1. The following layout of boreholes has been drilled in an area of Platinum Group
Metals (PGM) mineralization.
1.1 Calculate the grade at point T (Figure 1) using a spherical semi-variogram model
with a nugget effect of 0.2 (g/t)2, a partial sill : ·· ·;.·. ·i : and a = 175 m as shown in
Figure 2
[18]
1.2 Comment on the weights assigned to the four samples
[6]
1.3 Can sample M be used with the other four samples to calculate the grade at point
T? Why? Will the estimation error (kriging variance) increase or decrease if sample M
is used? Why?
[2,2, 2]
1.4 Distinguish between a geostatistical and a statistical variance. Explain which of
the two is appropriate for ore deposit mining.
[5]
1.5. Briefly explain the advantages and disadvantages of grade capping in gold
deposits.
[5]
360 l lz4h s:34 gtt'
350
1 ~- , -1 ,--I
340
I 1- I
330
I
II
Z3 = 5.84 git
• 320
I IrI
310
30D
29D
I
I
I
I
I
I
V
I
I
t
41
I
2&0
I•
_I
II
L
I
II I
ii-Z1 = 5.26 g/1
,. I
I
j I:I
·1
I
iI
270
260
.J,~.I~
I Z2.= 9.06git I
.---,------.--__,___1,___, -,----l"---<._.1_._I
II
..-.L..j-J M
79D
84D
890
940
Figure 1: Borehole layout
2