scholarly journals Amphibolite facies metamorphic event within the Upper Sebtides tectonic units (Internal Rif, Morocco): a record of a hyperextended margin at the border of the western Tethys

2021 ◽  
Vol 353 (1) ◽  
pp. 193-208
Author(s):  
Asmae El Bakili ◽  
Michel Corsini ◽  
Jean-Marc Lardeaux ◽  
Sylvain Gallet ◽  
Philippe Münch ◽  
...  
Keyword(s):  
Amphibolite Facies ◽  
Metamorphic Event ◽  
Western Tethys

scholarly journals Structural and geochronological constraints on the evolution of the Juréia Massif, Registro Domain, State of São Paulo, Brazil

2007 ◽  
Vol 79 (3) ◽  
pp. 441-455 ◽  
Author(s):  
Cláudia R. Passarelli ◽  
Miguel A.S. Basei ◽  
Hélcio J. Prazeres-Filho ◽  
Oswaldo Siga-Jr. ◽  
Gergely A.J. Szabó ◽  
...  
Keyword(s):  
Shear Zone ◽  
Sao Paulo ◽  
Amphibolite Facies ◽  
Metamorphic Event ◽  
São Paulo ◽  
Paulo State ◽  
The North ◽  
Domain State ◽  
Geochronological Constraints ◽  
Shear System

The Juréia Massif, southeastern São Paulo State (Brazil), is part of the Registro Domain, limited to the north by the Cubatão-Itariri Shear System and to the south by the Serrinha Shear Zone. Mostly composed of migmatitic granitegneiss rocks, represents a Paleoproterozoic terrane (1.9-2.2 Ga) strongly deformed during the Neoproterozoic (750-580 Ma). The present tectonic scenario was established at the end of the Neoproterozoic, as a result of collages associated with the formation of Western Gondwana. The Ponta da Juréia, our study area within the Juréia Massif, is constituted by paragneisses (garnet-muscovite-biotite gneisses). The monazite U-Pb age of 750 Ma is related to a main regional metamorphic event that reached the high amphibolite facies, recorded in rocks from the Itatins Complex and Cachoeira Sequence as well, which also belongs to the Registro Domain. The paragneissic rocks of this study are affected by the E-W-trending Serrinha Shear Zone, registering a predominantly dextral movement. Biotite K-Ar ages of 482 ± 12 Ma may represent later movements and reflect the younger ages of reactivation of the major lineaments and juxtaposition of the tectonic blocks involved.

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.

Eclogitic amphibolites from the Grampian Moines

1986 ◽  
Vol 50 (356) ◽  
pp. 217-221 ◽  
Author(s):  
A. J. Baker
Keyword(s):  
High Pressure ◽  
Amphibolite Facies ◽  
Metamorphic Event ◽  
Partial Reaction

AbstractAmphibolites from the Grampian Moines of Scotland contain clinopyroxene-plagioclase symplectites and plagioclase-hornblende coronas around garnet. The clinopyroxene-plagioclase symplectites are interpreted as former omphacites. It is inferred that an eclogitic garne-tomphacite-quartz assemblage once existed, but has since undergone partial reaction to an amphibolite facies hornblende-plagioclase assemblage. An early high-pressure metamorphic event occurred in parts of the Moine.

Metamorphism of the Thompson nickel belt gneisses: Paint Lake, Manitoba

1981 ◽  
Vol 18 (2) ◽  
pp. 191-209 ◽  
Author(s):  
J. K. Russell
Keyword(s):  
Mineral Assemblage ◽  
Total Pressure ◽  
Controlling Factor ◽  
Amphibolite Facies ◽  
Metamorphic Event ◽  
Mineral Phase ◽  
Mineral Assemblages ◽  
Temperature And Pressure ◽  
Granulite Terrain ◽  
Detailed Work

Gneisses mapped in the Thompson nickel belt are the product of a Hudsonian metamorphic (M3) overprinting of an Archean granulite terrain. Pikwitonei region granulites may be partially preserved in amphibolite facies migmatite gneisses of the Thompson nickel belt. Temperatures attending the earlier Archean (M2) metamorphic event have been estimated to be 910 ± 70 °C. More detailed work on the younger overprinting suggests that the metamorphic conditions were relatively constant during the M3 metamorphism. Estimated temperature and pressure during the Hudsonian metamorphism are 650 ± 50 °C and 4–5 kbar (4–5 × 105 kPa), respectively.Although total pressure may have been constant, calculated values for [Formula: see text] during the retrograde overprinting indicate a variability due to lithologic control. This variability in [Formula: see text] is shown to be a controlling factor in the development of hydrous retrograde mineral assemblages. Metapelitic gneisses are characterized by [Formula: see text] values of 0.05Ptotal, which may explain the absence of muscovite as a stable M3 mineral phase. Enderbitic gneisses exhibit higher values of [Formula: see text] (0.25Ptotal) due to the emplacement of syn-M3 pegmatite dykes producing a more hydrous stable M3 mineral assemblage.

scholarly journals Structural and Compositional Evolution of Cr-Spinels and Hornblends, Palma Group, Rio Grande do Sul, Brasil

2000 ◽  
Vol 27 (1) ◽  
pp. 15 ◽  
Author(s):  
LÉO AFRANEO HARTMANN ◽  
MARCOS ANTONIO VASCONCELLOS ◽  
MARIA DE FÁTIMA BITTENCOURT ◽  
JOÃO CASTRO ◽  
JULIANA FABIÃO ◽  
...  
Keyword(s):  
Direct Contact ◽  
Rio Grande ◽  
Shear Zones ◽  
Greenschist Facies ◽  
Amphibolite Facies ◽  
Metamorphic Event ◽  
Rio Grande Do Sul ◽  
Compositional Evolution ◽  
Granite Intrusion

One amphibolite facies metamorphic event is registered in chromites and hornblendes from the Palma Group serpentinites and meta-andesites, Brazil's southernmost Rio Grande do Sui Slate. Metamorphism was apparently caused by syntectonic injection of voluminous Cambaí Group meta-granitoids and not by post-tectonic Jaguari Granite intrusion. Regional metamorphic hornblendes are in direct contact with magmatic pargasites, which indicates that it was the first metamorphic event in the area. Both hornblendes in Campestre Formation and Crspinels in Cerro da Cruz Formation are little zoned, an indication that only one metamorphic event was of regional extent. Recrystallization to chlorite + epidote greenschist facies parageneses is restricted to shear zones and volumetrically small.

scholarly journals Evolution and emplacement of Archaean terranes in the Kapisigdlit area, southern West Greenland

1988 ◽  
Vol 140 ◽  
pp. 59-64
Author(s):  
C.R.L Friend ◽  
A.P Nutman
Keyword(s):  
Amphibolite Facies ◽  
Ductile Deformation ◽  
Metamorphic Event ◽  
Crustal Evolution ◽  
Crustal Accretion ◽  
West Greenland ◽  
Differentiation Event

In the Godthåbsfjord region, early Archaean Arnitsoq gneisses are found in association with the middle Archaean Nûk gneisses (McGregor, 1973). Early models of crustal evolution in the Godthåbsfjord region suggested that the Amitsoq gneisses were reworked in a major crustal accretion-differentiation event, which was marked by the injection of the voluminous Nûk gneisses (e.g. Bridgwater et al., 1974; McGregor, 1979; Moor- - bath et al., 1986). This event ,has been interpreted as having culminated in a granulite-amphibolite facies metamorphic event at c. 2800 Ma, which outlasted all significant ductile deformation (e.g. Wells, 1979; Coe, 1980).

Quantitative petrography of mafic dikes from the central Bighorn Mountains, Wyoming

1974 ◽  
Vol 111 (2) ◽  
pp. 97-106 ◽  
Author(s):  
R. A. Heimlich ◽  
G. L. Gallagher ◽  
L. B. Shotwell
Keyword(s):  
Country Rock ◽  
Amphibolite Facies ◽  
Granitic Rocks ◽  
Chemical Data ◽  
Metamorphic Event ◽  
Complete Replacement ◽  
Textural Changes ◽  
Quantitative Petrography ◽  
Partial Destruction ◽  
Bighorn Mountains

SummaryTwo groups of mafic dikes occur within a terrain of metasomatic granitic rocks and quartzofeldspathic gneiss in the central Bighorn Mountains of Wyoming. The younger group consists of dolerite dikes which possess ophitic, subophitic, hypidio morphic-granular and microporphyritic textures. Mineralogically, the dolerites consist primarily of plagioclase (average An 54), augite (average Ca: Mg: Fe = 41: 43: 16) and uralite. The older dikes are metadolerites which possess granoblastic margins that grade into interiors characterized by relict subophitic and locally, porphyriti texture. Dike margins consist of fresh plagioclase and hornblende primarily. Interiors are principally clouded plagioclase (average An 46), augite (average Ca: Mg: Fe = 39: 54: 7) and uralite and/or hornblende. Textural, mineralogic and chemical data indicate that the meta-dolerites were derived from an earlier generation of mafic dikes comparable to the unmeta-morphosed dolerites in the area. The dikes were metamorphosed under low amphibolite facies conditions during the last regional metamorphic event which affected the country rock. During their metamorphism, minimal amounts of water from the country rock facilitated the total recrystallization of the metadolerite margins and the complete or nearly complete replacement of pyroxene by hornblende in the margins. In general, dike interiors underwent no textural changes other than partial destruction of the original subophitic plagioclase–pyroxene relationship as the pyroxene was replaced peripherally by hornblende. This process was accompanied by diffusion of calcium from the plagioclase to form the hornblende, and by diffusion of iron from the augite to cause the clouding of adjacent plagioclase.

scholarly journals Monazite Breakdown in Metapelites From Wedel Jarlsberg Land, Svalbard — Preliminary Report

Mineralogia ◽  
2006 ◽  
Vol 37 (1) ◽  
pp. 61-69 ◽  
Author(s):  
Jarostaw Majka ◽  
Bartosz Budzyń
Keyword(s):  
Low Temperature ◽  
Preliminary Report ◽  
Greenschist Facies ◽  
Amphibolite Facies ◽  
Metamorphic Event

Monazite Breakdown in Metapelites From Wedel Jarlsberg Land, Svalbard — Preliminary ReportMetapelites from the SW part of Wedel Jarlsberg Land were progressively metamorphosed under amphibolite facies conditions followed by a Caledonian low-temperature metamorphic event under greenschist facies conditions. The latter resulted in various stages of monazite breakdown. These include monazite alterations and the formation of allanite-apatite coronas.

scholarly journals Mid amphibolite facies metamorphism of harzburgites in the Neoproterozoic Cerro Mantiqueiras Ophiolite, southernmost Brazil

2003 ◽  
Vol 75 (1) ◽  
pp. 109-128 ◽  
Author(s):  
LÉO A. HARTMANN ◽  
FARID CHEMALE-JÚNIOR
Keyword(s):  
Mineral Assemblage ◽  
Shear Zones ◽  
Amphibolite Facies ◽  
Ductile Deformation ◽  
Metamorphic Event ◽  
Mineral Equilibria ◽  
Facies Metamorphism ◽  
Geological Evolution ◽  
Mineral Compositions

Valuable information is retrieved from the integrated investigation of the field relationships, microstructure and mineral compositions of harzburgites from the Neoproterozoic Cerro Mantiqueiras Ophiolite. This important tectonic marker of the geological evolution of southernmost Brazilian Shield was thoroughly serpentinized during progressive metamorphism, because the oldest mineral assemblage is: olivine + orthopyroxene + tremolite + chlorite + chromite. This M1 was stabilized in mid amphibolite facies - 550-600ºC as calculated from mineral equilibria. No microstructural (e.g. ductile deformation of olivine or chromite) or compositional (e.g. mantle spinel) remnant of mantle history was identified. A metamorphic event M2 occurred in the low amphibolite facies along 100 m-wide shear zones, followed by intense serpentinization (M3) and narrow 1-3 m-wide shear zones (M4) containing asbestos.

The occurrence of högbomite and taaffeite in a spinel-phlogopite schist from the Mount Painter Province of South Australia

1980 ◽  
Vol 43 (329) ◽  
pp. 575-577 ◽  
Author(s):  
Graham S. Teale
Keyword(s):  
South Australia ◽  
Amphibolite Facies ◽  
Metamorphic Event ◽  
Chemical Analyses ◽  
Facies Metamorphism

SummaryA spinel-phlogopite schist from the Mount Painter Province of South Australia forms part of a highly magnesium- and aluminium-rich unit and contains the minerals högbomite and taaffeite. Taaffeite nucleated in spinel during upper amphibolite facies metamorphism. During a subsequent upper amphibolite facies metamorphic event both spinel and taaffeite were partially replaced by högbomite. Chemical analyses of högbomite, taaffeite, and spinel are presented.

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