"Groundwater distribution depends on the porosity and permeability of rocks or sediment. I suggest you "google" porosity and permeability, especially in conglomerates and sandstones. Hopefully that will provide you some insight into this issue."
I have no need to google it, I am quite familiar with sandstones and conglomerates and porosity. You are clearly not, and need to do some more homework before presenting things as "facts".
In general, sandstones and conglomerates have more porosity than many other rock types because they are composed of relatively large sand grains, pebbles, boulders, etc. As these do not pack as efficiently as smaller grains (e.g. clay, silt) they tend to have more space in between rock constituents, giving potential space for holding liquids.
BUT, in many cases, as the rock compacts and/or dissolved minerals crystallize out of fuid in the rock (like from epithermal fluids!!!) pores and/or finer grained minerals wash into pore spaces, the sandstone and conglomerate can lose their porosity over time.
So, where do you find a reference specific to the ARU property that the sandstones and conglomerates, are porous at FDN? That is what you have stated as fact. You are avoiding my question.
Also, you are presenting the rock package above the mineralised zone (Suarez Formation) as just "conglomerate and sandstone". From Sillitoe's recent report:
The conglomerate, sandstone, siltstone, dacitic tuff and andesitic flows that make up the Suarez Formation..
The overlying volcano-sedimentary package is dominated by relatively immature, polylithologic conglomerate, which is capped by finer-grained epiclastic rocks and an andesite flow unit (Fig. 1)
Siltstones, and tuffs in general, are fine-grained (very small grains). In general, finer-grained rocks tend to have minimal porosity, and in fact might act as a seal, helping to keep out overlying ground water from the mineralized zone, yet you only present one side of the story.
I don't know which is the case, but you seem to. I would like to know how you know. |
