GEOL 11: PRINCIPLES OF GEOLOGY 2nd Year
1st Sem
LESSON 9: Metamorphism, Metamorphic Rocks and Resources S.Y 2023 - 2024
MEtamorphism
-process of change undergone by an existing rock Water from
(protolith) in solid-state to another rock magmatic bodies
(hydrothermal)
[bago mag-metamorphism]
Lower limit: diagenesis (a sedimentary process)
Upper limit: melting (an igneous process) **fluids transport mineral matter from one
mineral to the other: metasomatism (e.g.
gold deposits)
Agents of metamorphism
● Heat
● Pressure
● Chemically-active fluids Types of metamorphism
** they may or may not interact with each other in (based on dominant agents)
a single environment**
Contact Metamorphism
Heat -T is dominant;
-provides the energy to drive chemical reactions -country rocks in contact with intrusives
-source of heat -magma invading pre-existing rock creates a zone
● Geothermal gradient of alteration (aureole) around the intruding body
● Intrusive bodies ● takes place at shallow depths and low
● Radioactive decay pressure
● creates non-foliated rocks
Pressure ● Bake-and-chill
-confining pressure -bake-and-chill margins
● equal stress in all directions ● textural contrast between an intrusion
● commonly after burial and the country rock caused by contact
-differential stress metamorphism
● unequal pressure in different directions
Chemically-active Fluids
fluids in pore spaces of original
rock/sediments
Dynamic Metamorphism
-rocks are subjected to shear forces along a fault
zone
fluids from dehydration ● brittle: fault breccia
of hydrated minerals ● ductile: mylonite
(micas, amphiboles)
1st Sem
LESSON 9: Metamorphism, Metamorphic Rocks and Resources S.Y 2023 - 2024
MEtamorphism
-process of change undergone by an existing rock Water from
(protolith) in solid-state to another rock magmatic bodies
(hydrothermal)
[bago mag-metamorphism]
Lower limit: diagenesis (a sedimentary process)
Upper limit: melting (an igneous process) **fluids transport mineral matter from one
mineral to the other: metasomatism (e.g.
gold deposits)
Agents of metamorphism
● Heat
● Pressure
● Chemically-active fluids Types of metamorphism
** they may or may not interact with each other in (based on dominant agents)
a single environment**
Contact Metamorphism
Heat -T is dominant;
-provides the energy to drive chemical reactions -country rocks in contact with intrusives
-source of heat -magma invading pre-existing rock creates a zone
● Geothermal gradient of alteration (aureole) around the intruding body
● Intrusive bodies ● takes place at shallow depths and low
● Radioactive decay pressure
● creates non-foliated rocks
Pressure ● Bake-and-chill
-confining pressure -bake-and-chill margins
● equal stress in all directions ● textural contrast between an intrusion
● commonly after burial and the country rock caused by contact
-differential stress metamorphism
● unequal pressure in different directions
Chemically-active Fluids
fluids in pore spaces of original
rock/sediments
Dynamic Metamorphism
-rocks are subjected to shear forces along a fault
zone
fluids from dehydration ● brittle: fault breccia
of hydrated minerals ● ductile: mylonite
(micas, amphiboles)
