New Zealand Journal of Geology and Geophysics abstracts
Textural zones in the Haast Schist--a reappraisal
I. M. TURNBULL
N. MORTIMER
Institute of Geological & Nuclear Sciences
Private Bag 1930
Dunedin, New Zealand
D. CRAW
Department of Geology
University of Otago
P.O. Box 56
Dunedin, New Zealand
Abstract Field subdivision of schist using textural
appearance is valuable as a means to readily identify post-metamorphic faults
and to subdivide monotonous schist, at 1:50 000 scale or smaller. Recent
regional mapping in the Haast Schist of South Island, New Zealand, has revealed
ambiguities and shortcomings in the existing field-based systems of textural
subdivision. We propose a revised textural zonation scheme that is broadly
compatible with the previous Hutton-Turner and Bishop systems, yet overcomes
their deficiencies. The main criteria for identifying textural zones (TZ) are
white mica grain size and foliation development. For field use, the main
features are: (1) restriction to first generation penetrative textures and
fabrics; (2) clarification of the definition and usage of segregation to better
distinguish TZIIB from III schist; and (3) grouping of TZIIIB and IV rocks
because of problems of protolith identification and quartz veining. The revised
system is applicable to both sandstone and mudstone protoliths.
Keywords schist; metamorphism; microtextures; foliation;
textural zones
New Zealand Journal of Geology & Geophysics, 2001, Vol. 44:
171-183
0028-8306/01/4401-0171 $7.00/0 (c) The Royal Society of New Zealand
2001
PDF file of entire paper: medium quality (3555K); (scanned from paper original: notes about this process)
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