I found it interesting, after reading 2 or 3 different articles that were in agreement, that this type of event happened on/near the tesorro. The theory is that ,off shore the crust underneath the ocean kept getting pushed underneath the Andes Mountains. As this kept happening over time, the leading edge of that crust, as it went under the mountains, would get burned off. It is suspected that this crust is fairly rich in minerals and that the hot fluids in the earth would melt this mineralization as it became available and deposit some of it each time the fluids got close to the surface and cooled.

It would appear that this process has been continuous for millions of years, and everytime a hydrothermal event happened that deposited the mineralisation, the crust would move in a little further and the process would repeat. This process might have only happened 3 times in the last million years or so, but it was subsequent events known to the Tesorro.

Initially, the Tesorro had its own deposit of epithermal veins that were a result of volcanism, IMO. Thats why we see the evidence of that there clearly on/near the surface.The andesite dykes on the property are a result of this volcanics as they are structures that were created by the same force that creates volcanics.

The pegmatic material on the property identifies the presence of faults. The fluids that brought this material came from the depths and had more room to spread out. So, we have two sort of different events that had their origins from the depths. Each event involves the hot fluids that contain the minerals in solution, as the fluids are pushed up into these less resistive structures (the small volcanos first, then later, the much bigger faults as pressure became more intense and had to split the earth) the fluids hit lower temperatures and cause its minerals to come out of solution and deposit close to the surface (that being anywhere from surface to lets say usually 2k deep, after 2km things may change and become unfavourable for deposition in some areas).

So, it should be reasonable to beleive that one gold depositing event was hot volcanics that put gold on and near the surface. The other event was a cooler/less pressurized mesothermal event that put gradual pressure over a wide area distributing minerals in cracks and fractures as the pressure spread the ground. This would explain the different association of minerals found with the gold. For example, high sulfides found in the C-1 vein, but hardly any in the A-4 vein. So, I believe these two veins were formed from entirely different events.

Now, the other interesting thing is that as that crust kept getting melted down deep,it kept replenishing the hot fluids with minerals. And everytime there was a pressure event that pushed this fluid up into the Tesorro, it released more riches. So, its possible that gold may have been deposited several times here, each time making the deposit much richer. You would think that each event may have deposited the gold a little deeper as space got filled and pressure activity eased, this would fit well with a mesothermal system.