There are already posted questions (and answers) for the meaning of となる as a similar pattern to になる, but with a sense of finality.
However, I've come across the following sentence
where なる as a meaning of "consist" or "be composed of".
My question is, how is the となる construction affected if なる does not have the usual meaning of "becoming", but one of "consisting"? Specifically, what is the meaning of the bold part?
For clarity, I already know that なる can mean "to be composed of". What I'm looking for is the nuance of に vs と when なる is used with this sense.
With the "become" meaning, と adds a sense of finality, like "has finally become". What is the corresponding nuance in with "composed of"? "Has finally become composed of" does not make sense in the example sentence...