geology

1. Igneous and Metamorphic rocks, 631
2014/2015
Prof. Ahmad Malabeh
Laith khaled alsalman (2014330006)

2. Deccan Trap in India

3. The index of this show:
 The world & geologic traps.
 Tectonic history of India.
 Deccan trap in India.
 The plume hypothesis.
 The Réunion hotspot
 Basaltic lava flow in deccan (well studies).
 Dick study in deccan:
 Electrical Resistivity studies
 Geochemical & geophysical studies.
 References.

4. The world & geologic traps.
The term "trap" has been used in geology since 1785–95
for such rock formations. It is derived from the Swedish word
for stairs (trapp , trappa) and refers to the step-like hills
forming the landscape of the region.
The
plateau: (/pləˈtoʊ/ or /ˈplætoʊ/plural plateaus or plateaux),
also called a high plain or tableland, is an area of highland,
usually consisting of relatively flat terrain. A plateau is an
elevated land. It is a flat topped table standing above the
surrounding area. A plateau may have one or more sides with
steep slopes.

5. World traps (basaltic flow)

6. Plateaus can be formed by a number of
processes:
1) upwelling of volcanic magma.
2) extrusion of lava.
3) erosion by water and glaciers.
4) magma rises from the mantle causing the ground to
swell upward, in this way large flat areas of rock are
uplifted.
5) Plateaus can also be built up by lava spreading
outward from cracks and weak areas in the crust.
Plateau Large, flat elevated region usually bounded by cliffs.

7. Classification of plateaus
Plateaus are classified according to
their surrounding environment:
 Inter mountain plateaus: are the highest in the world,
bordered by mountains. The Tibetan Plateau is one such
plateau.
 Piedmont plateaus: are bordered on one side by mountains
and on the other by a plain or sea.
 Continental plateaus: are bordered on all sides by the plains
or seas, forming away from mountains.
 Dissected plateaus: are highly eroded plateaus cut by rivers
and broken by deep narrow valleys.
 Volcanic plateaus: are produced by volcanic activity.
The Columbia Plateau in the northwestern United States of
America is one such plateau. ( Deccan is one of them)

8. Deccant trap -plateau- in India which classified as volcanic
plateau, which will study in this show..

9. Distribution of Mesozoic-Cenozoic large igneous provinces (LIPs) with
silicic LIPs in italics. NAIP, North Atlantic Igneous Province; CAMP, Central
Atlantic Magmatic Province; Rajm. Rajmahal basalts; TVZ, Taupo Volcanic

10. Tectonic history of India.
A cartoon depicting the tectonic scenario of the Indian plate and the
neighbouring plates. The vectors represent plate motion velocities along the
Indian plate margins, computed using NUVEI-1A model (DeMets et al.,
1994). Black

11. In the late Cretaceous about 90 million
years ago, subsequent to the splitting
off from Gondwana of
conjoined Madagascar
and India, the Indian Plate split from
Madagascar.
It began moving north, at about 20
centimeters (7.9 in) per year and is
believed to have begun colliding with
Asia between 55 and 50 million years
ago in the Eocene epoch of
the Cenozoic, although this is
contested, with some authors
suggesting it was much later at around
35 million years ago. If the collision
occurred between 55 and 50 Ma, the
Indian Plate would have covered a
distance of 3,000 to 2,000 kilometers
(1,900 to 1,200 mi), moving faster than
any other known plate.

14. India/Asia plates clip:

15. Indian Plate is moving northeast at 5 cm/yr (2 in/yr), while the
Eurasian Plate is moving north at only 2 cm/yr (0.8 in/yr). India is
thus referred to as the “fastest continent“ .
This is causing the Eurasian Plate to deform, and the Indian Plate
to compress at a rate of 4 mm/yr (0.15 in/yr).

16. Himalayan mountain built
clip:

17. Deccan trap in India.

18. The Deccan Volcanic Province is one of the Earth’s giant
continental flood basalts and has a total exposed area of about half a
million square kilometers, between latitudes 16° - 24° N and longitudes
70° - 77° E.
In the northwestern, central and southern Indian peninsula, the
approximate volume of the DVP is about 2 x 106 km3 and its estimated
age is 64-65 Ma. It is generally believed that the DVP originated during
Gondwana land breakup as part of the Seychelles-India separation
event.

19. shows the main rock formations
that make up the Indian shield. Over a
large part of the province, the contact
of the Deccan lavas with the pre-
volcanic basement is not exposed.
The Deccan lavas overlie a
complex Archaean and Proterozoic
basement along the the southern and
southeastern periphery of the
province.
In the northern and northeastern
parts of the province, i.e., central
India, they overlie diverse geological
formations: the Vindhyan sedimentary
basin (mid-late Proterozoic), the
Gondwana sedimentary basin
(Carboniferous to Jurassic-early
Cretaceous), late Cretaceous Bagh
and Lameta sediments, and Archaean
and early Proterozoic crystalline rocks
(granites, gneisses and
metasediments).

20. Google view (the Western & Eastern Ghats mountains in south
India).

23. Mantle Plume Theory:
A global scale model showing the origin of large plumes from near
the Core/Mantle boundary. The large plume heads melt and produce
flood basalts whereas their tails persist for millions of years and
generate hot spot tracks.
(source refs. in: Sen 2001)

24. The mantel plume movemant:

25. :The Réunion hotspot
During Indian plat journey northward after breaking off from the rest of
Gondwana, It's passed over a geologic hotspot, the Réunion hotspot, as a
mantle plume which caused extensive melting underneath the Indian Craton.

26. Basaltic lava flow in deccan:
(Well studies) & (Formations)
The geologist have divided the lava flow stratigraphy in the
southwestern part of the province into 11 flow formations (Table 1) on
the basis of major and trace elements and Sr, Nd, and Pb isotope
ratios.
(e.g. Cox & Hawkesworth, 1985; Beane et al., 1986; Lightfoot et al., 1990; Peng et al., 1994; Subbarao et
al., 1994).
These studies have mostly focused on the stratigraphically 3400m
thick lava pile exposed in the type sections of the Western Ghats (Fig.
1), an escarpment that separates the western coastal plain (Konkan)
from the Deccan Plateau (Fig. 1a).
Several of these formations have been shown to extend far to the SE,
east, and/or NE. Although their chemical and isotopic variability in
distant locations is somewhat greater than seen in the Western Ghats
(e.g. Mitchell & Widdowson, 1991; Peng et al., 1998; Mahoney et al., 2000; Jay & Widdowson, 2008),
their relative stratigraphic position is constant.
* The data collected in Tabels below,,

27. Fig. 1

29. Composite chemostratigraphy and
magnetostratigraphy of the main Deccan
province (MDP). Individual formational
units are shown to approximate thickness.
Age data are provided for magnetochron
boundaries.

34. Diks study in deccan:As we see above Deccan traps mainly composed of nearly flat
lying tholeiitic flows, many of which are laterally extensive although
their eruptive vents have not been found., Because flood basalts are
the products of dike-fed fissure eruptions, the study of Deccan dikes
as potential feeders to the Deccan flows is crucial for: determining
the eruptive source area(s), the lengths of lava flows, and the
architecture of the flood basalt field and its evolution during the flood
basalt event, the lengths of lava flows, and the architecture of the
flood basalt field and its evolution during the flood basalt event.
Three large dike systems are exposed in the deccan traps flood
basalt province of India: the dominantly north-south-trending west
coast swarm, the east-west-trending Narmada Tapi swarm in the
north-central Deccan, and the Nasik Pune swarm in the central
western Deccan.
Combined major and trace element and Sr-Nd-Pb isotope data
reveal that probable feeder dikes for the three main lava formations
in the upper part of the lava pile (Poladpur, Ambenali and
Mahabaleshwar Formations) are abundantly represented in the Nasik
Pune and coastal swarms.

35. Map of the DeccanTraps (gray), important localities mentioned in the text (white
squares), intrusions of Mundwara and Barmer (white circles), and the three major dike
swarms (shown schematically). Rectangles delimit the areas of each swarm for which
we made substantial numbers (indicated by n) of dike-strike measurements,
summarized in the rose diagrams. The white dashed line near the west coast represents
the Panvel flexure (after Subrahmanya, 1998). Dh., Dhadgaon; De., Dediapada.

37. Field photographs, a The Tamia scarp and Deccan basalt lava flows overlying
Gondwana sandstone. b Dyke PMD7 along Denwa River bed, dipping roughly north (left)
and with columns perpendicular to its contacts. c Dykes PMD8 and PMD9 on the Denwa
River bed. d The 28–34 m wide Satdhara dyke PMD11

39. Photomicrographs of some of the Pachmarhi dyke samples showing
typical textures (see text). a Sample PMD1, crossed polars, view 1.5
mm wide. b PMD12, crossed polars, view 6 mm wide. c PMD16,
crossed polars, view 1.5 mm. d PMD6, over the polarizer, view 1.5 mm.
Mineral grains are marked as ol (olivine), cpx (clinopyroxene), pl
(plagioclase), and ox (Fe–Ti oxide).

41. Electrical Resistivity Tomography Technique
in Deccan (Geothermal studies)
Geothermal energy is one of the cleaner sources of energy
which are gaining importance as an alternative to hydrocarbons.
According to Gupta and Roy (2007), more than 20 countries
generate electricity from geothermal resources and about 60
countries make direct use of
geothermal energy. Geothermal studies have been carried out by
many researchers to quantify the thermal characteristics of
different geological provinces in India and to evaluate their
suitability for geothermal exploration (Panda, 1985; Ravi Shankar, 1988; Gupta,
1993).
Electrical Resistivity Tomography (ERT) was carried out along two
profiles, namely L1 & L2 near Unhavare hot spring (Fig.2).
(The map next slid)

42. Fig.2. Location of hot springs and ERT profiles in the study area.

43. Unhavare Hot Spring: Profiles L1 & L2
2D Resistivity model near Unhavare hot spring (a) along L1 profile. (b) along L2 profile.

44. 2D Resistivity model near Tural hot spring (a) along L3 profile. (b) along L4
profile.

45. CONCLUSIONS of resisitivity study:
Interpretation of computed resistivity models along eight profiles at 4 hot springs
sites indicates the presence of potential geothermal reservoir at some
places. For Unhavare (Khed) hot spring, 2D resistivity model for profile L1
shows potential reservoir of hot water with resistivity <1 Ohm-m at 15 m
depth.
This reservoir shows downward extension (i.e., resistivity decreasing with depth)
which appears to be associated with a fault extended to a deeper depth
beyond 67 m and could be linked with the reservoir of Unhavare hot spring
at deeper level.
Another reservoir with a resistivity <5 Ohm-m below 8 m depth between 237 m
to
260 m towards SE end is delineated at profile L2.
For Tural hot spring, a geothermal reservoir between 135 m and 205 m on L3
profile and between 105 m and 235 m on L4 profile with <13 Ohmm
resistivity at 35 m depth is deciphered which is connected to a deeper heat
source.
For Aravali hot spring, a very low resistivity zone (<10 Ohm-m) along L8 profile
indicates the presence of a geothermal reservoir between 70 m to 130 m at a
depth of about 5 m. In addition, two potential sites are delineated for
groundwater exploration on L5 profile at Rajwadi and L7 profile at Aravali

46. Geochemical & geophysical
studies.
Within the Deccan Traps at least 95% of the lavas are tholeiitic basalts,
with Alkali basaltic rocks, Nephelinites, Lamprophyre, Carbonatites and
Mantle xenoliths.
Hear a plot of 624 samples of Deccan basalts of the Western Ghats (data of
Beane, 1988; courtesy J. J. Mahoney) on the well-known TAS diagram. Note
the complete absence of compositions other than basalt and basaltic
andesite, and the nearly exclusive subalkalic (tholeiitic) nature.
Dividing lines between alkalic and subalkalic fi elds proposed by Macdonald
& Katsura
(1964) and Irvine & Baragar (1971) are also shown.

47. This Plot of the same samples on the familiar AFM
diagram, Showing the Fe enrichment trend typical of
tholeiitic basalts.
Typical tholeiite trend (Thingmuli, Iceland)
and calc-alkaline trend (Cascades) are also shown,
along with boundaries between the two fi elds proposed
by Kuno (1968) and Irvine & Baragar (1971).
See Sheth (2005b) for an extended petrological
discussion.
MORB shows less crystal fractionation than
flood basalts, evidencing the fact that the
Deccan may have been subject to rapid melt
ascent and associated de-compression
melting resulting in olivine/magnetite crystal
fractionation.
The fact that there are no olivine crystals or
mantle xenoliths in the Deccan suggests a
period where the melt was held in a magma
chamber where they were able to settle out of
suspension before eruption.

49. References:
 Hetu C. Sheth Department of Earth Sciences, Indian Institute of Technology (IIT)
Bombay, Powai, Bombay (Mumbai) 400 076 India.
 Gautam Sen Department of Earth Sciences and Florida Center for Analytical Electron
Microscopy, Florida International University, University Park, Miami, FL 33199.
 RECEIVEDMARCH 31, 2010; ACCEPTED NOVEMBER 10, 2010 ADVANCE ACCESS
PUBLICATION JANUARY 3, 2011
 H. C. SHETH Department of Earth Sciences, Indian Institute of Technology (IIT)
Bombay, Powai, Mumbai 400 076, India (email: hcsheth@iitb.ac.in)
 S. Rajan, Anju Tiwary & Dhananjai Pandey National Centre for Antarctic & Ocean
Research, Headland Sada, Vasco-da-Gama, Goa-403 804, India,
 M. Widdowson ’ , K.G. Cox Depurtment ofEarth Sciences, Parks Road, Oxford. OXI
3PR. UK Received 9 June 199.5; accepted 30 October 1995
 DEWASHISH KUMAR, S. THIAGARAJAN and S. N. RAI Council of Scientific and
Industrial Research (CSIR) - National Geophysical Research Institute, Uppal Road,
Hyderabad - 500 007.
 Hetu C. Sheth ⇑, Kanchan Pande Department of Earth Sciences, Indian Institute of
Technology Bombay (IITB), Powai, Mumbai 400076, India.
 Other geologic sites in internet with YouTube video & other spatial GIF pictures locations
& G_maps.