Sillitoe, 2010 - Avala Resources Ltd.

Sillitoe, 2010
KUDD-­‐034
What part of a porphyry system might the deep
Kuruga drill hole KUDD-­‐034 have encountered?
From top to ~462 m depth, the drill hole passed through rocks showing
the typical hydrothermal silicate altera@on assemblage characteris@c of
a porphyry Cu hydrothermal system.
However, there was a remarkable lack of quartz veins as well as Cu-­‐Fe
sulfide minerals. The overall grade is likely low, perhaps in the 0.1+% Cu
from the serici@c zone through the K silicate (potassic) altera@on zone.
Pyrite where present is replacing Fe-­‐bearing minerals (2 nd bio@te and
magne@te) that form a pervasive replacement of mafic phases as well
as veins
Pyrite is also associated with anhydrite.
The transi@on in the drill core from intensely altered to almost
unaltered is very sharp (over 5 cm); sharp lateral gradients are expected
as hydrothermal fluid flow on the margins will be largely ver@cal and in
the case of the drill hole based on grain boundary diffusion due to the
lack of significant veins.
Taking all the observa@ons suggests that the drill hole KUDD-­‐034 may
have just cut the pervasive altera@on that extend outside the Cu shell
(dashed line on cartoon to lej).