Anyone planning an ascent of EL Cap who is willing to help some geologists trying to make a new map of the face should check out the link below.
It sounds fairly straight forward,they are just collecting as many photos of the various types of granite to create a new map.
More details are at
http://www.supertopo.com/climbers-forum/1810189/El-Capitan-Geologic-Mapping...
John