Geology question about the abundance of granitic rock?

There are four main types of granites: O type (orogenic, or formed due to an orogeny), A type (anorogenic, or formed in the absence of an orogeny) , S type (formed primarily from sedimentary rocks) and I type (formed primarily from igneous rocks), with four different formation processes. O type granites are formed due to an orogenic event, such as continental plate subduction of an oceanic plate. The Sierra Nevada Batholith is an example of this type. A type granites are formed without the presence of an orogenic event. Pike's Peak is an example of this type of granite. I can't remember the mechanisms that result in I type or S type granites, but another granite producing process is ociated with hot spots, and the Yellowstone Caldera (which is a rhyolite with a granitic magma chamber) a possible producer of these granites.