Volume 1, numéro 3, august 1974

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At this time the oldest rocks on Earth occur in W. Greenland. Radioactive dating methods give ages of about 3.8 billion years. The rock types involved are a complex mixture of metasediments, metavolcanic and intrusive rocks. The rock types appear to be rather normal in terms of modern analogues. But the structural geology of this, and similar ancient regions, indicates that ancient tectonic patterns may be unique. It is suggested that differentiation of the Earth was advanced 4 billion years ago and that there was an extensive acid crust.

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This paper is a progress report concerning some of the research being conducted at the Centre for Precambrian Studies at the University of Manitoba. The research has led to a hypothesis that stable Archean continental nucleii originated during a period of large scale melting, volcanism, and intrusion. The paper describes the work leading to the hypothesis as well as on-going field and analytical results which test the hypothesis. The hypothesis leads to the suggestion that the planetary development of the earth may have major features in common with that of the moon and other planets, but differences in development are caused by gravity differences and the early presence of abundant water on the earth.

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The Superior Geotraverse Project is a cooperative geological and geophysical research program being carried out by the Precambrian Research Group of the University of Toronto, assisted by scientists from other universities. The purpose of the project is to study the origin of the Archean crust north of Lake Superior in a 300 mile long, N-S corridor which crosses three volcanic-plutonic belts (Uchi, Wabigoon and Shebandowan) and two metasedimentary-gneiss belts (English River and Quetico).

Six different models for the origin of the Archean crust are under consideration: no decision between competing models will be possible until further work is done. One possible model, however, is that the crust developed in three stages: 1 ) development of Archean "oceanic" crust, 2) development of Archean "island arc" crust as a result of subduction, 3) accumulation of greywackes in foreland basins.

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Although economic development has initiated more geological work in the Flin Flon area than any other part of the Precambrian Shield in Saskatchewan, it is only recently that the detailed geological, geophysical, and geochemical work necessary to gain a firm understanding of the area has begun. The results of this work are far from conclusive at present. However, a tentative geotectonic setting can be interpreted for the development of the area.

During Aphebian time, the Amisk Group of volcanic rocks were deposited as an island-arc complex. Continued closure of the Aphebian "Churchill Ocean" and concomitant subduction zone processes resulted in intrusion, uplift, and formation of the Missi Group of coarse clastic sediments as a molasse deposit. Finally, abutment of this complex with either older Aphebian arc complexes or the Archean Superior Province craton resulted in metamorphism, intrusion, and at least three phases of deformation during the Hudsonian orogeny.

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Labrador forms the eastern portion of the Precambrian Canadian Shield. It is divisible into four geologic provinces, each characterized by different orogenic history. Superior Province, in Western Labrador, and Nain Province, along the eastern and northern coast, represent parts of Archean orogenic belts. Both consist primarily of high grade metamorphic rocks, which in Nain Province are overlain locally by less deformed Proterozoic sedimentary and volcanic assemblages. Churchill Province trends northward across central Labrador, between the two older orogens. It is composed of a western belt of relatively little deformed sedimentary and volcanic rocks, and an eastern zone of high grade metamorphic rocks, both of which were last deformed in the Early Proterozoic Hudsonian orogeny. Grenville Province trends east-northeast across sothern Labrador. It is composed largely of quartzo-feldspathic gneisses, last deformed in the Grenvillian orogeny of the Middle Proterozoic. The metamorphic rocks of Grenville, Nain and Churchill Provinces are intruded by large anorthosite-adamellite plutons, emplaced during the Middle Proterozoic.

Exploration in Labrador has been concentrated in two areas: the Labrador Trough, in the western part of Churchill Province, and the "Central Mineral Belt" of Labrador, which extends eastward across the southern parts of Churchill and Nain Provinces. Mining in the Labrador portion of the Trough accounts for about half of Canada's iron ore production. Uranium, copper, beryllium and molybdenum occurrences are being investigated in the central mineral belt.

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Large amounts of geologic field data have been produced as a result of recent geologic investigations by the New Brunswick Department of Natural Resources, financed by the Federal Department of Regional Economic Expansion. This necessitated designing a standardized system for the collection, storage and retrieval of geologic field data, which is briefly described in this report.

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Late-orogenic sediments deposited alongside growing mountain belts reflect the rise and cooling of crystalline complexes within the core zone of the orogens. The nature of these molasse deposits is strongly influenced by structures adjacent to the sedimentary basins. Despite differences in scale and paleoclimate the molasse of the Alps and that of the Columbian Orogen show remarkable similarities.

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Comparison of Canada's frontier petroleum provinces with the North Sea suggests that much less oil will be found in Canada. It is concluded that the present export pattern for oil cannot be long maintained and that increased investment in petroleum exploration is essential.

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The Quebec part of the Abitibi volcanic belt is the subject of an intensive research project oriented towards providing detailed petrological and geochemical data integrated with stratigraphy and tectonics. In establishing the changing composition of the volcanic pile in the region north and south of Rouyn (from monotonous tholeiite basalt in the lower sections to intermingled calc-alkaline and tholeiitic series in the higher sections) such diverse subjects as the role of immiscibility in the formation of variolites, and the nature of quench-texture in Archean tholeiites have been investigated. A conference series designed to provide a means of exchange of information between project personnel and researchers investigating related topics elsewhere in Canada was convened. The feedback obtained during the conference series resulted in new directions being initiated within the confines of the project, and a complete traverse of the Abitibi volcanic pile from south of Rouyn to Matagami is planned.

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The annual CSEG convention, which was held this year at the Calgary Inn Calgary, Alberta, April 17th to 19th, 1974 has evolved over the last few years to the point where it has been regarded as the foremost meeting of geophysical exploration expertise in Canada.

This annual conference was designed to be technical in format and its prime purpose has been to promote the exchange and dissemination of technical data through all branches of the geophysical profession in Canada.

While the 1974 convention was ostensibly oriented toward technical content, the dominant overtones implicit in many of the papers were in fact political. This was of course predictable because of the uncertain future presently facing the resource industries (and consequently the geophysical industry) in Canada as a result of recent federal policy statements.

The 1974 convention attracted 750 registrants, a decrease of roughly eight per cent from the previous year. Papers at the conference were grouped under four general subdivisions: 1. data acquisition, 2. data processing, 3. interpretation, 4. general topics, with a considerable overlap between these classifications.

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