An Exploration Application for Lead Isotope Ratios, Stewart Mining Camp, Northwestern British Columbia

Abstract The Stewart mining camp has a long history of precious and base metal mining. The camp is abundantly mineralized, with more than 200 widespread, varied, vein prospects, deposits and orebodies. These show wide variations in the mineralogy of ore, gangue and alteration assemblages, and wide variations in textures and structural settings. This report establishes the timing of the different metallogenic epochs and suggests a specific exploration application for systematic lead isotope analyses.
Galena lead isotope ratios from a range of mineral occurrences indicate that all these varied deposits formed during two main mineralizing events. Lead isotope data from the Stewart mining camp do not provide absolute ages for the formation of mineral deposits, but the relative distributions of data are consistent with dates determined in other studies. One ore-forming episode occurred in the Early Jurassic and the other in the Middle Eocene. Both metallogenic epochs were brief, regional-scale phenomena. Some deposits from the younger mineralizing episode were em-placed adjacent to or superimposed on the older deposits.
Field and laboratory studies show that the two metallogenic epochs are characterized by different base and precious metal suites: Early Jurassic gold-silver-zinc-lead-copper; and Middle Eocene silver-lead-zinc. Therefore, showings of different ages have different base and precious metal potentials and deserve different exploration emphasis. Lead isotope studies provide a reliable, cost-effective method for evaluating the age and commodity potential of small or recently discovered mineral showings and for setting exploration priorities on properties with several varied mineral occurrences. The determination of the age and metal potential of a prospect at an early stage of exploration may . govern the urgency, intensity or even the necessity for further exploration work.
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Summary: The Geological Society has its own quarterly journal called Exploration
and Mining Geology, for the publication of Canadian and international papers on
applied aspects of mineral exploration and exploitation, including mineral
deposit geology, geochemistry, and geophysics, mining geology, mineral resource
appraisal and estimation methods, environmental geology, and case histories. The
editor of the journal is Jeremy P. Richards
Publication: Exploration & Mining Geology
Issue: 2
Volume: 2
Year: 1993
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Summary: The Mobrun VMS deposit in northwestern Quebec does not fit the classic Noranda-type model, but exhibits characteristics more consistent with a Mattabi-type deposit. The orebodies are underlain by fragmental volcanic rocks indicative of explosive volcanism in shallow water. Felsic volcanic rocks are more abundant than mafic rocks. Alteration assemblages comprise chlorite, carbonate, sericite, and quartz. Broad semi-conformable alteration occurs high in the footwall to the 1100 lens. Mobrun...
Publication: Exploration & Mining Geology
Author(s): ADRIENNE C.L. LAROCQUE, C. JAY HODGSON
Issue: 2
Volume: 2
Year: 1993
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Summary: Borate minerals, such as colemanite, ulexite and borax, have been reported in Tertiary continental basins of West Anatolia, Turkey, and Samos Island, Greece.
Tuffaceous rocks interbedded with the berates are rich in authigenic silicate minerals such as zeolites, potassium feldspar and opal-CT, all of which have a genetic association with the borates. Chemical analyses of the tuffaceous rocks show variation in major elements due to the varying percentage of carbonaceous, detrital, and volcanic...
Publication: Exploration & Mining Geology
Author(s): C. HELVACI, M.G. STAMATAKIS, C. ZAGOUROGLOU, J. KANARIS
Issue: 2
Volume: 2
Year: 1993
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Summary: Buried, possibly mineralized granite cupolas at the Silsilah tin deposit in Saudi Arabia (lat. 26°06' N, long. 42°40' E) have been successfully located using a closely spaced electric-field-ratio profiling technique. In this study, electrical fields at 27 and 270 Hz across grounded electrodes spaced 50 m apart were measured along six traverses. This method is in-terpretable by inspection, unlike the dipole-dipole technique, which requires mathematical modeling for interpretation.
In the study...
Publication: Exploration & Mining Geology
Author(s): ROBERT J. KAMILLI, CHARLES J. ZABLOCKI
Issue: 2
Volume: 2
Year: 1993
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Summary: The NERCO Con Mine is situated in the amphibolite fades aureole of the Western Plutonic Complex overprinting the Yellowknife Greenstone Belt. Metamorphic grade of the upright monoclinal basaltic succession decreases from hornblende-amphibolite facies along the border of the batholith to greenschist facies. Metamorphic isograds, subparalleling the faulted margin of the batholith, transect volcanic stratigraphy and coincide with major gold-bearing shears.
Gold mineralization is confined to...
Publication: Exploration & Mining Geology
Author(s): D.W. McDONALD, R.L. HAUSER
Issue: 2
Volume: 2
Year: 1993
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Summary: Many water inflows in Saskatchewan potash mines are linked to salt anomalies. Potash ore and three anomalies in the PCS Cory potash mine in the Patience Lake Member of the Prairie Evaporite Formation were studied to understand the processes involved in their formation. Another goal was to find geological indicators of the proximity of anomalies. A geological model that relates the potash to the salt anomalies has been developed.
Up to five post-burial fades may be recognized. These range from...
Publication: Exploration & Mining Geology
Author(s): CHRISTOPHER BOYS
Issue: 2
Volume: 2
Year: 1993
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Summary: The mineralogy of samples from the Wellgreen Cu-Ni-Pt-Pd deposit, Yukon Territory, is complex and the metals of interest are contained within fine-grained minerals which vary in size and mineral associations from sample to sample.
The major Ni carriers are pentlandite and violarite; the major Cu carrier is chalcopyrite. About 70% of the major Ni carriers and 78% of the major Cu carrier will be liberated at a grind of 80% -26.7 /on (-500 mesh) for typical low-grade gabbro (West zone, sample...
Publication: Exploration & Mining Geology
Author(s): LOUIS J. CABRI, LARRY J. HULBERT, ROLANDO LASTRA, SOEY H. SIE, CHRIS G. RYAN
Issue: 2
Volume: 2
Year: 1993
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