New Zealand Journal of Geology and Geophysics abstracts
Provenance analysis of the Paparoa and Brunner Coal Measures using integrated SEM-cathodoluminescence and optical microscopy
Kari Bassett
Franz Ettmuller
Department of Geological Sciences
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
kari.bassett@canterbury.ac.nz
Matthias Bernet
LGCA
Université Joseph Fourier
38000 Grenoble Cedex 9, France
Abstract An integrated approach using
grain-by-grain comparison of SEM-cathodoluminescence (CL) and
petrographic characteristics was applied to investigate the provenance
of fluvial/lacustrine quartz-rich lithic arenites deposited in the Late
Cretaceous transtensional Paparoa Basin in New Zealand. Results show
most quartz in the Paparoa Basin was derived from a relatively low
grade metamorphic source, most likely the underlying metasedimentary
Greenland Group. This interpretation is supported by the presence of
sedimentary lithics and Greenland Group conglomerate clasts in the
Paparoa members. The eastern part of the basin is characterised by the
addition of detrital chlorite and muscovite, some clearly replacing
potassium feldspar in retrograde metamorphic lithoclasts, the lack of
plutonic quartz, and an increase in polycrystalline metamorphic quartz.
All this indicates an increase in metamorphic grade of the source area
to the east upward through the stratigraphic section followed by a
decrease. Such a change in grain type most likely reflects the
migration of the basin past the exposed metamorphic rocks of the
Paparoa Metamorphic Core Complex to the northeast of the strike-slip
Paparoa Tectonic Zone. On the west side of the basin, c. 15% of
quartz grains are also derived from a plutonic source, probably the
Barrytown Granite pluton or similar intrusions. Our provenance
information provides the first concrete evidence for sinistral
strike-slip fault movement as predicted by tectonic reconstructions.
Keywords Paparoa Coal Measures; Brunner Coal
Measures; SEM-cathodoluminescence; provenance; Greymouth Coal Field;
sinistral strike slip
G05017; Received 27 April 2005; accepted 17 February 2006; Online publication date 17 May 2006
New Zealand Journal of Geology & Geophysics, 2006, Vol. 49: 241–254
0028–8306/06/4902–0241 © The Royal Society of New Zealand 2006
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