2. After undergoing this learning material, you are expected to:
1. describe the changes in mineral components and texture of rocks due
to changes in pressure and temperature (metamorphism) (S11/12ES-
Ic-17); and
2. compare and contrast the formation of the different types of igneous
rocks (S11/12ES-Ic-18)
Learning Objectives:
1. identify the factors affecting metamorphism
2. classify metamorphic rocks in terms of metamorphic grade and foliation
3. make use of a graphic organizer that will compare and contrast the
formation of the different types of igneous rocks
4. analyze igneous rocks in connection with composition and texture
3. Activity 1: Concept Map
Directions: Understand and identify the processes of the Rock
Cycle. Choose your answers from the box.
1. ____________________________________
2. ____________________________________
3. ____________________________________
4. ____________________________________
5. ____________________________________
6. ____________________________________
7. ____________________________________
8. ____________________________________
9. ____________________________________
Melting
Weathering
Lithification
Heat and Pressure
Cooling
Melting
Heat and Pressure
Weathering
Weathering
4. Factors that Affect Metamorphism:
1. TEMPERATURE
During the burial of rocks (collision or subduction), as it goes deeper the temperature
increases. Thus, higher temperature is expected during this process.
2. PRESSURE
There are two types of stress due to the increase of pressure, uniform stress, and differential stress.
Uniform stress is also called hydrostatic stress or confining stress because the pressure is equal from all
directions while in differential stress the pressure from all directions are not equal.
3. FLUID PHASE
Spaces between mineral grains in rocks may contain dissolved ions of H2O that speeds up
chemical change of a solid mineral into a new solid mineral. This alteration process is known as
metasomatism.
4. TIME
Metamorphism is a slow process and grains (mineral size and shape) increases with time. Coarse
grain metamorphic rocks took longer time of metamorphism.
5. Types of Igneous Rock Formation
Igneous rocks can be classified into types according to its formation.
1. Extrusive igneous rocks also known as Volcanic igneous rocks solidify at the surface.
2. Intrusive igneous rocks otherwise called Plutonic igneous rocks crystalizes at depth.
Igneous rocks are characterized in terms of texture (size, shape, and arrangement) and
composition (chemical makeup). The size of grain is relative to the rate of cooling. Thus, slow
rate of cooling will produce large crystals intrusively while rapid rate of cooling will result
small crystals extrusively.
6. Metamorphic Grade
Metamorphic Grade is the relative temperature and pressure conditions necessary for
the formation of metamorphic rocks.
1. Low-grade metamorphism – abundant in hydrous minerals at temperatures ranging from
200 to 320 ºC and a relatively low pressure. Examples are Clay Minerals, Serpentine, and
Chlorite.
2. High-grade metamorphism – non-hydrous minerals at temperatures exceeding from 320
ºC and a relatively high pressure. Examples are Biotite, Pyroxene, and Garnet.
There are two types of metamorphic rocks: foliated and non-foliated. Examples of
foliated metamorphic rock are Slate, Schist, and Gneiss while Amphibolite, Quartzite and
Marble are examples of non-foliated metamorphic rock because there is no evident planar
formation.
Editor's Notes
Metamorphic rocks came from an original rock known as protolith.
Protoliths are any type of rock that undergoes physical and chemical changes in texture and mineralogy and this process is called metamorphism.
These physical and chemical changes are driven by burial, tectonic stress, magmatism, and interactions with fluids.
All of these activities are possible due to the following conditions:
