Heat Output from Spreading and Rifting Models of the TVZ, New Zealand
by
Graham Weir
Industrial Research Ltd

Tectonic extension creates volume which can accomodate magmatic intrusions. Spreading models assume this volume is distributed throughout the whole region, perhaps in vertical dykes, whereas rifting models assume the upper crust is thinned and the volume created lies under this upper crust. Bounds on the heat flow from such magmatic intrusions are calculated. A conceptual model of the Taupo Volcanic Zone (TVZ) is developed, to a depth of 25 km, formed from three constant density layers. The upper layer is formed from eruption products. A constant rate of eruption of is assumed, which eventually implies a constant rate of extension, and a constant rate of volumetric creation in the middle and bottom layers. Heat flow calculations are performed, by assuming conductive heat transport below 8 km and above the lower layer, and intrusive heat sources below the upper layer and above 8 km. Some examples are provided which match the present total heat output from the TVZ of about 4200 MW, but these either have extension rates greater than the low values of about 8 +/- 4 mm/a being reported from GPS measurements, or else consider extension rates in the TVZ to have varied over time.

Date received: June 7, 1999

Copyright © 1999 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # cadl-02.