Deccan trap

geology

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

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  /ˈ pl æ toʊ / 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.

12. India/Asia plates clip:

13.  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).

14. Himalayan mountain built clip :

15. Deccan trap in India.

16. 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 10 6 km 3 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.

17. 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 ).

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

19. 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)

20. The mantel plume movemant : crust mantel core plume

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

22. Basaltic lava flow in deccan: (Well studies) & (Formations) T he 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. 1 a). 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,,

23. Fig. 1

24. 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.

25. 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.

26. 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 .

27. 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  

28. 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).

29. 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)

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

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

32. 2D Resistivity model near Tural hot spring (a) along L3 profile. (b) along L4 profile.

33. 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.  

34. 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.

35. 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.

36. 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: [email protected]) 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 .