Connection to the Earth Science Curriculum
Drift- underground tunnel where trammers and miners worked.
Stope- underground area where copper rock was removed.
Fault- In geology a fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement.
Fault line- the surface trace of a fault, the line of intersection between the fault plane and Earth’s surface.
Slip- The relative movement, including direction, of the land on either side of a fault
Figure 3. Diagram demonstrating the concepts of hanging wall and foot wall associated with a fault. http://serc.carleton.edu/quantskills/methods/quantlit/stressandstrain.html
Hanging wall- To geologist this means the block of land that sits above the fault; Miners define this as the rock above a mineral deposit in a mine (or where their lanterns would hang).
Foot wall- To geologist this means the block of land that sits below the fault; Miners define this as the rock underneath a mineral deposit in a mine (or where their feet would be).
Date Visited:July 13, 2011
Quincy Mine/ Hancock Fault
Figure 1.Quincy Mine Library of Congress, Prints and Photographs Division, HAER
One of the most celebrated and successful mine along the Keweenaw atop Quincy Hill. This mine produced 1.5 billion pounds of copper and paid out 30 million dollars in dividends for almost a century.
This mine was established in 1846 and did not pay a single dividend until almost 20 years later. Around 1857 the mine began to show progress and the rest is history.
In this EarthCache visitors will explore the Hancock fault and its effects on the copper miners at the Quincy Mine. This feature will be explored above ground at various points along the fault line or, for an optional closer look, at a below ground exposure during the Quincy Mine Tour.
Coordinates: N 47 o 08.013’ W 88 o 34.748,
Optional below ground view of the
Hancock fault from inside the Quincy Mine:
47o08.13’ N 88 o 34.28’ W
Figure 2. Google Earth Image of the Quincy Mine Area with the Hancock Fault crossing in red. Google Earth
Content Explanation and Images:
A fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other. This can happen fast, such as in an earthquake or it could happen slowly in the form of creep. During an earthquake, the rock on one side of the fault suddenly slips with respect to the other side. The surface of the faults can be horizontal or vertical or somewhere in between.
Faults were very important to miners in the 1900’s. These mines usually follow one mineral rich layer and faults disrupt the regular order of layers. When miners encountered a fault, they would have to find the mineral rich layer on the other side of the fault before they could mine more. A miner needs to know whether it’s a normal or reverse fault, or they won’t be able to find the mineral rich layer.
Earth scientist uses the angle of the fault with the dip and the direction of slip along the fault to classify it.
fault is a dip-slip fault in which the block above the fault has moved downward
relative to the block below. This type
of fault is usually found in the Western United States Basin and Range Province
and along oceanic ridge systems.
Figure 5. Source: Wikipedia.org/wiki/fault/geology
A thrust fault (figure 5) is a dip-slope fault in which the upper block, above the fault plane, moves up and over the lower block. This type of faulting is found in the areas of compression, such as regions where one plate is being subducted under another.
Figure 6. Source: Wikipedia.org/wiki/fault/geology
When the dip angle is shallow, a reverse fault (figure 6) is often described as a thrust fault.
Figure 7. Source: Wikipedia.org/wiki/fault/geology Figure 8. Source: Wikipedia.org/wiki/fault/geology
In a strike- slip fault occurs when two blocks slide past one another (figure 7). The San Andreas Fault in California is an example of a right lateral, strike-slip fault (figure 8).
As is often the case, standing on the surface at Quincy Mine you never see the Hancock fault itself but can sometimes detect the offset of the rock layers. Underground, inside the mine, you can see the fault exposed and classify its type.
The major fault of the region is the Keweenaw Fault. This is a thrust fault and it exposed the ~1.1 billion year old lava layers by raising them thousands of feet above which the much younger sandstone layer.
Above ground tour of the Hancock Fault:
Stop #1: N 47 o 08.013’ W 88 o 34.748- Quincy Mine Office
Stop #2: N 47 o 08.083’ W 88 o 34.565- Quincy Shaft No. 7 Broiler House with Jacobsville Sandstone blocks to South and Shaft No. 4 Hoist House to North
Stop #3: N 47 o 08.158’ W 88 o 34.367- Hoist House #2 and impressively large core sample
Stop #4: N 47 o 08.303’ W 88 o 33.990- Local neighborhood with houses built for the miners of Quincy.
Choose one of the four places you visited along the fault and give a few short sentences describing what you see. How was this location important to the operation of the mine? Notice that there is NO indication that the fault is below our feet. Describe something that is in your view.
Optional Logging Question:
Take the full Quincy Mine Tour to go nearly one-half mile straight into the side of the Quincy Hill just as the Copper Miners of the past. For information tours visit http://quincymine.com/ . Along the way you will pass an exposure of the Hancock fault at: 47o08.13’ N 88 o 34.28’ W
By looking at the fault line inside the mine what type of fault do you think it is and how do you know?
Quincy Historic Copper Mine Museum
Surface and Underground Tours
Quincy Mine Hoist Association
49750 US Highway 41, Hancock Mi. 49930
References and Citation:
Cornwall, Henry R. & Wright, James C. (1956). Geologic Map of the Laurium Quadrangle, Michigan.
Ormand, Carol & Baer, Eric. (May 28, 2010). Teaching Quantitative Skills in the Geosciences, Stress and Strain. Retrieved from http://serc.carleton.edu/quantskills/methods/quantlit/stressandstrain.html
Quincy mine hoist association. (2011). Retrieved from http://www. quincymine.com
Ralph, J. (2011). Retrieved from http://www.mindat.org
Usgs bc heritage. (2009). Retrieved from http://www.wells.entirety.ca/mining.htm
Wikimedia foundation, inc. . (2011, July). Retrieved from http://www.wikipedia.org/wiki/fault/_geology.htm
Figure 9. Geologic Map of Laurium Quadrangle, Michigan. Map displays both the Hancock and Keweenaw Faults. Authors: Cornwall & Write