Igneous and Metamorphic rocks, 6312014/2015

Prof. Ahmad Malabeh

Laith khaled alsalman (2014330006)

Deccan Trap in India

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.

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.

World traps (basaltic flow)

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.

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)

Deccant trap -plateau- in India which classified as volcanic

plateau, which will study in this show..

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

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

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.

India/Asia plates clip:

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).

Himalayan mountain built

clip:

Deccan trap in India.

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.

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 Proterozoicbasement 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 Baghand Lameta sediments, and Archaeanand early Proterozoic crystalline rocks (granites, gneisses and metasediments).

Google view (the Western & Eastern Ghats mountains in south

India).

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)

The mantel plume movemant:

: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.

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,,

Fig. 1

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.

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.

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.

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

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).

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)

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

Unhavare Hot Spring: Profiles L1 & L2

2D Resistivity model near Unhavare hot spring (a) along L1 profile. (b) along L2 profile.

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

profile.

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

villages.

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.

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 petrologicaldiscussion.

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.

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.