin for the area.

scholarly journals Progress report on geochronological investigations in the crystalline complexes of the East Greenland Caledonian fold belt between 72° and 74°N

1976 ◽  
Vol 80 ◽  
pp. 127-133
Author(s):  
D.C Rex ◽  
A.R Gledhill ◽  
A.K Higgins
Keyword(s):  
Progress Report ◽  
Geological History ◽  
Fold Belt ◽  
East Greenland ◽  
History Of ◽  
Crystalline Complexes Of ◽  
Middle Proterozoic

In the summer of 1974 two of the authors (D. C. R. & A. R. G.) collected samples from vanous crystalline units in the innerfjord region ofthe Caledonian fold belt between 72° and 74°N. with a view to testing current hypotheses of the geological history of the region. The only dates so far available from this region are a few K-Ar mineral ages reported by Haller & Kulp (1962) all of which reflect Caledonian orogenesis. In the Scoresby Sund region isotopic work on crystalline units comparable to some of those reported on here has yielded Archaean and middle Proterozoic as well as Caledonian ages (Hansen et al., 1973, 1974; Rex& Gledhill, 1974; Friderichsen & Higgins, this report).

scholarly journals Reconnaissance for mineral occurrences in North-East Greenland (76°–78°N)

1994 ◽  
Vol 162 ◽  
pp. 163-168
Author(s):  
S.M Jensen ◽  
H Stendal
Keyword(s):  
Present Knowledge ◽  
Stream Sediment ◽  
Normal Faults ◽  
Fold Belt ◽  
East Greenland ◽  
Geochemical Anomalies ◽  
North East ◽  
Economic Significance ◽  
Incompatible Elements ◽  
Middle Proterozoic

Reconnaissance for indications of potentially economic mineralisation in the Caledonian fold belt of North-East Greenland has shown that stream sediment geochemical anomalies and mineral occurrences are related to Lower-Middle Proterozoic and Caledonian skarns, Caledonian shear and thrust zones, and breccias in post-Jurassic normal faults. None of the mineral showings are of economic significance. Mineralised rock samples, stream sediment silt samples and panned stream sediment heavy mineral concentrates generally have low contents of metals and incompatible elements, and only few areas stand out as being geochronically anomalous. On the basis of the present knowledge of the geology of the region the mineral potential is considered low.

scholarly journals Structure of the Storstrømmen shear zone, eastern Hertugen af Orléans Land, North-East Greenland

1994 ◽  
Vol 162 ◽  
pp. 103-112
Author(s):  
R.A Strachan ◽  
I.R Tribe
Keyword(s):  
Shear Zone ◽  
Greenschist Facies ◽  
Amphibolite Facies ◽  
Fold Belt ◽  
East Greenland ◽  
North East ◽  
Mineral Assemblages ◽  
Basement Gneiss

The Storstrømmen shear zone is a NNE-trending belt of steep, heterogeneously deformed gneisses and mylonites, at least 8 km wide, which transects the basement gneiss complexes of the Caledonian fold belt between Dronning Louise Land and Hertugen af Orleans Land. Shear criteria indicate a consistent sinistral sense of displacement parallel to a gently-plunging L-S fabric. Mineral assemblages and fabrics within the mylonites indicate that mylonitisation was initiated under low amphibolite facies conditions and continued within the greenschist facies. The shear zone is reworked by late, steep brittle faults which are associated with cataclasis and local metamorphic retrogression.

DIVING DEEPER INTO THE PICURIS OROGEN: UPPER AMPHIBOLITE FACIES METAMORPHISM AND BRITTLE DEFORMATION ALONG THE PLOMO SHEAR ZONE

2020 ◽  
Author(s):  
Adrian E. Castro ◽  
◽  
Chloe Bonamici ◽  
Christopher G. Daniel ◽  
Danielle Shannon Sulthaus
Keyword(s):  
Shear Zone ◽  
Amphibolite Facies ◽  
Brittle Deformation ◽  
Facies Metamorphism

scholarly journals Metamorphic evolution and U-Pb zircon SHRIMP geochronology of the Belizário ultramafic amphibolite, Encantadas Complex, southernmost Brazil

2003 ◽  
Vol 75 (3) ◽  
pp. 393-403 ◽  
Author(s):  
Léo A. Hartmann ◽  
João O.S. Santos ◽  
Jayme A.D. Leite ◽  
Carla C. Porcher ◽  
Neal J. Mcnaughton
Keyword(s):  
Ultramafic Rock ◽  
Greenschist Facies ◽  
Amphibolite Facies ◽  
Rio De La Plata ◽  
Metamorphic Evolution ◽  
Río De La Plata ◽  
La Plata ◽  
Shrimp Geochronology ◽  
Facies Metamorphism ◽  
Magnesian Basalt

The integrated investigation of metamorphism and zircon U-Pb SHRIMP geochronology of the Belizário ultramafic amphibolite from southernmost Brazil leads to a better understanding of the processes involved in the generation of the Encantadas Complex. Magmatic evidence of the magnesian basalt or pyroxenite protolith is only preserved in cores of zircon crystals, which are dated at 2257 ± 12 Ma. Amphibolite facies metamorphism M1 formed voluminous hornblende in the investigated rock possibly at 1989 ± 21 Ma. This ultramafic rock was re-metamorphosed at 702±21 Ma during a greenschist facies eventM2; the assemblage actinolite + oligoclase + microcline + epidote + titanite + monazite formed by alteration of hornblende. The metamorphic events are probably related to the Encantadas Orogeny (2257±12 Ma) and Camboriú Orogeny (~ 1989 Ma) of the Trans-Amazonian Cycle, followed by an orogenic event (702±21 Ma) of the Brasiliano Cycle. The intervening cratonic period (2000-700 Ma) corresponds to the existence of the Supercontinent Atlantica, known regionally as the Rio de la Plata Craton.

scholarly journals Precambrian metamorphic complexes in the East Greenland Caledonices (72°–74°N) – their relationship to the Eleonore Bay Group, and Caledonian orogenesis

1981 ◽  
Vol 104 ◽  
pp. 5-46
Author(s):  
A.K Higgins ◽  
J.D Friderichsen ◽  
T Thyrsted
Keyword(s):  
Metamorphic Complex ◽  
East Greenland ◽  
Late Proterozoic ◽  
Isotopic Studies ◽  
Lower Palaeozoic ◽  
Caledonian Orogeny ◽  
Proterozoic Basement ◽  
Basement Gneiss ◽  
Metamorphic Complexes ◽  
Middle Proterozoic

Results are presented of regional geological reconnaissance and local detailed studies. The new fjeld work, together with isotopic studies, has made possibie a provisional reassignment of metamorphic, plutonic and deformational events recorded in the different rock units to Archaean and Proterozoic, as well as Caledonian, orogenic episodes. The infracrustal elements of the 'central metamorphic complex' are considered to be essentiaIly Archaean - early Proterozoic basement gneiss complexes, and are overlain by middle Proterozoic metasedimentary sequences. The late Proterozoic and Lower Palaeozoic sediments have arestricted outcrop at present levels of exposure. During the Caledonian orogeny the late Proterozoic cover sequences appear to have become detatched from their older metamorphic 'basernent' along a decollement surface, but the nature of this contact is usually obscured by Caledonian metamorphic effects. The main characteristics of the different rock units are described. Detailed relationships are illustrated by studies of four areas: Nunatakgletscher-Eremitdal, Knækdalen and adjacent areas, Kap Hediund, and Tærskeldal-Forsblads Fjord-Randenæs.

scholarly journals Archaean U-Pb zircon ages from the Scoresby Sund region, East Greenland

1987 ◽  
Vol 134 ◽  
pp. 19-24
Author(s):  
B.T Hansen ◽  
A.K Higgins ◽  
B Borchardt
Keyword(s):  
Fold Belt ◽  
East Greenland

U-Pb analyses on zircons are reported for two rock colleetions from infracrustal complexes within the East Greenland Caledonian fold belt in the Scoresby Sund region. Calculated minimum ages range from 2800 to 2965 Ma, and are the oldest ages obtained in the region using this method.

scholarly journals Regional geology and 1:500 000 mapping in North-East Greenland

1990 ◽  
Vol 148 ◽  
pp. 16-20
Author(s):  
N Henriksen
Keyword(s):  
Geological Mapping ◽  
Fold Belt ◽  
East Greenland ◽  
Regional Geology ◽  
Field Mapping ◽  
North East ◽  
General Geology ◽  
Geological Map

A three-year field mapping programme was initiated in 1988 aiming at regional geological studies and geological mapping in North-East Greenland between latitudes 75° and 78°N. This region encompasses relatively little known parts of the Caledonian fold belt and the overlying post-Caledonian sequences, which lie north of the better known regions of central East Greenland (Henriksen, 1989). Major aims of the programme include compilation a 1:500 000 geological map, and an understanding of the general geology of the region.

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