Trench and slope basin deposits in an Archean metasedimentary belt, Superior Province, Canadian Shield

1992 ◽  
Vol 29 (12) ◽  
pp. 2551-2557 ◽  
Author(s):  
Philip Fralick ◽  
Jinhua Wu ◽  
Howard R. Williams
Keyword(s):  
Shallow Water ◽  
Canadian Shield ◽  
Complex Medium ◽  
Superior Province ◽  
Accretionary Complex ◽  
Forearc Basin ◽  
Northwestern Ontario ◽  
Depositional Systems

The identification of a late Archean arc–trench assemblage in northwestern Ontario provides the opportunity to compare depositional systems developed in a Precambrian convergent setting with Cenozoic examples. Two types of sedimentary associations exist in the accretionary complex. Medium- to thick-bedded Bouma A, AB, and ABC felsic turbidites dominate the belt. These are primarily organized into unstructured sequences and reflect deposition in a ramp-like environment with multiple feed points supplying sediment from a forearc basin. Mafic turbidites with possible shallow water reworked intervals form isolated pods within the metasedimentary belt. Erosion of upthrust blocks of sedimentary strata containing ultramafic masses supplied this sediment to elevated slope basins. These types of depositional systems are similar in many respects to those developed in Cenozoic and Holocene arc–trench settings.

Orthoquartzite pebbles in Archean conglomerate, North Spirit Lake, northwestern Ontario

1977 ◽  
Vol 14 (9) ◽  
pp. 1980-1990 ◽  
Author(s):  
J. A. Donaldson ◽  
Richard W. Ojakangas
Keyword(s):  
Greenstone Belt ◽  
Sedimentary Rocks ◽  
Canadian Shield ◽  
Superior Province ◽  
Lake Area ◽  
Definite Evidence ◽  
The North ◽  
Northwestern Ontario ◽  
Form Part ◽  
Quartz Grains

An Archean conglomerate in the North Spirit Lake area of northwestern Ontario contains rare orthoquartzite pebbles. Detailed study of these pebbles shows that mineralogically they are very mature, consisting of as much as 99.8 percent quartz and a heavy mineral suite of zircon, tourmaline, and apatite. Textures are typically bimodal, characterized by rounded sand-sized quartz grains set in a 'matrix-cement' of thoroughly recrystallized finer quartz grains. These orthoquartzite pebbles provide the first definite evidence for local tectonic stability of the Canadian Shield before deposition of the immature sedimentary rocks that form part of an Archean (>2.6 Ga) greenstone belt of the Superior Province.

scholarly journals METAMORPHISM OF THE CANADIAN SHIELD, ONTARIO, CANADA. I. THE SUPERIOR PROVINCE

2000 ◽  
Vol 38 (2) ◽  
pp. 287-317 ◽  
Author(s):  
R. M. Easton
Keyword(s):  
Canadian Shield ◽  
Superior Province

Some new measurements of heat flow in the Superior Province of the Canadian Shield

1987 ◽  
Vol 24 (7) ◽  
pp. 1486-1489 ◽  
Author(s):  
Malcolm Drury ◽  
Alan Taylor
Keyword(s):  
Standard Deviation ◽  
Heat Flow ◽  
Canadian Shield ◽  
Superior Province ◽  
Flow Measurements ◽  
Radiogenic Heat ◽  
Radiogenic Heat Production ◽  
Climatic Variations ◽  
The Mean ◽  
A Site

Borehole heat-flow measurements are reported from six new sites in the Superior Province of the Canadian Shield. Values adjusted for glaciation effects, but not for Holocene climatic variations, range from 42 to 56 mW/m2. When these new values are combined with 21 previously published borehole values the mean is 42 mW/m2 with a standard deviation of 11 mW/m2. The data for a site on the Lac du Bonnet batholith suggest that the batholith has a thin veneer, less than 3 km, of rock of high radiogenic heat production at the surface.

Paleomagnetism of the 1.1 Ga Lackner Lake Complex and tectonics of the Kapuskasing Structural Zone

1989 ◽  
Vol 26 (9) ◽  
pp. 1778-1783 ◽  
Author(s):  
D. T. A. Symons
Keyword(s):  
Fault Zone ◽  
Canadian Shield ◽  
Superior Province ◽  
Thermal Demagnetization ◽  
Abitibi Subprovince ◽  
Reversed Polarity ◽  
Middle Proterozoic

The Middle Proterozoic Lackner Lake Complex is a circular alkalic syenite–carbonatite stock with a diameter of about 5.5 km. It intrudes granulite-rank Archean gneisses in the Kapuskasing Structural Zone of the Wawa Subprovince in the Superior Province of the Canadian Shield. It adjoins the Ivanhoe Lake fault zone, which forms the boundary with the Abitibi Subprovince and is the probable locus of maximum motion between the subprovinces. Specimens from 18 sites in the complex were analyzed paleomagnetically by alternating-field and thermal demagnetization and by saturation isothermal remanence tests. Large, recent viscous remanence components required removal before a stable remanence with a mean direction of 305.4°, 64.1 °(α95 = 5.2°) was isolated. Its pole of 53.7°N, 156.5°W (dp = 6.7°, dm = 8.3°) indicates emplacement at 1108 ± 10 Ma during a brief normal interval in a predominantly reversed-polarity time. This study indicates that there has been no postintrusion tilting of the Kapuskasing Structural Zone and that postintrusion uplift by unroofing did not exceed about 8 km.

A detailed 40Ar/39Ar age study of an Abitibi dike from the Canadian Superior Province

1979 ◽  
Vol 16 (5) ◽  
pp. 1060-1070 ◽  
Author(s):  
J. A. Hanes ◽  
Derek York
Keyword(s):  
Canadian Shield ◽  
Superior Province ◽  
Low Grade ◽  
Polar Wander ◽  
Mafic Mineral ◽  
Fine Grained ◽  
Apparent Polar Wander Path ◽  
Step Heating ◽  
Apparent Age ◽  
Hydrothermal Event

40Ar/39Ar step-heating analyses were performed on 11 felsic and mafic mineral separates from a 90 m wide Precambrian diabase dike of the Abitibi swarm in the Superior Province of the Canadian Shield. Deuterically altered minerals from the dike interior define a primary age of 2150 ± 25 Ma. Updated ages, obtained from felsic separates within 30, and mafic within 1.5 m of the dike border, are evidence of a previously undetected 'Hudsonian' (1.7–1.8 Ga) hydrothermal event in the area. It is possible to distinguish the deuteric from the later hydrothermal alteration by both dating and petrographic methods. The data from this study demonstrate the successful application of 40Ar/39Ar dating to early Proterozoic dikes which have suffered low grade metamorphism. The ages support a north to south sense of motion of the Track 5 apparent polar wander path (APWP). A monotonic decrease in apparent age of felsic spectra indicates reactor induced recoil effects which are correlated with the fine-grained saussurite in the feldspar.

Rare earth distribution in Archean granitoid plutons of the Wabigoon volcanic–plutonic belt, northwestern Ontario

1979 ◽  
Vol 16 (2) ◽  
pp. 270-289 ◽  
Author(s):  
Dieter Birk ◽  
Tapio Koljonen ◽  
R. J. Rosenberg
Keyword(s):  
Rare Earth ◽  
Steep Slope ◽  
Canadian Shield ◽  
Secular Change ◽  
Source Modeling ◽  
Northwestern Ontario ◽  
History Of ◽  
Plutonic Belt ◽  
High Concentrations ◽  
Ree Patterns

Rare earths (La to Lu, Y) are investigated for five Archean granitoid stocks of Kenoran age that intrude the Wabigoon volcanic–plutonic belt. Homogeneous granodiorites are characterized by low total rare earth concentrations (ΣREE), with chondrite-normalized REE patterns that show steep negative slopes, no Eu anomalies, and enrichment of Lu. A hypabyssal porphyry of possible volcanic affiliation displays similar REE patterns, but is more depleted in heavy REE. Zone plutons yield patterns of steep slope, no Eu anomalies, with or without Lu enrichment. REE concentrations decrease from monzodioritic margins, to granodioritic cores, to aplitic apophyses.These plutons carry REE concentrations similar to the Canadian Shield average, but notably lower than some published averages for granitoids. No secular change is evident for the Archean interval.ΣREE decreases during differentiation with no appreciable fractionation of heavy over light REE, until the end stages. Late differentiates suffer depletion in heavy REE by hornblende fractionation. Lu enrichment correlates with deuteric metasomatism, as evidenced by microcline megacrysts. Eu anomalies are absent because fractionation of divalent Eu is prevented by high concentrations of Sr and Ba.Quantitative source modeling should consider the complete magma history of emplacement, crystallization, and deuteric metasomatism.

ERRATUM: AN ESTIMATE OF THE COMPOSITION OF PART OF THE CANADIAN SHIELD IN NORTHWESTERN ONTARIO

1967 ◽  
Vol 4 (6) ◽  
pp. 1269-1269
Author(s):  
G. A. Reilly ◽  
D. M. Shaw
Keyword(s):  
Canadian Shield ◽  
Northwestern Ontario
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