Hi Sage, Yes we have been there.
Assuming that the abundance of elements of both Earth and Venus are comparable, within the same order of magnitude, Earth and Venus should have comparable amounts of carbon in the lithosphere.
The back side of my envellope says that Venus has about the same amount of carbon in the atmosphere as the Earth has in the crust, forming variations of limestone type rox.
The greenhouse hypothesis for Venus (Kasting, Pollack, Ackerman. Icarus. 1984;57:335-55.) assumes that Venus had an Earthlike appareance in the early days including oceans and weathering processes that bonded CO2 to limestone. How get all the limestone of Earth in the atmosphere?
seems highly inadequate if we need all the CO2 to get out the crust and we need 900-1200 degrees celcius to begin with:
So I was looking for a chemical specialist who could confirm if the processes are possible under lower temperatures.