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Proactive disclosure Print version   | |  Searching for diamonds in Canada
A.N. Lecheminant, D.G. Richardson, R.N.W. DiLabio, and K.A. Richardson Diamonds! "The Great Canadian Diamond Rush" north of Yellowknife (McNellis, 1993) revives for this generation a sense of the excitement and dreams of the Klondikers of the last century. Until recently, most Canadians thought of diamonds only as exotic and treasured jewels, appreciated for their rarity and brilliance, but of little direct economic interest to Canada. Prospective areas of the Canadian Shield were largely ignored, even though for almost thirty years geologists have known that diamond deposits are closely associated with the old stable nuclei of continents (cratons). Diamonds originate in the Earth's mantle at depths >150 km and most are stored in distinctive source rocks that make up part of the stable mantle root beneath Archean (> 2500 million years old) and Proterozoic (2500 to 570 million years old) cratons. The two most important diamond source rocks are peridotite and eclogite, and each rock type contains a characteristic suite of minerals that are key indicators for diamond exploration. Primary diamond deposits occur where kimberlite and lamproite magmas erupted, since these deep-seated magmas provide a medium to sample diamond-bearing source rocks and transport diamonds and associated indicator minerals to surface. Economic diamond-producing gelds occur on most Archean cratons worldwide, with the notable exception of Archean cratons in Canada, such as the Superior, Slave and Nain provinces. However, intense exploration activity throughout Canada, since the late 1980s, has located numerous diamond-bearing kimberlite in the Slave Province near Lac de Gras, north of Yellowknife, and additional kimberlites have been discovered in Alberta, Saskatchewan, Manitoba, Ontario, and Quebec. Surprisingly, before the 1990s, diamonds were almost absent from Canadian folklore and mineral history. Jacques Cartier's men mined "diamonds" at the mouth of Rivière du Cap-Rouge in 1541, but their treasure turned out to be worthless quartz. This episode gave Quebec's Cap Diamant its name, and the story survives in the saying "faux comme des diamants du Canada". Early this century, reports by officers of the Geological Survey of Canada suggested microdiamonds were recovered from chromitite lenses in the Tulameen complex, British Columbia Camsell, 1911) and from chromite ore mined at Black Lake, Quebec (Dresser, 1913). Although the Tulameen "microdiamonds" were later shown to be synthetic periclase formed by laboratory heating of the rock samples, recent work in Morocco, Spain, and Tibet has documented the association of diamonds with similar mechanically emplaced untramafic rocks (Davies et al., 1993; Baio et al., 1993). J.J. Brummer (1978) culled meagre data from a wide range of source's to provide a remarkably comprehensive overview of the early history of "Diamonds in Canada". He noted that W.H. Hobbs (1899) first raised the possibility of diamond sources in Canada, based on discoveries of diamonds in glacial drift south of the Great Lakes. Although a 33 carat alluvial diamond was discovered near Peterborough, Ontario before 1920, and some finds were reported in Saskatchewan and Quebec in the late 1940s and early 1950s, significant diamond exploration did not begin in Canada until the 1960s, when indicator mineral surveys were conducted in Ontario by mining companies, the Ontario Department of Mines and the Geological Survey of Canada. Satterly (1949) recognized the first Canadian kimberlites in Michaud Township, north of Kirkland Lake and, by the late 1960s, several other kimberlites and a few diamonds had been discovered. The history of recent diamond discoveries in Canada has yet to be written, but many of he most enthusiastic extortionists, active over more than 25 years, now find themselves drawn to the Barrenlands near LaC de Gras, hoping to be among the first to bring Canadian diamonds to world markets. Discovery of world-class diamond deposits depends on determined mineral exploration aided by a reliable and comprehensive geological database. Papers in this volume provide a snapshot of the spectrum of geoscience information available to assist diamond exploration in Canada. Maps provide elegant and ready access to data acquired and interpreted by the Geological Survey of Canada (GSC), Provincial Surveys, and University-based researchers. Mapping by the GSC now integrates traditional geological, geophysical, geochemical, and surficial surveys with specialized Geographic Information System (GlS) techniques, several of which have important applications to diamond exploration. This volume provides background for several of the national databases maintained by the GSC, as well as summaries of specific areas of diamond-related research and short reviews of GSC research relevant to diamond exploration. Readers seeking further information are encouraged to contact the authors, whose addresses are listed at the end of the volume. In addition, the GSC has published a bulletin that reviews the use of various indicator minerals and mineral assemblages as important aids in diamond exploration in Canada (Fipke et al., 1995). Reports contained in this volume were submitted during the period December 1994-June 1995, and have been reviewed by GSC staff, but have not undergone rigorous scientific review. Thanks are extended to the many scientists who contributed to this volume, and to OJ. Ijewliw, R. Lacroix, D. Paul, S. Scully, M. Sigouin, K. Venance and T. West, all of the GSC, for assistance with figure production. W.C. Morgan undertook the technical editing. Preliminary corrections, compilation and layout were completed by A. Anand with assistance from N. Devine, C. Bélanger, L. O'Neill and C. Plant (all of the GSC). Printing of this volume was funded by the GSC's Mineral Resources and Continental Geoscience divisions. Sadly, two scientist who contributed to this volume died in 1995. On February 23, Chris Roddick died in a skiing accident in Vermont, tragically cutting short a scientific career in isotope geoscience characterized by imagination, enthusiasm, and curiosity. His contribution to the Geochronology Laboratory of the GSC is commemorated in the introduction to the 1995 Radiogenic Age and Isotope Studies report ( Parrish, 1996). Chris leaves a rich legacy and is deeply missed. Marianne Mareschal, a leading scientist in Canada's LITHOPROBE project, passed away on July 11, 1995, after a long and courageous struggle with cancer. She was a member of the organizing committee for the Precambrian conference in Montreal and a dedication to her is published in the Program and Abstracts volume for Precambrian '95'. Her kindness and energy touched all whom she met and she will be missed by many. Most of all, her direction and vision in combining seismic and electromagnetic experiments for the study of cratonic root:, which was her last major research effort, will bear fruit for many years to come. A foundation, established in her name, will be used to provide a student bursary in geophysics at the École Polytechnique de Montréal. Contributions should be forwarded to:
Fonds Marianne Mareschal,
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