Regional mapping of Precambrian basement beneath Phanerozoic cover in southeastern Trans-Hudson Orogen, Manitoba and Saskatchewan

1997 ◽  
Vol 34 (5) ◽  
pp. 618-634 ◽  
Author(s):  
A. D. Leclair ◽  
S. B. Lucas ◽  
H. J. Broome ◽  
D. W. Viljoen ◽  
W. Weber
Keyword(s):  
Gravity Data ◽  
Regional Mapping ◽  
Western Canada Sedimentary Basin ◽  
Gneiss Complex ◽  
Intrusive Rocks ◽  
Anomaly Pattern ◽  
Northern Edge ◽  
Flin Flon ◽  
Seismic Reflection Profiles ◽  
Canada Sedimentary Basin

The northern edge of Phanerozoic platformal rocks of the Western Canada Sedimentary Basin overlies the Flin Flon Belt (Trans-Hudson Orogen) in Manitoba and Saskatchewan. A program of regional mapping of the Phanerozoic-covered basement has been undertaken, involving the integration of high-resolution aeromagnetic and gravity data with extensive drill core information. Several major domains are recognized in the buried basement, each with a distinct lithotectonic character and potential field anomaly pattern. Three lithotectonic domains in the buried basement (Clearwater, Athapapuskow, and Amisk Lake domains) are characterized by northerly-trending positive gravity and aeromagnetic anomalies and correlate with the 1.92–1.83 Ga volcanic and plutonic rocks of the exposed Flin Flon Belt (Amisk collage and Snow Lake assemblage). An upper amphibolite grade orthogneiss complex (Namew Gneiss Complex), containing calc-alkaline intrusive rocks ranging in age from 1.88 to 1.83 Ga and screens derived from the older volcano-sedimentary rocks, is interpreted as the middle crust of a 1.88–1.84 Ga arc exposed in the Flin Flon Belt. Discordant intrusive complexes, such as the 1.830 Ga Cormorant Batholith, are centred on magnetic–gravity lows and truncate the structural trend of adjacent lithotectonic domains. Correlation of Flin Flon Belt geology with that beneath the Phanerozoic cover shows that its constituent lithotectonic elements have north–south strikes of up to 150 km, and form a predominantly east-dipping crustal section, consistent with Lithoprobe seismic reflection profiles.

The edge of northwestern North America at ∼1.8 Ga

2005 ◽  
Vol 42 (6) ◽  
pp. 983-997 ◽  
Author(s):  
Frederick A Cook ◽  
Kevin W Hall ◽  
C Elissa Lynn
Keyword(s):  
Gravity Anomalies ◽  
Western Canada Sedimentary Basin ◽  
Bear Lake ◽  
Lithospheric Extension ◽  
Isostatic Gravity Anomalies ◽  
Isostatic Gravity ◽  
North American Craton ◽  
Seismic Reflection Profiles ◽  
Northwestern North America ◽  
Canada Sedimentary Basin

The ∼1.80 Ga edge of the northwestern North American craton is buried beneath Phanerozoic and Proterozoic rocks of the Western Canada Sedimentary Basin and the adjacent Cordillera. It is visible in more than eight deep seismic reflection profiles that have images of west-facing crustal-scale monoclines with up to 15–20 km of vertical relief, and it produces regional isostatic gravity anomalies that can be followed for more than 1500 km along strike. The deep reflection profiles include two major transects of Lithoprobe (southern Canadian Cordillera transect and Slave – Northern Cordillera Lithospheric Evolution (SNORCLE) transect) and industry profiles that are strategically located to provide depth and geometry constraints on the monoclines. The isostatic anomalies mark the density transition from Paleoproterozoic and older crystalline rocks of the Canadian Shield to less dense supracrustal rocks of westward-thickening late Paleo proterozoic and younger strata. These gravity anomaly patterns thus provide areal geometry of crustal structure variations along strike away from the depth control provided by the seismic data. Although many of the monoclines follow the Fort Simpson geophysical trend along the Cordilleran deformation front, isostatic anomalies near Great Bear Lake delineate a northeast-striking region of low values that may coincide with a failed rift arm or the southern margin of a large basin. The monoclines are interpreted as a series of en echelon structures that probably formed as a result of lithospheric extension at about 1.80–1.70 Ga following terminal accretion of the Paleoproterozoic Wopmay Orogen.

Geoelectric response and crustal electrical-conductivity structure of the Flin Flon Belt, Trans-Hudson Orogen, Canada

1999 ◽  
Vol 36 (11) ◽  
pp. 1917-1938 ◽  
Author(s):  
I J Ferguson ◽  
Alan G Jones ◽  
Yu Sheng ◽  
X Wu ◽  
I Shiozaki
Keyword(s):  
Geological Structure ◽  
The Body ◽  
Geomagnetic Induction ◽  
The North ◽  
Gneiss Complex ◽  
Conductivity Structure ◽  
Intrusive Rocks ◽  
Magnetotelluric Method ◽  
Flin Flon ◽  
Southern Flank

A Lithoprobe magnetotelluric survey across the Palaeoproterozoic Trans-Hudson Orogen included 34 sites within the Flin Flon Belt and adjacent geological domains. The magnetotelluric impedance tensors and geomagnetic induction vectors reveal four distinct geoelectric zones along this segment of the Lithoprobe transect. In the east and west, the geoelectric responses are dominated by the contrast between intrusive rocks and more conductive ocean-floor assemblages. A significant characteristic of the responses throughout the Flin Flon Belt is the very strong galvanic distortion of the electric field, which reflects the complexity of the upper crustal geological structure in the greenstone belt, requiring careful application of distortion removal methods. The responses at sites near the north of the Flin Flon Belt are related to the boundary with the southern flank of the Kisseynew gneiss belt. To the south, at sites near Athapapuskow Lake, the responses are dominated by a strong upper-crustal conductor. The magnetotelluric observations show that the Athapapuskow Lake conductivity anomaly extends for at least 40 km along strike (~N36°E), and is roughly two-dimensional in form. Numerical modelling shows that the top of the body dips southeast at 20-50° from a western edge coincident with the Athapapuskow Lake shear zone. The conductor lies in the eastern part of the Namew gneiss complex. The magnetotelluric method cannot resolve the exact spatial distribution of conductive rocks but it is probable that the anomaly is caused by a series of isolated conductors (with resistivity <1 Ω·m) associated with subordinate graphitic and sulphidic supracrustal gneisses.

Potential-field signatures of buried Precambrian basement in the Western Canada Sedimentary Basin

2000 ◽  
Vol 37 (11) ◽  
pp. 1453-1471 ◽  
Author(s):  
M Pilkington ◽  
W F Miles ◽  
G M Ross ◽  
W R Roest
Keyword(s):  
Sedimentary Basin ◽  
Gravity Data ◽  
Magnetic Data ◽  
Western Canada ◽  
Precambrian Basement ◽  
Western Canada Sedimentary Basin ◽  
Magmatic Arc ◽  
Magnetic Source ◽  
Definition Of ◽  
Canada Sedimentary Basin

An internally consistent, levelled compilation of magnetic data is derived for Alberta and northeastern British Columbia. With Bouguer gravity data, this compilation is used to refine the definition of Precambrian basement domains within the Western Canada Sedimentary Basin. Magnetic data are draped at a constant distance above the mapped basement surface to reduce the effects of varying magnetic source depths. Automated interpretation methods that effectively map outlines of magnetic sources are used to characterize the internal structure of the domains and to aid in their delineation. The basement domain map thus derived differs from previous interpretations in the extension of domains further to the southwest, due mainly to the availability of new public-domain magnetic data and the more precise definition of domain boundaries, based on the magnetic source location maps. The Nahanni, Hottah, Chinchaga, Thorsby, Vulcan, and Kiskatinaw domains are weakly magnetic and characterized by magnetic sources that are paramagnetic, comprising low-susceptibility silicate minerals. All other domains are characterized by the presence of ferrimagnetic material, most likely magnetite, which has a sufficiently high susceptibility to produce measurable anomalies. The largest anomalies and magnetizations are found in the Fort Nelson, Fort Simpson, Buffalo Head, Talston, Ksituan, and Matzhiwin domains. Such large magnetizations are usually indicative of intermediate igneous rocks associated with magmatic arc environments. Moderate-amplitude anomalies and (or) magnetizations are characteristic of the Nova, Wabamun, Lacombe, Rimbey, Loverna, and Medicine Hat domains, suggesting the presence of ferrimagnetic basic and granitoid rocks. Within some of the moderately magnetic domains are areas of paramagnetic lithologies that produce no magnetic anomalies. The narrower regions of magnetic lows, such as the Thorsby, Kiskatinaw, and Vulcan domains, are interpreted as resulting from demagnetization effects accompanying collision. Since demagnetization zones are limited in areal extent, the wider, more extensive magnetic lows of the Chinchaga and Hottah domains likely result from a combination of boundary demagnetization and a lower bulk magnetization level of crustal lithologies present.

Hydraulic Fracturing and Seismicity in the Western Canada Sedimentary Basin

2016 ◽  
Vol 87 (3) ◽  
pp. 631-647 ◽  
Author(s):  
Gail M. Atkinson ◽  
David W. Eaton ◽  
Hadi Ghofrani ◽  
Dan Walker ◽  
Burns Cheadle ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Sedimentary Basin ◽  
Western Canada ◽  
Western Canada Sedimentary Basin ◽  
Canada Sedimentary Basin

scholarly journals Geology of the Mesoproterozoic Pillar Lake Volcanics and Inspiration Sill, Armstrong, Ontario: Evidence of Early Midcontinent Rift Magmatism in the Northwestern Nipigon Embayment

2021 ◽  
Author(s):  
Pete Hollings ◽  
Mark Smyk ◽  
Wouter Bleeker ◽  
Michael A. Hamilton ◽  
Robert Cundari ◽  
...  
Keyword(s):  
North America ◽  
Direct Contact ◽  
Large Igneous Province ◽  
Rift System ◽  
Flood Basalts ◽  
Midcontinent Rift ◽  
Igneous Province ◽  
Intrusive Rocks ◽  
Midcontinent Rift System ◽  
Northern Edge

The Midcontinent Rift System of North America is a ~1.1 Ga large igneous province comprising mainly flood basalts and intrusive rocks. We present new data for the Pillar Lake Volcanics and Inspiration Sill from the northern edge of the Midcontinent Rift in the northwestern Nipigon Embayment. The Pillar Lake Volcanics comprise a ~20-40 m-thick, flat-lying sequence of mafic pillowed and massive flows, pillowed flow breccia, and hyaloclastite breccia. They are characterized by SiO2 of 52-54 wt%, TiO2 of 1.2 to 1.3 wt% and K2O of 0.9 to 1.1 wt%. They are LREE-enriched, with La/Smn of 3.0 to 4.4 with fractionated HREE (Gd/Ybn = 1.4 to 1.7). The Inspiration diabase sill is < 50 m thick and is in direct contact with the underlying Pillar Lake Volcanics. Baddeleyite and zircon data from the Inspiration Sill yield a combined U-Pb upper intercept age of 1105.6 ± 1.6 Ma. The Inspiration Sill is characterized by uniform SiO2 of 52 to 53 wt%, TiO2 of 1.1 to 1.2 and K2O of 0.9 to 1.2 wt%. Inspiration Sill samples are LREE enriched with La/Smn of 3.2 to 3.3 and fractionated HREE of (Gd/Ybn = 1.6). The Pillar Lake Volcanics are at least 1120 Ma, and perhaps as old as 1130 Ma and represent an early, thin, and restricted mafic volcanic sequence, largely preserved below the younger Inspiration Sill. The Pillar Lake Volcanics and Inspiration Sill display a marked geochemical similarity, suggesting that they may represent magmatism associated with the earliest stages of Midcontinent rifting.

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