Nd evidence for extensive Archean basement in the western Churchill Province, Canada

1986 ◽  
Vol 23 (9) ◽  
pp. 1433-1437 ◽  
Author(s):  
C. D. Frost ◽  
R. A. Burwash
Keyword(s):  
Drill Hole ◽  
Crust Formation ◽  
Southern Alberta ◽  
Northern Saskatchewan ◽  
Archean Crust ◽  
Northeastern Alberta ◽  
Archean Basement

To determine the extent of reworked Archean crust in the western Churchill Province, we have examined Sm–Nd crustal residence ages of basement cores in southern Alberta and southwestern Saskatchewan along with crustal residence ages calculated for other Sm–Nd data available from the Churchill Province. The deep drill hole samples from the Interior Platform give Sm–Nd crustal residence ages that average 2.8 Ga. Granulites from northeastern Alberta and composite gneisses from northern Saskatchewan also provide Archean crustal residence ages. These data demonstrate that the presence of reworked Archean crust in the western Churchill Province is more widespread than has been confirmed previously. We suggest that Sm–Nd crustal residence ages are valuable estimates of crust formation times, especially in orogenic areas where other isotope systems have been disturbed.

Rb–Sr study of metavolcanic rocks from the La Ronge and Flin Flon domains, northern Saskatchewan

1985 ◽  
Vol 22 (3) ◽  
pp. 452-463 ◽  
Author(s):  
B. R. Watters ◽  
R. L. Armstrong
Keyword(s):  
Source Region ◽  
Volcanic Rocks ◽  
Volcanic Arcs ◽  
Magmatic Arc ◽  
Linear Evolution ◽  
Metavolcanic Rocks ◽  
Northern Saskatchewan ◽  
Archean Crust ◽  
Flin Flon ◽  
Lynn Lake

Two whole-rock suites of metavolcanic rocks from separate volcanic belts of the Churchill Province in northern Saskatchewan have been dated by Rb–Sr. Samples from the Amisk Group of the Flin Flon – Snow Lake domain provide an isochron date of 1784 ± 44 Ma; suites from the Waddy Lake and Devil Lake areas of the La Ronge (–Lynn Lake) domain yield isochron dates of 1814 ± 26 and 1854 ± 100 Ma, respectively. All are regarded as minima for, but close approximations to, emplacement ages. The maximum crustal age of any suite cannot greatly exceed 1850 Ma.Previous Rb–Sr and U–Pb isotopic dates together with these new determinations confirm the contemporaneous existence of two volcanic arcs, active during the late Aphebian (1875–1784 Ma) in the Churchill Province.Low initial 87Sr/86Sr ratios (0.7017–0.7022) are consistent with a petrochemically inferred subduction-related origin for the volcanic rocks with no closed-system reworking of Archean crust, and a linear evolution of 87Sr/86Sr ratio in the magmatic-arc mantle source region from 4.55 Ga to the present.

Striding-Athabasca mylonite zone: implications for the Archean and Early Proterozoic tectonics of the western Canadian Shield

1995 ◽  
Vol 32 (2) ◽  
pp. 178-196 ◽  
Author(s):  
Simon Hanmer ◽  
Michael Williams ◽  
Chris Kopf
Keyword(s):  
Continental Margin ◽  
Canadian Shield ◽  
Magmatic Evolution ◽  
Tectonic Zone ◽  
Early Proterozoic ◽  
Plate Margin ◽  
Mylonite Zone ◽  
Northern Saskatchewan ◽  
Archean Crust ◽  
Rifted Margin

Study of the northern Saskatchewan–District of Mackenzie segment of the Snowbird tectonic zone suggests that fragments of relatively stiff mid-Archean crust, possibly arc related, have controlled the localization, shape, and complex kinematics of the multistage Striding–Athabasca mylonite zone during the Archean, as well as the geometry of the Early Proterozoic rifted margin of the western Churchill continent. By the late Archean, the Striding–Athabasca mylonite zone was located in the interior of the western Churchill continent, well removed from the contemporaneous plate margins. Except for the Alberta segment, the Snowbird tectonic zone was not the site of an Early Proterozoic plate margin. We suggest that the geometry of the Archean–Early Proterozoic boundary in the western Canadian Shield represents a jagged continental margin, composed of a pair of reentrants defined by rifted and transform segments. These segments were inherited from Early Proterozoic breakup and controlled by the Archean structure of the interior of the western Churchill continent. The geometry of this margin appears to have strongly influenced the Early Proterozoic tectono-magmatic evolution of the western Canadian Shield.

The geochronology of the granitic rocks along the Bear–Slave Structural Province boundary, northwest Canadian Shield

1977 ◽  
Vol 14 (6) ◽  
pp. 1356-1373 ◽  
Author(s):  
Rosaline Frith ◽  
R. A. Frith ◽  
R. Doig
Keyword(s):  
Age Groups ◽  
Canadian Shield ◽  
Granitic Rocks ◽  
Thermal Event ◽  
Slave Province ◽  
Fault Block ◽  
Granitic Intrusions ◽  
Main Period ◽  
Archean Crust ◽  
Archean Basement

Archean granitic rocks along the southern Bear–Slave boundary fall into three age groups: the oldest are 3000 Ma old intrusive tonalites and granodiorites that form the basement to the Yellowknife Supergroup; the second are syn-volcanic granitic intrusions of ~ 2700 Ma; and the youngest are ~ 2560 Ma granitic and migmatitic diapirs formed in part from supracrustal and granitic rocks. Two Proterozoic thermal events are recognized within the Slave Province. A ~ 2300 Ma event may be related to early rift breakup of the Archean crust and is recorded in Rb–Sr whole-rock and K–Ar mineral systems. A ~ 1970 Ma event was less intense but may be related to further rifting of the Archean and to fault-block depression of the Indin Lake supracrustal basin, the intrusion of a group of granodioritic stocks, and the formation or granitic pegmatite.Within the Bear Province, evidence of a ~ 2700 Ma intrusive event and a ~ 2300 Ma thermal event are preserved in Rb–Sr whole rock systems. Practically all the granitic rocks of the Bear Province, including the Hepburn batholitic rocks, are thought to have been derived wholly or partly from Archean rocks. The main period of Hudsonian deformation and metamorphism was accompanied by a diapiric remobilization of the Archean basement about 1800 Ma ago. Twelve Rb–Sr isochrons, as well as other published geochronologic data from the region, support these conclusions.

Stratigraphic variations in carbon and oxygen isotopes in the dolostone of the Carswell Formation (Proterozoic) of northern Saskatchewan

1989 ◽  
Vol 26 (11) ◽  
pp. 2318-2326 ◽  
Author(s):  
P. I. Abell ◽  
J. McClory ◽  
H. E. Hendry ◽  
K. L. Wheatley
Keyword(s):  
Oxygen Isotope ◽  
Isotope Ratios ◽  
Drill Hole ◽  
Carbon And Oxygen Isotopes ◽  
Oxygen Isotope Ratios ◽  
Nearshore Environments ◽  
Carbon And Oxygen Isotope ◽  
Isotopic Analyses ◽  
Northern Saskatchewan ◽  
Lowermost Part

Petrographic and stable isotopic analyses of stromatolitic sediments deposited in nearshore environments provides us with some of the best information available on ancient environments. Diamond drill hole CAR 58 penetrated 110 m of sediments in the lowermost part of the Proterozoic (probably Helikian age) Carswell Formation of northern Saskatchewan and gave us such an opportunity. The rocks are mainly dolostone and include, in descending order of abundance, cyanobacterial laminites, stromatolites, dolomicrites, dolorudites, breccias, and oolites. Stromatolites and Cyanobacterial laminites increase in abundance up-section, and deposition is interpreted as having taken place in conditions of increasingly restricted water circulation through time. The carbon isotope ratios vary from about −0.5 to −1.5‰ (Pee Dee Belemnite (PDB)) in the section except near the base where they assume values near −2.5‰. The oxygen isotope ratios (vs. PDB) increase from about −9.3‰ at the base to −7‰ at the top, with anomolously high values, more positive than −7‰, at two positions in the sequence. Original depositional structures and textures are still visible in most of the rocks, but gypsum has been replaced by dolomite, there has been some silicification, and original features have been obliterated by dolomite rhombs in a few samples. The upward trend to less-negative values of the oxygen isotope ratios is interpreted in terms of changing depositional environment involving a deepening but more protected basin, with increased evaporational concentration of the heavier isotope. Scatter diagrams of carbon and oxygen isotope ratios place the Carswell Formation dolomites close to the mainstream of other Proterozoic stromatolites but indicating some evaporative alterations during deposition.

Constraints on Archean crust formation from open system models of Earth evolution

2019 ◽  
Vol 530 ◽  
pp. 119307 ◽  
Author(s):  
Seema Kumari ◽  
Debajyoti Paul ◽  
Andreas Stracke
Keyword(s):  
Open System ◽  
Crust Formation ◽  
System Models ◽  
Archean Crust

U–Pb geochronology in the Trans-Hudson Orogen, northern Saskatchewan, Canada

1987 ◽  
Vol 24 (3) ◽  
pp. 407-424 ◽  
Author(s):  
W. R. Van Schmus ◽  
M. E. Bickford ◽  
J. F. Lewry ◽  
R. Macdonald
Keyword(s):  
Granitic Rocks ◽  
Early Proterozoic ◽  
Tectonic Events ◽  
Northern Saskatchewan ◽  
High Grade Metamorphism ◽  
The One ◽  
Relationship Of ◽  
The Relationship ◽  
Orogenic Events ◽  
Archean Basement

We have obtained U–Pb ages on zircons from volcanic and plutonic units in several lithotectonic domains of the southern Trans-Hudson Orogen in northern Saskatchewan. These data constrain the timing of early Proterozoic orogenic events in the region and enhance our understanding of both the relationships among local domains and the relationship of the Trans-Hudson Orogen to other early Proterozoic orogens in North America.With one exception, all units studied so far yield zircon ages of 1890–1835 Ma, most of which are systematically earlier than previously reported Rb–Sr isochron ages on the same or similar units, suggesting open-system behavior in the Rb–Sr systems. Five metarhyolites, from volcanic sequences in the La Ronge domain, Glennie domain, and Hanson Lake block, give ages ranging from 1888 to 1876 Ma. Most of the plutons we dated, ranging from gneissic syntectonic tonalites and granodiorites to less-deformed late intrusions such as the Wathaman batholith and other smaller bodies, yield ages of 1870–1850 Ma, apparently constraining peak plutonic activity to about 1860 ± 10 Ma ago. The youngest unit found is a small discordant pluton with an age of 1836 ± 7 Ma. The concordance of ages of volcanics on the one hand and of plutons on the other suggests that domainal distinctions are mainly lithotectonic rather than temporal.Zircons from the Sahli charnockitic granite in the Hanson Lake block yield equivocal results. Discordia upper and lower intercepts for the Sahli granite suggest that granitic rocks at least 2500 Ma old were subjected to high-grade metamorphism about 1800–1900 Ma ago, with substantial resetting of zircons. Reworked Archean basement is thus present in this domain, supporting previously reported Rb–Sr isochron data from the Sahli granite. No other indications of Archean basement in the Trans-Hudson Orogen are documented, although one sample from the adjacent Peter Lake domain shows that it consists of Archean continental crust.Zircon ages in the range 1890–1835 Ma from this part of the Trans-Hudson Orogen are similar to those obtained from igneous units of the Penokean and Wopmay orogens, in North America, and from the Svecofennian Orogen, suggesting essential synchroneity of igneous and tectonic events in these four major orogens during major Proterozoic continental assembly.

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