Metamorphic devolatilization of basalts across the greenschist-amphibolite facies transition zone: insights from isograd mapping, petrography and thermodynamic modelling

Lithos ◽  
2019 ◽  
Vol 342-343 ◽  
pp. 295-314 ◽  
Author(s):  
Paul G. Starr ◽  
David R.M. Pattison
Keyword(s):  
Transition Zone ◽  
Thermodynamic Modelling ◽  
Amphibolite Facies ◽  
Facies Transition

scholarly journals The effects of solid and vapour phase compositional variations on the amphibolite facies to granulite facies transition in the Agto metadolerites

1979 ◽  
Vol 89 ◽  
pp. 109-111
Author(s):  
W.E Glassley ◽  
K Sørensen
Keyword(s):  
Granulite Facies ◽  
Vapour Phase ◽  
Amphibolite Facies ◽  
Chemical Analyses ◽  
Bulk Rock ◽  
Entire Sequence ◽  
Garnet Granulite ◽  
Compositional Variations ◽  
Petrographic Study ◽  
Facies Transition

Metadolerites occurring in the vicinity of Agto (within the Isortoq Complex of central West Greenland) have been metamorphosed in upper amphibolite to garnet granulite facies. Detailed sampling and petrographic study of these demonstrates that the entire sequence of assemblages may occur in individual dykes, with the amphibolite assemblages normally restricted to dyke margins, garnet granulite facies rocks occurring in the dyke cores, and pyroxene granulite facies rocks intervening between these two. Bulk rock chemical analyses demonstrate that the dykes are chernically homogeneous with respect to all oxides except Al2O3 and Na2O. Nevertheless, variation in the latter two oxides is small, and demonstrably is not a parameter which significantly controls assemblage development.

scholarly journals Stratigraphy and structural development of the Precambrian rocks in the area north-east of Disko Bugt, West Greenland

1967 ◽  
Vol 13 ◽  
pp. 1-28
Author(s):  
A Escher ◽  
M Burri
Keyword(s):  
Transition Zone ◽  
Greenschist Facies ◽  
Amphibolite Facies ◽  
Structural Development ◽  
West Greenland ◽  
Precambrian Rocks ◽  
The Third ◽  
North East ◽  
Area North

The Precambrian rocks in the area north-east of Disko Bugt can be divided into a lower gneiss group and an upper supracrustal group. The lower part of the supracrustal group consists of quartzites, amphibolites and garnet-staurolite schists, while the upper part is mainly semipelitic schist. The gneisses were affected by three successive phases of deformation, while in the supracrustals only the two latest phases of folding can be recognized. Evidence is given in support of the idea that the supracrustals were deposited on a gneiss basement after the first phase of folding, the basement being later reactivated mainly during the third and last deformation. Two main tectonic compLexes can be distinguished in the area mapped: a southern complex characterized by a predominarit ENE direction of the fold axes and a northern complex in which the main fold axes are strongly curved around a central gneiss dorne. The transition zone between the southern and northern complex is marked by the presence of severaL important faults and mylonites. The gneiss dorne is flanked in its northern part by a thick granite sheet. The dorne structure appears to have been forrned by a combination of diapiric movements and the interference between two successive deformations. The gneisses and lower supracrustals recrystallized under amphibolite facies conditions, while greenschist facies conditions prevaiLed during the recrystallisation of the upper supracrustals.

scholarly journals Some border relations between supracrustal and infracrustal rocks in South-West Greenland

1966 ◽  
Vol 9 ◽  
pp. 1-43
Author(s):  
B.F Windley ◽  
N Henriksen ◽  
A.K Higgins ◽  
E Bondesen ◽  
S.B Jensen
Keyword(s):  
Transition Zone ◽  
Metamorphic Grade ◽  
Greenschist Facies ◽  
Amphibolite Facies ◽  
Granitic Rocks ◽  
Second Phase ◽  
Concomitant Increase ◽  
West Greenland ◽  
South West ◽  
Volcanic Series

Three types of border relation between supracrustal and intracrustal rocks are described from South-West Greenland. In the Ravns Storø area a largely volcanic series, possibly equivalent in age to the Tartoq Group, passes downwards into the underlying gneisses via a transitional migmatite front. The supracrustal bedding passes conformably downwards into the gneissic foliation and there is a progressive downward increase in metamorphic grade and degree of mineral orientation. In the northern part of the Ivigtut region Ketilidian supracrustals lie with a major unconformity on pre-Ketilidian gneisses (and Tartoq Group) supracrustals; between which there is a migmatite front relation. Passing southwards the autochthonous unconformity between the Ketilidian supra­crustals and the underlying rocks is affected by a series of progressive tectonic modifications. Faulting parallel to the axial planes of Ketilidian second phase folds in the supracrustals is followed by thrusting along the unconformity, giving rise to a parautochthonous border, which further south passes into an allochthonous border modified by gneissification and associated with the formation of granitic rocks. Earlier basic dykes together with the gneissic foliation are dragged along the transitional border which simulates a transition zone between a superstructure and an infrastructure. In association with this increase in tectonisation there is a concomitant increase in grade of metamorphism of the supracrustal rocks from an almost unmetamorphosed state through greenschist facies and epidotemphibolite facies to amphibolite facies.

scholarly journals Thermodynamic modelling of carbonate-silicate rocks from the Sakar unit, Sakar-Strandzha zone, SE Bulgaria

2021 ◽  
Vol 82 (3) ◽  
pp. 76-78
Author(s):  
Tzvetomila Vladinova ◽  
Milena Georgieva
Keyword(s):  
Metamorphic Grade ◽  
Thermodynamic Modelling ◽  
Greenschist Facies ◽  
Amphibolite Facies ◽  
General Increase ◽  
Metasedimentary Rocks ◽  
Town Area ◽  
East West ◽  
Silicate Rocks

The P-T evolution of carbonate-bearing metasedimentary rocks from the Sakar unit (Sakar-Strandzha Zone, SE Bulgaria) has been obtained using Perple_X modelling and conventional geothermometry. The metamorphic conditions vary from greenschist facies (250–350 °C/2–4 kbar) in the Klokotnitsa village area to amphibolite facies (550–650 °C/4.5–6.5 kbar) in the Topolovgrad town area, confirming a general increase of the metamorphic grade at east-west direction.

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