Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Sherlock, R. L. Articles by Cousens, B. L. Search for Related Content GeoRef GeoRef Citation

Geologic and Geochronologic Constraints on the Timing of Mineralization at the Nanisivik Zinc-Lead Mississippi Valley-Type Deposit, Northern Baffin Island, Nunavut, Canada^*

Ross L. Sherlock

Canada-Nunavut Geoscience Office, P.O. Box 2319, Iqaluit, Nunavut, Canada X0A 0H0

James K.W. Lee

Department of Geological Sciences and Geological Engineering, Queen’s University, Kingston, Ontario, Canada K7L 3N6

Brian L. Cousens

Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B6

Corresponding author: email, sherlock{at}nrcan.gc.ca

The Nanisivik mine is located on Borden Peninsula, northern Baffin Island, about 750 km north of the Arctic Circle. The deposit is hosted by Mesoproterozoic sedimentary rocks of the Bylot Supergroup that rest unconformably on the Mary River Group, an Archean to Proterozoic basement complex of granites and gneisses. The Mesoproterozoic strata have been folded into broad, open folds with north-south–trending axes. The sulfides at Nanisivik are hosted in petroliferous dolostones of the Society Cliffs Formation. A series of long-lived, east-west–trending, normal faults divide the Nanisivik area into a series of horst and grabens. All known sulfide bodies are associated with normal faults, particularly where they cut the fold axes of antiforms.

The geometry of the main sulfide body indicates that sulfides were emplaced after tilting and folding of the host strata and that a horizontal feature such as a gas-water interface controlled the precipitation of the sulfides. The sulfides show no displacement across the Keystone fault, although the fault has displaced the host stratigraphy by about 150 m and has displaced the Mine dike, a Franklin-aged intrusion (~723 Ma), by about 40 m with steep oblique-slip movement. A progressive potassium feldspar alteration selvage, about 3 m wide, on the margin of the Mine dike has been recognized. Textural evidence and immobile element ratios indicate that this is an alteration product of the dike, interpreted to have formed by the hydrothermal event that emplaced the sulfides. Similar alteration assemblages are present throughout the mine and are interpreted to be altered siliciclastic sedimentary rocks. The ⁴⁰Ar-³⁹Ar ages of orthoclase from these alteration assemblages indicate a Middle Ordovician (461 Ma) age of mineralization.

Although the regional process that resulted in the formation of the Nanisivik deposit remains unclear, it is possible that topographically driven fluid may have resulted from localized Middle Ordovician uplift in the region, as seen at the Navy Board High. Basinal brines may have migrated along the basement contact within the overlying Mesoproterozoic siliciclastic sedimentary rocks, and local basement topography, such as the horst and graben structures, may have focused fluid flow into the Society Cliffs Formation at Nanisivik. Local structural and stratigraphic traps would ultimately have localized and controlled the precipitation of the sulfides.

This article has been cited by other articles:

				S. E. Kesler and M. H. Reich Precambrian Mississippi Valley-type deposits: Relation to changes in composition of the hydrosphere and atmosphere Geological Society of America Memoirs, January 1, 2006; 198(0): 185 - 204. [Abstract] [Full Text] [PDF]