The Waihi Region is host to many low sulphidation epithermal Au-Ag
deposits. The Golden Cross mine located at the head of the Waitekauri River,
eight kilometres NW of Waihi, was a gold mining operation that placed
significant emphasis on environmental management. An assessment of the influence
of this mining project on stream sediment geochemistry (Fe, Mn, As, Cu, Pb, Zn,
Cr, Cd, Ni, Ag and Se) in the Waitekauri Catchment has been made. Effective
waste management during the mine operation appears to have prevented
contamination of stream sediment. Trace metal concentrations in the Waitekauri
Catchment sediment have generally decreased since 1987, and are currently mainly
below the ANZECC (2000) sediment quality guidelines. However, elevated As levels
were recorded in the Upper Waitekauri River and Battery Stream, exceeding
guideline values. Elevated levels of Cu, Pb, Zn and Cd were found in the Huanui
Stream, a tributary of the lower Waitekauri River. This reflects the influence
of past mining operations in the valley, as well as natural weathering of
hydrothermally altered Coromandel Group andesite. At a number of sites, Mn
concentrations also exceeded sediment quality guidelines, and this may be
derived from the remediated Golden Cross mine site.