scholarly journals Partial melting of metavolcanics in amphibolite facies regional metamorphism

2001 ◽  
Vol 110 (4) ◽  
pp. 287-291
Author(s):  
Alan Bruce Thompson
Keyword(s):  
Partial Melting ◽  
Regional Metamorphism ◽  
Amphibolite Facies

scholarly journals Zircon U–Pb Dating and Lu-Hf Isotope of the Retrograded Eclogite from Chicheng, Northern Hebei Province, China

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xu Kong ◽  
Xueyuan Qi ◽  
Wentian Mi ◽  
Xiaoxin Dong
Keyword(s):  
Regional Metamorphism ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Metamorphic Event ◽  
Isotopic Data ◽  
Metamorphic Condition ◽  
Eu Anomaly ◽  
Facies Metamorphism ◽  
Eclogite Facies ◽  
Plagioclase Gneiss

We report zircon U–Pb ages and Lu-Hf isotopic data from two sample of the retrograded eclogite in the Chicheng area. Two groups of the metamorphic zircons from the Chicheng retrograded eclogite were identified: group one shows characteristics of depletion in LREE and flat in HREE curves and exhibit no significant Eu anomaly, and this may imply that they may form under eclogite facies metamorphic condition; group two is rich in HREE and shows slight negative Eu anomaly indicated that they may form under amphibolite facies metamorphic condition. Zircon Lu-Hf isotopic of εHf from the Chicheng eclogite has larger span range from 6.0 to 18.0, which suggests that the magma of the eclogite protolith may be mixed with partial crustal components. The peak eclogite facies metamorphism of Chicheng eclogite may occur at 348.5–344.2 Ma and its retrograde metamorphism of amphibolite fancies may occur at ca. 325.0 Ma. The Hongqiyingzi Complex may experience multistage metamorphic events mainly including Late Archean (2494–2448 Ma), Late Paleoproterozoic (1900–1734 Ma, peak age = 1824.6 Ma), and Phanerozoic (495–234 Ma, peak age = 323.7 Ma). Thus, the metamorphic event (348.5–325 Ma) of the Chicheng eclogite is in accordance with the Phanerozoic metamorphic event of the Hongqiyingzi Complex. The eclogite facies metamorphic age of the eclogite is in accordance with the metamorphism (granulite facies or amphibolite facies) of its surrounding rocks, which implied that the tectonic subduction and exhumation of the retrograded eclogite may cause the regional metamorphism of garnet biotite plagioclase gneiss.

Rapid fluid-driven transformation of lower continental crust associated with thrust-induced shear heating

2020 ◽  
Author(s):  
Bjørn Jamtveit ◽  
Kristina G. Dunkel ◽  
Arianne Petley-Ragan ◽  
Fernando Corfu ◽  
Dani W. Schmid
Keyword(s):  
Regional Metamorphism ◽  
Shear Zones ◽  
Amphibolite Facies ◽  
Source Rocks ◽  
Granitic Rocks ◽  
Time Interval ◽  
Fluid Infiltration ◽  
Facies Metamorphism ◽  
Shear Heating ◽  
Host Rocks

<p>Caledonian eclogite- and amphibolite-facies metamorphism of initially dry Proterozoic granulites in the Lindås Nappe of the Bergen Arcs, Western Norway, is driven by fluid infiltration along faults and shear zones. The granulites are also cut by numerous dykes and pegmatites that are spatially associated with metamorphosed host rocks. U-Pb geochronology was performed to constrain the age of fluid infiltration and metamorphism. The ages obtained demonstrate that eclogite- and amphibolite-facies metamorphism were synchronous within the uncertainties of our results and occurred within a maximum time interval of 5 Myr, with a mean age of ca. 426 Ma.  Caledonian dykes and pegmatites are granitic rocks characterised by a high Na/K-ration, low REE-abundance and positive anomalies of Eu, Ba, Pb, and Sr. The most REE-poor compositions show HREE-enrichment. Melt compositions are consistent with wet melting of plagioclase- and garnet-bearing source rocks. The most likely fluid source is dehydration of Paleozoic metapelites, located immediately below the Lindås part of the Jotun-Lindås microcontinent, during eastward thrusting over the extended margin of Baltica. Melt compositions and thermal modelling suggest that short-lived fluid-driven metamorphism of the Lindås Nappe granulites was related to shear heating at lithostatic pressures in the range 1.0-1.5 GPa. High-P (≈2 GPa) metamorphism within the Nappe was related to weakening-induced pressure perturbations, not to deep burial. Our results emphasize that both prograde and retrograde metamorphism may proceed rapidly during regional metamorphism and that their time-scales may be coupled through local production and consumption of fluids.</p>

Petrogenesis of spilite and keratophyre from a Permian and Triassic volcanic arc terrane, eastern Oregon and western Idaho, U.S.A.

1978 ◽  
Vol 15 (8) ◽  
pp. 1356-1369 ◽  
Author(s):  
T. L. Vallier ◽  
Rodey Batiza
Keyword(s):  
Mass Balance ◽  
Ion Mobility ◽  
Regional Metamorphism ◽  
Greenschist Facies ◽  
Amphibolite Facies ◽  
Internal Mass ◽  
Volcanic Arc ◽  
Sea Floor ◽  
General Internal ◽  
Low Potassium

Spilite, keratophyre, and quartz keratophyre from a Permian and Triassic volcanic arc assemblage in eastern Oregon and western Idaho originally were low-potassium basalt, andesite, dacite, and possibly rhyolite. Amphibolite from an abyssal sea floor or marginal basin environment of either Permian or Triassic age originally was low-potassium basalt. Present mineralogies are characteristic of the greenschist and amphibolite facies of regional metamorphism. Greenschist facies minerals are mostly albite, epidote, chlorite, calcite, and quartz, whereas amphibolite facies minerals are predominantly hornblende, plagioclase (andesine), and epidote. In the volcanic arc assemblage, mineralogies of the Permian rocks are nearer equilibrium in the greenschist facies than those of the overlying Triassic rocks, probably reflecting deeper burial. Bulk compositions indicate extensive ion mobility, but there has been a general internal mass balance of most components. Na2O, CO2, and H2O were probably added to most rocks, but the source of those components has not been established.

scholarly journals Structural setting and U–Pb zircon geochronology of the Glen Scaddle Metagabbro: evidence for polyphase Scandian ductile deformation in the Caledonides of northern Scotland

2008 ◽  
Vol 145 (3) ◽  
pp. 361-371 ◽  
Author(s):  
R. A. STRACHAN ◽  
J. A. EVANS
Keyword(s):  
Regional Metamorphism ◽  
Amphibolite Facies ◽  
Ductile Deformation ◽  
Zircon Geochronology ◽  
Zircon Age ◽  
Structural Setting ◽  
Facies Metamorphism

AbstractWithin the Scottish Caledonides, the Glen Scaddle Metagabbro was intruded into the Moine Supergroup of the Northern Highland Terrane after Grampian D2 folding and prior to regional D3 and D4 upright folding and amphibolite-facies metamorphism. A U–Pb zircon age of 426 ± 3 Ma obtained from the metagabbro is interpreted to date emplacement. D3–D4 folding is constrained to have occurred during the Scandian orogenic event. In contrast, polyphase folding and regional metamorphism of the Dalradian Supergroup southeast of the Great Glen Fault is entirely Grampian. These differences are consistent with published tectonic models that invoke a minimum of 700 km of post-Scandian sinistral displacements across the Great Glen Fault to juxtapose the Grampian and Northern Highland terranes.

scholarly journals Neoproterozoic pegmatite from Skoddefjellet, Wedel Jarlsberg Land, Spitsbergen: Additional evidence for c. 640 Ma tectonothermal event in the Caledonides of Svalbard

2012 ◽  
Vol 33 (1) ◽  
pp. 1-17 ◽  
Author(s):  
Jarosław Majka ◽  
Alexander Larionov ◽  
David Gee ◽  
Jerzy Czerny ◽  
Jaroslav Pršek
Keyword(s):  
Electron Microprobe ◽  
Regional Metamorphism ◽  
Amphibolite Facies ◽  
The Other ◽  
Clear Distinction ◽  
Metasedimentary Rocks ◽  
Facies Metamorphism ◽  
Shrimp Zircon ◽  
Tectonothermal Event

Neoproterozoic pegmatite from Skoddefjellet, Wedel Jarlsberg Land, Spitsbergen: Additional evidence forc. 640 Ma tectonothermal event in the Caledonides of SvalbardNeoproterozoic (c. 640 Ma) amphibolite facies metamorphism and deformation have been shown recently to have affected the Isbjørnhamna and Eimfjellet Complex of Wedel Jarlsberg Land in southwestern Spitsbergen. New SHRIMP zircon U-Pb andin situelectron microprobe monazite and uraninite U-Th-total Pb ages are presented here on a pegmatite occurring within the Isbjørnhamna metasedimentary rocks. Although the dated zircons are full of inclusions, have high-U contents and are metamict and hence have experienced notable Pb-loss, the new Cryogenian ages are consistent with the age of regional metamorphism of the host metasediments, providing additional evidence for a clear distinction of the Southwestern Province from the other parts of the Svalbard Caledonides.

The texture and composition of tourmaline in metasediments of the Sinai, Egypt: Implications for the tectono-metamorphic evolution of the Pan-African basement

2007 ◽  
Vol 71 (1) ◽  
pp. 17-40 ◽  
Author(s):  
M. M. Abu El-Enen ◽  
M. Okrusch
Keyword(s):  
Regional Metamorphism ◽  
Metamorphic Grade ◽  
Crystalline Basement ◽  
Amphibolite Facies ◽  
Metamorphic Rocks ◽  
Pan African ◽  
Chemical Signatures ◽  
Mineral Assemblages ◽  
The Matrix ◽  
Metamorphic Facies

AbstractAccessory tourmaline in metasediments from the Sinai crystalline basement exhibits textural and chemical signatures that relate to the evolution of regional metamorphism and deformation during the Pan-African orogeny and testifies to different P-T path segments. Tourmaline inclusions in various porphyroblasts were formed during the prograde phase of metamorphism; acicular to prismatic crystals in the matrix, oriented sub-parallel to, and enveloped by, the main foliation crystallized syntectonically under prograde and peak metamorphic conditions; tourmaline cross-cutting the main foliation may have formed just after the peak or during the retrograde phase of metamorphism. Some of the cores in tourmaline crystals, showing different colours, are interpreted as former detrital grains. The abundance of tourmaline decreases with increasing peak metamorphic conditions. The tourmaline investigated belongs to the schorl-dravitess group, generally with XMg of 0.42–0.73 and XCa = Ca/(Ca+Na+K+□) of 0.02–0.24, typical of tourmalines in metapelites and metapsammites; whereas detrital cores have been derived from various sources, including former tourmaline-quartz and pre-existing high-metamorphic rocks. Tourmaline of the Sinai metasediments was formed during metamorphism of the sedimentary precursors, essentially in a closed system, where clay minerals and organic matter, together with detrital tourmaline, served as the source of boron. Although a metamorphic facies should be defined by characteristic mineral assemblages present in metamorphic rocks, tourmaline chemistry is a good monitor of P-T conditions in the metapelites and semi-metapelites investigated, showing an increase in XMg with increasing metamorphic grade, where XturMg = 0.60 distinguishes between greenschist and lower-amphibolite facies, while XturMg = 0.65 could distinguish lower- from middle- to upper-amphibolite facies. The results of tourmaline-biotite geothermometry compare well with our former temperature estimates using conventional geothermometry and phase-diagram modelling.

METAMORPHISM OF THE MEGUMA GROUP OF NOVA SCOTIA

1966 ◽  
Vol 3 (7) ◽  
pp. 959-974 ◽  
Author(s):  
F. C. Taylor ◽  
E. A. Schiller
Keyword(s):  
Nova Scotia ◽  
Regional Metamorphism ◽  
Greenschist Facies ◽  
Amphibolite Facies ◽  
Contact Metamorphism ◽  
Granitic Rocks ◽  
Structural Elements ◽  
Early Ordovician ◽  
Quartz Veins ◽  
Granite Emplacement

The Meguma group of lithic greywacke, feldspathic quartzite, slate siltstone, and argillite is Early Ordovician or older in age and has undergone both regional and contact metamorphism. Both types of metamorphism have resulted in recrystallization and locally in orientation of newly formed minerals. Metasomatism and retrogressive metamorphism are subordinate and only locally important. Regionally metamorphosed rocks are divided into greenschist and almandine–amphibolite facies, although some assemblages cannot be assigned with certainty. Locally, biotite and garnet isograds are mappable within the greenschist zone.Relationships between regional metamorphism and structural elements (folding) show that deformation preceded regional metamorphism. Intrusion of granitic rocks has produced a zone of contact metamorphism (hornblende–hornfels facies) that is superimposed upon regional greenschist facies rocks, which shows that granite emplacement occurred after the regional grade was reached. Gold–quartz veins are confined to areas lying in the greenschist zone of regional metamorphism, which suggests that the almandine–amphibolite zone is not favorable.

From granulite hydration to metamorphic differentiation: Evolution of a shear zone.

2020 ◽  
Author(s):  
Andrew Putnis ◽  
Jo Moore ◽  
Andreas Beinlich ◽  
Sandra Piazolo ◽  
Håkon Austrheim
Keyword(s):  
Mass Transfer ◽  
Partial Melting ◽  
Shear Zone ◽  
Strain Distribution ◽  
Amphibolite Facies ◽  
Fluid Flux ◽  
Transfer Processes ◽  
Fluid Infiltration ◽  
Mass Transfer Processes ◽  
Local Dissolution

<p><span>The studied outcrop, located within the Bergen arcs of southwestern Norway, preserves the hydration of an anorthositic granulite at amphibolite-facies conditions. The amphibolite-facies hydration is expressed as both a statically hydrated amphibolite and a shear zone rock, defined by the interlayering of amphibolite with leucocratic domains. Within the outcrop, quartz-filled fractures and their associated amphibolite alteration haloes crosscut the granulite. These fractures are relicts of the initial fluid infiltration event. The fracture assemblage (quartz + plagioclase + zoisite + kyanite ± muscovite ± biotite) is equivalent to that occurring locally within leucocratic domains of the shear zone. Due to the textural and compositional similarities between quartz-filled fractures and leucocratic domains, the compositional layering of the shear zone rock may be directly linked to fracturing during initial fluid infiltration. Mass-balance calculations indicate quartz-filled fractures and compositional differentiation of the shear zone form by internal fractionation rather than partial melting or precipitation of minerals from an eternally derived fluid. This inferred fluid connectivity combined with the enhanced local dissolution indicates the presence of a continuously replenished fluid along fracture pathways. The overall conclusion is that the mass transfer processes that result in metamorphic differentiation of the shear zone lithologies are dependent on both continuous fluid flux and heterogeneous strain distribution. </span></p>

scholarly journals Petrogenesis, U-Pb and Sm-Nd geochronology of the Furna Azul Migmatite: partial melting evidence during the San Ignácio Orogeny, Paraguá Terrane, SW Amazon Craton

2016 ◽  
Vol 46 (2) ◽  
pp. 239-259
Author(s):  
Newton Diego Couto do Nascimento ◽  
Amarildo Salina Ruiz ◽  
Ronaldo Pierosan ◽  
Gabrielle Aparecida de Lima ◽  
João Batista Matos ◽  
...  
Keyword(s):  
Partial Melting ◽  
Amphibolite Facies ◽  
Mato Grosso ◽  
Intrusive Suite

ABSTRACT: The Furna Azul Migmatite is a ~10 km2 complex located in Pontes e Lacerda city, Mato Grosso, Brazil. It belongs to Paraguá Terrane, limit with Rio Alegre Terrane, southeast of San Ignacio Province, in Amazon Craton. It consists of transitional metatexites with amphibolite enclaves and dioritic injections. The rocks were divided in residuum rich and leucosome rich; both have three deformation phases marked by folded stromatic layers affected by spaced foliation and metamorphosed in amphibolite facies, represented by garnet, biotite, sillimanite, and by the clinopyroxene in the enclaves. The metamorphic retrograde to greenschist is marked by formation of chlorite, muscovite and prehnite. Residuum-rich metatexites show higher CaO and Na2O contents, separating them from K2O, Ba and Rb enriched transitional metatexites. U-Pb on zircon and Sm-Nd whole-rocks dating indicates that the residuum-rich metatexite crystallized at 1436 ± 11 Ma, with a TDM age of 1.90 Ga and εNd(1.43) of -0.54, whereas the dioritic injection crystallized at 1341,7 ± 17 Ma with a TDM age of 1.47 Ga and εNd(1.34) of 3.39. These results indicate that the Furna Azul Migmatite protolith was formed during the San Ignácio Orogeny and was reworked during the same orogeny, as basement for collisional to post-magmatic granites from Pensamiento Intrusive Suite.

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