Regional magnetic anomalies, magnetic units, and crustal structure in the Kenora District of Ontario

1968 ◽  
Vol 5 (5) ◽  
pp. 1277-1296 ◽  
Author(s):  
Donald H. Hall
Keyword(s):  
Magnetic Susceptibility ◽  
Crustal Structure ◽  
Continuous Distribution ◽  
Magnetic Anomalies ◽  
Canadian Shield ◽  
Superior Province ◽  
Quantitative Interpretation ◽  
Variable Intensity ◽  
Depth Determination ◽  
Greenstone Belts

Regional magnetic anomalies were smoothed from aeromagnetic maps in a part of the Superior Province of the Canadian Shield (latitudes 48°45′ to 50°00′ N; longitudes 93°30′ to 95°00′ W). It was found that anomaly lows lie over Keewatin greenstone belts, and highs over adjacent granitic areas.Surface mapping of magnetic susceptibility and NRM was combined with quantitative interpretation of the regional magnetic anomalies. It was found that, when considered regionally, magnetization lies primarily in the granitic bodies, with a continuous distribution from the surface down to the Intermediate (Conrad) discontinuity. Intensity of magnetization increases with depth, and is directed nearly along the direction of the present-day geomagnetic field.As an aid to the interpretation, a method of depth determination for deep crustal magnetic units with sloping sides is introduced, and one for variable intensity of magnetization with depth.

Central Superior Province geology: evidence for an allochthonous, ensimatic, southern Abitibi greenstone belt

1990 ◽  
Vol 27 (4) ◽  
pp. 582-589 ◽  
Author(s):  
S. L. Jackson ◽  
R. H. Sutcliffe
Keyword(s):  
Crustal Structure ◽  
Greenstone Belt ◽  
Superior Province ◽  
Low Grade ◽  
Simple Correlation ◽  
Abitibi Greenstone Belt ◽  
Structural Style ◽  
Metavolcanic Rocks ◽  
Crustal Model ◽  
Greenstone Belts

Published U–Pb geochronological, geological, and petrochemical data suggest that there are late Archean ensialic greenstone belts (GB) (Michipicoten GB and possibly the northern Abitibi GB), ensimatic greenstone belts (southern Abitibi GB and Batchawana GB), and possibly a transitional ensimatic–ensialic greenstone belt (Swayze GB) in the central Superior Province. This lateral crustal variability may preclude simple correlation of the Michipicoten GB and its substrata, as exposed in the Kapuskasing Uplift, with that of the southern Abitibi GB. Furthermore, this lateral variability may have determined the locus of the Kapuskasing Uplift. Therefore, although the Kapuskasing Uplift provides a useful general crustal model, alternative models of crustal structure and tectonics for the southern Abitibi GB warrant examination.Thrusting of a juvenile, ensimatic southern Abitibi GB over a terrane containing evolved crust is consistent with (i) the structural style of the southern Abitibi GB; (ii) juvenile southern Abitibi GB metavolcanic rocks intruded by rocks having an isotopically evolved, older component; and (iii) Proterozoic extension that preserved low-grade metavolcanic rocks within the down-dropped Cobalt Embayment, which is bounded by higher grade terranes to the east and west.

scholarly journals Contribution of applied geophysics in mining prospecting

2020 ◽  
Vol 150 ◽  
pp. 03016
Author(s):  
Meryeme El Abidi El Alaoui ◽  
Latifa Ouadif ◽  
Lahcen Bahi ◽  
Ahmed Manar
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
Deep Structure ◽  
Magnetic Anomalies ◽  
High Amplitude ◽  
Quantitative Interpretation ◽  
High Atlas ◽  
Residual Magnetic Field ◽  
Reduction To The Pole ◽  
Geological Formations

The Eastern High Atlas (Morocco) contains a variety of rocks with different magnetic susceptibility, among these rocks are those which constitute the Proterozoic and Paleozoic basement of the plain of Tamlelt which is the study area. This work is devoted to the analysis and interpretation of the main magnetic anomalies using the Oisis Montaj program, and the correlation using ArcGis software, from the main « magnetic facies» detected, to the main geological formations affecting the geological basement, highlighted in the plain of Tamlelt. The map of the residual magnetic field shows elongated magnetic anomalies in the direction E-W and NE-SW. the reduction to the pole shows at the level of the plain of Tamlelt a large anomaly elongated in the direction E-W then in the direction NW-SE. The transformation of Tilt Angle allowed to delimit the anomalies of low or high amplitude that limit the shallow structures. The quantitative interpretation of the main magnetic anomalies highlighted in the study area has made it possible to characterize the deep structure of the magnetic bodies, which could contain sulphide clusters, according to the geological and mining context of the studied area.

Rubidium–strontium ages from the Oxford Lake – Knee Lake greenstone belt, northern Manitoba

1980 ◽  
Vol 17 (5) ◽  
pp. 560-568 ◽  
Author(s):  
G. S. Clark ◽  
S.-P. Cheung
Keyword(s):  
Greenstone Belt ◽  
Volcanic Rocks ◽  
Superior Province ◽  
Granitic Intrusion ◽  
Greenstone Belts ◽  
Archean Greenstone Belts

Rb–Sr whole-rock ages have been determined for rocks from the Oxford Lake – Knee Lake – Gods Lake greenstone belt, in the Superior Province of northeastern Manitoba.The age of the Magill Lake Pluton is 2455 ± 35 Ma (λ87Rb = 1.42 × 10−11 yr−1), with an initial 87Sr/86Sr ratio of 0.7078 ± 0.0043. This granitic stock intrudes the Oxford Lake Group, so it is post-tectonic and probably related to the second, weaker stage of metamorphism.The age of the Bayly Lake Pluton is 2424 ± 74 Ma, with an initial 87Sr/86Sr ratio of 0.7029 ± 0.0001. This granodioritic batholith complex does not intrude the Oxford Lake Group. It is syn-tectonic and metamorphosed.The age of volcanic rocks of the Hayes River Group, from Goose Lake (30 km south of Gods Lake Narrows), is 2680 ± 125 Ma, with an initial 87Sr/86Sr ratio of 0.7014 ± 0.0009.The age for the Magill Lake and Bayly Lake Plutons can be interpreted as the minimum ages of granitic intrusion in the area.The age for the Hayes River Group volcanic rocks is consistent with Rb–Sr ages of volcanic rocks from other Archean greenstone belts within the northwestern Superior Province.

Magmatic and tectonic emplacement of the Pukaskwa batholith, Superior Province, Ontario, CanadaThis 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. 187-204 ◽  
Author(s):  
Gary P. Beakhouse ◽  
Shoufa Lin ◽  
Sandra L. Kamo
Keyword(s):  
Partial Melting ◽  
Abrupt Change ◽  
Superior Province ◽  
Density Inversion ◽  
Tectonic Processes ◽  
Slab Breakoff ◽  
Greenstone Belts ◽  
Lower Crustal ◽  
Basaltic Crust ◽  
Structural Dome

The Neoarchean Pukaskwa batholith consists of pre-, syn-, and post-tectonic phases emplaced over an interval of 50 million years. Pre-tectonic phases are broadly synvolcanic and have a high-Al tonalite–trondhjemite–granodiorite (TTG) affinity interpreted to reflect derivation by partial melting of basaltic crust at lower crustal or upper mantle depths. Minor syn-tectonic phases slightly post-date volcanism and have geochemical characteristics suggesting some involvement or interaction with an ultramafic (mantle) source component. Magmatic emplacement of pre- and syn-tectonic phases occurred in the midcrust at paleopressures of 550–600 MPa and these components of the batholith are thought to be representative of the midcrust underlying greenstone belts during their development. Subsequent to emplacement of the syntectonic phases, and likely at approximately 2680 Ma, the Pukaskwa batholith was uplifted as a structural dome relative to flanking greenstone belts synchronously with ongoing regional sinistral transpressive deformation. The driving force for vertical tectonism is interpreted to be density inversion (Rayleigh–Taylor-type instabilities) involving denser greenstone belts and underlying felsic plutonic crust. The trigger for initiation of this process is interpreted to be an abrupt change in the rheology of the midcrust attributed to introduction of heat from the mantle attendant with slab breakoff or lithospheric delamination following the cessation of subduction. This process also led to partial melting of the intermediate to felsic midcrust generating post-tectonic granitic phases at approximately 2667 Ma. We propose that late density inversion-driven vertical tectonics is an inevitable consequence of horizontal (plate) tectonic processes associated with greenstone belt development within the Superior Province.

A New Algorithm for Depth Determination from Total Magnetic Anomalies due to Spheres

2008 ◽  
Vol 165 (5) ◽  
pp. 967-979 ◽  
Author(s):  
E. M. Abdelrahman ◽  
T. M. El-Araby ◽  
E. R. Abo-Ezz ◽  
K. S. Soliman ◽  
K. S. Essa
Keyword(s):  
Magnetic Anomalies ◽  
Depth Determination

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.

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