Amphibolite and blueschist-greenschist facies metamorphism, Blue Mountain inlier, eastern Jamaica

2008 ◽  
Vol 43 (5) ◽  
pp. 525-541 ◽  
Author(s):  
Richard N. Abbott ◽  
Betsy R. Bandy
Keyword(s):  
Greenschist Facies ◽  
Blue Mountain ◽  
Facies Metamorphism ◽  
Greenschist Facies Metamorphism

scholarly journals The tectono-metamorphic evolution of a dismembered ophiolite (Tinos, Cyclades, Greece)

1996 ◽  
Vol 133 (3) ◽  
pp. 237-254 ◽  
Author(s):  
Yaron Katzir ◽  
Alan Matthews ◽  
Zvi Garfunkel ◽  
Manfred Schliestedt ◽  
Dov Avigad
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Subduction Zone ◽  
Sea Water ◽  
Regional Metamorphism ◽  
Greenschist Facies ◽  
Normal Faults ◽  
Model Calculations ◽  
Facies Metamorphism ◽  
Greenschist Facies Metamorphism

AbstractThe six exposures of the Upper tectonic Unit of the Cycladic Massif occurring on the island of Tinos are shown to comprise a metamorphosed dismembered ophiolite complex. The common stratigraphic section consisting of tens-of-metres- thick tectonic slices of mafic phyllites overlain by serpentinites and gabbros is considered to have been derived by a combination of thrusting during obduction and subsequent attenuation by low-angle normal faults. All rock types show evidence of a phase of regional greenschist-facies metamorphism, which in the case of the phyllites is accompanied by penetrative deformation. The greenschist-facies metamorphism in gabbros is preceded by high temperature sea-floor amphibolite-facies alteration, whereas in the serpentinites, the antigorite + forsterite greenschist-facies assemblage overprinted an earlier low temperature lizardite serpentinite. Trace element patterns of the mafic phyllites and a harzburgitic origin of meta-serpentinites suggest a supra subduction zone (SSZ) affinity for the ophiolitic suite. ρ18O values of phyllites, gabbros and serpentinites range from 6 to 15%o. Model calculations indicate that such values are consistent with low temperature (50–200°C) alteration of parent rocks by sea-water at varying water/rock ratios. This would agree with the early low temperature mineralogy of the serpentinites, but the early high temperature alteration of the gabbros would require the presence of 18O-enriched sea-water.The following overall history is suggested for Tinos ophiolitic slices. (1) Oceanic crust was generated at a supra-subduction zone spreading centre with high temperature alteration of gabbros. (2) Tectonic disturbance (its early hot stages recorded in an amphibolitic shear zone at the base of serpentinites) brought the already cooled ultramafics into direct contact with sea-water and caused low-T serpentinization. (3) Tectonism after cooling involved thrusting which caused repetition and inversion of the original order of the oceanic suite. (4) Regional metamorphism of all the ophiolite components at greenschist-facies conditions (−450°C) overprinted the early alteration mineralogy. It was probably induced by continued thrusting and piling up of nappes. The Tinos ophiolite, dated as late Cretaceous and genetically related to other low pressure rock-units of the same age in the Aegean, differs in age and degree of dismemberment and metamorphism from ophiolites in mainland Greece.

scholarly journals Thermochronological evidence for late Proterozoic (Vendian) cooling in southwest Wedel Jarlsberg Land, Spitsbergen

1998 ◽  
Vol 135 (1) ◽  
pp. 63-69 ◽  
Author(s):  
M. MANECKI ◽  
D. K. HOLM ◽  
J. CZERNY ◽  
D. LUX
Keyword(s):  
Geological Mapping ◽  
Greenschist Facies ◽  
Amphibolite Facies ◽  
Variable Intensity ◽  
Late Proterozoic ◽  
Facies Metamorphism ◽  
History Of ◽  
Greenschist Facies Metamorphism

Two Proterozoic terranes with different metamorphic histories are distinguished from geological mapping in southwestern Wedel Jarlsberg Land: a northern greenschist facies terrane and a southern amphibolite facies terrane which has been overprinted by greenschist facies metamorphism. To better characterize the tectonothermal history of these terranes we have obtained new 40Ar/39Ar mineral dates from this area. A muscovite separate from the northern terrane yielded a Caledonian plateau age of 432±7 Ma. The southern terrane yielded significantly older 40Ar/39Ar ages with three muscovite plateau dates of 584±14 Ma, 575±15 Ma, and 459±9 Ma, a 484±5 Ma biotite plateau date, and a 616±17 Ma hornblende plateau date. The oldest thermochronological dates are over 300 Ma younger than the age of amphibolite facies metamorphism and therefore probably do not represent uplift-related cooling. Instead, the Vendian dates correlate well with a regionally widespread magmatic and metamorphic/thermal resetting event recognized within Caledonian complexes of northwestern Spitsbergen and Nordaustlandet. The apparent Ordovician dates are interpreted to represent partial resetting, suggesting that late Caledonian greenschist facies overprinting of the southern terrane was of variable intensity.

Crossitic amphibole and its possible tectonic significance in the Richmond Area, southeastern Quebec

1976 ◽  
Vol 13 (5) ◽  
pp. 711-714 ◽  
Author(s):  
W. E. Trzcienski Jr.
Keyword(s):  
Subduction Zone ◽  
Geophysical Data ◽  
Greenschist Facies ◽  
The South ◽  
Tectonic Significance ◽  
Facies Metamorphism ◽  
Greenschist Facies Metamorphism

Crossitic amphibole suggesting blueschist-type metamorphism has been found in the Richmond area, southeastern Quebec. Prehnite facies metamorphism to the northeast of Richmond and greenschist facies metamorphism to the south along with the blueschist-type metamorphism and geophysical data suggest that the Richmond area may represent a partially eroded Ordovician subduction zone.

A transition from diagenesis to greenschist facies within a major Variscan fold/thrust complex in SW England

1985 ◽  
Vol 49 (352) ◽  
pp. 365-374 ◽  
Author(s):  
T. J. Primmer
Keyword(s):  
Greenschist Facies ◽  
North Coast ◽  
Illite Crystallinity ◽  
Continuous Section ◽  
The North ◽  
Mineral Assemblages ◽  
Facies Metamorphism ◽  
O Isotope ◽  
Greenschist Facies Metamorphism ◽  
Pelitic Rocks

AbstractThe north coast of Cornwall, from Bude to Newquay, provides a continuous section through a major Variscan fold/thrust complex. Illite crystallinity studies have revealed a transition from diagenesis in the north to greenschist facies metamorphism in the south in the Upper Palaeozoic succession. More detailed studies of mineral assemblages in both metabasites and pelitic rocks support the regional pattern of metamorphism indicated by illite crystallinity, and show that locally in the Tintagel district, the grade of metamorphism may have reached middle to upper greenschist facies. An attempt to correlate the above data with temperatures (108–985°C) derived from O-isotope geothermometers is made. Interpretation of the metamorphic data presented helps to emphasize the tectonic importance of the major structures seen in the fold/thrust complex.

Subcalcic, Fe-rich amphiboles in meta-dolerites, Glenrock Station, NSW, Australia

1984 ◽  
Vol 48 (346) ◽  
pp. 47-52 ◽  
Author(s):  
R. Offler
Keyword(s):  
Fluid Phase ◽  
Greenschist Facies ◽  
Fe Content ◽  
Facies Metamorphism ◽  
Greenschist Facies Metamorphism

AbstractSub-greenschist facies metamorphism has produced unusual subcalcic, Fe-rich actinolitic amphiboles in meta-dolerites from the Glenrock Station area, NSW. They show edenite, riebeckite, ferri-tschermakite and Ti-tschermakite coupled substitutions. Their high Fe content is attributed to high aFe2+ and aFe3+ in the fluid phase produced during the breakdown of clinopyroxene, hornblende, magnetite, and ilmenite. The high aFe2+ led to Fe led to Fe2- occupying the B site, resulting in the formation of subcalcic amphiboles. Variation in aFe2+, aFe3+, aMg, aSi, aAl, and aCa, in different domains resulted in the crystallization of chemically inhomogeneous amphiboles.

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