Sorry Lief..didn't know you were learning. All Calderas have mineralization to some extent in the outer edge..some have huge mineralization - like Pebble and BCSP. The same goes to the Bisbee Porphyry in AZ. Tombstone is a Caldera AS CONFIRMED by USGS.
When mother nature spits out that molten lava when a volcano collapses into a caldera, most minerals get disseminated as a ring formation. This is a well proven theory. Please refer to USGS web site and search for Caldera.
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