Scientific Drilling in Canada — Past and Future
Several countries presently have national programs for deep crustal studies, principally by reflection and refraction seismology, but some with strong components of other techniques such as magnetotellurics. Such surveys are capable of providing information on the nature of the Earth’s crust to depths of several kilometres, and are essential to our understanding of the processes by which the crust has evolved. However, they provide only two-dimensional information, and the interpretation of that information is often ambiguous. By careful choice of survey lines the importance of the information can be substantial, but it is still severely restricted areally. Potential field geophysical surveys are able to provide much greater areal coverage, but their interpretation is often difficult because of the inherent non-uniqueness of their solutions. Multidisciplinary studies can help to reduce this problem if different potential field techniques, with different resolving powers, are used. By combining the two types of survey a clearer picture of the structure of the crust is possible. However, notwithstanding the great value of geophysical surveys, ultimately there is only one way to gain exact knowledge of the nature, composition and structure of the crust, and that is to drill into it.
KeywordsGreenstone Belt Impact Structure Canadian Shield Heat Flow Measurement Sudbury Structure
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