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SEG student chapter members from the Univerisity
of Utah, New Mexico Tech,
UT Austin and Berkeley
jointed together for a field trip to Portugal and Spain, May
15-29, 2001. The trip, lead by Drs. Erich U. Petersen and William
X. Chavez, Jr., included a total of 18 students and 4 professionals.
The excursion covered many practical aspects of ore deposits,
mineralogy, geological engineering, structural geology, environmental
geochemistry, hydrology, geophysical exploration, environmental
restoration, economics, and the role that natural resources have
played in the unfolding of civilization on the Iberian Peninsula
and Europe in general. Our first stop after leaving Lisbon was
the Neves Corvo Mine, the highest grade and newest copper
mine in Europe. This massive sulfide deposit, hosted in volcanic
rocks, is famous for its high tin grades and its discovery revolutionized
thinking regarding the possibility of finding high-grade deposits
in well-explored portions of the globe. At Aljustrel we
visited a Zn-rich VMS deposit where production was on hold pending
development of adjacent orebodies. At the present time the main
product of the mill was to produce freshwater from the water
being pumped from underground and the rock materials storage
area! At Lousal we saw Roman mine workings (Au). Both Lousal
and São Domingo have received recent attention
for exploration and for environmental reasons. At São
Domingo drainage from a stockpile of low-grade pyritic material
has resulted in runoff waters with a pH of 2. On the Spanish
side of the Pyrite belt we visited the famous Rio Tinto
deposits where the Romans won gold from gossans that contained
1 ppm of the metal. At Rio Tinto we saw mining implements believed
to be over 9000 years old attesting to the long mining history
of the area. Mining at Rio Tinto was greatly expanded at the
dawn of the industrial revolution in England. Rio Tinto supplied
much of the SEG Newsletter October, 2001. Revised: 10/1/2001 |
iron ore that made the industrial
revolution possible. Mining here also denuded large areas exposing
fine-grained pyritic rocks to rapid chemical weathering. Acidity
of the rivers draining the area increased dramatically. Over
the decades both the flora and fauna in this extreme environment
have adapted to the new conditions and now much of the area is
protected so as to preserve these extreme environments for scientific
study. The Las Cruces deposit, located on the outskirts
of Sevilla, was a geophysical discovery under several hundred
meters of cover. With the environmental studies completed and
most of the mining permits in hand, mining is scheduled to begin
within a year. Las Cruces is one of the largest new projects
in Europe, capable of supplying six percent of Europe's copper
needs. Leaving the Pyrite Belt behind, we traveled to the famous
Almaden mercury district. The Romans discovered the area
and guarded it carefully to prevent others from acquiring the
cinnabar, which they used as ornamental body-paint. Mercury from
this district made the California (the forty-niners) and later
gold rushes possible. Yearly production records date back 500
years! Today Almaden serves as a world recycling center for mercury.
Crossing back into Portugal we visited one of the largest tin-tungsten
mines in the world, Panasqueira. Unusual, horizontal quartz
veins host wolframite, aresenopyrite, cassiterite, and chalcopyrite
mineralization. Exceptionally large crystals of numerous minerals
have been found in this deposit.