Abandoned Mines: Effects on stream water geochemistry Fall, 2003 Serena NW Hollmeyer

Abandoned Mines:
Effects on stream water geochemistry
Fall, 2003
Serena NW Hollmeyer
Questions...
• What effects to abandoned mines have on
pH and conductivity?
• What effects will abandoned mines have on
dissolved metal species downstream?
• Where are the metals seen downstream
coming from?
• What impact does pH have on metal
dissolution?
Sample site locations:
• Belvidere Asbestos
Mine, Eden Mills, VT.
• Ely Copper Mine,
Vershire, VT.
• MacIntyre Titanium
Mine, Tahawus, NY.
Belvidere Asbestos Mine
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•
•
•
•
Eden Mills, VT.
Asbestos mine
1960-1993
Serpentine, amphibolite, muscovite schist.
Drains into Dark Branch and Gihon River
Ely Copper Mine
• Vershire, VT.
• 1821-1950
• Weakly calcareous mica schist with
amphibolite and acicular amphibolite.
• Pyrite occurrences.
• Drains into Schoolhouse Brook (Upstream
and downstream samples)
MacIntyre Titanium Mine
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•
•
•
Tahawus, N.Y.
1941-1982
Ilmenite and magnetite
Drains into Opalescent River.
Methods
• Samples collected, filtered and acidified.
• pH and conductivity measured using digital
meters.
• Samples analyzed using inductively coupled
plasma optical emission spectrometer
(ICPOES).
• Looked for 24 different metals.
Belvidere Data
Location
Sample
PH
Conductivity
BEL
Upstream
7.7
39.2
BEL
Pit Lake
9
Off-scale
BEL
Downstream 7.7
81.6
Belvidere Metals
Ely data
Location
Sample
PH
Conductivity
ELY
Upstream
6.7
119.2
ELY
Pit Lake
4.4
Off-scale
ELY
Downstream 6.2
118.8
Ely metals
MacIntyre data
Location
Sample
PH
Conductivity
ADK
Upstream
9.0
20.8
ADK
Pit Lake
8.0
Off-scale
ADK
Downstream 9.0
64.1
MacIntyre Metals
Analysis:
• pH was lowest at Ely (expected due to
sulfidic mineral exposures increasing
acidity)
• Metals were most mobile at Ely, due to low
pH?
• Na, Ca, and Mg levels elevated at each site,
related to bedrock weathering?
Belvidere samples and possible
sources of metals:
Calcic filling of
fractures?
Amphibole
Serpentine
Road salt runoff?
Ely samples and possible sources
of metals.
Calcareous bedrock
Mica
Copper ore
Amphibole
Road salt?
Associated iron ore Feldspar
MacIntyre samples and possible
sources.
Feldspar weathering (no road salt input)
Ilmenite
Conclusions
• pH was lower at
sulfidic site.
• Conductivity was
highest in pit lakes or
drainages
• Lower pH created
conditions condusive
to metals leaching
• Bedrock geology
ultimately determined
metals available for
leaching.
• Bedrock geology also
determined pH, the
controlling factor in
leaching of metals.
Questions?