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Igneous rock
Rocks are divided into three major groups: igneous, sedimentary, and metamorphic. Igneous rocks form from the cooling and solidification of magma either underground to form intrusive rocks or on the surface to form extrusive rocks. The texture and structure of igneous rocks depends on factors like the cooling rate, mineral composition, and gas content of the magma. Common igneous rock features include phenocrysts, vesicles, xenoliths, columnar joints, and sills/dikes.
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Definition of rocks as aggregates of minerals, with divisions into Igneous, Sedimentary, and Metamorphic rocks.
Classification of Igneous rocks based on chemical composition and characteristics of different magma types.
Textural classification based on crystal size, shape, and arrangement; significance of cooling rates on texture.
Structures like vesicular, xenolith, columnar, and pegmatite in igneous rocks, highlighting gas cavities and mineral grain size.
Types of igneous bodies formed by solidification under surface or on land, including extrusive and intrusive forms.
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Igneous rock
- 1. Dr. V. RGhodakeDr. V. R Ghodake SCOE, PuneSCOE, Pune
- 2. DefinitionDefinition It is aaggregate of mineral. They form major part of the earthIt is a aggregate of mineral. They form major part of the earth crust.crust. Rocks are divided in to three major groupsRocks are divided in to three major groups 1)1)Igneous RocksIgneous Rocks 2)2)Sedimentary RocksSedimentary Rocks 3)3)Metamorphic RocksMetamorphic Rocks Igneous Rocks:Igneous Rocks: Igneous rocks are formed by cooling andIgneous rocks are formed by cooling and solidification of magma. Magma is hot, viscous, siliceoussolidification of magma. Magma is hot, viscous, siliceous melts, containing water vapor and gases. It comes frommelts, containing water vapor and gases. It comes from great depth below the earth surface it is mainly composedgreat depth below the earth surface it is mainly composed of O, Si, Al, Fe, Na, Mg, Ca and K.of O, Si, Al, Fe, Na, Mg, Ca and K. when magma comes upon the surface it iswhen magma comes upon the surface it is called as ‘Lava’called as ‘Lava’ R o c k sR o c k s
- 4. Chemical Composition ofIgneous RocksChemical Composition of Igneous Rocks • Acid MagmaAcid Magma :: is rich in Si, Na, & K and Poor in Ca, Mg, Feis rich in Si, Na, & K and Poor in Ca, Mg, Fe • Basic Magma:Basic Magma: is rich in Ca, Fe & Mg and Poor in Si, Na, & Kis rich in Ca, Fe & Mg and Poor in Si, Na, & K Basic Magma is divided in to three groupsBasic Magma is divided in to three groups 1)1)Ultra Basic rock:Ultra Basic rock: these contains less than 45% of Si. Example Perioditethese contains less than 45% of Si. Example Periodite 2)2)Basic Rock :Basic Rock : These contain Si between 45 to 55 %. Example Gabbro &These contain Si between 45 to 55 %. Example Gabbro & BasaltBasalt 3)3)Intermediate Rock :Intermediate Rock : These contains Si between 55 to 65%. ExampleThese contains Si between 55 to 65%. Example DioriteDiorite 4)4)Acid Rock :Acid Rock : In this Si contains more than 65%. Example GraniteIn this Si contains more than 65%. Example Granite Peridotite Gabbro Basalt Diorite
- 5. Igneous rocks canalso be classified asIgneous rocks can also be classified as 1)1)Over saturated:Over saturated: contains high amount of Si & abundant Qtz. & alkalicontains high amount of Si & abundant Qtz. & alkali FeldsparsFeldspars 2)2)Saturated:Saturated: contains sufficient amount of Si & do not contains Qtz.contains sufficient amount of Si & do not contains Qtz. 3)3)Under saturated:Under saturated: contains less Si & High in Alkali & aluminum Oxides.contains less Si & High in Alkali & aluminum Oxides. Types of Igneous RocksTypes of Igneous Rocks 1)1)Extrusive RocksExtrusive Rocks 2)2)Intrusive Rocks :Intrusive Rocks : These are divided in to two typesThese are divided in to two types Plutonic RocksPlutonic Rocks Hypabyssal RocksHypabyssal Rocks
- 6. Texture of IgneousRocksTexture of Igneous Rocks Texture means Size, Shape and arrangement of mineral grains in a rockTexture means Size, Shape and arrangement of mineral grains in a rock In general the slower cooling or solidification of magma shows coarser grain rocks.In general the slower cooling or solidification of magma shows coarser grain rocks. To study texture following four parts are important.To study texture following four parts are important. 1)1)Degree of crystallizationDegree of crystallization 2)2)Size of grainsSize of grains 3)3)Shape of crystalShape of crystal 4)4)Mutual relation between mineral grainsMutual relation between mineral grains Lava 1)1) Degree of Crystallization : It divides in two partsDegree of Crystallization : It divides in two parts a)a) Holocrystalline texture:Holocrystalline texture: Rocks shows entirely crystalline textureRocks shows entirely crystalline texture b)b) Holohyalline texture:Holohyalline texture: Rocks shows entirely glassy textureRocks shows entirely glassy texture c)c) Meso / Hemicrystalline:Meso / Hemicrystalline: A rock is composed partly of crystals and partly of glassA rock is composed partly of crystals and partly of glass 2) Size of grains:2) Size of grains: a)a) Phaneric : constituent minerals grains can be see by necked eyes.Phaneric : constituent minerals grains can be see by necked eyes. i)i) Coarse grained ii) Medium grained iii) Fine grainedCoarse grained ii) Medium grained iii) Fine grained ii)ii) Aphanitic : whose mineral grains are too small but can be see by necked eyesAphanitic : whose mineral grains are too small but can be see by necked eyes Phaneric TexturePhaneric Texture Aphanitic TextureAphanitic Texture
- 7. Shape of crystals:Shapeof crystals: Well developed crystals faces of grains calledWell developed crystals faces of grains called EuhedralEuhedral Partly developed crystal faces calledPartly developed crystal faces called SubhedralSubhedral The crystal faces are absent such grains of rock calledThe crystal faces are absent such grains of rock called UnhedralUnhedral Mutual relation of grainsMutual relation of grains.. i)i) Equigranular textureEquigranular texture ii)ii) Inequigranular textureInequigranular texture a) Porphyritic texture b) Poikilitic texture c) Ophitic texturea) Porphyritic texture b) Poikilitic texture c) Ophitic texture Porphyritic texturePorphyritic texture Poikilitic texturePoikilitic texture PhenocrystPhenocryst GroundGround massmass
- 8. VesicularTexture: Volcanic rocks whichhave a glassy matrix often contains gas cavities called vesicles.
- 9. Structures of IgneousRocksStructures of Igneous Rocks VesiclesVesicles Vesicular StructureVesicular Structure
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- 11. Structures of IgneousRocksStructures of Igneous Rocks
- 12. Structures of IgneousRocksStructures of Igneous Rocks
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- 14. Pegmatite Structure:Pegmatite Structure:The constituent minerals grains exceedsThe constituent minerals grains exceeds several centimeters in the size, the rock is known asseveral centimeters in the size, the rock is known as Pegmatite Structure.Pegmatite Structure. Structures of Igneous RocksStructures of Igneous Rocks Pegmatite StructurePegmatite Structure
- 15. 1)1) Extrusive IgneousBodiesExtrusive Igneous Bodies 2)2) Intrusive Igneous Bodies.Intrusive Igneous Bodies. Forms of Igneous BodiesForms of Igneous Bodies Extrusive Igneous Bodies :Extrusive Igneous Bodies : These are forms when magmaThese are forms when magma reaches to earth surface and get solidification. Example Lavareaches to earth surface and get solidification. Example Lava flowflow Intrusive Igneous Bodies :Intrusive Igneous Bodies : These areThese are formed by the consolidation of magma atformed by the consolidation of magma at some depth below the earth surface. Suchsome depth below the earth surface. Such bodies shows variations in their shape andbodies shows variations in their shape and size.size. These are divided in to two parts.These are divided in to two parts. 1) Discordant bodies 2) Concordant bodies.1) Discordant bodies 2) Concordant bodies.
- 17. Forms of IgneousBodiesForms of Igneous Bodies SillSill SillSill DykeDyke Volcanic neckVolcanic neck LaccolithLaccolith
- 18. Forms of IgneousBodiesForms of Igneous Bodies Mafic dykeMafic dyke
- 19. Forms of IgneousBodiesForms of Igneous Bodies BatholithsBatholiths
- 22. SillsSills are alsosmall igneous intrusions. They are sheets of rock that, unlike dikes, are parallel to pre-existing rocks. Think of magma invading sedimentary rocks by spreading out between rock layers. That magma would cool to form a sill.