Rocks_geology_engineering_gati_shakti.pptx

the presentation is based on the topic rock in geology.

1. Rock Rock or stone is a natural substance, a solid aggregate of one or more minerals combined together in an orderly manner. Petrography deals with the descriptive part of rocks. Petrogeny deals with the mode of formation of rocks. 1

2. Petrology means “ STUDY OF ROCKS” Petro = Rock L o g y = S t u d y The branch of geology deals with the various aspects of rocks such as, Origin, Association, Occurrence, Mineral composition , Chemical composition, Texture, Structure, Physical properties of rocks. 2

3. Classification of Rocks R oc k s Geological I g neo u s Intrusive H yp a ba sa l Pl u t onic Extrusive V olc anic Sedimentary Clastic Deposits C hemical Deposits Organic Deposits Met am o r p hic F olia t ed Non F olia t ed Physical Stratified Unst r a t if i ed F o l ia t ed Chemical Siliceous Argillaceous Calcareous 4

4. Igneous Rock Ig n eous r oc k s a r e th e p r i m a ry r ocks , w hich a r e f o rmed due to cooling and solidification of magma. Magma is a hot viscous, siliceous melt, containing water vapour and gases . Ma g m a co m es o u t f r o m t h e g r ea t e r depth bel o w t h e e ar t h surface, such magma is called LAVA. 4

5. Classification of Igneous Rock R oc k s Geological I g neo u s Intrusive H yp a ba sa l Pl u t onic Extrusive V olc anic

6. I g neous Rock Intrusive igneous rocks Intrusive igneous rocks are formed from magma that cools and solidifies within the crust of a planet, surrounded by pre-existing rock (called country rock). The magma cools slowly and, as a result, these rocks are coarse-grained . The mineral grains in such rocks can generally be identified with the naked eye.

7. Dior i t e G r an i t e

8. G a bb r o Pegmatite

9. Classification of Igneous Rock R oc k s Geological I g neo u s Intrusive H yp a ba sa l Pl u t onic Extrusive V olc anic

10. Igneous Rock Intrusive igneous rocks Hypabasel Rock These Rocks are formed at intermediate depth generally up t o 2 km b e l o w th e ea r t h s u r f a c e and e x h i b i t s m i x e d characteristics of volcanic and plutonic.

11. Dior i t e

12. Igneous Rock Intrusive igneous rocks Plutonic Rock These R o c k s a r e f o rm e d at c o n s i de r abl e depth ge n e r a l l y u p to 7-10 km below the earth surface. Because of very slow rate of cooling at these depth coarse grained rocks are formed.

13. G a bb r o Pegmatite

14. Plutonic Rocks Gabbro Hypab a sel R o c k Diorite

15. Igneous Rock Extrusive igneous rocks It is also called as volcanic rocks. These rocks are formed due to cooling and solidification of magma at the crust surface. The magma, which is brought to the surface through fissures or volcanic eruptions, solidifies at a faster rate . Hence such rocks are smooth, crystalline and fine-grained .

16. Igneous Rock Extrusive igneous rocks V o l cani c R o c k s These rocks are formed due to cooling and solidification of lava erupted from volcanoes. since lava cools down very fast rate. The grain size of the crystal formed in these rock is fine .

17. V ol c an i c R o c k

18. B a s a l t

19. B a s a l t Diorite

20. Classification of Rocks R oc k s Geological Sedimentary Clastic Deposits C hemical Deposits Organic Deposits

21. Sedimentary Rock E ng - Ge o [6K473]-U n it 1 Sedimentary rocks are those, which are formed by the accumulation, compaction and consolidation of sediments. The sediments are the particles produced from the disintegration of pre-existing rocks (Igneous/metamorphic rocks) through the process of transportation and deposition by various natural agencies like wind, water and glaciers . 21

22. Sedimentary Rock Eng- Geo [6K473]-Unit1 24

23. Sedimentary Rock

24. Sand Stone C o n g l o m e r a t e

25. shale Lim e s t o n e

26. Sedimentary Rock Clastic deposit rock They are mechanically formed rocks. These are formed due to the process of weathering, erosion, transportation and deposition of pre-existing rocks. Rudaceous rocks -If the grain size are more than 2 mm in dia, Arenaceous rocks- If the grain size is in between 1 and 2 mm. Argillaceous rocks- If the size of the particle is < 1mm in dia,

27. C o n g l o m e r a t e B r e c cia

28. Quartz Sand stone G r i t

29. Shale and Mud stone

30. Sedimentary Rock Chemical deposit rock They are formed by precipitation, evaporation or crystallization from natural aqueous solution. When water is rich in dissolved salt evaporates and left behind minerals. (Halite) Limestone can form when calcite minerals dissolved in lakes, sea and underground water comes out of solution and form crystal.

31. Lime Stone Hali t e

32. Sedimentary Rock Organic deposit rock Sedimentary rocks which are formed exclusively from remains of organisms like plant / animals deposited in a thick layer.

33. Eng- Geo [6K473]-Unit1 35

34. C o al Li g n i t e

35. Classification of Rocks R oc k s Geological Met am o r p hic F olia t ed Non F olia t ed Physical Chemical

36. Metamorphic Rock The word "Metamorphism" comes from the Greek: Meta = change , Morph = form , so metamorphism means to change form. Metamorphic rocks are those rocks that are formed as a result of transformation that takes place in the pre-existing rocks (Igneous/sedimentary rocks). When the pre-existing rocks are subjected to higher temperature, pressure and chemically active liquids and gases, the minerals present in the original rocks changes to new environmental condition.

37. S l a t e S l a t e

38. G neiss Gneiss

39. Metamorphic Rock Foliated W h e n p r e s s u r e sq u eez e s th e flat o r e lo n g a t e m ine r a l s w i t h i n a rock so they become aligned. These rocks develop a platy or she e t - l i k e s t ruct u r e t h a t r e f l e c t s t h e d i r ect io n t h a t p r e s s u r e was applied in. Slate , schist , and gneiss are all foliated metamorphic rocks.

40. S l a t e S chist

41. Metamorphic Rock Non Foliated Non foliated metamorphic rocks are formed around igneous i n t r us i o ns w h e r e t h e t empe r at u r e s a r e h i g h bu t the pressures are relatively low and equal in all directions

42. Wh i t e M a r bl e M a r bl e

43. Classification of Rocks R oc k s Geological I g neo u s Intrusive H yp a ba sa l Pl u t onic Extrusive V olc anic Sedimentary Cla stic C hemical Deposits Organic Deposits Met am o r p hic F olia t ed Non F olia t ed Physical Stratified Unstratified Foliated Chemical Siliceous Argillaceous Calcareous

44. Physical Classification Stratified rocks These structure . rocks are h a vi n g l a y e r ed They possess planes of stratification or c l e a v ag e . They can be easily split along these planes. Exa: Sand stones, lime stones , etc .

45. Physical Classification Un-stratified rocks These rocks are not stratified. They possess crystalline and compact grains. They cannot be split in to thin slab. Exa: Granite, trap, marble

46. G r an i t e Marble

47. Physical Classification Foliated Rocks These r ock s h av e a t e n d e nc y t o split a l o n g a d e f i n i t e direction only. The direction need not be parallel to each other as in case of stratified rocks. This ty p e o f s tr u c t u r e i s v e r y co m m o n i n case of metamorphic rocks.

48. Chemical Classification Siliceous rocks These rocks which have silica as the main constituent. The silica in the free state is called sand and in combined state is silicate. Examples: Granite, Quartzite, Sandstone etc.

49. Chemical Classification Argillaceous rocks These rocks which have clay or alumina as the main constituent. Examples: Kaolin, Laterite, Slate etc.

50. Chemical Classification Calcareous rocks These r oc k s w hich h av e calcium carbonate or lime as their leading constituent. These rocks are readily acted upon by even dilute HCl . Examples: Limestone and Marble.

51. F o r m s o f I g ne o u s R o c k I gn eo u s R oc k s Intrusive Concordant Sill P hac o li t h Lopolith L acc o li t h Discordant Batholith D y k e Volcanic neck Extrusive

52. Forms of Igneous Rock Concordant intrusive bodies T h e ma g m a i ntr u sion i s p a r allel t o t h e st r u ct u r e o f t h e c o u ntry rock, they are called ‘Concordant intrusive bodies

53. Forms of Igneous Rock Concordant intrusive bodies Sill It is a concordant intrusive igneous bodies. Sills are formed due to the penetration of magma into bedding planes of enclosing sedimentary rock. Their spreading capacity is mainly depends upon viscosity of magma, its temperature and the weight of overlaying rocks. The thickness varies from few centimetres to several kilometres

54. E n g- Geo [ 6 K 473 ]- Un i t 1 59 Sill

55. F o r m s o f Igneou s R o c k C on c o r d a n t intrusive bodies Phacolith When thick sedimentary strata are folded, along the crust and trough, some empty space occurs. These spaces are readily occupied if magmatic intrusion get access to them. On solidification these appear as lens shaped across the axial plane. 60

56. Eng- Geo [6K473]-Unit1 61 Phacolith

57. Forms of Igneous Rock Concordant intrusive bodies Lopolith This i s b a s i n o r saucer shap e d concordant intrusive igneous body of enormous size. Its top is nearly flat and bottom is convex downward bowl-like bodies, which are sagged downwards due to the weight of the intruded magma. 62

58. Eng- Geo [6K473]-Unit1 63 Lopolith

59. Forms of Igneous Rock Concordant intrusive bodies Laccolith This is a mushroom like concordant intrusive igneous bodies. It is nearly flat bottom but it is convex upward i.e. dome shaped. When viscous magma is injected along the bedding plane, as it cannot spread easily, it pushes up the overlaying rocks and piles up more at the place. 64

60. Forms of Igneous Rock Concordant intrusive bodies Laccolith Eng- Geo [6K473]-Unit1 65

61. Laccolith Eng- Geo [6K473]-Unit1 66

62. Forms of Igneous Rock intrusive ign e ous Discordant intrusive bodies Batholith Thes e a r e the l a r g e s t k n o w n di s c o r da n t bodies mainly occurring in mountain ranges. Batholiths have side sloping away from each other which makes them larger and larger downwards and they have extended to very great depths covering several kilometres. 67

63. Batholith Eng- Geo [6K473]-Unit1 68

64. Forms of Igneous Rock Discordant intrusive bodies Dyke Dykes are discordant igneous body of more or less tabular shape and exhibit a cross –cutting relationship with the country rocks they occur commonly n the forms of wall like masses of exactly or nearly vertical attitude. If the rocks constituting the dyke are hard and compact, they can resist weathering and Erosional process. 69

65. D y k e Eng- Geo [6K473]-Unit1 70

66. D y k e Eng- Geo [6K473]-Unit1 71

67. Forms of Igneous Rock Discordant intrusive bodies Volcanic neck The vents of quiet volcanoes have become sealed with the igneous intrusions and is called volcanic necks/plugs. These forms may be circular, semi circular or irregular and in varying diameter. 72

68. V o l c a n i c neck Eng- Geo [6K473]-Unit1 73

69. Structure 72 Structure are physical features associated with the rocks. They are primary in nature they occurs along with the formation of rocks Structure contribute the strength and weakness of the rock. Structure helps to distinguishing features of rock group. Structure reveals the mode of formation.

70. Structure of Igneous Rock 73 Vesicular Structure Structure is porous in nature. Commonly observed in Volcanic rocks. Magma is a mixture of rock melts and volatiles, (Gases). The g a s es p r e s en t i n t h e m a gm a a r e l i g h t e r and escape in t o atmosphere. Em p t y c a v i t y o f v a r i o u s siz e s and shapes a r e f o r m e d on surface. These cavity called Vesicles. W h e n v o l c ani c r oc k i s h i g h l y p o r o u s a n d s po n g y in appearance, it is called Scoria

71. Structure of Igneous Rock Vesicular Structure 74

72. Structure of Igneous Rock Amygdaloidal Structure The empty vesicles in the vesicular structure are filled by surface water or under ground water or sediments. The in filled cavity are called Amygdales. Wh en e mp ty c a v i ti e s a r e fi l l e d wi t h a m y gda le s th a t structure is called Amygdaloidal Structure 75

73. Structure of Igneous Rock Amygdaloidal Structure 76

74. Structure of Igneous Rock Columnar Structure The volcanic igneous rock appears to be made up of numerous parallel polygon prismatic column bundled together. This results of the contraction of lava during cooling. 77

75. Structure of Igneous Rock Columnar Structure 78

76. Structure of Igneous Rock Sheet Structure The rocks appears to be made up of a number of sheets, because of the development of nearly horizontal crack . Plutonic rocks are formed at a great depth which means under the great pressures. W he n e r os i o n t a k e s plac e i n t h e o v e r l a y i n g s t r a ta gradually dis appear ultimately exposing of plutonic rock in the form sheet. 79

77. Structure of Igneous Rock Sheet Structure 80

78. Structure of Igneous Rock Flow Structure These struct u r e s a r e li ne a r a nd n e a r l y p a r all el f e at u r es oc c urri n g i n v ol c an i c r oc k s w hich d e v elops as a consequence of the flow of lava. 81

79. Structure of Igneous Rock Flow Structure 82

80. Structure of Igneous Rock P i ll o w S t r u ctu r e The Volcanic igneous body appears as a pile of numerous overlapping pillows. It occurs only in soda rich basalt rock. The pill o w s a r e g e ne r a l l y i n t e r conn e c t e d v e s i c u l ar a n d glassy tops. 83

81. Structure of Igneous Rock Pillow Structure 84

82. Structures of Metamorphic rocks Cataclastic structure S chistose structure G neissose structure M aculose structure G ranulose structure

83. Cataclastic structure Cataclastic structure results from the crushing and granulation of minerals and rocks ( cataclasis ), through the application of stress at low temperatures, with but little new mineral formation, except along planes of considerable movement, and at places where heat has been locally generated in the upper zones of earth’s crust. Due to this, resistant minerals in rocks may remain unaffected, while the softer minerals are powdered to fine material.

84. S chistose structure Schistosity ,  mode of foliation that occurs in certain metamorphic rocks as a consequence of the parallel alignment of platy and lath-shaped mineral constituents . It reflects a considerable intensity of metamorphism—i.e., changes resulting from high temperatures, pressures, and deformation

85. G neissose structure Gneissose structure This is a banded structure in which the minerals have been segregated into discontinuous bands, each of which is dominated by one or two minerals. These bands range in thickness from 1 mm to several centimeters. The individual mineral grains are macroscopic and impart a striped appearance to a hand specimen. Light-colored bands commonly contain quartz and feldspar. and the dark hands are commonly composed of hornblende and biotite . Accessory minerals are common and are useful in applying specific names to these rocks. A rock with a gneissic structure is called a gneiss.

86. G neissose structure

87. M aculose structure Maculose structure is characterized by a spotted appearance of the rock that may be caused due to the formation of large-sized crystals called porphyroblasts within an otherwise fine grained rock as a result of thermal metamorphism of argillaceous rocks like shale.

88. G ranulose structure Granulose : —a texture (structure) characterized by the presence of granular minerals such as quartz, feldspar, garnet, and pyroxene in granulites; alternating streaks or bands may vary in mineralogy, but consist of granular minerals.

89. Structures of Sedimentary Rock Stratification Lamination Cross bedding Ripple marks Rain Prints Mud Cracks Graded bedding

90. Stratification

91. Lamination

92. Cross bedding

93. Ripple marks

94. Rain Prints

95. Mud Cracks

96. Graded bedding