Characteristics and controls of the largest porphyry copper‐gold and epithermal gold deposits in the circum‐Pacific region

Eleven gold‐rich porphyry copper and 14 epithermal gold deposits around the Pacific rim contain > 200 t (‐7 million oz) of gold. These large porphyry‐type deposits conform to a single overall model, whereas the large epithermal gold deposits are varied in both genetic type and mineralisation style. Most regional and local characteristics of the largest porphyry and epithermal deposits fail to explain convincingly their extremely high gold contents. Nevertheless, a number of hypothetical processes operative alone, or in combination, in the mantle, in upper crustal magma chambers and at the sites of gold accumulation are believed to maximise the likelihood of exceptional gold concentrations. Partial melting of the upper parts of stalled lithospheric slabs in the mantle, immediately following collision or arc migration, promotes oxidation of mantle sulfides and the release of gold. These tectonic scenarios may also result in rapid cooling and uplift‐induced depressurisation of upper crustal magma chambers, t...

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