Long term effect on rocks of high pressure and temperature?

Question

The mean surface temperature of Venus is about 460 C and the pressure is about 92 atmospheres. Assuming this situation (or similar) has prevailed for millions of years what changes (if any) would there have been in the structure and chemistry of the rocks on the surface of Venus? Wikipedia(Venus) http://en.wikipedia.org/wiki/Venus

Answer 1

Minerals that have alternative forms that are created under high pressure and heat would be very abundant. Minerals such as carbon-based graphite wouldn't form. They would turn into their alternative forms of coal and diamond.