Isotopic age and metamorphic history of the banded gneiss at Danmarkshavn, East Greenland

Steiger, R.; Harnik-Šoptrajanova, Gorica; Zimmermann, Emil; Henriksen, N

doi:10.1007/bf00392849

Cited by 43 publications

(34 citation statements)

References 28 publications

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“…The Archean ages, c . 2.8–2.4 Ga, are comparable to ages obtained from the crystalline basement gneisses south of latitude 72°30′N (Kalsbeek et al ., 1993; Thrane, 2002), and to the only other Archean age known north of 73°N, which is from a tonalitic gneiss near Danmarkshavn (76°46′N) (Steiger et al ., 1976; Nutman & Kalsbeek, 1994).…”

Section: Pre‐caledonian Evolution Of the Payer Land Gneiss Complexmentioning

confidence: 99%

Metamorphic history of high‐pressure granulites in Payer Land, Greenland Caledonides

Elvevold

Thrane

Gilotti

2002

Journal Metamorphic Geology

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A high‐P granulite facies gneiss complex occurs in north‐west Payer Land (74°28′−74°47′N) in the central part of the East Greenland Caledonian (Ordovician–Devonian) orogen. High‐P metamorphism of the Payer Land gneiss complex resulted in formation of the assemblages Grt + Cpx + Amp + Qtz + Ru ± Pl in mafic rocks, and Grt + Ol + Cpx + Opx + Spl in rare ultramafic pods. Associated metapelites experienced anatexis in the kyanite stability field. Peak metamorphic assemblages formed around 800–850 °C at pressures of c. 1.4–1.7 GPa, corresponding to crustal depths of c. 50 km. Mafic granulites contain abundant reaction textures, including the replacement of garnet by symplectites of Opx + Spl + Pl, indicating that the high‐P event was followed by decompression while the granulites remained at elevated temperatures. Charnockitic gneisses from Payer Land show evidence of late Archean (c. 2.8–2.4 Ga) crustal growth and subsequent Palaeoproterozoic (c. 1.85 Ga) metamorphism. The gneiss complex experienced intense reworking during the Caledonian continental collision. On the basis of Caledonian monazite ages recorded from the high‐P anatectic metapelites, the clockwise P–T evolution and formation of the high‐P granulite facies assemblages is related to Caledonian crustal thickening, which resulted in formation of eclogites approximately 300 km north of Payer Land. The Payer Land granulites comprise a metamorphic core complex, which is separated from the overlying low‐grade supracrustal rocks (the Neoproterozoic Eleonore Bay Supergroup) by a late Caledonian extensional fault zone, the Payer Land Detachment. The steep, nearly isothermal, unloading P–T path recorded by the granulites can be explained by erosional and tectonic unroofing along the Payer Land Detachment.

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Section: Pre‐caledonian Evolution Of the Payer Land Gneiss Complexmentioning

confidence: 99%

Metamorphic history of high‐pressure granulites in Payer Land, Greenland Caledonides

Elvevold

Thrane

Gilotti

2002

Journal Metamorphic Geology

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“…Biotite cooling ages recorded by Rb-Sr mineral isochrons from a Danmarkshavn garnet websterite and a banded amphibolitic gneiss are 326 ± 6 Ma (Brueckner, Gilotti & Nutman, 1998) and 321 ± 10 Ma (Steiger et al 1976), respectively, suggesting a prolonged cooling history. Biotite cooling ages recorded by Rb-Sr mineral isochrons from a Danmarkshavn garnet websterite and a banded amphibolitic gneiss are 326 ± 6 Ma (Brueckner, Gilotti & Nutman, 1998) and 321 ± 10 Ma (Steiger et al 1976), respectively, suggesting a prolonged cooling history.…”

Section: Discussionmentioning

confidence: 97%

“…An enclave of Archaean gneiss has been recognized (Steiger et al 1976;Nutman & Kalsbeek, 1994) within the dominantly Palaeoproterozoic gneisses. They are dominated by quartzofeldspathic orthogneisses derived from the calc-alkaline batholiths, with less abundant paragneiss.…”

Section: A Host Gneissesmentioning

confidence: 99%

Geology and timing of dextral strike-slip shear zones in Danmarkshavn, North-East Greenland Caledonides

2006

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The North-East Greenland eclogite province is divided into a western, central and eastern block by the sinistral Storstrømmen shear zone in the west and the dextral Germania Land deformation zone in the east. A family of steep, NNW-striking dextral mylonite zones in the Danmarkshavn area are geometrically and kinematically similar to the ductile Germania Land deformation zone, located 25 km to the east. Amphibolite facies deformation at Danmarkshavn is characterized by boudinage of eclogite bodies within quartzofeldspathic host gneisses, pegmatite emplacement into the boudin necks and subsequent deformation of pegmatites parallel to gneissosity, a widespread component of dextral shear within the gneisses, and localization of strain into 10-50 m thick dextral mylonite zones. The gneisses and concordant mylonite zones are cut by a swarm of weakly to undeformed, steeply dipping, E-W-striking pegmatitic dykes. Oscillatory-zoned zircon cores from two boudin neck pegmatites give weighted mean 206 Pb/ 238 U sensitive, high mass resolution ion microprobe (SHRIMP) ages of 376 ± 5 Ma and 343 ± 7 Ma. Cathodoluminescence images of these zircons reveal complex additional rims, with ages from ranging from c. 360 to 320 Ma. Oscillatory-zoned, prismatic zircons from two late, cross-cutting pegmatites yield weighted mean 206 Pb/ 238 U SHRIMP ages of 343 ± 5 Ma and 332 ± 3 Ma. Zircons from the boudin neck pegmatites record a prolonged growth history, marked by fluid influx, during amphibolite facies metamorphism beginning at c. 375 Ma. The cross-cutting pegmatites show that dextral deformation in the gneisses and ductile mylonite zones had stopped by c. 340 Ma. Ultrahigh-pressure metamorphism in the eastern block at 360 Ma requires that the Greenland Caledonides were in an overall contractional plate tectonic regime. This, combined with 20 % steep amphibolite facies lineations in the eclogites, gneisses and mylonites suggests that dextral transpression may have been responsible for a first stage of eclogite exhumation between 370 and 340 Ma.

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“…Some studies (e.g. Hofmann & Grauert, 1973; Krogh & Davis, 1973; Grauert et al ., 1974 ; Hänny et al ., 1975 ; Steiger et al ., 1976 ; O’Hara & Gromet, 1983) have shown that Sr isotopic equilibration was not reached over distances of more than centimetres during amphibolite facies regional metamorphism. On the other hand, reports of many well‐fitted Rb–Sr isochrons giving the time of metamorphism of regionally metamorphosed rocks suggest that Sr isotopic equilibration can take place on a regional scale (e.g.…”

Section: Introductionmentioning

confidence: 99%

Contrasting responses of Rb–Sr systematics to regional and contact metamorphism, Laramie Mountains, Wyoming, USA

Patel

1999

Journal Metamorphic Geology

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Archean supracrustal sequences of pelitic, quartzitic, calcareous and mafic compositions in the central Laramie Mountains, Wyoming, have been affected by two metamorphic events: a 1.78 Ga amphibolite‐grade regional metamorphism, and a 1.43 Ga contact metamorphism resulting from the intrusion of the Laramie Anorthosite Complex (LAC). Rb–Sr whole‐rock isotopic data from both outside and within the LAC contact aureole define a linear array that lies along a 1.78 Ga isochron. This date has been independently established as the time of amphibolite facies regional metamorphism associated with collision of the Archean Wyoming province and the Proterozoic Colorado province along the Cheyenne belt. The Rb–Sr isotopic data require that Sr was redistributed during regional metamorphism on a scale of at least tens of metres. Although within the 2 km‐wide aureole of LAC the pelitic rocks were thermally metamorphosed at temperatures greater than 800 °C, none of the whole‐rock Rb–Sr data from samples within the LAC aureole show evidence of resetting at 1.43 Ga. It is interpreted that the regional metamorphism involved fluid transport which facilitated Sr isotopic resetting, whereas the contact metamorphism occurred in a relatively dry environment in which isotopic mobility was restricted to centimetre‐scale or less. Rb–Sr data for biotite, feldspar and whole rock from a regional metamorphosed pelitic schist give an isochron age of 1450±40 Ma, which is interpreted as a cooling age resulting from crustal uplift. Rb–Sr data for biotite, quartz+feldspar and whole rock from a pelitic schist affected by contact metamorphism give an isochron age of 1420±43 Ma, the time of isotopic re‐equilibration in response either to crustal uplift or to both contact metamorphism and crustal uplift. This study demonstrates that although the response of isotopic systems to metamorphism is complex, isotopic data provide insight into metamorphic processes that is difficult to obtain by other means.

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Isotopic age and metamorphic history of the banded gneiss at Danmarkshavn, East Greenland

Cited by 43 publications

References 28 publications

Metamorphic history of high‐pressure granulites in Payer Land, Greenland Caledonides

Metamorphic history of high‐pressure granulites in Payer Land, Greenland Caledonides

Geology and timing of dextral strike-slip shear zones in Danmarkshavn, North-East Greenland Caledonides

Contrasting responses of Rb–Sr systematics to regional and contact metamorphism, Laramie Mountains, Wyoming, USA

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