GEOLOGICAL SETTING

The local geology of the iron deposits for the Roche Bay Magnetite Project has been described by Ursel (1968, 1969, and 1970), van Evendingen (1982), Ford (1982) and Harper (1984) and was summarized by Golder (2007) as presented here.  The Melville Peninsula is underlain largely by Precambrian rock of the Churchill Structural Province, with Paleozoic carbonate rocks occuring along the coast and eastward across Foxe Basin.  The Precambrian rocks are characterized by Archean granitic rocks with narrow elongated belts of Archean supracrustals cutting across the peninsula in a northeast direction.  These Archean belts consist of a suite of rocks known as the Prince Albert Group that contain sequences of metamorphosed sedimentary and volcanic rock (greenstones) exposed mainly in two belts on the Melville Peninsula and one belt southwest of Committee Bay.  The rocks are predominantly metavolcanics, which vary in composition from dark-coloured basaltic rocks through intermediate dacite to light-coloured rhyolite.  Three phases of diabase intrusions cut these older rocks.  Paleozoic rocks, exposed along the east coast as well as underlying the Foxe Basin consist of Cambrian-Ordovician massive micritic limestone, sandstone, dolomite, and dolomitic limestone.

 

 

 

LOCAL GEOLOGY

The Roche Bay Magnetite Project lies in the Churchill Province of the Canadian Shield.  The age of these rocks range from 1,580 to 2,900 million years before present.  Two periods of folding have occurred, one with a northwest-southeast axis, and the other with a northeast southwest axis.  Several sub-parallel belts of the Prince Albert Group illustrate these trends, with belts of the Prince Albert Group on the east and west sides of the Melville Peninsula showing convergence to the southwest.  It is believed that this defines a peninsula-wide fold, the nose of which was destroyed by granitic intrusion.  Another large scale fold may be present in the central portion of the peninsula, where the two Prince Albert belts on the east side of the peninsula converge and thicken appreciably.

The Roche Bay Magnetite Project encompasses five deposits of Algoma type Banded Iron Formation (BIF), known as Zones A (or Adler), B, C, D, and E.  These deposits are generally characterized by alternate bands of magnetite and silica, ranging in thickness from  one meter to one millimeter, strike lengths of 820 m (2,700 ft) to 4,200 m (14,000 ft), and widths of 120 m (400 ft) to 160 m (520 ft).

In the mapped grid areas, the outcrop pattern shows the regional NE-SW trend with nearly vertical dips and foliations.  Occasionally, the dip angles vary from near-vertical down to 60° to 70°.  Many faults and folds are present, but the vertically dipping nature of the bedding and foliation made structural interpretation difficult.
 

Banded Iron Formation outcropping.

 

DEPOSIT TYPE

The Roche Bay Magnetite Project has been classified as an Algoma type iron ore deposit or Banded Iron Formation (Golder, 2007).  This iron formation is characterized by well-laminated rock consisting predominantly of alternating magnetite and white quartz bands.  On fresh surfaces, this banding has been described as visually striking, clearly showing microstructures such as small folds and minor displacement.  Weathered surfaces are commonly steel black with occasional rusty zones.  The rocks have been re-crystallized but are still fine grained.  Quartz (re-crystallized chert) and magnetite are essential minerals that make up the iron formations; however, silicates such as amphiboles, micas, and chlorite, may form up to 40% of the rock.  Sulphide mineralization is dominated by pyrite and pyrrhotite with traces of chalcopyrite and arsenopyrite.  The thickness of each band in the iron formation ranges between 1 m to 0.001 m (1 mm) but is generally from 0.005 to 0.02 m (0.5 to 2 cm).  Also, there is often a thickness variation between adjacent bands. 

 

Reference
Golder Associates Ltd. 2007. Technical Report - Roche Bay Magnetite Project. Submitted to Advanced Explorations Inc. February 4, 2007. (filed on SEDAR June 4, 2007)

View the full report here. (pdf)