I don't think the rock colors reflect the composition of an impactor. Since most impactors are carbonaceous chondrites I would not go for its being "iron rich" but what do the experts find at Manicouigan? I have seen fossil meteorite clasts from Ordovician impacts in Sweden etc. They are identifiable with some difficulty.

I do notice the light colored material shows signs of soft deformation and the red material, not so much. The hard clasts seem like "red" material. The boundary between clasts and matrix is hard to see. Not really enough information to know if the rock is a penecontemporaneous fallback breccia. I've been to Sudbury and saw that fall back breccia and several other lithologies. I recollect it being mostly granule to pea gravel size heterolithic aggregate with a rock flour matrix. I've also seen some from Chesapeake impact and a few others...winslow etc. The coarseness of the red material and the intermingling of what looks like hard rounded red clasts and soft matrix filling material makes me think of a mudslide origin that might well be remobilized impactite mixed with the red stuff. Gotta chip out some of the white stuff and do a little panned concentrates. I'd hunt for shattered quartz grains. Same with the red (trachyandesite) stuff. Usually andesite isn't red. I work in the Andes...it's dull gray unless oxidized. The clasts may have undergone partial oxidizing and chemical degeneration but it isn't competely bleached because of permeability contrasts and solubility contrasts. Are there signs of remnant tectite dust? Sometimes there is enough to see. How about other material mixed in with the cementing agent. This is all just off the top of my head. I don't want to throw around too many stratigraphic lithologic terms from say Sudbury without refreshing my memory.

Hi Michael, the pink (hematite-altered?) rock seems to have porphyritic textures. Could it represent the trachyandesite mentioned above? If that is correct, the impact might have triggered the local injection of trachyandesite magma into the brecciated limestone unit.

Thank you Steve Johnson for your plethora of observations and the numerous examples you presented. That will give me plenty of suggestions to go through to get a better idea of what happened here.

I think there are signs of "impact melt spherules", as they call them today and the name of "pseudotachylite" is one name described by some from this crater.

Unlike the Andes gray rocks, my area had lots of iron when I was cutting the impact rocks I got plenty of red clay that painted even the saw machine!

Thanks again for your variety of suggestions.

Thank you Daniel Müller for your contribution. There are indeed many fragments that resemble porphyritic texture.If the rock is from the impact (which I think), researchers elsewhere describe them as melt grains or melt spherules, most are mm size and plenty of small rounded (previously) gas bubbles.

The red color is intriguing because the country rock is limestone. The impact created rocks like trachyandesite and pseudotachylyte, but there is also clear quartz which might be coesite due to the high pressures involved during impact.

Dear Dr. Issigonis,

I can only macroscopically compare the red central fragments displaying some kind of a porphyritic texture with known impact rocks. It can be described as the so-called suevite which occurs in different colors from gray to red and results from an impact-induced molten material ("lava"). It can easily be mistaken for a volcanic brecciated material . With this in mind and soley based on its outward appearrance calling it a “trachyandesite” is not anything out of the ordinary. The yellow material has obviously been derived from the calcareous country rocks which underwent shock metamorphism. My statements are based on personal observations during a visit paid to the Nördlingen Ries Crater which is a well-defined Miocene impact in SE Germany which shows all features from true impactites (suevite) to syn-impact backfill sediments (colored breccia) and post-impact lacustrine marly crater sediments.

Kind regards

H.G.Dill

Dear Michael (Dr. Issigoris),

As it is now and so many times we can read a beautiful response from Herald G. ( Prof. Dill)... I think you can consider resolved your question.

I have only a small practical experiment, but my insight looking onto the area wake up the next idea that the origin of the crater is 'absolute acceptable like an impact crater' did not was caused by an explosive volcanic eruption... 'Volcanic brecciated material ' materials are forming in such a condition... I did not verify what kind of eruption producing such a type of lava... If the zone in the volcanic rocks can find an anomaly geochemical (increase in rare earth elements) can give such an opinion that your samples have volcanic origin...

Regards,

Laszlo

Thank you Harald G. Dill and László Attila Horváth for your valuable contributions.

This crater was originally described as a volcano and was accepted as such for a long time. Later on the government did some drilling and discovered the central peak of granite as well as two annular rings occupied with granite. In between these granitic areas were lava-like rocks, breccia and gypsum deposited from an inland sea. I tried to locate shatter cones without success. However, within the crater I found the rocks pictured above which I hypothesize would be the result of the meteorite impact.

Although the impact crater is one of the biggest in the world, not much research has been carried out. There are lots of peculiar rocks within the crater that represent target rocks that have since been weathered away.

Dear Michael Issigonis,

Thank you for valorous response with some details.

Exactly as supposed in connection to the mentioned crater have to exist granitic rock… I am supposing that this granite is A-type… So the crater has to be volcanic crater (only opinion)… the ‘trachyandezit’ origin is connected to the granitic magma: (with the actual theory can be said that its origin at crust-mantle contact… The shatter cones fragment can be the ‘trachyandesit’ fragments, another think if you have possibility to get data from Indonesia in connection with Krakatoa… In case of Stromboli (Italy) is not so evident, but its study is easier and exist possibility to get such an information which can give you opportunity for an better understanding same study of:’ Nördlingen Ries Crater’ mentioned by Herald G. ( Prof. Dill).

Regards,

Laszlo

Michael Issigonis

One perhaps related comment - in systems where limestone is subjected to metamorphic conditions then marble is a common outcome. One classic region is on the Isle of Skye in the Broadford region (and on Iona to a lesser extent). The (marble) color there can vary from white, through yellow, to green. For example:

https://www.therockgallery.co.uk/skye-marble-----isle-of-skye-scotland-2877-p.asp

The geological explanations are to be found in ,many places:

http://nora.nerc.ac.uk/id/eprint/7449/1/CR06075N.pdf

One of the most decisive features to corroborate the theory of impact structures are shatter cones

Thank you Alan F Rawle for your suggestion and very interesting publications re Island of Skye.

The limestones in and around the St. Martin meteorite crater were subjected to very violent conditions and no marble or other metamorphosed rocks have been located. Instead, there are many lava-looking rocks and others such as those described above with an abundance of calcite and red coloration.

Thank you László Attila Horváth and Harald G. Dill for your continued contributions and suggestions.

Although the nature of the rocks in and around the St Martin crater have been studied by many investigators no shatter cones have ever been found. This is also the case with another crater in the USA which is also hosted in limestone and dolomite. The presence of the central peak and annular rings proved the collision with a meteorite took place here. However, the crater is quite large and additional studies might find new sources of evidence. It is interesting that the rocks that I came across were not described by previous investigators.

Dear Michael Issigonis,

As it seems you are doing god job!

Before, you have mentioned a very important observation: ‘It is interesting that the rocks that I came across were not described by previous investigators.’ You have to find the response: ‘why?’ another thing if you have opportunity to get information somewhat about the crater surrounding: neighbor areas rock, stratigraphy (from bore holes, natural openings, seismic profiles and correlate it with the bottom of crater … The information is present in the researched region:… what happened, and how happened… Every time try to understand in most simple ways as it possible…

Regards,

Laszlo

It is likely the result of meteorite impact

Dear Michael Issigonis,

Yesterday I looked onto the form of the studied crater by you... the time of crater... one thing is interesting that its creating time 'was closed' to two extinctions: Permian–Triassic extinction event (End Permian): 252 Ma at the Permian–Triassic transition, and Triassic–Jurassic extinction event (End Triassic): 201.3 Ma at the Triassic–Jurassic transition. The form of the crater same suggests that is an impact crater... But I am remaining the position that is a volcanic-impact crater... In many ways, I have a different idea of Earth-tectonic changes like the mainstream... I was got acceptable answers onto question which was asked by myself when I was in college,... I hope that you have the opportunity to test such a hypothesis...

Regards,

Laszlo

Dear Dr Issigonis,

Discovering of a meteorite fragment(s) embedded in any of the rocks within your study area would be a very significant to prove the meteoritic impact theory.

Regards,

Shad

Thank you Dear László Attila Horváth for your valuable contributions.

You certainly have a point. This crater had been called a volcano for many years until the government put a series of drill holes to study it. After the drilling was studied it was decided to change the volcano into a meteor crater with a probable age of 215 my. With that age there were another 5 bigger and smaller craters around the world with similar ages, so it was decided this multiple crater event was created by a large asteroid broke apart into smaller fragments, but big enough to create the Manicouagan crater in Quebec (100 km diameter) and other smaller ones. All craters had the same paleolatitude at 215 my ago, so they were part of the same asteroid.

Several independent investigators also contributed taking samples and doing their own interpretation. I took my students for field trips into the crater and they were all very impressed.

I think the matter is still under investigation. There ought to be an international conference on this major crater to discuss all aspects of its geology. In the meantime, the place is open to any investigators to carry out any type of research.

Thanks again Dear László Attila Horváth for your continuing discussion on this and other subjects. It is through discussion that many problems are solved.

Thanks Shadrach K. Noku for your suggestion. It has been the target of previous studies, especially the drilling project carried out within the crater.

No such fragments have been found yet. The core is kept by the government and is available to anyone to study it. I had looked at some of that core, just to see the terminology of rock types that the study described by the authors.

In the meantime, I found out different types of rocks not encountered in that drilling which were "lying around" on the surface pits, which I am trying to describe now.

The amount of surface investigations done over the years on this 40 km-wide crater is very limited.