dc.contributor.advisor |
Rowland, Julie |
|
dc.contributor.advisor |
Rowe, Michael |
|
dc.contributor.author |
Hudson, Samuel Alexander |
|
dc.date.accessioned |
2022-11-14T01:51:34Z |
|
dc.date.available |
2022-11-14T01:51:34Z |
|
dc.date.issued |
2022 |
en |
dc.identifier.uri |
https://hdl.handle.net/2292/61827 |
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dc.description.abstract |
The Wharekirauponga (WKP) epithermal deposit comprises the largest rhyolite-hosted gold-silver (Au-Ag) vein system in New Zealand’s Hauraki Goldfield. The deposit consists of three primary vein systems, the East Graben (EG), Teawaotemutu-Stream (T-Stream) and Western vein systems, hosted within a sequence of rhyolite cryptodomes and pyroclastic tuff. The EG vein system (EGVS) displays a transition between differing quartz vein textures, where the hanging wall is dominated by banded and lattice textures, which are overprinted by pyrite + marcasite + arsenopyrite vein breccias with enrichments in base-metals in the footwall.
A geochemical and mineralogical study of vein textures in the EGVS was conducted, to refine mineralisation within this system, providing insight into the conditions under which the different veins formed. The interpretations of a deposit-scale study are combined with the results of a core- to micro-scale investigation of wallrock associated with key vein textures to provide insight into their formation. These findings were supplemented by the results of a pilot Fluid Inclusion Analysis (FIA) study to understand the depths of mineralisation of veins in the EGVS below the paleo water table.
Results show a significant halo around the EGVS is dominated by a mineral assemblage consisting of adularia + quartz + pyrite + illite ± albite ± sericite, indicating mineralisation conditions ≥230°C. This adularia-rich core around the EGVS is interpreted as having influenced a switch in the style of mineralisation at the deposit from permeable diffuse flow to structurally hosted flow. Wallrock adularia and quartz deposition during boiling of hydrothermal fluids strengthened the host rock while decreasing its permeability and porosity, hindering the ability for permeable flow. Boiling of fluids and structurally controlled flow in this regime deposited lattice and banded vein textures. Following this, a shallowing of mineralisation below the paleo water table or a weaning of the system promoted mixing and gentle boiling of upwelling alkali-chloride and downward migrating acid-sulfate fluids in the footwall. The EG main vein is interpreted as having acted as a permeability barrier to this late-stage hydrologic regime, reducing its overprinting effect in the hanging wall. |
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dc.publisher |
ResearchSpace@Auckland |
en |
dc.relation.ispartof |
Masters Thesis - University of Auckland |
en |
dc.relation.isreferencedby |
UoA |
en |
dc.rights |
Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. |
|
dc.rights.uri |
https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm |
en |
dc.rights.uri |
http://creativecommons.org/licenses/by-nc-sa/3.0/nz/ |
|
dc.title |
Geochemical and vein textural investigation of the Wharekirauponga epithermal Au-Ag deposit, Hauraki Goldfield, New Zealand |
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dc.type |
Thesis |
en |
thesis.degree.discipline |
Earth Sciences |
|
thesis.degree.grantor |
The University of Auckland |
en |
thesis.degree.level |
Masters |
en |
dc.date.updated |
2022-10-04T10:59:55Z |
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dc.rights.holder |
Copyright: the author |
en |
dc.rights.accessrights |
http://purl.org/eprint/accessRights/OpenAccess |
en |