Variation in lithology and tectonometamorphic relationships in the Precambrian basement of northern Saskatchewan

1977 ◽  
Vol 14 (6) ◽  
pp. 1453-1467 ◽  
Author(s):  
John F. Lewry ◽  
Thomas I. I. Sibbald
Keyword(s):  
Shear Zone ◽  
Granulite Facies ◽  
Mobile Belt ◽  
Western Boundary ◽  
Northern Saskatchewan ◽  
Virgin River ◽  
Granitic Intrusions ◽  
Granitoid Gneisses ◽  
Narrow Belt ◽  
Archean Basement

The southwestern part of the Precambrian Shield of northern Saskatchewan is divisible into five lithostructural domains. The lithological, structural, and metamorphic characters of these domains are described. The Mudjatik and Virgin River domains constitute parts of a more extensive mobile belt extending further east and share a common tectonometamorphic history. The western boundary of this (Hudsonian) mobile belt is marked by the Virgin River shear zone, a zone of repealed movement marked by a narrow belt of mylonite gneisses and sheared marginal granitic intrusions. To the west of the shear zone the Western Granulite and Firebag domains comprise elements of an earlier (Archean?)cratonic foreland, formed by granulite facies gneisses which are only mildly affected by later Hudsonian events. These two cratonic elements are separated by the Clearwater domain, a narrow mobile belt with a history broadly similar to that of the main mobile belt to the east.The Mudjatik and Virgin River domains are formed predominantly by granitoid gneisses, with supracrustal rocks appearing only in thin, often discontinuous zones. It is suggested that these relationships were achieved by remobilization of granitoid (Archean?) basement and preservation of the (Aphebian?) supracrustals between laterally moving, flat lying migmatite nappelobes.

New age constraints on magmatism and metamorphism in the Morin terrane (Grenville Province, Quebec)

2022 ◽  
Author(s):  
William H Peck ◽  
Matthew P Quinan
Keyword(s):  
Shear Zone ◽  
Granulite Facies ◽  
Western Boundary ◽  
Grenville Province ◽  
Granulite Facies Metamorphism ◽  
Metamorphic History ◽  
Crustal Block ◽  
Two Samples ◽  
Western Side ◽  
Age Constraints

The Morin terrane is an allochthonous crustal block in the southwestern Grenville Province with a relatively poorly-constrained metamorphic history. In this part of the Grenville Province, some terranes were part of the ductile middle crust during the 1.09–1.02 Ga collision of Laurentia with the Amazon craton (the Ottawan phase of the Grenvillian orogeny), while other terranes were part of the orogen’s superstructure. New U-Pb geochronology suggests that the Morin terrane experienced granulite-facies metamorphism during the accretionary Shawinigan orogeny (1.19–1.14 Ga) and again during the Ottawan. Seven zircon samples from the 1.15 Ga Morin anorthosite suite were dated to confirm earlier age determinations, and Ottawan metamorphic rims (1.08–1.07 Ga) were observed in two samples. U-Pb dating of titanite in nine marble samples surrounding the Morin anorthosite suite yielded mixed ages spanning between the Shawinigan and Ottawan metamorphisms (n=7), and predominantly Ottawan ages (n=2). Our results show that Ottawan zircon growth and resetting of titanite ages is spatially heterogeneous in the Morin terrane. Ages with a predominantly Ottawan signature are recognized in the Morin shear zone, which deforms the eastern lobe of the anorthosite, in an overprinted skarn zone on the western side of the massif, and in the Labelle shear zone that marks its western boundary. In the rest of the Morin terrane titanite with Shawinigan ages appear to have been only partially reset during the Ottawan. Further work is needed to better understand the relationship between the character of Ottawan metamorphism and resetting in different parts of the Morin terrane.

Evidence for deep crustal seismic rupture in a granulite-facies, intraplate, strike-slip shear zone, northern Saskatchewan, Canada

2018 ◽  
Vol 131 (3-4) ◽  
pp. 403-425 ◽  
Author(s):  
Omero F. Orlandini ◽  
Kevin H. Mahan ◽  
Michael J. Williams ◽  
Sean P. Regan ◽  
Karl J. Mueller
Keyword(s):  
Shear Zone ◽  
Granulite Facies ◽  
Strike Slip ◽  
Seismic Rupture ◽  
Northern Saskatchewan

scholarly journals The northern boundary of the Proterozoic (Nagssugtoqidian) mobile belt of South-East Greenland

1989 ◽  
Vol 146 ◽  
pp. 54-65
Author(s):  
P.R Dawes ◽  
N.J Soper ◽  
J.C Escher ◽  
R.P Hall
Keyword(s):  
Shear Zone ◽  
Shear Zones ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Mobile Belt ◽  
Basic Dyke ◽  
Northern Boundary ◽  
East Greenland ◽  
Diffuse Region

The Proterozoic mobile belt of South-East Greenland has been regarded as a classic example of amphibolite facies reworking of an Archaean granulite facies gneiss terrain. Its northern boundary has been interpreted as a transcurrent shear zone in which reworking was associated with major basic dyke emplacement. A re-examination of the northern boundary shows it to be a diffuse region more than 50 km wide in which retrogression, unrelated to dykes or shear zones, gradually intensifies southwards. Superimposed on this are discrete belts of retrogression associated with dykes and shear zones. The sense of displacement on the latter is compatible with thrusting of the northern Archaean block southwards over the reworked terrain of the mobile belt.

Petrophysical constraints on magnetic anomalies associated with metamorphic reactions in northern Saskatchewan, Canada

2019 ◽  
Vol 56 (9) ◽  
pp. 895-911
Author(s):  
Jeffrey R. Webber ◽  
Laurie L. Brown ◽  
Michael L. Williams
Keyword(s):  
Magnetic Susceptibility ◽  
Shear Zone ◽  
Remanent Magnetization ◽  
Magnetic Phase ◽  
Granulite Facies ◽  
Magnetic Data ◽  
Aeromagnetic Anomaly ◽  
Mineral Phases ◽  
Northern Saskatchewan ◽  
Magnitude Variation

The western Chipman domain of the east Athabasca mylonite triangle in northern Saskatchewan, Canada, displays a large positive aeromagnetic anomaly that is the result of retrograde magnetite production during exhumation. Petrologic, magnetic coercivity, and hysteresis analyses indicate that multidomain magnetite is the primary magnetic phase in rocks of the region. Measurements of magnetic susceptibility from the western Chipman domain document five orders of magnitude variation, while rocks from the eastern Chipman domain are paramagnetic. The distribution of Koenigsberger ratios is approximately a mixed bimodal lognormal distribution with peak ratios at 0.039 and 0.73, suggesting that magnetic susceptibility is more significant than remanent magnetization. However, remanent magnetization is an important contributor to total magnetization. Petrographic observations indicate that magnetite is primarily produced from the breakdown of hornblende. The consumption of hornblende is also texturally associated with the production of actinolite and the hydration-related breakdown of granulite facies mineral phases such as garnet and clinopyroxene. Based on the proximity of the positive aeromagnetic anomaly to the Cora Lake shear zone, late-stage deformation along the shear zone during exhumation of the east Athabasca mylonite triangle may have structurally controlled the infiltration of fluids resulting in the heterogeneous production of magnetite. These results document the utility of integrating aeromagnetic, petrologic, and rock magnetic data to transcend observational scales and better understand regional tectonometamorphic history.

scholarly journals Precambrian and Tertiary geology between Kangerdlugssuaq and Angmagssalik, East Greenland

1978 ◽  
Vol 83 ◽  
pp. 1-17
Author(s):  
D Bridgewater ◽  
F.B Davis ◽  
R.C.O Gill ◽  
B.E Gorman ◽  
J.S Myers ◽  
...  
Keyword(s):  
Large Scale ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Mobile Belt ◽  
East Greenland ◽  
Reconnaissance Survey ◽  
Gneiss Complex ◽  
Igneous Intrusions ◽  
Igneous Complexes ◽  
Granitoid Gneisses

The preliminary results of a reconnaissance survey of the coast between Kangerdlugssuaq and Angmagssalik are summarized. The Archaean gneiss complex between Kangerdlugssuaq and Kap Japetus Steenstrup is fairly uniform and comprises granitoid gneisses with inclusions of supracrustal rocks, layered basic igneous complexes and older gneisses. Inland areas generally show low deformation states, large scale recumbent folds, and rocks are in granulite facies, whereas a belt of stronger deformation, steep foliation and amphibolite facies matamorphism extends alng the outer coast. To the south of Kap Japetus Steenstrup, Archaean rocks are strongly deformed in the Nagssugtoqidian mobile belt and granulite facies rocks are retrograded to amphibolite facies, except in pods of low deformation, between 2800--2600 m.y. ago. Large bodies of diorite and granodiorite (the Blokken gneisses) were emplaced and metamorphosed in amphibolite facies 2400 m.y. ago, and around Angmagssalik a complex of Ieuco-norite and charnockite was emplaced in granulite facies and caused coarse recrystallization of the adjacent gneisses. Post-tectonic igneous intrusions ranging from ultramafic to granite were intruded 1600 m.y. ago. Numerous Tertiary dykes and plutonic complexes ranging from gabbro to granite were emplaced along the coast between Tasilaq and Kangerdlugssuaq 60-35 m.y. ago.

High-pressure granulite facies metamorphism of Archean Bastar craton at the interface of Eastern Ghats Belt: Implications for cratonic subduction/underthrusting

2021 ◽  
Author(s):  
Padmaja Jayalekshmi ◽  
Tapabrato Sarkar ◽  
Somnath Dasgupta ◽  
Rajneesh Bhutani
Keyword(s):  
High Pressure ◽  
Shear Zone ◽  
Granulite Facies ◽  
Eastern Ghats ◽  
Mobile Belt ◽  
High Grade ◽  
Granulite Facies Metamorphism ◽  
Bastar Craton ◽  
High Pressure Granulite ◽  
Facies Metamorphism

<p>The Bastar Craton at the interface of Eastern Ghats Belt (EGB) contains a mélange of rocks from both the Archean cratonic domain and the adjacent Proterozoic mobile belt domain marking a broad shear zone, known as the Terrane Boundary Shear Zone (TBSZ). The TBSZ preserves a very rare occurrence of high-grade metamorphosed Archean cratonic rocks, whose ancestry has been constrained by Nd model ages. This study presents the petrological and geochemical characterization of mafic granulites and orthopyroxene bearing granitoids from the shear zone and its implications on the tectonic evolution of the craton – mobile belt boundary. Detailed petrographic, geothermobarometric and P-T pseudosection studies indicate that the Bastar cratonic rocks underwent high-pressure granulite facies metamorphism along a clockwise P-T path, reaching ~900°C and 9-10 kbar. The originally amphibolite facies rocks, metamorphosed through dehydration-melting of hornblende (mafic rocks) and biotite (felsic rocks), to attain the peak P-T conditions. We suggest that this high-grade metamorphism was due to the subduction/underthrusting of the Bastar Craton beneath the EGB, supported by the available seismic data, which resulted from far-field stress related to the Kuunga orogeny in an intraplate setting.</p>

scholarly journals Exotic garnet–clinopyroxene–K-feldspar granulites from the Chepelare shear zone, Central Rhodope massif, Bulgaria: implications for high-pressure granulite facies metamorphism

2019 ◽  
Vol 48 (3) ◽  
pp. 49-63
Author(s):  
Milena Georgirva ◽  
Tzvetomila Vladinova
Keyword(s):  
Shear Zone ◽  
Thick Layer ◽  
Granulite Facies ◽  
Mineral Association ◽  
Granulite Facies Metamorphism ◽  
Fine Grain ◽  
Fluid Infiltration ◽  
High Pressure Granulite ◽  
The Matrix ◽  
Homogeneous Matrix

Garnet–clinopyroxene–K-feldspar granulite occurs as a thick layer or boudin within the variegated rocks of the Chepelare shear zone in the Central Rhodope massif, Bulgaria. It consists of several domains: mesocratic homogeneous matrix (clinopyroxene–plagioclase–K-feldspar–quartz ± amphibole), porphyroblastic garnet, K-feldspar and clinopyroxene, and strongly foliated fine-grain bands (chloritized biotite–chlorite–prehnite–albite ± epidote). The origin and nature of the matrix mineral association is still unclear. The peak porphyroblast association forms at the expense of plagioclase from the matrix at higher pressure. The fine-grain deformation zones channel the lattermost fluid infiltration. The clinopyroxene-garnet and Zr-in-titanite thermometry give temperatures higher than 790–860 ºC at 2 GPa and, with thermodynamic modeling, suggests crystallization at ~1.8–2.1 GPa and temperature of ~850 ºC in HP granulite field for the porphyroblast granulite association.

scholarly journals A NEW GOLD ORE REGION IN TANZANIA

2018 ◽  
pp. 55-59
Author(s):  
V. Mykhailov ◽  
А. Tots
Keyword(s):  
Gold Deposit ◽  
Shear Zone ◽  
Gold Mineralization ◽  
Lake Victoria ◽  
Gold Deposits ◽  
Mobile Belt ◽  
Gold Content ◽  
Gold Ore ◽  
Metallogenic Zone ◽  
The Republic

Tanzania is one of the leading gold mining countries in the world and the discovery of new gold resources on its territory is an actual task. Known gold deposits are concentrated mainly in the northwest of the country, in the metallogenic zone of Lake Victoria, where they are associated with the Archean greenstone belts, and to a lesser extent – in the southwest, in the ore regions of Lupa and Mpanda, confined to the Ubendian Paleoproterozoic mobile belt. With regard to the eastern regions of Tanzania, where the Proterozoic structures of the Uzagaran mobile belt are developed, until recently in this region any significant manifestations of gold mineralization were not known. As a result of our research in the northern part of the Morogoro province of the Republic of Tanzania, a new previously unknown gold deposit Mananila was discovered. It is represented by a large volume, up to 400–450 m long, up to 60–80 m thick, mineralized shear zone over intensely leached and schistosed migmatites, gneisses, amphibolites, penetrated by echelon systems of quartz veins and veinlet, steeply dipping bodies of quartz breccia up to 1.0–1.5 m thick. Gold contents range from 0.61 to 8.11 g/t, the average zone content is 2.5–3.0 g/t. Parallel to the main zone, similar structures are developed on the site, although they are of lower thickness. The forecast resources of the deposit are estimated at 20 tons of gold. 2.8 km to the east from the Mananila field, the recently discovered Mazizi gold deposit is located, and a number of small occurrences of gold are also known in the region. All these objects are located within a large shear zone of the northeastern strike, up to 4–5 km width, over 20 km in length. This serves as the basis for the identification of a new gold ore region in the northern part of the Morogoro province of the United Republic of Tanzania, within the Proterozoic mobile belt of Usagaran, the possible gold content of which has never been previously discussed in geological literature.

scholarly journals Outline of the Nagssugtoqidian mobile belt of East Greenland

1979 ◽  
Vol 89 ◽  
pp. 9-18
Author(s):  
D Bridgwater ◽  
J.S Myers
Keyword(s):  
Shear Zones ◽  
Granulite Facies ◽  
Tectonic Activity ◽  
Mobile Belt ◽  
East Greenland ◽  
The North ◽  
Marginal Areas ◽  
High Level ◽  
North And South ◽  
Wide Zone

The Nagssugtoqidian mobile belt is a 240 km wide zone of deformation and plutonic activity which cuts across the Archaean craton of East Greenland. The belt was established 2600 m.y. ago by the formation of vertical E-W shear zones and the syntectonic intrusion of basic dykes. Tectonic activity along the E-W shear zones was followed by the emplacement of tonalitic intrusions, the Blokken gneisses, 2350 m.y. ago in the central parts of the mobile belt. The emplacement of the Blokken gneisses was accompanied and followed by further emplacement of basic dykes. These are synplutonic in the centre of the mobile belt but are emplaced into more rigid crust in the marginal areas of the belt and in the Archaean craton to the north and south. During a second major tectonic and thermal episode circa 1900 m.y. ago, the region was deformed by thrusting from the north. In the southem part of the mobile belt the earlier steep shear zones are cut by shear zones dipping gently northwards in which rocks are downgraded to greenschist facies. The grade of metamorphism increases northwards and shear zones are replaced by open folds with axial surfaces which dip gently northwards. The increasing ductility in the centre of and northem part of the belt is associated with the intrusion of charnockitic plutons and their granulite facies aureoles. Regional uplift occurred before the intrusion of high level post-tectonic plutons of diorite and granite 1550 m.y. ago.

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