If you’re trying to get your arms around what a copper porphyry deposit is all about this paper by Don Singer is looked upon as pretty much the definitive summary research paper available.

http://pubs.usgs.gov/of/2008/1155/of2008-1155.pdf

Medinah’s hyper spectral satellite imaging study revealed the presence of “about a dozen intrusives” including a copper-gold porphyry (type 20c in this paper) and a copper-moly porphyry (type 21a) in the Singer classification system. In a nutshell they’re huge, of moderate grades and have extremely long mine lives. It is the extremely long mine life that is of interest to the major mining firms because once they put the initial capital expenditure in they can ring the cash register for a very long time. The significance of owning a 7.5% “free carried interest”/net smelter return for the life of the mine in a twin porphyry complex environment without having to contribute to the significant capital expenditure is what to focus on.

Courtesy of Dr D