3. Acknowledgement
All our group members have contributed significantly in compiling
this project. However, it would not have been possible without the
kind support and help of our professors, Prof.ArindamBasu and
Prof.Abhijeet Mukherjee. We would like to extend our sincere
thanks to both of them.
We are highly indebted to Mr. Bikas Kumar Ram and Mr. Hemant
Singh for his guidance and constant supervision, providing
necessary information regarding the fieldtrip and for his extensive
support in completing the report.
4. INDEX
INTRODUCTION
Objective
Study area and its Stratigraphy
Geological field work done in and around Balasore
Location
Lithology
Study of different composition Granite
Geological structures
Data Analysis and Discussion
Rock samples pictures
Appendix
5. INTRODUCTION
Objective :To study the Geological aspect of the region around Balasore(North
Orrisa). Observing the different composition of minerals in Singhbum granite to
know the stratigraphy of the area. To observe the different grades of weathering.
This report is a brief synopsis of the Field Trip for the second year students of
2014-19 UG Batch of the Department of Geology and Geophysics, Indian Institute
of Technology, Kharagpur dated 7/12/2012 to 15/12/2012.
The area under analysis and observation is geographically located in Balasore,
North Orissa. Geologically, this region is a part of the Singhbhum Craton which is
considered to be one of the oldest and the first formed landmasses on Earth. The
Singhbhum Craton is an approximately 40000 sq. kms batholithic mass having
varied geological features, most of them relating to as old as the Pre-Cambrian Age.
According to Geological Survey of India, the region is well known for its rich
deposits of iron and copper. The rocks found in this region are Singhbhum Granite,
Hornblende Gneiss, Hornblende Granite, Dolerite, Granophyre and Red Laterite
rocks. Very old rocks like OMG(Older Metamorphic Group) and OMTG(Older
Metamorphic Tonalite Gneiss) which dates back to 3-4 Billion years.
6. Location-1 : NILAGIRI
Latitude – 21̊ 27 ̍ 53.4 ̎ N
Longitude – 86̊ 46 ̍ 11.8 ̎ E
Location on GSI Map
Location (fig 1.1)had singhbhum granite which are 3.8 billion years old. The
presence of an Unconfirmity is identified as unconsolidated sediments are present at
very close distance (according to the map).
According to Geological Survey of India, SinghbhumGranite ,a type of older
metamorphic rock(OMG approx. 3.8billion years) is found in Nilagiri region.
Considerable vegetation and light colored minerals are present in
The Nilagiri region, which is 25 km South West (SW) of Balasore , comprises of
Crystalline Rocks.
: NILAGIRI
.1)had singhbhum granite which are 3.8 billion years old. The
presence of an Unconfirmity is identified as unconsolidated sediments are present at
close distance (according to the map).
According to Geological Survey of India, SinghbhumGranite ,a type of older
metamorphic rock(OMG approx. 3.8billion years) is found in Nilagiri region.
Considerable vegetation and light colored minerals are present in the nilagiri region.
The Nilagiri region, which is 25 km South West (SW) of Balasore , comprises of
.1)had singhbhum granite which are 3.8 billion years old. The
presence of an Unconfirmity is identified as unconsolidated sediments are present at
According to Geological Survey of India, SinghbhumGranite ,a type of older
metamorphic rock(OMG approx. 3.8billion years) is found in Nilagiri region.
the nilagiri region.
The Nilagiri region, which is 25 km South West (SW) of Balasore , comprises of
7. On observing the rocks different minerals are identified on the basis of Lustre ,
Colour and Cleavage Planes and textures.
The minerals in the rocks are determined to be Quartz(fig 1.2), Plagioclase
Feldspar, Muscovite (Small Quantity), Orthoclase Feldspar ( Small Quantity) and a
Black Mineral (which cannot be easily determined) .
Quartz has Vitreous lustre and has no Cleavage Sets
Plagioclase Feldspar is White to Yellow in Colour, has lustre Sub-Vitreous and
shines more than Quartz has cleavage sets.
Muscovite is a white coloured flaky mineral, having single cleavage plane.
Joints – A fracture dividing rock into two sections that have not moved away from
each other . They occur in parallel sets and are distinguished from fractures and
fault planes.
Fractures do not occur in parallel sets over a region but joints do occur
Faults are the fractures dividing rock into two sections that have moved away from
each other.
Formation of Joints -
When magma crystallizes beneath the surface of the earth, Some parallel isothermal
planes subnormal to which the stresses are maximum puts the either side of rock
apart to form Joints.
Joints control the stability of rock because the magma while crystallizing separates
into different rock along joint planes.
OBSERVATIONS –
Most of the rocks are Hard and Massive.
Distinct joint sets are observed in the rocks with moderate joint spacing.
Rocks are mostly weathered due to exposure to air, water and other physical
conditions.
On the basis of our observation, we identified that there were three different clusters
of joints as shown in stereogram.
8. Fig 1.1:Location Overview Fig 1.2: Quartz Cluster spread in the area
The attitude data of rocks were collected and are shown below:
TABLE 4:
Stereonet of the collected data :-
10. Location-2/6: MIRGUNI
Latitude – 21̊ 27 ̍ 1.9 ̎ N
Longitude – 86̊ 45 ̍ 24.54 ̎ E
Location on GSI Map
According to Geological Survey of India, Newer Dolerite Dykes intruded through
Singhbhum or Hornblende Granite basement
In this location newer dolerite dykes intruded through singhbhum granite basement,
the country rock (Hornblende Granite). The region was a mining site. The site has a
deep water reservoir, formed due to mining activities. Parts of the left over dykes
were observed in some parts surrounding the reservoir with blackish appearance
presumably comprising Dolerites.
The rocks are hard and massive. The Country rock of the region was granite with
more content of Hornblende in it that’s why named as Hornblende Granites.
: MIRGUNI
According to Geological Survey of India, Newer Dolerite Dykes intruded through
Singhbhum or Hornblende Granite basement is found in Mirguni(Fig
In this location newer dolerite dykes intruded through singhbhum granite basement,
ock (Hornblende Granite). The region was a mining site. The site has a
deep water reservoir, formed due to mining activities. Parts of the left over dykes
were observed in some parts surrounding the reservoir with blackish appearance
Dolerites.
The rocks are hard and massive. The Country rock of the region was granite with
more content of Hornblende in it that’s why named as Hornblende Granites.
According to Geological Survey of India, Newer Dolerite Dykes intruded through
is found in Mirguni(Fig-2.1).
In this location newer dolerite dykes intruded through singhbhum granite basement,
ock (Hornblende Granite). The region was a mining site. The site has a
deep water reservoir, formed due to mining activities. Parts of the left over dykes
were observed in some parts surrounding the reservoir with blackish appearance
The rocks are hard and massive. The Country rock of the region was granite with
more content of Hornblende in it that’s why named as Hornblende Granites.
11. There are two types of rocks in the region –
1. Country Rock (Hornblende Granites)
2. Doleritic Dykes ( Comprising of Dolerites)
Hornblende Granite contains Quartz, Plagioclase Feldspar, Hornblende (In higher
quantity than Singhbhum granites), Orthoclase Feldspar (Small Quantity), which
are identified through their lustre, colour and cleavage planes.
Silica Veins are found in most of the rocks. It mainly comprises of Quartz. When
Hydrothermal fluid extrudes up to the surface and settles in the country rock
,since Quartz is the last phase to crystallize according to Bowen reaction series
,Quartz settles in the fractures of the rocks hence forming the quartz Veins.
The colour of the rocks changes to yellow due to the action of rainwater, air and
other factors (Physical Weathering).
The Country rock (Hornblende Granite ) is intruded by Dykes . The dykes mostly
comprises of Dolerites which constitutes of Orthopyroxene and Plagioclase
Feldspar. Dolerites are Hypabyssal igneous rocks. Although these are Plutonic
igneous rocks which are formed beneath the surface, they come up to the surface
mainly due to land upliftment and weathering, both of which are continuous
processes and have been going on for about 3.8 billion years.
OBSERVATIONS –
Based on the stereonet plot, it is observed that 3 sets of joint planes are
present in this region.
The Basement Rocks appeared to have gneissic trace over them. It is due to
Instantaneous release of pressure over the rocks thus forming foliations over
them.
12. Fig-2.1 : Location Overview Fig-2.2 : Specific joint sets
We visited Mirguni as our first site. A huge Dolerite Dyke which intruded the
country rock, Hornblende gniess made the whole exposure at Mirguni. Only some
parts of the dyke were observed as most parts had been taken out for economic
purpose. The rocks at the site had broken along the cooling joint planes(Fig-2.2)
due to some mining activities. The region also unconsolidated rocks broken off
from the country rock and dolorite dyke. Normally, Granite has very less amount of
hornblende but is rich in Biotite (about 4-5%) but the hornblende Granite/Gneiss
observed had considerable amount of Biotite along with Quartz and Plagioclase
with conspicuous amount of hornblende in the matrix. Quartz veins were found in
most of the rocks.The dyke cross-cutted the country rock which showed that the
dyke was younger than the country rock.
Thermal Exfoliation:Release of locked in stresses due to change in temperature.The
orthoclase content in the rock is more giving it a flashy colour.Sudden change in
atmospheric conditions induces uneven irregural expansions and contraction in rock
minerals which are different for different minerals resulting in foliation.
Contact Metamorphism:Metamorphosed granites are observed. It occurs due to
doleriticintrusion,which provides required conditions for metamorphism.
13. Quartz veins:Ptygmatic folding of veins are observed.Hydrothermal fluids extrudes
and settles in country rock(Hornblende Granite.Since quartz is the last phase to
crystalise according to Bowen Reaction Series hence the veins are composed of
quartz.
In the field grain size of country rock is relatively coarser than the intruded
dyke(dolerite).It is due to recrystallisation
Exfoliation surfaces was observed in the granite which happened due to diurnal
temperature difference. This happens in granite because it is hard and the
temperature variation between different layer was significant and grains are very
fine.
Fig-2.3 : Exfoliation Surface
Stereo Net of the collected Data:
14.
15. STEREONET 2 AND 3
Location-3 :Bhalukasauni
Latitude – 21̊ 28 ̍ 48.6 ̎ N
16. Longitude- 86̊ 41 ̍ 30.9 ̎ E
Location on GSI Map
This location is about 10 kms south of Bhalukasuni Village (Fig 3.1). The site was
an active mining site with rocks having blue surface because of the active mining.
Most of the rocks were a part of igneous Dolerite with more of Dolerite (Fig 3.2),
having parallel cooling joints which were formed together in Singhbhum Granite.
There was little vegetation, plausibly because of the water seepage from the cracks
which might have been formed due to the on-going mining activities. The rocks in
this region are younger than the country rock because this is a dyke that cross-cut
the pre-existing country rock.
The country rock of the region is Diorite which can be identified through the
minerals present in the rock Quartz, Plagioclase Feldspar (more abundant than
Alkali Feldspar), Alkali feldspar, Hornblende, Mica (very small).
Diorite is composed of various dark coloured minerals which explain its black
colouring. Diorite is a relatively finer grained than Granite rocks.
17. Compositional differences –
GRANITE – Content of (Alkali feldspar > Plagioclase Feldspar)
GRANODIORITE – Content of (Alkali Feldspar = Plagioclase Feldspar)
DIORITE – Content of (Alkali Feldspar < Plagioclase Feldspar)
The country Rocks of the region are older rocks .It is observed to be intruded by a
dyke containing minerals Orthopyroxene and plagioclase .The dyke is fine grained ,
Dark Coloured . The minerals in it (plagioclase) has sub-vitreous lustre. Hence, the
dyke is identified to be dolerite.
OBSERVATIONS –
The rocks showed distinct joint sets, which are parallel and very closely
spaced. On plotting the data of the rocks on stereonet, clusters of poles are
noticed in North-East, South-East and South – West Directions which defines
specific Joint sets.
Fig-3.1:Location Overview Fig-3.2: Joint Planes
Most of the rock mass is the dolerite dyke.A huge vein of thick quartz which looks
bluish due to its thickness are found here(Fig-3.3).
18. Fig-3.3 : Bluish thick quartz
The collected data depicting the attitude of dolerite rocks at the site is shown
below.—
Stereo Net of the collected data:
19. STEREONET 4
Location-4: NARANGPUR (TOWARDS NORTH OF
BHALUKASUNI VILLAGE)
Latitude – 21° 30 ̍ 21.3 ̎ N
Longitude- 86̊ 72 ̍ 19 ̎ E
The region looked like an abandoned mining site with reddish black soil covering.
A surface, one side of which has a pillow like structure and the other showing
vesicular structure with distinct transition between the two. Possibly the vesicles
might have formed due to release of trapped gases on cooling of lava and due to
leaching.
The pillow like structure might have formed due to under water cooling of lava,
water leached out most of the elements except Iron, Manganese, Aluminium and the
laterite thus formed is a result of residual concentration.
20. Leaching – Leaching is the loss of mineral and organic solutes due to percolation.
It is a mechanism of soil forming process of eluviation, which is the loss of mineral
and organic colloids.
Laterization -
Billions of years ago , there might be some magma flow in the region and
crystallized to form basaltic rocks. Laterites have a source rock. Thus they are
called secondary rocks. The red colour is due to Ferric Oxide (Limonite – Coetite) .
A possible hypothesis is that , the source rock ( Basalt) in the last millions of years
has transformed to laterites .
The source rock contains (Fe-pyroxene and Feldspar). When water reacts with Fe-
pyroxene and will leach out everything except Iron,Manganese and Aluminium .
When magma extrudes out from deep beneath the earth’s surface .It contains
minerals like pyroxenes ,Quartz , Plagioclase etc..
Since , Pyroxene comes in contact with atmosphere having temperature around 300
Kelvin. It becomes unstable.It will convert to stable form of Ferric oxide. Quartz
crystallizes at ~600°C which is much lower than Pyroxene , thus Quartz will be last
to crystallize according to Bowen reaction Series hence , We observe shiny (glassy)
particles in the region.
OBSERVATION -
Alternate red and black layered pattern was observed on the vertical cross sections
of the site .A possible hypothesis may be that this might have formed because of
several lava flows taking place at different intervals of time.
The inner surface might be more weathered because of water seepage through
vesicles that acts like tunnels.
The upper layer of the soil is hard while the lower layer is soft. Also, the upper
layer is vesicular , but the lower layer is having fine grained particles due to
percolation of water.
22. This location (fig-5.1)showed us the whole
rock) to grade-6(soil).The soil layers had huge boulders known as “Core stones”
which might have been formed due to seepage of chemical weathering agent
through the fractures and joint planes.
The country rock of the region is Singhbhum Granite which can be identified by its
constituent minerals which are Hornblende (dark coloured), K
These minerals are identified on the basis of
It is fine grained and discoloured
Singhbhum Granite more Hornblende and Feldspar grains are altered.
In one of the selected areas the top soil layer is 5
grading of weathering of rocks below the topsurface
increases.
In the other area weathering grade of these rocks vary laterally significantly.The top
layer is grade 4 weathered while the underlying rocks are harder and show 2
weathering, this may primarily attribute to the i
5.1)showed us the whole process of weathering from grade
6(soil).The soil layers had huge boulders known as “Core stones”
which might have been formed due to seepage of chemical weathering agent
through the fractures and joint planes.
region is Singhbhum Granite which can be identified by its
constituent minerals which are Hornblende (dark coloured), K-Feldspar and Quartz.
These minerals are identified on the basis of color, lustre and cleavage planes.
It is fine grained and discoloured due to weathering. In weathered part of
Singhbhum Granite more Hornblende and Feldspar grains are altered.
In one of the selected areas the top soil layer is 5-6 grade weathered while the
grading of weathering of rocks below the topsurface changes from 4
In the other area weathering grade of these rocks vary laterally significantly.The top
layer is grade 4 weathered while the underlying rocks are harder and show 2
weathering, this may primarily attribute to the influence of joints present there.
process of weathering from grade-1(bed
6(soil).The soil layers had huge boulders known as “Core stones”
which might have been formed due to seepage of chemical weathering agent
region is Singhbhum Granite which can be identified by its
Feldspar and Quartz.
color, lustre and cleavage planes.
due to weathering. In weathered part of
Singhbhum Granite more Hornblende and Feldspar grains are altered.
6 grade weathered while the
changes from 4-6 as the depth
In the other area weathering grade of these rocks vary laterally significantly.The top
layer is grade 4 weathered while the underlying rocks are harder and show 2-3
nfluence of joints present there.
23. Fig-5.1 : Location Overview Fig-5.2 : Weathered Rocks
Stereonet of the collected data is :-
25. Location on GSI Map
Location 7: PANCHALINGESHWAR: PANCHALINGESHWAR
26. Fig-5.1 : Location
The rocks observed here are called Granophyre (Fig 5.1). They are massive and
rounded due to the presence of feldspar in relatively higher amount. The minerals
that are identified (on the basis of colour, lustre,cleavage sets) to be present in large
amount are plagioclase feldspar, Quartz, Orthoclase feldspar.
The rocks are hard, fabricated and no joint planes are observed due to large in-
locked stresses acting within it. The hardness of these rocks could also be attributed
to its minerology and its typical microstructure.
27. Discussion
The Singhbhum Craton has rocks of various chronolological periods, different
geological features and evidences leading to various interesting hypothesis
regarding its formation.
The field trip starts at Nilagiri Region where we can find the oldest rocks of about
2.9 bya. The Singbhum Granite of about 2.9bya of Archaean Age, Newer Dolorite
Dykes and very young Proterozoic Laterite Deposits were found in the locations.
The region has a varied structural and lithological diversity. The hardness of the
rocks varied from easily crushable weathered Laterite to very hard Granophyre. The
Granophyre was highly massive and rounded whereas the Dolerite had sharp edges.
Distinct joint sets were observed in Singhbhum Granite, Hornblende
Granite/Gneiss, Dolerite but they were negligible in Granophyre and Laterite
Deposits.
Mineralogical differences were most prominent among the sites visited. Chemical
transformation of the minerals changed the rock type from Singhbum granite to
Hornblende Gniess. This all happened due to the magmatic differentiation during
the formation of rocks. Location-1 and Location-2 had newer Dolerite Dykes
whereas Locations 3,4,5 did not have any traces of Dolerite Dyke. Joint Planes were
more prominent and clearly visible at Location no. 1 and 2 compared to Locations
3,4,5. Location 3 gave us a complete picture of the grades of weathering(Fig-6).
The hardest rock we came across was Grannophyre found at location 5.
28. Fig-6 : Weathering Profile
Some Rock samples we came across during this field trip
Quartz Dolerite
