JOURNAL GEOLOGICAL SOCIETY OF INDIA

Vol.94, August 2019, pp.117-138

Carbonatites of India
P. Krishnamurthy
Formerly Atomic Minerals Directorate for Exploration and Research (AMD), Department of Atomic Energy, Begumpet,
Hyderabad - 500 016, India
E-mail: krisviji @gmail.com

ABSTRACT evaluation of the radiometric anomalies located at Amba Dongar

Based on the field relations, associated rock types and age, the (Udas, 1965).
carbonatite-alkaline rock complexes of India, that are spatially The UNDP for mineral exploration in Tamil Nadu, led by UN
related to deep main faults, rifts and shear zones, have been experts like L. S. Borodin, Semenov, Franc Joubin and D. N. Holt
classified in to two major groups, namely: 1. Middle – late along with V. Gopal and his associates of the State Department of
Cretaceous, subvolcanic –volcanic complexes (Amba Dongar, Geology, Tamil Nadu, led to the discoveries of the Sevathur and
Siriwasan, Swangkre, Mer-Mundwara, Sarnu-Dandali-Kamthai) Samalpatti carbonatites associated with syenites and pyroxenites in
and 2. Paleo-Neoproterozoic plutonic complexes (Newania, 1966. T. Deans of the Institute of Geological Sciences, London,
Sevathur, Samalpatti, Hogenakal, Kollegal, Pakkanadu, visited these complexes during 1966 - 1967 and obtained Sr-isotopic
Udaiyapatti, Munnar, and Khambamettu). The middle Cretaceous data on carbonatites from Amba Dongar and other areas confirmed
Sung Valley and Samchampi complexes also belong to this these complexes as mantle-derived carbonatites (Deans and Powell,
plutonic group. Three minor associations, belonging to these 1968).
two age groups include, the Neoproterzoic, late stage veins of AMD’s exploration inputs, mainly radiometric surveys, to discover
carbonatites in peralkaline syenite complexes (e.g., Kunavaram, new resource bases of U, Th, rare metals (Li, Be, Nb, Ta and Zr) and
Elchuru), the diamond-bearing carbonatite and kimberlite at rare earths (La-Lu, Y and others) in various parts of India during the
Khaderpet and the lamprophyre-lamproite association (e.g., 1960s and 1970s led to numerous discoveries of carbonatites in India
Pachcham Is. Upper Cretaceous, Deccan Volcanic Province, and such as Newania in Rajasthan, Pakkanadu, Moolakadu, Jokkipatti,
the Proterozoic Chitrangi Group). Petrological associations Beldih, Mer-Mundwara, Sarnu-Dandali and Sung Valley in the 1970s
include carbonatite-nephelinite-phonolite (e.g. Amba Dongar, (see Table 1).
Sarnu-Dandali-Kamthai), dunite-peridotite-pyroxenite-ijolite- Reviews on tectonic settings of Indian carbonatites were provided
melilitite (e.g. Sung Valley), miaskitic syenite-pyroxenite ± dunite by Udas et al., (1974). The first review on carbonatites of India was
(e.g. Sevathur, Samalpatti, Pakkanadu), carbonatite alone with presented by Sukheswala and Viladkar (1978) at the First International
fenites (e.g. Newania), besides those minor associations mentioned Symposium on Carbonatites at Pocas de Caldas, at Brazil. Subsequent
above. Sovites (calico-carbonatites) occur as the most dominant reviews include those of Krishnamurthy (1988), Krishnamurthy (2008)
type in some ten (10) complexes. Beforsite (magnesio-carbonatite) and Viladkar (2001).
is the dominant type at Newania and ankeritic-sideritic types The 1990s and subsequent decades in the new millennium saw a
are mainly found at Amba Dongar, Siriwasan and Newania. paradigm shift in the studies and publication of isotopic and trace
The rare benstonite-bearing carbonatites are found at element data, including the whole range of REE on many Indian
Jokkipatti and Udaiyapatti in Tamil Nadu. Mineralogically carbonatites especially through project work and also international
and chemically the carbonatites show considerable diversity. collaborative efforts with a number of Universities from Brazil, Canada,
Fenitised zones and types of fenites (Na, K and mixed) vary Czech Republic, China, Germany, Italy, Russia, UK and USA , notably
widely since the carbonatites are emplaced in a variety of host- by S. G. Viladkar of St. Xavier’s College, Mumbai and R. K. Srivastava,
rocks ranging from granitic, mafic, ultramafic, charnockitic types Department of Geology, Benares Hindu University, Varanasi. The
besides basalts and sandstones. Stable (δ δ13C and δ 18O) and present review provides an overview on the current status of knowledge
radiogenic (Sr, Nd and Pb) isotopes clearly indicate their mantle on carbonatites of India in the light of advancements made on
origin and also the diverse types of sources (both depleted HIMU carbonatites both in India and the world over in the new millennia.
and enriched EM 1 and 2). Petrogenetic considerations reveal
three types of carbonatites, namely direct partial melts from MAJOR STURUCTURES AND SPATIAL RELATIONS OF
metasomatised mantle (e.g. Newania), liquid immiscibility from CARBONATITES OF INDIA
carbonatite-nephelinite association (e.g. Amba Dongar) and Carbonatite-alkaline rock complexes of India, as elsewhere in the
through fractionation of ultra-alkaline ultramafic and mafic world, show an apparent spatial relation to fairly well defined structural
association (e.g. Sung Valley). Carbonatites of India that host domains such as rifts, deep faults and terrain boundaries. Following
significant resources include Amba Dongar (Fluorite, REE, Udas et al. (1974), Krishnamurthy (1988) and Srivastava and Hall
Nb, P, Ba, Sr), Kamthai (REE), Sevathur (Nb, P, vermiculite), (1995), six major structural domains for the emplacement of
Beldih (P, Fe), Sung Valley (P, Nb, REE, Fe) and Samchampi carbonatites of India have been recognised (Figure 1) and these will
(P, Nb, Fe, REE). be briefly considered in the following section.

INTRODUCTION Eastern Ghat Mobile belt (EGMB) and the Southern Granulite
The Amba Dongar, carbonatite-nephelinite association, as part Terrain (SGT) and the Carbonatites of Andhra Pradesh (AP),
of the Upper Cretaceous, Deccan Volcanic Province (DVP), was Northern Tamil Nadu (NTN), and Kerala.
the first carbonatite complex discovered in India by Sukheswala and The EGMB trends NE-SW along the eastern India coast in AP
Udas (1963). This discovery came as a sequel to AMD’s detailed and Odhisa (see Figure 2 inset) and swerves to ENE-WSW in NTN.

0016-7622/2019-94-2-117/$ 1.00 © GEOL. SOC. INDIA | DOI: 10.1007/s12594-019-1281-y

 
Fig.1. Carbonatites of India along with major structures. Index to Numbers. 1. Amba Dongar and Siriwasan 2. Newania 3. Sevathur 4.
Samalpatti 5. Pakkanadu 6. Hogenakal 7. Khaderpet 8. Eluchuru 9. Kunavaram 10. Mer-Mundwara 11. Sarnu-Dandali-Kamthai 12. Sung
Valley 13. Munnar 14. Khambamettu 15. Swangkre 16. Kollegal 17. Udaiyapatti-Chhinnagoundan Palayam 18. Samchampi-Samteran 19.
Beldih-Kutni 20. Chhaktalo 21. Mahdawa and others 22. Hingoria 23. Pascham Is. 24. Chitrangi 25. Ariyalur 26. Murud-Janjira.
References to numbers given in Table 1. I Eastern Ghat Mobile Belt; II Narmada; III Aravalli; IV Assam-Meghalya V Western Ghat faults ; VI
Cuddapah-Godavari rift (Modified after Udas et al., 1974; Krishnamurthy, 1988; Srivastava and Hall, 1998). F – F Charnockite - non-charnockite
boundary of Fermor (1936). CMB - Charnockite mobile belt. EPSZ, Erinpura shear zone; PSZ, Phulad shear zone; KSZ, Kaligumon shear
zone; DSZ, Delwara shear zone; SNNF, Son-Narmada Northern fault; SP, South Purulia shear zone.

They contain the high-grade granulite facies rocks comprising of the the migmatites and charnockites along the break-in slope that
charnockite series, the khondalites and granite gneisses. They occur follows the Kerala-Tamil Nadu border, hosts the Munnar
to the south and southeast of the charnockite-noncharnockite boundary and Khambamettu alkaline carbonatite complex (KAC) which occur
of Fermor (1936), later recognised as the Dharwar craton-charnockite at the intersection of NNW-SSE (Achankoil shear) and NE-SW
mobile belt boundary (CCMB) in southern India (Ramakrishnan and structures (and includes four separate intrusive phases, namely:
Vaidyanadhan, 2008). The boundary between the belt has been 1. Syenite-quartz-monzonite as the first phase, 2. Pyroxenite
established as a broad zone of intense faulting, shearing and thrusting 3. carbonatite and 4. Syenite, the final phase. Among the felsic units,
in which the charnockite terrain had been uplifted and over-thrusted medium to very coarse grained, pinkish, quartz monzonite is the
on to the craton (Radhakrishna, 1968). This zone, along with the dominant rock unit (Renjit et al., 2016 and references therein).
Narmada-Son belt, has also been recognised recently as an important
Proterozoic orogen in the Indian sub-continent with numerous Narmada-Son Rift Zone
occurrences of syenite and carbonatite-alkaline rock complexes The E-W to ENE-WSW trending Narmada–Son suture or rift
(Leelanandam et al. 2006; Chetty, 2017; see Figure 1). It can be seen zone has been recognised as a major tectonic lineament of great
that the belt of syenite dominated carbonatite complexes in NTN (Nos. significance in Indian geology (Crawford, 1978; Murthy and Mishra,
1-6) and in AP (Nos. 8-12) are confined to this belt. Based on DSS 1981; Naidu, 2012 and references therein). The Amba Dongar and the
and reflections in the zone between 34-46 km below the craton, the Siriwasan carbonatite complexes occur about 5-8 km to the north of
boundary between these two provinces has been considered as a the Narmada rift. The eastern continuity of the NSRZ continues to
suture/ volcanic arc involving subduction of the northern, cratonic the ENE and splays in to the NSNF zone and the NSSF zone, the
plate dipping to south (Vijaya Rao et al., 2016). latter forming the southern boundary of the Chhota Nagpur gneissic
complex. Along this or in close proximity to its south the Beldhi
Western Ghat Faults carbonatite is located besides Kutni and others. This structure seems
The NNW-trending faults in the Khambametu foot hills, within to continue further east across the Bengal basin and join the major

118 JOUR.GEOL.SOC.INDIA, VOL.94, AUGUST 2019

 constitutes a major structural feature south of the Narmada-
Son rift zone. The north- and south Purulia shear zone
south of the Chhota Nagpur granite gneissic complex
(CNGNC) and north of the Singhbhum craton forms a
major structural feature. The Beldi-Kutni carbonatite (also
known as Purulia carbonatite) hosts rich apatite deposits
that occur along the northern shear (Ramakrishnan and
Vaidyanadhan, 2008).

CARBONATITE TYPES
Petrological Associations and Grouping of Carbonatites
of India
Based on the field relations and associated rock types,
the carbonatite-alkaline rock complexes of India can be
classified into two major groups, namely subvolcanic-
volcanic and plutonic types (see Table 1). The rare, kimberlite-
lamproite-carbonatite association and the lamprophyre-
carbonatite association are also included in these groups.
Some potential areas, based on existing data, for locating
possible carbonatite bodies (both surface and sub-
surface) are also indicated in the Figure 1 and listed in the
 Table 1.
Fig.2. Structural relations of the carbonatites of Tamil Nadu along the Koratti
fault zone indicating the syenite and dunite plugs with spatially related carbonatites Classification and Nomenclature of Carbonatite Types
(after Borodin et al., 1971 and Grady, 1971). The Udaiyapatti carbonatite is located Carbonatites are defined in the IUGS system of
c. 10 km from Salem. The inset indicates the the Eastern Ghat mobile belt (EGMB) classification as igneous rocks composed of more than 50
and the alkaline complexes in them as also in the Southern Granulite Terrain modal per cent primary carbonate (sensu lato) and less than
20 wt.% SiO2 (Le Maître, 2002). Based on the CaO - MgO -
(SGT). F-F as in Figure 1. EDC – Eastern Dharwar Craton. (Modified after
(FeO + Fe2O3 + MnO) plot, three main types, namely calcio-
Krishnamurthy, 1988, Fig. 12).
(sovite), magnesio-(beforsite) and ferro- have also been
recognised. The relative abundances of the three main types
faults along the southern Meghalaya plateau and continues further of carbonatites from the different complexes of India are shown in
in to Assam. Figure 3.

Arvalli Rift and Related Structures in Rajasthan Silico-carbonatites vs. Siliceous Carbonatites
In the north-western part of India, in Rajasthan, several major The term silico-carbonatite was coined by Brogger (1921) for
lineaments and fault/shear zone have been recognised (Chetty, 2017 carbonatites that contain silicate minerals such as phlogopite,
and references therein). These include, from NW to SE, the EPSZ, pyroxene, ampbhibole and others. The term, however, has been used
PSZ, KSZ and the DSZ (see Figure 1) and the carbonatites (Nos.2, 10 by Srivastava (1997, 1998), especially for the SiO2-rich samples of
and 11) appear to be related to them. The NW-SE trending Jaisalmer - carbonatites from both the Samalpatti and Amba Dongar carbonatite
Barwani Lineament also appears to be related the Sarnu-Dandali- complex. The Amba Dongar samples, especially the brecciated and
Kamthai carbonatite bodies. tuffaceous types, termed as silico-carbonatites by Srivastava (1997)
appear to be silicified by hydrothermal solutions carrying Si, F, Ba
Assam-Meghalaya Plateau and others. They contain anhedral quartz (greater than 10% and
The Assam–Meghalaya plateau is considered to be an uplifted other rock fragments) including cherty silica (c.f. Srivastava, 1997;
horst-like structure bordered by the Dauki fault to the south and the Figure 5a and Table 2). In all probability they are members of the
Brahmaputra trough zone to the north. The development of these silicified carbonatite suite. Recent studies on the carbonatites of
structures was largely related to the northward migration of India after Samalpatti area had also indicated that these anomalous, SiO2-rich
the fragmentation of the Gondwana land and its subsequent collision carbonatite types with very low abundances of REE, Y, Ba, Sr, Nb
with the Asian continent during Jurassic-Cretaceous and the Cenozoic and P have been explained as contaminated types from crustal
period (Evans, 1964; Desikachar, 1974; Balakrishnan et al., 2009). sources including siliceous skarns (Schleicher et al., 1998; Vladykin
The Sung Valley, Swangkre, Samchampi and the Barpung alkaline et al., 2008; Ackerman et al., 2017). Thus this aspect of silico- and
complexes, with carbonatites (except Barpung) occur spatially close silicified- carbonatites must be made clear in carbonatite complexes
to large number of lineaments and fractures either along them or at of India.
the intersection of such lineaments (see Figure 1). There is also a
suggestion from the spatial disposition of the carbonatites of Meghalaya PETROGRAPHY AND MINERALOGY
and Assam that they are also in structural continuity of the major Petrographic and mineralogical studies constitute an important
Narmda-Son lineament and its easterly extension. aspect in understanding the evolution of the different carbonatite types
from a given complex and also help in elucidating their genetic relation
Central Indian Suture (CIS) and the North Singhbhum Mobile to the associated alkaline-silicate rocks (Heinrich, 1966; Kapustin,
Belt (NSMB) 1980). Recent studies have further emphasized the need to study in
The central Indian suture (CIS) along the northern boundary of detail the petrographic and mineralogical aspects since they have an
the Dongargarh Supergroup and its easterly continuity in the NSMB important bearing on understanding the mineralisations that are

JOUR.GEOL.SOC.INDIA, VOL.94, AUGUST 2019 119

 Table 1. Summary of Carbonatites of India*

Carbonatite complex and age** Associated rock types and emplacement sequence References

Group 1. Subvolcanic – volcanic complexes:

1. Amba Dongar, Baroda Dt., Gujarat Nephelinite-phonolite; earliest phase of nephelinite and phonolite Sukheswala and Udas, 1963; Viladkar, 1981,;
(Figure 1.1) plugs followed by carbonatite breccia, intruded in turn by the 1986, 2012, 2018; Viladkar and Dulski, 1986;
65.0±0.3 40Ar-39Ar sovite ring-dyke. Ankeritic carb. plugs intrude the sovite ring; Srivastava, 1997; Gwalani et al. 1993;
(Ray and Pande, 1999) K-, Na-K & Na-fenite well developed in the nephelinite and Simmoneti et al., 1995; Doroshkevich et al.,
sandstone xenoliths. Hydrothermal fluorite and silicification 2009; Ray and Shukla, 2004;
1a. Siriwasan- Nakal, Baroda Dt., 11 km long sill of carbonatite breccia (intruding the Bagh Sukheswala and Avasia, 1972; Sukheswala and
Gujarat (Figure 1.1a) sandstone) with pockets of aegirine sovite; tinguaite, Borges, 1975; Sethna and Borges, 1980; Viladkar
70±Ma ; Pb-Pb (Veena Krishna, 2000) trachyte; sodic fenites and Avasia, 1995; Viladkar and Gittins, 2016;
10. Mer-Mundwara, Sirohi Dt., Rajasthan. Theralite, melteigite, pyroxenite, syenite with veins of Subramaniam and Rao, 1972; 1977; Chakraborty
68.53±0.16 40Ar-39Ar (Basu et al., 1993) carbonatite (sovite) in pyroxenite and gabbro and Bose, 1978; Narayan Das et al., 1982;
80-84 Ma and 102 - 110 Ma from associated rocks
(Pandey et al., 2016)
11. Sarnu-Dandali- Kamthai, Barmer Dt., Melanephelinite-alkali pyroxenite-melteigite-ijolite-teschenite, Narayan Das et al., 1978; Chandrasekaran et al.,
Rajasthan. tinguaite and phonolite dykes along with carbonatite dykes 1990; Chandrasekaran and Srivaastava, 1992;
68.57±0.08 40Ar-39Ar (Basu et al., 1993) (alvikites and ferrocarbonatite) and veins. Bhushan and Chandrasekaran, 2002;
66.3±0.4 Ma (Sheth et al., 2017)
15. Swangre- Jasra, West Khasi Hills, Dt., Veins of carbonatite in gabbro and granite Nambiar and Golani, 1985;
Meghalaya.
105.2±0.5 Ma U-Pb, (Heaman et al., 2002)
20. Chhaktalo, Jabua Dt., Madhya Pradesh. Carbonate-rich rocksat Chaktalo occur as E-W trending dyke- Hari et al., 1998; Khandelwal et al., 1997;
Khatarkehda and Bakhatgargh are localities in like bodies within the Deccan ‘basalts and show a structurally Note: Trace element concentrations are low
adjoining areas of Jabua and Dhar Dts., of controlled mode of emplacement. Modal composition shows compared to average carbonatites (see Table 4).
Madhya Pradesh. calcite as the dominant mineral ( c. 90%). Ankerite, apatite, Some of the δ13C - 1.74 to -2.8 ‰) and δ18O
altered olivine, augite and opaques account for the remaining (+ 12.75 to + 13.35‰) fall within the “igneous
percentage. carbonatites”. Xenoliths of ‘basaltic andesite’ in
which the andesine is altered to calcite (c.f. Hari
et al., 1998, p.591)
21. Mahdawa and others, south of Narmada, E-W to ENE-WSW trending (c. 10 to 100 m thick) dykes of Sant et al., 1991
Dhulia Dt., Maharashtra alvikitic carbonatites, variably silicified and ferruginated with
xenoliths of fine-grained porphyritic nepbelinite and basalt.
22. Hingoria, Baroda Dt., Gujarat Calcite-ankerite-fluorite veins within basalts. Also calcite–dykes Udas and Krishnamurthy, 1968;
trending ENE-WSW as part of a potassic alkali suite of Rajpipla. Krishnamurthy and Cox, 1980;
Lacks the diagnostic suite of carbonatite-type trace elements.

Group 2. Plutonic Complexes

2. Newania, Udaipur Dt., Rajasthan Dolomitic carbonatite with minor sideritic types; sodic Dhar (1964); Phadke and Jhingran, 1968;
(a) 2273±13 (a) Dolomite carbonatite fenites after Untala granite gneiss. Viladkar and Wimmenauer, 1986;
(b) 1551±46 (b) Ankerite carbonatite Viladkar, 1981, 1998; Viladkar et al., 2017;
(Schleicher et al., 1997; Ray et al. 2003) (Fig.1.2) Doroshkevich et al., 2010;
3. Sevathur, Dharmapuri Dt., Tamil Nadu Pyroxenite-syenite-carbonatite; potassic syenite pluton with Borodin et al., 1971; Krishnamurthy, 1977;
(Figure 1.3) minor pyroxenite intruded by sovite and dolomite carbonatite in Subramanian et al., 1978; Viladkar and
(a) 767±8 / Rb-Sr isochron (syenites); (Anil Kumar the NW periphery as minor cone sheets?; enitised pyroxenites Subramanian, 1995; Saravanan and
and Gopalan, K., 1991; Anil Kumar et al., 1998) with development of vermiculite in feconomic concentrations Ramaswamy, 1975; Schleicher et al., 1998
(b) 801±11 / Pb-Pb isochron(ankerite carbonatite; and also Na- and K-fenites. Elagiri ring-complex, north of Ramaswamy, 2018; Schleicher, 2019;
(Schleicher et al., 1997) Sevathur contains small lens like bodies of sovite, intrusive
(c) Rb-Sr isochron (syenite+pyroxenite). into leuco-syenite and hornblende gabbro. Mukopadhyaya et al. 2011;
(Miyazaki et al., 2001) Semenov et al., 1978;
4. Samalpatti complex (incudes Jokipatti, Syenite pluton with an incomplete pyroxenite ring and minor Udas and Krishnamurthy, 1970; Borodin et al.,
Pallasullakarai, Redipatti and Karappattu), dunite bodies. Arcuate, discontinuous, carbonatite bands (soviet, 1971; Subramaniam et al., 1978; Viladkar and
Dharmapuri Dt., Tamil Nadu. (Figure 1.4). dolomitic and silico-carbonatite types) within pyroxenite and Subramanian, 1995; Srivastava, 1998;
Jogipatti 700±30 Ma / K-Ar of phlogopite; gneisses. Vladykin et al., 2008; Akerman et al., 2016;
(Moralev et al., 1975)
5. Pakkanadu-Mulakadu, Dharmapuri Dt., Syenite pluton with subordinate dunite and pyroxenite. Rao et al., 1978; Pandit et al., 2002; 2016;
Tamil Nadu. Carbonatite (sovite) veins and bands, often contorted enclosed in
(a) 771±2 & 599±30 K-Ar of phlogopites pyroxenite. Large crystals of allanite and monazite in pyroxenites
from Carbonatite; (Moralev et al., 1975) (fenitised?)
6. Hogenakal, Dharmapuri Dt., Tamil Nadu. Carbonatite (sovite and silico-carbonatites) and pyroxenite with Srinivasan, 1977; Natarajan et al., 1994;
2436 ± 154 Sm-Nd isochron WR (Anil Kumar minor syenite. At Hogenakal, carbonatites occur in the form
et al., 1998; Pandit et al., 2002; 2016) of lenses and veins (c. 30-800 m long and 3-50 m wide) within
two N-S trending linear bands of mixed rock consisting of
pyroxenite and syenite emplaced within charnockitic gneisses.
Eighteen such lenses of carbonatites were observed.
16. Ajjipura-Kollegal,* Mysore Dt., Karnataka Several lensoidal bodies of carbonatite in the granulite Ramakrishnan et al., 1973; Anantharamu
terrain,emplaced along deep NNE-SSW fracture system et al., 1995;
associated with pyroxenite, talc-tremolite schist which show
varying degree of fenitisation. The sovite and beforsite
varieties show high percentage of SiO2 due to contamination
during emplacement.

120 JOUR.GEOL.SOC.INDIA, VOL.94, AUGUST 2019

Table 1. Contd....

Carbonatite complex and age** Associated rock types and emplacement sequence References
12. Sung Valley, Jaintia Hills Dt., Meghalaya. Alkali pyroxenite, peridotite, dunite, ijolite./mellilotite, Chattopadhyay and Hashmi, 1984; Krishnamurthy,
(Figure 1.12) ne-syenite and cone-sheet/or dyke- like bodies of carbonatite 1985;Viladkar et al., 1994; Sheik Yusuf and
(a) 107.2 ±0.8/ 40Ar-39Ar (phlogopite from within pyroxente. Apatite-magnetite bands or pockets along Saraswat, 1977; Srivastava et al., 2005; 2019;
carbonatite and a WR pyroxenite) (Ray et al., 1999) with Na and K fenites after pyroxenites. Complex emplaced Melluso et al., 2005; Sadiq et al. 2014;
(b) 106±11 / Rb-Sr isochron (carbonatite and into the Proterozoic quartizes and gneisses of Shillong
pyroxenite WR and phlogopite from carbonatite) Series
(Ray et al., 2000)
18. Samchampi, Karbi-Anglong Dt., Assam. Syenite and syenitic fenite in the core of the complex Dhrendra Kumar et al. 1989; Nag etal. 1993;
~105 K-Ar of lamprophyres (Sarkar et al., 1996) (c. 60% ) into which, perovskite and Ti-magnetite-bearing Saha et al. 2010; Saha et al., 2017; Hoda and
bodies have been emplaced. Ijolite-melteigite-pyroxenite in Krishnamurthy, 2014, 20162017;
the northern part as incomplete arcuate ring? Secondary
phosphatic rock bodies along the SE and E periphery of the
complex. Carbonatites of varied dimensions.
17. Udaiyapatti-Chhinnagoundan Palayam, Calcite-ankerite-benstonite bearing carbonatite veins within Senthil Kumar et al., 2001, 2003;
Salem Dt., Tamil Nadu charnockites and gneisses
19. Beldih (Purulia carbonatite), Purulia Dt., Subsurface veins of carbonatite from bore holes at Kutni Basu, 1993; Chakrabarty and Sen, 2010;
Paschim Bengal. and Medinitanr Basu and Bhattacharya, 2014;
748±24 Ma from pyrochlore in a Ne-syenite by Carbonatite, alkali pyroxenite- apatite-magnetite rock within Singh et al., 1977;
EPMA (Basu and Bhattacharya, 2014) phyllites and schists. Apatite rich -carbonatite (sovite) bodies
emplaced amidst the above rocks. Sushina alkali syenite
gneiss occurs spatially close by.

Group 2. Plutonic: Carbonatites as Minor Veins and Dykes within Syenite/Ne-syenite /Alkali Granite Complexes

8. Elchuru,* Prakasam Dt., Andhra Pradesh. Alkali granite, syenite and veins of carbonatite Rao, 1976; Bose et al., 1976; Ratnakar and
Leelanandam, 1989;
9. Kunavaram,* Khammam Dt., Andhra Pradesh Nepheline syenite, syenite with veins of carbonatite Sharma et al., 1971; Bose et al., 1976
13. Munnar,* Central Kerala Alkali granite and syenite with veins and patches of carbonatite? Nair et al., 1984; Santhos et al., 1987;
14. Khambamettu,* Madurai Dt., Tamil Nadu; Carbonatite, qz-monzonite, syenite, pyroxenite Balakrishnan et al., 1985; Burtseva et al., 2013;
2410 Ma; (Renjith et al. 2016) Renjith et al., 2016;

Carbonatite-Kimberlite-Lamproite Association

7. Khaderpet pipe, Anumpalle cluster of the A an unusual diamondiferous carbonatite-kimberlite clan rock Smith et al. 2013;
Wajrakarur kimberlite field, Cuddapah Dt., (clast-supported lithic breccia and crystal lithic tuff/ alnoite
Andhra Pradesh. or aillikite -like.). The sovite phase has up to 95% calcite, with
mineralogical gradations from an olivine-rich ultramafic to a
calcite-dominant rock resembling pure carbonatite. Diamonds
recovered from both the carbonatite and kimberlite phases after
caustic fusion have similar morphology.
24. Chitrangi Region, Mahakoshal Carbonate ocellae in aillikite Srivastava, 2013;
Supracrustal belt, Uttar Pradesh
23. Pachcham Islands, Northern Kutch, Camptonite dyke contains kaersutite phenocrysts that contain Ray et al. 2014;
Gujarat immiscible melt/glass phases as melt inclusions of two types –
calciocarbonatite and alkaline silicate melts.
25. Ariyalur, Tiruchirapalli Dt., Tamil Nadu Suspected, based on higher abundances of Ba, F, Sr in the Grady, 1971;
soils of phosphatic nodules
26. Murud-Janjira, Ratnagiri Dt., Maharashtra N-S trending (c.1 km x c.100 – 200 m ) dyke/stock-like body Sethna and Christopher D’sa. 1991;
of ijolite, (grading at places to melteigite to pyroxenite in local
patches) with veinlets of calcite ( < 1 cm in thickness) which
in thin sections show distinct association of calcite with augite.
Accessory amounts of perovskite (?), pyrochlore (?) occur as
tiny inclusions in grains of pyroxene. Iron oxide is fairly
ubiquitous. A nepheline syenite dyke ‘occurs close to the
northern portion of the ijolite

*Numbers refer to the localities shown in Figure 1. **Age data from Ray and Ramesh (2006, Table 1, p.20) and others as indicated.

associated with carbonatite complexes, especially those related to the Mineral orientation due to flowage is another important feature
main phase as also during fenitisation and the later hydrothermal shown by several Indian carbonatites, both at the outcrop and in thin
stage (Elliot et al., 2018 and references therein). sections, especially Amba Dongar, Sevathur, Sung Valley and others
(Viladkar, 1981; Krishnamurthy, 1977; 1985; 1988; Sesha Sai and
Petrography and Structures Sengupta, 2017)
Heterogeneity is one of the main petrographic features of the
carbonatites, both in terms of flow structure, texture and modal Mineralogy
mineralogy. Usually, several thin sections have to be studied for Reviews on the mineralogy of carbonatites have been provided by
discerning the accessory or minor minerals. Mineral banding and Heinrich (1966) and Kapustin (1980). The mineralogy of the different
clustering are common features, usually resulting from the distribution carbonatites of India are summarised in Table 2. It can be seen that
of apatite, magnetite, phlogopite, aegirine-augite, pyrochlore either the group as a whole shows the maximum diversity in terms of
alone or in combination of size and quantity. minerals contained in a single igneous rock type.

JOUR.GEOL.SOC.INDIA, VOL.94, AUGUST 2019 121

 


Fig.1.1. Geological map of Amba Dongar carbonatite complex. (Viladkar, Fig.1.2. Geological map of Newania carbonatite complex (after
1981, modified after Udas, 1965). Viladkar, 1981).

Fig.1.3. Geological map of Sevathur. 


Fig.1.12. Geological map of the Sung Valley ultramafic–alkaline–carbonatite complex
(Srivatava et al., 2005 after Krishnamurthy, 1985). Nepheline syenite and melilitolites dykes
exposed around the villages Sung and Maskut are very small, hence not indicated in the

map.
Fig.1.4. Geological map of Samalpatti

122 JOUR.GEOL.SOC.INDIA, VOL.94, AUGUST 2019

 Table 2. Summary of mineralogy of carbonatites of India

Carbonates 1 3 4 5 16 2 10 12 14 19 11 15 18 13 20 9

Calcite E E E E E M E E E E E E E E E E
Dolomite M E E M E M E M M M
Siderite E M M E
Ankerite E E M M E M E
Benstonite M M-R E
Rhodochrosite M
Strontianite Tr M M
Magnesite

Oxides
Magnetite M M M M M M M M M M M M M
Hematite M M M M
Ilmenite M M M M
Rutile S
Ilmeno-rutile M M
Goethite M
Spinel S M
Perovskite R R

Silcates
Olivine M M M M M
Diopside M M M M M M
Aegirine-augite M M M M M M M
Acmite M
Arfvedsonite M M
Riebeckite M M M M
Ritcherite M M
Eckermanite M
Phlogopite M M M M M M M M M M M M
Biotite M M M M M M M M M M M
Muscovite M
Vermiculite M M
Sphene S S M M M A M M
Zircon S S M M
Zirconalite M
Allanite M M M
Albite R
Orthoclase M M R
Epidote M
Chlorite A
Ti-clinohumite M M
Humite M

Phosphates
Apatite M M M M M M M M M M M R M R M
Monazite M M M M M A M

Halides/Sulphates
Fluorite E
Barite E M M M E M M
Celestite M M
Anhydrite M
Cerite R?
Strengite M

Sulphides
Pyrite R R R R
Pyrrhotite R R R R M
Chalcopyrite R R R M R
Galena R R R R
Molybdenite

REE, U, Th, Nb, Ta minerals

Bastnaesite M M-R R
Fersmite Tr Tr Tr
Eschynite M
Chevkinite M
Pyrochlore M M M M M R R
Cerianite M M M
Columbite M Tr

1. Amba Dongar and Siriwasan. 2. Newania. 3. Sevathur. 4. Samalpatti . 5. Pakkanadu. 9. Kunavaram. 10. Mer-Mundwara. 11. Sarnu-Dandali-Kamthai. 12. Sung Valley. 13. Munnar
14. Khambamettu. 15. Swangre. 16. Kollegal. 18. Samchampi-Samteran. 19. Beldih-Kutni. 20. Udaiyapatti-Chhinnagoundan Palayam. Samalpatti has in addition vesuvianite, wollostonite,
quartz and ort - orthoclase. Newania has tremolite and graphite. Samchampi has calzirtite, jirkelite and baddeleyite in minor to trace amounts (Viladkar et al., 2009). E - Essential, M -
Minor, A - Accessory, R - Rare and Tr - Traces

JOUR.GEOL.SOC.INDIA, VOL.94, AUGUST 2019 123

 
Fig.3. Classification of Indian carbonatites in the CaO-MgO- FeO + Fe2O3 + MnO plots. Fields after IUGS, Woolley and Kempe (1989).

Fenites and Fenitisation features of fenitisation that can guide exploration for rare earths and
The term fenite was first introduced by Brögger (1921) to Nb, akin to those found as wall-rock alterations around deposits of
describe the leucocratic syenitic rocks of metasomatic origin Cu, Pb, Zn and others.
comprising 70-90% alkali feldspar, 15-25% aegirine and calcite, A striking feature that has been brought out by Elliot et al. (2018),
with accessory sphene and apatite, found around the Fen carbonatite is the extensive zone of fenitization (1-2 km wide) in meltiegite-
alkalic complex (Anderson, 1989). The term also includes, the ijolite-carbonatite complexes (e.g. Fen, Sokoli, and others)
metasomatism, on the older members of the carbonatite-alkaline compared to the narrow and thin (c. 100 m) zones in the
complex themselves (internal fenites) by the younger members of agpaitic, peralkaline, syenite and nepheline syenite complexes (e.g.
the complex that may include the different types of carbonatites. as Khibiny and Lovozero, Kola Peninsula, and Ilímaussaq, Greenland).
Mobilised (rheomorphic) and transported hybrid rocks were excluded Thus the dimensions of the fenitised or metasomatised zones, in
from this definition by Heinrich (1985) who provided a review on the alkaline rock complexes, in the absence of an exposed carbonatite
extremely diverse fenite types and metasomatism around alkline body, may indicate their genetic link to possible carbonatite-
complexes including carbonatites. Major reviews on fenites include related complexes compared to those agpaitic, syentic complexes that
those of Le Bas (2008) and the most recent one being by Elliot et al., lack carbonatites. Different types of fenites that have been studied
(2018; and references therein) wherein an attempt has been made to from carbonatite-alkaline rock complexes of India are given in
evaluate the nature of fenites and their genesis, so as identify specific Table 3.

B - Beldhi; SD - Saranu Dandali


Fig.4. Sr vs. Ba variations in some of the major carbonatite bodies of India (see Table 1 for sources of data for the different complexes).

124 JOUR.GEOL.SOC.INDIA, VOL.94, AUGUST 2019

 Table 3. Some examples of fenites from the different carbonatite complexes of India

Complex Country Rocks External fenites and fenites Internal fenites and types References

Amba Dongar Sandstones Sandstones to: Nephelinites (xenoliths in Dean et al. (1972); Sukheswala and
Basalts i. Microperthite+aegirine- augite (high temp. sovites) subjected to Viladkar (1981); Udas, 1970;
Dolerites deeper levels; sodic and sodic potassic types ). phlogopitisation Viladkar (1986); Viladkar (2015);
ii. Orthoclase(Or>90+ aegirine); low temp., Palmer and Jones, 1996;
shallow levels; potassic
iii. Mild nephelinisation of xenoliths of
diverse rocks.
Dolerites to:
i. basanitoids
Siriwasan-Nakal Sandstone Sandstone to albite and aegirine-bearing types; Sukheswala and Borges (1975)
Dominantly sodic Sethna and Borges (1981)
Sevathur Granite gneiss and i. Granitic gneiss to syenitic fenite (both sodic i. Pyroxenite to: Borodin et al. (1971)
charnockite and potassic types). a. pyroxene-biotite rock Krishnamurthy (1977)
with or without amphibole.
ii. Charnockite Group to: b. pyroxene-phlogopite- Sugavanam et al. (1976)
epidotised hornblende gneiss with riebeckite apatite-magnetite rock;
and arfvedsonite (epidote-amphibolite facies); ii.Development of vermiculite
sodic in pyroxenite
Samalpatti Hornblende gneiss Albitite and riebeckite veins; sodic types; i. Pyroxenites to: Subramanian et al. (1978)
may be reomorphic; aegirine-augite bearing types Viladkar and Subramanian (1995)
ii. Syenites albitised
Pakkanadu Migmatites i. Pyroxenites to aegirine- Rao et al. (1978)
augite bearing types;
Hogenakal Charnockitic gneiss Not noticed Pyroxenites to: Srinivasan (1977)
and granitoids i. pyroxene-biotite rock
ii. Pyroxene-phlogopite-
magnetite rock;
In carbonatites:
i. diopside and augite to
alkali ambhibole.
ii. Aegirine rim around biotite
Newania Granite gneiss Granite gneiss to: Viladkar (1981a)
i. repeated syenitic fenite with arfvedsonite?
(sodic and potassic)

Sung valley Quartzite Quartzites to: Pyroxenite to: Chattopadhyay and Hashmi (1984)
i. granitic and syenetic types i. aegirine-augite and potash Krishnamurthy (1985)
(sodic potassic and potassic) feldspar bearing types
ii. Pure potash feldspar veins with or ii. Extensive phlogopitisation
without aegirine
iii. Wollostonite-rich rocks with aegirine
augite and andradite

Samchampi Granite gneiss Granitic gneiss to: Pyroxenites to: Dhirendra Kumar et al. (1989);
i. syenitic types i. ijolitic types Hoda (2002)

GEOCHEMISTRY Chondrite Normalised –REE Patterns

Representative analyses of carbonatites from different complexes Carbonatites as a group show maximum enrichment in REE among
of India are given in Table 4. The range and averages for the three igneous rocks and become ore-grade in many complexes. The REE-
different carbonatites types, compiled by Woolley and Kempe (1989) chondrite plot from different complexes India illustrates this feature
are also included in the Table 4. It can be seen that, geochemically, (see Figure 5). At Amba Dongar, REE, abundances in ferrocarbonatites
carbonatites represent, a group that are very heterogeneous and reach 10,000 x times the chondrite and become ore grade. REE
elemental abundances vary considerably. The representative nature abundances are at maximum in the Kamthai samples indicating its
of such averages, however, has been debated (Woolley and Kempe, mineralised character.
1989) since the carbonatite magma loses its original Na and K as it
evolves (causing the fenitisation) and also some other elements STABLE AND RADIOGENIC ISOTOPES
that are geochemically coherent like Ba, Rb, F, Cl and others. An
Carbon and Oxygen Isotopes
example of such a variation is given by the Sr vs. Ba abundance plot
(Figure 4). Stable isotope studies of Indian carbonatites have been pioneered
Wide variations in the abundance levels of Ba and Sr have been by PRL in India since the late 1980s and had continued since then by
observed from the carbonatite complexes of India. These occur both a number of workers (see Table 5 and Figure 6). Ray and Ramesh,
within a single complex (e.g. Newania) and between complexes as 2006) and Viladkar and Ramesh (2014 and references therein) provide
well, clearly portraying the modal variations of minerals that carry reviews on these isotopes from carbonatite complexes of India. The
these elements such as strontianite, calcite and apatite (Sr), phlogopite/ data when considered in tandem with Figure 6, lead us to the following
biotite (Ba) besides minerals such as barite, benstonite and celsian inferences.
that are present in some of the carbonatites in varying proportions 1. Primary mantle fields (PMFs) of δ18O (6 – 10 ‰) and δ13C (– 4
(see Table 2). to – 8) are indicated for most of the complexes, especially those

JOUR.GEOL.SOC.INDIA, VOL.94, AUGUST 2019 125

126

Table 4. Representative analyses of carbonatites from different complexes of India (See Table 1 for location and references)

ADC-3 ADF-9 Siri.-2 Siri.-8 Sev-2 Sev-4 Sev-174 ICOFS1 Joggi191 H-46 Pak-204 KMB-2 KC-30 SD-1 M-18 Newa.2 Newa.4 Kamthai C/254 Mund.-9 SV Bheldi-5 LV30 TH-2

SiO2 7.82 9.14 7.32 5.07 1.49 3.66 0.01 5.13 0.07 0.2 8.03 8.27 0.57 0.18 9.99 1 0.2 1.47 3 1.5 0.46 2.14 4 10.3
TiO2 0.09 0.1 0.07 0.53 0.01 0.06 0.11 0.03 0.22 0.08 0.01 0.22 0.11 0.08 0 0.04 0.15 n.d 0.13 0.14 0.2 0.1
Al2O3 0.24 0.31 0.55 0.16 1.45 0.75 0.03 2.03 0.02 0.35 3.01 3.2 0.09 2.18 2.55 1.2 0 0.45 0.72 n.d 0.19 0.07 0.9 0.8
Fe2O3 2.92 8.04 3.56 11 1.8 12.79 0.99 0.18 5.66 Tr 2.62 5.84 1.77 13.78 0.08 3.3 12.3* 3.22 6.71 0.74 2.22 1.95 6.4 6.6
MnO 0.37 1.64 1.66 0.59 0.2 1.12 0.37 0.02 0.72 Tr 0.18 0.14 0.19 0.18 0.03 1.2 1.8 2.41 0.72 0.42 0.18 0.29 0.3 0.4
MgO 0.34 12.6 1.81 4.32 2.94 12.9 4.03 3.03 14.55 1.2 0.94 6.88 4.48 0.72 0.8 16.5 12.3 0.26 0.81 1.2 2.64 1.13 3.6 13.2
CaO 50.81 28.2 45.78 43.66 50.23 28.04 49.34 50.02 36.37 54.28 43.69 38.07 52.22 42.28 49.28 30.33 31 26.37 46.03 53.8 50.85 49.1 47.1 36.2
Na2O bd bd 0.05 0.24 0.3 1.31 0.06 0.22 0.13 0.14 0.68 0.02 0.08 0.02 0.5 0.09 0 0.18 0.84 0.2 0.04 0.21 0.3 0.3
K2O bd bd 0.02 0.07 0.21 0.19 0.39 0.01 0.11 1 1.32 0.01 0.02 0.58 0 0 0.17 0.8 0.2 0.12 0.01 0.1 0.2
P2O5 1.53 0.11 2.15 2.55 2.65 1.09 0.22 0.04 9.51 0.11 1.16 5.28 2.18 0.04 0.09 3.7 2.5 0.4 0.6 0.04 2.15 2.96 1.8 6.2
CO2 36.25 36.66 42.95 36.67 34.91 42.57 32.48 29.6 38.6 39.5 35.5 39.84
LOI 33.71 39.1 35.78 31.9 27.87 39.63 41.28 34.2 24.7
H2O+/- 0.32 0.56 0.5 0.04
Total 100 100.4 98.75 100.09 97.85 98.57 97.99 99 101.9 99.79 94.01 99.5 61.6 59.62 90.71 96.00 99.60 34.61 98.52 101.08 97.91 99.28 99 99

Rb 0.3 0.58 2 2 0.09 19 0.11 13.49 27.95 1.61 11 14 4 2.67 2.22 41 47

Sr 2419 2468 3523 3000 8750 9375 8110 339 8840 12253 15910 6328 24974 0.16% 553 990 6050 24000 0.85% 997 198 8807 4058 3187
Ba 17200 7791 393 360 1590 2210 1900 268 1560 517 5300 15029 570 1.49% 78 410 15 88000 2.19% 684 4374 1489 60 485
Nb 900 210 60 30 10 80 1.6 40 3.44 23 35 0.99 610 290 473 70 114 44 347 66
Zr 61 3.3 180 955 375 470 16 20 367 16.06 72 68 4.12 37 60 20 10 29 252 870
Hf 1 0.5 0.52 0.83 0.92 1.47 0.13 0.33
V 81 499 173 430 10 <2 8 42.79 36 5 4.08 53 14 257 44
Cr 30 4 32 19.22 27 21.57 83 14 10 10
Ni 3 3.7 17 6.3 35.88 33 20 33.5 27 5
Co 0.85 <2 8 5.85 8.7 12.59 23 18 18 10
Zn 84 2192 14 40 43.23 30 54.9 26 1755
Ta 0.2 0.2 0.03 0.21 7.5 0.21 1.24 0.22 7.5 <50
Pb 20 606 10 5.1 2.88 51 95.89 62 6
Th 115 128 160 160 2.46 1.4 7 42.44 17.3 5 1.01 78 5 0 5 343 5.51
U 1.2 44 1.39 0.63 17.1 2.08 9.2 5 0.13 4.4 20 40 3 0.6 11.66 397 134
La 1500 3001 2200 346 631 140 430 6.5 506 1871 870 1045 598.7 395 87 545 153 131800 > 5000 163 161 461 679 383
Ce 2850 4424 6150 878 720 675 790 14 1115 33.75 1320 2027 1249 512 149 2680 182 155500 > 5000 74 351 833
Pr 329 375 1.6 1.58 45 44 322 180
JOUR.GEOL.SOC.INDIA, VOL.94, AUGUST 2019

Nd 1110 1065 224 6.2 587 1802 390 592 57 455 21800 172 374 54 10
Sm 150 123 89 22.4 45.7 1.3 95.8 290 43.1 120 105 13 8.5 52.3 8.7 29 48
Eu 39 28 23 5.2 14.2 0.28 23.8 60.42 10.2 2.78 26 4.3 28.4 4.2 9 15 13
Gd 102 105 1.2 188.3 66 3085 22 34 32 20
Tb 14 8.8 10.6 2.3 5 0.17 7.1 16.97 2.2 9.2 7 1.2 1.1 5.7 0.7 3 4.5
Dy 67 34 0.87 72.27 30 2.2 13 19 13 2
Ho 12 5.5 0.2 8.24 5 2.1 3.81
Er 29 17 0.52 34.14 9 5.17 7.87
Tm 4 1.7 0.07 1.68 0.9 0.52 0.93
Yb 19 10 13.1 5 6.6 0.49 3.39 9 1.94 6.2 4.6 0.5 1.5 2.6 0.64 3.37 5.39 3 2
Lu 2.3 1.3 1.2 0.5 0.84 0.08 0.43 1.25 0.25 0.9 0.57 0.5 0.6 0.44 0.11 0.41 0.68
ΣREE 6227 9199 33.2 2475 2694 1030 815.6 1742 1573 744
Y 453 160 125 150 <5 25 96 5.5 97 202.3 32 119 17 10 10 105 50 53 54 88 58 34
Sc 13 15 11 23.5 1.8 9 11.71 0.53 11.7 16 1.79
JOUR.GEOL.SOC.INDIA, VOL.94, AUGUST 2019 Table 4. Contd...
Khader.538 MPC-42 Katarkh. Av Calcio-Carb. Av. Magnesio. Carb. Av. Ferro.-carb. Av. Samailov
Wt.%
SiO2 7.23 16.1 8.03 0—8.93 (116) 2.72 0.6—9.40 (50) 3.63 0.36—9 (57) 4.7
TiO2 0.03 0.38 0.22 0—1.09 (115) 0.15 0—1.98 (49) 0.33 0—2.3 (57) 0.42
Al2O3 0.36 2.1 1.12 0—6.89 (116) 1.06 0—4.41 (53) 0.99 0.01—5.6 (53) 1.46
Fe2O3 < 0.20 4.6 2.64 0—9.28 (97)** 2.25** 0—9.57 (48) 2.41** 0.46—17.84 (50) 7.44**
MnO 0.17 0.21 0.24 0—2.57 (119) 0.52 0.02—5.47 (54) 0.96 0.23—5.53 (57) 1.65
MgO 0.11 3.2 2.81 0—8.11 (122) 1.8 9.25—24.82 (54) 15.06 0.10—14.50 (58) 6.05
CaO 49.9 50.6 42.98 39.24—55.40 (118) 49.12 20.8—47 (53) 30.12 9.20—46.43 (58) 32.77
Na2O < 0.01 3.2 2.81 0—1.73 (102) 0.29 0—2.23 (44) 0.29 0.0—1.52 (46) 0.39
K2O 0.01 0.04 0.07 0—1.47 (105) 0.26 0—1.89 (44) 0.28 0.0—2.80 (51) 0.39
P2O5 1.15 0.05 4.48 0—10.41 (119) 2.1 0—11.3 (51) 1.9 0.0—11.56 (54) 1.97
CO2 37.4 21.58 35.24 11.02—47.83 (104) 36.64 16.93—47.88 (49) 36.81 20.56—41.81 (53) 30.74
LOI 38.1
H2O+/- 0—4.49 (78) 0.76 0.08—9.61 (36) 1.2 0.04—4.52 (35) 1.25
Total 97.02 99.25 100.64
ppm
Rb 0.64 4—35 (6) 14 2—80 (4) 31 Not given
Sr 873 69 94 0—5 (74)* 0.86% 0.06—1.50 (29) 0.69% 0.1—5.95 (34) 0.88% > 700
Ba 0.55% 78 0—3.29 (66) 0.34% 0.01—4.3 (32) 0.64% 0.02—20.6 (38) 3.25% > 250
Nb 66.5 < 20 < 20 1—15000 (43) 1204 10—3000 (18) 5691 10—5033 (17) 1292
Zr 20 179 61 4—2320 (33) 189 0—550 (14) 165 0—900 (13) 127
Hf 0.2
V 68 61 1548 0—300 (31) 80 7—280 (9) 89 56—340 (16) 191 > 20
Cr 20 84 51 2—479 (10) 13 2—175 (9) 55 15—135 (8) 62
Ni 20 72 20 5—30 (11) 18 21—60 (5) 35 10—63 (7) 26
Co 1 31 29 2—26 (12) 11 4—39 (9) 17 11—54 (7) 26
Zn 6 89 188 15—851 (10) 251 35—1800 (9) 606
Ta 0.3 0—0 (1) 5 4—34 (6) 21 1 0.09
Pb 163 121 < 10 30—108 (6) 56 30—244 (7) 89 46—400 (4) 217
Th 75 5—168 (13) 52 4—315 (11) 93 100—723 (13) 276
U 32.6 0.3—29 (10) 8.7 1—42 (13) 13 1—20 (16) 7.2
La 1350 29 < 100 90—1600 (31) 608 95—3655 (19) 764 95—16583 (15) 2666
Ce 2060 670 37 74—4152 (18) 1687 147—8905 (14) 2183 1091—19457 (8) 5125
Pr 168 50—389 (2) 219 1 560 141—1324 (4) 550
Nd 490 190—1550 (8) 883 222—1755 (6) 634 437—3430 (4) 1618
Sm 49.4 95—164 (2) 130 33—75 (6) 45 30—233 (4) 128
Eu 10.8 29—48 (2) 39 3—20 (6) 12 11—78 (4) 34
Gd 26.8 91—119 (2) 105 31—226 (4) 130
Tb 2.48 9—10 (2) 9 0.9—8 (6) 4.5 4—36 (4) 16
Dy 10.2 22—46 (2) 34 11—105 (4) 52
Ho 1.54 3—9 (2) 6 1—9 (4) 6
Er 2.4 1 4 3—35 (4) 17
Tm 2.65 1 1 1—52 (10) 0.03—3 (4) 1.8
Yb 1.5—12 (10) 5 1 9.5 1—16 (4) 15.5
Lu 0.38 1 0.7 0.08
REE 4473.53 > 500
Y 43.5 < 20 10 25—346 (16) 119 5—120 (13) 61 28—535 (9) 204
Sc 2 0.6—18 (7) 7 10—17 (3) 14 9—14 (2) 10

Note: Sr and Ba values in % denotes oxides; ** Values of FeO not given here. Index to analyses: Amba Dongar: ADC-3 & ADF-9, Chandra et al. (2017), Table 1; Siriwasan: Siri-2 & 8, Viladkar and Gittins (2016), Table 1;
Sevathur: Sev-2 & Sev-4: Krishnamurthy (1977), Table 1; Sev-174, Schleicher et al. (1998) Table 1; Samalpatti: ICOSF 1, Ackermann et al. 2(017), Table 1; Joggipatti: Jogi-191, Schleicher et al. (1998), Table 1; Hogenakal:
H-46, Pandit et al. (2002); Table 1b; Pakkanadu: Pak-204, Schleicher et al. (1998), Table 1; Khambamettu: KMB-2, Burtseva et al. (2013), Table 1; KC - 30, Renjith et al. (2016), Table 1; Udaiyapatti: SD - 1, Senthilkumar
et al. (2000), Table 6; Munnar: M-18, Santosh et al. (1987), Table 1; Newania: Newa - 2 & -4; Viladkar (1998), Table 6; Kamthai: No. 5, alvikite dyke, Viladkar (1998), Table 6; C/254, alvikite, Chandrasekaran and
Srivastava, (1992), Table 1; Mundwara: Mund-9, Subramaiam and Rao, 1977; Sung Valley: SV, average of 7, Srivastava et al. (2005), Table 3; Beldih: 5, Chakraborty and Sen (2010), Table 2; Samchampi: LV-30 & TH-2,
Hoda and Krishnamurthy (2017), Table 2; Khaderpet: 538, Smith et al. (2013), Table 1; MPC-42, carbonatite?, Hari et al. (1998), Table 1; Katarkh. Av. Khandelwal et al. (1997), Table 3. Range and Average of Calcio-,
127

Magnesio- and Ferro-carbonatites from Woolley and Kempe, 1989, Table 1.1 and 1.2. Typical values of Sr, Ba, V and REE from Samailov (1991, p.252).
 


Fig,5. REE variations in some of the major carbonatites of India. (see Table 1 for sources). ADCC = Amba Dongar calico-carbonatite and ADFC
= Ferro-carbonatite. Others, as indicated in the diagram.

of plutonic types (see Table 5). mantle regions brought up by plumes.

2. The Amba Dongar calcitic carbonatites show clear evidence of 6. Recent publications on combined calcium (δ44/40Ca and δ44/42
primary fractional crystallization with fields up to higher δ18O Ca) and radiogenic isotopes of Sr-Nd at Amba Dongar (Banerji
(15) and heavier δ13C (– 2) abundances. Secondary, altered and Chakrabarti, 2019), and boron isotope (δ11 B) from a number
carbonatites (e.g. mainly Amba Dongar and others) show wide of carbonatite complexes of the world, including Amba Dongar
variations in δ18 O values ( > 15 ‰) and δ13C (– 4‰ to –2‰) and Barmer (Sarnu-Dandali), Hulett et al. (2016) have indicated
that apparently results from low temperature alteration by the role of recycling of subducted crustal components in the
either meteoric water or CO2-bearing aqueous fluids. mantle source regions (especially in asthenosphere-sourced
3. C and O isotopes of calc-silicate rocks and marbles that are found Reunion plume), corroborating the inferences based on O-C
in the Samalpatti and others areas (e.g., Borra; Le Bas et al., isotopic studies by Ray and Ramesh (2006) mentioned above.
2002) clearly show their non-carbonatitic origin.
4. Ray and Ramesh (2006) further demonstrated that 90% of Sr, Nd and Pb Isotopes
the data lie in the range of δ13C (–6 to –2 ‰) compared to those Radiogenic isotopic studies in understanding the genesis of
from outside India (Deines, 1989). carbonatites have been briefly reviewed by Bell (1998). Studies on
5. Based on more enriched values of δ13C ( –3.1‰) in the complexes the Sr-Nd-Pb systematics on Indian carbonatites began in the early
such as Sung, Samchampi, Swangkre and at Amba Dongar 1990s, largely through collaborative studies and also developing in-
(δ13C = – 5.4 – 2.1‰; Viladkar and Schidlowski, 2000) (see house capabilities in several institutes in India such as NGRI, AMD
Figure 6 ), Ray and Ramesh (2006) postulate that the enrichment and PRL. Data on Sr, Nd and Pb-isotopes on Indian carbonatites are
in the mantle source regions of these complexes, apparently summarised in Table 6 and the εNd vs. εSr isotopes are plotted in
occurred as a sequel to metasomatism by fluids derived from Figure 7.
recycled oceanic crust through subduction around 2.8 Ga, that Various mantle reservoirs, such as HIMU (a mantle source
carried enriched crustal carbon into the lithospheric or deep enriched in U and Th believed to be due to recycling of ancient altered

128 JOUR.GEOL.SOC.INDIA, VOL.94, AUGUST 2019

 Table 5. Stable isotopes of carbonatites of India systematics of the carbonatites of India, summarised in Table 6,
Complex δ13C δ18O Remarks clearly indicate two significant features.
Subvolcanic-Effusive 1. The Cretaceous complexes, such as Amba Dongar, Sung Valley
and Samchampi indicate an EM2 and ‘plume type’ Reunion
1. Amba Dongar1 –2.68 to –8.62 (21) 7.67 - 26.82 PMF and altered
2. Amba Dongar2 –2.1 to –7.5% (28) 7.7 -15.3 PMF (Deccan) and Kerguelen (Sylhet) sources akin to depleted
3. Amba Dongar3 –4.12 to –3.58 (4) 8.8 – 10.02 PMF MORB-type and kimberlite Gr.I (Figure 7; also Simmonetti et
(calcio) al., 1998; Simmonetti et al., 1995).
4. Amba Dongar3 –1.62 to – 4.29 13.73 – 24.67 PMF and altered
2. The Paleoproterozoic, Hogenakal and other Neoproterozoic
(ferro)
5. Siriwasan5 –5.5±0.2 7.9±0.8 PMF carbonatite complexes and associated pyroxenites (Pakkanadu,
Samalpatti and Sevathur), on the other hand, clearly show the
Plutonic
involvement of more EMI type source (akin also to some of the
6. Sevathur1 –4.99 to –5.09 (3) 7.86 – 7.94 PMF
ultrapotassic rocks of Leucite Hills, Vollmer et al., 1984) besides
7. Sevathur4 –4.8 to –6.2 6.7 – 7.6 PMF
8. Sevathur8 –4.76 to –5.95 2.62 – 10.50 PMF some depleted HIMU and Kimberlite Group II type sources as
9. Hogenakal4 –6.0 to –6.3 7.0 – 8.1 PMF indicated in plots (Figure 7).
10. Khambamettu6 –6.4 7.8 PMF
11. Samalpatti1 0.56 to –2.75 (7) 11.73 – 17.61
PETROGENESIS AND DISCUSSIONS
12. Samalpatti 8 –1.81 to –4.0(4) 21.7 – 23.2 Modified/Altered
(carb) Petrogenetic considerations of the carbonatite complexes of the
13. Silico-carb. –3.14 to –3.91(8) 10.1 – 25.5 Modified/Altered world over, coupled with studies in experimental petrology including
14. Samalpatti10 –0.56 to –2.75 (7) 11.73 – 17.61 Altered samples from Oldoinyo Lengai (Potter etal., 2017; Weidendorfer et
15. Mundwara1 –6.15 to –6.55 6.36 - 9.40 PMF
al., 2017 and references therein) have provided wealth of data towards
16. Sung valley5 –3.1±0.1 6.3±0.2 PMF
17. Sung Valley 11 –3.12 to –3.29 7.35 – 7.93 PMF their origin and genesis from upper mantle depths. Fluid and melt
18. Samchampi5 –3.1±0.2 7.3±0.7 PMF inclusion studies on minerals such as magnetite, perovskite and apatite
19. Newania (DC)7 –3.6 to –4.9 (7) 7.1 – 13.6 DC - PMF that crystallize very early from the carbonatite melts (Guzmics et al.,
20. Newania (Fc) –0.5 to –2.2 (3) 26.8 – 33.1 2012; Schleicher, 2019) have also enabled a better understanding of
21. Udayapatti9 –4.9 to –5.0 9 -9.2 PMF
the carbonatite magma or melt compositions and their petrological
1. Srivastava and Taylor (1996) includes samples of Viladkar and Subramaniam (1995); evolution. All these data have led to the recognition of the following
2. Viladkar and Schidlowski (2000); 3. Simmonetti et al., (1995); 4. Anilkumar et al. (1998);
three genetic schemes (Mitchell, 2005; Woolley, 2013; Jones et al.,
5. Veena Krishna (2000); 6. Burtseva et al. (2013); 7. Ray et al. (2013); 8. Akerman et al.,
(2016); 9. Senthil Kumar et al. (2001); 10. Ray and Ramesh (2006); 11 - Srivastava et al., 2013 and references therein) for carbonatites.
(2005); DC- Dolomitic carbonatites and Fc – Ferro carbonatites. PMF - Primary mantle
filed. 1. Primary mantle melts from metasomatised, CO2-bearing mantle
peridotites (Wallace and Green, 1988; Dalton and Presnall, 1998;
oceanic crust into the mantle), DMM (Depleted MORB mantle), EM1 Harmer, 1999).
(Enriched Mantle 1, generated either by recycling of lower crustal 2. Residual liquids through fractionation of primary, ultra-alkali
material or enrichment by mantle metasomatism) and EM2 ( Enriched melts (e.g., nephelinite-phonolite and other suites (Gittins and
Mantle 2, possibly formed by recycling of continentally derived Jago, 1998; Mitchell, 2005; Woolley, 2013).
sediment, or ocean island crust into the mantle by subduction processes) 3. Liquid immiscibility from CO2 - saturated primary silicate melts
have all been recognized from different carbonatites of the world (Brooker and Kjarsgaard, 2011 and references therein;
(Zindler and Hart, 1986; Rukhlov et al., 2015) including India (see Weidendorfer et al., 2017).
references in Table 6 and Figure 7). Available data on the Sr-Nd-Pb
The genetic models that have been proposed for the different
carbonatite complexes of India in the light of the above three categories
are briefly dealt with in the following section.

Partial Melting of Metasomatised Mantle: Carbonatites as

Primary Melts (e.g. Newania, Udaiapatti, Jokipatti,
Beldih, and Khambamettu)
Presence of magnesite, graphite and Cr-rich magnetite in the
dolomitic carbonatites of Newania, led Doroshkewich et al., (2010)
to postulate a primary beforsitic magma at Newania. Application
of a multicomponent Rayleigh isotopic fractionation model to the
correlated δ13C versus δ18O variations in the unaltered carbonatites
led Ray et al., (2013) to suggest that the carbonatites have crystallized
from a CO2 + H2O fluid - rich magma that had a mantle-source
isotopic composition (see Table 5). Trace element modelling coupled
with Sr-Nd isotopic data led Ray et al. (2013), further to infer that the
carbonatites conform to the incipient melts from a carbonated,
phlogopite bearing-peridotitic source as inferred from experimental
 petrology by Yaxley and Green (1996) and Wyllie and Lee (1998).
Presence of benstonite at both Udaiyapatti and Jokkipatti which
Fig. 6. δ13 C vs. δ18 O isotope plot for the carbonatites of India ( modified can form only at a pressure of 1.5 GPa at 840º – 650º C, clearly indicate
after Schleicher et al., 1998, Fig. 7; see Table 5 for sources of data mantle–depths for their origin (Vladykin et al., 2008).
used). The field of primary igneous carbonatites box and Ocean Island The primary status of the carbonatite at Beldih has been inferred
Basalts (OIB) indicated are after Keller and Hoefs (1995) and Deines by Chakrobarty and Sen (2010) based on the presence of Type B
(1989) respectively. apatite in the carbonatites (O’Reilly and Griffin, 2000) and also

JOUR.GEOL.SOC.INDIA, VOL.94, AUGUST 2019 129

 
Fig .7. εNd vs εSr plot for the carbonatites of India (modified after Schleicher et al., 1998, Fig.11; the pyroxenite field represents samples from
Samalpatti and Pakkanadu carbonatite complexes). See Table 6 for isotopic data and sources. SV - Sung Valley. Others indicated are dealt with
in the text.

from the lower Ba/La and Nb/Th ratios found in the carbonatites suites, namely the carbonatite (sovite-ferro-carbonatite) and the
(Chakmouradian et al., 2008). nephelinite – phonolite. Based on high LREE/HREE fractionation
Burtseva et al., (2013) based on mineral thermometer of dolomite, (average (La/Yb)N = 175 in carbonatites and 50 in nephelinites), a
olivine, spinel, phlogopite and Mg-rich ilmenite (790°-980°C), inferred very low degree of melting (<1%) has been envisaged. In a recent
a primary status for the Khambamettu carbonatite. study of noble gases from Amba Dongar pyroxene and calcite
separates, Hopp and Viladkar (2018) had shown plume-neon
Fractionation of Alkali Carbonate Magma and Liquid contributions ranging up to the Réunion hotspot reference line. A
Immiscibility of Mantle Melts pyroxene separate from the Siriwasan carbonatite even showed a
‘Loihi-type’ neon composition. Thus, they conclude that both upper
Amba Dongar and Siriwasan
mantle and mantle plume sources apparently contributed in different
Trace element modelling by Chandra et al., (2017) led to postulate ways to the formation of these two carbonatite complexes.
that the primary carbonatite melt was generated from a subcontinental
lithospheric mantle (SCLM) that was metasomatised by the CO2-rich Sarnu-Dandali-Kamthai carbonatites
fluids and provided thermal energy from the Deccan plume (Reunion). The Sarnu-Dandali-Kamthai carbonatite complex exhibits a
Melting of this SCLM generated a ‘carbonated silicate magma’ continuous gradation from alkali pyroxenite to feldspathic ijolite
that underwent liquid immiscibility at crustal depths, forming the two through micro-melteigite and ijolite with foidal syenite and phonolite

Table 6. Radiogenic isotopes of Indian carbonatites

87 86 143
Complex Sr/ Sr εSr Nd/144 Nd εNd 206
Pb/204 Pb 207
Pb /204 Pb 208
Pb / 204 Pb

1. Amba Dongar 1
Calcio – carbonatites 0.70549 -70579 (4) +15.1 to +19.0 0.51248 -0.51252 –0.8 to –1.6 19.05 – 19.09 15.72 – 15.74 39.72 – 40.16
Ferro – Carbonatite 0.70566 – 70581 (5) +17.5 to +26.0 0.51248 – 0.51253 –0.6 to –1.6 18.94 – 19.28 15.66 – 15.81 39.55 – 40.05
2. Amba Dongar 7 0.70545 – 0.70565 (2) +14.6 to +17.6 0.512503 – 0.512526 –1.55 19.02 – 19.26 15.61 – 15.64 39.51 – 42.80
3. Sirivasan7 0.70580 – 0.70595 +19.6 to +21.8 0.512490 – 0.512491 –1.82 19.02 – 19.26 15.60 – 16.19 39.38 – 42.80
4. Sevathur2 0.70500 – 0.70529 (5) 0.51179 – 0.511327 –5.4 to –8.3 17.20 – 68.0 (8) 15.55 – 32.11 (8) 37.39 – 38.53
5. Sevathur3 0.70508 – 0.70523 (5) +21.2 to +23.0 0.511815 – 0.511871 –5.1 to –5.9
6. Sevathur3a 0.704887 – 0.705504 (6) 0.511125 – 0.511141 –3.9 to –7.0 16.57 – 16.97 15.51 – 15.64 36.97 – 37.88
7. Joggipatti2 0.70513 – 0.70514 (3) 0.51121 – 0.511345 –5.1 to 7.76 37.55 – 37.94 15.36 – 15.53 16.63 – 16.84
8. Samalpatti2 0.70537 – 0.70554 (2) 0.511394 (1) –4.15 36.67 – 37.75 15.39 – 15.66 17.20 – 21,26
9. Samalpatti3 0.705294 -0.712914 (6) 0.511506 – 512174 –5.3 to –14.4 16.50 – 17.57 15.37 – 15.68 36.81 – 38.38
10. Pakkanadu2 0.70503 (1) 0.511257 –6.83 37.96 – 92.73 15.52 – 16.30 17.45 – 24.80
11. Hogenakal3 0.70169 – 0.70236 (4) 0.511239 – 0.511317 –1.1 to –1.3
12. Hogenakal8 0.70161 -0.70174 (2) 0.511136 – 0.511238
13. Newania4 0.702117 – 0.702052 (2) 0.511533 –5.3
14. Sung valley5 0.70442 – 0.70456 (4) 0.511254 – 0. 511256 +0.7 to +1.5 39.14 – 39.682 15.06 – 15.713 19.451 – 19.540
15. Sung Valley6 0.70471 – 0.70489 (8) + 5.3 to +6.9 0.51264 – 0. 51266 +1.7 to +2.3 19.40 – 93.19 15.68 – 19.24 40.43 – 88.29
16. Sung Valley9 0.704710 – 0.704830 (7) + 4.68 to +6.98 0.512538 – 0.512594 +0.68 to +1.78
17. Samchampi 5 0.70471 – 0.70471 (3) 0.511252 – 0.511256 +0.3 to +1.2 19.450 – 19.462 15.648 – 15.726 19.793 – 41.254
Index to sources as indicated by numbers in superscript after the name of the complex: 1. Simmonetti et al., 1995; 2. Schleicher et al., 1998; 3. Anil Kumar et al., 1998; 3a. Akerman et al.,
2016; 4. Ray et al., 2013; 5. Arundhuti and Basu, 2013; 6. Veena Krishna et al., 1998; 7. Veena Krishna (2000); Saha et al., 2017, 8. Pandit et al., 2002; 9. Srivastava et al., 2005; Number
of samples given in parentheses in the 87Sr/86 Sr column. Isotopic data is age corrected/initial values as given by the authors.

130 JOUR.GEOL.SOC.INDIA, VOL.94, AUGUST 2019

in the end phase (Bhushan, and Chandrasekaran, 2002). Carbonatites carbonatites and the perovskite from a dunite, and the bulk-rock
include sovitic, alvikite and ferro-carbonatite varieties. Progressive carbonatites of Sung Valley have the lowest initial 87Sr/86Sr and εNd
increase in Al2O3, Na2O and K2O and decrease in MgO, CaO, total values, apparently the best proxies of the lithospheric mantle source
iron, MnO and TiO2 with increasing SiO2 indicates the role of fractional compositions. Based on combined Nd–Sr–Pb-isotopic data and trace
crystallisation in the evolution of the suite, the major fractionating element geochemistry of the SVCC (Veena et al., 1998) and Ghatak
phases being pyroxene and magnetite (Chandrasekar and Srivastava, and Basu (2013) propose a genetic model in which the carbonatite is
1992). derived from a relatively primitive carbonated garnet peridotite source
in the Kerguelen plume (KP) with a HIMU-EM 2 component that
Petrogenesis of Syenite Dominated Carbonatite Complexes of yields alkaline ultrabasic melts including carbonatites at greater
Northern Tamil Nadu (e.g., Sevathur, Samalpatti Pakkanadu depths with low-degree melting.
and Hogenakal) and Andhra Pradesh The Samchampi-Samteran carbonatite complex (Nag et al., 1999)
Recent work on melt inclusions of apatite and calcite from sovites appears to have evolved from primary, mantle derived melteigite-ijolite
at Sevathur by Schleicher (2019) has provided evidence for the suite with development of alkali pyroxenites, akin to jacuprangites,
existence of different pulses of carbonatite melt during crystallization from which carbonatites evolved through fractionation or liquid
and also on the fractionation process. For example, ‘mere apatite immiscibility. Recently, Saha et al., (2017) based on Sr and Nd
crystallization and fractionation does not lead to enriched REE isotopic data invoke a plume-derived OIB-type mantle with recycled
compositions during carbonatite evolution but lowers their subduction component (EM II) as a source for the complex akin to
concentrations in the residual melts’…..and ‘ if segregated apatite is those suggested by Veena et al. (1998) and Gatak and Basu (2013) for
collected and incorporated by a new melt batch, the overall REE of the Sung Valley carbonatites.
this melt will be increased’ (c.f. Schleicher et al., p.305). The At Mer-Mundwara, carbonatites formed from late carbonatitic
petrogenetic relations between the syenites and carbonatites of liquid left after the crystallisation of the silicates from the melteigite –
Sevathur, Samalpatti and the Yelagiri plutons have been elucidated by theralite parent magma (c.f. Chakraborty and Bose, 1978).
several studies (Miazaki et al. 2001; Mukhopadhyaya et al. 2011 and
references therein). Based on geochemical and isotopic characteristics, Minor Carbonatites from Alkaline Syenite or Granite Complexes
the syenites have been shown to be derived independently from (Kunavaram and Elchuru and Munnar)
isotopically different sources from those of carbonatites. A subduction- The occurrences of carbonatites are very minor at Kunavaram and
related tectonic regime has been inferred for the Elagiri syenites by Elchuru and occur as minor veins and clusters, in association with
Mukhopadhyay et al. (2011). shonkinite, malignite, melteigite and nepheline-syenite. The
Furthermore, there is also a distinct age difference between the carbonatites apparently formed by fractional crystallisation of CO2-
carbonatites of Hogenakal and others, both in age and mantle-source bearing silicate magmas as suggested by Ratnakar and Leelanandam
characters. Hogenakkal being, Paleoproterozoic, one of the oldest in (1989).
India (2.4 Ga; Pandit et al., 2016), with a depleted, OIB-like source The carbonatites of Munnar are very minor, and are considered to
with (εNd +0.54 and +1) and significantly lower initial 87Sr/86Sr ratios represent a ‘late immiscible fraction that separated from a polymerized
(0.70161 and 0.70174) (see Figure 7). alkali silicate melt’ as part of a Late Precambrian alkaline magmatic
The Samalpatti carbonatites have been shown to have a complex regime in this part of the Indian Shield (c.f. Santhos et al., 1987). This
petrological and geochemical history such as the pre-emplacement carbonatite, based on lower abundances of the typical carbonatite suite
interaction with a host of crustal materials such as gneisses, of elements (see Table 4 and Figure 4) could also in part be due to the
charnockites, calc-silicate rocks besides other rock types present in carbonatites being formed from carbothermal solutions of the alkaline
the area. The Samalpatti carbonatites contain samples with carbonatitic silicate melts.
affinities with much lower values of characteristic trace elements such
as P, Sr, Ba, Zr, Nb, Th, Y and REEs than the average concentrations Carbonatite – Kimberlite – Lamproite Association
for a magmatic carbonatite (see Table 4). Samalpatti area also (Wajrakarur, Khaderpet, A.P.)
contains calc-silicate rocks that show a wide range of C–O isotopic This association with the presence of diamond had been recognised
compositions (see Figure 6), values more akin to calc-silicate for the first time in the Proterozoic kimberlite fields of Andhra
rocks and marbles as at Borra, a locality earlier thought to be a Pradesh, India by Smith et al., (2013). The Khaderpet carbonatite
carbonatite (Le Bas et al., 2002). On the other hand, such heavy component shows extreme enrichment in REE approaching that of
isotopic signatures could be due to large scale hydrothermal interaction world-average carbonatite (see Table 4) along with the associated
with carbonated-fluids as suggested by Ackerman et al. (2017) and widespread aureole of metasomatism. The diamondiferous carbonatite
Srivastava (1998). is considered to be a late-stage fractionation product of the Khaderpet
diamond-bearing ultramafic magma (c.f. Smith et al., 2013).
Carbonatite Complexes with Dominant Ultramafic Rocks
(Sung Valley, Samchampi, Mer-Mundwara) Carbonatite-Lamprophyre Association
An alkali-picritic, magma was considered as the parental magma
Mahakoshal Supracrustals, Uttar Pradesh
for the complex (Krishnamurthy, 1985). Sen (1999) observed that Mg-
rich peridotite and pyroxenite of Sung Valley were initially fractionated The carbonate-rich dykes and plugs in ultramafic lamprophyres
from the parental melilitic magma, resulting in enrichment of calcium that are close to aillikite in composition (Srivastava, 2013) show
and generation of carbonatite melt by the process of liquid hypidiomorphic texture and mostly composed of calcite with
immiscibility. Based on detailed mineralogical and isotopic studies appreciable amount of silicate minerals like clinopyroxene, phlogopite
Srivastava et al., (2005) and Melluso et al., (2005) postulate that the and olivine (often pseudomorphed by calcite, amphibole and chlorite).
SVCC had several batches of primary magmas, with distinct magmatic A multi-stage veined mantle melting model has been suggested in the
suites or associations (see Table 1). Recent studies by Srivastava et early stages of rifting in the Mahakoshal region.
al., (2019) has indicated wide variations in the Sr - Nd - Hf isotopic
compositions (initial 87Sr/86Sr = 0.70472 to 0.71080; εNd i = –10.85 Pachcham Islands in Kutch
to + 0.86 and εHf i = –7.43 to +1.52). Calcite and apatite in the The basanite dyke, with oceleii of carbonatite in the Pachcham Is.

JOUR.GEOL.SOC.INDIA, VOL.94, AUGUST 2019 131

in Kutch (Ray et al., 2014) provide evidence for the ultra alkaline estimated with an average grade of 1.16% REE (Nanda et al., 2017).
rock - carbonatite genetic link, apparently as an incipient liquid- Additionally, this block contains 9,600 tonnes Nb2O5 at an average
immiscibility stage. grade of 0.08 % Nb2O5. These results indicate the high potential of
Amba Dongar carbonatite complex for both REE and Nb besides
Possible Sub-surface Carbonatitic Occurrences and Localities of fluorite and barite.
Doubtful Origin Other carbonatites complexes like Sevathur, Jokipatti, Samchampi
Suspected carbonatite bodies, in the Lower Narmada Valley, and Sung valley do contain minor amounts of REE minerals and can
following the discovery of Amba Dongar and Siriwasan based on the host significant REE resources. However, specific details on ore
works of Blanford (1869) and Bose (1884) prompted researches for grade and tonnage are not yet available.
detailed studies during the late 1960s and later years by Udas (1982)
and the present author besides others. These studies resulted in Sung Valley, Meghalaya
discoveries of several suspected carbonatite occurrences in western This complex had been evaluated for Nb and P hosted in pyrochlore
Madhya Pradesh, northern Maharashtra and Gujarat (Nos. 20, 21 and apatite in the late 1990s by AMD (Krishnamurthy et al., 2000). In
and 22 in Figure 1). The postulated carbonatite at Ariyalur (No. 25, recent years it is being explored for possible resources of rare earths
Table 1) by Grady (1971) also need to be evaluated. (Sadiq et al. 2014). Several REE minerals such as bastnäsite-(Ce),
ancylite-(Ce), belovite-(Ce) and britholite-(Ce) have been identified
ECONOMIC ASPECTS that are associated with calcite and apatite. The presence of REE
Carbonatites as a group are endowed with higher abundances of carbonates and phosphates associated with REE-Nb bearing pyrochlore
REE, Sr, Ba, Nb, Y, F besides other elements and are hosts to many further enhances the economic potential of the Sung Valley
world-class deposits of rare earth carbonates, pyrochlore, apatite, carbonatites.
fluorite and others (Mariano, 1989; Simandl and Paradis, 2018 and
references therein). Carbonatites of India also host a variety of Pyrochlore (Nb) Resources
economic mineral deposits, a few of which are actively being exploited
Samchampi Complex, Assam
and explored (Krishnamurthy et al., 2000). The different types of
deposits and resources that are being proved in India are briefly An area of 11 sq. km residual soils of Samchampi complex has
considered next. been evaluated for Nb resources. A total of 10.7 sq. km had been
evaluated in four blocks with depths varying from 1.24 m to 2.09 m.
REE Deposits A reserve of 20.949 Mt of ore with 12, 124 t of Nb, 2685 t of Ta and
1822 t of Y has been established (Hoda and Krishnamurthy, 2016).
Kamthai
Thus, Samchampi contains the richest pyrochlore resources so far
Based on detailed geological mapping, grid channel sampling and proved in India.
assaying for REE elements, a carbonatite-plug hosted REE deposit
has been proved at Kamthai (Bhushan and Kumar, 2013). The main Sung Valley, Meghalaya
REE minerals identified are bastanesite (La, Ce), synchysite (Ce), Pyrochlore occurs along with apatite in the residual soil of the
carbocerinaite (Ce), cerianite (Ce), ancylite and parisite. The maximum carbonatite complex. The pyrochlore is a thorium-rich type (with 8.5%
value of total LREE obtained in this deposit is 17.31%, with a mean ThO2) with less uranium (2.20% U3O8). In the southern part of the
of 3.33% and a weighted average of 2.97%. The carbonatite plug covers complex, where carbonatites are concentrated, a reserve of
about 19,475 sq. meters and the resources estimated up to a depth of 6.75 Mt of Nb ore with 0.02% Nb, over an area of 5 km2 up to a
84 m under proved, probable and possible categories amounts to about depth of 1 m has been established resulting in a reserve of 1300 t of
4.91 million tons of ore, making Kamthai as one of the best REE Nb (Krishnamurthy et al. op.cit).
deposits in India. Estimates of individual rare earths computed include
52,196 tons of La, 66,026 tons of Ce, 13,663 tons of Nd, 5,415 tons Carbonatites of Tamil Nadu (Sevathur, Samalpatti and Pakkanadu)
of Pr, 920 tons of Sm and 207 tons of Eu. Besides these REE, the Pyrochlore occurs in the ankeritic beforsite of the Sevathur
Kamthai resource will produce 551 tons of Ga, 44 tons of Ge and carbonatite complex. Exploratory and evaluation drilling was carried
1,12,830 tons of SrO also during its mining life (c.f. Bhushan and out in Sevathur during the early 1970s and about 360 t of pyrochlore
Kumar, 2013, p. 41). was proved for a strike length of 500 m and up to a depth of 250 m.
Pyrochlore with up to 23.8% U3O8 appears to be a U-Ta variety,
Amba Dongar, Gujarat transitional to hetchetolite and betafite with Nb2O5/Ta2O5 ratio of 9
This carbonatite-nephelinite ring complex has been extensively and Nb2O5/U3O8 ratio of 2 (Borodin et al., 1971; Krishnamurthy et
drilled since 2015 by AMD and since 2017 by GSI to seek REE and al., 2000). Since the pyrochlore was metamict and posed challenges
Nb resources from both the ankeritic carbonatites and the carbonatite in separation techniques, further exploration was discontinued.
breccia. Petromineralogical and XRD-studies of the carbonatites and Pyrochlore from other complexes are minor and has not been evaluated.
breccias had indicated the presence of REE minerals such as monazite,
thorite, cerite, synchisite and bastnasite, besides, rare earth fluoro- Apatite Deposits
carbonates, parisite, and florencite. Apatites occur in significant quantities, either as concentrated
Detailed chemical analysis of cores at 1 m interval and of primary bands within carbonatites or in the residual soils along with
composite samples from every borehole indicate homogeneity of pyrochlore and magnetite or as secondary enrichments (e.g., Sevathur,
mineralisation in the entire column up to an explored vertical depth of Newania, Sung Valley and Samchampi).
120 m. Except for a few lean zones, the entire column hosts REE
mineralisation of the order of >1% ΣREE with some zones at > 4 % Samchampi-Samteran, Assam
total REE. Taking into consideration these results, resource estimation At Samchampi, four large, lensoid bodies of secondary phosphatic
of a small block of 400 m x 100 m (0.04 sq. km) with an average rocks (c. 0.43 sq. km) occur along the curvilinear fault zone in the
depth of 113 m has been completed. Inferred REE resources of dominantly soil covered areas of the complex. Petrographic and EMP
c. 140,000 tonnes contained in 12.00 million tonnes of ore have been studies indicate that the fine grained fluorapatite is the dominant

132 JOUR.GEOL.SOC.INDIA, VOL.94, AUGUST 2019

phosphate mineral set in a groundmass of calcite and francolite. age groups, include: (i) the late stage veins in peralkaline syenite
Crandellite, pyrochlore, magnetite, ilmenite, goethite, biotite and complexes (e.g., Kunavaram, Elchuru); (ii) the diamond-bearing
zircon occur as accessory minerals. Major and minor oxides of the carbonatite-kimberlite bodies at Khaderpet and (iii) the
phosphatic rocks show wide variation in P2O5 (31.49-38%), CaO lamprophyre-lamproite dyke association (e.g., Pachcham Islands
(41.70-54.73%), Fe2O3 (1.40-11.16%), and Al2O3 (0.53-4.47%). Upper Cretaceous, Deccan Volcanic Province, and the
Trace element data indicate: total REE- 1518 ppm; U3O8-223 ppm; Proterozoic Chitrangi Group).
Nb-168 ppm; Y-69 ppm; Zr-674 ppm. The phosphatic rocks appear 4. A number of petrological associations that have close genetic
to have formed after some secondary enrichment processes (lateritic- links have been identified. These include the carbonatite-
type of weathering). Reserves of 15 million tonnes with an average nephelinite-phonolite (e.g. Amba Dongar, Sarnu-Dandali-
grade of 35% P2O5 have been established up to 10 m depth at Kamthai), dunite-peridotite-pyroxenite-ijolite-melilitite (e.g.
Samchampi (Hoda et al., 1997; Hoda and Krishnamurthy, 2017). Sung Valley), miaskitic syenite-pyroxenite ± dunite (e.g.
Sevathur, Samalpatti, Pakkanadu).
Beldhi-Kutni, Paschim Bengal 5. Dolomitic carbonatite with a well-developed fenite zones in the
Apatite ± magnetite and olivine (phoscorite) occur as lensoid Untala-granite at Newania, clearly indicates the source source
bodies in this complex. Large bodies of apatite-rich rock, possibly of the fenitising fluids, namely the carbonatites.
concentrated through solution activity occur intermittently along or 6. Sovites (calico-carbonatites) occur as the most dominant type in
close to the South Purulia shear zone. 16.6 Mt of apatite ore with an some ten (10) complexes. Beforsite (magnesio-carbonatite) is
average grade of 11% P2O5 has been proved and being mined from the dominant type at Newania and ankeritic-sideritic types are
this deposit (Basu, 2003). mainly found at Amba Dongar, Siriwasan and Newania.
7. The rare benstonite (Ba-Sr) bearing carbonatites are found at
Titano-Hematite Rock (THR) Jokkipatti and Udaiyapatti in Tamil Nadu.
8. Mineralogically the carbonatites show considerable diversity
Samchampi - Samteran, Assam
with some10-15 minor or rare minerals besides the major calcite,
Two large bodies of THR occur prominently (c.2.5 sq. km in dolomite or ankerite.
outcrop area) in the dominantly soil covered complex of Samchampi 9. Fenitised zones and types of fenites (Na, K and mixed) vary
that were emplaced in close proximity to the Kalyani Lineament widely since the carbonatites are emplaced in a variety of host-
during the upper Cretaceous (109 Ma). Petrographic studies rocks ranging from granitic, mafic, ultramafic, charnockitic
indicate that hematite is the predominant ore mineral with minor types besides basalts and sandstones.
amounts of ilmenite and accessory phases of perovskite, pyrochlore 10. Major, minor and trace element data, including the REEs, show
and crandalite. Ore textures exhibit well developed exsolution considerable diversity with some of the carbonatite bodies (e.g.
lamellae of ilmenite along the octahedral cleavage of the Munnar, Samalpatti ) with low abundances of the diagnostic suite
original magnetite that has been completely martitised. Based on of trace elements.
geological and geophysical studies (ground magnetics), a reserve of 11. Stable (δ13C and δ18O) and radiogenic (Sr, Nd and Pb) isotopes
75 million tons of THR has been inferred up to a depth of 30 m in clearly indicate the mantle origin of all the carbonatites and also
the Gangjang (I & II), Thulbhung ore blocks (Hoda and Krishnamurthy, the diverse types of mantle-sources (both depleted HIMU and
2014). enriched EM 1 and 2).
12. Petrogenetic considerations reveal three types of carbonatites,
Fluorite and Barite Resources namely direct partial melts from metasomatised mantle (e.g.
Newania), liquid immiscibility from carbonatite-nephelinite
Amba Dongar, Gujarat
association (e.g. Amba Dongar) and through fractionation of ultra
The late stage, silica-rich, fluorite-barite carbonatite hosts one of alkaline ultramafic and mafic association (e.g. Sung Valley; Mer-
the richest fluorite deposits in the world, with reserves of 11.6 Mt of Mundwara; Sarnu-Dandali).
ore averaging 30% CaF2 (Subramaniam and Parimoo, 1963; Viladkar, 13. A few suspected, surface and subsurface, carbonatite bodies found
1981). Fluid inclusion studies (Roedder, 1973) indicate that the fluorite in the Narmada zone and other areas (e.g. Ariyalur) need to be
precipitated from low-temperature solutions (100-200º C), which more critically evaluated.
penetrated the fractured roof of the domed-up carbonatite complex 14. Carbonatites of India that host significant resources include Amba
that intruded the basalts. Barite is recovered as a co-product of the Dongar (Fluorite, REE, Nb, P, Ba, Sr), Kamthai (REE), Sevathur
fluorite. The case for ‘carbo-hydrothermal’ solutions in carbonatite (Nb, P, vermiculite), Beldih (P, Fe), Sung Valley (P, Nb, REE,
complexes the world over thus becomes important as a mineralising Fe) and Samchampi (P, Nb, Ti, Fe, REE).
agent (Woolley and Kjaarsgard, 2008).
Acknowledgements: The author is thankful to Prof.. Shrinivas
SUMMARY Viladkar, who had worked on almost all carbonatites of India, for his
1. Carbonatite-alkaline rock complexes of India (25 nos.) are objective and critical review which enabled substantial reduction and
spatially related to deep main faults, rifts and terrain boundaries improvement of the MS. Ms. Prajakta Lavhale, Research Scholar,
that apparently facilitate their rapid ascent in the crust. Department of Geology, Savitri Bhai Phule Pune University and Dr.
2. The carbonatite complexes belong to two age groups, namely Dayananda, Department of Geology, Bengaluru University are thanked
Middle – late Cretaceous, subvolcanic –volcanic complexes (e.g. for helping with the illustrations used in this review. This publication
Amba Dongar, Siriwasan, Swangre, Mer-Mundwara, Sarnu- coincides with the Commemoration of Seven Decades of exploration
Dandali-Kamthai) and the Paleo-Neoproterozoic plutonic for atomic minerals by AMD (1949-2019) and is dedicated to all those
complexes (Newania, Sevathur, Samalpatti, Hogenakal, Kollegal, past and present workers of carbonatites and related rocks in India,
Pakkanadu, Udaiyapatti, Munnar, and Khambamettu). The especially those from AMD led by late Dr. G. R. Udas, my Guru.
middle Cretaceous Sung Valley and Samchampi complexes also
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(Received: 13 March 2019; Revised form accepted: 3 May 2019)

138 JOUR.GEOL.SOC.INDIA, VOL.94, AUGUST 2019