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2. geology

Geological Field Excursion Guide
Hyderabad to Nagarjuna Sagar
(November 9, 2014)
FIERY ICE 2014
9th International Methane Hydrate R&D
(IMHRD) Workshop
Organized by
CSIR-National Geophysical Research Institute
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COMMITTEES
Fiery Ice International Steering Committee
• Richard B. Coffin,Department of Physical and Environmental
Sciences, Texas A&M University -Corpus Christi, USA
• Bjørn Kvamme,Department of Physics and Technology,
University of Bergen, Norway
• Stephen M. Masutani,Natural Energy Institute,University of
Hawaii, Honolulu, USA
• Hideo Narita,National Institute of Advanced Industrial Science
and Technology,Sapporo, Japan
• Tsutomu Uchida,Division of Applied Physics, Faculty of
Engineering, Hokkaido University, Japan
Local Advisory/Organizing Committee
• Prof. Harsh K. Gupta, Atomic Energy Regulatory Board (AERB),
Mumbai , Chair
• Dr. Shailesh Nayak, Ministry of Earth Sciences, New Delhi
• Shri B. N. Talukdar, Directorate General of Hydrocarbons, Noida
• Dr. S.K. Srivastava, Oil India Limited, Dhuliajan
• Dr. Y.J. Bhaskar Rao, CSIR-National Geophysical Research
Institute, Hyderabad
• Dr. S.W.A. Naqvi, Director, CSIR-National Institute of
Oceanography, Goa
• Dr. M.A. Atmanand, National Institute of Ocean Technology,
Chennai
• Dr. S. Rajan, National Centre for Antarctic & Ocean Research, Goa
• Dr. Pushpendra Kumar, Gas Hydrates KDM Institute of
Petroleum Exploration, ONGC, Dehradun
• Dr. Kalachand Sain, CSIR-National Geophysical Research
Institute, Hyderabad, Convener
Convener
Dr. Kalachand Sain
CSIR-National Geophysical Research Institute
Gas-hydrate Group, Uppal Road, Hyderabad - 500 007, India
E-mail: 14fieryice@gmail.com
Ph No. +91 040-2701 2799 (O) Mob: +91 9440964038
Website: http://www.fieryice2014.org/
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Background
The growing demand of energy and depletion of fossil fuels
necessitate looking for an alternate source for sustainable
development. Among various forms of renewable and
unconventional energy resources, gas hydrates seem to be the
major unconventional energy resource for the next generation
because of their abundant occurrences in nature. The energy
potential of gas hydrates is so huge that even 15% production
from global reserve can meet the world’s energy requirement
for about two hundred years. Successful production tests
through carbon dioxide replacement method in the permafrost
of Alaska (USA) in 2012 and by depressurization method in the
Nankai Trough off Japan in 2013 have increased tremendous
interests to the national gas hydrates programs of many
countries, particularly in the Asian countries. It is expected
that gas hydrates will be produced commercially by another
10 years times. The ’Fiery Ice’ International Methane Hydrates
R&D (IMHRD) Workshops were earlier held in Honolulu,
Hawaii; Washington DC; Vina del Mar, Chile; Victoria, British
Columbia; Edinburgh, Scotland; Bergen, Norway; Wellington,
New Zealand; and Sapporo, Japan. The 9th IMHRD Workshop
will be held in Hyderabad, India during November 9-12, 2014
that will provide a platform for deliberation, interaction and
sharing information on new advances of several perspectives
of gas hydrates. The leading edge topics covering the natural
systems, energy, environmental impacts, flow assurance,
advancement in production technology, etc will be presented
and discussed by an outstanding and diverse group of scientists
(academic and industries) from different countries, fostering
an opportunity for International collaboration.
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Structure of the Workshop
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1-day pre-workshop ‘Geologic Field Excursion’ on
November 9, 2014, as a part of the Workshop
Inaugural and Plenary sessions
2 Key-note presentations
10 National Reports on recent progress of gas hydrates
R&D in respective countries.
15 oral presentations on latest work of gas hydrates
25 posters on cutting-edge R&D on gas hydrates.
Theme-wise ‘break-out sessions’ spread during the
workshop
1-day Post-Workshop ‘Seminar on Indian Gas Hydrates’ or
‘Laboratory visit to NGRI’
Nagarjuna Sagar Field Excursion, Time Schedule
November 9, 2014
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07:00 hrs: 09:00 hrs: Departure: CSIR-NGRI guest House
Breakfast at the Geological field stop
no. 1
09:30 – 10.30 hrs Geological field Stop 2
12.00 hrs: Geological field Stop 3
13:00 – 14:00 hrs: Lunch at Vijaya Vihar Guest House,
APTDC
14.00 – 15.30 hrs: Visit to Cultural site
16:00 hrs: Geological field site stop no. 4
16:30 hrs: Evening Snacks
17:30 hrs: Tea at Devarakonda X’roads
20:00 hrs: Return to the Hotel
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Preface
One day geologic field excursion on November 9, 2014,
organized as a part of the 9th International Methane Hydrate
R&D (IMHRD) Workshop provides glimpse of the Archaean
greenstone belts, Precambrian granites and gneisses, and
Proterozoic sediments in the Eastern Dharwar Craton. The
participants also will visit one of the largest (masonry) irrigation
dams in Asia.
The geological excursion to Nagarjuna Sagar from Hyderabad
is planned exclusively for the delegates of IMHRD. The
objectives of this excursion are two fold: (1) offers glimpse of
the Precambrian geology of the Eastern Dharwar Craton and
(2) experience the environs of the Nagarjuna Sagar reservoir
- a major multipurpose irrigation project.
The following
pages present a brief introduction to the geologic setting and
a description of four interesting geologic outcrops (scheduled
stops) along the 150 km-long traverse.
November 9, 2014
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E.V.S.S.K. Babu
T. Vijaya Kumar
T.R.K. Chetty &
Kalachand Sain
Geological Field Excursion Guide
Hyderabad to Nagarjuna Sagar
(A late Archaean to Mesoproterozoic geologic cross section in
the Eastern Dharwar Craton)
Field traverse and the locations of the outcrops
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Regional Geology
Much of the Indian Peninsula is made-up of Precambrian
formations which include: Archean cratons, Proterozoic
mobile belts and Proterozoic supracrustal sedimentary basins
(Fig. 1). The southern part of the Indian shield is well known
as ‘Dharwar Craton’ (DC) which forms a large, well exposed
Precambrian-crustal segment. The northern part of the DC is
predominantly an Archean granite-greenstone terrain which is
divisible into western and eastern parts. Whilst the Western
Dharwar Craton (WDC) consists of middle to Late Archean
(~3.5-2.6 Ga) greenstone (or supracrustal) successions and
tonalite-trondhjemite-granodiorite (TTG) gneisses, the Eastern
Dharwar Craton (EDC) consists of Late Archean and Paleo- to
Neoproterozoic supracrustal sequences surrounded by a vast
Late Archean to Paleo-Proterozoic granite-gneiss basement
complex. The boundary between the WDC and the EDC
coincides broadly with the Closepet Granite (CG) outcrop.
The DC is surrounded by granulite facies gneiss terrains to the
south and to the east, which are well known as the Southern
Granulite Terrain (SGT) and the Eastern Ghat Granulite Terrain
(EGGT), respectively. Several Proterozoic sedimentary basins
are distributed in the northern and eastern parts of the DC, the
most prominent of which is the Cuddapah Basin (CB), which
contains a thick succession of sedimentary rocks grouped
into the Cuddapah Super group and the Kurnool group. The
DC is bound at its north-eastern margin by the Permo-Triassic
sedimentary basin along the Godavari Graben (GG) and overlain
by the Cretaceous Deccan basalts in the northwestern and
northern parts. The crystalline basement around Hyderabad
proximal to the large Proterozoic sedimentary basins is expected
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to preserve the imprint of a protracted and complex Post-Archean
geologic history involving granite magmatism, emplacement of
mafic dyke swarms and recurrent extensional / trans-tensional
deformation related to sedimentary basin formation and its
subsequent deformation. A major objective of this geologic
excursion is to provide a glimpse of the ground-manifestations of
these Neoarchean to Phanerozoic geologic processes reflected in
the architecture of the basement–cover rocks.
Figure 1. Geological map of India (after G.S.I.) showing the major tectonic units.
EGGT-Eastern Ghats Granulite Terrain, CB-Cuddapah Basin, CG-Clospet Granite,
WDC-Western Dharwar Craton, EDC-Eastern Dharwar Craton, SGT-Southern
Granulite Terrain. H-Hyderabad and N-Nagarjuna Sagar.
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The Hyderabad-Nagarjuna Sagar Traverse
The 150-km long traverse present three principal geologic units,
viz., the Hyderabad granites, the Peddavura schist belt and the
Kurnool group of sedimentary cover (Figs. 2 and 3).
Figure 2. Geological Map of Andhra PRadesh (after G.S.I.)
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Figure 3. Broad geological frame work of the EDC
showing different tectonic elements.
Hyderabad granites:
The city of Hyderabad is located in the northern part of the EDC
(Fig. 2). The rock exposure around Hyderabad consists of a variety
of Neoarchean / Paleoproterozoic (ca. 2.55 Ga) granite plutons.
These granites form typical landforms such as inselbergs, tors and
castle koppies etc., presenting a gently undulating terrain with
elevations ranging between 550 and 300 m (MSL). The granites
are predominantly calc-alkaline, K-rich types with both metaand per- aluminous variants. Petrological variation ranges from
granite to granodiorite to rare tonalite. These are generally coarse
grained, homophanous to megacrystic, but often show a feeble to
well developed foliation on closer examination.
The granites consist of a petrologically complex assemblage of
xenoliths showing different shapes, sizes and a wide variation in
the degree of migmatisation and / or assimilation by the granite
melt. Commonly, the xenoliths include meta-basic and ultra-mafic
rocks with predominant amphibole, biotite and epidote. They
show fabrics of deformation pre-dating granite emplacement
and have been generally considered to be vestiges of an older
greenstone-gneiss assemblage. These granites indicate variable
effects of brittle-ductile shearing, migmatization, epidotisation
and low temperature alteration processes.
On both mesoscopic and regional-scale, the terrain shows a
complex pattern of multiple shear zones and joints with definite
but variable orientations. Several of these are picked-up as
mega-lineaments. Also, mafic dyke swarms and reefs of quartzrich pegmatites are seen with different orientations. An aspect
relevant to the regional tectonic evolution is the distribution of
zones of high finite strain (fault zones / shear zones).
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The Peddavura schist belt (PSB) is a NW-SE trending narrow (1-2
km wide) linear belt extending for over 60 km from Juvvigudem in
the NW in Nalgonda district to Tummurukota in the SE in Guntur
district southern part of the traverse. The PSB can be visualized as
mega-xenoliths in the granite terrain, similar to numerous other
supracrustal traces of the EDC (Fig. 3). Its hook-shaped southerly
extensions are concealed partly by the Proterozoic cover sequence,
but spectacular windows of the PSB are exposed through the
sedimentary cover near Nagarjuna Sagar (Figs. 4 and 5).
Fig. 4. Geological sketch map of the Peddavuru schist belt (modified after G.S.I.)
Fig. 5 Simplified geological map showing the distribution of the granites,
migmatites and schist belts around Nagarjuna Sagar (modified after G.S.I.)
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Proterozoic cover sequence
The southern section of the traverse around Nagarjuna Sagar
comprises Proterozoic sedimentary cover sequences pertaining to
the Kurnool group of rocks (ca. 0.6 Ga). Principally these include
shale-quartzite sequence with striking horizontal bedding. These
rocks form the northern limit of the well known Cuddapah
Basin, where the depositional ages range from ~ 1.9 to ~ 0.5 Ga.
The salient features of three geological units described in the
foregoing can be observed along the Hyderabad-Nagarjuna Sagar
traverse at specific locations.
FIELD EXCURSION
November 9, 2014 (Sunday): Departure (06.00 hrs) from CSIRNGRI (Guest House)
Stop 1 – 36 km from Hyderabad (17° 08′42″ - 78° 40′16″)
These rocks are medium to coarse grained granites of Neoarchean
age with poorly developed foliations. The rocks are traversed by
thin and narrow pegmatites and quartz veins. The general foliation
trends NW-SE, and is consistent with the general structural grain
of the East Dharwar craton. There are both grey and pink variety
of granitoids. There are a few cm to metre scale enclaves of
preexisting mafic rocks. A variety of brittle-ductile shear zones
occur with variable thickness from a few cms to more than a
metre and the strike length extends upto nearly 10 metres. They
are oriented in different directions: NW-SE, N-S, NNE-SSW, NESW and near east-west. The NW-SE trending shear zones exhibit
sinistral displacements and they seem to be the earliest shear
zones developed in the terrain. This shear zone is also displaced
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by a narrow shear zone trending NNE-SSW in dextral fashion with
a displacement of ~ 60cms.The other shear zones show both
sinistral and dextral kinematic sense of movements. Some of
the shear zones are emplaced by very coarse grained pegmatites
which are free from deformation. The mylonitic foliation is well
developed adjacent to some of the shear zones. The youngest
shear zones seem to be defined in the form of a network of
epidote veins. Detailed structural studies are essential to relate
these shear zones with the regional tectonics and to understand
the emplacement and tectonics of granites around Hyderabad.
Archean Mafic enclave surrounded by Neoarchean granite
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Ductile Shear zone (~50 cm wide) within Granite
Shear zones and pegmatites associated with mylonitic foliation in the granites.
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Stop 2 ~ 50 km from Hyderabad (16° 55′13″ - 78° 40′15″)
This is well exposed, typical high temperature migmatite outcrop
from the east Dharwar craton. The important rock types are grey
granite and pink granites intruded by subvertical as well as dipping
pink feldspar pegmatites. These pegamites are cm to metre scale
in width. Enclaves of comagmatic as well as preexisting relict
greenstone belts are abundant in the outcrop. Many enclaves
of granodiorite / tonalite gneiss and amphibolite-gneiss occur
in this outcrop displaying gently dipping foliations. The enclaves
are variably digested and randomly oriented. Neosomes of
hybrid rocks wrap around the enclaves. Earlier deformational
events are well preserved in some of the xenoliths. A range of
mesoscopic shear zones showing different displacement patterns
are common. At a few places, the leucosome melt products
exhibit flow structures. Pegmatites are often displaced by shear
zones with a displacement by about a metre. There are also mafic
dykes in the form of ridges nearby traversing the region. These
migmatites could be a part of NW-SE trending major sinistral shear
zone, which constitutes the migmatized extensions of Peddavura
schist belt (Fig. 5). The host granite represents pervasive granite
event in the region but the other phases of granite can be
observed elsewhere in the region.
Enclaves of relict Archean Greenstone belt within the migmatitic gneiss
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High temperature migmatites with caught-up patches of xenoliths and Mafic Comagmatic enclaves.
Stop 3: 120 km from Hyderabad; Peddavura schist belt (16°
41′51″ - 78° 56′38″)
The well exposed east-west section of Peddavura schist
belt (PSB), adjacent to the road, trending NW-SE with steep dips
to west. The PSB extends for over 60 km along strike and the
width varies from 0.5 km to 2 km. The lithological units of the
schist belt are metavolcanics, predominantly metabasalts with
subordinate acid to intermediate varieties, banded iron formation
and metamorphosed plutonic rocks of homblende-gabbro
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and homblendite. All the litho-units of the belt exhibit intense
foliations / schistosity throughout its length. The dominant
lithologies of the PSB, at this exposure, include schistose
amphibolites and chlorite schist with minor fine-grained felsic
schist (felsic volcanics?). Along the axial part of the belt, coarsegrained porphyritic gabbro is exposed and shows variable effects
of strain resulting, in extreme case, in amphibolite with intense
penetrative fabrics. Also pillowed meta-basalts have also been
preserved. Elsewhere, iron formations (mainly banded magnetite
quartzite) and quartzites are also known to occur within the PSB.
Deformed pillow structures within the ampibolites and bimodal volcanics
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A noticeable feature is the highly strained nature of rocks both
of the schist belt and the adjacent granite-gneiss units, which is
best observed further north along a stream bed. The gneisses
developed very strong mylonitic fabrics and include a variety of
inclusions all of which showing extreme stretching with aspects
ratios typically exceeding 10. Also seen, is a network of leucosomes
(melt products) criss-crossing the rocks. Away from this high-strain
zone, one can observe better preserved gneisses and granites of
multiple generations. However, granodiorite-tonalite gneiss with
abundant amphibole-rich inclusions of different sizes (up to 0.5 m
diameter) is exposed to the east of the belt.
Arrival at Nagarjuna Sagar – (13.00 – 14.00 hrs.) and LUNCH
Vijaya Vihar Tourist Complex, Nagarjuna Sagar.
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About Nagarjuna Sagar
A dream destination for perfect relaxation, Nagarjuna Sagar is a
massive irrigation project on River Krishna about 150 km from
Hyderabad. The region has a rich and interesting past. It was
a valley with civilizations dating back to thousands of years.
Archeologists assert that the fertile Krishna valley hummed with
life in the third millennium BC. The tallest masonry dam in the
world, Nagarjuna Sagar, was constructed here, standing 124 m
high, and creating the largest man made lake. Pandit Jawaharlal
Nehru called Nagarjuna Sagar a “Temple of Modern India”.
Nagarjuna Sagar Dam and the Power House
The valley was the site of an ancient Buddhist civilization and
is named after the Buddhist saint Acharya Nagarjuna. It is
considered as one of the most beautiful tourist destinations in
Andhra Pradesh
Stop 4 – 3 km to Nagarjuna Sagar; Basement - cover sequence
Further, along the road to the south, the granite–greenstone
association of the basement traversed by mafic dyke and quartz
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reef can be seen overlain by flat lying quartzites and shales of
Kurnool group (Neoproterozoic), at the down stream of Krishna
River. Un-conformity contact of the Archean basement and the
Cuddapah sedimentary rocks
Unconformity contact between Archaean basement and Neoproterozoic Kurnool
sediments.
On the other end, exposure of the Archean basement with BIF,
amphibolite-granite with steep foliation dips are surrounded
by the overlying sub-horizontal Kurnool group of sediments are
observed further south near Ethipothala.. More information
about the fold structure of the basement underlying the cover
sequence as revealed in aeromagnetic data, facilitated by BIF’s
as markers has been described in some detail in a publication by
Rama Rao et al. (1991).
Return Departure from Nagarjuna Sagar Dam around 16.00 hrs
Arrival Around CSIR-NGRI at 20.00 hrs.
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Further reading
1. Nagaraja Rao, B.K., Rajurkar, S.T., Ramalingaswamy, G.,
Ravindra Babu, B. (1987). Stratigraphy, structure and evolution
of the Cuddapah basin. Memoir of Geological Society of India
6, 33-86.
2. Naqvi, S.M., Rogers, J.J.W. (1987). Precambrian geology of India.
Oxford University Press, 223 p.
3. Radhakrishna, B.P. (1983). Archean granite-greenstone terrain
of the south Indian shield. In: S.M. Naqvi and J.J.W. Rogers (Eds.).
Precambrian of South India. Memoir 4, Geological Society of
India, 1-46.
4. Ramam, P.K., Murthy, V.N. (1997). Geology of Andhra Pradesh.
Geological Society of India, Bangalore, 145 p.
5. Ramarao, Ch.,Chetty,T.R.K., Lingaiah, A., Babu Rao,V. (1991).
Delineation of a greenstone belt using aeromagnetics, Landsat
and Photogeology- A case study from the South Indian shield.
Geoexploration, 28, 121-137.
6. Sarvothaman, A., Leelanandam, C. (1992). Peraluninous,
metaaluninous and alkaline granites from parts of Andhra
Pradesh and Karnataka in Dharwar Craton: A Critical reappraisal
of existing data. Journal of Geological Society of India 39, 287291.
7. Chandrasekhar, K., Charyulu, D.N. (2000). Specialised Thematic
Mapping of Peddavuru Schist Belt and the Surrounding PGC
Terrain, Nalgonda and Guntur Districts. Records Geological
Survey of India 134, Pt-5, 11-14.
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FIERY ICE 2014
HYDERABAD - INDIA
Workshop Secretariat:
FIERY ICE - 2014
CONFERENCE SECRETARIAT
CSIR_National Geophysical Research Institute
Gas-hydrate Group,
Uppal Road, Hyderabad - 500 007, India
E-mail: 14fieryice@gmail.com