Discovery of active hydrothermal venting in Lake Taupo, New Zealand

https://doi.org/10.1016/S0377-0273(01)00332-8Get rights and content

Abstract

The Horomatangi geothermal system of Lake Taupo, New Zealand, is a sub-lacustrine equivalent of subaerial geothermal activity nearby in the Taupo Volcanic Zone (TVZ). The setting of this system is rare within the TVZ as it is directly associated with an individual volcanic feature, that of the 1.8 ka Taupo eruption vent. Two distinct hydrothermal vent areas, named Te Hoata and Te Pupu, have been discovered during dives with the submersible Jago. Venting of gases was seen at both sites and hot water (up to 45°C) discharges at the Te Pupu site. Dilute water samples have concentrations of SO4, Cl, Na and SiO2 above ambient lake water values. Gas samples have compositions similar to other TVZ geothermal systems. Gas geothermometers indicate the existence of a high-temperature hydrothermal environment beneath the lake with reservoir temperatures in excess of 300°C. Chimney structures were found at the Te Pupu site. They are up to 30 cm tall and mineralized by an ‘epithermal’ suite of elements, including S, Hg, As, Sb and Tl. The walls of the chimneys are largely composed of diatoms and strands of silicified filamentous bacteria embedded in an amorphous silica groundmass. Bacterial mats are commonly associated with the gas vents and also occur at two hot springs. Close to the vents, commonly perched on top of dead chimneys and/or exposed outcrops, are dense assemblages of what are probably a new species of sponge of the genus Heterorotula. The sponges host a notably diversified, associated invertebrate fauna and represent a previously unseen biomass on the lake floor. The sponges appear to have bored into the mineralized chimneys.

Introduction

Known occurrences of hydrothermal activity in deep (>30 m) freshwater lakes are few, and even fewer have been studied in detail. Even scarcer are examples of associated biological communities and include Crater Lake, Oregon (Dymond et al., 1989), Yellowstone Lake, Yellowstone National Park, Wyoming (Remsen et al., 1990), Lake Baikal, Siberia (Crane et al., 1991) and Lake Tanganyika, East Africa (Tiercelin et al., 1993). Direct observation of active venting has been seen in Yellowstone Lake by using a remotely operated vehicle, and in Lake Tanganyika by scuba divers. Here we report the results of the joint New Zealand/German Taupo ’98 dive project with the submersible Jago which includes the first observations of vigorous hydrothermal venting in a lake using a manned submersible.

The aims of the project were to: groundtruth geophysical anomalies in an area near the Horomatangi Reefs of Lake Taupo that indicated probable hydrothermal activity; sample and analyze vent fluids and any mineralized samples; provide insight into the spatial, temporal, and chemical evolution of the hydrothermal system; and determine the nature of any biological activity associated with venting.

Section snippets

Regional geologic setting

Lake Taupo is New Zealand’s largest lake covering 623 km2 and is the site of one of the world’s most active rhyolitic calderas as part of the Taupo Volcanic Zone (TVZ; Wilson, 1993; Fig. 1A). Taupo is the oldest currently active rhyolite center in the TVZ, having been active for >330 ka (Wilson et al., 1984). Lake Taupo is thus the focus of some of New Zealand’s largest rhyolitic eruptions, including the 26.5 ka Oruanui eruption that generated 430 km3 of fall deposits and 300 km3 of pyroclastic

Water chemistry

The relatively high concentrations of dissolved salts in several lakes found in the TVZ have been attributed to an input from hydrothermal fluids (McColl, 1972, McColl, 1975, White et al., 1980, Schouten, 1983, Timperley and Vigor-Brown, 1986). For example, mass budget calculations for Lake Taupo waters show a substantial excess (∼2.4 times) of dissolved salts flowing out of the lake relative to those flowing in with surface water, including input from thermal springs on the northeastern and

Discussion

The Horomatangi geothermal system is a rare example of an active geothermal system in the TVZ that is directly associated with an individual volcanic feature, i.e. the main source vent area for the 1.8 ka Taupo eruption. The size of the Taupo eruption meant that caldera collapse will have occurred (Wilson, 1993), infilling the lake with large quantities of volcaniclastic rocks (Davy and Caldwell, 1998). Thus any hydrothermal activity affecting these rocks is post-1.8 ka which makes the

Acknowledgements

This research project was done in partnership with the Tuwharetoa Maori Trust Board and we thank them for their permission to dive on the Horomatangi Reefs site. We acknowledge the skill and enthusiasm of Jago pilot Jürgen Schauer and dive coordinator Karen Hissmann. We are grateful to Chris Jolly, Les Porter, Steve Mawdsley, Gareth Davies and John Baker in providing the necessary logistical support. Comments made on an earlier draft by G.J. Massoth and reviews by R.W. Collier and M.H.

References (55)

  • P.C. Whiteford

    Heat flow measurements in the sediments of Lake Taupo, New Zealand

    Tectonophysics

    (1996)
  • C.J.N. Wilson

    The 26.5 ka Oruanui eruption, New Zealand: an introduction and overview

    J. Volcanol. Geotherm. Res

    (2001)
  • R.R. Brooks et al.

    Mercury and other heavy metals in trout of central North Island, New Zealand

    N. Z. J. Mar. Freshw. Res

    (1976)
  • Caldwell, T.G., Bibby, H.M., 1992. Geothermal implications of resistivity mapping in Lake Taupo. In: Proceedings 14th...
  • Calhaem, I.M., 1973. Heat flow measurements under some lakes in the North Island of New Zealand. Ph.D. thesis, Victoria...
  • B.W. Christenson et al.

    Ohaaki reservoir chemistry: Characteristics of an arc-type hydrothermal system in the Taupo Volcanic Zone, New Zealand

    J. Volcanol. Geotherm. Res

    (2002)
  • Cole, J.W., Darby, D.J., Stern, T.A., 1995. Taupo Volcanic Zone and Central Volcanic Region - back arc structures of...
  • K. Crane et al.

    Hydrothermal vents in Lake Baikal

    Nature

    (1991)
  • D’Amore, F., 1991. Gas geochemistry as a link between geothermal exploration and exploitation. Application of...
  • D.J. Darby et al.

    Geodetic measurement of deformation in the Taupo Volcanic Zone, New Zealand: the north Taupo network revisited

    N. Z. J. Geol. Geophys

    (2000)
  • de Ronde, C.E.J., Davy, B.W., Smith, R.T., Immenga, D.K.H., Baxter, J.A., 2001. Detailed swath mapping survey of a...
  • J. Dymond et al.

    Bacterial mats from Crater Lake, Oregon and their relationship to possible deep-lake hydrothermal venting

    Nature

    (1989)
  • Ellis, A.J., Mahon, W.A., 1977. Chemistry and Geothermal Systems. Academic Press, New York, 392...
  • Forsyth, D.J., Howard-Williams, C., 1983. Lake Taupo. In: New Zealand Dept. Sci. Res., DSIR Info. Ser. 158, 163...
  • Fournier, R.O., 1981. Application of water geochemistry to geothermal exploration and reservoir engineering. In:...
  • J.C. Francis et al.

    Copper and zinc toxicity in Ephydatia fluviatilis (Porifera: Spongillidae)

    Trans. Am. Microsc. Soc

    (1988)
  • N.G. Gee

    Freshwater sponges from Australia and New Zealand

    Rec. Aust. Mus

    (1931)
  • Cited by (67)

    • Understanding caldera degassing from a detailed investigation at Lake Rotoiti, Okataina Volcanic Centre, New Zealand

      2023, Journal of Volcanology and Geothermal Research
      Citation Excerpt :

      We propose that the deep gas is likely CO2 but is consumed or reduced to CH4 during the uprising of the bubble toward the surface. CH4 was reported in the bubbles (Gibbs, 1992) and this phenomenon is also seen in Horomatangi Reefs, Lake Taupo, where surface CO2 range from only −2.21 to 0.56 g m−2 d−1 (De Ronde et al., 2002). Surface samples at Lake Rotoiti were attempted to confirm this hypothesis but analyses were dominated by air contamination due to the slow acquisition.

    View all citing articles on Scopus
    View full text