-
Large, cookie sheet (or shallow tray) at least 12 X 24 inches
- Approximately
5 pounds white mortar sand (or clean, very light colored silt)
-
Calcite sand (aquarium type) which is white, or same color as mortar
sand (or silt)
- Dilute Hydrochloric
Acid (approximately 10 %) in a dropper bottle
-
Piece of quarter inch rope approximately 12 inches long
1. Place
the rope on the cookie sheet near the center; align it with two opposite
corners.
2. Fill
the sheet with a smooth layer of mortar sand about one half inch deep.
3. Remember
where the rope is buried. This represents a blind (hidden) mineralized
vein.
4. Make
two calcite sand + mortar sand mixtures (total volume of each approx.
1 cup):
Mix A (calcite
rich): calcite sand (approx. 85 %) + mortar sand (approx. 15 %).
Mix B (sand
rich): calcite sand (approx. 25 %) + mortar sand (approx. 75 %).
Homogenize
each of the mixes by shaking and stirring.
5. First
create a model of a zone of strong carbonate alteration along the vein
using Mix A.
Carefully place a thin layer of Mix A (approx. 1/8 inch), about 2 inches
wide, which is centered along the vein.
6. Next
create a model of a zone with weak carbonate alteration, which lies
outboard and adjacent to the zone of strong carbonate alteration, using
Mix B. Carefully place a 1/8 inch layer of Mix B, about 2 inches
wide, on the left side of the “strong” zone. Likewise,
place a similar layer on the right side of the “strong”
zone.
7. Use something stiff and flat, like a book or board,
to press down on the entire area to make the entire surface of
the sand very smooth. Students should not be able to see the
difference in the zones and the “unaltered rock” (represented
by the mortar sand).
8. Next create a grid system for mapping on the surface
of the sand as follows:
a. Starting
in the lower left corner of the cookie sheet, make a mark with a marker
pen every inch along the left side of the sheet. Do the same
for the right side.
Starting in the lower left corner, make a mark every inch along the
bottom side. Do the
same for the top edge.
b.
Place a piece of masking tape about one inch long at each mark.
c.
Label each piece of tape along the left and right sides with the northing.
Do this
by assigning the lower left corner coordinates of 0 North and 0 East.
The 1” marks on the left and right sides will have a Northing
of 100 N. The 2” marks on the left and right sides will
have a Northing of 200 N. The 3” marks on the left and
right sides will have a Northing of 300 N. So on and so forth.
d.
Label each piece of tape along the bottom and top sides with the easting.
The 1” marks
on the bottom and top sides will have an Easting of 100 E. The
2” marks on
the bottom and top sides will have an Easting of 200 E. So on
and so forth.
e.
Take a piece of string and stretch it tightly across the the 100 N
marks so as to create a slight indentation in the sand forming a straight
line between the marks. Do this for each pair of marks to create
the rest of the lines of the grid.
1. Use the
dilute acid dropper bottle to test the “wall rock” (sand)
for carbonate alteration at the
site location with coordinates 100 N, 100 E. Do
this by dropping THREE DROPS ONLY
of HCl onto the sample site.Observe
the reaction for about a minute to evaluate the effervescence.
If the there is no reaction,
write a “0” on the map (Answer Sheet AS7). If there
is a slight reaction, write a“1”
on the map. If there is a strong reaction, write a “2”
on the map.
2. Test
the site location with coordinates of 100 N, 200 E. Record your
results on the map. Systematically continue to test each grid coordinate
on the entire model and record the results for each site location on
the map.
3. Sketch
a line on your map between unaltered areas and the zone of weak alteration.Sketch
a line on your map between the zone of weak alteration and the zone
of strong alteration.
4.
The budget for your exploration program only allows for excavating
two trenches, each with a length of 600 meters (6 inches on
the model). Draw two lines on your alteration map which represent
the proposed trench locations. Choose the locations of the trenches
carefully and strategically, and orient the trenches perpendicular
to the strike of the zone of strong alteration. Note the coordinates
for the endpoints of each trench.
5. Place a match stick or small stick a the corresponding
locations on the sand model.
6. Excavate your trenches along a line between the trench
endpoints.
