China
Africa
Explore chapters and articles related to this topic
Geological, geochemical and geophysical characteristics of geothermal fields
Published in D. Chandrasekharam, Jochen Bundschuh, Low-Enthalpy Geothermal Resources for Power Generation, 2008
D. Chandrasekharam, Jochen Bundschuh
Low-enthalpy geothermal systems are distributed over a large area in New Zealand and include (1) geothermal waters with discharge temperature of 90 °C and less occurring in the North and South islands; (2) high-enthalpy systems (>150 °C) along the margins of the Taupo volcanic zone (TVZ); (3) low-enthalpy systems with discharge temperatures of 120–160 ° C, available from abandoned hydrocarbon wells, and (4) geothermal hot water systems heated near the surface. These systems are associated with four major tectonic settings characterized by (1) subduction related volcanism in the TVZ; (2) intraplate volcanism associated with rifts; (3) fault zones within the North island fore-arc; and (4) Alpine fault zone in the South island fore-arc (Reyes and Jongens 2005). New Zealand has an installed geothermal capacity of 308 MWe. A generalized tectonic setting and the distribution of geothermal areas in New Zealand is shown in Figure 5.1.
Random Vibration: Probabilistic Forces
Published in Haym Benaroya, Mark Nagurka, Seon Han, Mechanical Vibration, 2017
Haym Benaroya, Mark Nagurka, Seon Han
Intraplate earthquakes occur within plate interiors where they are not perfectly rigid. In some cases, for example in Hawaii, these earthquakes are associated with intraplate volcanism. These are studied, generally, to provide data about where and how the plate tectonic model does not fully describe tectonic processes.
Understanding present-day stress in the onshore Canning Basin of Western Australia
Published in Australian Journal of Earth Sciences, 2021
A. H. E. Bailey, A. J. M. Jarrett, E. Tenthorey, P. A. Henson
There have been numerous studies analysing the origin and state of continental Australia’s crustal stress pattern from a broad range of perspectives. A summary is presented by Rajabi, Tingay, Heidbach, et al. (2017), who use the most up-to-date Australian stress database to generate and model continent-scale stresses throughout Australia. Rajabi, Tingay, Heidbach, et al. (2017) also note that while the large-scale driving mechanisms of plate tectonics are the main sources of intraplate stress in the Australian continental crust, geological features such as faults, fractures, lithological density, strength contrasts and intraplate volcanism result in extensive localised stress perturbations in the studied basins. Additionally, Rajabi, Tingay, Heidbach, et al. (2017) highlight that although stress orientations are determined in more detail than stress magnitudes or regimes, the compiled stress data in the Australian Stress Map indicates that shallower parts of the Australian crust are primarily characterised by a present-day thrust faulting stress regime that changes to a prevailing strike-slip stress regime at greater depths.
Introduction to the special issue on Volcanism in Zealandia and the SW Pacific
Published in New Zealand Journal of Geology and Geophysics, 2021
Te Riu-a-Māui/Zealandia has a remarkable temporal and spatial record of intraplate volcanism. North Island contains intraplate volcanic provinces of Miocene to Holocene age, occurring from Northland to Waikato (Smith and Cronin 2020). The youngest intraplate eruption is the ∼500 year old Rangitoto eruption within the Auckland Volcanic Field (Hopkins et al. 2021a), which post-dates Polynesian arrival to New Zealand. South Island, too, has many intraplate volcanic provinces (Figure 2(D and E)), and this Special Issue features reviews of the Oligocene-Miocene Dunedin Volcanic Province, which at 7800 km2 is the largest on-land intraplate volcanic province in the country (Scott et al. 2020a), the lamprophyric-carbonatitic Alpine Dyke Swarm in West Otago (Cooper 2020), and the Waiareka-Deborah Volcanic Field, which erupted continental shelf when almost all of Zealandia was submerged (Scott et al. 2020b). There remains debate on the origins of the Zealandia intraplate magmas, with asthenosphere, lithosphere and combinations of both having been suggested to be mantle reservoirs; this topic requires further work, but the mantle peridotite datasets summarised by Scott (2020) provide a foundation for examining the role of Zealandia’s mantle. Detailed micro-analytical studies of components within the intraplate magmas provide insight into how xenoliths of mantle (Auer et al. 2020) or crust (Scanlan et al. 2020) have reacted with host magma, as well as the formation of amphibole megacrysts in Westland and the Alpine Dyke Swarm (Serre et al. 2020).
Intraplate volcanism on the Zealandia Eocene-Early Oligocene continental shelf: the Waiareka-Deborah Volcanic Field, North Otago
Published in New Zealand Journal of Geology and Geophysics, 2020
James M. Scott, James D. L. White, Petrus J. le Roux
The intraplate Waiareka-Deborah Volcanic Field surrounding Oamaru in the South Island preserves a superb record of Eocene-Oligocene submarine volcanism on the Zealandia continental shelf. The on-land extent is ∼890 km2, and the offshore extent could, potentially, be nearly four times that area. The volcaniclastic beds, which are extensive and well-exposed along the coastline, show that the volcanic field formed from small volume, short duration eruptions, with volcanoes built from tephra deposited by eruption-fed density currents, and more widespread tephras emplaced from ash initially transported in subaerial eruption plumes (Figure 3). The magma also crystallised as sills, pillow lavas and dikes. The sills are extensive, reaching up to ∼25 km2, were emplaced at shallow levels in the thin sedimentary veneer that covered Otago at the time of formation, and are commonly chemically differentiated. Volcaniclastic glass chemistry and bulk rock composition of sills and pillow lavas show that the volcanic field mainly erupted sub-alkaline magmas, although there were minor coeval alkaline components, the best known of which is the xenocryst- and xenolith-rich Kakanui melanephelinite. Radiogenic isotopic properties of the sills and dikes and one melanephelinite clast indicate that the mantle source for the magmas was distinct from the nearby intraplate alkaline Oligocene Alpine Dike Swarm and the adjacent and spatially overlapping Oligocene-Miocene Dunedin Volcanic Group. Intraplate volcanism in Otago therefore has multiple mantle sources.