Sault Prospector's field trip to the Eagle River Mine,
River Gold Mines Ltd., Mishisbishu Lake Area, Wawa

Once again the Sault & District Prospector's Association had a great fieldtrip this year, 
this time into the wilds of the Mishibishu Lake area. 

A little bit of history....
The Mishibishu Lake area was quite active during the late 1980's with much of the greenstone belt staked and actively explored for gold. As a result of the exploration effort, several gold deposits were discovered. The Magnacon deposit was brought into production in 1989 and a gold mill built to process the ore. Just to the west of Magnacon, the Mishi deposit was delineated and a small open pit was developed. Fifteen kilometres south of the Magnacon and Mishi deposits, the Eagle River deposit was discovered and developed. In the early 1990's the price of gold floundered and the mines and mill were shut down.

Photo 2: SDPA vehicle caravan waiting at the River Gold Mines Ltd. gate

 In 1994, River Gold Mines Limited was created to consolidate ownership and bring the Eagle River Mine into production. Most recently, River Gold has brought the Mishi deposit into production and has dewatered the Magnacon Mine with the intent of increasing additional ore reserves.

On our arrival at the mine site we were met by George Mannard, Vice President, Exploration for River Gold Mines Ltd. We circled around the drafting table while George gave us a detailed overview of the mineralized zones, where we were going, and the kinds of assays that had been found within the areas under development.

We then headed off to the core shack where both George and Charlie gave an overview of the geology and the exploration being done on their large property holdings. The drill core on display was a section through the new 818 Zone

Notably, the mineralized shear zone hosting the Eagle River gold deposit extends well past the east and west ends of the diorite stock - into the greenstones. Some interesting gold prospects have been discovered, including a mineralized iron formation to the west and gold-bearing quartz veins to the east.

General Geology and Location Map

Reference: River Gold Mines Ltd. 2003 Annual Report

The Eagle River orebody consists of a series of near vertically dipping quartz veins and lenses hosted mostly in a sheared diorite host rock. The ore zones consist of thicker sections of veins and lenses which plunge steeply to the east. The veins have been traced over a strike length of 2.5 kilometres and to a depth of 650 metres.

Typically the vein-type ore consists of quartz veins separated by schistose sections of sheared diorite. Sulphide minerals generally occur along the quartz-schist contact and these appear to contain the higher grades of gold.

Most recently a new ore type was discovered, referred to as breccia-type ore, consisting of variable-size fragments of sheared and mineralized vein material contained within a quartz-calcite-Kfeldspar matrix. The mineralized breccia has only been found in the lower levels of the deposit and appears to occur as breccia veins in close association with the main vein-type ore. 

One would have thought that we were about to enter the Sudbury Neutrino Observatory after donning our white coveralls and all the underground paraphernalia. After posing for a few pictures, we stepped into a couple of rather comfortable U/G personnel vehicles and headed down the ramp. 

For some of the SDPA members it was their first time underground (Vivienne counted the number of turns the vehicles took and in which direction). As soon as we were out of the trucks everyone took to the U/G like ducks to water - and there was lots of it! At the 540 metre level the mine is about 350 metres below Lake Superior.

 Photo 7: Loading up into the U/G transport vehicles

The 818 Zone is dominated by breccia-type ore, containing fragments ranging from a few centimetres in size up to a metre. Fragments at various sizes have a 'splintered' appearance, having been broken along their length or shear fabric and then variably rotated. These zones of brecciation are also characterized by the presence of disseminated epidote alteration which is noted in drill core as the wall rocks and the mineralized breccia are intersected.

Other breccia veins were noted within the 818 Zone consisting of wall rock fragments contained in a predominantly calcite matrix with associated hematite-rich seams. This secondary breccia type forms large cavities and its relationship to the mineralized breccia-type ore is uncertain (Keweenawan age?). 

High-grade intersections of 146 g/t over 4.7 metres and 50 g/t over 2.3 metres in the 650 Zone attest to the continued richness of the gold mineralization with depth and the longer term viability of this gold mine.

Here we had an opportunity to see how it all fits together. The folded and thickened quartz veins and lenses are contained within a shear zone which occurs at the contact between diorite and mafic volcanics. The 650 Zone is at the eastern edge of the diorite stock which hosts most of the vein system.

It is possible to walk from south to north through unsheared mafic volcanic rocks, to sheared mafic volcanic, folded quartz veins with sheared slivers of diorite and/or mafic volcanic, to sheared diorite and then unsheared diorite. A good lesson in geology!

After such an 'exhaustive' day in the field, George Mannard invited us to share in some refreshments at the Eagles Nest. This is the location at the top of the hill where the original drill program was completed by Hemlo Gold Mines. Much of the drill core is still at the site. The small cottage has a spectacular view of Lake Superior with Miichipicoten Island in the distance.

Folks may not remember, but the nearest comparison to the Eagle River gold deposit both in size and style of mineralization in the Wawa area was the Renabie Mine. The Renabie produced over 1 million ounces during its lifetime which spanned over 25 years.

With the hard work and dedication evident in River Gold's mining and exploration team and the continuing resilience of the ore body, we can expect to see River Gold Mines Ltd. live long and prosper.

Vivienne in full regalia

Cliff -  final adjustments

Bud & Son

 The Newcomers

George assessing the footwear

Verdun & Mike ready-to-go

John - first time underground

Viv - cheering the Flames

.

Acknowledgements:
Thanks to all the folks who helped out in giving the SDPA a great surface and underground tour and to all their hospitality, especially: 

George Mannard           Vice President, Exploration
John Plecash                  Chief Geologist
Charlie Hartely               Exploration Geologist
Joe Wilkins                    Mine Captain

Eagle River Mine
River Gold Mines Limited
www.rivergoldmine.com