Geochemistry and mineralogy of soils over the Ohui epithermal Au-Ag prospect, Coromandel Peninsula, New Zealand.

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dc.contributor.advisor Mauk, J en
dc.contributor.advisor Hoskin, P en Carruthers, Scott en 2011-02-24T03:23:38Z en 2011 en
dc.identifier.uri en
dc.description Full text is available to authenticated members of The University of Auckland only. en
dc.description.abstract The Ohui adularia-sericite epithermal Au-Ag prospect is a highly prospective tenement located 14 km north of Whangamata on the east coast of the Coromandel Peninsula in New Zealand, and includes 4 targets, the Great Mexican, Box, Phoenix, and Staircase. The prospect contains a Late Miocene sequence of andesitic and rhyolitic lavas, and pyroclastic deposits, which are hydrothermally altered. Soil horizons at Ohui are developed mostly on bedrock of rhyolite or andesite with some areas that are partially overlain by post-mineral cover, which includes Quaternary volcanic ash up to 3 m thick, landslide debris up to 2 m thick, and Quaternary alluvium up to 15 m thick. Soil samples were collected from a 1 km2 area and comprise 473 soil profile and soil grid samples. Each sample was analysed for 21 elements by solution ICP-MS/-AES following an aqua regia digestion, and for mineralogy by Short Wavelength Infrared techniques. One hundred and five soil Hg gas samples were gathered from 5 selected soil grid lines. These new soil geochemical data have highlighted previous targets and structures at Ohui. Analyses of soils identified strong concentrations of As, Au, Hg, Mn, Mo, Pb, Sb, Se and soil Hg gas related to faults and most of the known mineralisation at Ohui. C horizon soil samples are consistently more enriched and are reliably cospatial with exploration targets relative to A horizon samples, which is different to previous studies utilising soil geochemistry in the Hauraki Goldfield. The SWIR measurements show the presence of kaolinite, smectite, illite and illite/smectite; these clay minerals did not match the underlying alteration mineralogy previously documented in rock samples, and was therefore interpreted to be the result of weathering. The soil Hg gas defines strong enrichments over the Great Mexican fault and eastern vein of the Staircase target, and the data show a small enrichment over the Phoenix target. The correlation between soil Hg gas and mineralisation has been previously documented at Favona, but more work is required to quantify its distribution and association with faults and mineralisation before it can be consistently applied to exploration strategies. As exploration for new economic deposits intensifies, increased attention will be focussed on geochemical exploration techniques. This study outlines the significance of soil geochemistry as an exploration tool for epithermal deposits, particularly in the geologically complex Hauraki Goldfield. Results herein suggest that SWIR analyses of soils is not a useful exploration tool in the Hauraki Goldfield; this may be a more useful application in environments where weathering is less of a contributing factor. en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof Masters Thesis - University of Auckland en
dc.relation.isreferencedby UoA99220454714002091 en
dc.rights Restricted Item. Available to authenticated members of The University of Auckland. en
dc.rights.uri en
dc.title Geochemistry and mineralogy of soils over the Ohui epithermal Au-Ag prospect, Coromandel Peninsula, New Zealand. en
dc.type Thesis en Geology en The University of Auckland en Masters en
dc.rights.holder Copyright: the author en
pubs.elements-id 206488 en
pubs.record-created-at-source-date 2011-02-24 en

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