Earth Sciences 4432A/B Lecture Notes - Lecture 8: Fluid Inclusions, Chalcopyrite, Kaolinite
13 Apr 2016
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Porphyry cu deposits originally gained their name because they were associated with porphyritic. Compared to other types of copper deposits the grades are low, ~0. 4 to 1. 0 % cu (table 8-1), but the tonnage is large, and in some cases extremely large (>12 billion tonne at el. Au and mo are commonly recovered as by-products of cu mining (often the by- product metals can be the overriding factor that determines whether or not a specific deposit is economic). Porphyry" deposits are now loosely considered to be low-grade large-tonnage deposits, hosted by intrusions that contain mineralization as disseminations, stockworks or veins. The intrusions may or may not have a porphyritic texture depending in part on the depth of emplacement, which ranges from volcanic to sub-volcanic to plutonic. Most porphyry deposits have only been exploited since ~1950, when advances in mining technology allowed large scale open pit mining to be profitable.
