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]