Questions tagged [metamorphism]

questions relating to solid-state recrystallisation of rocks, including (but not limited to) conditions, chemical reactions, and geobarometers and geothermometers

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Isotopic dating of metamorphic rocks

I read in my physical geology textbook that sedimentary rocks cannot be dated using isotopic dating, because they are formed from fragments of other rocks and minerals, which if you were the subject ...
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Phase rule for akf triangle diagram in the field of metamorphic rock lithography

Why does the number of components become 3 when calculating the phase rule of rocks consisting of MS and Chl. According to the Goldschmidt's minimal phase rule, in most cases, the degree of freedom of ...
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Any recommendations for a good online lecture series on Metamorphic Petrology

Any recommendations for a good online lecture series on Metamorphic Petrology? Thank you in advance.
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171 views

When sediments are deposited, do they sink into the earth?

I was listening to a geology podcast describing how sedimentary rock forms and later turns into metamorphic rock. As a river lays down sediment, the lower layers can eventually be several kilometers ...
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1answer
78 views

Does muscovite occur as a contact metamorphism mineral?

Does muscovite occur as a contact metamorphism mineral, with dacitic intrusion into dacitic rocks?
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1answer
17 views

Where can I find papers on the geology of the Wastach Range in Utah

I am looking for papers on the stratigraphy, geochronology and/or compositional make up of the Wastach Range and its formations. I prefer a broad overview paper and I can't seem to find one. Any help ...
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1answer
1k views

What is the metamorphic field gradient useful for?

As I understand it, the metamorphic field gradient is the PT line traced out by the maximum temperature points of a series of PTt paths of rocks from the same metamorphic event. What exactly is this ...
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1answer
564 views

Which geological processes will destroy plastic?

The geological record at the end of the Anthropocene will undoubtedly contain large volumes of plastic. However, some geological processes will completely destroy plastic (e.g. magmatic or chemical ...
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2answers
760 views

Does grade of metamorphism apply to igneous and sedimentary rocks?

Does grade of metamorphism apply to igneous and sedimentary rocks? I know that grade of metamorphism applies to the scale in which a rock becomes crystallized. Or is it? Please also define grade of ...
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4answers
4k views

When metamorphic rocks undergo pressure, how are they changed?

When metamorphic rocks undergo pressure they are changed, but how are they changed? Do they become fragments of rocks? Doesn't that mean that the difference between sedimentary rocks and metamorphic ...
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1answer
847 views

are laccolith, lobolith, dikes and sills formed of porphyritic texture?

Laccolith, lobolith and batholith are shapes of igneous rocks which exist below the surface of the earth, dikes and sills too. And the way they formed by makes me think that they have a porphyritic ...
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2answers
5k views

How do the swirls and veins in marble form in detail?

I am finding surprisingly little information about this. I imagine that the process is somewhat like foliation except because the particles that go into marble (to my knowledge) don't have any ...
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1answer
78 views

Identifying serpentinite reworked during high-T metamorphism

What kind of mineralogy results when a serpentinite is reworked during high-T or UHT metamorphism? I am envisaging a possible scenario where an obducted ophiolite terrane is buried and metamorphised ...
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365 views

What is the age of the earliest traces of life on Earth?

In the article Oldest rocks, earliest life, heaviest impacts, and the Hadean–Archaean transition (Moorbath, 2005), the author states (based on previous referenced research) that the $\ce{^13C}$ ...
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Exhumation of blueschist

Blueschist has a mineral assemblage such that it must have formed at high pressures and low temperatures. It must therefore form in subducting slabs (and I believe this correlates with the locations ...
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545 views

Can concretions form in non-sedimentary rocks?

Most modern works (e.g. Nichols 2009; Allaby & Allaby 1999) seem to restrict the definition of ‘concretion’ specifically to formations in sedimentary rocks. I have recently come across a taxonomy ...