Geochemical and mineralogical record of historical mining, Hayle estuary, Cornwall, UK

Rollinson, G.K., Pirrie, D., Power, M.R. and Cundy, A.B. (2007) Geochemical and mineralogical record of historical mining, Hayle estuary, Cornwall, UK. Geoscience in South-West England, 11 (4), 326-337.

Abstract

The release pf particulate waste as a result of major historical mining activity within the polymetallic Cornubian orefield, Cornwall UK, has locally caused significant contamination of estuarine sediments. In this study the impact of historical mining on the southwest Hayle Estuary, Cornwall, UK, was evaluated by examining the sediment geochemistry and mineralogy of nine shallow (<1 m) cores along with surface sediment sampling throughout the intertidal areas of the estuary. The sediment geochemistry of ll of the cores shows very elevated levels of tin and copper (maximum Sn value of 7041 ppm and Cu 29,869 ppm).
Surface (uppermost 5 cm) sediment samples are also contaminated, with up to 4520 ppm Cu, 5455 ppm Sn, 2292 ppm As, 522 ppm Pb and 1777 ppm Zn. Core dating indicates that the sediments currently exposed at the surface were deposited prior to 1880. The detrital heavy mineral assemblage is dominated by cassiterite, chalcopyrite, arsenopyrite, sphalerite and pyrite along with minor galena, monazite, zircon, stannite, wolframite, plumbogummite, covellite, bornite and ilmenite. In addition, man made slag and smelt products are common. Diagenetic pyrite, chalcopyrite and atacamite are also present. The sediment geochemistry and mineralogy are interpreted to represent (a) the input of historic mine waste tailings and smelt waste into the estuary probably prior to 1880, and (b) the subsequent exposure of these contaminated sediments as a result of recent erosion.

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Contributors

Author: A.B. Cundy

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