Interpretation of gravity and magnetic anomalies at Lake Rotomahana: geological and hydrothermal implications
Tontini, F. Caratori
de Ronde, Cornel E. J.
Scott, Bradley J.
Tivey, Maurice A.
MetadataShow full item record
KeywordLake Rotomahana; Hydrothermal systems; Magnetic anomalies; Gravity anomalies; Phreatomagmatic eruptions; Basaltic dikes
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.
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.
Showing items related by title, author, creator and subject.
High-resolution near-bottom vector magnetic anomalies over Raven Hydrothermal Field, Endeavour Segment, Juan de Fuca Ridge Tivey, Maurice A.; Johnson, H. Paul; Salmi, Marie S.; Hutnak, Michael (John Wiley & Sons, 2014-10-06)High-resolution, near-bottom vector magnetic data were collected by remotely operated vehicle Jason over the Raven hydrothermal vent field (47°57.3′N 129°5.75′W) located north of Main Endeavour vent field on the Endeavour ...
Tominaga, Masako; Sager, William W. (John Wiley & Sons, 2010-05-12)The current M-anomaly geomagnetic polarity timescale (GPTS) is mainly based on the Hawaiian magnetic lineations in the Pacific Ocean. M-anomaly GPTS studies to date have relied on a small number of magnetic profiles, a ...
Central Anomaly Magnetization High documentation of crustal accretion along the East Pacific Rise (9°55′–9°25′N) Williams, Clare M.; Tivey, Maurice A.; Schouten, Hans A.; Fornari, Daniel J. (American Geophysical Union, 2008-04-09)Near-bottom magnetic data collected along the crest of the East Pacific Rise between 9°55′ and 9°25′N identify the Central Anomaly Magnetization High (CAMH), a geomagnetic anomaly modulated by crustal accretionary processes ...