U–Pb zircon and monazite ages from the Kapuskasing uplift: age constraints on deformation within the Ivanhoe Lake fault zone

1994 ◽  
Vol 31 (7) ◽  
pp. 1096-1103 ◽  
Author(s):  
T. E. Krogh ◽  
D. E. Moser
Keyword(s):  
Fault Zone ◽  
Granulite Facies ◽  
Ductile Deformation ◽  
Metamorphic Rocks ◽  
High Grade ◽  
Granulite Metamorphism ◽  
Superior Craton ◽  
Age Constraints

A decade of U–Pb dating of zircon and monazite from high-grade metamorphic rocks in the Kapuskasing uplift has identified a series of magmatic and metamorphic events between 2700 and 2585 Ma, and indicates that the onset of regional granulite metamorphism took place at mid-crustal levels of the southern Superior craton ca. 2660 Ma. New U–Pb ages for zircon and monazite have been used to constrain the age of ductile deformation fabrics at two sites in the Ivanhoe Lake fault zone, the structure along which the granulite-facies Kapuskasing structural zone was uplifted. These results suggest that the fault zone was probably active in the late Archean (as young as 2630 Ma) and again at approximately 2500 Ma.

Zircon ages and the distribution of Archaean and Proterozoic rocks in the Rauer Islands

1993 ◽  
Vol 5 (2) ◽  
pp. 193-206 ◽  
Author(s):  
P. D. Kinny ◽  
L. P. Black ◽  
J. W. Sheraton
Keyword(s):  
Granulite Facies ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
High Grade ◽  
Ion Microprobe ◽  
Rock Interaction ◽  
Mafic Rocks ◽  
Grade Fluid ◽  
Vestfold Hills ◽  
Intrusive Suite

The application of zircon U-Pb geochronology using the SHRIMP ion microprobe to the Precambrian high-grade metamorphic rocks of the Rauer Islands on the Prydz Bay coast of East Antarctica, has resulted in major revisions to the interpreted geological history. Large tracts of granitic orthogneisses, previously considered to be mostly Proterozoic in age, are shown here to be Archaean, with crystallization ages of 3270 Ma and 2800 Ma. These rocks and associated granulite-facies mafic rocks and paragneisses account for up to 50% of exposures in the Rauer Islands. Unlike the 2500 Ma rocks in the nearby Vestfold Hills which were cratonized soon after formation, the Rauer Islands rocks were reworked at about 1000 Ma under granulite to amphibolite facies conditions, and mixed with newly generated felsic crust. Dating of components of this felsic intrusive suite indicates that this Proterozoic reworking was accomplished in about 30–40 million years. Low-grade retrogression at 500 Ma was accompanied by brittle shearing, pegmatite injection, partial resetting of U-Pb geochronometers and growth of new zircons. Minor underformed lamprophyre dykes intruded Hop and nearby islands later in the Phanerozoic. Thus, the geology of the Rauer Islands reflects reworking and juxtaposition of unrelated rocks in a Proterozoic orogenic belt, and illustrates the important influence of relatively low-grade fluid-rock interaction on zircon U-Pb systematics in high-grade terranes.

Zircon geochronology of anatectic melts and residues from a highgrade pelitic assemblage at Ihosy, southern Madagascar: evidence for Pan-African granulite metamorphism

1996 ◽  
Vol 133 (3) ◽  
pp. 311-323 ◽  
Author(s):  
A. Kröner ◽  
I. Braun ◽  
P. Jaeckel
Keyword(s):  
Source Region ◽  
Granulite Facies ◽  
Detrital Zircons ◽  
High Grade ◽  
Left Behind ◽  
Granulite Metamorphism ◽  
Mozambique Belt ◽  
High Grade Metamorphism ◽  
Depositional Age ◽  
Heterogeneous Source

AbstractWe report U—Pb and207Pb/206Pb zircon ages for a granulite facies gneiss assemblage exposed in a large quarry at Ihosy, southern Madagascar. The granulites are derived from pelitic to arkosic sediments and attained equilibrium conditions at 650–700°C and 4–5 kbar. HigherP—Tconditions of 750–800°C and 6 kbar in the presence of low water activities have led to dehydration melting processes. The formation of granitic melts, which (partly) moved away from their source region, intruded into upper parts of the metapelitic gneisses as small granitic veins and left behind granulitic garnet-cordierite-quartz bearing rocks. Detrital zircons in a sample of metapelite and a sample of quartzofeldspathic gneiss yielded ages between ˜720 and ˜1855 Ma, suggesting a chronologically heterogeneous source region and a depositional age of less than ˜720 Ma for these rocks. High-grade metamorphism and anatexis are documented by zircon ages between 526 ±34 and 557 ±2 Ma with a mean age of about 550 Ma. The broad lithologies, metamorphic grades and ages recorded in the Ihosy rocks are similar to those in the Wanni Complex of northwestern Sri Lanka and in high-grade assemblages of southernmost India and support the contention that all these terrains were part of the Mozambique belt which formed as a result of collision of East and West Gondwana in latest Precambrian time.

scholarly journals Polyphase Deformation of the High-Grade Metamorphic Rocks along the Neusspruit Shear Zone in the Kakamas Domain: Insights into the Processes during the Namaquan Orogeny at the Eastern Margin of the Namaqua Metamorphic Province, South Africa

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 759
Author(s):  
Cyrille Stephane Tsakou Sonwa ◽  
Jan van Bever Donker ◽  
Russell Bailie
Keyword(s):  
Shear Zone ◽  
Granulite Facies ◽  
Ductile Deformation ◽  
Structural Development ◽  
Shear Direction ◽  
High Grade ◽  
Deformation Event ◽  
Intense Deformation ◽  
Western Regional ◽  
Regional Boundary

The central part of the Namaqua Metamorphic Province was subjected to intense deformation under high-grade metamorphic conditions up to granulite facies, but also shows greenschist facies overprints denoting the metamorphic nature during the 1.2–1.0 Ga Namaquan Orogeny. This study examines the structural development of the central Kakamas Domain of the eastern Namaqua Metamorphic Province, which has not been extensively studied previously. The compressional orogenic phase is associated with D1 and D2 deformation events during which northeast–southwest-directed shortening resulted in southwest-directed thrusting illustrated by an intra-domain thrust and southwest-verging isoclinal folds. The post-tectonic Friersdale Charnockite of the Keimoes Suite is emplaced during the D3 deformation event. Late reactivation of the intra-domain thrust in the Kakamas Domain to form the Neusspruit Shear Zone during the D4 event is of a monoclinic nature and is described as a deeply rooted structure with shear direction towards the east. This structure, together with the more local Neusberg Thrust Fault, forms part of an intensely flattened narrow basin in the eastern Namaqua Metamorphic Province. Strain and vorticity indices suggest a transpressional shearing across the Neusspruit Shear Zone and adjacent regions probably initiated during the reactivation of the intra-domain thrust. The ~1.2 to 1.8 km-wide, northwest–southeast striking dextral-dominated Neusspruit Shear Zone constitutes a western regional boundary for the supracrustal Korannaland Group and is composed of steep, narrow zones of relatively high strain, characterised by ductile deformation and penetrative strain.

Accretion and evolution of an Archaean high-grade grey gneiss – amphibolite complex: the Fiskefjord area, southern West Greenland

1997 ◽  
pp. 1-115 ◽  
Author(s):  
Adam A. Garde
Keyword(s):  
Continental Crust ◽  
Granulite Facies ◽  
Ductile Deformation ◽  
Repeated Injection ◽  
High Grade ◽  
Volcanic Origin ◽  
Granulite Facies Metamorphism ◽  
West Greenland ◽  
Facies Metamorphism ◽  
Grey Gneiss

NOTE: This monograph was published in a former series of GEUS Bulletin. Please use the original series name when citing this series, for example: Garde, A. A. 1997: Accretion and evolution of an Archaean high-grade grey gneiss – amphibolite complex: the Fiskefjord area, southern West Greenland. Geology of Greenland Survey Bulletin 177, 115 pp. _______________ The Fiskefjord area in southern West Greenland, part of the Akia tectono-stratigraphic terrane, comprises a supracrustal association and two groups of grey quartzo-feldspathic orthogneises c. 3200 and 3000 Ma old. The supracrustal association forms layers and enclaves in grey gneiss and may comprise two or more age groups. Homogeneous amphibolite with MORB-like but LIL element enriched tholeiitic composition predominates; part, associated with cumulate noritic and dunitic rocks, represents fragments of layered complexes. Heterogeneous amphibolite of likely submarine volcanic origin, (basaltic) andesitic amphibolite, leucogabbro-anorthosite, and minor pelitic metasediment occur. Disruption by magmatic and tectonic events and geochemical alteration have obscured primary origin: the supracrustal association may represent oceanic crust. Grey orthogneiss of the tonalite-trondhjemite-granodiorite (TTG) association was generated during continental accretion at c. 3000 Ma, most likely by partial melting of wet and hot tholeiitic basaltic rocks subducted in a convergent plate setting. Most dioritic gneiss is c. 220 Ma older. A 3040 Ma dioritic to tonalitic phase, enriched in P2O5 , Ba, Sr, K, Pb, Rb and LREE, probably was derived from metasomatised mantle. Intense deformation and metamorphism accompanied the 3000 Ma magmatic accretion.Thrusts along amphibolite-orthogneiss contacts were succeeded by large recumbent isoclines, upright to overturned folds, and local domes with granitic cores. Syntectonic granulite facies metamorphism is thought to be due to heat accumulation by repeated injection of tonalitic magma. Strong ductile deformation produced steep linear belts before the thermal maximum ceased, whereby folds were reorientated into upright south-plunging isoclines. Two large TTG complexes were then emplaced, followed by granodiorite and granite. Post-kinematic diorite plugs with unusually high MgO, Cr and Ni, and low LIL and immobile incompatible element contents, terminated the 3000 Ma accretion. Hybrid border zones and orbicular textures suggest rapid crystallisation from superheated magma. The diorites most likely formed from ultramafic magma contaminated with continental crust. Widespread high-grade retrogression preserved a granulite facies core in the south-west; to the east the retrogressed gneiss grades into amphibolite facies gneiss not affected by granulite facies metamorphism and retrogression. LIL elements were depleted during granulite facies metamorphism and reintroduced during retrogression, probably transported in anatectic silicate melts and in fluids. Rb-Sr isotope data, and relationships between retrogression, high-strain zones and granite emplacement, show that retrogression took place shortly after the granulite facies metamorphism, before terrane assembly at c. 2720 Ma, probably by movement of melts and fluids into the upper, marginal zone of granulite facies rocks from deeper crust still being dehydrated. Retrogression during Late Archaean terrane assembly was in narrow reactivated zones of ductile deformation; in the Proterozoic it occurred with faulting and dyke emplacement.Geochemical data are presented for Early Proterozoic high-Mg and mafic dykes. A rare 2085 Ma microgranite dyke strongly enriched in incompatible trace elements was formed by partial anatexis of Archaean continental crust.  

Deformation history and U–Pb zircon geochronology of the high grade metamorphic rocks within the Klaeng fault zone, eastern Thailand

2013 ◽  
Vol 77 ◽  
pp. 224-233 ◽  
Author(s):  
Pitsanupong Kanjanapayont ◽  
Piyanuch Kieduppatum ◽  
Urs Klötzli ◽  
Eva Klötzli ◽  
Punya Charusiri
Keyword(s):  
Fault Zone ◽  
Metamorphic Rocks ◽  
High Grade ◽  
Zircon Geochronology ◽  
Deformation History

Himalayan inverted metamorphism and syn-convergence extension as a consequence of a general shear extrusion

2001 ◽  
Vol 138 (3) ◽  
pp. 253-276 ◽  
Author(s):  
JEAN-CLAUDE VANNAY ◽  
BERNHARD GRASEMANN
Keyword(s):  
Simple Shear ◽  
Thermal Evolution ◽  
Pure Shear ◽  
Hanging Wall ◽  
Ductile Deformation ◽  
Metamorphic Rocks ◽  
High Grade ◽  
The South ◽  
Main Central Thrust ◽  
Shear Component

Two paradoxical geological features of the Himalaya are the syn-convergence extension and the inverted metamorphic isograds observed in the crystalline core zone of this orogen. This High Himalayan Crystalline Sequence corresponds to an up to 40 km thick sequence of amphibolite to granulite facies gneiss, bounded by the Main Central Thrust at the base, and by the extensional faults of the South Tibetan Detachment System at the top. Geochronological and structural data demonstrate that coeval movements along both the Main Central Thrust and South Tibetan Detachment System during Early to Middle Miocene times were related to a tectonically controlled exhumation of these high-grade metamorphic rocks. The High Himalayan Crystalline Sequence systematically shows an inverted metamorphic zonation, generally characterized by a gradual superposition of garnet, staurolite, kyanite, sillimanite + muscovite and sillimanite + K-feldspar isograds, from the base to the top of the unit. Recent kinematic flow analyses of these metamorphic rocks demonstrate the coexistence of both simple shear and pure shear during the ductile deformation. The simple shear component of such a general non-coaxial flow could explain a rotation of isograds, eventually resulting in an inversion. The pure shear component of the flow implies a thinning of the metamorphic sequence that must be balanced by a perpendicular stretching of the unit parallel to its boundaries. Inasmuch as seismic data show that both the Main Central Thrust and South Tibetan Detachment System converge at depth, a thinning of the wedge-shaped High Himalayan Crystalline Sequence should induce a ductile extrusion of these high-grade rocks toward the surface. Rapid extension at the top of the sequence could thus be the consequence of a general shear extrusion of this unit relative to its hanging wall. Moreover, this extensional movement should decrease with depth to become zero where the boundaries of the unit meet, accounting for the paradoxical convergence of the South Tibetan Detachment System toward the Main Central Thrust. Furthermore, a general flow combining simple shear and pure shear can reconcile inverted isograds with the lack of inverted pressure field gradient across the High Himalayan Crystalline Sequence, despite an intense non-coaxial deformation. In good agreement with the seismic, kinematic and P–T–t constraints on the Himalayan tectono-thermal evolution, general shear extrusion provides a consistent model accounting for both inverted isograds and rapid extension in a compressional orogenic setting.

scholarly journals High Temperature Reduced Granulite-Facies Nature of Garnetites in the Khabarny Mafic–Ultramafic Massif, Southern Urals: Evidence from Fluid and Mineral Analyses

2020 ◽  
Vol 61 (6) ◽  
Author(s):  
Ronald J Bakker ◽  
Evgenii Pushkarev ◽  
Anna P Biryuzova
Keyword(s):  
High Temperature ◽  
Fluid Inclusions ◽  
Electron Microprobe ◽  
Granulite Facies ◽  
Southern Urals ◽  
Metamorphic Rocks ◽  
High Grade ◽  
Ultramafic Massif ◽  
Fluid Environment ◽  
Formation Conditions

Abstract High-grade metamorphic rocks underlying the intrusive layered dunite–pyroxenite–gabbronorite East-Khabarny Complex (EKC) are integrated in the complex Khabarny mafic–ultramafic Massif in the Sakmara Allochthon zone in the Southern Urals. These rocks are associated with high-temperature shear zones. Garnetites from the upper part of the metamorphic unit close to the contact with EKC gabbronorite are chemically and texturally analysed to estimate their formation conditions and fluid regime. Fluids provide crucial information of formation conditions and evolution of these garnetites during high-grade metamorphism, and are preserved in channel positions within Si6O1812- rings of cordierite, and in fluid inclusions in quartz and garnet. Minerals and fluid inclusions of the garnetites are studied with X-ray fluorescence spectrometry, electron microprobe analyses, Raman spectroscopy, and microthermometry. The garnetites mainly consist of garnet (up to 80 vol. %), cordierite and quartz. Accessory minerals are rutile, ilmenite, graphite, magnetite and cristobalite. Granulite-facies metamorphic conditions of the garnetites are estimated with the garnet–cordierite–sillimanite–quartz geothermobarometer: temperatures of 740 to 830 ˚C and pressures of 770–845 MPa. The average garnet composition in end-member concentrations is 48·5 mole % almandine (±3·9), 34·7 mole % pyrope (±3·3), 10·3 mole % spessartine (±1·1), 1·8 mole % grossular (±1·5), and 1·5 mole % andradite (±1·5). The cordierite electron microprobe analyses reveal an average Mg2+ fraction of 0·79 ± 0·01 in the octahedral site. Relicts of a strong positive temperature anomaly (up to 1000 ˚C) are evidenced by the preservation of cristobalite crystals in garnet and the high titanium content of quartz (0·031 ± 0·008 mass % TiO2) and garnet (0·31 ± 0·16 mole % end-member Schorlomite-Al). The fluid components H2O, CO2, N2 and H2S are detected in cordierite, which correspond to a relatively oxidized fluid environment that is common in granulites. In contrast, a highly reduced fluid environment is preserved in fluid inclusions in quartz nodules, which are mono-fluid phase at room temperature and composed of CH4 (>96 mole %) with locally minor amounts of C2H6, N2, H2S and graphite. The fluid inclusions occur in homogeneous assemblages with a density of 0·349 to 0·367 g·cm-3. The CH4-rich fluid may represent peak-temperature metamorphic conditions, and is consistent with temperature estimation (∼1000 ˚C) from Ti-in-garnet and Ti-in-quartz geothermometry. Tiny CH4-rich fluid inclusions (diameter 0·5 to 2 µm) are also detected by careful optical analyses in garnet and at the surface of quartz crystals that are included in garnet grains. Graphite in fluid inclusions precipitated at retrograde metamorphic conditions around 300–310 ± 27 ˚C. Aragonite was trapped simultaneously with CH4-rich fluids and is assumed to have crystallized at metastable conditions. The initial granulite facies conditions that led to the formation of a cordierite and garnet mineral assemblage must have occurred in a relative oxidized environment (QFM-buffered) with H2O–CO2-rich fluids. Abundant intrusions or tectonic emplacement of mafic to ultramafic melts from the upper mantle that were internally buffered at a WI-buffered (wüstite–iron) level must have released abundant hot CH4-rich fluids that flooded and subsequently dominated the system. The origin of the granulite-facies conditions is similar to peak-metamorphic conditions in the Salda complex (Central Urals) and the Ivrea–Verbano zone (Italian Alps) as a result of magmatic underplating that provided an appearance of a positive thermal anomaly, and further joint emplacement (magmatic and metamorphic rocks together) into upper crustal level as a high temperature plastic body (diapir).

scholarly journals The plutonic igneous and high-grade metamorphic rocks of southern Liverpool Land, central East Greenland, part of a supposed Caledonian and Precambrian complex

1985 ◽  
Vol 123 ◽  
pp. 1-39
Author(s):  
R.F Cheeney
Keyword(s):  
Sedimentary Rock ◽  
Granulite Facies ◽  
Great Depth ◽  
Metamorphic Rocks ◽  
High Grade ◽  
Hydrous Minerals ◽  
East Greenland ◽  
North West ◽  
Rock Types ◽  
Extreme North

Layered metamorphic formations in southern Liverpool Land are disposed in dome-shaped structures with inclinations everywhere gentie. Meta-igneous and meta-sedimentary rock types are represented as well as formations of less clear affinities. Rocks of eclogitic character comprise part of one of the formations which, together with others of the layered succession, passes laterally into a less-deformed complex containing discordant contact relations of plutonic igneous type. The Hurry Inlet granite is a posttectonic, post-metamorphic formation cropping out in the extreme north-west of the area. The earliest detectable events indicate emplacement of granodiorite into sedimentary or metasedimentary formations. Subsequently, these rocks of igneous and sedimentary origin were raised to upper amphibolite or granulite facies with some deformation leading to the prominent layering and including, perhaps, their juxtaposition with eclogitic rocks originating at great depth. Retrogression to 'normal' amphibolite facies followed, with widespread development of hydrous minerals, pegmatites, etc. The position of limited cataclasis with respect to this later stage of metamorphism is not abundantly clear. Emplacement of the Hurry Inlet granite entirely post-dates all of these events.

Age constraints on ductile deformation and long-term slip rates along the Karakoram fault zone, Ladakh

2004 ◽  
Vol 226 (3-4) ◽  
pp. 305-319 ◽  
Author(s):  
Richard J. Phillips ◽  
Randall R. Parrish ◽  
Michael P. Searle
Keyword(s):  
Fault Zone ◽  
Ductile Deformation ◽  
Slip Rates ◽  
Karakoram Fault ◽  
Age Constraints

Amphibolite-granulite facies assemblages in southern Nyasaland

1961 ◽  
Vol 32 (252) ◽  
pp. 725-730 ◽  
Author(s):  
S. W. Morel
Keyword(s):  
Granulite Facies ◽  
Metamorphic Rocks ◽  
High Grade ◽  
Mineral Assemblages ◽  
Metamorphic Facies

SummaryThe mineral assemblages developed in a variety of high-grade metamorphic rocks from southern Nyasaland are compared with standard metamorphic facies mineral assemblages proposed by some authors.

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