In Brief: Volcanic Vermell


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Colombian police used to play soccer inside the 4200-m high Galeras volcano until it reactivated in 1989. More recently, Galeras erupted on January 14, 1993, killing six scientists and three civilians. On site at the time, Fraser Goff, a geochemist at Los Alamos National Laboratory in New Mexico, was fortunate to have been collecting samples for his work on tritium content of magmatic fluids at a safe distance from the eruption. But Goff s luck didn't end there. A week later a guide asked Goff if he wanted to see some gold. Although Goff didn't take the guide seriously at first, he soon learned that the Colombian Galeras volcano was in fact spewing about 0.5 kg of gold a day. However, the amount of gold emitted can greatly fluctuate, depending on the volcano's daily output of ash and gas, which averages about 500 tons of sulfur dioxide a day. Gold concentrations in various rock samples near the conduit contained as much as 2.5 ppm, whereas samples from a vein cutting older Galeras rocks contained 22–269 ppm, says Goff, who reported his findings at a recent Geological Society of America meeting in Seattle. Although economic geologists have known about the association between precious metals and exhumed volcanoes for some time, the report marks the first time scientists have documented gold being deposited in the conduit rocks of an active volcano.