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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
The lithology of the Momotombo geothermal field is divided into six units (Martínez Tiffer et al. 1988, Porras et al. 2005) (Fig. 5.16). The youngest andesites and basaltic andesites interlayered with scoria are underlain by a Pleistocene palagonite tuff alternating with basaltic andesites followed by Late Miocene volcanic products intercalated with sandstones and agglomerates. The middle Miocene fossiliferous marl sediments are separated from the Late Miocene sandstone by ignimbrite flows. The oldest rocks are presented by andesitic lava flows and clastic tuffs. The 150 °Cisotherm, located at a shallow depth, occupies a wide area (Fig. 5.16) and makes this field most suitable for exploiting low-enthalpy fluids.
Revised stratigraphy and first geochronology of the Miocene submarine volcanic succession at Kennaook/Cape Grim, northwestern Tasmania
Published in Australian Journal of Earth Sciences, 2023
J. M. Fox, J. McPhie, R. J. Carey, F. Jourdan
The contact of an oval-shaped basaltic body with the overlying Woolnorth Tuff is exposed north of Flat Topped Bluff (Figure 9c). The margin of the basalt comprises black glass and palagonite. Fluidal apophyses of basalt protrude upward into the tuff, and detached masses of basalt occur in the tuff within 1 m of the contact (Figure 9h, i). The apophyses are up to 75 cm long and 40 cm wide. Bedding in the tuff adjacent to the apophyses is either absent or deformed. The 10–50 cm of tuff immediately above the contact is indurated and strongly jointed, and bedding is absent. Clastic dykes and minor faults with offsets of 1 cm to 2 m are common in the Woolnorth Tuff adjacent to the oval-shaped basaltic bodies. The local faults do not extend into the overlying Studland Bay Basalts.