Metaphoric Rock and Regional Metaphorism

Metaphoric Rock and Regional Metaphorism

In Geology, metaphoric rock is a rock that was another type before it was changed while on earth thus becoming a new type of rock. Protolith is the term used to describe the type of rock the metaphoric rock used to be before metaphorism took place. The process of metaphorism involves the mineral context as well as the texture of the protolith changing because of chemical as well as physical factors associated with the environment. There are several cases as to why metaphorism occur and they include tectonic stress, heating by magma, burial or even the alteration by fluids. When the metaphorism continues to an advanced stage, the metaphoric rock is likely to develop different set of minerals and the texture also may change entirely that it may be difficult to realize what the protolith was. There are two main form of metaphorism regional and contact metaphorsim as will be discussed in this essay

Grade of Metaphorism

I will be looking at the grades of metaphorism that exist and factors that affect them. When the pressure and/or temperature increases in the body of a rock, the rock undergoes a process referred to as the prograde metaphorism, in other words the grade of metaphorism also increases. Metaphoric grade is a term that is often used in the description of relative pressure as well as temperature where metaphoric rocks begin to form. My graph will include a graph that portrays Temperature against pressure. The P-T paths shows relationship of metaphorism through pressure, temperature and time.

Figure SEQ Figure * ARABIC 1Pressure-time path

Figure SEQ Figure * ARABIC 2: Graph Showing relationship between temperature, pressure and metaphorism

Reference

White, C. E., & Barr, S. M. (2012) Meguma Terrane Revisted: Stratigraphy, Metamorphism, Paleontology and Provenance. Geoscience Canada 39(1).