Property Geology – Dubenski

The following section is sourced from and is an update of the previous technical report on the Property by Dunbar and Kociumbas (2009).

“To date, the Property has only been systematically mapped by Noranda in 1973 (scale 1” to 200 ft), by the OGS in 1996 (scale 1:31,680) and finally by Avalon at a scale of 1:5,000 in 1997-1998” (Lengyel, 1998).

The Property is underlain by a series of felsic, mainly dacitic, tuffs with minor intercalated sediments such as argillites, sandstones and cherts and minor gabbroic intrusive rocks (Norontex, 1983). South of the Property, these gabbroic rocks appear in differentiated mafic sills alternating and concordant with felsic volcanic rocks.  No complete stratigraphic column has been established for the Property. Stratigraphy strikes between 105° to 110° and dips sub-vertically.

The following geological discussion incorporates observation from Avalon’s 1997-1998 mapping program, structural studies and their completed diamond drilling programs, and has been sourced directly from Campbell (1999a).

Geological mapping and structural studies provide evidence that the host rocks of the mineralization at the Shaft Zone, while extensively altered, have not been subjected to intense ductile (simple) shear, and that rocks outside the main Dubenski trend are essentially undeformed.  In addition, the strong fabric recognized on surface and in drill core at the Shaft Zone was generated by a regional compression event (end member simple shear) that post dates the dominant gold emplacement event. 

The geological mapping has resulted in some major changes to the initial geological interpretation of the Property, which includes an overall change in orientation of the stratigraphy from east-west to north-northeast in most areas outside the main Dubenski trend.

The majority of the Property is underlain by two distinct formations of felsic volcanic rocks: the Kakagi Lake Formation; and a series of overlying finer grained felsic volcanic rocks, the Cedartree Lake Formation.  The lower Kakagi Lake Formation rests conformably on a basal sequence of mafic volcanic rocks which comprise the dominant bedrock of the adjacent HLM property, contiguous to the west of the Property.

The Kakagi Lake Formation is defined mainly by a coarse pyroclastic unit, predominantly a coarse tuff breccia consisting of large blocks of basaltic to dacitic composition, within a tuffaceous matrix of intermediate to felsic composition.  This unit comprises most of the western portion of the Property.  The variability in block size and composition strongly suggests the origin is slump breccias, as opposed to true vent pyroclastic agglomerates.  The geological environment suggested by these rock types is indicative of great instability in the volcanic stratigraphy during formation, possibly regional subsidence contemporaneous with volcanism.  Several thin horizons of fine-grained tuff occur intercalated within the coarse units and could potentially be used as stratigraphic marker horizons, at least over short distances.

Overlying the Kakagi pyroclastics are tuffaceous sediments, cherts, tuffs, and minor dacitic flows of the Cedartree Lake Formation.  These are felsic, probably dacitic to rhyolitic in chemical composition, and have a high proportion of cherty beds.  Mapping indicates that these rocks underlie the East Cedartree property and the eastern half of the Property.  Good exposures occur all along the east shore of Cedartree Lake, and the south shore of Flint Lake.  Individual units range from massive tuff to crystal tuff, fine grained pyroclastics with abundant cherty sediments, reworked volcaniclastics, and lesser lapilli tuff.  Primary features such as graded bedding and layering in tuffaceous units, flame structures and millimetre scale lamina in cherty units is clearly evident.  The general trend of stratigraphy is in the order of 010° to 040° azimuth, with moderate dips to the east.  The lack of penetrative foliation or any small scale folding or crenulation attests to the fact that these rocks are essentially undeformed to within 200 m of the main Dubenski trend.

The contact between these two regional formations, labelled as a transition zone on the geological plan map, transects the Property along the northeastern end of Cedartree Lake in a north-northeastern direction.  Its actual location through the Property is partially interpreted on diamond drill results. Current evidence indicates the Shaft Zone is spatially associated with this contact.

A fold structure located in the central portion of the Property has been interpreted and is based on limited geological information at this time.

Several mafic sill intrusions occur with the volcanic stratigraphy, and may belong to the Kakagi sill intrusive event.  One occurrence of gabbro occurs in the central portion of the Property.  Smaller occurrences are commonly noted throughout the stratigraphy.  The sills are composed of subhedral pyroxene and / or hornblende phenocryst phases, set in a fine-grained ground mass of plagioclase and mafic minerals.  Their morphology can be quite variable within the stratigraphy, as noted at the stripped outcrop at the junction of the main road with the Shaft Zone trail.  Here a small intrusion can be seen exhibiting both conformable and cross-cutting relationships with the enclosing host rocks.  Some of these mafic intrusions are reflected geophysically as magnetic highs, while others are non-magnetic, suggesting two different intrusive phases.