Geochemistry in prospectivity modelling: investigating gold mineralization in the Taupo Volcanic Zone, New Zealand

Abstract

Prospectivity modelling of epithermal gold mineralization has been completed over the Taupo Volcanic Zone (TVZ), North Island, New Zealand. The TVZ is unique in that it is a present-day analogue of the environment in which many epithermal ore deposits, such as in the adjacent Hauraki Goldfield in the Coromandel Volcanic Zone, are formed. The model utilizes compiled digital data including: historical exploration data; geological data from the Institute of Geological and Nuclear Sciences Quarter Million Mapping Programme over Rotorua, Hawkes Bay and Taranaki; recent Glass Earth Gold Ltd geophysical data; and historic exploration geochemical data from rock-chip and stream sediment samples. The weights of evidence modelling technique was used to determine spatial correlations between known gold prospects and predictive maps, created from the available data, representing each component of the currently accepted mineral system model for epithermal gold. Despite the limited coverage of several data-sets, the resulting prospectivity model over the TVZ confirms potential for gold mineralization. The most prospective areas are those associated with active and inactive hydrothermal systems represented by areas of hydrothermal alteration. The Rotokawa and Waiotapu hydrothermal centres have been identified as particularly prospective, suggesting these systems may represent modern analogues of epithermal gold mineralization.

Porphyry and skarn Cu prospectivity of Sumatra with GIS spatial modelling techniques

“…The use of original or re-analysed legacy data in recent GIS-based MPM is common. For example, Payne and Peters 50 utilised rock chip assays from the 1980s in a fuzzy logic gold prospectivity mapping of part of New Zealand; Mars et al 51 and Xiao et al 52 included, respectively, mid-1970s soil and stream sediment assays and stream sediment samples collected starting in 1979, in their geochemical evidential layers to assess the porphyry Cu prospectivity in the Basin and Range Province, US, and in China, with the WoE method. In this study, 3111 samples from Aceh and 15,744 samples from Central-South Sumatra formed the basis for the geochemical evidential layers.…”

Ambient Noise Tomography and Machine Learning Models to Reveal Geothermal Structure in the Taupo Volcanic Zone

“…In geothermal environments, ground water has always existed, and the main contrast velocity is among fractured, non-fractured rock, altered or nonaltered rock 6 due to the dynamical deformation of tectonic-magmatic-volcanic mechanisms. For mineralized ore environments (i.e., hydrothermal/geothermal mineral deposits), the ore minerals as magmatic uids lled into fractures as ore forming processes [11][12][13] . These ore mineral-lled fractures tend to cause high velocity (or high gravity or magnetics) compared to the surrounding rock 14 .…”