Tectonic evolution of two greenstone belts from the Superior Province in Manitoba

1978 ◽  
Vol 15 (11) ◽  
pp. 1808-1816 ◽  
Author(s):  
R. G. Park ◽  
I. F. Ermanovics
Keyword(s):  
Tectonic Evolution ◽  
Superior Province ◽  
The North ◽  
Crenulation Cleavage ◽  
Facies Metamorphism ◽  
Tonalitic Gneiss ◽  
Uniform Stress Field ◽  
Greenstone Belts ◽  
East West ◽  
Lower Group

The Bigstone Lake and Stevenson Lake greenstone belts are two areas of supracrustal rocks surrounded by quartz diorite to granodiorite plutons and by small patches of tonalitic gneiss interpreted as basement to the greenstone belts. The supracrustal sequence is divided into a lower, mainly volcanic, group correlated with the Hayes River Group of Island Lake and an unconformable upper group with roughly equal proportions of sediments and volcanics correlated with the Island Lake 'Series'. The lower group consists of about 4600 m of basaltic and andesitic pillow lavas with minor greywackes and dacitic volcanics. It is partly replaced at the base by the bordering plutons and cut out at the top by the unconformable upper group, which consists of about 2300 m of greywackes, arkoses, and mudstones above a basal conglomerate containing boulders derived from the lower group and from the basement. A further 2100 m of volcanics overlies these sediments.The supracrustal rocks show three phases of deformation. The first, F1, produced major northeast–southwest and east–west synclines. S1 foliation was developed under greenschist facies to low amphibolite facies metamorphism. F2 produced smaller scale steep east–west folds with a crenulation cleavage. Subsequent deformation resulted in chevron folds and conjugate shear belts.The intrusion of the plutons commenced before the F1 deformation and partly controlled it, but a further period of plutonic intrusion occurred after F1 and before F2.The north–south compressive stress prevailing during F2 and later deformation under waning metamorphism implies that the batholiths in the vicinity of the greenstone belts had completely solidified and that the crust was rigid enough to transmit a uniform stress field. The dominance of east–west structural grain in this part of the Superior Province indicates that these conditions were general.

Variable unroofing in the western Superior Province - metamorphic evidence and possible origin

2006 ◽  
Vol 43 (7) ◽  
pp. 805-819 ◽  
Author(s):  
Andrew Hynes ◽  
Zixin Song
Keyword(s):  
Superior Province ◽  
Surface Distribution ◽  
Seismic Line ◽  
The North ◽  
Metavolcanic Rocks ◽  
Limited Support ◽  
Greenstone Belts ◽  
Rotation Motion ◽  
East West ◽  
Broad Region

Western Superior Lithoprobe seismic-reflection line 1 exhibits a broad region of northward-dipping reflectors in the Uchi subprovince, which gives way to southward-dipping reflectors farther north in the Berens River sub province. Mafic metavolcanic rocks across the region of northward-dipping reflectors exhibit a decline in metamorphic pressure, from pressures of 6 kbar (1 kbar = 100 MPa) in the south to only 2 kbar 80 km to the north. This indicates that the southern edge of the Uchi subprovince has undergone significantly more unroofing than regions farther north. The differential unroofing is not consistent with a doubly vergent thrusting origin for the northward- and southward-dipping reflector pattern. It could result from a crustal-scale synform, of which the region of northward-dipping reflectors would make up the southern limb. Metamorphic pressures from samples off the seismic line, however, provide only limited support for a regional synform, and suggest that much of the pressure variation may result from deformation associated with motion on late faults that are widespread in the western Superior Province. These faults occur in a WNW-striking set with dextral offsets and an ENE-striking set with sinistral offsets. They could result from north–south compression and east–west extension, provided the faults have rotated towards the east–west direction during deformation. Regional tilting and (or) jostling of crustal blocks is attributed to deformation associated with the fault rotation. Motion on the faults and the associated deformation of intervening fault blocks may be important contributors to the present crustal architecture of the western Superior Province, including the surface distribution and form of the greenstone belts.

New high-precision U–Pb ages for the Island Lake greenstone belt, northwestern Superior Province: implications for regional stratigraphy and the extent of the North Caribou terrane

2006 ◽  
Vol 43 (7) ◽  
pp. 789-803 ◽  
Author(s):  
Jen Parks ◽  
Shoufa Lin ◽  
Don Davis ◽  
Tim Corkery
Keyword(s):  
Shear Zone ◽  
High Precision ◽  
Greenstone Belt ◽  
Superior Province ◽  
Geological History ◽  
Isotopic Data ◽  
Mapping Study ◽  
The North ◽  
Crustal Block ◽  
Greenstone Belts

A combined U–Pb and field mapping study of the Island Lake greenstone belt has led to the recognition of three distinct supracrustal assemblages. These assemblages record magmatic episodes at 2897, 2852, and 2744 Ma. Voluminous plutonic rocks within the belt range in age from 2894 to 2730 Ma, with a concentration at 2744 Ma. U–Pb data also show that a regional fault that transects the belt, the Savage Island shear zone, is not a terrane-bounding structure. The youngest sedimentary group in the belt, the Island Lake Group, has an unconformable relationship with older plutons. Sedimentation in this group is bracketed between 2712 and 2699 Ma. This group, and others similar to it in the northwestern Superior Province, is akin to Timiskaming-type sedimentary groups found throughout the Superior Province and in other Archean cratons. These data confirm that this belt experienced a complex geological history that spanned at least 200 million years, which is typical of greenstone belts in this area. Age correlations between the Island Lake belt and other belts in the northwest Superior Province suggest the existence of a volcanic "megasequence". This evidence, in combination with Nd isotopic data, indicates that the Oxford–Stull domain, and the Munro Lake, Island Lake, and North Caribou terranes may have been part of a much larger reworked Mesoarchean crustal block, the North Caribou superterrane. It appears that the Superior Province was assembled by accretion of such large independent crustal blocks, whose individual histories involved extended periods of autochthonous development.

40Ar/39Ar Incremental Release Ages of Biotite and Hornblende from Pre-Kenoran Gneisses between the Matagami-Chibougamau and Frotet-Troilus Greenstone Belts, Quebec

1974 ◽  
Vol 11 (11) ◽  
pp. 1586-1593 ◽  
Author(s):  
R. D. Dallmeyer
Keyword(s):  
High Temperature ◽  
Tectonic Evolution ◽  
Superior Province ◽  
High Grade ◽  
Continuous Increase ◽  
Thermal Event ◽  
Greenstone Belts ◽  
Orogenic Belts ◽  
Gas Fractions

Biotite and hornblende from high-grade, granitic gneisses exposed between the Matagami-Chibougamau and Frotet-Troilus greenstone belts in Quebec have been affected by Kenoran metamorphism. Biotites record total gas 40Ar/39Ar ages of 2308 ± 30 m.y. and 2338 ± 30 m.y. Incrementally released gas fractions yield similar plateau ages, suggesting that the biotites have been totally degassed as a result of the thermal event. The ages are interpreted as reflecting the time of post-metamorphic cooling when radiogenic 40Ar began to be retained within biotite. Hornblendes record total gas 40Ar/39Ar ages of 2517 ± 40 m.y. and 2610 ± 40 m.y. Incrementally released gas fractions show a wide deviation from the total gas ages, with a continuous increase in age from low to high temperature release fractions. This lack of correlation suggests that the hornblendes have been only partially degassed by Kenoran metamorphism. However, lack of a high-temperature release plateau indicates that original meramorphic crystallization was older than the ages recorded by the highest temperature release fractions (2599 ± 40 and 2801 ± 40 m.y.). Recognition of an older sialic terrain between these greenstone belts supports recent models proposed for the tectonic evolution of the supracrustal orogenic belts in the Superior Province.

U–Pb age constraints for the magmatic and tectonic evolution of the Pontiac Subprovince, Quebec

1993 ◽  
Vol 30 (9) ◽  
pp. 1970-1980 ◽  
Author(s):  
J. K. Mortensen ◽  
K. D. Card
Keyword(s):  
Tectonic Evolution ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Volcanic Zone ◽  
Volcanic Arcs ◽  
The North ◽  
Intrusive Rocks ◽  
History Of ◽  
Tonalitic Gneiss ◽  
Age Constraints

New U–Pb zircon, titanite, and monazite ages help constrain the history of magmatism and tectonism within the Pontiac Subprovince of western Quebec. The Pontiac Subprovince resembles other metasedimentary belts of the Superior Province; however, the stratigraphic relationships between the dominantly sedimentary rocks of the Pontiac and the adjacent, volcanic-dominated Abitibi belt to the north and west remain controversial. Volcanic rocks of the Belleterre volcanic zone in the southern part of the Pontiac Subprovince have been interpreted by other workers as klippen of Abitibi strata that were thrust southward onto the Pontiac Subprovince. However, volcanic rocks in the Belleterre zone give crystallization ages of 2689–2682 Ma, which are younger than any extrusive rocks dated thus far from the Abitibi belt. Single detrital zircon grains from Pontiac sedimentary rocks give ages as young as 2683 Ma, indicating that the sediments are similar in age, or younger than, the volcanic units. The volcanic rocks probably represent distal facies of small volcanic arcs deposited within a large turbidite basin.The Lac des Quinze tonalitic gneiss body gives U–Pb zircon and titanite ages of 2695 ± 1 Ma and 2673 ± 4 Ma, respectively. Although the gneiss may represent basement to the supracrustal units, field relationships indicate that it was tectonically juxtaposed against the supracrustal package. Alkaline intrusive rocks in the Pontiac Subprovince yield U–Pb ages that overlap with the youngest ages obtained from the volcanic units. This attests to a very short-lived cycle of sedimentation and arc magmatism, followed by late tectonic and posttectonic alkaline plutonism.

Déformation coaxiale en bordure de la discontinuité structurale de Lyndhurst, sous-province de l'Abitibi

1992 ◽  
Vol 29 (4) ◽  
pp. 783-792 ◽  
Author(s):  
Jean-Yves Labbé ◽  
Real Daigneault ◽  
Pierre A. Cousineau
Keyword(s):  
Structural Analysis ◽  
Deformation Zone ◽  
Thrust Fault ◽  
The South ◽  
Mesoscopic Scale ◽  
The North ◽  
The Poor ◽  
Crenulation Cleavage ◽  
Deformation Regime ◽  
East West

The Lyndhurst discontinuity is a major east–west structure located some 40 km north of Rouyn–Noranda. It separates the rhyolitic and sedimentary units of the Hunter Mine Group to the north from the basalts of the Kinojévis Group to the south. Evidence of deformation is observed only in the rhyolites and sediments along the south edge of the Hunter Mine Group. The deformation zone is approximately 1 km wide and is continuous for about 30 km. The Kinojévis Group rocks are not deformed. Deformed rhyolites show a strong sericite and chlorite alteration of hydrothermal origin. The competency of the rhyolites is significantly reduced by the presence of these phyllosilicates, which results in the deformation being preferentially localized in the more altered rocks. Competency contrasts observed on a mesoscopic scale are also valid on the microscopic and megascopic scales. The structural analysis of the deformation zone reveals different arrays that characterize three distinct sectors. These arrays reflect competency contrasts of the lithology and a crenulation cleavage. The stretching lineation is generally steeply plunging. Although the deformation seems significant in a zone contiguous to the Lyndhurst discontinuity, the poor development of the stretching lineation, the preservation of the original crystalline shapes of phenocrysts in the rhyolites, and the constant symmetry of the pressure shadows suggest a global coaxial deformation. This deformation regime is difficult to reconcile with a compressive fault such as a thrust fault.

Paleomagnetism of Archean granites and Matachewan dikes in the Wawa Subprovince, Ontario: reevaluation of the Archean apparent polar wander path

1990 ◽  
Vol 27 (8) ◽  
pp. 1031-1039 ◽  
Author(s):  
T. A. Vandall ◽  
D. T. A. Symons
Keyword(s):  
Single Component ◽  
Superior Province ◽  
Polar Wander ◽  
Early Proterozoic ◽  
Dike Swarm ◽  
The North ◽  
Apparent Polar Wander Path ◽  
Quartz Monzonite ◽  
Greenstone Belts ◽  
Tectonic Rotation

Paleomagnetic measurements have been completed on 400 specimens from dated Archean granites and Matachewan dikes in the Michipicoten and Gamitagama greenstone belts in the western Wawa Subprovince of the Superior Province, Ontario. Detailed alternating-field and thermal step demagnetization analyses were used to isolate stable remanence directions. A single-component remanence was isolated within three adjacent dated granitic plutons on the eastern margin of the Michipicoten belt, including the Hawk Lake trondhjemite, the Southern external granite, and the Eastern external granite (HSE). The maximum possible age for this remanence is constrained by the intrusion of the last pluton at 2694 Ma. The corresponding HSE paleopole is located at 10°W, 41°S (dp = 8°, dm = 13°). A second paleopole, NB, is derived from the Northern external granite and the Baldhead River quartz monzonite, which give U–Pb zircon ages of 2662 and 2668 Ma, respectively. Their single-component remanence defines a paleopole on the Archean apparent polar wander path (APWP) at 15°E, 27°S (dp = 8°, dm = 13°), with a maximum possible age of 2.66 Ga. A third paleopole, GD, is derived from the north-northwest-trending Gamitagama diabase dikes and yields a position of 57°E, 41°N (dp = 7°, dm = 14°), which agrees with poles determined by other workers from the 2454 Ma Matachewan dike swarm. The GD pole, along with previously determined Matachewan dike poles, demonstrates that a tectonically stable craton has existed since intrusion of this extensive dike swarm, and it improves the precision of the 2454 Ma Matachewan pole on the APWP. These poles, when compared with coeval poles from the eastern side of the Kapuskasing Structural Zone in the Superior Province, imply no tectonic rotation or translation between the Wawa and Abitibi subprovinces along this Early Proterozoic structure.

Polyphase deformation and crustal evolution in the Pipestone Lake area of the Archean Wabigoon Subprovince, Superior Province, Canada

1999 ◽  
Vol 36 (3) ◽  
pp. 459-477 ◽  
Author(s):  
Garth R Edwards ◽  
Mel R Stauffer
Keyword(s):  
Shear Zone ◽  
Canadian Shield ◽  
Superior Province ◽  
Crustal Evolution ◽  
Lake Area ◽  
Polyphase Deformation ◽  
Crenulation Cleavage ◽  
East West

Archean supracrustal rocks in the western Wabigoon Subprovince, Superior Province, Canadian Shield, have undergone four phases of deformation, D1-D4. D1, confined to the oldest rocks, includes a large, refolded, reclined, isoclinal anticline (F1) with moderately developed axial-planar cleavage (S1). Rocks affected by D1 are overlain by a regional unconformity. D2 includes post-unconformity, steeply plunging, north-northeast-south-southwest-striking, isoclinal folds (F2) that are approximately coaxial with F1, but have contorted the F1 axial trace. D3 is represented by east-west-striking, steeply plunging folds at various scales (F3) which occur mainly in rocks near the regional Manitou Stretch - Pipestone Lake Shear Zone, also interpreted to be a D3 structure. D4 is represented by pervasive cleavage (S4), locally penetrative but mainly spaced, including crenulation cleavage, fractures, small faults, and brittle-ductile shears. S4 is parallel to the margin of the Jackfish Lake Pluton. D1-D3 are ascribed to convergence of the Wabigoon Subprovince with adjacent subprovinces, ending with formation of the Manitou Stretch - Pipestone Lake Shear Zone as a (presently) steep thrust and oblique-ramp structure. D4 is the result of either diapiric emplacement of the Jackfish Lake Pluton, or marginal strain intensification due to the rigidity of the older Ash Bay Dome during late north-south compression. Previously available zircon U-Pb geochronology provides a maximum age for D1 of 2728 Ma, and an approximate age for D4 of 2698 Ma. The unconformity developed between D1 and D2, 2725-2713 Ma.

The transition from dyke to sill in the Otish Mountains, Quebec; relations to host-rock characteristics

1987 ◽  
Vol 24 (1) ◽  
pp. 110-116 ◽  
Author(s):  
E. H. Chown ◽  
Guy Archambault
Keyword(s):  
Host Rock ◽  
Sedimentary Basin ◽  
Superior Province ◽  
Sedimentary Sequence ◽  
Grenville Province ◽  
Clastic Rocks ◽  
The North ◽  
Dyke Swarms ◽  
East West

The Otish gabbro sills intrude Aphebian clastic rocks lying uncanformably on the Archean rocks of the Superior Province close to its juncture with the Grenville Province. The sills are undated but by inference may be ca. 1750 Ma. Two dyke swarms are known in the vicinity, the 1950 Ma, northwest-trending Mistassini dykes and a northeast-trending swarm of unknown age extending 600 km from Senneterre to the Otish Mountains and possibly another 300 km to the northeast. The trends of feeder dykes to the Otish sills are physically compatible with the dominant northeast dykes, which are therefore considered to be the feeders and should be called the Otish dykes.The Otish sills appear to be a unique occurrence along the 900 km dyke trend, possibly, but not entirely because of the chances of preservation. The general form of the Otish sill complex is a triangle bounded on the north by the east–west lip of the sedimentary basin, on the southwest by a northwest-trending Otish feeder dyke, and on the southeast by the underlying northeast feeder dykes. These dykes segment the sills into a series of four or five separate intrusive complexes, small in the northwest and becoming larger to the southeast. The regular inclination of tension fractures in the basal chilled margin of the sills suggests a crude pattern of flow from the feeder dykes inward to the centre of the sheets.Interpretation of the sedimentary sequence indicates that the Otish clastics were deposited higher on the paleoslope than the Mistassini carbonates. Although few dykes intrude the deeper basin, the magma rose and formed sills within the higher sequence. This variation may be explained by the different mechanical character of the two types of cover rock controlling the dyke behaviour. The relatively plasto-viscous Mistassini carbonate–shale sequence resisted the formation of tension fractures, whereas the brittle elastics opened easily, allowing the magma to rise into the stratified sequence, forming the sill complexes.

Cooperative seismic surveys across the Superior–Churchill boundary zone in southern Canada

1980 ◽  
Vol 17 (5) ◽  
pp. 617-632 ◽  
Author(s):  
A. G. Green ◽  
O. G. Stephenson ◽  
G. D. Mann ◽  
E. R. Kanasewich ◽  
G. L. Cumming ◽  
...  
Keyword(s):  
Velocity Structure ◽  
Small Region ◽  
Superior Province ◽  
Boundary Zone ◽  
Reflection Point ◽  
Preliminary Results ◽  
The North ◽  
Seismic Surveying ◽  
Point Data ◽  
East West

Three seismic surveying techniques have been employed in a study of the Superior–Churchill boundary zone in southwestern Manitoba and southeastern Saskatchewan. Two reversed refraction – wide angle reflection profiles, one north–south within the Superior tectonic province and one east–west traversing part of the Superior tectonic province, the boundary zone, and part of the Churchill tectonic province, were used to obtain information on the gross velocity structure of the crust over a large region. Preliminary results from these surveys suggest that the crust beneath the north–south profile is typical of previously published crustal models of the western Superior Province, while the crust beneath the east–west profile is similar to that reported for the Churchill Province in eastern Alberta and western Saskatchewan. Generally, the upper and middle crustal sections in the two tectonic provinces are quite similar, while the lower crust in the Churchill Province has a distinct ~7 km/s layer that is not observed in this part of the Superior Province. In addition, there is a marked thickening of the crust within the boundary zone from ~41 km in the Superior Province to ~46 km in the Churchill Province.A 72 km length of fourfold common reflection point coverage was collected in order to determine the fine structure of the crust over a relatively small region. Reliable stacking velocities that may be used for future processing of the common reflection point data were obtained from an expanding spread reflection survey. Various data processing techniques, including common reflection point stacking, linear and nonlinear velocity filtering, and velocity spectral analysis, have been successful in enhancing reflections from the middle and lower parts of the crust. From the preliminary results of the two reflection surveys, it may be concluded that those parts of the crust which are shown as relatively simple layers in the refraction derived models, may be quite complex when viewed on a smaller scale.

Chronology of transpression, magmatism, and sedimentation in the Thompson Nickel Belt (Manitoba, Canada) and timing of Trans-Hudson Orogen – Superior Province collisionThis article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh.

2011 ◽  
Vol 48 (2) ◽  
pp. 295-324 ◽  
Author(s):  
Nuno Machado ◽  
Denis Gapais ◽  
Alain Potrel ◽  
Gilles Gauthier ◽  
Erwan Hallot
Keyword(s):  
Crustal Thickening ◽  
Superior Province ◽  
Mafic Intrusions ◽  
The North ◽  
Continental Block ◽  
Diffuse Zone ◽  
Detrital Zircon Ages ◽  
Superior Craton ◽  
East West ◽  
Group Part

The Thompson Nickel Belt marks the boundary between the Archean Superior Province and the Trans-Hudson Orogen in Canada. It comprises Archean gneisses, and Paleoproterozoic rocks with metasediments and metavolcanites (Ospwagan Group) and intrusions. The gneisses are frequently migmatitic and host numerous pegmatites. The western belt boundary is a fault contact with the Kisseynew Domain of the Reindeer Zone. In the south, the transition zone between the belt and the Kisseynew Domain comprises granitoids and a detrital sequence (Grass River Group), part of which grades into turbidites in the Kisseynew Domain. The eastern belt boundary is a diffuse zone where the Archean east–west (E–W) structural trend changes into the north-northeast (NNE) trend of the belt. This paper presents U–Pb ages for granitoids and 207Pb/206Pb detrital zircon ages from the Ospwagan and Grass River groups. Ages and a comparison of events in the belt and in the eastern Reindeer Zone have major implications. The change from stable platform deposits to syn-tectonic filling and emplacement of mafic intrusions in the Ospwagan Group are attributed to the convergence between the Reindeer Zone and the Superior Province at 1891–1885 Ma. At ca. 1850 Ma, continuing convergence led to drowning of marginal basins of the Superior craton and to the development of a transpressive regime in the belt, the onset of which could be as old as ca. 1885 Ma. Metamorphic ages of 1818–1785 record closure of the Kisseynew basin and crustal thickening. Collision of the new continental block with the Superior Province was accommodated by transpression until 1750–1720 Ma.

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