SEG - Society of Economic Geologists

JULY 2012 • No 90 SEG NEWSLETTER 33
Society of Economic Geologists Foundation
Student-Dedicated Field Course • Iberian Pyrite Belt
May 12–18, 2012
WILLIAM X. CHÁVEZ, JR. (SEG 1990 F) AND ERICH U. PETERSEN (SEG 1986 F)
The Society of Economic Geologists
Foundation held its ninth Student-
Dedicated Field Course, with emphasis
on the regional characteristics of volcanogenic
massive sulfide (VMS) systems
of the Iberian Pyrite Belt (IPB). Sixteen
students, representing eight countries,
as well as four professionals serving as
mentors to the students, participated in
the field course. The importance of
these offerings to the SEG Foundation
mission to provide opportunities for
students to observe ore deposits features
first-hand is reflected in the fact that
more than 50 students applied for this
course, as well a dozen professionals.
Starting in Lisboa, we traveled along
the strike of the IPB across Portugal and
Spain, arriving in the Arecena area for
our first visit: the mid-1990s discovery
comprising the Las Cruces VMS system.
Producing approximately 72 kt/yr of
cathode copper, Las Cruces is one of
the largest copper mines in Europe, and
our discussions centered on the discovery
history of the deposit, as well as the
advantages of copper recovery using
hydrometallurgical methods, one of the
few mines in the IPB to do so.
Aguas Teñidas, a polymetallic VMS
system producing Cu, Zn, and Pb concentrates
from massive and stockworkstyle
ores, was our next visit, and provided
the opportunity for participants
to observe variations in VMS
ore styles and metal contents.
Ore production is from a series
of underground orebodies, each
having distinct metal contents
and metal ratios; by means of
these, we were introduced to
the complexities of ore segregating
and processing, and the
necessity of producing highquality
concentrates for competitive
marketing. Review of
core provided the opportunity
to see sedimentary features
that characterize the ore-host
Devonian-age rock units of the
Aguas Teñidas mine area.
Traveling back to Portugal
along the southern part of the
belt, our following visit was to
the largest metal-producing
mine in western Europe, the
polymetallic Neves Corvo
mine operated by Lundin
(SOMINCOR). Partici pants
were split into two groups,
with one group visiting the
underground mine, while
another toured the extensive
concentrator operations;
this division allowed
students to see the de tailed
mine-to-mill operations
that process complex ores
derived from more than 80
underground faces. We
learned that infill drill hole
spacings of 17.5 m were
necessary to effectively
understand ore grade and
metal distributions, making
Neves Corvo one of the most densely
drilled orebodies in the world.
The Aljustrel mine, representing the
westernmost producing ore district in
the IPB, is a polymetallic Cu-Zn VMS
system that currently produces approximately
70kt/yr of copper concentrates;
formerly emphasizing zinc production
and potential, the Aljustrel mine now is
the second largest producer of copper
in the Portugal section of the belt. Out
visit involved both underground and
concentrator visits, reinforcing the need
to understand both complex mine geology
and ore metallurgical characteristics
Field course participants listen to Joáo Matos of the
Portuguese Geological Survey describe local stratigraphy
near the westernmost known margin of the IPB in Portugal.
Joáo is describing the local VMS environment on properties
being explored by Paul Kuhn and the Avrupa Minerals-
Participants listen to a geology presentation at the Aguas
Teñidas polymetallic VMS mine, southwestern Spain. All IPB
mines provided detailed discussions of regional and mine geology,
emphasizing the stratigraphic occurrences of massive sulfides
and regional structural considerations.
in order to produce a market-competitive
ore concentrate.
Our final day was spent reviewing
exploration characteristics of the IPB,
with a visit to the Avrupa Minerals
exploration programs near the westernmost
known margin of the belt, in the
Lousal-Grándola area. Paul Kuhn and
the Avrupa Minerals exploration team
discussed exploration ideas and concepts
within this section of the belt and
included a visit to an exploration drill
rig testing the stratigraphic sequence
known to host VMS bodies in the Lousal
region. Following the exploration review,
Joáo Matos of the Portugal Geological
Survey conducted a visit to the Lousal
Life Science Center at the former Lousal
pyrite mine. The Portuguese government
and Survey have converted the
former mine area into an educational
center, discussing the importance of
mining, the environment, and regional
sustainability issues. Joáo discussed the
complexities of this portion of the IPB,
and recent advances in understanding
the tectonostratigraphic nature of the
sedimentary sequences in this region,
especially the ore-host horizons.
Our traditional farewell dinner, back
in Lisboa, allowed participants to review
our visits to the IPB and to establish contacts
for future discussions and continued
professional-student interactions. These
end-of-course dinners also provide the
opportunity for the SEGF
to present certificates to
Antofagasta Minerals joint venture exploration team. to page 34 ...
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