progress of deep hole, page-12

kmuirhead - in reply to your comment below ..

"f) To me, the concept of a big fat mother load at
a depth of 2000 metres defies physical logic.
To generate such a lode would require that
the 2000 metres of rock above it would need to be
uplifted to create the space to contain this load.
Logically, the molten quartz containing the gold,
has been forced up faults or zones of weakness from
the upper mantle ~40km down. Thus, I would expect
them to find that there are seams of gold down
to 2000m but so what."

i dont know about the motherlode either -
Without knowing the possibility of this occurrence in CTO's system and setting - it is quite possible for lots of gold to be contained in the sediments next to dyke - known as "contact" zones.

The mechanics are roughly as follows -
All Dykes originate deep down in the magma chambers and were forced to the surface over time by orogenic forces.
As these dykes ploughed vertically through the sediments they may have created areas of structural weakness in immediately adjacent sediments i.e. areas of least resistance - and these areas may have provided pockets for the gold that was forced up under pressure to deposit into.

cohen's reef is an example of a sediment hosted gold reef next to a long dyke body. It was a prolific and famous reef in Victoria.

I'm not sure if this occurrence can happen as you say under the dyke body or indeed does happen in the case of CTO, but it's interesting following the system down to see how far it goes and what is actually happening down there.

Sediment hosting may add significantly more gold - that's if it happens in this system and there's been no mention until now, but i wonder if it has been explored for all the same?

when we say the temperature increases by 1 degree per 100 metres - what is the surrounding temperature say 100 metres underground ? - it should be fairly stable year round.
From that we can determine the temperature at depth using the temperature gradient.