The aim of this activity is to acquire a better understanding of mafic-ultramafic intrusive bodies and their associated magmatic events, discover new intrusive bodies, and evaluate their Ni-Cu-PGE metallogenic potential. In order to accomplish this we will compile existing geological maps and assessment work with new magnetic and gravity maps, satellite imagery, and digital elevation models in order to define magmatic environments and possible structural controls for the localization of magmatic sulphides. This information will be compatible with GIS systems and enhanced with embedded areomagnetic and ground gravity surveys, satellite imagery, and maps of selected intrusive sites and mineral occurrences.

Additionally, 282 rock samples were collected from 67 sites (see figure below). The majority of samples were collected from: Franklin sills (110), Booth River Complex (67), Morel sills (8), Gumbo Lake nickel showing, Coppermine volcanics in the Bathurst Inlet area, High Lake Belt, Recluse and Epworth formations (Paleoproterozoic), Rae Group (Neoproterozoic), and along the Coronation Gulf. Fieldwork was conducted during the summer of 2003 in collaboration with Anglo American Exploration (Canada Ltd).

The image below is a LandSat TM 4-5 RGB Band 742 mosaic (WGS 84 Zone 12) of Northern Slave Province and environs, showing the location of the 67 sites ( red dots) visited during the summer field program 2003.

Franklin Magmatism

Franklin sills were systematically sampled along Coronation Gulf and inland. The collected information will be used to produce a mineralogical, lithogeochemical and tracer isotope database and to compile chemostratigraphic profiles through selected Franklin intrusions in conjunction with a new map of the Franklin magmatic environment along Coronation Gulf.

The image below is of a Franklin sill intruding Archean gneiss NW of Bathurst Inlet.

The next image is of a Franklin sill resting on top of arenaceous Recluse Formation (Paleoproterozoic) sediments in the Tree River Fold Belt. Note the recessive weathering beneath the chilled intrusive contact of the sill. This exposure of the sill is approx. 15 m thick.

A number of sites where Franklin sills intrude sedimentary rocks of the Rae Group (Neoproterozoic) were sampled along Coronation Gulf from Tree River to an area 60 km west of Kugluktuk. The image below depicts a Franklin sill intruding a red bed shale-sandstone sequence near the top of the Rae Group west of Kugluktuk. The sill is fractionated, olivine-enriched and shows signs of local contamination.

Sills intruding Coppermine basalts in the Bathurst Inlet bay area were also sampled. The sills were systematically sampled from the chilled basal contact upwards at regular intervals. In order to assess geochemical vectors in mineral exploration and Nd-Sr-Pb-isotopic variations the influence of these different country rock environments must be ascertained. Ten samples from these environments have been submitted for Nd-Sr-Pb isotope analyses.

The image below shows a Franklin sill (tan) intruding Coppermine basalts (grey) or Ekalulia Formation along Coronation Gulf, Bathurst Inlet. View looking north towards towards ice bound Coronation Gulf and Victoria Island. Note the terracing of the landscape due to the abundance of sills.

One of the most striking features of the Franklin sills is their great lateral continuity. A sill at the base of the Rae Group could be followed along strike from east of the mouth of Tree River to the Kugluktuk area to the west for approximately 200 kilometers. Such lateral continuity could give rise to magmatic "flow-through channels" similar to those found in the "gabbro-diabase" sills in the Noril'sk region of Russia. In addition to the lateral continuity of these intrusive bodies; their frequency and volume within the Archean, Paleo- and Mesoproterozoic strata records a world-class magmatic event at 718-723 Ma. Sills within the Archean and Paleoproterozoic appear to be massive and undifferentiated and lacking in olivine, whereas those in the Mesoproterozoic rocks around Kugluktuk appear to be more olivine-rich and demonstrate in situ differentiation and local signs of crustal contamination.

One of the most effective tools for finding, following and studying sills is with aid of digital elevation models (DEM). The image below displays a regional digital elevation model. Note the distinctive topographic expression of these ridge forming tabular bodies (sills), their laterally extensive nature, and surrounding lineaments. (Lambert Conformal Conic NAD 83 projection & datum).

Booth River Complex

The Booth River Complex is a large layered mafic-ultramafic intrusion comprising poorly exposed northern and southern limbs that protrude along the margins of the Kilohigok sedimentary basin west of the Bathurst Inlet fault. Results of this work will be used to generate both a new map and a lithogeochemical, mineralogical, paleomagnetic and geochronology database for the Booth River Complex. The DEM (see figure below) illustrates the pronounced topographic effects associated with the basin. The white areas along the northern and southern margins of the basin represent the best exposed portions (limbs) of the intrusive complex. The magnetic and gravity geophysical expressions of this complex are also outlined on the DEM below: their association with the limits of the sedimentary basin, and the presence of similar looking rocks near the west end of the basin (east of Lupin) demonstrate that this is a very large mafic-ultramafic intrusive complex.

In the DEM below, note the distinctive topographic and recessive nature of the Kiliohogok sedimentary basin, and the pronounced topographic break associated with the Bathurst Inlet fault. The exposed portions of the Booth River Complex are represented by the white areas flanking the margin of the basin to the north and south. The gravity and magnetic anomaly outlines attributed to the complex are also shown.

One of the unexpected features associated with this complex is the widespread distribution of magmatic sulphides. Next to the Muskox intrusion this is the best mineralized mafic-ultramafic complex in the western Arctic. Patchy magmatic sulphides occur in taxitic norites and gabbronorites (see below) along the margin of the intrusion and impart a gossanous appearance to the surface exposures. Note the orange gossanous areas which generally have a taxitic texture.

Mineralized anorthositic gabbro with a distinctive iron-stained gossanous surface occurs near the transition between these two zones. Localized patches and stratabound lenses of magmatic sulphides (comprising up to 8% disseminated sulphide) occur from this zone to near the base of the oxide-rich gabbronorite and ultramafic rock zone. Sulphide mineralization in the form of disseminations, blebs (0.5 to 1.0 cm in diameter) and pods (5-10 cm in diameter) comprising up to 10% of the rock volume occur throughout the macro layered oxide-rich gabbronorite and ultramafic rock zone and impart a gossanous appearance to the outcrops. Note the distinctive iron stained appearance of the mineralized outcrops (see below) and the distinctive stepping or terracing of the outcrops due to cumulate macro-layering. Photo looking southwest towards Booth River.

Some of the most pronounced gossans are associated with sulphidic ilmenite-rich layers near the top of the oxide-rich gabbronorite and ultramafic rock zones. In the image below the person is standing on one of the more gossanous sulphide-rich horizons.

The image below is a down-dip expression of the mineralized stratbound horizon shown above.

Although most of the mafic and ultramafic rocks in this upper zone contain magmatic sulphides and are gossanous, many of the gossans result from weathered Fe-Ti oxides. In the image below, ocherous gossans are associated with sulphidic Fe-Ti oxide concentrations near the top of the oxide-rich gabbronorite and ultramafic rock zone. This horizon is strikingly similar to the ilmenite-rich oxide layers found near the top of the upper zone of the Bushveld Complex.

Gumbo Lake Nickel showing

High Lake Belt