METAMORPHIC ROCKS

Sire Kassama 2014

Intro to Info

Metamorphic Rocks: Rocks created through intense heat or pressure

Are good examples of metamorphic rock: gneiss, schist, slate, marble

Alps and Himalayas are primarily composed of metamorphic rocks

Foliated metamorphic rocks are rocks that have bands of minerals in it

Metamorphism

Describe the only location that provides the intense and extreme heat and pressure re-quired to form metamorphic rocks.

Deep within the earth; lithosphere; or subduction zone

Contact vs. Regional Metamorphism

Local or Contact Metamorphism: rocks touched by red hot magma in crust; whenever magma rises to crust

Regional Metamorphism: deep in crust from enormous pressure over a large area; two tectonic plates move toward each other; Lewissian gneiss is a good example

VS. CONTACT REGIONAL

occurs adjacent to igneous intrusions

Both• Contact may result from tectonic forces

resulting in compressional stresses • usually results in foliated metamorphic rocks• mineral crystals are rearranged• results in folds or curves• large crystals are formed• minerals crystallize

Identifying Metamorphic Rocks

Rock Color Foliated Grain Size

Shale Dark gray Yes Fine

Schist Mixture No Medium

Gneiss Pink or gray Yes Coarse

Marble Light No Coarse

Quartzite Light No Coarse

Need To Know on Rocks ROCK NAME TYPE ( Igneous, Sedimentary, metamorphic) FORMATION Igneous (Extrusive, Intrusive) (volcanic, plutonic) (felsic or mafic) Sedimentary ( Clastic, chemical, biochemical, organic) Metamorphic (Regional, Contact Metamorphism) (low grade-high grade) ENVIRONMENT TEXTURE Igneous (phaneritic, aphanitic, porphyritic) Sedimentary (grain size) Metamorphic Foliated or non-foliated HARDNESS RANGE MINERALS PHYSICAL DESCRIPTION (Color) USES OTHER PROPERTIES

Base your answers to this question on the pictures of four rocks shown below. Magnified views of the rocks are shown in the circles. What do all four rock samples have in common?

1.They show cleavage. 2. They contain minerals. 3. They are organically formed. 4. They formed on Earth’s surface.

Base your answers to this question on the pictures of four rocks shown below. Magnified views of the rocks are shown in the circles. Which rock is metamorphic and shows evidence of foliation?

Which sample best shows the physical properties normally associated with regional metamorphism?

Examples of Metamorphic Rocks

Marble

Reacts with HCl and therefore contains the mineral calcite

Formed by metamorphism of limestone Minerals: Calcite Has no foliation Red, white, yellow, green Found in US, Italy, Canada, Spain, Greece Used in sculptures, Lincoln memorial

Slate

Fine grained rock formed when shale, mudstone, clay, or volcanic ash is put under high pressure

Splits into thin sheets easily Almost completely waterproof Used for roof and floor tile, monuments,

and name plates Minerals: mica, feldspar, and quartz

Schist

Medium grained Made from shale, clay, slate, and many

other rocks Put under very high temperatures and

pressures Minerals: feldspar, mica, quartz Good for building materials Also crushed into gravel to use for

pavements

Gneiss

Formed at very high temperatures and pressure from different igneous and sedimentary rocks

Coarse grained and has bands of minerals that are often bent and folded

Formerly granite before exposed to immense pressure

Used to replace granite Common metamorphic rock Found in Sweden

Quartzite

Formed when sandstone is heated Formed when tectonic plates grind

together Some of the oldestest rocks made of

quartzite

Other Resources

The following questions and answers are from the New York State Regents Website: http://www.regentsprep.org/Regents/core/questions/topics.cfm?Course=ESCI

Geology.com

Contact metamorphism: alteration of rock by heat adjacent to hot lava; important setting fir metallic ores such as gold, silver, copper, zinc, lead, etc

Regional metamorphism: alteration of rock over large area by het and pressure due to deep burial or tectonic process

Metamorphic Rocks are either foliated or nonfoliated

Foliated: laminated structure in rock resulting from parallel alignment of sheet like minerals ( slate, phyllite, schist, gneiss)

Nonfoliated: no preferred orientation (marble , quartzite)