Geochemical surveys for gold in the Berwyn Hills

During a reconnaissance drainage survey of the Berwyn Dome gold (Au) was identified in a panned concentrate from the Afon Trystion near Cynwyd (Figure 1). Additional panned concentrates collected upstream and analysed for Au and the gold-pathfinder element, arsenic (As), revealed the presence of an anomalous but irregular dispersion train over much of the Afon Trystion and its headwater tributary, the Nant y Lladron (Cooper et al., 1984). The area was subsequently resampled by the Geochemical Survey Programme (GSP) in 1989 as part of the systematic regional geochemical mapping of the Mid Wales and Marches 1:250,000 map sheet. During the course of this work, gold was seen in panned concentrates collected from the lower reaches of the Afon Llynor the catchment to the south of the Af on Trystion, and from a small stream 2 km north east of the village of Glyndyfrdwy (Figure 1). This open file report gives the results of detailed follow-up geochemical surveys designed to provide further information on the source of the gold discovered in the Afon Trystion and adjacent catchments by the MRP and GSP regional scale surveys. The surveyed area is situated in Central Wales at the north west margin of the Berwyn Hills, approximately 15 km west of the market town of Llangollen and 3 km south of Corwen (Figure 1). Most of the area is hill land rising to a little over 6OO m, supporting sheep grazing, grouse moor and, in the lower reaches of the main streams, coniferous forest plantations. Acid soils are developed over glacial (largely till) deposits with upto 2 m of peat on the highest ground. Rock exposure is restricted largely to stream courses and outcrops on interfluvial ridges.