Hi all
I see everyone is introducing themselves and I feel somewhat obliged to do the
same.
My name is Malcolm Dixon and I am a Metamorphic Geologist / Geochemist studying
towards a M.Sc. at Victoria University in New Zealand.
The basic aim of my research is to work out the metamorphic history for a
section of the Southern Alps, South Island New Zealand. The Southern Alps lie
to the east of and have been exhumed by the Alpine Fault, the boundary between
the Pacific and the Australian plates. At the highest grade the exposed schist
is garnet-oligoclase bearing.
I am using a mix of thermometry and barometry techniques, with garnet growth
dates and a fluid inclusion study to build a P-T-t path for the region. In
addition, constraints on the overall geological and metamorphic history of the
wider study area are being obtained through a study of a thin suite (500m) of
garnet-kyanite-sillimanite gneiss collected from the western side of the Alpine
Fault.
In places against the fault, the schist is absent of garnet, and sometimes even
biotite, yet rocks a few kilometers along strike, identical in appearance can
have up to thumbnail sized garnets. However rocks that lie further from the
fault (~4-5 km) do have garnets, (microscopic), these garnets seem to occur in
bands of higher graphite content, or in regions were the schist has a slightly
greener coloration. My initial feeling is that the garnet growth is being
controlled by the bulk rock composition of the original protolith, and/or some
sort of fluid interaction. I am awaiting isotope data to identify the types of
fluids that have been present, and have only just started examining my bulk
rock and trace element data from the XRF.
If anyone had any ideas or references on this I would be extremely grateful.
Many thanks
Malcolm
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Malcolm Dixon
School of Earth Sciences
Victoria University of Wellington
New Zealand
Ph 00 64 04 4635233 x8408
Fx. 00 64 04 4635186
[log in to unmask]
http://www.geo.vuw.ac.nz/
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