2. Introduction
What is Sandstone?
• Sandstone is one of the most common kinds of clastic
sedimentary rocks consists of sand-size (0.06 to 2 mm) clasts
or grains of minerals and organic matters.
Formation of Sandstone
• The formation of sandstone occurs mostly into two phases,
sedimentation/accumulation & compaction. Sedimentation of
sand particles takes place either through water or air.
Compaction occurs with physical pressure and chemical
changes. The steps are:
• Sedimentation of quartz crystals
• Formation of cement & matrix
• Formation of pores
3. Types of Sandstone Components
• The first phase forms sand clasts or grains due to
transportation of sand particles from the source. The second
phase forms cement or binding material and matrix as filler
between the framework grains or clasts. The pore space is a
void where no clasts, cement, or matrix matter exists. Let’s
know these components of sandstone with some details.
6. What is limestone?
• Limestone = a biochemical sedimentary rock
made up mostly of calcium carbonate
Mineral Crystal system Formula Remarks
Calcite Rhombohedral CaCO3 Dominant limestone mineral,
especially in rocks older than
Cenozoic
Aragonite Orthorhombic CaCO3 Dominant mineral in Recent
carbonate sediments; alters readily
to calcite
7. How do limestones form?
• Most limestones are simply the cemented
remains of marine shells
• Limestone “anatomy”
– Grains
• Skeletal particles, ooids, peloids
– Lime mud
• Microscopic crystals produced by calcareous algae
and through abrasion of larger particles
– Cement
• Inorganically precipitated CaCO3 crystals
13. Factors affecting precipitation of
CaCO3 in sea water
Factor Type of change Physical effect Effect on CaCO3
Temperature Increase Loss of CO2,
increase in pH
Increase
precipitation
Pressure Decrease Loss of CO2,
increase in pH
Increase
precipitation
Salinity Decrease Decrease activity
of “foreign”
cations
Increase
precipitation
Photosynthesis Removes CO2 from sea water; pH
increases
Increase
precipitation
Bacterial activity Catalyzes CaCO3 precipitation Increase
precipitation
14. Where do limestones form?
• Because CaCO3 precipitates most readily in
warm, well lit, agitated water of normal
marine salinity…..most limestones form in
shallow, tropical depositional
environments
– e.g., Bahamas, central America, Persian Gulf, NW
shelf of Australia, Great Barrier Reef, Malaysia,
Indonesia, etc.
15. What are limestone products?
• Whole rock
– Crushed limestone
– Dolomitic limestone
• Burned lime (calcium oxide)
– High calcium lime
– Dolomitic lime
• Hydrated lime (calcium hydroxide)
16. How is limestone used?
• Construction
• Soil stabilization
• Flue Gas Desulfurization
• Steel Production (flux for blast furnaces)
• Glass Production
• Water Treatment
• Waste Treatment
• Paper Production (filler)
• Chemical Production
• Masonry, Mortars and Other Building Materials
19. ⦁ The word "granite" comes from the Latin granum,
⦁ Granite is a common type of
plutonic intrusive, felsic, igneous rock which is granular
and phaneritic in texture.
⦁ This rock consists mainly of quartz, mica, and feldspar.
⦁ By definition, granite is an igneous rock with at least 20% quartz by
volume. Outcrops of granite tend to form rounded massifs. Granites
sometimes occur in circular depressions surrounded by a range of
hills.
⦁ Granite is nearly always massive ,hard and tough, and therefore it has
gained widespread use as a construction stone. The
average density of granite is between 2.65 and 2.75 g/cm3,Melting
temperature is 1215 - 1260 °C.
20. Essential minerals
⦁ Feldspar and quartz are the most important
mierals
⦁ Quartz makes up about 10-30%
• it is anhedral and occur as phenocryst
⦁ Feldspar-alkali feldspar,orthoclase,microcline
Orthoclase
Quartz
Feldspar
21. Accessory minerals
⦁ Biotite –common mafic mineral in granites.colour varies with fe
content.
⦁ Hornblende-green hornblende seen in calcalkali granites
⦁ amphibole
⦁ Pyroxene
⦁ Hedenbergite
Minor accessories
⦁ Tourmaline,(schorl rock)
topaz,epidote,garnet(almandine,spessartine),apatite,epidote
22.
23. ⦁ Granite is classified according to the QAPF diagram for coarse
grained plutonic rocks and is named according to the percentage
ofquartz, alkali feldspar (orthoclase, sanidine, or microcline)
and plagioclase feldspar.
⦁ Granite differs from granodiorite in that at least 35% of the feldspar in
granite is alkali feldspar as opposed to plagioclase; it is the alkali
feldspar that gives many granites a distinctive pink color.
⦁ When a granitoid contains less than 10% orthoclase, it is
called tonalite; pyroxeneand amphibole are common in tonalite. A
granite containing both muscovite and biotite micas is called a binary
or two-mica granite. Two-mica granites are typically high
in potassium and low in plagioclase, and are usually S-type granites
or A-type granites. The volcanic equivalent of granite is rhyolite and
hypabyssal is granophyre(Tyrrell’s classification)
24. ⦁ Granite is a phanerocrystalline rock which is
medium to coarse grained.
⦁ They also in holocrystaline, hypidiomorphic,
granular rocks
⦁ Some granites exhibit porphyritic
texture(phenocryst-feldspar), orbicular texture,
graphic(qtz & fldspr), granophyric texture
⦁ Occasionally some individual crystals (phenocrysts)
are larger than the groundmass, in which case the
texture is known as porphyritic. A granitic rock
with a porphyritic texture is sometimes known as
a porphyry. Granites can be pink to gray in color,
depending on their chemistry and mineralogy.
25. ⦁ Granites occur as huge batholiths of great dimensions usually
occuring in the cores of mountain
ranges(stocks,bosses,laccoliths)
⦁ The huge bodies does not show any peculiar structure
⦁ Moral jointing is common and rift and grain is also present in
most varieties.
⦁ The basic minerals like biotite,amphibole occur as
seggregations and patches in the granite body.sometimes
parallel arrangement of minerals(foliation) may be seen
26. ⦁ Mica granite –the micas,muscovite and biotite together make up
10% of the rock. other accessory minerals are allanite, sphene,
apatite, magnetite and guorite. It is the most abundant type of
granite.
⦁ Biotite hornblende granite – these are next in abundance. These
rocks are somewhat more basic. A few of them carry pyroxenes.
⦁ Pyroxene granite- this type is rare. Biotite and hornblende are
entirely absent here or make up only vary small
amount.clinopyroxene is the chief mafic minerals. Orbicular
granite – it exhibits orbicular structure. The orbicules are made
up of layers of biotite and quartz.
⦁ Granite, pegmatites and aplites – these are very common in
and around a granitic body. The pegmatites have the intergrowth
texture and are very coarse grained. They are store house of a
number of valuable minerals. The aplites are finegrained,
equigranular, allotriomorphic rocks. They occur as contact facies
in a granitic body.
27. ⦁ Alkali granite – this is a granite marked by the occurrence of
amphibole and puroxene rich in Na and Fe. The rock is
usuallymade up of sodic and potassic feldspars(75%).perthite
is common. Aegerine and riebeckite are the common mafics.
Accessories are apatite,sphene,zircon,iron ore etc.
⦁ Porphyritic granite – exhibits the porphyritic texture.
Phenocrysts are orthoclase, microcline, perthite.
28. ⦁ Granite and granite gneiss are too common in peninsular
India and cover vast areas in Indian geology.
⦁ Typical granite occurrences are Singhbhum granite(Bihar),
Bundelkhand granite(Rajasthan), Erinpura granite, Idar
granite, Closepet granite, Chamundi granite(Karnataka).
⦁ Granites of North arcot and Sankaridrug in Tamilnadu and
granites of Himalayas.alkali granite are seen in Siwana and
Tatanagar.
29.
30. ⦁ It is a coarse-grained structure of such a crystalline rock.
⦁ Granite is usually found in the continental plates of the
Earth's crust(magma).
⦁ This rock consists mainly of quartz, feldspar, mica etc
⦁ (Curling) another name for a granite stone.
⦁ A common, coarse-grained, light-colored, hard igneous rock
consisting chiefly of quartz, orthoclase or microcline, and
mica, used in monuments and for building.
31. ⦁ Igneous and metamorphic petrology(1962), Francis
J.Turner,McGraw-Hill book company.
⦁ http://en.wikipedia.org/wiki/Granite
⦁ http://www.thefreedictionary.com/granite
33. • Introduction
• Mineralogy
• Textures
• Classification of dolerite
• Dolerite dyke
• Formation of dolerite
• Distribution
• Uses
• Conclusion
34. • A dolerite is the medium-grained equivalent of a
basalt - a basic rock dominated by plagioclase and
pyroxene.
• Dolerites also often include olivine or quartz and
can be alkali basalts, olivine tholeiites or quartz
tholeiites. They can contain a wide range of
accessory minerals including hornblende and
biotite. Dolerites usually have an ophitic texture
35. • Dolerite is typically found as a hypabyssal igneous
rock, typically within dykes. Dykes may also
contain basalt instead of dolerite.
• Diabase is often used as a synonym of dolerite by
american geologists, however, in europe the term
is usually only applied to altered dolerites.
36. Mineralogy: Phenocrysts comprise olivine (olivine diabase) and/or
pyroxene or plagioclase. The groundmass comprises the same
minerals with iron oxide, and sometimes with some quartz,
hornblende or biotite.
37. • Ophitic texture - laths of plagioclase in a coarse
grained matrix of pyroxene crystals, where in the
plagioclase is totally surrounded by pyroxene
grains. This texture is common in diabases and
gabbros.
• Subophitic texture - similar to ophitic texture
where in the plagioclase grains are not completely
enclosed in a matrix of pyroxene grains.
38.
39.
40. • Pyroxene and calcic plagioclase,typically
labradorite ,as essential constituents,with or
without some olivine and a variable amount of
interstitial residum consisting of alkali feldspar
and quartz, often intergrowth .
• The accessory constituents are iron-ore and
apatite with ,in some a little hornblende or
biotite.
41. • Single lime-rich more or less titaniferous
augite as their pyroxene.
• They normally have olivine as a further
essential constituent and not infrequently
have a little interstitial analcite.
• They may be illustrated by those occurring
in Tertiary igneous province of scotland.
43. A view of
the dolerite
dyke cutting
through the
granite.
44. Sam Edwards on
the first ascent of
Slap Dancer (26,
5.12b), a dolerite
pillar in the Organ
Pipes, Tasmania,
Australia
45. Formation of
dolerite
Dolerite cools under
basaltic volcanoes, like those
at mid-ocean ridges. It cools
moderately quickly
when magma moves up into
fractures and weak zones below a
volcano. There, it forms dikes
(tabular igneous rock bodies that
cut across pre-existing rock layers
or bodies) or sills(tabular igneous
rock bodies that form parallel to
pre-existing rock layers). The
moderate cooling rate allows small
visible crystals to form in the rock.
46. Distributio
n
• Tholeiitic dolerite - occur in karroo of
South Africa and those of Tasmania and
Antartica were intruded.
• Alkali dolerites - occur in Scotland
particularly in where they may form large
sills. Midlands of England, as at Rowley
Regis, near Birmingham; in the Clee hills,
Shropshire and Derbyshire.
47. In geological timescale this Karoo dolerite intruded
approximately 83 million years ago during the
Mesozoic era
48. • Dolerite are used in monumental
masonry,building material,concrete
aggregate, paving stone, road stone, road
stones and ornamental stones.
Uses
49. Conclusion
• A dolerite is the medium-grained equivalent of a
basalt - a basic rock dominated by plagioclase and
pyroxene.
• One of its distinguishing character is its ophitic
texture.
• Dolerite is typically found as a hypabyssal igneous
rock, typically within dykes, however, it may also
occur in sills.
• Tholeiitic dolerite and alkali dolerite are the two
types.
52. INTRODUCTION
Basalt is a common extrusive igneous or volcanic
basaltic
rock formed from the rapid cooling of
lava exposed at or very near the surface.
It is also known as a dark volcanic rock
The term basalt is at times applied to
shallow intrusive rocks with a composition typical of
basalt, but rocks of this composition with a coarse
groundmass and are generally referred to as gabbro.
53. ENVIRONMENTAND OCCURENCE
Basalts commonly occur as lava
flows because of their low volatile
content
When rising basaltic magma
encounters groundwater the magma
may vesiculate to form flow
breccias or erupt to form cinder cones
It covers all the ocean floor except where they
themselves are covered by continental-margin
sediments.
54. CONT……
It is the most abundant igneous rock at or near the
earth’s surface
The most voluminous are also called MORB
The great flood of basalts that have been extruded
onto the continents, form extensive nearly horizontal
flows erupted from fissure swarms
Most basalts are erupted from tensional or rift
environment except for the arc volcanic rocks or hot-
spot basalts.
55. Mineralogy
Composed of plagioclase feldspar and pyroxene in
the ratio of 50:50.and magnetite and may contain
olivine.
Alkaline basalts may contain a little nepheline or
alkali feldspar
On the basis of mineralogy there are three different
types of basalts viz., tholeiitic, transitional and alkali
basalts
56. Basalt is usually grey to black in colour, but
rapidly weathers to brown or rust-red due to
oxidation of its mafic (iron-rich) minerals
into rust
Alteration minerals in ocean floor basalts
include green to light brown palagonite,
chlorite, epidote, celadonite, goethite,
hematite, calcite and zeolite
60. TYPES OF BASALTS
Tholeiitic basalt: relatively rich in silica and poor
in sodium. Basalts of the ocean floor and
continental flood basalts comes under this.
MORB (Mid Ocean Ridge Basalt): characteristically
low in incompatible elements. Commonly erupted
only at ocean ridges.
High alumina basalt :may be silica-undersaturated or
oversaturated. Alumina (Al2O3) content is more than
17% and intermediate in composition i.e.between
tholeiite and alkali basalt
61. CONT….
Alkali basalt:relatively poor in silica and rich in
sodium. It is silica-undersaturated and may
contain feldspathoids, alkali feldspar and phlogopite
Boninite: is a high-magnesium form of basalt that is
erupted generally in back-arc basins, distinguished by
its low titanium content and trace element
composition.
62. ORIGIN
The origin of basaltic magma is universally accepted
as involving melting within the earth’s mantle
Evolve by fractional crystallization as separate series
along different paths. Each is chemically distinct
Tholeiites are generated at mid-ocean ridges, oceanic
islands, subduction zones
Alkaline basalts generated at oceanic islands and at
subduction zones
63. Cont..
The melting behavior of basalts indicates that it is
the partial melting products of a more primitive
rock (e.g. garnet peridotite).
In the region of magma generation (below 60 km)
the parental material, presumed to be garnet
peridotite, yields an eclogitic magma and its
fractionation depends on the garnet and omphacite
of the eclogite, not on plagioclase and
clinopyroxene of a basaltic magma.
64. Cont…
Increase of the garnet constituents in the magma at
high pressure by effective removal of omphacite or
shift of the garnet-omphacite boundary surface will
give rise to a tholeiite-type magma at low pressure.
Increase of the omphacite constituents in the magma at
high pressure by physical or physicochemical means
will give rise to an alkali basalt-type magma at low
pressure.
In general, alkali basalt-type magmas are to be
expected to be generated at greater depths than
tholeiite-type magmas from the same primary source
rock.
65. Theories
Origin 1: Mechanism involving partial melting under
under different condition
-higher pressure or lower temperature partial melting
of mantle material produce alkaline basalt whereas
lower pressure or higher temperature partial melting
produce tholeiitic magma
2: Mechanism involving stage of melting or degree of
melting
-early stage of partial melting of garnet peridotite
produce tholeiitic basalt, whereas an intermediate
stage give rise to alkaline olivine basalt
66. Cont….
3. Mechanisms involving partial melting of a mantle
source of different composition
- MOR basalts contain less radiogenic Pb and Sr, and
more radiogenic Nd, and depleted light REEs
compared with continental tholeiites and are
probably derived from mantle of different
compositions
- Tholeiitic basalts form by partial melting of peridotite
containing H2O, K2O, and Na2O whereas alkaline
basalts form by partial melting of peridotite richer in
CO2, TiO2, and P2O 5
67. Cont…
4. Mechanisms involving differentiation or fractional
crystallisation
- Higher pressure fractionation of basalt formed by
partial melting in the mantle could give alkaline
basalt, whereas lower-pressure fractionation of the
same basalt could give tholeiitic magma
- Partial melting at a depth of about 60km could give
alkali basalt. Partial crystallisation at a depth of about
40km could produce transitional basalt
- Partial melting of peridotite and leaching of
68. Cont…
Wall rocks during ascent of the magma could form
alkali basalt
- limited partial melting of garnet peridotite could
produce alkali basalt and more extensive melting
give tholeiitic basalt
- Incipient melting of heated mantle wall rocks
produced early alkalic melts; later melting could
produce tholeiitic melts; stagnation as the volcano
moved off the hot spot and a decrease in melting of
the wall rocks would form the latest alkalic basalts
69. Cont…
• -Separation of high Mg olivine and pyroxene at a
depth of 15 to 35 km could form high Al basalt
• 5. Mechanisms involving a particular
tectonic environment
• -Basaltic melt from a deep mantle plume
accumulates at the base of the lithosphere.
• Magma at the base of the lithospheric plate finds
access to the surface along zones of crustal weakness
70. Cont….
- Alkali basalts volcanism may be associated with the
lateral edge of a subducting lithosphere plate.
- Tholeiitic and transitional basalts such as those
formed at a mid-oceanic ridge could originate by
partial melting at modest pressures below about 8 to
10 kbars or depths of 30 to 35 km.
71. Deccan Traps
The Deccan Traps are a large igneous province
located on the Deccan Plateau of west-central India
and one of the largest volcanic features on Earth
They consist of multiple layers of solidified flood
basalt that together are more than 2,000m thick and
cover an area of 500,000 km2 and a volume of
512,000 km3
The basalt flows are generally massive, compact
and coarse grained in central part but become fine
grained near top and bottom parts
72. Cont…
Within the Deccan Traps at least 95% of the lavas
are tholeiitic basalts, however other rock types like
Alkali basalts, Nephelinites, Lamprophyre,
Carbonatites also occur.
Mantle xenoliths have been described
from Kutch (northwestern India) and elsewhere in
the western Deccan.
73.
74. Cont…
The Deccan Traps eruption was associated with a
deep mantle plume.
The area of long-term eruption known as
the Reunioun hotspot, is suspected of both causing
the Deccan Traps eruption and opening the rift that
once separated the Seychelles plateau from India.
The basalt deposits in the Seychelles are from
the Deccan Traps eruption, which occurred in the
central part of the Indian sub-continent 65 million
years ago, at the end of the Cretaceous period
77. The Deccan Traps at Mahabaleshwar.These comprise multiple layers of flood
basalt, over a mile deep, the result of massive volcanic activity at the K/T
boundary. Some regard this as the cause of the extinction event
79. Economic importance
Flood basalts are known to host important
deposits of native copper and platinoids
Bauxite cappings over Deccan Trap as in
Belgaum are useful as aluminium ore
Natural zeolites filling the cavities in volcanics
are useful as gemstones and have industrial and
agricultural applications
used in construction as building blocks or in the
groundwork, making cobblestones (from
columnar basalt) and in making statues. Heating
and extruding basalt yields stone wool, an
excellent thermal insulator
80. Conclusion
Basalt is a common extrusive igneous rock formed
from the rapid cooling of basaltic lava exposed at or
very near the surface.
It is an aphanitic igneous rock
tholeiitic, transitional and alkali basalts are the three
important types of basalts
81. Cont….
It is formed by fractional crystallisation along
different paths
Seafloor spreading at the boundary between
the Indian and African Plates subsequently
pushed India towards north, which now lies
under Reunion island in the Indian Ocean,
southwest of India
Important texture present in basalt is called
amygdaloidal texture
