Hello ALI - the sites that I read a few months ago had all kinds of theories.
Gold is in solution as chlorides, sulphides, organic molecules with N, C, or O, and, occasionally, carried as fine, free gold. THe solutions can be acidic H20, neutral or alkaline H20, and sometimes , a mostly C02 containing fluid. These can be very hot temperatures or less hot, under huge pressures or less huge and the solubilities are effected by all of these. It may take millions of years to deposit concentrated free gold, or insoluble gold containg molecules that need further refining. This deposition can be caused by leaching of chemicals from host rock, by a source of secondary fluid bringing some physical or chemical effector that causes deposition, or by cooling of the fluid near the surface, decrease in pressure, or, in some cases, evaporation to concentrate and deposit the solutes, and other things.
The present surface at Rice Lake is probably not the same surface that was there during the geothermal process that did the depositing. The gold on the surface, then, may have hitch hiked on glaciers to the Black Hills of the Dakotas as alluvial deposits.
So - the gold could be at it's least concentrated in the "pencil" if there was minimal deposition there. It is not uncommon to find high concentrations on a face of the host rock, where chemical deposition events occur, etc. So - I don't think there is any certainty that the highest concentrations of gold are, necessarily, found in the deeper, original, fluid conduits.
Mosey
