New Zealand Journal of Geology and Geophysics abstracts
Paleomagnetic-tectonic study of the New Caledonia Koh Ophiolite and the
mid-Eocene obduction of the Poya Terrane
Jason R. Ali*
Jonathan C. Aitchison
Department of Earth Sciences
University of Hong Kong
Pokfulam Road, Hong Kong
P.R. China
email: jrali@hku.hk
Abstract A paleomagnetic study was carried out on
the allochthonous Late Paleozoic Koh Ophiolite of New Caledonia to determine
its formation site. Four outcrops (20 sites) were sampled from weakly metamorphosed
pillow lavas and dike rocks. Usable directional data were obtained from 18
sites, and 2 magnetization components were identified. A high-stability component
thought to be of primary origin is recognised in 11 sites. It is westerly
orientated, but the large spread of directions makes it impossible to deduce
with any precision the latitude at which the Koh Ophiolite formed, a “subequatorial
to mid-latitude Southern Hemisphere location” being the strongest justifiable
statement. An overprint (partial/total) was identified in 9 sites/4 outcrops.
It is northerly directed, upward dipping (c. -57.0 ± 5.8°; i.e.,
of normal polarity), and equates to a paleolatitude of 37.6 ± 6.2°S.
The overprint may be tectonically significant; it corresponds to the position
New Caledonia was at when it was overthust by the oceanic Poya Terrane in
the middle Eocene.
Keywords paleomagnetism; New Caledonia; plate tectonics;
Pacific; Indo-Australian plate; Koh Ophiolite
G01017; Received 7 June 2001; accepted 17 June 2002; published 27 September
2002
New Zealand Journal of Geology & Geophysics, 2002, Vol. 45: 313-322
0028-8306/02/4503-0313 $7.00/0 © The Royal Society of New Zealand
2002
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