Multi-Phase Manganese Mineralization in the Noamundi Synclinorium, East Indian Shield

Manganese mineralization associated with phyllites in and around Joda, Odisha belongs to the Iron Ore Group of Noamundi basin and is a part of Jamda-Koira belt of East Indian Shield. The present study area comprises low to medium grade tectonites containing economic resources of both iron and manganese. Present study is concentrated on Manganese mineralization. Field study and petro-mineralogical observations reveal syngenetic character of manganese ores comprising lowT higher oxides viz. pyrolusite, cryptomelane, manganite as major Mn-minerals along with highT lower oxides viz. jacobsite, bixbyite, braunite and hausmannite as minor Mn-minerals. The Mn-ore bodies and associated phyllites have undergone multiple phases of deformation and metamorphism followed by hydrothermal and supergene processes. Four deformational phases have been deciphered during field study. Geochemical analyses of ores and phyllitic host rocks show high values of Al2O3, TiO2, Ba, Co, Ni, Cr, Cu, Sc, V, As, Zn but depletion of Sr, Yb, Sm, Nb. Geochemical data infer ores to be a recycling product originally derived from a mafic crustal source of tholeiitic character. Age data obtained from Sm-Nd ratio of two rock samples are 3.46 Ga and 2.79 Ga. Present work provides a critical assessment on the multiphase mineralization of manganese ores.


Regional Geology and Stratigraphy
The East Indian Shield (EIS) (21°25°N lat. and 85°-88°E long) comprises two Precambrian cratonic blocks viz. the northern high grade metamorphic Chhotanagpur Granulite gneiss terrain and the southern low grade metamorphic Singhbhum Granite greenstone terrain, which are separated by the Singhbhum Orogenic Belt containing Dalma lavas and Singhbhum Group of rocks. Figure 1 shows the geological map of the EIS. The Singhbhum granite greenstone terrain is bounded by Singhbhum shear zone (200 km long) in the north and separated from the Proterozoic Eastern Ghat Mobile Belt by Sukinda thrust in the south. The generalized Stratigraphic succession in this Singhbhum craton after Saha et al. (1988) is given in Table (Chakraborty & Majumder, 1986;Saha, 1994;Bhattacharya et al., 2007;Mukhopadhyay et al., 2008). IOG rocks are low grade metamorphosed and intruded by younger Singhbhum Granite (Type-B). Bonai-Keonjhar iron-manganese belt (Lat: 21°40' and 22°15' N and Long: 85°00' and 85°35' E) in the IOG forms a 60 km long & 25 km wide synclinorium (Noamundi synclinorium), referred to as "Iron-Ore horse shoe" plunging variously to north and north east. The corresponding anticlinal core in the western part of the Noamundi synclinoriumis mainly occupied by the 3.3 Ga Bonai granite (Saha, 1994). BIF, which is an important volcano-sedimentary rock formation of the Archean Greenstone belt, broadly defines the outline of the synclinorium, are almost continuously exposed along the margin, while manganese ore bearing shales occur within the core region of the fold. The entire region displays the effect of superposed folding on two near perpendicular axes, the generalised trends being NNE-SSW & WNW-ESE to NW-SE (GSI report on manganese ore, 2011). Mn-mineralization in and around Joda has taken place in Joda, Bichakundi, Khondband, Guruda, Joribar and Bamebari areas.

Previous Work
Manganese mineralization in the Noamundi-Jamda-Koira belt is a very conspicuous feature in close association with iron ores. Spencer (1948) considers manganese ores hydrothermal in origin but Sen (1951) regards them to be submarine volcanic origin. Engineer (1956), Prasad Rao andMurty (1956) consider the manganese ores products of the replacement of shales and quartzites by manganiferous solutions. Basu (1969) considers these ores syngenetic but modified by epigenetic concentration. Basu (1969) and Roy (1978) describe bedded manganese orebodies interstratified with shale (often www.scholink.org/ojs/index.php/ees Energy and Earth Science Vol. 3, No. 1, 2020 29 Published by SCHOLINK INC. tuffaceous) and sometimes co-folded with it from Kalimati, Phagua, Gurda Block II and the Mahulsukha mine-areas in Odisha (cf. Roy, 1981). Murthy and Ghosh (1971) reported pyrolusite-cryptomelane-manganite-rhodochrosite bearing Mn-ores in association with chert and dolomite beds and regarded the manganese minerals originally disseminated in the shales and later mobilized and concentrated at structurally favourable sites. Banerji (1977) concluded that manganese ores formed later than the iron ores. Subramanyam and Murty (1975) and Banerji (1977) suggest a volcanic source for the manganese deposits. Banerji (1977) stratigraphically characterized iron-manganese mineralization in the Jamda-Koira belt as the Noamundi Group of much younger age (c.1500-1100 Ma) with the following sequence (ascending order) lower shale (tuffaceous shale-phyllite), banded hematite jasper, upper shale (manganiferous shale, tuff and chert), basic intrusion, grinitic activity. Saha (1962, 1977) described manganese ore bodies intimately associated with unmetamorphosed shales (occasionally tuffaceous) and chert of the Archean IOG.
According to Roy (1981), Mn-oxide deposits are intimately associated with unmetamorphosed shales (occasionally tuffaceous) and cherts of the Precambrian IOG rocks and the manganese ores are of dominantly lateritoid type having mainly pyrolusite and cryptomelane with local manganite. There are a number of manganese ore bodies within chert and/or shale as layers and lenses (Banerji, 1977;Mohapatra et al., 1996;Mishra et al., 2006). Mishra et al. (2006) classified the IOG manganese orebodies into stratiform, stratabound, and lateritic types. The stratiform type has distinct lamination or banding, and is often co-folded with shale. The stratabound type is structure-and shear zone-controlled and is often silicified. These ore bodies occasionally cross-cut the bedding planes of the host shale.

Methodology
Samples of various types of ore and associated host rocks are collected from the open-pit mines and surrounding areas for geochemical analyses and isotopic studies. for variable mass fractionation to a value of 1.17537 for 152 Sm/ 154 Sm also using the exponential law.
Sm/Nd isotopic studies are done by ICP-SFMS at the Canadian laboratory of the Australian Laboratory Services.

Mode of Occurrence and Structural Disposition of Manganese Ores
Manganese ores occur as massive, thinly laminated or lenticular stratabound bodies hosted by differently coloured (red, pink, yellow, brown, purple, smoky grey, etc.) phyllites which are kaolinised in many parts to different degrees. Large deposits of manganese ores are being mined in Bichakundi (near Joda), Khondband, Bamebari, Guruda and Joribar areas in the eastern part of the Noamundi synclinorium. In Khondband and Guruda areas manganese ore bodies are very closely associated with iron ores. The massive Mn-ore bodies show typical colloform structures (often pisolitic and botryoidal). The ore bodies, in places, are co-folded with phyllites forming mesoscopic synforms and antiforms.
In the Joda area, manganese ore bodies are mainly hosted by phyllitic rocks with minor quartzites. The lenticular bands of manganese ore are conformable with the host phyllites. The phyllites are, in places, laminated, compositionally banded and often showing brecciated character (Figure 2a). The laminated phyllites are light coloured and mainly composed of very fine-grained phyllosilicates with intermittent occurrence of ferruginous chert. The geological field work reveals manganese ore bodies to be of four different types viz. massive, banded, colloform (pisolitic/botryoidal/reniform) and brecciated. In the quarry section, manganese rich ore pockets are overlain by ochre which in turn is capped by lateritic horizon (Figure 2b). At places, a high degree of strain has produced folds with rootless intrafolial character (Figure 2c). The associated iron ore bands comprise mainly hematite or martite with variable amounts of goethite and minor amounts of magnetite and siderite. Hematite-rich iron ores often show typical BIF character accompanied by strong deformational events (Figure 2d). The gangue material is principally composed of cherty silica (in the form of jasper or quartzite) and kaolinitic clay.
The manganese ores and associated host rocks bear the evidence of multiphase tectonic deformation. The F 1 and F 2 folds are more or less isoclinal and axial plane dipping towards NW or SE. The F 3 fold is transverse and superposed over F 1 and F 2 and is much more open in character with axial plane E-W in general. The major Mn-ore bodies are mainly localized in the axial zones of the F 2 folds (Figure 2e), thin manganese ore bands are concentrated along the S 2 axial plane (Figure 2f). The F 2 fold axis plunges 7⁰ to 40⁰ towards the NNE or the SW with local variations towards the NNW, E and ENE. Manganese ore bands are also co-folded with the host phyllite forming mesoscopic synformal and antiformal structures (Figure 2g & 2h). The F 2 fold of the ore bodies can be categorized in Class 2 of Ramsay's geometrical classification of folds (Ramsay, 1967 WNW mainly with variations of W, NW and SE. The D 3 phase was further followed by a phase of faulting and shearing (D 4 ) (Figure 2j) which formed a number of sets of faults in this region among which at least three sets of faults are discernible in the field, the attitudes of which are as follows: i) 60⁰ to 85⁰ dipping towards W to NW.
ii) 8⁰ to 10⁰ dipping towards SE to NE.
iii) 60⁰ to 65⁰ dipping towards the SW.
The fault and shear zones are mostly in filled with pyrolusite-cryptomelane-chert association and fault breccias (Figure 2k). Although the Mn ores are not uncommon along the S 0 and S 1 planes, the ores are primarily concentrated in the F 2 hinge areas. Thinning of the ore bands at the limbs and thickening of the same at the hinge are very frequent in the manganese ore mineralized zone. The folded ore bodies have two general axial trends NE to ENE and SW to WSW. The axial planes of these folded ore bodies dip between 40⁰ and 72⁰ towards NW or SE. In these areas, the ore bodies also plunge along the F 2 fold axis (Figure2l).

Mineralogy and Petrography of Manganese Ores
Study under microscopes (both reflected and transmitted light) reveals that the predominant manganese ore minerals are pyrolusite, cryptomelane and manganite. Braunite, bixbyite, jacobsite and hausmannite occur mainly as minor phases. Minor iron ore minerals like hematite/martite and goethite are also present.
Two generations of axial plane cleavage have been identified in the manganese ore. The first-generation cleavage (S 1 ) is conformable with the compositional banding/bedding (S 0 ) whereas the second-generation cleavage shows transgressive relation with S 0 and S 1 planes Manganese ore gets mainly concentrated along the F 2 hinge area (Figure 3a). The micro-folded veins of pyrolusite forming

Major Element Geochemistry
The average silica content in ores and associated phyllites (except 93% in one sample of Bamebari  The average Ba content varies from 205.6 ppm in host rocks to 1012.85 ppm in ores (maximum up to 2960 ppm) respectively. The average Pb content varies from 10 ppm in host rocks and 26.8 ppm in ores respectively. The average Cs content is 2.18 ppm and Cs is probably derived from psilomelane-rich ore.
The average Rb content is 65 ppm, Rb generally replaces K and is always associated with potash bearing minerals. Chondrite normalized (after McDonough & Sun, 1995) Trace element pattern of manganese ores and associated rocks shows positive Co, As, Rb, Ba anomaly ( Figure 7).

Rare Earth Element (REE) Geochemistry
The manganese ores and associated rocks of the Joda area are analyzed using Inductively Coupled Mass  Haskin et al., 1968; Figure 8a) and also with average upper continental crust (Taylor & McLennan, 1981; Figure 8b).
Both standard-normalized REE patterns exhibit similar trends. The diagrams depict an overall depletion of LREE and relative enrichment of HREE, an exception for an ore sample with diminished HREE value that can be attributed to preferential leaching of HREE by meteoric water in oxidized ores. The most significant feature of the REE pattern is the positive Eu anomaly of the ores and associated rocks. The average Eu/Eu* and Ce/Ce* values are 1.16 and 0.8 respectively.
In TiO 2 -Zr/(P 2 O 5 *10 4 ) discrimination diagram (Figure 9), there is a complete separation between the fields of tholeiitic and alkali basalts with alkali basalts plotting in the field of low Zr/ P 2 O 5 and high TiO 2 .

Sm-Nd Isotopic Studies and Age
Two rock samples are analyzed for Sm and Nd by isotope dilution. The details of the analytical results are given in

Note. 1) Uncertainty in Nd isotopic composition is 2 Standard Errors; 2) TDM is the Depleted Mantle
Model Age in Ga calculated using the linear model of Goldstein et al. (1984); 3) ε Nd 0 is the epsilon 143 Nd value calculated present day.

Manganese Ores and Associated Rocks of Joda Area (Blue Triangles Indicate Ores and Green
Stars Indicate Associated Host Rocks)

Discussion
The Joda-Noamundi sector in the eastern limb of the Noamundi synclinorium contains significant manganese mineralization. Different tectono-metamorphic events are characterized by distinguished ore mineral assemblages belonging to that particular event.

Deformation & Metamorphic Events
The earliest deformation and metamorphism event (D 1 /M 1 ) are characterized by the ore mineral assemblage of braunite-bixbyite-jacobsite-hausmannite. The D 2 /M 2 event is characterized by the ore mineral assemblage of pyrolusite-psilomelane-hollandite. D 3 stage bears no significant manganese mineralization whereas the post D 3 event is characterized by the hydrothermal pyrolusite-psilomelane-chert association occurring along the faults and shear planes. At the final stage of manganese mineralization, supergene activity/lateritization has formed the ore mineral assemblage of polianite-pyrolusite-psilomelane-manganite-goethite precipitated from colloidal solution replacing earlier manganese minerals. The presence of jacobsite-hausmannite assemblage along with triple junction shown by recrystallized bixbyite grains infer that the peak metamorphic condition during D 1 /M 1 attained upper green schist to amphibolite facies, if not higher.

Major & Trace Element Analysis
Strong positive correlations between Sc and Al 2 O 3 (Figure 4a), V and Al 2 O 3 (Figure 4b), Cr and Al 2 O 3 (Figure 4c), Th and Al 2 O 3 (Figure 4d), Ga and Al 2 O 3 (Figure 4e), Nb and Al 2 O 3 (Figure 4f) indicate their clastic/detrital origin along with Al 2 O 3 . The relative enrichment of Sc, V, Cr in comparison with average Zr & Th contents indicates the source of clastic materials to be of basic magmatic affinity. On the other hand, Co, Ni, Cu, Zn do not show any appreciable variation with SiO 2 and Al 2 O 3 contents of ores and associated rocks signifying that these elements are not directly linked to terrigenous clastic inputs. On ternary diagrams like Fe-Mn-10 (Ni+Co+Cu) (Figure 5a) (after Bonatti et al., 1972) and Zn-Ni-Co (Figure 5b) (after Choi & Hariya, 1992) and binary diagram Co/Zn versus Co+Ni+Cu (Figure 5c) (after Toth, 1980) and the geochemical data of the ores and host rocks plot in the field of hydrothermal part which depicts a significant role of hydrothermal activities for the enrichment of these highly compatible elements in ore formation process. In the case of chemically incompatible elements, the correlation coefficients for regression lines that pass through the bulk composition and origin can be used to select the most immobile element pair (MacLean & Kranidiotis, 1987). High field strength elements like Nb, Ta, Zr, and Hf, which are widely considered to be immobile, correlate highly with each other in manganese ores of the Joda area. Sedimentary environment and alteration can shift the immobile element concentrations but have little effect on inter-element ratios, which are controlled largely by the source of detritus in the rocks. Within the analytical errors, the chemically incompatible elements Nb, Ta, Hf against Zr plot on regression lines through the origin (Figure 6 a, b, c). This means that these elements are geochemically coherent and remain immobile during the ore-forming secondary processes. Pb is assumed to be derived from cryptomelane. Both Ba and Pb do not vary systematically with Al 2 O 3 and SiO 2 contents inferring their source to be hydrothermal activities at later stages. Samples of Algoma-type BIF of early Archean age (3.8Ga) from Isua, west Greenland, have Ni values as high as∼58ppm (Dymek & Klein, 1988). High abundances of Ni and Cr are also reported from several Archean clastic sedimentary rocks, and are generally explained by the presence of an ultramafic source (e.g., Fedo et al., 1996). In the Joda area, average Ni and Cr contents are 100.5 ppm & 219 ppm respectively. This is more akin to the Algoma type character. The relative enrichment of Ti, Zr, Sc in comparison with Th possibly infers a recycling product of earlier volcanogenic metabasic rocks.

REE Analysis
Manganese ores and associated host phyllites comprise a low overall abundance of LREEs and a flat pattern of HREEs. The lack of marked differentiation between LREE and HREE hints for a basic affinity as mafic or ultramafic end-members are characterized by small degrees of light-heavy REE fractionation. It is observed that there is a small positive Eu anomaly (1.16) and negative Ce anomaly (0.88). Attenuated Eu anomalies account for a more dominating mafic source. Manganese ores of the present area show HREE enrichment, negative Ce anomaly and positive Eu anomaly which are similar to modern ferromanganese sediments near mid-oceanic ridges (Barrett & Jarvis, 1988 seawater Ce is removed as CeO 2 or Ce (OH) 4 by oxidation reaction. Modern seawater has LREE depletion and negative Ce anomaly (Douville et al., 1999). A positive Eu anomaly is also a typical characteristic of modern manganese hydrothermal deposits in the ocean (Hodkinson et al., 1994). As with the increase of terrigenous components the Ce/La ratio increases, the average value of Ce/La ratio (1.79) in the manganese ores indicates inclusion of volcaniclastic components, suggesting that the REE pattern and the Eu anomalies of the manganese-iron ores in the area are influenced by the mixing of Mn rich sea water and volcaniclastics (Mishra et al., 2007). The process of lateritization can also promote the loss of REE to some extent (Moriyama et al., 2008). The REE patterns shown by the ores and associated rocks represent the end product of a complex series of events that record the properties of the Mn rich solutions subsequently precipitated with volcaniclastic sediments. The TiO 2 -Zr/(P 2 O 5 *10 4 ) discrimination diagram reveals the tholeiitic character of the basic rocks which acted as the major source for derivation of the ore-forming elements. Alkali basalts have higher P 2 O 5 than tholeiitic basalts for a given Zr content. Thus, it can be postulated that the ultimate origin of the ore and associated host rocks is clearly linked to magma of basic composition with prevailing tholeiitic character.
Banerji (2002) considered a major part of the materials of the IOG rocks was deposited in the miogeosyncline derived from the offshore zone of fracture and volcanism. Evidence of earlier crust is also recorded in detrital zircons from supracrustal rocks of these Archaean Cratons, e.g., ~3.62 Ga from Singhbhum Craton (Goswami et al., 1995;Misra et al., 1999). According to Dunn (1940), Dunn and Dey (1942) and Sarkar and Saha (1977) all the iron formations of Bihar and Orissa belong to one group.
According to Saha et al. (1988), around 3.2 Ga there was a development of a tensional regime on either side of Singhbhum Granite (3.3 Ga) following which the BIF were deposited in these basins where SBG acts as the basement of IOG rocks. On the other hand, Baidya (2015) suggests 3500-3200 Ma age of the Iron Ore Group when the greenstone belt was formed with concomitant volcanism, sedimentation and ultramafic-mafic magmatism. The oldest granitoid is referred to as the Older Metamorphic Tonalite Gneiss (OMTG, ~3.4 Ga; Saha, 1994;Goswami et al., 1995;Acharyya et al., 2010) that includes enclaves of meta-sediments and meta-volcanics designated as the Older Metamorphic Group (OMG). Sm-Nd isotopic data from the present work indicates the possible maximum age of the rocks (BIF) in Joda area is 3.46 Ga definitely older than the SBG-type A (c. 3.3 Ga) which acts as the basement of IOG rocks. Supergene alteration and hydrothermal activity at later stages may have been attributed for relatively younger age (2.79 Ga) of banded cherty phyllite. The limited age data of the present study possibly infers that manganese ores and associated rocks are likely to be recycled from still earlier greenstone belts.

Conclusion
In addition to megascopic and petrographic analyses, the major, trace and rare earth element geochemistry of the manganese ore and associated phyllitic host rocks of the present area confirm the chemistry of the samples as well as the composition of the source material indicative towards a parent magma of basic affinity. The presence of high temperature mineral assemblages (Jacobsite-hausmannite) in pyrolusite-cryptomelane rich groundmass indicates an earlier high-grade peak metamorphic condition.
Manganese, iron and some silica were deposited initially as chemical precipitates in the basin. Major oxides Al 2 O 3 , SiO 2 , K 2 O, MgO, Na 2 O and TiO 2 appear to be contributed from volcaniclastics and terrigenous detritus. Trace elements appear to be controlled by adsorption on the precipitating Mn and Fe oxides or hydroxides. The manganese ore bearing BIF deposits in a greenstone belt with evidence of volcaniclastic association postulate that BIF hosted manganese-iron ores in and around Joda are akin to Algoma character rather than Lake Superior type. REE distribution pattern, positive Eu anomaly, negative Ce anomaly, Ce/La ratio all indicating a mixing of basic volcaniclastic material with the chemically precipitated ores. Hence, it can be concluded that a basic magma generated in an extensional tectonic set up in Archean time acted as the initial source of present-day ore and associated host rocks of Joda area. These rocks were later subjected to several stages of deformation and metamorphism with subsequent hydrothermal activities and supergene alteration/lateritization leading to further recycling and enrichment of manganese in younger ore formation.