Nickel Sulfide Ores Related to Ultrabasic Intrusions in Canada
L. C. Kilburn, H. D. B. Wilson, A. R. Graham, Y. Ogura, C. J. A. Coats, R. F. J. Scoates, 1969. "Nickel Sulfide Ores Related to Ultrabasic Intrusions in Canada", Magmatic Ore Deposits, H. D. B. Wilson
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Canadian nickel sulfide ores related to ultrabasic rocks are divided into two categories based on geological environment. The Orogenic category is related to ultrabasic intrusions localized along or adjacent to major faults, whereas the Volcanic category is distributed throughout thick volcanic sequences as interflow sills and dikes.
In both the orogenic and volcanic categories, nickel sulfide deposits occur as disseminations within the ultrabasic intrusion, as massive and stringer zones at the ultrabasic contact, and as massive and stringer zones within the adjacent wall rocks.
The normal sulfide assemblage in most deposits is relatively simple, and comprises the primary minerals pyrrhotite, pentlandite, pyrite, chalcopyrite, and magnetite, usually in that order of abundance. Important exceptions are millerite, pentlandite, pyrite and chalcopyrite at Marbridge No. 2, Quebec and unusually high pyrite contents at Shebandowan, Ontario.
Petrographic studies reveal a pattern of progressive recrystallization with serpentinization. Increased serpentine grain size with recrystallization leads to displacement of sulfide minerals and finally complete destruction of primary silicate-sulfide textures.
In the Orogenic category, ultrabasic rocks are predominantly peridotite and pyroxenite; disseminated sulfide is the most common mode of occurrence, irregularly distributed throughout the ultrabasic intrusion; contact deposits are encountered less frequently and deposits in the wall rocks are rare. In the Volcanic category, ultrabasic rocks are predominantly peridotite with gabbro; contact deposits are most common; disseminated deposits are less common; and wall rock deposits are rare.
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This monograph on Magmatic Ore Deposits has resulted from a Symposium held at Stanford University on November 12 and 13, 1966. All except three of the papers that were presented are published in this volume as well as some of the discussion and the summation of the symposium. Unfortunately much of the discussion cannot be included because the volume is already so large. The best introduction to this volume is, perhaps, the introduction as it was presented at the symposium:
This symposium was conceived in 1962 when the Program Policy Committee recommended that the . Society of Economic Geologists should sponsor a symposium on magmatic ore deposits. The Committee under the chairmanship of John K. Gustafson believed this to be an effective method of advancing geologic thought. It is fitting that the symposium should finally be held during Gustafson’s presidential year. The proposal of the Program Policy Committee was approved by Council at its meeting in November, 1962. A special committee consisting of G. Kullerud, J. A. Noble, C. H. Smith, T. P. Thayer, with H. D. B. Wilson as chairman, was appointed by the President, Olaf N. Rove, in February 1963 to make arrangements for the symposium. E. N. Cameron, Secretary of the Society, was ex officio member of the special committee and remained as an active member when he resigned the secretaryship. C. H. Park, Jr. joined the committee shortly after its formation.
The Program Policy Committee was prompted to recommend the symposium by the realization that the underlying theory of the formation of magmatic ore deposits was formulated many decades ago., In the intervening years, much new data have been acquired from systematic research. It seemed to the Program Policy Committee that it was time for those with an abiding interest in the magmatic deposits to meet to assess this new data and to point out the unresolved problems.
The symposium was entitled “Symposium on Magmatic Ore Deposits.” The special committee accepted the terminology in the “Glossary of Geology and Related Sciences,” Edition 2, page 175.
Magmatic Deposits Certain kinds of mineral deposits form integral parts of igneous rock masses and permit the inference that they have originated, in their present form, by processes of differentiation and cooling in molten magmas. (Lindgren p. 863, 1929).
The symposium committee has added the term “ore” to attempt to keep the discussions centered on ore, or near ore material, or with