Abstract

The Canadian Committee on the Dynamics and Evolution of the Lithosphere (CANDEL; see appendix for membership) recommends that LITHOPROBE studies be carried out in specific corridors in several parts of Canada, selected to solve key geological problems. Although the past two decades have witnessed major conceptual advances in earth science through plate tectonic models, many aspects of continental tectonics and evolution have resisted application of plate tectonic theory. Because the continents contain most of the world's known hydrocarbon and mineral resources, continental tectonics is the major challenge to earth science in the 1980s. Canada, with its vast territory and varied geology, is a natural laboratory for these studies. LITHOPROBE involves the use of combined geological and geophysical techniques to determine the third dimension of crustal geology, by extending and relating surface geology to structure at crustal depth. A large bank of innovative techniques and concepts is available now for LITHOPROBE studies, ranging from advanced high resolution seismic techniques and deep drilling, to optimum computer-based interpretational methods and geological models of the latest plate tectonic concepts. When combined with more traditional methods, these new tools substantially improve our prospects for resolving the three-dimensional structures and evolutionary histories of key geological targets. The proposed programme is national in scope, and will involve a broad spectrum of earth scientists. Based on regional geological/geophysical considerations, a number of LITHO-PROBE transects are suggested within five regions: Appalachian Orogen/Mesozoic Passive Margin, Arctic, Eastern Cordillera, Western Cordillera and Modern Pacific Margin, and Precambrien Shield. Two areas are tentatively identified for the initial phase of the LITHO-PROBE programme: onshore-offshore profiles of the northeast Newfoundland area; and the southeastern Cordillera. For each area both the surface geology and the geological/geophysical problems are well defined. Each area thus holds the promise of a high initial degree of success from the completed transects. A Precambrian corridor is of next highest priority. Key geological problems for all five regions as well as the details of methodology and costs are presented in the paper. The specific proposals were developed by CANDEL through study groups. Studies of the depth dimension in relation to surface geological features will provide the three-dimensional geometry of major rock units and the recognition of similarities between buried geological environments which may be host to resources, and those exposed at the earth's surface. Indirect benefits include exchange of ideas and results between those engaged in the search for resources and those involved in basic research,enhanced training of Canadian geo-science students, and increased incentives to Canadian industry to develop innovative techniques and instrumentation. An initial capital investment of about $4million is estimated, with each corridor costing an additional $6 million on average. Five or six LITHOPROBE corridors could be completed in five years, and CANDEL considers this to be a realistic goal. Locations of LITHOPROBE corridors and methodology should be continually reviewed and assessed. The cost of the programme largely reflects the costs of high resolution seismic reflection and refraction technology, but also provides for the application of deep drilling, and of more traditional geological/geophysical measurements. CANDEL recommends that appropriate new funds be identified by NSERC and EMR. Consideration should be given to mechanisms by which funding to these agencies can be administered to ensure coordination between studies. Disbursement should be guided by a steering committee charged with setting overall priorities, and composed of government, university and industry representatives.This committee could be supported by a series of advisory sub-committees, each similarly charged for a particular regional LITHOPROBE project. LITHOPROBE as a programme for the 1960's can provide a focus for the government-, university-, and industry-based Canadian earth science community to cooperate on a scale never before attempted, as the scope of the problems and challenges demands. It also can concentrate the national expertise on problems of interest and significance to all Canadians.