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Proactive disclosure Print version   | |  Co-operative Geological Mapping Strategies Across Canada : COGMAPS Ancient Pacific Margin, British Columbia and Yukon
Ancient Pacific Margin, British Columbia The Ancient Pacific Margin Project combined the expertise, energy and resources of the Geological Survey of Canada, the British Columbia Geological Survey, and numerous university studetns and faculty to map portions of the mineral-rich rocks that once formed the craton margin. Onset of Devonian-Mississippian extension accompanied by faulting, volcanism, and basin segmentation, provided fertile, volcanism, and basin segmentation fertile conditions for the deposition of polymetallic, stratabound massive sulphide mineralization. Multiparameter geological maps are now available.
Ancient Pacific Margin, Yukon The Yukon and Ancient Pacific Margin projects were federal/territorial initiatives designed to develop a fuller understanding of the geology and hence the mineral prospectivity of the Yukon Tanana Terrane. Successes included the discovery of a new VMS prospect; the development of a streamlined and efficient process for data management and map production in the field; and the dissemination of local expertise and knowledge. (TGI and NATMAP projects)
Canada's Ancient Pacific Margin
Synopsis The Ancient Pacific Margin Project was a multi agency, cooperative, bedrock-mapping initiative sponsored by the Geological Survey of Canada under the auspices of the National Mapping Program (NATMAP). It provides new multi parameter geologic maps, reports, and models for the mineral-rich belt that formerly occupied the outer reaches of Canada's Pacific continental margin. This project demonstrated the value of collaborative working agreements between governments, universities, and industry. Rationale The ancient Pacific margin was the site of multiple, overlapping sedimentary basins and volcanic edifices in which metals were concentrated, often as stratabound and stratiform massive sulphides. Margin evolution was long-lived and complex, starting in the Paleoproterozoic and ending in the Jurassic when wholesale mountain building transformed the margin into the Cordilleran orogenic belt. Our interest in deciphering margin history prior to Mesozoic orogenesis stemmed from three objectives: 1) to better define the boundary conditions that existed prior to mountain building, 2) to better establish the nature and extent of geological linkages across the ancestral margin, and 3) to better understand the geological circumstances that led to the deposition of metal occurrences, especially those of latest Devonian-earliest Mississippian age. In this way we sought to provide a new, integrated, and readily accessible framework of geological maps, reports, ideas and models that would aid in the sustainable development of mineral resources.
Approach Areas of investigation were chosen because of their strategic importance, and included regions where numerous mineral occurrences were known, regions where crucial geological relationships could be studied in detail, and regions where little was known but prospects for discovery were high. Emphasis on joint ventures with other government surveys, universities, and industry engendered cooperative planning and delivery of products, maximized return on financial and human resource commitments, and permitted the training of 'next generation' earth scientists. Recognizing that most of the 'ancient Pacific margin belt' was not mapped at scales required by most map users, provision of geo-spatial, multi parameter geologic maps was the priority. Geology Mid Palaeozoic time (circa 360 Ma) heralded an important change in margin dynamics, from passive subsidence to active subduction associated with back-arc extension. This led to margin segmentation, especially in the north, where several fragments of crust became separated from the continent by ocean basins of unspecified width. The combination of structural, magmatic and sedimentary processes associated with extension and rifting created a fertile environment for the concentration and deposition of polymetallic sulphides. Asymmetrical roll-back (trench retreat) of the subducting "Pacific" plate is one explanation that accounts for the south-to-north increase in the magnitude of extension that culminated in rifting in the north but not in the south. Outcomes A significant change in our understanding of the history and dynamics of the ancestral Pacific margin is manifest in the new multi-parameter geological maps completed and nearing completion. Chrono- and litho-stratigraphic correlation of map units is more precise; chemical characterization of magmatic rocks is significantly improved; stratigraphic and tectonic histories are better understood; and most important, areal distribution of potential metal-bearing successions is better defined. Fifteen masters and doctoral candidates have successfully defended their research projects and all have gone on to geoscience careers. Data is coming on-stream in readily available digital form, and the Geological Association of Canada will publish a special volume of summary papers. The efficiency and capability of the mineral exploration industry to identify new targets has been increased and we anticipate a substantial long-term return on our investment of resources. More Information A compendium of papers, abstracts, maps, and reports is available by contacting Dr. Robert Thompson
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