Evidence of exhalative origin for Tasmanian tin deposits

Abstract Orebodies of the Renison Bell - Mt. Bischoff tinfield in Tasmania are stratabound, conformable lenses of massive cassiterite-bearing pyrrhotite, with underlying discordant, fault-fracture-controlled and more siliceous ore. The deposits occur in eugeosynclinal, trough-deposited sedimentary and mafic volcanic rocks which are stratigraphically equivalent to differentiated volcanic rocks that contain volcanogenic massive base metal sulphide deposits in a parallel arc to the east. Textures of the massive pyrrhotite ore suggest that it has undergone metamorphic recrystallization. Although the massive ore contains both monoclinic and hexagonal pyrrhotite, a study of a few samples from one orebody suggests that their distribution is stratigraphically controlled, with the monoclinic variety abundant only at the base. The distribution pattern of rare-earth elements in massive ore is similar to that of volcanogenic massive base metal sulphides in New Brunswick, and suggests that mixing of sea water with exhalative hydrothermal brines occurred during ore deposition. Tin is a common accessory element in many volcanogenic massive base metal sulphide deposits, providing strong evidence that it, too, is transported and deposited by volcanic-affiliated hydrothermal brines.Sedimentary rocks containing the massive orebodies are fine grained, thinly laminated, compositionally banded and of mixed chemical sedimentary-tuffaceous origin. They include finely recrystallized chert, carbonate-rich and pyritic varieties; and soft sediment deformation structures in these rocks suggest that dense sulphides deformed underlying, less dense chert prior to lithification. Close to ore the chert becomes massive and coarsely recrystallized, as does the carbonate, which is here strongly enriched in Fe and Mn. Apatite is present in pyritic, cherty and carbonate-rich beds and in the ore itself, in all of which it shows a similar pattern of rare-earth element distribution, suggesting that it is of marine sedimentary origin.These deposits have traditionally been considered as epigenetic replacements of favourable carbonate horizons by hydrothermal fluids derived from later Devonian porphyritic intrusions. Some of these intrusions have associated tin-bearing greisens. The above relationships suggest, alternatively, that, like massive base metal sulphides, the tin deposits were of original syn-sedimentary origin. Circulating hydrothermal brines generated during early Cambrian eugeosynclinal subsidence and tectonism rose through steep fault-fractures, there giving rise to the discordant orebodies, and were discharged on the sea floor, where the massive pyrrhotite lenses were precipitated with the associated cherts and carbonates. In some places, Devonian intrusions remobilized the earlier deposits, forming greisens and new epigenetic veins.Finally, the geologic setting of these deposits, in trough-deposited sedimentary and mafic volcanic rocks, suggests another favourable environment for massive sulphide exploration which is quite different from the domalfelsic volcanic environment so heavily favoured currently in North America.
Keywords: Ore deposits, Tin deposits, Tasmania, Pyrrhotite, Cassiterite, Sulphides, Massive sulphides, Renison Bell Mine, Exhalative origins, Volcanogenic rocks.
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Summary: Thunder Bay Terminals' plant, now in operation, cost about 70 million dollars and was completed on time and under budget. The paper is the project manager's account of this accomplishment. From site selection through feasibility, engineering and construction to realization, he emphasizes the necessary philosophies for the control of time and money. The computer as a tool is discussed, as well as techniques for procurement.
Publication: CIM Bulletin
Author(s): P. R. COOK
Keywords: Thunder Bay Terminals Ltd., Site selection, Management, Construction, Planning, Approvals, Permits, Scheduling.
Issue: 808
Volume: 72
Year: 1979
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Summary: The transportation challenge began with the need to move millions of tons of coal annually from Western Canada to Ontario. The paper will discuss the options which were available, the final mode selected and the economic trade-offs which were involved. It will outline the demands of unit train technology and the effect of transportation requirements on the other elements of the whole system.
Publication: CIM Bulletin
Author(s): R. E. LAWLESS, R. P. LANGLOIS
Keywords: Thunder Bay Terminals Ltd., Transportation, Railways, Trains, Unit Trains, Coal.
Issue: 808
Volume: 72
Year: 1979
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Summary: This paper discusses: (1) the need for Western Canadian coal in eastern Ontario Hydro plants; (2) design parameters—unit trains, year- 'round receiving from trains, and shipping (Great Lakes season); (3) equipment chosen—dumper-indexer, outhaul conveyor, yard belt, stacker, reclaimer, surge-bin feeders, shiploader, docking system and dust control; (4) foundation and soil conditions—dumper house, yard belt, surge bin and dock-piling-runway; (5) winter conditions—thaw...
Publication: CIM Bulletin
Author(s): J. CARR
Keywords: Thunder Bay Terminals Ltd., Design, Terminals, Plant design, Coal handling, Ontario Hydro, Stockpiles, Dumper houses, Car dumpers, Winter operations, Stackers, Reclaimers, Shiploaders.
Issue: 808
Volume: 72
Year: 1979
Text
Summary: Concern over the acid drainage and radionuclide dissolution problems associated with current uranium tailings disposal methods, as well as the lack of thorium production in Canada, has prompted investigation into new and improved methods for the extraction of uranium and thorium from their ores.One such method currently under investigation at CANMET is the high-temperature chlorination of uranium ore, for which the objective is to develop a process which is both economically viable and...
Publication: CIM Bulletin
Author(s): J. M. SKEAFF
Keywords: Extractive metallurgy, Ore processing, Chlorination, Ra-dionuclides, Pyrite, Tailings disposal, Uranium tailings, Acid drainage, Uranium extraction, Thorium extraction, Radium extraction, Elliot Lake.
Issue: 808
Volume: 72
Year: 1979
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Summary: After more than 93% of the uranium is extracted from Elliot Lake uranium ores by a sulphuric acid leaching process, the leach residue (tailings) contains small amounts of uranium and radioactive isotopes, particularly radium-226, which is the most serious health hazard. Heavy metal components and pyrite are also present, along with the gangue minerals. Currently, over 1000 acres of the Elliot Lake area are covered with these tailings, which contain over five million tons of pyrite.Because of...
Publication: CIM Bulletin
Author(s): D. RAICEVIC
Keywords: Uranium tailings, Elliot Lake, Decontamination, Radioactivity, Flotation, Pyrite, Tailings disposal, Environmental control.
Issue: 808
Volume: 72
Year: 1979
Text
Summary: McKellar Island, the site of the Thunder Bay Terminals coal handling facility, is situated in a low-lying delta area. The ground surface across the island, which is relatively flat at between 1 and 5 ft above lake level, is underlain sequentially by surficial peat materials, extensive lacustrine strata and glacial till deposits which overlie shale bedrock. Each of these major stratigraphic units significantly influenced the design and construction of major features of the facility.Coal is to...
Publication: CIM Bulletin
Author(s): J. L SEYCHUK, J. H. A. CROOKS
Keywords: Thunder Bay Terminals Ltd., Geotechnical engineering, McKellar Island, Terminals, Design, Construction, Geomorphology, Lacustrine deposits, Foundations, Stockpiles, Coal, Slope stability, Conveyors, Tunnels, Monitoring
Issue: 808
Volume: 72
Year: 1979
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