Hello,

I do not think it is necessary to create a new definition of metasomatism because it already exists. It's still a pretty complicated problem. This is defined (Zharikov et al., in: Fettes D. and Desmonds J. ed.., (2011): Metamorphic rocks - A Classification and Glossary of Terms. ) as:

"a metamorphic process by which the chemical composition of a rock or rock portion is altered in a pervasive manner and which involves the introduction and/or removal of chemical component as a result of the interaction of the rock with aqueous fluids (solutions). During metasomatism the rock remain in solid state."

From this definition (it is the official definition of IUGS) it is also clear that metasomatism has no direct relation to magma or its differentiates. An indirect relationship can, of course, exist. Metasomatism can be taken as a "hydrothermal metamorphism" with substance transfer.

Whether fluids originate from a volcanic or metamorphic process should be due to the geological context and geochemical signature.

Dear sir Dalibor Matýsek,

I very happy you have clarified my doubt on the basics of the term "metasomatism". Thank you very much.

With reference to point no.4 in my question above, can you comment something on an igneous process, which has a residual fluid portion (left from a crystallizing magma) that escapes and interacts with the earlier formed rocks? If this is not a type of metasomatic process, then what type of process should I look into?

Perhaps, I am not clear with this sentence {An indirect relationship can, of course, exist. Metasomatism can be taken as a "hydrothermal metamorphism" with substance transfer}. Can you please kindly elaborate a little bit more or may be a few references will be highly appreciated.

Thank you very much sir 😊.

Hi,

It will be good if you read the above book on metamorphic rocks. Various contact metamorphic / metasomatized rocks are associated with volcanic rocks. These are different types of hornfels, skarns and similar rocks. Metasomatism is most marked in albite contact hornfels, ie adinole series rocks, and in tactite-type contact skarns. From my private observations, it follows that a certain metasomatism occurs at slightly higher temperatures or pressures at any petrological interface.

I have some reservations about point 4, as formulated in the original question.

"4. It is an igneous metasomatic process when the last remaining fluid portion of a crystallizing magma escapes and interacts with the earlier formed rocks."

If the last remnants of magma mean any melt (above the subsolidus), then it is not metasomatism, but perhaps migmatization. However, if fluid phases (such as supercritic fluid) are meant as remnants of magma, then metasomatism is an option. For example, greizens are sometimes interpreted this way

Other study literature:

https://link.springer.com/book/10.1007%2F978-3-642-28394-9

https://sp.lyellcollection.org/content/293/1/1.short

https://www.springer.com/gp/book/9789811006654

https://www.springer.com/gp/book/9789027726186

Thank you for your help and valuable time sir Matýsek.

Dear Damepaia S M Pdah thank you for asking this interesting technical question on RG. In this context please have a look at the following potentially useful article which might help you in your analysis:

Fluid-induced processes: metasomatism and metamorphism

Article Fluid-Induced Processes: Metasomatism and Metamorphism

Unfortunately this paper has not yet been posted as public full text on RG. However, one ofthe authors has an RG profile (https://www.researchgate.net/profile/Hakon-Austrheim). Thus there is a good chance that you can request the full text directly from this author via RG.

Regarding the difference between igneous and metamorphic metasomatism the following link might be helpful:

Top 7 Differences between Metamorphic Rocks and Igneous Rocks

https://www.geologyin.com/2016/06/top-7-differences-between-metamorphic.html

Good luck with your research and best wishes!

Dear Frank T. Edelman, thank you for your support and guidance. I will get back as soon as I have gone through them.

Dear Sir Jorge Costa-de-Moura,

Thank you for the detailed and refreshing comments and feedback.

Can I call my point no. 4 in the original question as "autometamorphism"?

Thank you again.

In ancient Greek the term "meta" stays for "over", the term "soma" stays for "body" and "morphos" stays for "shape".

Metasomatism is a natural process that leads to the change of the essential characteristics of a rock body (the "soma"). It can be either modal (with the formation of new minerals crystallized from "metasomatic" infiltrating agents) or cryptic (i.e., identifiable only on the basis of enrichment of specific groups of elements). Occasionally it can be both modal and cryptic. It is used as a magic word when geochemists (and petrologists) do not say how to explain the origin of the rocks they are investigating. Poorly defined "metasomatic processes" are often used when there is no exit.

Metamorphism is a natural process associated with variation (not only increase) of pressure and temperature. What officially change are the shapes and the forms of the minerals (i.e., the "morphos"). Very commonly, new minerals form when T-P conditions (but also the oxygen fugacity) change. A classical discontinuous reaction is albite = jadeite + quartz, but there are hundreds of reactions like this. Officially metamorphism leaves unchanged the pristine rock composition (i.e., a basalt has the same composition of the high-pressure equivalent eclogite), but in reality what we observe is nearly always a fluid enrichment/depletion and some variation in strongly mobile elements.

Good luck for your studies,

Michele

Metamorphism is an isochemical adjustment (be it contactmetamorphic, regional/dynamometamoprhic or burial metamorphic) to changing physical conditions pressure and temperature in the lithosphere. By definition the expulsion of carbon dioxide and water along with an increasing metamorphic grade is not involved in these processes. The lower limit called the very low-grade stage overlaps with the upper part of the diagenesis (around 200°C) and depends on the angle you look at this boundary using siliceous, organic or sulfidic matter. The upper limit is the onset of anatexis between 600 and 800°C which depends on the water content of the system. The metasomatism sensu stricto is a closed system.

Metasomatism is allochemical and an open system where in special zones at a certain P-T level a new mineral partly or wholly different in its chemical composition from the host mineral formed. These mineralizations may be caused by subcritical or supercritical solutions sparked by igneous bodies at different depth (contact -metasomatic / skarn) or in the course of burial or dynamometamorphic processes (see the isochemical analogues above). The replacement of preexisting rock-forming material occurs through chemically active liquids and gases from external sources.

Thank you very much Sir Harald G. Dill for your valuable time and explanation.

My research idea on a problem I am working is becoming clearer and better. Your comments triggered some idea and confidence in the direction I am taking. Thank you sir.

Hi Damepaia S M Pdah

Excellent question,

Please find a relvant study to your question here.

1. igneous and metamorphic metasomatism https://www.tandfonline.com/doi/abs/10.1080/00167615908728504?casa_token=ggipbOUllFEAAAAA%3Al9gU7be7AoBw_K7Goi2OwORDZ-rgiyNr4WPOsMIntVLpNzwlkyO4-Tc22JAfcS9nfGwDaeZWW0Y&

2. https://www.sciencedirect.com/science/article/abs/pii/S0016703718305362

Best Regards,

SHA