Question

Monazite is a Ce phosphate mineral that commonly contains abundant rare earth elements (REE), metals that have many high-tech applications. Economically viable lag deposits of monazite can occur in some sandstone. You’ve been hired to evaluate a potential deposit. On a relatively level ground surface in the desert, the outcrop width (measured perpendicular to strike) of a monazite-bearing sandstone unit is 23 m. The sandstone has an orientation of 308, 32 (strike, dip), as measured in outcrop. In this area, it is known that the sandstone units most likely to contain useful amounts of monazite are greater than 10 m thick. (20 points)

      a. Is the true thickness of the sandstone unit greater than 10 m? Determine the true thickness. (4 pts)

      b. You must verify the thickness of the sandstone beneath your client’s property, located near the outcrop mentioned above, by drilling a vertical hole which passes through the unit. Assuming the orientation is constant, over what vertical distance would you expect to encounter sandstone if the thickness is unchanged? (4 pts)

      c. If a drill hole was located 150 m along 038 from an outcrop that contains the upper contact of the sandstone bed, how deep will the hole have to be to cross both contacts (top and bottom) of the bed? (5 pts)

      d. You’ve mapped a vertical basalt dike near the sandstone to be about 12 m wide on flat ground. The heat given off from the cooling dike may have metamorphosed the sandstone, increasing the cost of drilling. In order to calculate the amount of heat given off we need to know the true thickness of the dike. What is the true thickness? (3 pts)

      e. An alternate site for the drill hole is 180 m due east (090) of the outcrop mentioned in c. above. How deep will the hole have to be to cross the full thickness of the bed at this site? (4 pts)

Answer 1