COMMENTARY — Miners seeking GSC data

.BMichael Thomas

The regional geophysics section of the Geological Survey of Canada (GSC) focuses on the acquisition, archiving, distribution and analysis of aeromagnetic and gravity data. Historically, the section has planned and managed national programs to measure and map the magnetic and gravity fields over the Canadian landmass and territorial waters.

Recently, the responsibility of acquiring gravity data has been moved to another agency within Natural Resources Canada, but distribution remains the job of the GSC. Magnetic and gravity data sets resulting from these programs are archived in the geophysical data centre. There, they are accessible to a broad spectrum in the geoscientific community, including the mineral and hydrocarbon exploration sectors, consulting companies, provincial governments and academia. The GSC’s expertise in planning and managing aeromagnetic surveys is recognized internationally, and currently the regional geophysics section is involved in projects in Guinea and Argentina.

Magnetic and gravity data play an invaluable, unique and sometimes critical role in mineral exploration programs. For example, programs may be significantly enhanced by consulting the geophysical data centre in the early stages of exploration. Since the data were collected in the context of regional mapping, they are particularly useful for evaluating the exploration potential of specific areas. Often, they provide the only insight into bedrock geology obscured by glacial deposits, bodies of water or younger sedimentary sequences. Rock units may be defined and rock types predicted, while trends and continuity of structures (some closely associated with ore-forming processes) may be delineated with confidence.

From a target-oriented perspective, distinctive magnetic signatures, such as those associated with massive sulphide deposits and kimberlites, may help direct follow-up ground geophysical surveys and drilling.

The utility of the geophysical data centre to the resource industry is reflected in the number of requests for data, which average about 280 per year (most from Canadian clients). International requests, though much fewer in number, have originated in about 20 countries worldwide, including Australia, Papua New Guinea, Norway, South Africa, Russia and the U.S.

Data are distributed by computer, and hard-copy plots are prepared to meet the client’s particular need for scale, map projection, and inclusion or exclusion of drainage, ocean shore lines, political boundaries or geographical grid lines.

In recent years, requirements by mineral exploration companies for high-quality magnetic data in areas where gaps exist in the national coverage have resulted in surveys funded by government-industry consortiums.

Such arrangements have been mutually beneficial. Industry partners receive exclusive rights to the data for periods that typically last two years, after which time data become accessible to the public through the geophysical data centre. For example, results of a co-operative survey on Victoria Island in the Arctic, in which the industry partners were Monopros and Western Mining Corp., are scheduled for release this summer.

The regional geophysics section has participated in several

government-funded programs aimed directly at assisting Canada’s mining industry in areas of high mineral potential. Magnetic survey specifications in these programs are designed to obtain high-resolution data. A current example is the EXTECH program in the Bathurst mining camp of New Brunswick, where the value of the survey has been demonstrated by the successful intersection of a small, high-grade sulphide deposit, targeted on the basis of coincident magnetic and conductivity anomalies.

Scientists in the regional geophysics section are active in areas of software development and geological interpretation of magnetic and gravity data. One example of new software is an automatic method to detect magnetic anomalies related to kimberlite pipes in diamond exploration. An ongoing interpretation project involves compilation of a geophysical atlas of the Bathurst camp, along with partners in the GSC and New Brunswick Department of Natural Resources and Energy. Geophysical signatures of 20 sulphide deposits will be featured, giving the atlas relevance for exploration in other camps hosting massive sulphides.

— The author is a research scientist with the Geological Survey of Canada.