scholarly journals Prograde amphibolite facies to ultrahigh-pressure transition along Nordfjord, western Norway: Implications for exhumation tectonics

Tectonics ◽  
2007 ◽  
Vol 26 (1) ◽  
pp. n/a-n/a ◽  
Author(s):  
David J. Young ◽  
Bradley R. Hacker ◽  
Torgeir B. Andersen ◽  
Fernando Corfu
Keyword(s):  
Amphibolite Facies ◽  
Ultrahigh Pressure ◽  
Western Norway

Pre-Caledonian granulite and gabbro enclaves in the Western Gneiss Region, Norway: indications of incomplete transition at high pressure

2000 ◽  
Vol 137 (3) ◽  
pp. 235-255 ◽  
Author(s):  
M. KRABBENDAM ◽  
A. WAIN ◽  
T. B. ANDERSEN
Keyword(s):  
High Pressure ◽  
Shear Zones ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Ultrahigh Pressure ◽  
Western Gneiss Region ◽  
Ultrahigh Pressure Metamorphism ◽  
Mountain Belts ◽  
Orogenic Cycle ◽  
Highly Strained

The Western Gneiss Region of Norway is a continental terrane that experienced Caledonian high-pressure and ultrahigh-pressure metamorphism. Most rocks in this terrane show either peak-Caledonian eclogite-facies assemblages or are highly strained and equilibrated under late-Caledonian amphibolite-facies conditions. However, three kilometre-size rock bodies (Flatraket, Ulvesund and Kråkenes) in Outer Nordfjord preserve Pre-Caledonian igneous and granulite-facies assemblages and structures. Where these assemblages are preserved, the rocks are consistently unaffected by Caledonian deformation. The three bodies experienced high-pressure conditions (20–23 kbar) but show only very localized (about 5%) eclogitization in felsic and mafic rocks, commonly related to shear zones. The preservation of Pre-Caledonian felsic and mafic igneous and granulite-facies assemblages in these bodies, therefore, indicates widespread (∼ 95%) metastability at pressures higher than other metastable domains in Norway. Late-Caledonian amphibolite-facies retrogression was limited. The degree of reaction is related to the protolith composition and the interaction of fluid and deformation during the orogenic cycle, whereby metastability is associated with a lack of deformation and lack of fluids, either as a catalyst or as a component in hydration reactions. The three bodies appear to have been far less reactive than the external gneisses in this region, even though they followed a similar pressure–temperature evolution. The extent of metastable behaviour has implications for the protolith of the Western Gneiss Region, for the density evolution of high-pressure terranes and hence for the geodynamic evolution of mountain belts.

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

2006 ◽  
Vol 143 (4) ◽  
pp. 431-446 ◽  
Author(s):  
C. SARTINI-RIDEOUT ◽  
J. A. GILOTTI ◽  
W. C. McCLELLAND
Keyword(s):  
Deformation Zone ◽  
Shear Zones ◽  
Amphibolite Facies ◽  
Ultrahigh Pressure ◽  
High Mass ◽  
Weighted Mean ◽  
East Greenland ◽  
North East ◽  
The North ◽  
Land Deformation

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 206Pb/238U 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 206Pb/238U 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.

Multi-stage metamorphism of the South Altyn ultrahigh-pressure metamorphic belt, West China: insights into tectonic evolution from continental subduction to arc–backarc extension

2021 ◽  
Author(s):  
Jie Dong ◽  
Chunjing Wei
Keyword(s):  
Late Stage ◽  
Tectonic Evolution ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Ultrahigh Pressure ◽  
Garnet Amphibolite ◽  
The South ◽  
Metamorphic Belt ◽  
Mineral Assemblages ◽  
Eclogite Facies

Abstract The South Altyn ultrahigh-pressure (UHP) metamorphic belt is claimed to host the deepest subducted continental crust based on the discovery of former stishovite, and thus can provide unique insights into the tectonic evolution from deep continental subduction and exhumation to arc–backarc extension. In this paper, we present detailed studies of petrography, mineral chemistry, phase equilibria modelling and zircon U-Pb dating for three representative samples involving garnet amphibolite (A1531 & A1533) and associated garnet-biotite gneiss (A1534) from the UHP belt. Three phases of metamorphism are inferred for the rocks. The first phase high pressure (HP)–UHP-type eclogite facies is represented by the mineral assemblages of garnet and phengite inclusions in zircon and garnet cores with the high grossular (XGrs = 0.33–0.34). The Si contents of 3.40–3.53 and 3.24–3.25 p.f.u. in phengite inclusions yield pressure conditions of >1.7–2.3 GPa for A1533 and 2.5–2.55 GPa for A1534 at a fixed temperature of 770 °C. The second phase medium-pressure (MP)-type overprinting of garnet amphibolite facies shows P–T conditions of 0.8–1.2 GPa/750–785 °C based on the stability fields of corresponding mineral assemblages, the measured isopleths of Ti contents in biotite and amphibole cores, and XGrs in garnet. The third phase low-pressure (LP) type overprinting includes early-stage heating to peak granulite facies followed by cooling towards a late-stage amphibolite facies. The peak granulite facies is represented by the high Ti amphibole mantle, high Zr titanite and the intergrowths of clinopyroxene + ilmenite in A1533 & A1531, with P–T conditions of 800–875 °C/0.80–0.95 GPa. The late-stage is defined by the solidus assemblages, giving P–T conditions of 0.5–0.7 GPa/720–805 °C. U-Pb geochronology on metamorphic zircons from A1533 and A1534 gives three ages of c. 500 Ma, c. 482 Ma and c. 460 Ma. They are interpreted to represent the HP–UHP, MP and LP types of metamorphism respectively, based on cathodoluminescence images, mineral inclusions and trace element patterns. Combining the regional geology and metamorphic evolution from the Altyn Orogen, a tectonic model is inferred, including the following tectonic scenarios. The small Altyn Microcontinent was subducted to great mantle depths with dragging of the surrounding vast oceanic lithosphere to undergo the HP–UHP eclogite facies metamorphism during the early subduction stage (c. 500 Ma) of the Proto-Tethys Ocean. Then, the subducted slabs were exhumed to a thickened crust region to be overprinted by the MP-type assemblages at c. 482 Ma. Finally, an arc–backarc extension was operated within the thickened crust region due to the retreat of subduction zones. It caused evident heating and the LP-type metamorphic overprinting at c. 460 Ma, with a fairly long interval of 30–40 Myr after the HP–UHP metamorphism, distinct from the short interval of <5–10 Myr in the Bohemian Massif.

Structure and40Ar/39Ar thermochronology of an ultrahigh-pressure transition in western Norway

2011 ◽  
Vol 168 (4) ◽  
pp. 887-898 ◽  
Author(s):  
D.J. Young ◽  
B.R. Hacker ◽  
T.B. Andersen ◽  
P.B. Gans
Keyword(s):  
Ultrahigh Pressure ◽  
Western Norway

Coupled Lu–Hf and Sm–Nd geochronology constrains prograde and exhumation histories of high- and ultrahigh-pressure eclogites from western Norway

2007 ◽  
Vol 242 (1-2) ◽  
pp. 137-154 ◽  
Author(s):  
Andrew R.C. Kylander-Clark ◽  
Bradley R. Hacker ◽  
Clark M. Johnson ◽  
Brian L. Beard ◽  
Nancy J. Mahlen ◽  
...  
Keyword(s):  
Ultrahigh Pressure ◽  
Western Norway

Analysis of Squalene and Its Transformation By-Products in Latent Fingermarks by Ultrahigh-Pressure Liquid Chromatography-High Resolution Accurate Mass Orbitrap™ Mass Spectrometry

2019 ◽  
Author(s):  
Buddhika Dorakumbura ◽  
Francesco Busetti ◽  
Simon Lewis
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
High Resolution ◽  
Storage Conditions ◽  
Ultrahigh Pressure ◽  
Accurate Mass ◽  
Rational Approach ◽  
By Products ◽  
Over Time ◽  
High Resolution Accurate Mass

<p>Transformation of squalene and its by-products in fingermarks over time under different storage conditions (light, dark and underwater) was examined through ultrahigh-pressure liquid chromatography high resolution accurate mass Orbitrap™ mass spectrometry. Complications of assessing fingermark compositional variation over time using multiple samples with varying initial compositions were elucidated and a more rational approach was successfully demonstrated. Squalene was detected in all fresh natural fingermarks and the amount ranged between 0.20 to 11.32 μg/5 fingertips. A notable difference in the transformation of squalene was observed with different storage conditions, where a dark aquatic environment accelerated degradation of squalene compared to dark but dry conditions. Squalene monohydroperoxide was extremely short-lived in natural deposits while the amount of squalene epoxide was still increasing relative to the initial amount, after ageing under dark and aquatic conditions for up to 7 days. Some oxidation by-products of cholesterol were also tentatively identified, which exhibited a growth over time against their initial concentration under any of the storage condition tested. These by-products, therefore, show potential as biomarkers for targeted visualisation of aged deposits.</p>

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