16 March, 2008

What Phyllites can give you...

...when you treat them nice and with care is organic-walled microfossils! Yep, I managed to get a few (only 3) well preserved (hear the sarcasm!) chitinozoa out of highly metamorphosed rocks of the Erzgebirge! My professor read and loved my report (meaning I cannot be too wrong) which is wonderful news! This is the first time I was told "it was a joy reading it"! Ok, enough exclamation marks! As I wrote in an earlier post I made a handful of thin section to examine with a polarisation microscope in the hope to prove or disprove the presence of organic-walled microfossils in these so far undescribed rocks. My seminar paper grew to 18 pages and far beyond the initally set aim of 8 but fortunately only to add a lot of detail and quality as I think. I never worked on organic-walled microfossils before, and actually I never work with fossils because I'm deeply into mineral deposits, but this was really fun. Also I have to admit it is amazing what can be done with a budget of exactly 0 Euros. It did cost me a lot of time in the lab to prepare the thin sections myself and I surely was an annoyance to the poor lab technician who had to demonstrate me everything. So what did I find? These:

A slender chitinozoan example.

This one is getting a bit rounder...

...just like this one, as well. Perhaps they are related.

Above you see 3 neat microfotos of the suspects sought. They are all a bit tiny in comparison to the literature but still within the realm of the possible. Considering the results and occurence time of chitinozoa I dismissed my original ideas and decided these must be part of the Hermsdorf Phyllites. Precambrian or Upper Carboniferous chitinozoa would have been a bit of a far fetch and the rock samples themselfs shared more characteristics with Graphite-Phyllites than Precambrian or Carboniferous Schists. I still should mail this seminar paper to the mine geologist who originally gave is the task to map out the Hermsdorf Phyllites. If I remember correctly he once told me it would be a first to find microfossils in those rocks. So these are Ordovician chitinozoa. Cool. Also cool are some metamophic microtextures. Here you go:

A nice foto of crenulation cleavage under the microscope. Note the quartz in the centre and clay minerals and organics at the sides.

Parallel foliation and segregated quartz. There is no foto of it but it forms a very nice mosaic in another sample.

Quartz with I assume fluid inclusions and signs of dissolution.

Well, enough of micro-palaeontology and metamorph rock fabrics. Hope you liked it! :-)


Silver Fox said...

I have always like phyllites, and these seem to be very interesting. Those microfossils are so tiny - will you also use other methods of viewing them like an SEM? Glad you are finding such interesting things! (Oops, another exclamation point.)

The Lost Geologist said...

I wish I could! But as I wrote I didn't get any funding for this seminar paper. So I had to with what I could get for free. Preparing the samples and extracting the mircofossils would be quite a lot of work I couldn't do on my own or at least not without assistance because I never did that before. The chemicals for the extraction and the prepetation and use of the SEM would also cost. So only way to get some funding for that would be to make a master thesis about it, however, as much as I like this, I want to do my thesis about mineral deposits. Likely some MVTs in Peru, not chitinozoa from the Erzgebirge.