Geochemical investigations on fluvial sediments contaminated by tin-mine tailings,Cornwall, England |
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| Authors: | W W -S Yim |
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| Institution: | (1) Department of Geography and Geology, University of Hong Kong, China |
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| Abstract: | Tin-mine tailings containing high concentrations of Sn, Cu, Zn, Fe, Mn, As, and W are discharged into the Red River of cornwall,
England and are then transported into St. Ives Bay under normal flow conditions. Most of the tin-bearing particles in the
fluvial sediments are smaller than 170 μm, but tin-bearing composite grains or mineral grains with tin interspersed in the
crystal lattices also occur in coarser size fractions. Tin distribution in the sediments is controlledby: (1) the distance
from the source of the tailings, and (2) the concentration processes operating on the river bed. Suspended sediment and sediment
transported by saltation filtered from river water samples also showed high concentrations of metals although, in contrast
to the bottom sediments, they vary within a narrow range. Distributions of Cu, Zn, Fe, As, and Pb in the filtered sediments
probably are related to the physical and chemical behavior of their sulphide minerals during fluvial transportation.
A regional stream-sediment geochemical reconnaissance survey for tin did not show the highest concentration in the Red River;
this indicated that in other rivers and streams tin reconcentration by selective removal of light minerals had taken place
in the bottom sediments after mining operations had ceased. These rivers and streams also can transport large quantitiies
of land-derived sediment including tin-mine tailings discharged into them when mines were operating. The minimum distance
of tin transported by the Red River is at least 10 km; however, most of the tin was derived from mine tailings and is considered
to be unnatural. |
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