Thin section imaging

Images made through a microscope. All subject types.

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Andy Resnick
Posts: 40
Joined: Tue Apr 25, 2023 4:38 pm
Location: Cleveland, OH

Thin section imaging

Post by Andy Resnick »

I was able to reproduce a few images appearing in:

Verschure, R. H. & Maijer, C. 2005: A new Rb-Sr isotopic parameter for metasomatism, ∆t, and its application in a study of pluri-fenitized gneisses around the Fen Ring Complex, South Norway. Norges geologiske undersøkelse Bulletin 445, 45–71.

Here's a piece of the published image (this is an open-source paper, btw.)
Untitled.jpg
and mine (I have 3 of the 4 above samples):
DSC_1907.jpg
DSC_2052.jpg
DSC_2056.jpg
Here's the relevant part of the figure caption:

Fig. 10. Photomicrographs of fenitized gneisses. […].

(c) Ma 88: Biotite with reaction rim of massive Na-pyroxenes and alkali feldspar due to Fenitization-1. The rim was formed where biotite was in contact with quartz (clear) and not where biotite was in contact with feldspar (turbid). Other biotites within the same sample (not visible on this photomicrograph) appear stronger or even completely replaced. Location of the sample: Small quarry for road material near Steinsrud on road Holla-Steinsrud, Økonomisk Kart Foreløpig Utgave 1971 (BV 030-5-4) coordinates: 51502- 656890.1.

(d) Fen 125: Biotite replaced during Fenitization-2 by radiating needles of bluish Na-amphibole, subsequently partially replaced by fine- grained magnetite and hematite. The replacement occurred where biotite was in contact with quartz. Other biotites within the same sample appear unaffected or completely replaced. The sample was taken 1750 m south of the Fen Complex, far outside the zone of Fenitization–1. Location of the sample: HSP post M00059, Økonomisk Kart Foreløpig Utgave 1971 (BW 020-5-1) coordinates: 138965-51753. […]

(f ) Fen 33’’’: Biotite with a rim of a massive aggregate of blue Na-amphibole pseudomorphing Na-pyroxenes. Stilpnomelane (brown radiating flakes) occurs at the edge of the blue Na-amphibole aggregates. Location of the sample: Håtveittjørn Section 375 m from the contact with the Fen Complex.

For me, this kind of information is really useful- not for the technical detail- I don't yet have enough knowledge to fully appreciate them- but rather (1) I learn how a geologist looks at samples, and (2) for the experience observing how color is used as a identification tool- I can't rely on color names to identify the mineral. For example, now when I read "bluish Na- amphibole", I understand what that color looks like to my color-deficient eyes. That holds especially for green/brown minerals.

Also, "stilpnomelane" :)
stilpnomelane.jpg

Pau
Site Admin
Posts: 6033
Joined: Wed Jan 20, 2010 8:57 am
Location: Valencia, Spain

Re: Thin section imaging

Post by Pau »

Interesting!
So you have access to the original thin section slides and you are reproducing the same frames, do you?

I love petrographic thin sections but metamorphic rocks mineralogy is too much for my level.

About colors beware that some of them, specially as shown in the crop picture are optical chromatic aberrations, not interference colors
Pau

Andy Resnick
Posts: 40
Joined: Tue Apr 25, 2023 4:38 pm
Location: Cleveland, OH

Re: Thin section imaging

Post by Andy Resnick »

Pau wrote:
Tue Aug 29, 2023 2:24 am
Interesting!
So you have access to the original thin section slides and you are reproducing the same frames, do you?

I love petrographic thin sections but metamorphic rocks mineralogy is too much for my level.

About colors beware that some of them, specially as shown in the crop picture are optical chromatic aberrations, not interference colors
Yes- During the summer I came into possession of what I believe are research materials of R. Verschure, an academic geologist who was at the Geological Institute of Amsterdam. One of the reasons I agreed to purchase the set is that he published research using these samples, so I am (kind of) teaching myself some geology. Or at least pretending to teach myself some geology. :)

Most of the samples were taken from the Fen Complex near Oslo- carbonitates and a lot of diatreme-facies examples. Really wild stuff!

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