DOC PREVIEW
GSU GEOL 1122K - Chapter 7 Textbook Annotations

This preview shows page 1-2-3-4-5 out of 14 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 14 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 14 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 14 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 14 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 14 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 14 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

7.1 Introduction- James Hutton o 18th century - Metamorphic rock o Meta  Change o Morphe  Form o Metamorphic rock  A rock that forms when a preexisting rock - Protolith o Undergoes a solid-state change in response to themodification of the environment.  This process of change is called metamorphism o By Solid-state  Metamorphic rock does NOT from by the solidification of magma.- That is an igneous rock. o By change  Metamorphism produces new minerals that did not occur in the protolith,and or produces a new texture (arrangement of mineral grains) that isdistant to that protolith. o By modification of environment  Metamorphism takes place when a protolith endures a rise or fall intemperature and or pressure, undergoes compress and shear, or reacts with“hydrothermal fluids” (very hot water solutions) o Forming of metamorphic rocks  1. Some metamorphic rocks are adjacent to igneous intrusions- So, metamorphism can take place when heat from an intrusion“cooks” the tock which it intrudes.  2. Some metamorphic rocks occur over broad regions in the absence ofintrusions - So, metamorphism can also take place when rocks end up at greatdepth beneath Earth’s surface. 7.2 Consequences and Causes of Metamorphism - What is a Metamorphic Rock?o First Can possess metamorphic minerals - New minerals that grow in place within the solid rock only undermetamorphic temperatures and pressures. o Can produce a group of minerals that make up“metamorphic mineral assemblage”o Second  Can have a metamorphic texture - Defined by distinctive arrangement of mineral grains that are NOTfound in other rocks. o Textures results in a metamorphic foliation.  The parallel alignment of platy minerals and or thepresents of alternating light-colored and darkcolored layers. o When metaphorical minerals and or textures develop, a metamorphic rockbecomes different from its protolith.  This takes place very slowly- Thousands to millions of years o Involves serval processes, which can occur alone ortogether.  The most common processes: - Recrystallization o Changes the shape or size of grainswithout changing the identity of themineral making up the grains. - Phase change o Transforms one mineral into anothermineral with the same compositionBUT a different crystal structure. o Phase change involves therearrangement of atoms. - Metamorphic reaction or neocrystallization o New o The growth of new mineral crystalsthat differ from the protolith o During neocrystallization, chemicalreactions digest minerals of theprotolith that produces new minerals.- Pressure solution o When a wet rock is squeezedstrongly in one direction more thananother. o Mineral grains dissolved where thesurfaces are pressed against othergrains. o This produces ions that migratethrough to water to from aprecipitate. - Plastic deformationo When a rock is squeezed or shearedat elevated temperatures andpressures. o Grains behave like a soft plastic andchanges shape without breaking.  Rocks undergo metamorphism when they aresubjected to heat, pressure, compression and shear,and or very hot water. - Metamorphism Due to Heating o When you heat a rock, it transforms into a metamorphic rock.  Heat causes the atoms to vibrate rapidly, stretching and bending chemicalbonds that lack atoms to their neighbors.  If the bonds stretch too far and break then the atoms detach from theirneighbors, more slightly and from new bonds with other atoms.  Repetition of this process leads to the rearrangement of atoms within thegrains, or the migration of atoms into and out of the grains. - Called solid state diffusion o Therefore  Recrystallization and or neocrystallization takesplace, enabling a metamorphic material assemblageto grow in a solid rock.  Takes place at temperatures between though at which diagenesis occursand those that causes melting. - You can find metamorphic rocks in outcrops on continents formedat temperatures between 250* and 850* C - Metamorphism Due to Pressure o Pressure can cause a material to collapse inward  Near the earth’s surface, minerals with relatively open crystal structurescan be stable. - If you subject these minerals to extreme pressure, the atoms packmore closely together and dense minerals tend to form o This transformation involves phase changes and orneocrystallization. - Changing Both Pressure and Temperature o In the earth pressure and temperature change together with increasing depth.  Experiments and calculations how that the stability of certain minerals - The ability of a mineral to form and surviveo Depends on both pressure and temperature. When pressure and temperature increase, the original mineral assemblagein a rock becomes unstable, and a new assemblage forms out of mineralsthat are stable. - For example, a rock formed at 8km does not contain the sameminerals as one formed at 20km.- Compression, Shear, and Development of Preferred Orientation o Compression  Flattens a material o Shear  Moves one part of a material sideways, relative to another. o When rocks are subjected to compression and shear at elevated temperatures andpressures, they can change shape without breaking.  As it changes shape, the internal texture of a rock changes. - Platy (pancake shaped) grains become parallel to one another. - Elongated (cigar-shaped) grains align in the same direction. o Inequant grains, meaning that the dimensions of a grain isnot the same in all directions o Equant grains have roughly the same dimensions in alldirections  The alignment of Inequant minerals in a rock resultsin a preferred orientation. - The Role of Hydrothermal Fluids o Reactions comply take place in the presences of hydrothermal fluids  Very hot water solutions - Where does this fluid come from?o Originally bonded to minerals in the protolith Reactions release water into its surroundings o May seep up into the protolith from a nearby igneousintrusion or down from overlying groundwater reservoirs. o Under extremely high pressure and temperatures. The wateris neither a gas nor a liquid, but a supercritical state  It has the characteristic of both gas and liquids. o Some hydrothermal fluids chemically react with rock


View Full Document

GSU GEOL 1122K - Chapter 7 Textbook Annotations

Download Chapter 7 Textbook Annotations
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Chapter 7 Textbook Annotations and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Chapter 7 Textbook Annotations 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?