New Zealand Journal of Geology and Geophysics abstracts
Oxygen, carbon, and strontium isotopic constraints on timing and sources
of crustal fluids in an active orogen: South Island, New Zealand
T. W. Horton1
J. D. Blum2
D. Craw3
P. O. Koons4
C. P. Chamberlain1*
1Geological and Environmental Sciences Department
Stanford University
Stanford, CA, 94305, USA
email: chamb@pangea.stanford.edu
2Department of Geological Sciences
University of Michigan
425 East University Avenue
Ann Arbor, MI 48109, USA
email: jdblum@umich.edu
3Geology Department
University of Otago
P.O. Box 56, Dunedin, New Zealand
email: dave.craw@stonebow.otago.ac.nz
4Department of Geological Science
Bryand Global Sciences Center
University of Maine, Orono, ME 04469-5790, USA
email: Peter.Koons@maine.edu
*Corresponding author.
Abstract Active deformation on New Zealand’s South
Island can be divided into four tectonic zones: Inboard, Main Divide, Outboard,
and Marlborough strike-slip. On the basis of stable isotope data (δ13C
and δ18O) we suggest that calcite veins are formed from a mixed
meteoric and metamorphic water in the Inboard and Main Divide tectonic zones,
as well as the Alpine-Wairau Fault of the Marlborough strike-slip zone. We
suggest that the metamorphic waters are derived from the breakdown of biotite
at c. 25 km, a depth which corresponds to a conductive zone identified by
a recent magnetotelluric study across central South Island. These metamorphic
fluids exit the orogen along the steep faults that border the Southern Alps.
87Sr/86Sr ratios of vein and fault-zone calcite suggest
that calcite formation is associated with young tectonically driven hydrothermal
fluid flow in the Inboard, Main Divide, and Wairau Fault zones. The age of
calcite formation in the Outboard, Awatere, and Hope Fault zones could not
be explicitly determined.
Keywords calcite; stable isotopes; strontium isotopes;
fluid flow; New Zealand
G02026; Received 17 May 2002; accepted 19 March 2003; online publication
date 10 September 2003
New Zealand Journal of Geology & Geophysics, 2003, Vol. 46: 457-471
0028-8306/03/4603-0457 $7.00/0 © The Royal Society of New Zealand
2003
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