Research Commons
      • Browse 
        • Communities & Collections
        • Titles
        • Authors
        • By Issue Date
        • Subjects
        • Types
        • Series
      • Help 
        • About
        • Collection Policy
        • OA Mandate Guidelines
        • Guidelines FAQ
        • Contact Us
      • My Account 
        • Sign In
        • Register
      View Item 
      •   Research Commons
      • University of Waikato Theses
      • Masters Degree Theses
      • View Item
      •   Research Commons
      • University of Waikato Theses
      • Masters Degree Theses
      • View Item
      JavaScript is disabled for your browser. Some features of this site may not work without it.

      A comparison of buried andesites at Ngatamariki and Rotokawa geothermal fields, Taupo

      Vestman Andersen, Linda Christina
      Thumbnail
      Files
      thesis.pdf
      27.66Mb
      Example of petrographic description LA1.pdf
      393.6Kb
      Igneous textures.pdf
      262.8Kb
      RK27 strat log.pdf
      799.7Kb
      Whole-rock chemistry raw data.pdf
      650.4Kb
      XRD graphs.pdf
      9.630Mb
      Lithology and stratigraphy.pdf
      268.3Kb
      Well locations.pdf
      172.2Kb
      Inventory list of samples.pdf
      354.2Kb
      Citation
      Export citation
      Vestman Andersen, L. C. (2011). A comparison of buried andesites at Ngatamariki and Rotokawa geothermal fields, Taupo (Thesis, Master of Science (MSc)). University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/5776
      Permanent Research Commons link: https://hdl.handle.net/10289/5776
      Abstract
      The Rotokawa and Ngatamariki geothermal systems are hosted by hydrothermally altered Quaternary andesitic, dacitic and rhyolitic volcanics resting on Mesozoic Torlesse greywacke basement, and covered by lacustrine sediments and surficial deposits. Andesitic lava and breccia (> 2 km thick) below 1 km depth at Rotokawa is an important production aquifer for geothermal power due to its interconnected fracture permeability. Exploration drilling at Ngatamariki has revealed andesite at several depth intervals, with an approximate age of 1.2 Ma for the shallow andesite lavas, interlayered with ~1 km of ignimbrite. Rotokawa andesite is a massive to flow-banded, fine-medium grained porphyritic lava with primary plagioclase (An51-82), clino- and orthopyroxene in an aphanitic groundmass. Accessory minerals are biotite and Fe-Ti oxides. The Ngatamariki andesite has primary plagioclase (An54-82) and clinopyroxene phenocrysts. Intercalated breccia contains andesite, minor rhyolite and greywacke lithics in a fine grained matrix. Hydrothermal alteration is propylitic, albeit with minor potassic or argillic mineralogy resulting from variable conditions within the thermally-evolving reservoirs. The andesite is commonly veined and/or has a vuggy texture. XRF analysis, particularly plots of immobile element data, e.g. Ti vs. Zr, Y vs. Zr, has been used to fingerprint the hydrothermally altered volcanics, and infer the intensity of fluid-rock interaction. The TiO2/Zr ratio in Rotokawa andesite is 27-63 whereas in the Ngatamariki andesite it is 13-48. Chemical data, combined with inferred stratigraphic relationships suggest that Rotokawa andesites derive from an older, basaltic andesite composite cone volcano, compared to a younger dacite/andesite volcanic centre at Ngatamariki.
      Date
      2011
      Type
      Thesis
      Degree Name
      Master of Science (MSc)
      Supervisors
      Pittari, Adrian
      Briggs, Roger M.
      Publisher
      University of Waikato
      Rights
      All items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.
      Collections
      • Masters Degree Theses [2385]
      Show full item record  

      Usage

      Downloads, last 12 months
      256
       
       

      Usage Statistics

      For this itemFor all of Research Commons

      The University of Waikato - Te Whare Wānanga o WaikatoFeedback and RequestsCopyright and Legal Statement