New Zealand Journal of Geology and Geophysics abstracts

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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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