Christie, A.B.; Carver, R. 2023 Stream-sediment geochemistry of the Hauraki Goldfield, Coromandel Volcanic Zone, New Zealand. Lower Hutt, NZ: GNS Science. GNS Science report 2023/09. 46 p.; doi: 10.21420/A2KA-HV46
Abstract:
Results of mining company stream-sediment geochemical surveys in the Hauraki Goldfield have been compiled in the REGCHEM (Regional Exploration Geochemistry) database, managed by GNS Science. The Hauraki Goldfield dataset contains analyses for 11,127fine-fraction stream sediments, 568 pan concentrates and 1437 BLEG (bulk leach extractible gold) samples from 70 surveys carried out between 1968 and 1991, the main period of modern reconnaissance exploration in the goldfield. The stream-sediment samples were typically analysed for Au and As, and in many cases for other elements, including Ag, Cu, Pb, Zn, Sb and Mo. The BLEG samples were analysed for Au and in some cases also for Ag. The main exploration target was epithermal Au-Ag deposits associated with Miocene to Pliocene volcanism of the Coromandel Volcanic Zone. A secondary target was sub-volcanic porphyry Cu-Au deposits. A large number of geochemical anomalies were identified in this study, and, in particular, there are prominent areas of elevated Cu, Pb and Zn on the western side of the goldfield where there are deeper levels of erosion. This erosion exposes the deep base-metal style of epithermal mineralisation and several porphyry Cu occurrences. Background populations of some elements exhibit different threshold concentrations for the main geological units of greywacke, andesite (and dacite) and rhyolite (auths)
