Hey Willem,

Nice thin section picture, and actually a good question. From my own experience, PDFs in olivine can be hard to recognize under the optical microscope. Usually, what we can easily identify are planar fractures (PF; often filled with opaque material; in meteorites commonly "shock-darkened"). Like in quartz, planar fractures are wider and commonly open, in contrast to real PDFs. Frankly, I cannot see any unambiguous PDFs in the olivine grain you presented; but that doesn't mean they're not there. Some PF seem to run approximately NE-SW, moreover, the Ol crystal probably contains numerous tiny fluid inclusions.

The best way to analyze these possible PDFs would be using the transmission electron microscope (TEM), or possibly a scanning electron microscope with a cathodoluminescence detector (SEM-CL). 

A very good reference is the following paper by Dieter Stöffler and colleagues: http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&uact=8&ved=0ahUKEwiX-paTm8PJAhWBoD4KHch9BNYQFgg9MAM&url=http%3A%2F%2Fwww.higp.hawaii.edu%2F~escott%2FStoffler%2520Keil%2520Scott%25201991%2520GCA%2520shock%2520metam.pdf&usg=AFQjCNEYH8S5zABEH3SWOncGnFPWB7hZuw (this link literally opens a PDF file);

as well as this paper by Falko Langenhorst: http://www.geology.cz/bulletin/fulltext/03langenhorstfinal.pdf

Good luck! May I ask you which (terrestrial?) impact site this thin section is from? Vredefort? Lonar? Or one of the Brazilian, basalt-hosted, impact structures?

All the best,

Martin

Thanks Martin! I'll try to analyze the sample with an electron microscope soon!

This particular thin section is from the Vredefort Dome.

Dear Willem,

Perhaps the below mentioned article provides answers to the question of planar deformation features in olivine:

Mechanisms of plastic deformation of olivine

by

C. B. Raleigh

In: Journal of Geophysical Research

Vol. 73, Issue 16, pages 5391-5406

First published: 15 August 1968

DOI: 10.1029/JB073i016p05391

Abstract

Olivine deformed experimentally at 5-kb confining pressure undergoes plastic flow by slip on several systems. The active slip system is determined from microscopic study of slip bands, deformation lamellas and kink bands. At temperatures less than 1000°C the slip systems are {110} [001], (100) [001], and (100) [010]. At 1000°C, slip on {0kl} [100], pencil glide in [100], the system shown here to be predominant in naturally deformed terrestrial olivine, occurs in addition to the system {110} [001] and becomes the predominant mechanism with decreasing strain rate. Dependence of glide mechanism on temperature and strain rate is also observed in diopside. Data of the sort acquired in these experiments may be used to place limits on the possible temperatures and strain rates of naturally deformed rocks.

Best regards,

Guenter

I would do ebsd to see if your planes align with any of the known pdfs in olivine. Firstly it would be nice to see a cross polarization image