Aes1105

Research Article International Journal of Advances in Earth Sciences, Volume 1, Issue 1, 2012, 20-32

© Copyright 2012, All rights reserved Research Publishing Group

20

Geochemical Signatures of Archean Felsic Volcanism in the Central part of Bundelkhand Craton, Central India

S.P. Singh Department of Geology,

BundelkhandUniversity, Jhansi- 284128 (UP)

Abstract

The metavolcanics and metasedimentaries of Bundelkhand Massif confined into the central part and is related to the greenstone belt. The metavolcanics are characterized by bimodal composition, ranges from felsic to mafic and dominated by felsicsmagmatism along the E-W trending shear zone. The felsic volcanism is mainly rhyolites, rhyodacites and andesites. Geochemical studies suggest high SiO2 ranges from 66.2 to 75.5 wt% and high Al2O3 from 12.2to14.7 wt% and high Na2O+K2O write the value. They are also enriched in LREE and strong negative Eu anomaly. The different variation diagrams for major and trace suggest island–arc tectonic environment for the felsic magmatism in Bundelkhand during late Archean.

Key Words: Archean crust, felsic volcanism, Bundelkhand Massif, greenstone belt, geochemistry

1. Introduction

The Indian shield has been divided into number of cratons and provinces. The nuclei of early to middle – Archean crust were developed in six cratonic blocks of Indian shield with the minor changes in their nature and occurrences (Naqvi 2005). The remnants of early crustal components have been described from Dharwar (Taylor et al. , 1984, Chadwick et al., 2003), Bastar (Balmiki et al., 1990), Singhbhum (Saha, 1994) and Aravallicratons (Ahmad and Tarney, 1994) . The petrological and geochemical results show thick to thin occurrences of mafic and felsic volcanic sequences of Archeanmagmatism in each nucleus part. The geochronoligical data obtained by Mondal et al. (2002) and Sarkar et al. (1996) suggest that primordial crustal components in Bundelkhand massif are widely spread and nucleated at Middle Archean times (3500/3300 Ma). In recent year some investigation have been taken even though our present state of information on the geological and geochemical data about the crustal evolutionary processes from nucleus to stabilization stage in Bundelkhandcraton is limited as compare to other part of Indian shield. The central part of Bundelkhand massif has been advocated to preservation of the signatures of early crustal components (Singh et al 2007, Mondal 2010). The low and high grade metamorphic event of Archean has been opined by some workers in the Central Part of massif (Singh and Dwevedi, 2009, Saha et al., 2010). The low grade 20olcanic20ic known as BnMM includes the metavolcanics and metasediments were developed in the middle to late Archean times in the southern and central part of Bundelkhand massif. The occurrences of different type of volcanism ranges from felsic to mafics in BnMM from the central part of Bundelkahnd were mapped in the E-W strike length of 200 kms between Mohar/Umariakalan in west and Mahoba in east (Fig.1). It was found that all the metavolcanics are confined between biotite granite (BG) in north and high grade 20olcanic20ic (BnGC) in south. Our present knowledge about the geological signatures of primordial crust and presence of different components of Archeans are mostly fragmentary and meager due to lack of data. The present paper attributes the geochemical signature of felsic 20olcanic associated with metasedimentaries in the central part of Bundelkhand and also discusses a possible tectonic environment of evolution of the metavolcanics in Bundelkhandcraton.

Singh / International Journal of Advances in Earth Sciences, Volume 1, Issue 1, 2012, 20-32

21

Fig.1. Regional geological map of Bundelkhand craton modified after Basu (1986, and Mondal et al

2002, Singh et al 2007). The metavolcanics are mainly exposed in the north of Basement Complex in the central part of Massif. M: Mohar, MK: Mankuan, K: Khajaraha, D: Dhaura, B: Balyara, G: Gora, T: Tejpura, KT: Kathora. The numbers represent the reference number of analysed rock samples of metavolcanics given in Table 1.

Table-1 Chemical Analysis of Metavolcanics of Northern Bundelkhand Massif

Andesite Andesite Andesite

Mylnonitesed hornblende granite Andesite Rhyodacite Rhylite Rhyolite Rhylite Rhyolite Rhyodacite

Andesite Andesite Andesite

Sl No 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Sample NO PM-118 PM/84 PM/93 PM-130 PM-107 PM-74 GM-9 KT-X CM-3 PM-73 PM-68 PM/86 P-54 D-14A

SiO2 71.21 73.68 75.83 70.60 70.08 73.57 76.96 76.05 76.40 72.95 67.10 66.86 66.22 66.62

Al2O3 14.71 14.05 12.32 13.03 12.39 14.98 12.23 12.46 12.97 14.85 11.99 13.04 14.88 14.97

Fe2O3 4.31 2.01 2.12 4.77 4.91 2.19 1.10 1.83 1.07 2.02 6.09 6.60 5.15 4.77

MnO 0.04 0.03 0.05 0.08 0.11 0.03 0.01 0.02 0.01 0.03 0.09 0.12 0.08 0.07

MgO 0.19 0.80 0.59 1.27 1.09 0.63 0.41 0.16 0.25 0.48 2.97 3.04 1.05 1.36

CaO 1.11 1.70 1.79 2.36 2.70 1.88 0.28 0.37 0.68 0.89 2.81 1.98 3.77 3.76

Na2O 3.58 2.60 4.06 2.96 3.21 1.35 2.71 3.46 2.75 2.05 2.59 3.60 4.10 5.01

K2O 3.20 2.23 1.26 3.18 3.49 4.19 4.92 3.94 4.72 4.94 3.82 2.07 2.28 1.58

TiO2 0.10 0.11 0.14 0.42 0.60 0.13 0.03 0.09 0.11 0.12 0.55 0.62 0.40 0.45

P2O5 0.02 0.08 0.03 0.15 0.28 0.04 0.01 0.01 0.02 0.02 0.16 0.13 0.14 0.16

SUM 98.47 97.29 98.19 98.82 98.86 98.99 98.66 98.39 98.98 98.35 98.17 98.06 98.07 98.75

VindhyanSupergroup Bijawar Group Granitoids BnMM BnGC

Mafics of Madaura Alluvium Lineaments

25o

78o 80

o

JHANSI KARERA

BABINA

MAURANIPUR

MAHOBA

BIJAWAR

IN DIA

250

DELHI

LALITPU

N

2 D M

MK

S

5

9 2 12 Sampl

4

1 3


22

2. Geological setting A vast track of reworked granitic terrain of Archean with different magmatic and thermal

events occurs in the northern part of the Central Indian shield which is known as Bundelkhand massif. This is a semicircular outcrop of the Archaeans of Bundelkhand terrain where Bijawar and Vindhyan sediments of Proterozoic were deposited. Thus, the entire terrain structure in north of SONATA appears to be an independent cratonic block in the Indian shield which is delineated by Son Narmada Fault in south from the Mahakaushal Group of rocks and Arravalli of Rajasthan by Great Boundary Fault (GBF) in the west. The craton is also detached from granitic plane of Himalayan folded belt in north by E-W trending gravity fault known as Yamuna fault. The Archean terrain represented by Bundelkhand massif is thus a cusp shape structure where the E-W trending Proterozoic supracrustal rocks of Bijawar, Gwalior Group and Vindhayan Group are present (Basu 1986). Singh et al. (2007) reviewed the geology of the Bundelkhand region and suggest that the Bundelkhand Gneissic Complex (BnGC) is the oldest component that comprises high grade metamorphics of ortho and paragneisses including the amphibolites and TTG overlain by low grade metamorphic rocks of greenstone belts known as Bundelkhandmetasedimentaries and metavolcanics (BnMM). These high and low grade metamorphites have several phases of deformation (Singh et al. 2007). Subsequent to these developments, the Archean crust of Bundelkhand was subjected to acidic magmatism known as BundelkhandGranitoid (BG) on large and extensive area. The emplacement of these granitoids (BG) is considered in the volcanic arc environment in the late Archean time (Mondal et al., 2002) and is mainly responsible for crustal growth and tectonic process of the Archean crust transformation into a stable craton. Thus massif represents the culmination of a long period of ancient structural, tectonic, magmatic and geothermal cycles of several episodes that may have been operative from Archaean to early Proterozoic.

The geological investigations in the different cratonic part of Indian shield point out a distinct geological, geochemical and geophysical configuration for the crustal growth and series of tectonic process involved the in early primordial crust and nucleus component of early Archean. Recently, this has been advocated that signatures of early supracrustal components are also available in Bundelkhand massif like other cratonic blocks (Sarkar et al., 1996, Sharma 2000).

The metavolcanics have been reported from most of the cratonic blocks of Indian shield (Naqvi, 2005) and have been characterized by their bimodal nature. A detailed field and lab investigation in the central part of Bundelkhand massif carried out in the recent years deal a narrow belt of volcanic rocks ranges from basaltic komatitie to rhyolite and rhyodacite which are some places intercalated with metasedimentries. However, the present knowledge about the geological signatures of primordial crust and presence of different components Archeans are mostly fragmentary and meager due to lack of data. The geological and geochemical information about such suit from Bundelkhandcraton is discussed in the preceding sections.

3. Metavolcanics and its petrography

The metavolcanics are exposed mainly along the E-W trending lineament in the central part of massif and are characterized by fine grained texture with different variety of flow structure (Fig. 2A). The volcanics are rhyolites, andesites, rhyodacites and basalt in composition and are charecterised as low-grade metavolcanics. Among those, metabasalt is least common while felsic volcanics are most common. The metabasalt and meta-andesite are mainly exposed in the Mohar, Khajaraha areas while the meta-rhyolite and meta-rhyodacite are exposed around Gora, Babina, Tejpura, Dhaura, Mohar, Umarikalan and Dhamna areas (Fig. 1). The felsic volcanics (rhyolite, dacite and rhyodacities) are brown to the dark brown (Fig. 2.A) in color and sometimes pinkish brown, and light pink colored metavolcanics are also visible (Fig. 2.D). The andesite is mostly gray to light grayish brown in color (Fig. 2.B). The patches of dark brown to brownish dark rhyodacite within dacitic rock have been also found at many places. They are very hard and compact and characterized by conchoidal fractures. The broken surface of rock sample shows ring-type structure. Xenolith of metavolcanic have been found in pink granite at north of village Dhaura and many other places the Bundelkandgranitoid is found as intrusive into rhyolites as several places (Fig. 2.E). These


23

metavolcanics are usually associated with metasedimentaries which comprises mainly banded magnetite quartzite (BMQ), ferrogenousquartizite, quartzite and carbonate rocks.

The metavolcanics are usually found at lower tropography. Texturally, they are fine grained but the medium to coarse grained feldspar; epidote, clinozoisite, quartz and magnetite embedded in the fine grained matrix of feldspar have been also identified at some places. The phenocrysts are sometimes found to be rotated also. Coarse-grained granite emplaced into mylonitic meta-rhyolites, meta-rhyodacites are also found (Fig. 2.C). The occurrences of 100 to 200 m thick E-W trending brittle-ductile to ductile shear zone from the myloniticmetavolcanics (Fig. 2D) suggests a strong compressional tectonic event subsequent to volcanism, which was perhaps subsequent to felsic volcanism in the central part of Bundelkhandcraton.

The K-feldspar, plagioclase, quartz and magnetite are the main minerals constituents but at places sericite, amphibolites, epidotes, zircon, chlorite and sulphide of iron are also present in the subordinate amount. Biotite is usually present as medium to fine grained, elongated flacks of greenish to greenish brown crystals along the shear planes. Chlorite is more common in andesite while sericite, K–feldspar are confined in rhyolite and rhyodacite. Epidote, chlorite and quartz are common inclusion in amphiboles. The recrystallisation is more common in orthoclase with compare to plagioclase in the matrix of sheared zone. Biotite shows variation in colors from green to dark brownish to brown, characterized by medium to fine grained texture and mainly observed in mylonitisedmetavolcanics. Quartz observed as coarse to fine grained, at places as inclusions within the feldspar. In most of the thin section quartz crystals observed in fragmented form but at many of the cases the aggregates of recrystalised coarse-grained crystals of quartz are observed as lensoidal or eye shaped body within the matrix .

Fig.2. A: Dark brown coloured Rhyodacite exposed at village Khaora, south of Mahoba.

B: Recrystallised crystals of epidote, calcite, amphibole embedded in the fine- grained Ansesite at Kathora.

C: Pink granite vein traversing across the E-W trending Rhyolite (Mylonitised) at 3km east of Mankuan.

D: Vertical shears in E-W trending myloniticRhyodacite at 4km south of Babina. E Contact of rhyodacite with biotite granite near Mohar F. A view of felsic volcanics South of Mohar


24

Chlorite is present as medium to fine-grained texture, light green to colourless. Chlorite also seen generally within the mylonite matrix, at places observed as inclusion within the feldspar and are more common in andesites and also observed as secondary mineral altered from biotite. Magnetite observed as coarse to medium grained texture, at places magnetite content is very high and sometimes observed as aggregate of granules. Hornblende shows light green in colour, fined-grained texture in association with epidote, biotite and feldspar.

4.Geochemistry

Major and trace elements The geochemical result presented in Table-1 suggests that the metavolcanics have wide

variation in silica content ranging from 76-66 wt% and their values lies in composition field of dacite to rhyolite. However, most of the samples are lying in the rhyodacite to rhyolite field (Fig. 3a and b)) and are characterized by meta-aluminous to peraluminous and high calsic alkaline in composition (Fig 6 a,and b). The K2O content of metavolcanics ranges from 1.26-4.94 wt% and it is noted that with increasing the Na2O, the value of K2O decreases (Fig. 4a). The signatures of geochemical variations based on major oxides in different bivariant diagrams show distinct trend of crystallization (Fig. 4b and c). The trends of major and trace element of Harkar’s

Fig.3a. Classification of the metavolcanics of Bundelkhand based on total alkali versus silica (TAS)

Fig.4. Bivariant plots showing the crystallization trend in Felsic volcanism.

60 65 70 75 804

5

6

7

8

Na 2O+K 2O

SiO 2

0 1 2 3 40

1

2

3

4

CaO

MgO

1 2 3 4 5 61

2

3

4

5

6

K 2O

Na 2O

T

35 40 45 50 55 60 65 70 75 800

5

10

15

Na 2O+K 2O

SiO 2

basaltandesite

dacite

rhyolite

trachyte

phonolite

trachyand.

picrite

nephel. hawaiite

mugearite

benmorite

35 40 45 50 55 60 65 70 750

2

4

6

8

10

12

14

16

Na 2O+K 2O

SiO 2

Picro-basalt

Basalt BasalticandesiteAndesite Dacite

Rhyolite

Trachyte

TrachydaciteTrachy-andesite

Basaltictrachy-andesiteTrachy-basaltTephriteBasanite

Phono-Tephrite

Tephri-phonolite

Phonolite

Foidite

7


25

variation diagram appear to be consistent with the magmatic differentiation as the main process of evolution of magma (Fig. 5a,b,c). The plotted values in the variation diagram proposed by Harker (1909) for CaOvsMgO (Fig. 4.b)and Al/(Ca+Na+K)vs Al(Na+K) (Fig. 6a) and various other modal (Fig 6b,c and d) clearly point out that calsic and alumina phases was initially fractionate from the magma. The SiO2vs Major oxides (MgO,CaO,Fe2O3 and MnO) point out that the metavolcanics (Fig.5) were initially enriched with mafic minerals and subsequent stages they become felsic in nature .

Fig.5. Bivariant plots showing the crystallization trend in Felsic volcanism in Bundelkhand

Fig 6: Discrimination diagram for the metavolcanics of Bundelkhand showing calc-alkanine to high calc alkaline type composition which are meta-aluminous to per-aluminous in composition.

45 50 55 60 65 70 750

1

2

3

4

5

6

7

K2O

SiO 2

Arc Tholeiite Series

Calc-Alkaline Series

High-K Calc-Alkaline Series

Shoshonitic Series

Shos: Basalt Shoshonite Latite Trachyte

Rest: Basalt BasAnd Andesite Dacite Rhyolite

Arc rock types

0.5 1.0 1.5 2.00

1

2

3

Al/(Na+K)

Al/(Ca+Na+K)

Peralkaline

Metaluminous Peraluminous

Ab' Or

AnIrvine+Baragar 71

Sodic

K-rich

0 10 20 30 40 50 60 70 80 90 1000

10

20

30

40

50

Q'

ANOR

2 3a 3b 4 5a 5b

6* 7* 8* 9* 10a* 10b*

2 alkali rhyolite

3 rhyolite

4 dacite

5 (dacite)

6 trachyte

7 Q trachyte

8 Q latite

9 andesite

10 basalt

a b

c d


26

In the recent years the tectonic environment based on major and trace elements have been developed by various workers (Pearce et al 1984, Maniar and Piccole 1989, Roger and Greenberg 1990). An attempt has been made to discriminate the possible tectonic setting for metavolcanics of the study area by using the different discrimination diagrams.The plots in the Pearce et al (1975) for the metavolcanics of Bundelkhand correspond to island arc type tectonics (IAT) for the formation of calc alkaline magma. The relationship of ratio of FeO/MgO against TiO2 to discriminate between the island arc and MORB setting proposed by Miyasiro 1975 shows the different field of island arcs. The plotting of these values clearly indicate the island arc (IA) field (Fig. 7) for the felsic rocks. The discrimination diagram using ZrvsTi proposed by Muller (1980) points that most of the metavolcanics of Bundelkhandcraton correspond to calc-alkaline composition while the plot of ZrvsSr diagram proposed by Muller (1980) suggests island tectonic setting (IAT). Thus the different variation diagrams after Pearce (1982) discriminate that metavolcanics of Bundelkhand region are related to island arc type lava (Fig.7).

Fig.7. Discrimination diagrams for the metavolcanics of central Bundelkhand (after Pearce et al.

1984). A: Y+Nb vs Rb, b: Yb+Ta vs Rb diagram, c: Nb vs Y diagram and, d: Yb vs Ta diagram.WPG: Within Plate Granite, VAG: Volcanic Arc Granite, COLG: Collisional Granite and ORG: Oceanic Ridge Granite.

In order to discriminate the better understanding about the Archean felsic volcanism, the trace and rare earth elements variation diagram proposed by Martin (1993) and Harris et al. (1994) have been examined. The plotting of chondrite normalized values Ybvs (La/Yb)n and Y vsSr/Y (Fig.8a,b)

10 100 10001

10

100

1000

Rb

Y+Nb

syn-COLG WPG

VAG

ORG

1 10 1001

10

100

1000

Rb

Yb+Ta

syn-COLG WPG

VAGORG

1 10 100 10001

10

100

1000

Nb

Y

syn-COLG

WPG

VAG +

ORG

.1 1 10 100

.1

1

10

100

Ta

Yb

syn-COLG

WPG

VAG

ORG

a

cKT dK

b


27

values clearly suggest the classical island arc tectonic environment for the Bundelkhand felsic magmatism.

Fig. 8b. (Yb)N vs (La/Yb)N diagram showing plots of metavolcanics (after Martin 1993) and (b) Y vs

Sr/Y diagram showing plots of metavolcanics (after Martin 1993)

Sun et al. (1989) and Wood et al. (1979) proposed the mantle normalized incompatible elements spider diagram for the genetic interpretation of basalt. Their proposed diagram was further tested by Harmon et al. (1984) to study the trace element variation in different suites. The incompatible trace element pattern of metavolcanics of Bundelkhand plotted for spider diagram proposed by Sun et al. (1989) is relatively smooth and is characterized with significant depletion of Ba and Sr (Fig 9). The higher value of Zr and Rb pointing highly fractionated felsic magma.


28

Fig.9. The mantle normalized incompatible elements spider diagrams for the genetic interpretation

of felsic rock of Bundelkhand craton (after Sun et. al. 1989, Wood et al. 1989.)

The REE plotting (Fig.9) after the Chondrite normalize from the different parts of metavolcanics yield the gentle slope and smooth trend which is an indication of high fractionation of magma LREE than HREE on the larger scale regional domains. A distinct depletion trend in Eu and Hf anomalies has been noted from all the analysedmetavolcanics and is related to plagioclase fractionation. This pattern is found similar to metavolcanics found in different Indian cratonic blocks (Naqvi 2005). It is worth to mention that the REE pattern shown for granitoid and gneisses for Bundelkhand (Mondal et. al. 1998) differ for metavolcanics composition. Therefore, two different trends of REE for felsic volcanism and granitoid indicate that the acidic magmatism for granitoids and metavolcanics should be two different magmatic activities in Bundelkhandcraton at different time.

5. Discussion The several workers considered that Bundelkhand massif is reworked crust which is formed

by multiple phases of acidic magmatism during the Archean to palaeoproterozoic times (Sharma 2000, Mondal et al., 2002, Basu ,2007, Mondal 2010, Pradhan et al., 2012). The geochronological studies (Crawford 1970, Sarkar et al., 1996 and Mondal et al., 1998) and detailed field relationship in Bundelkhand massif established at least five major events of magmatism (Early to middle ArcheanGrantoids and TTG, volcanism associated with greenstone belt, Late ArcheanBundelkhandgranitoids, Upper proterozoic event of quartz reefs and associated magmatism and Mafic dykes and swarms) were involved in the crustal growth of massif. Among all these, Late Archean to Palaeoproterozoic magmatic event known as Bundelkhandgranitoids was very prominent while the mafic and felsic magmatism associated with greenstone belt of Bundelkhand is least studies. Recently Singh (2011) pointed out that the Bundelkhand massif consist two events of metamorphism viz (i) high-grade metamorphics known as BnGC and low grade metamorphites (BnMM) in the

0 . 0 1

0 . 1

1

1 0

1 0 0

1 0 0 0

1 0 0 0 0

R b B a T h U K N b S r P T i Y

P M -7 4P M -1 0 7P M -5 4P M -9 3P M -8 4K TX

M E T A - V O L C A N IC S

1

10

100

1000

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

KT-X

Pm-84

PM-93

PM-54

PM-107

PM-74

b

a


29

central part of Bundelkhand massif and also opined that both the events are Archean in age. Based on the detailed structural and petrological works Singh, et al,(2007) pointed out that metavolcanics in central part of massif received low grade metamorphism before the Late Archeangranitoid.

The geochemical studies of the felsic rocks based on the different bivariant diagrams of total alkali (Na2O + K2O) vs SiO2 is consistent with the other proposed diagrams. K2O vs Na2O (Innocenti et al., 1982) and Zr/TiO2vs SiO2 (Winchester and Floyd, 1977) attributes that the felsic volcanics plot in the field of Rhyolite and Rhyodacite to dacite. The MgOvsCaO and Feo/(FeO+MgO) vs Al2O3 point that initially the magma was enriched with mafic phase component. The hornblende and plagioclase were crystallized and fractionated from the mafic parent magma and finally the felsic magma enriched by rhyolitic composition.

The geochemical data for felsic member show a distinct trend in the Harker’s variation diagram; when TiO2, CaO, P2O5 and Fe2O3 values were plotted against SiO2. The variation diagrams indicate that silica content increases with decreasing mafic phase component. The Alkali Index [(Na2O + K2O)/ (SiO2-43) X 0.17] vs Al2O3 and Na2O vs K2O variation diagram also suggest the enrichment of felsic phase component at the late stage.

The chondrite normalized REE plot for the felsic of metavolcanic in Fig9 indicate an enrichment of LREE and show a prominent Eu negative anomaly trend. The felsic rocks have varying concentration of total REE. The high LREE/HREE fractionation is reflected in the CeN/YbN ratio ranges 9 to 13. Due to consistent similarity of trend for REE trend an in spider diagram (after Sun et al., 1989) it can be concluded that felsic magma has undergone a similar type plagioclase fractionation. Since the metavolcanics have broadly similar REE pattern and trace element signatures support the petrogenetic modal that felsic magmatism would have achieved from fractionation of mafic magma. Therefore plagioclase and hornblende fractionation have taken place during the magmatic differentiation which is evident by a distinct negative Eu anomaly (Fig. 9). The constant incompatible element ratio precludes the formation of felsic member by assimilation of crustal rocks and suggests that they were most probably related to crystallization of parent mafic magma.

Late Archeangranitoids of Bundelkhand are supposed to be the part of arc type geological setup ( Mondal, 2010 and Mondel et al., 2002). Based on the presence of crustal component of Sr, Nd and Pb isotopes composition in the source of granite and andesite and their initial ratios of Rb/Sr arc related geological set up of Bundelkhand massif is proposed for both (Pandey et al., 2010). The presence of rhyolite/andesite xenoliths in biotite granites near Dhaura village and intrusion of granitoids into rhyolites (Fig.2) also demonstrate that felsic volcanism is older event than Bundelkhandgranitoids. The view is also supported by Rb-Sr whole rock isochron age of 2409+ 80 Ma for the Bundelkhandgranitoids of Mohar area and Rb/Sr age of 2510+ 280 Ma and Pb/Pb age of 2622+300 Ma for the andesites of felsic near Mohar which points out that felsic volcanic is older than Bundelkhandgranitoid (Pandey et al., 2010). The different discrimination diagrams for trace, major and REE suggest an island arc tectonic environment is most suitable configuration for the felsic magmatism of BnMM. Thus the present work established that felsic magmatism in the Bundelkhandcraton was active before the Palaeoproterozoicganitisation in the island arc tectonic environment in the central part of massif.

6. Conclusions 1. The metavolcanic rocks in the central part of Bundelkhand massif represent two major suits

with distinct petrochemical characteristics. Discrete calc-alkaline volcanism composed predominantly of andesite and rhyodacite were formed during the development of a major volcanosedimentary basin and were erupted contemporaneously with tholeiite basalt.

2. A feature of the stratigraphic model is the cyclicity of magmatism which begins with ultramafic-mafic rocks, progresses through intermediate (andesite) and felsic (rhyodacite) composition and ended with a rhyolite and granitoid porphyries event.


30

3. The volume of felsic magma erupted and dispersed to the sedimentary basin during the felsic volcanic event was several times larger than the volume of metasedimentary and equal to or larger than the volume of preserved mafic metavolcanics. The volcanism was thus bimodal, producing basalt and rhyodacite + rhyolite. The high silicic component implies a thick crust that presumably developed by extensive felsic volcanism loading the Archean crust.

4. The calc-alkaline melts were derived by shallow, hydrous partial melting of LIL enriched mantle; Y and HREE depleted, Sr enriched volcanic rocks, Rhyolite enriched in Zr, Nb, Y and HREE was deposited in a linear trough in the central tectonic zone.

5. The rhyolite associated andesite is considered to have formed by the fractionation of an intermediate parent. A crustal source, tapped during the initial phase of a period of increased crustal extension, is considered most likely.

Acknowledgement: The Ministry of Mines Governement of India is acknowledged to provide financial support.

References Ahmad, T. and Tarney (1994): Geochemistry and petrogenesis of the Late ArcheanAravallivolcanics

basement enclaves and granitoids Rajasthan. Precam.Research, V. 65, pp.1-23.

Balmik, P. (1990): Observations on the Precambrian geology of central India vis-à-vis adjoining region. G.S.I. Spl. Pub. No. 28, pp. 181-198.

Basu, A.K., (1986): Geology of parts of the Bundelkhand Granite Massif. Rec. Geol. Surv. Ind., V. 117 (2), pp. 61-124.

Basu, A.K., (2007). Role of the Bundelkhand Granite Massif and the Son-Narmada megafault in Precambrian crustal evolution and tectonism in Central and Western India.J. Geol. Society India.Spl v.70, pp.745-770.

Chadwick, B.Vasudeo, N. N. and Hegde, G. V. (2003): The Chitradurga schist belt and its adjacent plutonic rock NW of Tungabhadra, Karnataka. A duplex in Late Archean convergent setting and andDharwarcraton. Geol. Soc. Ind., V.61, pp. 645-663.

Crawford, A. R. (1970): The Precambrian geochronology of Rajasthan and Bundelkhand, Northern India. Can. J. Earth. Sci., V. 7, pp. 91-110.

Harker, A. (1909): The natural history of igneous rocks. Methuen, London, pp. 384.

Harmon, R. S. Halliday, A. N. Clayburn, J. A. P. and Stephens, W. E. (1984): Chemical and isotopic systematics of the Caledonian intrusions of Scotland and northern England : A guide to the magma source region and magma-crust interaction: Philos. Trans. Roy. Soc. (London) Series, A, V. 310, pp. 709-742.

Harris, N. B. W. Santosh, M. and Tylor, P. N. (1994): Crustal evolution in south India: constraints from Nd isotopes. Jour. Geol., 102, 139-150.

Jain, S. C. Gaur, V. P. Srivastava, S. K. Nambiar, K. V. and Saxena, G. P. (2001): Recent find of a Cauldron structure in Bundelkhandcraton. Geological.Surv. Ind., Pub. No. 64, pp. 289-329).

Le Bas, M. J. and Streckeisen, A. L. (1991): The IUGS systematics of igneous rocks. J. Geol. Soc. Lond., 148, pp. 825-833.

Maniar, P.D. and Piccoli, P.M. (1989): Tectonic discrimination of granitoids. Geol. Soc. Am. Bull., V. 101, pp. 635-643.

Martin, H. (1993): The mechanism of petrogenesis of Archean continental crust- comparison with modern processes. Lithos., V. 30, pp. 373-388.


31

Mondal, M.E.A., Sharma, K.K., Rahman, A., Goswami, J.N., (1998): Ion microprobe 207Pb/206Pb zircon ages for the gneisses-granitoids rocks from Bundelkhandmassif : Evidence for the Archean components. Curr. Sc., V. 74, pp. 70-75.

Mondal. M.E.A, Goswami, J.N., Deomurari, M.P. and Sharma, K.K. (2002): Ion microprobe 207Pb/206Pb ages of Zircons from the Bundelkhand massif, northern India, implications for crustal evolution of the Bundelkhand-Aravalli Proto Continent. Precambrian Research, V. 117, pp. 85-110.

Mondal; M.A.E. (2010) Geochemical evolution of the Archaean –PaleoproterozoicBundelkhandcraton, central Indian shield: RevisitedJournal of Economic Geology and Georesource Management; v. 7 No. (1-2), pp. 69-80.

Muller, J. E. (1980): Geochemistry and origin of Eocene Metchosinvolcanics Vancouver Island British Columbia. Can. J., Earth. Sc., V.17, pp. 199-209.

Naqvi, S. M. (2005): Geology and evolution of the Indian plate. Capital Publishing Company, New Delhi, India, pp. 450.

Pandey, U.K., Bhattacharya, D, Pandey, B.K. and Sastry, D.V.L.N. (2010) Geochronology (Rb-Sr, sm-Nd and Pb-Pb) of the magmatic activity around Moharcauldraon,Bundelkhand Granite Complex, Shivpuri district, MP India: Implication on the evolution of Cauldroun and Bundelkhand Granite Abstract vol. Geology and Mineral Resourses of BundelkhandCraton at Jhansi Page 26.

Pearce, J. A. (1982): Trace elements characteristics of lavas from destructive plate boundaries. In Andesites, RS. Thorpe (Ed), Jhon. Willy and Sons, New York. pp. 525-548.

Pearce, J.A., Harris, N.B.W. and Tindle, A.G. (1984): Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. Jour. Petrol, V.25, pp. 956-983.

Pearce, T. H. Gorman, B. E. and Birkett, T. C. (1975): The TiO2-K2O-P2O5 diagram: a method of discriminating between oceanic and nonoceanic basalts. Eath.Sci. Lett., 24, pp.419-426.

Pradhan, V. R., Meert, J. G., Pandit, M. K., Kamenov, G. and Mondal, M. E. A. (2011) Paleomagnetic and geochronologic studies of the mafic dyke swarms of Bundelkhandcraton, central India: Implications on tectonic evolution and paleogeographic reconstructions. Precam.Res.v. 198-199; pp. 51-56.

Prasad, M.H., Hakim, A., and Rao, B.K. (1999): Metavolcanic and metasedimentary inclusions in the Bundelkhand Granitic Complex in Tikamgarh District, Madhya Pradesh. Jour. Geol. Soc. Ind., V. 54, pp. 359-368.

Rogers, J.J.W., and Greenberg, J.K., (1990): Late-orogenic, Post-orogenic, and Anorogenic Granites: Distinction by Major-Element and Trace-Element and Chemistry and possible origins. Jour. Geol., V. 98, No.3, pp. 291-310.

Saha L. Pant NC, Pati JK, Berndt J, Bhattacharya A, and Satynarayanan M. 2010 Neoarchean high-pressure margarite-phengitic muscovite-chlorite corona mantled corundum in quartz-free high-Mg, Al phlogopite-chlorite schists from the Bundelkhandcraton, north central India. Contrib. Mineral. Petrol.DOI10.1007/ s00410-010-0546-7.

Sarkar, A., Paul, D.K., and Potts, P.J. (1996): Geochronology and geochemistry of the Mid-Archaeantrondhjemitic gneisses from the Bundelkhandcraton, Central India. Recent Researches in Geology, V.16, Ed. A.K. Saha, pp. 76-92.

Sharma, K.K., (2000): Evolution of ArcheanPalaeoproterozoic Crust of the BundelkhandCraton, Northern Indian Shield. Research Highlights in Earth System Science. D.S.T., Spl. V.1, (Eds. O.P Verma and T.M. Mahadevan) Indian Geological Congress, pp. 95-105

Singh S.P. (2011); Archean Geology of the BundelkhandCraton, India.GondReasearch (in press).

Singh, S. P. and. Dwivedi, S. B. (2009) Garnet–sillimanite–cordierite–quartz bearing assemblages


32

from early Archeansupracrustal rocks of Bundelkhand Massif, Central India Curr. Sc. v.

97, pp. 103-107.

Singh, S.P., and Singh, M. M., Srivastava, G.S., and Basu, A.K (2007) Crustal evolution in Bundelkhand area, Central India. J. Himalayan Geol.,v. 28 (2), 79-101.

Sun, S. S. and McDonough, W. F. (1989): Chemical and isotopic systematics of the oceanic basalts: Implication for mantle composition and processes. In Saunder, A. D. and Norry, M. J. (Ed): Magmatism in the oceanic basins, Blackwell Sc., Pub. No. 42, pp. 313-345.

Taylor, P. M. Chadwick, B. Moorbath, S. Ramkrishnan, M. and Viswanatha, M. V. (1984): Petrography, chemistry and isotope ages of Peninsular gneisses, Dharwar acidic volcanic rocks and Chitradurga granite with special reference to the Late-Archean evolution of Karnataka craton, South India. Precam.Res., V. 23, pp.375.

Winchester, J. A. and Floyed, P. A. (1977): Geochemical discrimination of different magma series and their differentiation product using immobile element. Chem. Geol., 20, 325-347.

Wood, D. A. Tarney, J. Varet, J. Sunders, A. D. Bougault, H. Joron, J. L. Treuil, M. K. and Cann, J. R. (1979): Geochemistry of Basalts drilled in the north Atlantic by IPOD leg 49: implications for the mantle heterogeneity: Earth Planet. Sci. Lett., V. 42, pp. 77-97.

Aes1105

Documents