Summary:
The quartzite on the Silicon Ridge Property is of the metamorphic type, of probable sedimentary origin, and occurs as large-amplitude folds formed in response to multiple episodes of folding. The controlling factors for the formation of the quartzite and for the presence of internal sub-units and structures are lithological (sediment precursor) and structural (recrystallization and formation of folds).
The Property area is located in the high-grade metamorphic terranes of the Grenville Province of the Canadian Shield. At least four ductile and one brittle deformation events have affected the area.
The Property hosts several map-scale sequences that host high purity quartzites. Rogue selected two of these sequences (“G” and “H”) as their primary drilling targets for potential further development. The “G” unit, hosting the South West and North East zones, trends SW-NE through the central portion of the Property, and the “H” unit, hosting the Centre North zone, is approximately 250 m to the north, in the northern sector of the Property. The width of the “G” quartzite unit varies along strike, reaching a maximum of 260 m, with an average thickness of 150 m.
The quartzite on the Property is generally coarse-grained, massive and locally fractured. It variably contains traces of biotite, muscovite, hematite, magnetite, ilmenite, fuchsite, rutile, and clusters of sillimanite with pyrite were occasionally observed. The different impurities cause the changes of colour in the quartzite. In the case of iron, fine hematite or magnetite crystals impart a pervasive pink or red colour to the quartzite, and iron staining (surface coating) is observed along fractures and fractured contact zones that promote water circulation.
The quartzite exhibits internal zones distinguished by their colour or by sheared zones that represent fairly continuous bands within the deposit, and the relative silica content within these bands is controlled by and inversely proportional to the impurities hosted in the gangue minerals. These bands of different tenors in impurities have been interpreted to have responded to different controlling factors:
- Lithological: precursor’s original composition (protolith);
- Structural, indicated by:
- The fact that these bands are folded sympathetic with the quartzite unit, rather than cross-cutting (synthetic folds with respect to the geometry of the large-scale fold in the quartzite unit);
- Observed remobilization of mobile elements during metamorphism;
- Evidence of late migration of iron along the fracture network.
ANZAPLAN (2016) reports a preliminary mineralogical investigation of three high silica quartzite specimens selected by differing colours, and the following features were described. The quartzite is comprised of isometric or elongate quartz crystals that reach a size of more than 1 cm. The complex regional geological/structural history has been recorded by the quartzite, as evidenced by features such as dynamic recrystallization and internal crystal deformation observed in these two thin sections. Films of hematite, imparting a reddish colour, of approximately 50 microns in size occur along grain boundaries and are interpreted to indicate primary sedimentary layering. In addition, the roundness of the zircons suggests a sedimentary precursor. The presence of muscovite flakes (occasionally altered), sillimanite prisms (occasionally altered to clay) and common rutile needles were observed. Abundant small fluid inclusions less than 20 microns were detected along annealed fractures and were interpreted to impart the whitish colour.