Lab 5B-Thin sections of veins
CET/UWA Microstructure Course
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| Lecture 1
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| Lab 1 a
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| Glossary Table
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Index
| GEOS5505 Lab 1
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(4) Thin sections of veins
The thin sections show a variety of structures that have been discussed
in the lecture. Have a look at them and answer the following questions:
- What is the grain shape (e.g. fibrous, elongate-blocky,
etc.)
- What is the vein type (e.g. antitaxial, syntaxial,
etc.)
- What can you say about the opening history of
the veins (opening trajectory, propagation, etc)
- Are there any other microstructures that relate
to veins and dissolution-precipitation processes
In short: What can you see and what does that
tell you about what happened?
Group 1: Calcite veins from dolomitic shales near Arkaroola (SA). Several of these images are courtesy of Michelle Robinson, who completed her Honours degree on these rocks. Some of the thin sections show the tip of veins, with complex
structures around it (as shown here).
Larger apparent crosscutting vein structure with smaller actual
crosscutting structure. Mostly fibrous calcite,
with minor blocky calcite and quartz is present. Cross polarised light, field of
view of overview is 4 cm.
What are the vein age relationships (e.g. antitaxial, syntaxial,
etc.)
En echelon vein structures in the field (horizontal field of view 40cm) and in thin section (horizontal field of view 7.5cm).
What is the sense of displacement in each image.
Highly disrupted vein network formed between two faults (oriented about 15 degrees clockwise from vertical) with bedding in shale bent by faults.
Group 2: Several mainly quartz bearing veins from Poolamacca, Victoria
and Arkaroola. The Arkaroola ones also contain anatase (Ti-mineral), with
pretty structures to have a look at.
