4 Interesting Road Cuts
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4 Interesting Road Cuts
of the Mississippi Valley Mineral District

OEDG Summer 2009



Silver Creek Cliff / Tunnel
- Highway 61
Anorthosite
- Highway 61
Tonalite
- Gunflint Trail Road
Pillow Basalts
- west of Ely
Click here to view lesson plans that were inspired by the field trip.

Location:
To find the Silver Creek Cliff tunnel, head Northeast from Duluth on route 61. Go through Two Harbors an approximately 5-7 miles northeast to find the tunnel. (Lat: 47o 4' 13'', Lon: -91o 35' 27'')
Silver Creek Tunnel
Silver Creek Hydrothermal Alteration
Silver Creek Cliff Tunnel, notice the two very distinct bands of rock. The lighter orange/pink rock is granophere
(a feldspar rich volcanic rock) that was deposited first and then covered by a volcanic gabbro. If you look at the area where they meet you can see the hydrothermal alteration where the
granophere was cooked by the thick diabasic sill.
Hydrothermal Alteration
Hydrothermal Alteration close up


Click on the pictures above to see a larger version.
Click here to view a pdf flyer from the CNA Engineers about the tunnel
Photos contributed by OEDG 2009 participants.