U.S. Department of the Interior - U.S. Geological Survey
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NUMBER 4, December 1995
The information on this website is for administrative use only.
It should not be quoted or cited as a publication.
Joint USGS Project with Hungary and Slovakia on Mineral Resources and
Environmental Risks
Contributed by Byron R. Berger, USGS, MS 973, Denver, CO
A three-year duration Hungarian-American Joint Fund (J.F. No. 415)
project with Slovakian participation has been initiated on mining-induced
environmental risks, ore-deposit modeling, and the assessment of mineral
resource potential, and the first workshop was held in
Budapest, Hungary, from April 25-May 5, 1995. The USGS team includes Byron
Berger, Richard Wanty, Lawrence Drew, and Walter Bawiec; Hungarian
counterparts include Laszlo Odor, Eva Veto-Akos, and Gyorgy Csirik; and our
Slovakian host was Jaroslav Lexa. Extended discussions were held at the
Hungarian Survey on each of the project components, but mine-site visits in
north-central Hungary and central Slovakia were of most value in evaluating
the potential for environmental effects from the ancient to modern-day
mining activities.
Our first stop was at Nagyborzsony in the Borzsony Mountains which are
adjacent to the Danube River north of Budapest. The mountains are a
remnant of an andesitic to dacitic stratovolcanic field, part of the Inner
Carpathian Neogene volcanic arc. The mining of polymetallic veins dates
back several centuries, and the sulfide-rich dumps and tailings from these
operations are within a drainage that flows through the village of
Nagyborzsony and into a tributary of the Danube River. A deeper, porphyry
copper style mineralization has been explored, but the system appears to be
relatively low in sulfide content, potassic alteration is minor, and
low-density stockwork veins contain quartz and calcite. The leavings from
the old mine activity and acidic mine waters in the old workings appear to
be the main environmental concerns.
Our second and third stops were in the Matra Mountains in north-central
Hungary, first at Recsk, then at Gyongyosoroszi. Recsk is a large, buried
porphyry copper-polymetallic vein and replacement-copper/gold skarn system
with a several square kilometer advanced-argillic alteration zone above and
lateral to it. The host rocks to the mineralization are andesitic to
dacitic rocks related to Paleogene volcanic activity on a basement of
Triassic limestone and siliciclastic rocks. Within the advanced-argillic
alteration, copper-gold ores occur in siliceous brecciated areas, the most
productive of which are in the Lahoca mine. Ore minerals at Lahoca include
enargite, tetrahedrite, and pyrite in a gangue of quartz, kaolinite, and
alunite. Weathering of the argillically altered rock has formed an upland
valley within which there are several small villages. Local ground waters
are affected by the mineralized rock, and the mine dumps and tailings from
the Lahoca mine produce a very acidic runoff into the local drainage
system.
Gyongyosoroszi is a lead-zinc polymetallic vein district on the southern
flank of the Matra Mountains. The veins, which occur in the Miocene
volcanic-arc rocks, contain sphalerite, galena, and pyrite, in a gangue of
carbonate, quartz, chlorite, sericite, and anhydrite. Acidic mine waters
drain into the main drainage which flows through the village of
Gyongyosoroszi, and release of tailings due to dam failure at the mill site
sent lead-rich material down Toka Creek where intermittent flooding has
distributed contaminated material into the village and out onto a flood
plain, on which wine grapes are grown.
Our stop in Slovakia was at Banska Stiavnica in the Central Slovakian
mid-Miocene andesitic to dacitic volcanic field. Here, polymetallic veins
have been mined more or less continuously since the 13th century. These
veins were primarily mined for their Pb-Zn-Ag content in a gangue of
quartz, carbonate, sericite, and chlorite. Many other styles of
mineralization occur in the volcanic field, but the most intriguing are
extensive zones of advanced-argillic alteration, the acid-leaching being so
intense in places that 'sanded' quartz is all that's left. At the Sobov
mine, silica is mined for smelter flux, and pyrite-rich waste material is
dumped along the hillside. Very low-pH waters pond on the surface of the
dump, and acidic dump waters flow from beneath the dump down the hill into
the local drainage and a reservoir which serves as the water supply for
Banska Bela. Mass wasting of the dump sends sulfidic material across
nearby cultivated fields.
The Hungarian Geological Survey is currently developing a baseline
geochemical map of north-central Hungary using stream-sediment and overbank
deposit samples. In addition, all available geologic, geophysical,
geochemical data for this region are being digitized for GIS analysis. The
Slovakian Survey already has in hand digital data bases, but there is a
need to develop the ability to analyze and present the data in a GIS
format. Future plans are to provide the Hungarians with training in the
environmental geology of ore deposits through a workshop and site visits
to Rocky Mountain mining districts, jointly develop environmental models
of the major ore fields in the study area, and complete a digital,
regional-scale, ore-related environmental risk assessment.
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