Publication Date:
2022-05-26
Description:
Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here for personal use, not for redistribution. The definitive version was published in Journal of Volcanology and Geothermal Research 314 (2016): 84-94, doi:10.1016/j.jvolgeores.2015.07.002.
Description:
We investigate the geological and hydrothermal setting at Lake Rotomahana, using recently collected
potential-field data, integrated with pre-existing regional gravity and aeromagnetic compilations. The
lake is located on the southwest margin of the Okataina Volcanic Center (Haroharo caldera) and had
well-known, pre-1886 Tarawera eruption hydrothermal manifestations (the famous Pink and White
Terraces). Its present physiography was set by the caldera collapse during the 1886 eruption, together
with the appearance of surface activities at the Waimangu Valley. Gravity models suggest subsidence
associated with the Haroharo caldera is wider than the previously mapped extent of the caldera
margins. Magnetic anomalies closely correlate with heat-flux data and surface hydrothermal
manifestations and indicate that the west and northwestern shore of Lake Rotomahana are
characterized by a large, well-developed hydrothermal field. The field extends beyond the lake area
with deep connections to the Waimangu area to the south. On the south, the contact between
hydrothermally demagnetized and magnetized rocks strikes along a structural lineament with high
heat-flux and bubble plumes which suggest hydrothermal activity occurring west of Patiti Island. The
absence of a well-defined demagnetization anomaly at this location suggests a very young age for the
underlying geothermal system which was likely generated by the 1886 Tarawera eruption. Locally
confined intense magnetic anomalies on the north shore of Lake Rotomahana are interpreted as
basalts dikes with high magnetization. Some appear to have been emplaced before the 1886 Tarawera
eruption. A dike located in proximity of the southwest lake shore may be related to the structural
lineament controlling the development of the Patiti geothermal system, and could have been
originated from the 1886 Tarawera eruption.
Description:
Science funding provided by GNS Science Strategic Development
Fund.
Keywords:
Lake Rotomahana
;
Hydrothermal systems
;
Magnetic anomalies
;
Gravity anomalies
;
Phreatomagmatic eruptions
;
Basaltic dikes
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
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