dome structures in namibia, page-5

Hi Tibbs.

Interesting pics.

A localized dome often indicates the presence of an intrusion at depth. After all, something major had to push the sediments up into the dome shape. Fluids the rock pores will be heated by this intrusion, become buoyant and migrate upwards. They will carry dissolved minerals with them and these minerals will have become more soluble in the heated fluids. The minerals may have come from the magma itself, from the sedimentary rocks under the dome or even from seawater if the dome is forming below sediments on the sea floor and setting up convection currents.

The sides of the dome will tend to split and open up, a bit like stretch marks really. The migrating fluid will tend to move towards these low pressure "dilational" structures and as the fluid cools or low pressure causes boiling off of volatiles, the dissolved minerals will precipitate out.

There you go, a taste of Economic Geology 301.