Transcript UNIT-III PETROLOGY

UNIT-III
PETROLOGY
This lecture will help you to
understand……
• Features of rock – formation, abundance and variety
in the earths crust.
• Mode of formation.
• Important rock groups and its classification.
• Importance of petrology for civil engineering.
Structure of the Earth
• Crust (0-35 km)
• Mantle (35-2898 km)
• Core (2898-6370)
ROCKS
IGNEOUS
1.Plutonic
2.Hypabyssal
3.Volcanic
SEDIMENTARY
METAMORPHIC
1.Fragmental
2.Chemical
3.Organic
1.Thermal
2.Dynamothermal
1. IGNEOUS ROCKS
• Formed by the consolidation of magma
• Mode of formation intruded or extruded
– Extruded- external rock formation during lava flow
– Intruded-internal rock formation inside older rocks
• Extruded-Extrusive rocks
• Intruded-Intrusive rocks
• Examples for intrusive rocks- Plutonic and hypabyssal rocks
• Igneous rocks classification
– 1.Acidic-rich in alumina
– 2.Basic-Rich in iron oxide and magnesia
2. SEDIMENTARY ROCKS
• Made of fragments and particles derived from older rocks.
• Usually cross bedded or false bedded structure.
• Fossiliferous
• Texture mainly depends on conditions under which the sediments
deposited.
– Coarse grain sedimentary rocks-shallow water deposition
– Coarse grain chemically formed rock-crystallisation of material dissolved in
water
• Major classification
– 1.fragmental or sedimentary deposits
– 2.chemical deposits
– 3.organic deposits
3. METAMORPHIC ROCKS
• Rocks which undergone some physical or chemical change give birth to
metamorphic rock
• metamorphic – “change in form”
• Rock resembles the parent rock with some altered characters due to the
reaction of external agents
• Agents responsible for metamorphism
– Addition of heat
– Operation of pressure due to chemical agents
– Temperature
• Process involved in metamorphism
– Thermal metamorphism – Effect on heat with depth
– Dynamo thermal metamorphism – combination of pressure and heat