This paper mainly concerns the active fields of Petsamo (Pechenga), Monchegorsk, and Kotalahti.
The Petsamo deposits are associated with a zone of layered intrusions that lie within low-metamorphic volcanics and sediments framed by gneisses. The orebodies, which adhere to the footwall of the intrusions, are comprised of disseminated sulfides in serpentinite, many with underlying massive sulfides. With increasing deformation, ore breccias gain in importance and the mineralization extends into adjacent phyllites. The pattern, composition and distribution of the sulfidic phase and its species, reflect local conditions.
The Monchegorsk mineralization lies in layered ultrabasics underlain by gneisses. The sulfides occur as disseminations, massive veins, and minor bodies. The veins strike parallel with, and are grouped above, the long axis of the massif, dip across the layering and die out before reaching the base. Dike rocks traversing the massif are cut by veins.
The Kotalahti orebodies are mineralized portions of complex basic units encased in steeply dipping gneisses. Pegmatitic and amphibolitic bodies traverse the gneisses and brecciate the ore-bearing masses. Orebodies consist of an intricate mixture of disseminated perknite, peridotite and gabbro, and barren pegmatitic and amphibolitic matter, superimposed on which are bodies and stringers of massive sulfides. One exception is an ore shoot entirely enclosed in schists without any apparent connection to basic units.
Figures & Tables
Magmatic Ore Deposits
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