According to a new study by the University of Toronto geology professor James Mungall, large gold and copper deposits form beneath volcanoes when the Earth's crust is pushed down and begins to melt.
"There's one characteristic that is common to all of these big gold and copper deposits anywhere in the world," says Mungall. He suggests that rich mineral deposits occur when a slab of ocean floor slides underneath a continent or another part of the ocean floor and melts from the heat of the Earth's interior. The slab may get stuck long enough to melt or it may scrape along almost horizontally under the volcano, melting and causing the release of metals to produce gold or copper deposits that are close enough to the surface for mining. Not every volcano produces this melting effect, which explains why valuable deposits are not found near all of them. "These findings could help identify regions where these rich deposits are most likely to be present," he adds.
The results of the study have been published by the Geological Society of America in the October 2002 issue of Geology. An abstract of the article can be found by searching the GSA web site at www.gsajournals.org Prof. Mungall can be contacted at 416-978-2975 or mungall@geology.utoronto.ca
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