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Journal of Geosciences, Osaka City UniversityVol. 43, Art. 8, p. 149-163, March, 2000
Geological Fieldwork in the Aravalli and Delhi beltsin Rajasthan, India, 1999
KANO Takashi 1, BABA Sotaro 2, Buu, S.S.2, BISWAL, T.K.3,
CHAUHAN, N.K.4, ETO Takuro I, GYANI, K.C. 4
, JENA, S.K.3,
PANDIT, M.K.5, WADA Hideki 6 and YOSHIDA Masaru2
1 Department of Earth Sciences, Yamaguchi University, Yamaguchi 753-8512, Japan
2 Department of Geosciences, Faculty of Science, Osaka City University, Osaka 558-8585, Japan
3 Department of Earth Science, Indian Institute of Technology, Mumbai 400076, India
4 Department of Geology, M.L.Sukhadia University, Udaipur 313002, India
5 Department of Geology, University of Rajasthan, Jaipur 302004, India
6 Department of Earth Sciences, Shizuoka University, Shizuoka 420-8529, Japan
AbstractField observations in the Aravalli and Delhi belts in Rajasthan were conducted from January 5 th to 14 th 1999,
by a Japanese and Indian joint project team. The observations were focussed on the stratigraphic succession of the
early to middle Proterozoic Aravalli and Delhi belts, in order to obtain the general view on the geology of the
AravalJi Mountains. Attention was also payed to the Archaean basement (the Banded gneiss complex) including
granulite, charnockite and migmatite, as well as on the several intrusive granites in the belts. Important questions
pointed out during the field work, such as the sedimentary facies of the AravaIli and Delhi rocks, age determinations
of certain granitic bodies, and petrological investigations on migmatite, are summarized for future studies.
Key words: India, Aravalli belt, Delhi belt, Banded Gneiss Complex, Rajasthan
Introduction
The Aravalli and Delhi belts occupy the important part
of the Precambrian cratonic area in the northwestern Indian
subcontinent. The field work in the belts was planned by
Yoshida, an author of this paper, as a part of his long term
project on "Study of the Proterozoic events in East Gond
wana" (UNESCO-lUGS IGCP-368 project). The
observations were focussed on the early to middle
Proterozoic stratigraphic successions of the Aravalli and
Delhi belts, along with the major theme of the project. This
is also the first step on the research project entitled
"Tectonics of the Central India Tectonic Zone", which is
financially supported by the Grant-in-Aid for International
Scientific Research Program of the MONBUSHO (Ministryof Education, Science, Sports and Culture of Japan, No.
10041123).The field work started at January 5 th in Udaipur, and
ended in Delhi at January 14 th, covering the areas from
southern Rajasthan around Udaipur to central and northeastRajasthan around Jaipur (Figs. 1 and 2, Table 1). The field
survey was successful and a general view and understand
ing of the geology of the belts was obtained. Collections oftype rocks were also made. Detailed studies, however,
remain for the future, doing with problems of the petrology,
structural geology and, particularly, on the geochronology.
This paper summarizes the outline of geology of these
areas and describes the modes of occurrence, field
relationships and characteristic features of rock types at
each observed outcrop with some suggestions for future
problems of study. The descriptions refer to the guide
books by collaborators of the project (Gyani and Chauhan,
1999 ; Pandit, 1999), and also refer to personal
communications from them during the field work.
Outline of Geology of the Aravalli Mountainsin Rajasthan
The basement rocks of the Aravalli Mountains inRajasthan are made up of three major geologic
components: the Archaean Banded Gneiss Complex
(BGC), the Aravalli belt, consisting of the early Proterozoic
150 Geological Fieldwork in the ravalli and Delhi belt in Raja than, India, 1999
• DELHI
Delhi •• UDAIPUR
CALCUTTA •
BOMBAY
MADRAS
~/J 9(7' I ~
•..~~
8 U~(I
ert'~~4~~~Uf
.~o \ £3
~~ qI »' fJ
...0 ~jodhPur j p 4~.
9 ~~~~cP
~
Q:)
§-•[ill[]
[IIJ~~-
ALLUVIUM AND SAND (OVER
DECCAN TRAP
VINDHYAN SUPERGROUP
MALANl IGNEOUS SUITE
ERINPURA GRAN ITE
CHAMPANER GROUP
SIROHI GROUP
DELHI SUPERGROUP
UNCLASSIFIED PRE DELHI ROCKS(SCANTILY EXPOSED)
ARAVALLI SUPERGROUP
MEWAR GNEISS
100 ~m
Fig. 1. Geological map of the Aravalli Mountain , Rajasthan (After Roy, 1988). SDFBDelhi Fold Belt
South Delhi Fold Belt, NDFB orth
KANO Takashi et al. 151
+27" N77' E
+28' N
77" E
eRajgarth
8-68-7
DELHI7'
8-48-5
8-1 8-28-3
+76' E
9-6
-24' N
28' N +75'
25' N +75' E
27" N +75' E
5-45-5
+25' N
3-4
74' E
3-5
6-1
6-2 ----'
26' N 6-3 ----'/
6-4 ------'6-5 J
2-10
2-6
2-2
Fig. 2. Locations of observed outcrops during field survey, 1999.
Aravalli Supergroup (2500 - 2000 Ma), and the Delhi belt,
composed of the middle to late Proterozoic Delhi
Supergroup (2000 - 1500 Ma)(Gyani and Chauhan, 1999)
(Fig. 3). The Supergroups are intruded by several granitic
rocks with different geologic ages, ranging from early to
late Proterozoic, and contain many lead and zinc deposits
associated with carbonate rocks. Further, this area is the
famous marble product centre of India.
Banded Gneiss Complex (BGC)The BGC consists mainly of granItIc gneisses,
migmatites, high-grade schists, metavolcanics (metabasalt)
152 Geological Fieldwork in the Aravalli and Delhi belts in Rajasthan, India, 1999
Table I. Diary of Field Survey and Observed Outcrops.
Day I (Jan. 5)
Route
Objectives
Loc.l-l
Loc.I-2
Loc.J-3
Loc.I-4
Loc.I-5
Loc.I-6
Day 2 (Jan. 6)
Route
Objectives
Loc.2-1
Loc.2-2
Loc.2-3
Loc.2-4
Loc.2-5
Loc.2-6
Loc.2-7
Loc.2-8
Loc.2-9
Loc.2-10
UDAIPUR ~ DEBARI
Basement-Aravalli contact, Lithology from the base to lower part of the Aravalli rocks of the Delwara formation(F)
Basement (BGC) - Aravalli contact [TULSI NAMLA]
Debari conglomerate and quartzite [3 km N, DEBARI]
Basal metabasalt (Delwara F)
Quartzite (Delwara F)
Banded Gneiss (BGC) [7 km stone to JHARKOTRA]
Carbonaceous shale [PRATAPNAGAR]
UDAIPUR ~ ISWAL ~ GOGUNDA ~ SAERA ~ RANAKPUR
Upper part of Aravalli to Delhi Supergroup (SG), Intrusive rocks in Delhi SG
Sheared granite with intercalation of greenschist (BGC)[near KABITA]
Pisolitic laterite between Raialo group (G) and Delhi SG [ISWAL]
Alternation of phyllite and quartzose sandstone (Turbiditic facies in Jharol G= upper Aravalli SG) [5 km NW, ISWAL]
Mica phyllite in Jharol G [7 km NW, ISWAL]
Ultramafic rocks and chert in mica phyllite [near Loc.2-4]
Leucogranite intrusion in Delhi quartzite [near GOGUNDA]
Calc-silicate of Delhi SG and grey pegmatitic granite vein[22 km NW, GOGUNDA]
Granite in Padrara (=Erinpura granite) [3 km from Loc.2-7]
Rapakivi granite with mafic rocks [20 km NW, SAERA]
Ultramafic rocks in Delhi SG [RANAKPUR valley]
Day 3 (Jan. 7)
Route UDAIPUR ~ RlKHABDE ~ KHAIRWARA ~ DUNGARPUR
Objectives Ultramafic rocks in Aravalli SG and talc mine
Loc.3-1 Serpentinite, talc schist [RIKHABDE, 60 km S, UDAIPUR]
Loc.3-2 Serpentinite - Aravalli contact [MANDWA, near loc.l]
Loc.3-3 Dhelana serpentinite mine [5 km NE, KHAIRWARA]
Loc.3-4 Calc-silicate rocks in Aravalli SG [ near Loc. 3-3]
Loc.3-S Khandmin talc mine [4 km N DEVAL]
Day 4 (Jan. 8)
Route UDAIPUR --+ DEVGARH --+ SANDMATA -. KARERA --+ BHIM --+ BEAWAR
Objectives Gneiss - granulite terrain in Central Rjasthan
Loc.4-l Ultramafic rocks on Delhi - BGC boundary [DEVGARH]
Loc.4-2 Anjana granitic gneiss (augen gneiss) [10 km E, DEVGARH]
Loc.4-3 Mafic granulite - gneiss [SANDMATA]
Loc.4-4 Metapelite (gar-bio gn.) and norite body [SANDMATA hill]
Loc.4-S Charnockite [GYANGARH, 13 km SE, BHIM]
Day 5 (Jan. 9)
Route BEAWAR ~ MASUDA ~ BANDANWARA ~ BHINAI ~ BIJAYANAGAR
Objectives Granulite - migmatite terrain in Central Rjasthan
Loc.5-1 Cha..mockite, augen gneiss [BANDANWARA]
Loc.S-2 Augen gneiss, granulite, loddy migmatite [BANDANWARA]
Loc.S-3 Bhinai gneiss - migmatite [BHINAI]
Loc.S-4 Basic granulite [BHINAI]
Loc.S-5 Grey gneiss [SUKRANI]
Day 6 (Jan. 10)
Route BEAWAR ~ BAR ~ SENDRA
Objectives Bar - Sendra section of SDFB in Central Rjasthan
Loc.6-1 Western granite (BGC 7) [20 km W, BEAWAR]
Loc.6-2 Mica schist, Barr conglomerate, calc-silicate schist, greenschist (Barotiya G in SDFB) [near Loc.6-1]
Loc.6-3 Sendra granite [16 km W, BEAWAR]
Loc.6-4 Margin of Sendra granite and schist [10 km W, BEAWAR]
Loc.6-S Porphyritic Sendra granite [9 km W, BEAWAR]
KANO Takashi et al.
Table 1. (continued).
Day 7 (Jan. I I)
Route BEAWAR ---+ JAIPUR
Objectives Move from Beawar to Jaipur, post Aravalli intrusion
Loc.7-1 Nepheline syenite (gneissic, post Aravalii intrusion)
Day 8 (Jan. 12)
Route JAYPUR ---+ AJABGARH ---+ SARISKA (TIGER DEN)
Objectives Lower succession of NDFB in Alwar basin
Loc.8-1 Quartzite with ripple mark in Alwar G
Loc.8-2 Basement granite, lowennost Raialo quartzite, limestone
[SAND KOTRA]
Loc.8-3 Marble quarry (Raialo siliceous marble)
Loc.8-4 Serrate quartzite (Raialo G) [TEHRA]
Loc.8-5 Metavolcanics (uppennost Raialo G) [TEHRA]
Loc.8-6 Thick boulder conglomerate of Alwar G[SARISKA sanctuary]
Loc.8-7 Metavoicanics (uppennost Raialo G) [near Loc. 8-6]
Day 9 (Jan. 13)
Route TIGER DEN ---+ THANAGAZI ---+ BAIRATH BAHROR
Objectives Upper succession of Alwar basin and granite intrusions
Loc.9-1 Alternation of pelitic and caicareous bands of Kushalgarh F [KUSHARGARH]
Loc.9-2 Black schist (carbonaceous shale), metadiabase [THANAGAZI]
Loc.9-3 Basal Raialo conglomerate - Bairath granite boundary[MEENON KI DHANI]
Loc.9-4 Bairath granite, quartzite boundary [BAJRATH]
Loc.9-5 Metavolcanics of Raialo G
Loc.9-6 Ajitgarh granite [AJITGARH]
Day 10 (Jan. 14)
Route BAHROR ---+ NEW DELHI
153
and some granulite facies rocks. The BGC forms the
basement complex under the Proterozoic Aravalli and Delhi
Supergroups, and the granitic assemblages are comparable
to the Peninsular Gneisses (TTG) in the Dharwar craton of
South India. The BGC rocks are exposed mainly on the
eastern side of the Aravalli mountains, and granulite and
charnockite have limitted outcrops in central Rajasthan.
The radiometric ages of the BGC range from a 3310 Ma
Sm-Nd age in biotite gneiss, through 2900 Ma in granitic
rocks, to 2500 Ma in K-feldspar rich granites (Pandit, 1999).
Aravalli SupergroupThe Aravalli Supergroup, unconformably overlying
the BGC rocks, is composed mainly of clastic sedimentssuch as quartzite, grit (arkosic sandstone), conglomerate
and shale, dolomite and limestone, with intercalations of
metabasaltic rocks. The rocks are mostly folded and
metamorphosed into low- to medium-grade slate, phylliteand schist, and constitute the Aravalli Fold Belt (AFB).
The Aravalli Supergroup is divided into three parts in thetype area; the lower part (Delwara group), the middle part
(Debari group) and the upper part (Jharol group) (Fig.3).
The lower and middle parts are mostly shelf facies,including basic lava and coarse-grained clastics; on the
other hand, the upper part is assumed to be a deep-sea
facies. The upper part includes turbiditic facies, and is
often associated with serpentinized ultramafic bodies
(mined as so-called "green marble", talc and soapstone
deposits). The radiometric ages of the basement granites
(2500 Ma) and the synkinematic Darwal granite (l900±80
Ma) restrict the range of the formation and metamorphism
of the Aravalli Supergroup (Gyani and Chauhan, 1999).
Delhi SupergroupThe middle to upper Proterozoic Delhi Supergroup
consists mainly of dolomitic limestone, quartzite, arkosic
sandstone, shale, conglomerate and metabasaltic rocks.
The' Supergroup, however, is not a simple cratonic cover
sequence, but the rocks are mostly deformed and
metamorphosed into low- to medium-grade, and named the
Delhi Fold Belt (DFB). The DFB occurs in two belts; the
North Delhi Fold Belt (NDFB) and South Delhi Fold Belt(SDFB), separated by gneisses around Ajmer and young
cover sediments. The NDFB is exposed in northeastRajasthan, and subdivided into the Raialo, Alwar and
Ajabgarh groups (Fig.3). The SDFB is developed from
Ajmer in central Rajasthan to northern Gujarat along withthe NE trend of the Aravalli Mountains, and consits of the
154 Geological Fieldwork in the Aravalli and Delhi belts in Rajasthan, India, 1999
u S D F B N D F B ++++/ (++ ++ ~'0N
Kumbhalgarh. G. Ajabgarh. G. + + + +0La>
Delhi Supergroup etc 0 (.....Gogunda. G. l+~ Syenite0 (2.0"-' 1.5Ga'"") Sendra gr.L Alwar. G. (l.4Ga)a.. (0.9'""0.8Ga)
a> Padrara gr.=01J Raialo G. Raialo G.~
u +
~'0 Upper (Jharol. G.) + +N0 + +La>..... Aravalli Supergroup Middle (Debari. G.)0 (2.5"-' 2.0Ga) Darwal gr.La.. (2.0"-'1.9Ga)
>. Lower (Delwara. G.)"'Cro
LJJ
+ +~ (\ +Banded Gneiss Complex Mewar gneiss + +c (B G C) + +roa> (3.3'""2.5Ga) + +ro Untala gr....cu Gingla gr.L Berach gr.« (2.9Ga)
(2.6"-'2.5Ga)
Fig. 3. Stratigraphic framework and major geologic units of the Aravalli Mountains.SDFB : South Delhi Fold Belt, NDFB : North Delhi Fold Belt. Isotopic ages refer toGyani and Chauhan(1999), Pandit(1999) and personal communications from Gyani andPandit.
11. Delhi Supergroup
Upper 10. Ultramafic intrusion
Oharol G.) 9. ]harol F.
8. Tidi F.
- - -
7. Machhlamagra F.- - - -
~6. Zawar F.
- - - -Middle 5. Debari F.
(Debari G.)
- - - -U)
....... 4. Udaipur F........~> - - - -ro.....
<C3. ]hamarkotra F.
Lower 2. Delwara F.(Delwara G.)
1. Banded Gneiss Complex
serpentinite. talc schistmica schist, phyllite withquartzite(deep sea sequence)
(slaty phyllite with dolomite
_qu~tzi~ _
quartzite, quartz phyllite
(dolomite. carbonaceous phyllit~
quartzite, Pb-Zn Ore /
8. quartzite with phylliteA. conglomerate-arkose s.s.
(
greywacke-PhYlhte)lithic areniteconglomerate
D. argillaceous phylliteC. carbonaceoLls phyllite8. dolomite, phosphoriteA. quartite
C. carbonate.r.B. qurtzite/conglomerateA. metabasalt
Mewar gneiss..
Fig. 4. Stratigraphic succession of the AravalliSupergroup around Udaipor.Nos. 1 - 10 with A - D are corresponding to thegeologic units in Fig. 5 (Modified after Roy etal., 1988).
Gogunda and Kumbhalgarh groups (Fig.3). The geological
position of the DFB and the relationship between Aravalliand Delihi rocks have been much controver ial. For
example, there were several arguments about the
stratigraphic pOSItIOn of the Raialo group, whether it
belonged to the uppermost Aravallis or the lower part of theDelhis. In Fig. 3, we assumed the Raialo to be the lower
part of the NDFB according to the recent general view on it
{9 ~8 rn~\' :-:.:".
7 Cd6 ~
rij s[:~2 B _0:::;:;· ,
ESJo c 11A-, -. o 0
~ 4 ~ 10 00
10 km
KANO Takashi et al. 155
Fig. 5. Geological map around Udaipur (After Roy et aJ., 1988).1 : Banded gneiss complex, 2: Delwara formation (F) [A: metabasalt, B: quartzite/conglomerate, C: Carbonate rock], 3:Jhamarkotra F [A : quartzite, B : dolomite/phosphorite, C: carbonaceous phyllite, D : argillaceous phyllite], 4: Udaipur F, 5 :Debari F [A : conglomerate-arkose S.S., B : quartzite with phyllite], 6 : Zawar F, 7 : Machhlamagra F, 8 : Tidi F, 9 : Jharol F, 10 :
Ultramafic intrusion, 11 : Delhi Supergroup.Nos. I-I to 2-5 : locality number in Table 1, I: Iswal, KB: Kabita, DB: Debari, JR: Jharol, RSZ: Rikhbde Suture Zone,
KL: Kaligman Lineament..
156 Geological Fieldwork in the Aravalli and Delhi belts in Rajasthan, India, 1999
(Gyani and Chauhan, 1999; Pandit, 1999).
Field Survey in Southern Rajasthanaround Udaipur
The field survey in southern Rajasthan was conducted
around Udaipur by Dr. Gyani, an author of this paper,
during the period of Day 1 to Day 3 (Fig. 2, Table 1). The
area provides typical examples of the basement-Aravalli
contact and cross sections of the Aravalli Supergroup and
Delhi Supergroup in SDFB, with several plutonic bodies
within them (Figs. 4 and 5).
Banded Gneiss Complex (BGC)The BGC rocks in southern Rajasthan are generally
called the Mewar gneiss. The typical BGC is observed at 5
krn south of Debari [Loc.l-5 in Table 1 and Fig.5], where
the BGC forms a small dome elongated in the N-S direction
on the geological map. The rocks are well banded in
leucocratic and melanocratic layers, with typical gneissic
texture, and are tonalitic to trondhjemitic and/or
granodioritic in compositiOn (Plate 1-1). These
appearances are similar to those of the TTG in Peninsular
Gneisses. In part [Loc.2-1], the BGC has intercalations of
thin bands of greenschist, and is highly sheared and chlori
tized along fractures, where chlorite - epidote assemblage is
common, suggesting retrograde metamorphism.
Basement-Aravalli ContactThe weathered leucocratic tonalic rock belonging to
the BGC is in contact with mica schists, with a tectonic
boundary of 0.5 to 1 m in width [Loc.l-l](Plate 1-2). From
the boundary to several tens of meters into the Aravalli
rocks, the following lithological change was observed:
highly aluminous schist (pyrophyllite schist), 1-2 m in
thickness, mica schist, greenschist, quartzite and quartzite
conglomerate. The pyrophyllite band is assumed to be a
metamorphosed palaeosole in origin, forming a good
marker of the basement-Aravani contact. The band is often
mined along the contact.
Aravalli SupergroupThe Aravalli Supergroup, exposed around the Udaipur
area, is divided into three groups: the lower Delwara,
consisting of one formation, the middle Debari of sixformations, and the upper Jharol of two formations (Roy et
aI., 1988). The stratigraphic succession of the Supergroupin the area is summarized in Fig. 4.
The lower part of the Aravalli rocks designated as theDelwara group consits of metabasalt [Loc.I-3], quartzite[Loc.I-4], conglomerate and carbonate rocks (Fig. 4). The
metabasalt occupies the lowermost part of the sequence,
and has amygdaloidal structure, but pillow structure is not
clear.
The Debari group is characterized by thick quartzite
and conglomerate, including highly flattened pebbles
[Loc.1-2] (Plate 1-3). The conglomerate is dominantly
quartzose both in pebbles and matrix, but often includes
granite, amphibolite and mica schist. The quartzite bed in
a part of the group has well preserved cross lamination
(Plate 1-4). Carbonaceous shale [Lac. 1-6] is characteristic
of the middle part.The upper part (Jharol group), on the other hand, is
dominated by alternations of shale and sandstone (turbidite
in origin ?), and are metamorphosed into phyllite to mica
schist, including sporadic garnet [Loc.2-3, 2-4] (Plate 2-1).
At localities 2-4 and 2-5, we found an intercalation of chert,
manganese ore, metabasalt and ultramafic rocks in the ma
trix of mica phyllite - schist (Plate 2-2). This lithological
assemblage is similar to that of a Phanerozoic ophiolitic
sequence.
Ultramafic Rocks in the Aravalli SupergroupUltramafic rocks often occur in the Aravalli rocks,
most commonly associated with the Jharol group, but are
scarce in the SDFB, except at Ranakpur [Loc.2-1O] and
Devgarh [LocA-1]. The rocks are exposed in linear
arrangements along the Rikhbde suture zone and the
Kaligman Lineament, with a nearly N-S trend. The rocks
are totally serpentinized and/or metamorphosed into talc
schist and chlorite schist in the outer shell of an ultramafic
body, hence, the originallitholog'y could not be determined.
These serpentinite bodies are often mined as "green mar
ble" , talc, asbestos and soapstone around Rikhabde [Loc.3
1, 3-2, 3-3]. The Khandmin talc mine near Dungarpur
[Loc.3-5] represents a good example of the tectonic
intrusion of serpentinites, where a mushroom shaped
serpentinite body intrudes into the surrounding rocks, with
partly concordant and partly discordant boundaries (Plate 2
3) .
Another kind of ultramafic rock is amphibolite, which
occurs in small lenticular blocks within the Jharol group[Loc.2-5], but is not common rock type in the area.
Delhi Supergroup in SDFBThe stratigraphic succession of the SDFB is
summarized in Fig. 6 A. We observed quartzite [Loc.2-6]
and calc-silicate rocks [Loc.2-7] belonging to the Gogundagroup in the lower part of the SDFB in northwest Udaipur.
The observed outcrops are intruded by granitic rocks andmetamorphosed into schist or gneiss, with more or lesshomfelsic texture.
Subdivision
Sirohi/Ras/Punagarh G.
Lithology
mica schist, marble,basic volcanics
KANa Takashi et aL
Lithological succession of the Bar - Sendra section in SDFB
(Day 6, Loc. 1, 2)
15. Sendra granite
157
Fig. 6A. Stratigraphic succession of the South Delhi Fold Belt(SDFB) around Udaipur (After Roy et aI., 1988).
Sendra G. 1___________+-__ (see Fig. 6B)
Barotiya G.
1. Western granite -_ -._._._........ (6-1)
Bhim G.
Rajgarh G.
Gogunda G.~
Aravaili Supergroup
pelitic, semi-pelitic schist,calc-silicate, marble
pelitic schist with quartzite
quartzite
Banded gneiss compiex
14. Biotite schist with metabasics13. Calc-silicate rock with metabasics12. Micaceous schistose quartzite11. Nanana marble and calc-silicate rock
10. Schistose quartzite9. Calc-gneiss8. Biotite schist with pegmatite7. Calc-gneiss6. Biotite quartzite (feldspar spotted)5. Calc-silicate rock4. Biotite quartz schist3. Bar conglomerate2. Biotite quartz schist
r(6-2)
t
Sendra G.
Barotiya G.
Granitic Intrusions in SDFBThe SDFB is intruded by several granitic rocks along
the route from Udaipur to Ranakpur. A leucogranite intrude
into the quartzite formation of the Gogunda group, forming
several veinlets and dykes, including angular blocks of
quartzite [Loc.2-6]. The rocks are leucocratic muscovite
granite associated with tourmaline-bearing pegmatite, The
granite has been assumed to be synkinematic, but the
massive appearance and dyke-form are indicative of a late
or post-kinematic nature. A grey pegmatitic granite and
pink aplite also intrude into calc-silicate rocks as
concordant veins along the banding of the host rocks [Loc.2
-7].
The Padrara granite [Loc.2-8] has wider exposures
than the former two, around Padrara village. The outcrop
consists of pink to red granitic rocks and strongly foliated
tonalitic and granodioritic rocks with a fairly pink colour.
The granites are considered to be correlated with the late
Proterozoic Erinpura granite, but no geochronolgy has been
done in this area.
The Elephant bridge granite (a temporary name) has a
good outcrop along the gorge under the Elephant bridge
[Loc.2-9]. The granite is porphyritic and foliated, and
characterized by a distinct rapakivi texture (Plate 2-4). The
outcrop is composed mainly of porphyritic granite and
coarse- to fine-grained dioritic rocks including ocellar
quartz grains. However, it is quite heterogeneous inlithology, and is associated with many varieties showing a
gradation between felsic and mafic rocks. The Padrara andElephant bridge granites are both foliated and have a syn
or pre-kinematic nature, but their isotopic ages still remain
unknown.
Fig. 6B. Lithology of the Bar - Sendra section in SDFB (6-1, 62 : locality number in Table 1) (After Pandit, 1999).
Field Survey in Central Rajasthanaround Beawar
The field survey in central Rajasthan took place along
the Udaipur to Beawar route and around Beawar during the
period of Day 4 to Day 7 (Fig.2, Table 1). This area
provides the granulite - chamockite association within the
BGC (the gneiss - granulite - migmatite terrain in central
Rajasthan), whose typical outcrops were guided by Dr.
Gyani. The area also includes a continuous stratigraphic
section of the SDFB (Bar - Sendra section), which were
shown by Dr. Pandit.
Gneiss - Granulite - Migmatite TerrainThe area around Bhim to Beawar forms the distinct
gneiss - granulite - migmatite terrain in the BGC, the
basement of the Aravalli mountains. These rock types
occur in close association in outcrops, and charnockitic
rocks are also found within them. Several
geothermometries on two- pyroxene granulites in the area
show more than 850° to 900°C at 8 kb in maximum
temperature (Gyani and Chauhan, 1999).
The Anjana augen gneiss [Loc.4-2] is a characteristic
granitic gneiss, and has large K-feldspar porphyroblasts of
augen shape, more than 10 cm in maximum size (Plate 3-1).
Augen gneisses are also exposed around Bandanwara
closely associate with charnockite and with migmatiticrocks [Loc.5-1, 5-2]. The migmatite in Bandanwara shows
peculiar occurrences of augen or roddy shape, in which the
augen and rodds are filled with granitic materials [Loc.5-2](Plate 3-2). This may indicate incipient partial melting
induced by shearing. The Bhinai gneiss or migmatite is astrongly lineated rock with granodioritic composition
158 Geological Fieldwork in the Aravalli and Delhi belts in Rajasthan, India, 1999
[Loc.5-3, 5-5], and the grey gneiss in Salaani has a
homogeneous appearance and is granodioritic to dioritic in
composition [Loc.5-5].
Metapelite is rather scace in the area. We observed
garnet biotite gneiss intruded by a norite suite with a sharp
contact on a hill top near Sandmata [Loc.4-4].
Granulites of basic to intermediate composition occur
around Sandomata [LocA-3]. The outcrop is well banded
and composed of basic granulite, amphibolite, gneissic
bands of dioritic to tonalitic composition, and quartz
feldspathic gneiss. Basic granulite in the Bhinai gneiss is a
garnet-bearing amphibolite [Loc.5-4]. Charnockites are
exposed around Bandanwara, where the rocks are rather
massive, coarse-grained and porphyritic, with large feldspar
ovoids, several em to 10 em in diameter [Loc.5-l]. The
charnockitic rocks occur closely associated with augen
gneiss and migmatite with several intercalated bands of
basic granulite around Bandanwara [loc.5-2]. Charnockites
also occur southeast of Bhim [LocA-5].
Overall, the gneiss - granulite - migmatite terrain in
central Rajasthan is dominated by orthogneisses of plutonic
origin, and rather poor in metasediments, except of LocA-4.
Bar - Sendra Section in SDFBThe Bar-Sendra section represents a typical succession
of the Barotiya and Sendra groups, the lower part of SDFB
[Loc.6-2] (Fig. 6 A). The lithologic succession is
summarized in Fig. 6 B. The lower part is dominantly mica
schists with intercalation of conglomerate (the Bar
conglomerate) including pebbles of quartzite and granite.
The granite pebbles are believed to be derived from the
Western granite. Quartzite pebbles are strongly flattened
and seem to be flattened quartz veins. The middle part of
the Barotiya group contains calc-silicate rocks.
Granitic RocksThe Western granite in the observed outcrop [Loc.6-1]
is mostly a coarse-grained, two mica leucogranite,
including fine-grained mafic enclaves. The granitic rocks
are foliated and intruded by tourmaline-bearing pegmatite,
but are totally homogeneous in appearance. The Westerngranite is possibly the basement of Bar - Sendra section,
because granite pebbles are found in the Bar conglomerate.The protolith of pebbles, however, is not confirmed, and
Lithologies of the granite are similar to the post-Delhi intru
sions such as in Gogunda [Loc. 2-6, see above chapter].The Sendra granites [Loc.6-3] are exposed in several
plutons around central Rajasthan. A pluton located in the
eastern part of the Sendra group is a small body, severalkilometers in diameter, and is made up of foliated, two
mica granite containing a small amount of garnet. It caITies
fine-grained mafic enclaves, and the marginal portion of the
body is highly schistose. Another pluton is larger than the
former, and is 10 km in diameter. The central portion of
the pluton [Loc.6-5] is composed of a foliated and lineated
porphyritic leuocogranite, including small mafic enclaves.
The marginal portion [Loc.6-4] is a garnet-bearing two
mica granite, and is in contact directly with amphibole
schist and calc-silicate schist.
The most granitic rocks in this area have the sirnillar
lithological characteristics such as two mica and garnet
bearing mineralogy, suggesting a S-type granite.
Field Survey in Northeast Rajasthanaround J aipur
The field survey in northern Rajasthan took place
around Jaipur to Bairath during the period of Day 8 and
Day 9 (Fig.2, Table 1), guided by Dr. Pandit. This area
represents a standard section of the middle Proterozoic
Alwar basin of the NDFB, from the basement - lower
Raialo boubdary to the upper Ajabgarh group (Fig.7), with
several granitic intrusions in the NDFB.
Basement - Raialo Contact in SandkotraAn example of the basement BGC to lowermost
Raialo relationship was observed on a small hill behind
Sandkotra village [Loc.8-2]. The basement is composed of
Group Formation Lithology Locality
Bharkol F.carbonaceous phyllite.quartZite
rhyolitic f.,9-2Thanagazi F. carbonaceous phyllite.
Ajabgarh G. dolomitic marble, quartzite
Sariska F. brecciated quartzitewith carbonaceous phyllite
Kushalgarh F.marble with dolomitic marble,
9-1mica schist
Pratapgarh F. orthoquartzitewith mica schist
Alwar G. Kankwarhi F.mica schistwith quartzite, conglomerare
Rajgarh F.conglomerate. arkose 5.5.,
8-6quartzite
Tehla/jahaj-metabasalt with 8-5.8-7conglomerate. 9-5
GOYindpura F. quartzite. phyllite. marble
Raiala G. Serrate/Nithar F. quartzite with conglomerate 8-4
siliceous marble,dolomitic marble 8-3
Dogeta F. with quartzite, phyllite t 8-2-----------
-./'quartzite, phyll~ ~
~ ~
foliated granite-t ~
Basement (B . G . C.) with amphibolite
Fig. 7. Stratigraphic succession of the North Delhi Fold Belt
(NDFB) in the Alwar basin (After Pandit, 1999).
KANa Takashi et al. 159
strongly foliated (nearly vertical foliation) tonaJitic rocks
with several intercalations of greenschist and amphibolite
bands, and corresponds to the BGC. A quartzite bed, the
lowermost Raialo rock, overlies the basement with distinct,
angular unconformity, and is itself overlain by siliceous
marble. The marble bed is exposed widely in the area and
mined in many quarries [Loc.8-3). The marble often
includes actinolitic amphibole, pale green in colour and
more than 20 cm in length.
DFB Sequence in the Alwar BasinThe NDFB succession in the Alwar ba in is divided
into the Raialo, Alwar and Ajabgarh groups (Fig.7). The
Dogeta formation, the lower part of the Raialo group,
consists mainly of quartzite and siliceous marble, as
mentioned above [Loc.8-2, 8-3). The Serrate quartzite, the
middle part of group, overlies the marble, forming a ridge
along Tehera hill [Loc.8-4) (Plate 3-3). Quartzite in the
Alwar basin shows distinct ripple marks of partly wedge
like form on tlle urface [Loc.8-1). This form may be due to
the overlapping by later folding. The upper part of the
Raialo group is marked by metabasalt [Loc.8-5, 8-7,9-5).
Along the valley in Sariska sanctuary, a thick boulder
conglomerate of the Alwar group overlies the metabasalt
[Loc.8-6). The conglomerate is polymictic and the
boulders reach more than 1 ill in diameter (Plate 3-4). This
bed is assumed to be the basal conglomerate, and marks the
unconfOlmity in the Alwar - Raialo relationship. The
Kushalgarh formation of the lower Ajabgarh group,
consists of thin alternations of dolomitic marble and
argillaceous bands, showing a radiator-like surface due to
the easy erosion of calcareous bands [Loc.9-1). The
Thanagazi formation also contains dolomitic marble and
carbonaceous rocks [Loc.9-2). The carbonate rock carries
spherulitic aggregates of actinolite.
Granitic Intrusions in NDFBThe NDFB rocks are intruded by several granitic
plutons, such as the Bairath and Ajitgarh granites.
The Bairath granite is made up mainly of K-feldspar
porphyritic gnei sose two mica granite. The granitic body
has direct contacts with highly schistose quartzite and
quartzite conglomerate in Bairath [Loc.9-3, 9-4). Thegranite is itself highly schistose parallel to the schistosity
plane of the quartzite at the contact, but no thermal effect isobserved. These features may suggest that the granite bodycould be a re-warked basement granite like a "mantled
gneiss dome". This is a possibility, and systematic age
determination is necessary in future studies. The Westerngranites and equivalent granitic bodies with similar
lithological features may have the same origin as the
Bairath grartite. These questions are important for
establishing the tectonic history of the Aravalli and Delhi
belts in the area.
The Ajitgarh granite [Loc.9-6) has a different
occurrence and lithology from the Bairath granite. The
granite consists of two rock types; soda- rich leucocratic
rock and potash-rich pink granite. Their mineralogical and
geochemical data indicate the characteristics of an A-type
granite (Pandit, 1999). The granites are less deformed than
the other plutons and are considered to be the post-NDFB
granitoids.
Concluding remarks of the 1999 field survey
The field urvey in 1999 has been finished
successfully. The area observed covers the main part of ilie
Aravalli Mountains in Rajasthan. We obtained a general
view of the geology of the Aravalli and Delhi belts and
establish a ba e for future studies by collaboration between
Japanese and Indian geologists. However, there seem to be
many important problems still unsolved.
The first one is, what is the fundamental geological
situation of the Aravalli belt? The belt contains quartzite,
dolomite and mica phyllite of mostly pelitic to psammitic
origin, but iliey are not simple cratonic cover sediments.
We observed several ultramafic intrusions and metabasalts
in the belt, and found manganese chert and mafic
ultramafic rock assosiations in the Udaipur area. Some
authors have assumed that the Aravalli belt was a
Proterozoic greenstone belt (Smith, 1992). However, we
carmot give general agreement to this view, because, chert
and iron chert (BIFs) and komatiitic lava are much less in
the belt than in typical greenstone belts, and also because
the belt is quite different from the late Archaean iron-rich
sequence such as in the Hamersley Basin. The AravaUi
Delhi relationship, and ilie geological position of the Delhi
belt are also important problems in the area.
The third problem is that the geochronological data are
insufficient in the belts, particularly the geochronology of
granites is much important, as mentioned above.
Metamorphic and igneous petrology on the gneiss
granulite-migmatite terrain in the BGC also provide
interesting problems, such as the roddy and augen-shapedmigmatite, which may represents a good example of strain
induced partial melting.
Acknowledgements
The field survey in 1999 has funded by the Grant-inAid for International Scientific Research Program of the
MONBUSHO (Ministry of Education, Science, Sports and
160 Geological Fieldwork in the Aravalli and Delhi belts in Rajasthan. India, /999
Culture of Japan, No. 10041123). The survey is also
supported by the UNESCO-lUGS IGCP-368 project (Study
of the Proterozoic events in East Gondwana) led by
Yoshida. We wish to express our thanks to all those who
helped us in the organizations and universities.
References
Gyani, K.C. and Chauhan, N.K. (1999) AravaUi - Delhi
fold belt and deep crustal segment, Rajasthan. A
profile and field guide. M.L.Sukhadia University,
Udaipur, 1-57.
Pandit, M.K. (1999) Excursion guide, Transect across the
South Delhi Fold Belt in central Rajasthan, and North
Delhi Fold Belt in Alwar basin, northeastern Rajasthan.
Manuscript received September 3, 1999.
Revised manuscript accepted March 9, 2000.
University of Rajasthan, Jaipur, 1- 10.
Roy, A.B. (1988) Stratigraphic and tectonic framework of
the Aravalli Mountain Range. In: Precambrian of the
Aravalli Mountain, Rajasthan, India. (Roy A.B. ed.),
Geological Society ofIndia, Bangalore, 3-31.
Roy, A.B., Paliwal, B.S., Shekhawat, S.S., Nagori, D.K.,
Golani, P.R., and Bejamiya, B.R. (1988) Stratigraphy
of the Aravalli Supergroup in the Type area. In:
Precambrian of the Aravalli Mountain, Rajasthan,
India. (Roy A.B. ed.), Geological Society of India,
Bangalore, 121- 138.
Smith, T.E. (1992) Volcanic rocks of Early Proterozoic
greenstone belts. In: Proterozoic crustal evolution
(Condie K.C. ed), Elsevier, 7-46.
Plate 11 : Banded gneiss and migmatitic appearances of the BGC [Loc.I-S).2: BGC-Aravalli contact [Loc.I-I). The person in the centre steps across the Archaean (left leg) and Proterozoic (right leg), and his hammer points to the boundary. The
person in the left end touches pyrophyllite schist by his left hand.
3: Flattened and elongated pebbles in the Debari conglomerate, the middle Aravalli [Loc. 1-2].4: Cross lamination in the Debari quartzite [Smelting factory near Loc.I-2]
Plate 2
I : Mica phyllite in the Jharol group, the upper Aravalli [Loc.2-4].
2: A close association of manganese chert (Mn), banded red chert (Chert) and ultramafic rock (UM) in the Jharol group [Loc.2-S].
3: A mu hroom-like intrusive body of serpentinite in the Jharol group [Loc.3-S].
4: Rapakivi texture in the Elephant Bridge granite in the SDFB [Loc.2-9].
Plate 3
I : Augen structure of the Anjana granitic gneiss [LocA-2].
2: Augen- or loddy- shaped migmatite in the Bandanwara area [Loc.5-2]
3: Hilly outcrop of the Sen'ate quartzite, the middle Raialo group, and a distant view of the Fort near Tehera [Loc.8-4].
4: Boulder conglomerate of the lower Alwar group [Loc.8-6]