The Wecho River area comprises the eastern half of NTS 85O. Field mapping during 2003 took place between mid-July and late August and focused on the northern half of the Wecho River area, in NTS 85O/9, 10, 15, and 16. In 2004, field mapping occurred from mid-June to late August and focused on the southern half of the Wecho River area, in parts of NTS 85O/1, 2, 3, 7, and 8.
Previous mapping by Lord (1942) and Yardley (1949) defined the area as mostly undifferentiated, late Archean granites. This mapping project, the first systematic bedrock study of the area since Lord and Yardley, was able to further delineate the rock types. The northern part of the area is partially underlain by supracrustal rocks and a number of granitoid suites. In the southern part of the area, the supracrustal rocks and granitoid rocks were subdivided.
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Bedrock geology of the northern Wecho River area. Modified after Ootes (2004).
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Geology of the southern Wecho River area. Modified after Ootes (2005).
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Supracrustal rocks in the Wecho River area range from greenschist-grade in the south near Mosher Lake, to granulite-grade in the north in the vicinity of Wecho, Hickey, and Dauphinee lakes. The supracrustal packages have been extensively intruded by young Archean granitoids and offset by crustal scale Proterozoic faults.
In the northern part of the area, the supracrustal rocks locally attained granulite grade. Generally the rocks are metatexites with minor occurrences of diatexite. Silicate iron formation and amphibolite to mafic granulite occurs locally.
Mafic and intermediate rocks include mafic volcanics in the south that form a lenticular, north-trending belt within the turbidite sequences. Mafic rocks in the north include amphibolite to mafic granulite. The mafic granulite is locally associated with orthopyroxene-bearing tonalite (enderbite) in the northwest corner of the Wecho River area.
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Previously known mineral showings include iron formation-associated gold in the Wheeler-Germaine lakes area and quartz vein-hosted gold at Mosher Lake (see NORMIN Mineral Showings). New mineral deposit potential, identified in this study, includes extensive iron formation that is stratigraphically above a mafic
volcanic unit north-northwest of Mosher Lake (see photos) and continues into the Russell Lake area (see also Jackson, 2003, and the Snare River Project page). This volcanic unit contains a large, laterally continuous gossanous zone (10x250m) near the volcanic-sedimentary contact and appears similar in nature to VHMS-like occurrences.
Portions of the Wecho River area have been explored for diamondiferous kimberlite; none have been found to date. Mineral claim maps may be found on SID Viewer (a map tool created and maintained by Indian Affairs and Northern Development, Canada).
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Wecho River area, 1:100,000 scale preliminary bedrock geology maps of the northern and southern area (Open Reports 2004-003 & 2005-001) may be downloaded here.
In spring 2006, additional geochronology and geochemistry will be available for download. Keep checking this page for updates.
For related references click here
Associated Field Studies:
