Amorphization of quartz is commonly associated with lamellae produced during an impact cratering event. Has anyone ever seen amorphous quartz closely associated with tectonic lamellae in non-impact quartz, e.g., from along fault lines?
This rock has some shards of pure glassy quartz (in the lighter coloured areas) inside this altered rock, probably a melt-rock inside the Gypsumville crater (220 my old, 40 km wide).
The target rock was limestone, so I presume the red stain came from the meteorite. I have run into very weird rocks within that crater, but did not do any studies on them. I compiled my information into a draft paper under my name.
Thanks, Michael. Have you ever seen any similar glass in an area with no crater?
I did observed amorphous quartz in fault zone but they were full 'grains' in very small zones in extremely deformed faulted rocks (in these small areas you can add highly localized heat from structural pressure). They were kind of passed the tectonic lamellea formation stage and got further deformed in term of pressure/heat. The tectonic lamellea in quartz that I saw in faults were in grains that show very obvious stretching and elongation due to the fault crushing movements but I did not find amorphous quartz in these lamellea. Strong deformations in quartz grains shapes (and other minerals) and in the rock in general are the key words for fault-induced lamellea, whereas in impact induced lamellea, there is quite often little to no tectonic-based deformation in the rock and minerals as I observed in the Carswell, Vredefort and the Charlevoix impact structures.
Francine Robert Michael Issigonis Hi, Francine and Michael. Thanks for your answers -- they were very helpful. Have either of you ever seen features like those on the attached TEM brightfield image of a quartz grain? The gold arrows mark thin lines of amorphous quartz. I'm curious about how would you interpret the image?
Hello Allen West
No I have not seen such quartz anywhere else. However, I haven't got much experience with microscopy.
There are others at RG who would provide knowledgable comments to your question.
I am familiar with the quartz from the Ries crater which they call coisite. That is the reason I cut those rocks to ask around for possible similarities.
Your work is very interesting, so is your picture above.
best wishes!
Michael Issigonis Thanks, Michael. How did you identify the coesite from Ries crater -- Raman?
Sadly I have no experience in TEM imagery. I mainly use a high end petrological microscope and SEM with backscattered electron imaging (BSE) and cathodoluminecence (CL). CL imagery is quite useful for revealing amorphous phases in quartz and other minerals.
Allen West
I didn't identify coisite in the Ries crater myself. It was Eugene Shoemaker who made a video on meteorites and visited Ries and sampled it.
I found the presence of quartz in the Gypsumville crater intriguing. It has not been described before from the limited number of investigators who did research there.
If you think my samples above are worth doing more research I could send them to you.
Michael Issigonis Hi, Michael. Your photos are very intriguing and look similar to some high-temperature glass we have seen at a few other impact sites. However, we have about two solid years of projects ahead of us, and reluctantly, we have decided not to take on any new projects for awhile until we catch up. Thanks for the offer -- you have a very interesting site.
- Badges
- Science topic
- Similar topics
- Geoscience
- Atmospheric Sciences
- Climate Science
- Climate Change