New Zealand Journal of Geology and Geophysics abstracts

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New insights to temperature and pressure beneath the central Southern Alps, New Zealand

R. G. ALLIS

Institute of Geological and Nuclear Sciences
P.O. Box 30 368
Lower Hutt, New Zealand

Y. SHI

Graduate School
USTC
Academia Sinica
Beijing, China

Abstract  Thermal modelling of the late Cenozoic compression in the area of maximum uplift of the Southern Alps, South Island, New Zealand, confirms that the recent uplift and erosion history is consistent with a surface temperature gradient of c. 60deg.C/km, and with paleotemperatures derived from zircon fission track ages of c. 250deg.C at 10 km depth. The present-day thermal regime at mid and lower crustal depths is cooler than that inferred from paleotemperatures preserved in the exhumed rock at the surface because of the effects of crustal thickening. The hot springs scattered through the northern half of the Southern Alps are meteoric water which has equilibrated with rock at temperatures of 90-150deg.C, suggesting circulation to a depth of <3 km. The hot springs constitute a minor component of the upper crustal heat flow, which appears to be predominantly conductive. Fluid pressure may approach lithostatic pressure below 3 km depth, implying a relatively weak crust. The fluid inclusion evidence for trapping of fluids at temperatures of 200-350deg.C may be mostly from infrequent, possibly coseismic, fluid flow events at depths of 5-15 km.

Keywords  Southern Alps; thermal modelling; age dating; fluid inclusions; temperature; pressure; heat flow

New Zealand Journal of Geology and Geophysics, 1995, Vol. 38: 585-592

0028-8306/95/3804-0585 $2.50/0 (c) The Royal Society of New Zealand 1995

PDF file of entire paper: medium quality (783K); (scanned from paper original: notes about this process)

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