VISITS FOLLOWING THE NEW HIGHWAY 73 in SOUTH QUEBEC
During the fall of 2006, I saw a grand opportunity to see what was in the woods in the region east of Thetford Mines. A new 4 lane highway passing through Quebec City and entering the state of Maine was underway. Any time a major highway traverses the terrain, each road cut is a window into the local geology. Often if you are there at the right time, treasures are opened up and then buried or crushed forever. I take it as my responsibility to record and save the minerals.
The geology in this region was formed during the Taconic orogeny about 440 million years ago (according to the latest theory) when two continents slowly collided forming the subduction zone along a line now called Baie Verte Line, which locally is expressed as the Saint Josph fault. There was much shuffling of wedges of crust, olistostromes, ocean basin sediments pushed together in this area making it very complicated. Rock to the north west of this represents the passive margin of the ancient continent of Laurentia. This is called the Humber Zone. The Rosaire formation is a part of this. The rock to the southeast of this fault represents the Dunnage Zone which is composed of ophiolites, ocean sediments, volcanic island arcs being the last vestiges of the Japetus Ocean. The ancient ocean was closing at the subduction zone, which follows the Baie Verte Line. The whole Japetus Ocean at this Ordovician time was being squeezed into this suture.
Now 440 million years later this highway was cutting through this area so I figured it may open up something interesting . The Saint Joseph fault runs northeast south west near the area I was looking at. The rock to the northwest is metasedimentary rock of the Rosaire formation (slates , metasandstone, quartzites) which often is exposed with lots of quartz veins. If you follow the strike NE from Black Lake the ophiolitic rocks and related ocean volcanic of the Saint Daniel mélange and Caldwell formation have a potential for copper, nickel, zinc, chrome and other mineralization. So I figured it was worth a visit.

When I went looking for the construction I drove from Therford Mines on RT 112 and crossed the Chaudiere River at Sainte Marie and followed the route 173 south until the Calway Rd. I ended taking this road because I knew the new Highway 73 was NE and parallel to the old Rt 173. Heading Northeast for about 1 mile it brought me to the new Highway 73. This was my first location. A concrete over pass was already in construction and the path of the Highway was deforested and already graded with blasting already in progress. Hiking south east on the new highway 73 brought me to a volcanic rock corresponding to the Caldwell formation. You could see the rock was basalt like, colored by epidote and having 5-10 mm vesicles filled with minerals.
Heading north west the rock changed to a metasedimentary quartzite like rock with quartz veins, most likely a part of the Caldwell formation.

I went there hoping the quartz veins would be opened up, since I already found a few limpid xls up to 3cm in the roadcuts in the existing Route 73 north of RT 112 toward Saint Marie. These cut were always full of quartz veins running across the layering, but that was probably the Saint Rossaire formation.
Sure enough my first find greated me when I walked up the newly excavated bed north from Calway Rd about 1000 feet from where I parked my car there. I saw a light gray shale like rock with chucks of milky quartz laying about. I found a very nice calcite xl just laying in the rubble. Good sign! And there was a clear quartz crystal embedded in it. Yes! That whetted my appetite. So the search was on for quartz veins. When I saw how much quartz was laying at the bottom a a fresh road cut, it told me something. I followed it to the source and found myself a diagonal vein of milky quartz around 1 foot thick with evidence of pocketing in the white chuncks laying around. I worked it with my sledge, some chisels and pry bars and found a lot of light gray clay along the hanging wall of the vein and yes it was a pocket! Clay ,gooey clay, is always a good sign. Pockets are often filled with this. I started pulling out crystals. Some must have been 6” long or more but all broken in shards. The clay also grading into dark green chloritic clay.
I must have had 80 lbs of clay in my back sack. It is better to keep the crystals in clay to protect them, so I decided to take as much as I could to the car and latter hose it down and work out the crystals. Later at home I scubbed out all with a hose in a 5 gallon bucket and use of a screen, toothbrush, toothpicks and sliced fingers. I was disappointed that most of the big ones were already fractured. It seemed that the crystals were not fractured recently, since some crystals had regrowth on the fractured surfaces. So that consoled me. They probably were cracked by tectonic activity a long time before the blasting. However I found a few keepers which I posted under Saint Joseph de Beauce.
In later trips to follow the construction I followed a parallel road, Rang l’Assumption North west along the new RT 73. There were construction roads where construction trucks were dumping quartz for fill. I was able to pick up some crystallized quartz along the sides that was being used as just fill. Also a new housing development off of Rang L’assumption was blasting into the rock and opened a veins with some quartz xls exhibited nice forest green chlorite inclusions. I found one piece laying in the fill on the side of one of the new roads with albite xls epitactic on the chlorite included quartz. I had to notice a similarity to the RT 55 Windsor QC quartz.
When I walked southeast south of Calway Rd on the new highway 73 there was this road cut about ½ mile on the left showing the volcanic rock (Caldwell). The rock had been blasted and piled in boulders against the road cut. The smaller refuse rock was graded into the basement of the new highway. When I walked around I noticed the rock had a distinct dark greenish color not like the rock on the north side of Calway Rd. I began noticing that there was a mauve colored mineral under my feet. Now that is unusual, I thought. When I followed it to the source I saw the boulders had veins of mauve axinite and calcite up to 1” thick. After I saw the axe shaped bladed crystals in the volcanic rock environment it was pretty obvious. I went to work on these and found some xls encased in the calcite, which I later liberated with the help of Muriatic acid. The axinite proved to be the best find here. I found some interesting banded jasper or chalcedony laying about, a little chalcopyrite with green staining, some pinkish unidentified xls (perhaps an orthoclase but not sure), and a cellular quartz with epidote and small stilbite like xls.
The construction is supposed to continue South east ward toward Saint George de Beauce and late Maine. The plan is completion in 2010. Further down the line the highway begins entering dark shale of the Beauceville formation (Magog Group), which hasn’t shown much in the past. There are possible intrusions of diorites and quartz that my contain Au.
May 3rd, 2008 I got out again to see the work further south on the Route 73. The section between Route 276 is open to traffic all the way south to Rue de Golf in Beauceville. To begin, where the Route 73 intersects Route 276, There is an active quarry, Beton Saint Joseph, which has its entrance just along side the entrance to Route 73. This has produced some nice quartz crystals according to some Quebec collectors. It is owned by the Sintra Inc. and one needs permission to enter. I noticed quartz veins with evidence of pockets in the RT 276 road cut near here.
I drove on to the new Route 73 and took a ride to the next exit and present end at Rue de Golf (Road). Here I found a service road cut along a major road cut on Rt 73 that seems to be in the Beauceville formation. It is a black graphitic shale in almost a 90 degree bedding plane. At the end of this service road it turned into a cul de sac, where there was a pile of this reddish rock. There was calcite veins with green chloritic areas, but no signs of open areas or crystals. Looking at the local geological bedrock map makes me think this is part of the Saint Daniel formation, which was an olistostrome. An olistostrome is formed in the ancient ocean by a chaotic assembly of the local ocean sediments and volcanic rock slumped down ward by gravity forming a breccias like assemblage as the ocean is finally closing.
But for collecting, it didn’t look promising so I moved on. I walked down to the bridge crossing Riviere des Plantes. I was under it look at how I could ford the river since there was fill rock on the other side. The fill rock I examined on the south side was just uninteresting shale like rock with a lot a red slate shale. This my have been from the Caldwell formation which has purplish-red an green feldspathic sandstone and slates. But no sign of mineralization. Darn! Further west along the old highway 173, at the Riviere des Plantes there is a pit exposing serpentinite that I would like to get permission to examine one of these days. This slice of ophiolite is along the subduction line upstrike form Thetford Mines Ophiolite complex.
Well I headed back onto the new 73 north until I got back to the Rt 276 exit. Along the way I stopped to photo some of the road cuts. North of the Riviere des Plants bridge there was some serpentinite exposed in a road cut. That fit with the geologic maps. Further one the rock at the border of Beauceville and Saint Joseph was cut by a high road cut. I remember collecting here in 2006. The rock is probably part of the Caldwell formation. Again it appears to be a metasandstone. You can see someone worked on the alpine veins here. I was one of them, but I had to wonder what did they get out after I was there. Further north the road cut showing the Caldwell volcanic rock shows. But not much left to see. Mostly backfilled now and all the material is buried for the moment.
After the Highway trip I decided to head north on Calway Rd. to the Calway Quarry. It was not a productive visit like last time. There wasn’t much new material moved since last time.
I plan to keep an eye on the further extension of RT 73 south past Beauceville and see if I can get permission to enter the Beton Saint Joseph Quarry. Beyond that there doesn’t seem to be any fresh material in the area.

MAY 9th TRIP TO SAINT MARIE DE BEAUCE ROUTE 73

May 9th I made a visit to Route 73 in the Saint Marie area. I had a dentist appointment which was canceled in the village. I didn’t get my tooth pulled, and I already had taken off work. Finally a sunny spring day in Quebec. I had to get out and see what was around. I decided to start at Carter Rd, where there is an entrance to Route 73. There was a housing development in construction that was moving some rock.


I had been here before and I though there might be some decent quartz crystals. The rock according to the geological map is Saint Roch Group of formations which is Cambrian. The rock appears to be a greenish slate/ phyllite trasversed by veins. The veins are honeycombed with cavities filled with a black dirt. In some places the same voids are filled with calcite which looks like it was dissolved to form the dirt filled cavities.
I moved south along a road parallel to Rt 73, called Rang Saint Gabriel Sud, that near a stream and a water purification plant.
At this point I remember I was adjacent to the road cut on Rt 73 that produced larger veins a few years ago that did have some nice clear quartz xls up to 1 inch. This rock more like a quartzite and part of the Saint Rosaire formation which seems to form veins more likely to have well formed quartz xls. I broke a few rocks around the side of the Rang here and there was possiblilties but not enough exposed material. I did find on rock with large tan calcite cleavages.
Later I moved south on the Rang and ended at Rt 112. I decided to take a drive north eastward about 3 kilometers to Saint Ange and saw there was a housing development bulldozing rock there. The rock here again was an exposure of the Saint Roch group, a greenish slate/ phyllite. There were again a lot of quartz veins, but not much crystallization.





References:
Geologie des Regions de Saint-Victoir et de Thetford Mines (moitie est)
Pierre St-Julien

Structural Style and Tectonostratigraphy of the external-internal Humber Zone Boundary
in the Sainte-Marie-Saint Sylvestre area, Quebec Appalachians
Geological Survey of Canada Current Research 2001-D13
Sebastien Castonguay, Yvon Lemieux, Bertrand Marcotte and Alain Tremblay

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