Heat and pressure on metamorphic rock

[Dazzydogg]

Hello

 

I have to answer a question on the formation of metamorphic rock

 

Reffering to the relevant values of heat and pressure for rocks x and y describe the process involved in the formations of rock X and Y.

 

My question is, how would you describe the process, relating to the heat and pressure.

 

Thanks

[Ophiolite]

I am not going to do your homework for you, but - hopefully - guide you towards the answer.

 

Firstly, the question sounds rather badly phrased. Without knowing what rocks X and Y are it difficult to answer in any meaningful way,, without being very vague and unhelpfully general. Is that exactly how the questions was phrased?

 

Secondly, what thoughts have you had so far about tackling this? How does heat effect a rock? What kind of changes occur? What is it that is effected by those changes?

 

 

It would also be helpful to know what level this is pitched at. i.e. is this an introductory course in geology in the first or second year of high school, or for an A Level, or part of a first year degree course?

[Dazzydogg]

Thank you for your answer

 

This is for a first year degree course, Rocks X and Y are marble and slate. I have my answer as to the formations I am just confused as to how I would refer to the relevant values for pressure, temperature and depth. Would it just be explaining which temperature is needed for this formation to occur or that immense temperature may be needed? And would the diffrent temperature/pressure be indicative of the the type of rock?

[Ophiolite]

Thank you for the clarification. Well, the conversion of limestone to marble is, I think, primarily controlled by temperature. You would want to specify the temperature range over which the conversion occurs. Pressure will play a role, but I think it would be a secondary one. A standard text book should address these issues. (I think you will find that immense temperature is unnecessary, but you definitely want to be talking numbers, not adjectives.) You might wish to address the two ways in which the elevated temperature could be attained.

 

Formation of slate is influenced more by pressure, but again a certain minimum pressure will be required. Textbooks will address this, or find a recent research paper on the topic.

 

You certainly want to consider the changes in chemistry, mineralogy, and structure (macro and micro) that occur during the metamorphism, linking these to pressure/temperature ranges. The sort of thing that Eskola published back in the 60s, but updated with current knowledge/thinking would help you.

[studiot]

You should also look up slatey cleavage in the second case.