New version page

ECU GEOL 1500 - Metamorphic Rocks Notes - Fall 2014

This preview shows page 1-2-3-4-5 out of 16 pages.

View Full Document
View Full Document

End of preview. Want to read all 16 pages?

Upload your study docs or become a GradeBuddy member to access this document.

View Full Document
Unformatted text preview:

Ranges from Low to Intermediate/Medium to High Grade Pressure and Temperature Conditions (Greenschist to Amphibolite to Granulite Grade in P-T Diagram)A. Textural ChangesMETAMORPHISM AND METAMORPHIC ROCKSMetamorphism = Textural, mineralogical, and/or chemical changes that take place in the solid state (no melting) in response to changing Pressures and Temperatures and/or introduction of Chemically-active Fluids.Most Metamorphism is associated with Igneous Activity (Plutonism), Deformation, and Mountain Building (Orogeny). Hence, an Orogeny is a Period of Igneous Activity, Deformation, Regional Uplift, and Mountain Building. All of these processes are driven by the Earth’s internal heat derived primarily from Radioactivity.Metamorphic Rocks are exposed along with Igneous Rocks by Uplift and Erosion (Rock Cycle)The Rock Cycle (Generic)The Rock Cycle at a Convergent BoundaryI. Conditions that Cause and Drive MetamorphismA. Temperature - derived from Radioactivity, magmatic heat, and friction from faulting. Lower Temperature Limits are 200oC (10 Km depth)Upper Temperature Limits are about 700oC (30 Km depth)B. Pressure - measured in Kilobars (1 Kbar = 1000 bars; 1 bar = 14.7 lbs/in2)Lower Pressure Limits are 1-2 Kbar or 3-6 Km depth (1 Kbar ~ 3 Km depth)Upper Pressure Limit is ~ 10 Kbar or 30 Km depth)1. Confining Pressure or Lithostatic Pressure increases with increasing depth of Burial 2. Directed Pressure/Differential Stress at Convergent Boundaries and along faults (causes Deformation) C. Chemically-active Fluids (Hydrothermal Solutions) and Gases - derived from magma and from water-rich minerals (clays, micas, and amphiboles)II. Types of Metamorphism and Plate BoundariesIII. Types of MetamorphismA. Contact Metamorphism 1. Characteristics/Definition - Localized type of metamorphism that occurs Immediately adjacent to igneous intrusions, usually at shallow depths, and is driven primarily by excess heat derived from cooling magmas. Forms fine- to coarse-grained granular rocks. Dramatic Mineralogical changes but little textural change.22. Types of Changes that Occur during MetamorphismA. Mineralogical Changes (Driven primarily by increases in Temperature)1. Low temperature minerals change to higher temperature minerals2. Recrystallization3. Environment - High T - Low P at Shallow Depths adjacent to Igneous Intrusions (Hornfels = Contact Metamorphism in Graph)4. Plate Tectonics Association - Convergent and Divergent Boundaries5. Rocks formed under Contact Metamorphism P-T Conditionsa. Hornfels - from Contact Metamorphism of Shale or Mudstone3Hornfelsb. Marble - from Contact Metamorphism of Limestone or Dolostone Marblec. Quartzite - from Contact Metamorphism of Quartz SandstoneQuartziteB. Regional Metamorphism Ranges from Low to Intermediate/Medium to High Grade Pressure and Temperature Conditions (Greenschist to Amphibolite to Granulite Grade in P-T Diagram)4Occurs over large areas or regions due to elevated temperatures from the Intrusion of Batholiths and Directed Pressures from mountain building at active convergent boundaries and elevated Confining Pressures from deep burial. There are both Textural and Mineralogical changes. Most obvious of textural changes is development of Foliation in Rocks of variable composition and colour and results from increasing levels of Pressure.2. Types of Changes that Occur during MetamorphismA. Textural Changes1. Development of Foliation (= Parallel alignment of flat, platy minerals in response to directed pressure) 2. Change in Grain Size Development of Foliation in Regional Metamorphic RocksAnimation: <http://www.classzone.com/books/earth_science/terc/content/visualizations/es0607/es0607page01.cfm> B. Mineralogical Changes1. Low temperature minerals change to higher temperature minerals2. Recrystallization3. Environment - Broad regions and depths associated with the intrusion of large Batholiths and a range of Pressures and Temperatures thatvary with depth of burial and proximity to the Batholith as asource of heat. Conditions vary from Low P-T to High P-T(Low Grade [Greenschist] to Intermediate or Medium Grade [Amphibolite] to High Grade [Granulite]). See P-T Diagram above.4. Plate Tectonic Association - Convergent Boundaries only 5Ignore terms, “Barrovian” and “Eclogite”5. Rocks formed in response to Regional Metamorphism - Wide range of rocks Which are classified based on Texture (presence of an obvious Foliation or lack of a foliation) and Grade or Range of P-T (based on Mineralogy).6a. Foliated Regional Metamorphic Rocksi. Slate - Low Grade P-T (Greenschist Grade) from Shale or Mudstone Slate Slateii. Phyllite - Low Grade P-T (Greenschist Grade) from a Shale 7or MudstonePhylliteiii. Schist – Intermediate or Medium Grade P-T (Amphibolite Grade) from a Shale or Mudstone Garnet Schist Mica Schistby Andrew Alden, geology.about.comiv. Gneiss - High Grade P-T (Granulite Grade) from a Shale, Mudstone, or Felsic Igneous RockBanded GneissLineated Gneiss8b. Nonfoliated to Weakly Foliated Regional Metamorphic RocksNote that Marble and Quartzite are Nonfoliated Metamorphic Rocks that can form under Intermediate-Medium Grade (Amphibolite Grade) to HighGrade (Granulite Grade) Regional Metamorphism conditions as well as under Contact Metamorphism conditions. See the section above on Contact Metamorphism for parent rock information on and images of Marble and Quartzite.i. Greenstone - Low Grade (Greenschist Grade) P-T from a Mafic Igneous Rock (Basalt/Gabbro)Greenstoneii. Amphibolite – Intermediate or Medium Grade (Amphibolite Grade) P-T from a Mafic Igneous Rock (Basalt/Gabbro)Amphiboliteiii. Granulite - High Grade (Granulite Grade) P-T from Arkosic or 9Lithic Sandstones or Igneous Rocks of variable compositionGranulite“Dr. Harper’s Metamorphic Rock Index Photos and Description” <http://core.ecu.edu/geology/harper/Metamorphic/Metamorphic_new.cfm>C. Blueschist 1. Definition - A High P-Low T metamorphism that occurs at Subduction Zones as Basalt and Ocean floor sediments are shoved downward. Pressure increases at greater rate than temperature. Changes mineralogy and texture. Actually a sub-type of Regional Metamorphism. See P-T Diagram Below.2. Types of Changes that Occur during MetamorphismA. Textural Changes1. Development of Foliation (= Parallel alignment of flat, platy minerals In response top directed pressure) B. Mineralogical Changes1. Low


View Full Document
Loading Unlocking...
Login

Join to view Metamorphic Rocks Notes - Fall 2014 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 Metamorphic Rocks Notes - Fall 2014 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?