Applied Geochemistry. Suppl. Issue No.2. pp. 26J-268. 1993 Printed in Great Britain Q88J-2927193 $6.00 + .00 © 1992 Pergamon Press Ltd Sources, solid-phase transport and geochemical associations of Co and Cu in a small upland catchment, English Lake District JOY E. RAE and ANDREW PARKER Postgraduate Research Institute for Sedimentology, University of Reading, Whiteknights, PO Box 227, Reading, Berkshire RG6 2AB, U.K. Abstract-Deficiencies in Co and Cu are found in animals farmed in the Brotherswater catchment in the English Lake District. The only source of these elements is the local bedrock, which is acid igneous, and therefore contains low concentrations of Co and Cu. Furthermore, the fine-grained weathering products, enriched in Co and Cu, are very mobile and rapidly flushed out of the grazing environment into the lake sediments and beyond. Geochemical associations of Co indicate a strong dependence on Fe and Mg concentrations in both source rock and, unusually, in weathering products. The association with Mn appears to be less significant for all samples. Controls on the behaviour of Cu in the bedrock remain unclear but an association with organics in the weathering environment has been confirmed. INTRODUCTION COBALT AND CUare both essential elements for ani- mal and plant nutrition (ALLOWAY, 1990), so their levels and availability have been widely investigated (e.g. BURNS, 1976; LONERAGAN and ROBSON, 1981; JARVIS, 1984; SHOROCKS and ALLOWAY, 1987). How- ever, there has been no study in an upland catchment of Co and Cu deficiencies in relation to sediment transport and geochemical associations of the ele- ments. This is in spite of active farming of many upland catchments (e.g. in the U.K.), and the poten- tial for rapid transport out of the system of fine- A FIG.1. Location map of English Lake District and Brothers- water. 263 grained sediments, which are well known to be rela- tively enriched in Co and Cu (FORSTNER, 1989). Brotherswater is a small upland catchment in the English Lake District (Fig. 1), with a well-defined watershed. The area is farmed (1200 ha), with a small percentage of cutting land and good pasture, the rest being open hill grazing. Cobalt, Cu and Se deficiency problems occur both in the catchment and in the valley beyond. These are manifested predominantly in the cattle. The aim of this study was to investigate the sources, solid-phase transport and geochemical associations of two of the deficient elements (Co and Cu) in the Brotherswater catchment. GEOLOGICAL SETTING The English Lake District is predominantly made up of Lower Palaeozoic igneous and sedimentary rocks that have been affected by the Caledonian and Hercynian orogenies. In the Brotherswater catchment the bedrock iscomposed of Borrowdale Volcanic Series (Ordovician): chloritized and sheared andesitic tuffs (-96% of the exposed rock surface); andesiticlrhyolitic lava flows (4%) (CHAMBERS, 1978). The surficial deposits of the study area probably relate to two periods of glaciation and retreat: that of maximum extent at 25,000 a BP (Devensian), and the minor resur- gence of glacial activity between 11,000 and 10,000 a BP. It is thought likely that all the surficial deposits found today in the Brotherswatercatchment are oflocal origin (CHAMBERS, 1978). Soil development has proceeded both through and since the Late Devensian. METHODOLOGY Samples of bedrock, stream sediment, and soil and bank material were collected during a survey of the catchment in October 1990 (Fig. 2). In addition, a 4.5 m sediment core was obtained from the deepest part of Brotherswater (water depth 16 m), using a 6 m Mackereth pneumatic corer (CHAMBERS, 1978). The core was sliced into 2.5 cm intervals that were dried at 60°C for 24 h.