48

CHAPTER 3

GEOLOGICAL SETTING

3.1 REGIONAL GEOLOGY

The Precambrian terrains of Peninsular India are represented by five cratonic

nuclei defining two major tectonic blocks: the Northern Indian Block and the Southern

Indian Block (Fig. 3.1a). The cratonic nuclei in the Northern Indian Block are

represented by the Aravalli Craton in the west and the Bundelkhand craton on the north,

and the Southern Indian Block includes the Dharwar Craton in the south, the

Singhbhum craton in the east and the Bastar craton in the north. The contact between

the Northern Indian block and the Southern Indian Block is marked by a major tectonic

zone referred as the Satpura Mountain Belt or Central Indian Tectonic Zone (Fig. 3.1b-

c).

The study area on the southern flank of Satpura Mountains consists of an

Archean basement complex (Tirodi Gneiss) with a thick succession of Proterozoic rocks

(the Sausar Group) distributed over an ENE–WSW trending, complexly folded arcuate

belt occupying an area of 210 km X 30 km. The Sausar Group (SSG) consists of

regionally metamorphosed pelitic and calcareous sediments. The entire succession was

affected by three phase of regional deformation and low to medium grade

metamorphism (Mohanty 1988; Mohanty 1993; Mohanty 2010a; Mohanty 2011;

Mohanty and Mohanty 1996; Mohanty et al. 2000). In the both side of low grade rocks

of Sausar Group two belts of granulites facies of metamorphism are present, Ramkona

Granulite Belt in the north and Balaghat- Bhandara in the south. The southern granulite

belt associated Central Indian Suture/Shear zone (CIS), which is a high strain ductile in

nature (Fig. 3.1b). The CIS is a 500-km-long, trending ENE–WSW dips northward,

extending from southeast of Nagpur to south of Korba (Jain and Yedekar, 1989) and the

width of the CIS ranges between 0.2 and 4 km.

The Sausar Group is mainly composed of metamorphosed sediments of

predominantly greenschist-amphibolite facies with local granulite facies (Yedekar et al.,

1990). Both TG and SSG show imprints of polyphase deformation (Mall et al., 2008).

The age of basement gneiss (Tirodi Gneiss) is 2325- 2494 Ma (Sm-Nd age; Ahmad et

al., 2009; Mohanty, 2011). The contact of the Tirodi Gneiss and the Sausar Group is

marked by presence of an unconformity composed of polymictic conglomerate

49

(Mohanty, 1993). The age of Sausar sedimentation is as ~2.2 to 2.4 Ga (Mohanty, 2003,

2012). The post-Satpura orogeny is tentatively dated at 1525±70Ma (Sarkar et al.,

1986; Naqvi and Rogers, 1987). The peak metamorphic condition of the Sausar

supracrustals is estimated at c.7 kb, and at 675 °C (Bhowmik et al., 1999).

Fig. 3.1 a: Map showing of tectonic units of India (a) after Mohanty, 2011, (b) after

Pradhan et al., 2010.

Fig. 3.1 c: Geological map of Central India showing the study area (after Bhowmik et

al., 2012).

a b

c

Study Area

50

3.2 PREVIOUS WORK

The manganese deposits of the Bharweli-Ukwa area in the Balaghat district

were first investigated by Bose (1889; cited in Fermor, 1909), who have reported

association of phyllite, sericite-schist, quartzite and jaspery-quartzite and manganese-

ore forming the “Chilpi Ghat Series”, deposited over Archaean basement gneisses

represented by the Baihar Gneiss and Chauria Gneiss. Fermor (1909) mapped the area,

and retained the three divisions proposed by Bose (1889; Table 3.1), but suggested that

the rocks previously mapped as Archaean schists and gneisses may be more intensely

metamorphosed forms of the Chilpi rocks, comprising of slates, phyllite, and mica

schists with some quartz schist and conglomeratic grit. Other metamorphic rocks

reported from the area include muscovite biotite gneiss, mica schist, quartzite, with

pyroxene-gneisses, epidote-gneisses and hornblende schist.

Burton (1912-1914; cited in Fermor, 1931) mapped the Bharweli area and

proposed a two-fold stratigraphic division (Table 3.2). The calc-gneiss and orthogneiss

of the area (i.e. metamorphic and “Crystalline Series” and intrusive granite of Fermor,

1909) were thought to be crystallized under the same conditions of metamorphism. The

calc-gneisses were considered as mixed gneisses and were named as the “Sonawani

Series”.

Manganese bearing metamorphic rocks of Chhindwara, Nagpur and Bhandara

district were mapped by Fermor and others during 1911 and 1927, and were placed

under the “Sausar Series” (Fermor, 1931), comprising of calc-granulites, calcitic

marble, gondite with manganese ore, dolomitic marble, hornblende schist and

amphibolite. These rock units were grouped under six units: Sitapar, Bichua, Chorbaoli,

Mansar, Utekata and Lohangi “Stages”. Fermor’s subdivision of the various stages

within “Sausar Series” was slightly modified by West (1936), with addition of two new

stages namely Kadbikhera and Junewani.

Straczek et al. (1956) modified the stratigraphy of the “Sausar Series” suggested

by Fermor (1926, 1932) and West (1936) and recognized wide spread occurrence of

Biotite Gneiss (Tirodi Gneiss). Sitasaongi Formation was introduced as a new unit

above the Tirodi Gneiss. The Utekata and Sitapar Formations proposed by the earlier

workers were omitted (Table 3.3).

51

Table 3.1 Regional stratigraphy of the Chilpi Ghat Series of the Balaghat area

(after Fermor, 1909)

1. The Chilpi Ghat Series

2. The Metamorphic and Crystalline Series (designated as Baihar Gneiss by Bose, 1889).

3. The intrusive granite (designated Chauria Gneiss by Bose, 1889 and probably equivalent to Bundelkhand Granite).

Table 3.2 Two-fold stratigraphic division of the Balaghat-Sonawani area

(after Burton, 1912-14)

Chil

pi

Ghat

Ser

ies Phyllite, sericite schist, derived from phyllite, pegmatite and thin

feldspathic tuffs.

Blue slates, slaty quartzite, feldspathic tuffs.

Phyllite

Manganese Ore

Phyllite and jaspery quartzite

Basal conglomerate and grit

~~~~~~~~~~~~~~~~~~~~~~~Unconformity~~~~~~~~~~~~~~

Sonaw

ani

Ser

ies

(anci

ent

met

ased

imen

ts) Quartz muscovite schist

Phyllite schist

Feldspathic quartzite

Quartz muscovite schist

Calc-gneiss and crystalline limestone

Table 3.3 Geological succession of the Sausar Group

(after Straczek et al., 1956)

FORMATION DOMINANT LITHOLOGY Bichua Formation Dolomitic Marbles and Calc-silicates.

Junewani Formation Muscovite-Biotite Schists and Granulites.

Chorbaoli Formation Quartzite and Schists.

Mansar Formation Muscovite Schists and Muscovite-Biotite.

Lohangi Formation Dolomitic Marbles and Calc-silicates.

Kadibikhera Formation Quartz Biotite Granulites.

Sitasaongi Formation Felspathic Schists and Quartzites.

Tirodi Biotite Gneiss Biotite Gneiss with Amphibolites Calc-Gneisses and Quartz-Biotite Granulites.

On the basis of continuous westward grading of the low-grade phyllite and

sericite schists of the Bharweli-Ukwa area into the normal muscovite schist of the

Mansar Formation and associated quartz-muscovite-schist of Sitasaongi Formation,

52

Narayanaswami et al. (1963) correlated the phyllite and sericite schists of Bharweli-

Ukwa area with the Mansar Formation of the Sausar Group (Fig. 3.2; Table 3.4).

Table 3.4 Regional geological succession of the Sausar Group

(after Narayanaswami et al., 1963)

GROUP FORMATION PRINCIPAL LITHOLOGY

Sau

sar

Gro

up

Bichua Formation Dolomitic marble, calc-gneisses and calc schist

Junewani Formation Mica schist and quartzite; granulites and biotite gneisses.

Chorbaoli Formation Quartzite, feldspathic schist, gneisses, autoclastic quartz conglomerate.

Mansar Formation Mica schist and gneisses, graphitic schist, phyllite and quartzite; manganese deposits and gondites (most wide spread formation)

Lohangi Formation Three calcareous members showing gradational contacts with one other.

Lohangi Member

Pink and white calcite and dolomitic marble.

Utekata Member

Calc-silicate granulite and gneisses, epidote quartzite and manganese deposit.

Kadbikhera Member

Quartz –biotite schist, granulites, schist and gneisses.

Sitasaongi Formation

Quartz-muscovite schist and felspathic muscovite schist, mica gneisses, quartzite and conglomerate.

~~~~~~~~~~~~~~~~~~~ ? Disconformity ~~~~~~~~~~~~~~~~~~~

Tirodi Gneiss *

Biotite genesis with amphibolites, calc-silicate gneiss, granulite and feldspathic mica schist.

~~~~~~~~~~~~~~~~~~~ ?Unconformity ~~~~~~~~~~~~~~~~~~~

Older Metamorphics

Charnockite, orthogneisses and granite biotite gneisses, hornblende gneisses, amphibolites and calc granulites.

* Age is considered to be 2325-2494 Ma (Sm-Nd age reported by Ahmad et al., 2009;

Mohanty, 2011).

53

Fig. 3.2: Geological map of the Sausar fold belt (after Narayanaswamy et al., 1963)

54

Tripathi et al. (1981) studied the rocks of Bharweli-Ukwa area specially exposed in

Baihar area and correlated the Baihar Gneiss of Bose (1889) with the Junewani

Formation of the Sausar Group and considered the Chilpi Group to be stratigraphically

older and correlatable with the Sausar Group. Rao (1981) suggested the low-grade rocks

of Bharweli-Ukwa Baihar belt, forming the Chilpi Group, to be equivalent to the

Mansar Formation of the Sausar Group. Dasgupta et al. (1984) considered the schistose

rocks of Bharweli-Ukwa area as “Sausar metasediments”, having sheared contacts with

the older Chilpi Group and younger gneisses of Baihar (Table 3.5).

Table 3.5 Stratigraphy of the Bharweli-Ukwa area

(after Dasgupta et al., 1984)

Deccan Traps

~~~~~~~~~~~~~~~~Unconformity~~~~~~~~~~~~~~~~

Baihar Biotite Schist

Biotite Gneisses

~~~~~~~~~~~~~~~Sheared Contact~~~~~~~~~~~~~~~~

Sausar Metasediments

~~~~~~~~~~~~~~~Sheared Contact~~~~~~~~~~~~~~~~

Chilpi Rocks

~~~~~~~~~~~~~~~~Unconformity~~~~~~~~~~~~~~~~

Malanjkhand Granite

Jain et al. (1990, 1991, 1995) mapped a major shear zone from southeast of

Nagpur in the west to south of Korba, and Hatta and Baihar in Balaghat district in the

east. This shear zone is termed as the “Central India Shear” (CIS) zone. The rocks of

Chilpi Ghat Group are separated from the manganese belt by a gneissic country through

which this major ductile mylonite zone (CIS) passes (Jain et al., 1991). The manganese

bearing rocks of Bharweli-Ukwa area were considered to be younger than the Sausar

Group and are exposed to the north of this Central Indian Shear (Fig. 3.3, Table 3.6; cf.

Jain et al., 1991). The rocks to the south of CIS were mapped as the Khairagarh Group,

Nandgaon Volcanics, Dongargarh Granitoid, and Malanjkhand Granitoid (Table 3.7).

55

Table 3.6 Lithostratigraphy of the Bharweli-Ukwa area (after Jain et al., 1991)

GROUP FORMATION ROCK TYPES

Quaternary

Deccan Trap

Alluvium ~~~~~~~~~~~~~~~~

Basic volcanics ~~~~~~~~~~~~~~~~

Bharweli Group Bharweli Formation Intrusives Sericite Phyllite Quartzite Sericite Schist with Mn ore Basal Conglomerate and Grit

-----------------Tectonic Contact--------------

Sausar Group Tirodi Formation Granite Intrusive Sericite Muscovite Hornblende Schist (With Quartzites) Granite Gneiss/Migmatite Biotite Gneiss Biotite Schist

Table 3.7 Stratigraphic correlation of the rocks of Central India (after Jain et al.,

1991)

GROUP NORTH BLOCK SOUTH BLOCK

Bharweli

Group

Khairagarh Group 1700-1500 m.y.

(Sarkar et al., 1967)

Chhatisgarh Group

~~~unconformity~~~

~~~~~~~~~~~~~~~~~~~~ Unconformity~~~~~~~~~~~~~~~~~~~~~

Nandgaon Volcanics

(2180 m.y. to 2503 m.y.)

(Sarkar et al., 1981)

Dongargarh Granitoid

(2200 m.y. to 2438 m.y.)

(Sarkar et al., 1981)

Malanjkhand Granitoid

(2263 m.y.)

~~~~~~~~~~~~~~~~~~~~ Unconformity~~~~~~~~~~~~~~~~~~~~~

Sausar Group Sausar Tirodi Gneiss

Migmatites

Amgaon Gneiss / Migmatites

56

Fig. 3.3: Geological map of the study area (modified after Jain et al., 1991)

57

3.3 BRIEF DESCRIPTIONS OF THE VARIOUS FORMATIONS

The rock units mapped in the area around Bharweli include the basement granites and

gneisses, the Tirodi Formation and the lower units of the Sausar Group. The Chorbaoli

Formation, Junewani Formation and Bichua Formation are not exposed in the study area. The

regional geological succession of the Sausar Group which is exposed around the study area is

given in Fig. 3.4 (Sarkar et al., 2011).

3.3.1 Older Metamorphics (unclassified) and associated granites

The outcrops of the granitic rocks in the study area are less, mostly

surrounded by alluvium or covered by dense reserve forest. Much of the work is based on the

regional studies. These rocks are exposed to the south of Balaghat, along Wainganga river

Fig. 3.4: Stratigraphic column showing lithostratigraphic units of the Balaghat

manganese deposit (after Sarkar et al., 2011).

58

valley. The biotite hornblende rich granite shows gneissose structure. The large outcrops of

the granites are exposed in Lamta-Charegaon-Nagarwada area, and continue up to

Malanjkhand-Lanji-Amgaon area. In the Lalburra-Tirodi-Barghat (Seoni) area, pink fine-

grained varieties of granite with biotite gneiss and granite gneiss are exposed (Figs. 3.5 a &

b).

Fig. 3.5: Field photographs showing (a) fine grained granite (b) coarse grained granite

gneiss.

3.3.2 Tirodi Formation

This Formation mainly consists of gritty conglomerate and medium grained schistose

biotite gneiss to porphyroblastic biotite gneiss (Fig. 3.6). The gritty conglomerates have a

very important stratigraphic position. The rock contains very large size assorted pebbles

comprising of quartzite, cherty quartzite, chert, vein quartz, granite, and granite gneiss. The

matrix is generally foliated and consists of quartz, feldspars and mica. The conglomeratic

grit, at places, is arkosic in character (Fig.3.7 a). The schistose biotite gneiss is fine grained

hard and compact in nature (Fig. 3.7 b).

3.3.3 Sitasaongi Formation

Rocks occurring below the Manganese-ore bed in this area consist of quartzites with

minor amounts of quartz schist. The quartz schists are less exposed in study area. It is not

exposed in the mine area, but covered by overburden mining dumps. The quartzite is

feldspathic in nature, very coarse grained and thinly banded (Figs. 3.8 a & b).

3.3.4 Lohangi Formation

Rocks of the Lohangi Formation comprising chiefly pink calcite marble and calc-

granulite form a distinct horizon between the Sitasaongi and Mansar Formations in other

parts of the belt. This horizon is, however, markedly absent over the greater part of this area.

a b

59

Fig. 3.6: Geological map of Balaghat manganese deposit.

60

Fig. 3.7: Field photographs showing (a) boulders in gritty conglomerate and (b) biotite

gneiss

Fig. 3.8 a-b: Field photographs of feldspathic quartzite of Sitasaongi Formation showing

thin banding.

3.3.5 Mansar Formation

Overlying the Lohangi Formation is the manganese bearing Mansar Formation. The

characteristic of the Formation is presence of manganese ore, deposited as admixture of pure

and impure sediments. The pure sediments resulted in high quality Mn ore, where as the

impure sediments include jasperiod quartzite and manganiferous quartzite, combinedly

known as Banded Manganese Formation (BMnF). This phenomenon persist over the entire

manganese belt (Fig. 3.9 a). The manganese ore is confined between the sericite schists of the

Mansar Formation and feldspathic quartzite of Sitasaongi Formation (Fig. 3.9 b). Mansar

Formation also comprises of phyllite, muscovite schist, sericite schist in low grade

metamorphic zone.

Banding Thin bands

a b

a b

61

Fig. 3.9: Field photographs of BMnF showing (a) Jasperoid and manganiferous band, and

(b) manganese ore confined between sericite schist and feldspathic quartzite.

These phyllites appear to have undergone at least two phases of deformation, the

present schistosity being a crenulation cleavage that has more or less completely transposed

the earlier schistosity. At places, some of these phyllites show compositional layering of

sericite, chlorite and quartzose layers, with quartz showing neither recrystallization nor any

directional orientation and appears to be bedded. The phyllite constitutes the major rock type

in this area, consisting of sericite, chlorite and at times with fine biotite (Fig. 3.10 a).

The sericite schist is exposed in the Bharweli area trending ENE-WSW. The sericite

schist is fine to medium grained. It is greenish to dark grayish black in colour. Sericite

schist grades into medium grained mica schist towards the northern part of the study area.

The mica schist is fine to medium grained and is grey to brownish grey in colour. The sericite

schist is fine grained and contains quartz, flakes of sericite and muscovite. The dimensionally

oriented flakes of sericite, quartz and occasionally muscovite define the schistosity (Fig. 3.10

b).

Fig. 3.10 Field photograph showing (a) crenulated phyllite and (b) sericite schist.

Sericite schist Manganese ore

Manganiferous quartzite

Jasperiod quartzite Manganese ore

Feldspathic quartzite a b

a b