Iron Ore Deposit of Orissa-Jharkhand Region (With Map) | India | Metallurgy

Since times of the Jones (1934) the Iron ore deposits of Orissa and Jharkhand have received great attention due of their being high grade and large size. Here mining is done by simple quarrying. If the present day production of a very high scale, these ore deposits continue at this rate, then they would be exhausted in the near future. This may make imperative to mine out lower cut-off grade and also go for ore beneficiation.

In India most of the Proterozoic iron ore deposits are stratiform and hematitic like the rest of the world. The planar features of the ore bodies are parallel to bedding of BIF. Clashes are mostly absent and fine-grained shales exist above and below BIF. In the field the ore bandings thin or thicken (from mm to even 0.3 m.) and are parallel to bedding of BIF to start with and hence produce sediment-type-stratiform deposit.  

These deposits are mostly associated with sedimentary BIFs of Achaean to Proterozoic age; the grade of deposits increases with time. Each deposit is continuous, uniform and homogeneous, based on their chemical sedimentary characters and includes the gangue minerals which downgrade quality of the deposits. Hence primary and secondary processes upgrade deposits by enriching the grade due to beneficiation is now being adopted by several mining companies operating in the region.

Regional Geological Pattern of the Singhbhum-Orissa Region:

Geology of the Singhbhum-Orissa region has been one of the best geologically studied regions of the country because of Noamundi and Gua iron ore deposits (extension of Orissan iron ore district) and Gorumahisani, Sulaipat and Badampahar iron ore deposits (in Mayurbhanj dist. Orissa) as well as for the copper and atomic mineral deposits of Singhbhum shear zone that discontinuously extend upto Dakura, 16 kms south of Baripada in Mayurbhanj district.

The Iron Ore Super-group-bearing northern Orissa is separated from Talchir Gondwana rocks and Eastern Ghat Super-group by Sukinda Thrust zone (northern fault of Gondwana basin). The iron ore district of Orissa-Jharkhand is, thus, confined to the Singhbhum-Sukinda thrust belts in the north and south (Figure 5.1).

The Iron Ore Super Group (IOSG) has three stratigraphically horizons of BIFs in space and time, which are structurally, stratigraphically, mineralogically, petrologically, metamorphically and ore-deposit-wise different from each other. The following description is from Acharya (2008).

BIF-1 is narrow, Banded Magnetite-quartite (BMQ)-type, thin banded and extensive from Pallahara to Gorumahisani with Amphibolite fades metamorphism (grunerite) and often higher and exhibits at least 6 periods of deformation but with no big ore deposits so far known. BIF-2 forms Daitari-Tomka basin that dies out at Harichandanpur.

It has three periods of deformation and suffers higher phase of green schist fades of metamorphism. BIF-3, the ‘Horse-shoe’ basin (Joda-Koira Basin as JKB) is the youngest with Dhanjori Sandstone and younger volcanics at its base. It has the best grade and extensive ore bodies each of more than one km in length at times. With not much of complicated folding, the basin forms independently with youngest BIF (BIF-3) in the entire region and the thickness of bands of hematite/chert exceeds 30 cms at times.

GHSV Prasada Rao (1964), had recorded more than one BIF horizon in this entire region and significantly the opinion on Kansa quartzite, south of Daitari deposit to be of Dhanjori age and not of Kolhan as recorded by him earlier is very important in recasting the regional stratigraphy. A two-tier system was suggested by Banerjee (1974) whereas Acharya (2005) conceived of a three-tier system.

This has been found to be valid by repeated field checking when the second one has been observed to be intermediate to BIF-1 and BIF-3. An unconformity runs between the rocks of Daitari basin and Dhanjori sandstone, which, at different places, has acted as an angular unconformity, disconformity and nonconformity. BIF-3, is post Dhanjori sandstone and volcanics in the intra-cratonic basin between Singhbhum-Granite Complex (SGC) and Bonai granite.

Large deposits associated with BIF-1 are not yet known. But the BIF is magnetite- rich and structurally complex. They, with the associated rocks show upto sillimanite and kyanite grade of metamorphism. The thickness of the BIF is less in comparison to its length. The ore minerals are essentially magnetite and secondary ones. Jasper and chert almost do not exist since they are recrystallised.

BIF-2 forms Daitari-Tomka basin but is often considered as the same as BIF-1. Detailed field mapping shows structural inequality, mineralogical difference, and stratigraphic dissimilarity, metamorphism presence of large and small ore bodies associated with BIF-2 to bring forth the difference.

BIF-3, the Joda-Koira Basin (JKB) forms a small, shallow but highly rich iron and manganese ore basin that forms a ‘U’-shaped exposure of BIF, northern part of which comes under Jharkhand State. Its western limb extends further north to turn westward upto Chiria (the largest single Iron ore body of Asia) and then runs southward. Although the ‘Horse-shoe’ is normally considered separately a basin-wise discussion should mention about the Jharkhand part of the basin. BIF-1 has its remnants north of the copper-thrust zone irregularly.

While the western limb of the ‘Horse-shoe’ is isoclinally folded with dip westward the rest of the basin have open-folds of three generations i.e. with early E-W, NNE- SSW and later E-W axial planes. Occasional conjugate folds occur at different parts of the basin.

This basin, developed between Singhbhum and its equivalent Bonai granites (B.G.) is caused by a series of faulting in between causing the basin to form and the faults were channels for volcanic material after the sedimentation of Dhanjori sandstone around the SGC.

The supplied materials come from the granite complex pointing to a huge amount of erosion of SGC. The fracture-system in the basin extended towards SGC with the dolerite dykes. Keonjhar-Nuakot basic flows forming the western border of the BIF-3 basin are fissure-eruption material.

Kolhans overlapped this basin un-conformably in the north though a few outliers were recorded even up to Khandadhar top and off Nandigura peak by in folding of rocks and later weathering. It thus, indicates a post-Kolhan deformation or a post- deformational at Kolhan deposit.

The ore bodies are mostly on the hilltop, above and inside BIF and below BIF and above lower shale. Thus, they are supra- intra- and infra- to BIF. The upper shale does not exist normally on the hilltops and, if and when so, gets lateritised or is removed out by weathering. But BIF naturally forms the ridges controlling the geomorphologic evolution and becoming the mother-rock of ore deposits. The BIFs show microbial evidences in support of iron precipitation. This has not found to develop in BIF-1 and marginally so in BIF-2.

Field Disposition and Structure of Iron Ore:

Ore deposits of sedimentary association, like that of iron ore, one finds parallelism of extension of ore bodies and BIF when the former is syn-sedimentary. This relationship broadly exists even if later enrichment makes it wider and thicker. In Gandhamardan, Jajang, Malangtoli, Thakurani, Kurbandh and many such localities broad infra- or supra-BIF deposits exist in such fashion. Even depending on chemical precipitation such a framework remains as one sees at Tomka.

Due to diagenesis when post-sedimentary enrichment process is introduced, banded chert gets enriched with hematite or replaced by iron-oxide/silica, subsequently metamorphism brings in recrystallisation of new ore minerals are formed while the gangues partly get removed.

Structure Framework of Iron Ore Group:

Iron ore group rocks show folding. The pre-folding ore deposits exhibit structural elements printed on them that suggest the direction of extension of the ore body in addition to their deformation and trend in local exposures.

On computing several of them the regional structural behaviour can be known, which in turn, gives clues to successful mining. Thus, folding of fold axis of B2-folds (NNE-SSW) indicates south/northward plunge/s of ore bodies and later (EW) folds behave accordingly depending on culminations and depression of the set up.

Of the three phases of folding in BIF-3 basin (JKB), the first-EW fold is very local in the south, (Dubna and Khandadhar) the second E-W fold causes folding of fold- axis of the earlier and this regional NNE-SSW fold; control the depth of ore bodies and stratigraphic depth loses its significance due to the folding of its axis.

Plunge directions change 180° and consequent migration of material causes thickening and thinning of the band/s of minerals. Faults have controlled the linear extension, disappearance of units, geomorphology, litho-dispositions and are also responsible in creating chaos in the run of the fold-axes as well.

The JKB has at least seven important mutually related NNE-SSW faults, statistically parallel to each other as found in Bonai granite (BG), JKB and SGC. Their roles are discussed in different sectors. In the south the upthrow has brought in northerly plunge.

The basin exhibits thinning down of BIF from three directions towards the middle part where it practically vanishes out when the lower and upper shales are in juxtaposition. The projection of the So-surface (Bedding plane) can only distinguish them in the field. The three sections drawn show the open-nature of the folds of JKB (Figure 5.3). In the western limb, folding is isoclinal, dipping west.

The Daitari ore body is co-folded with the rocks and plunges and extends in the same way as the associated rocks. So is the case of Tomka deposit but with different direction or plunge. The former is infra-BIF in nature while the latter is intra- and supra-BIF. Intra-BIF small deposits exist north of Baghiathali Parbat upto Harichandanpur discontinuously and also at Champajhar, Tungaisuni and Kalisagar (Figure 5.4).

Faults are important in controlling up-gradation of deposits. It is of interest to note that in Daitari basin iron ore mineral rich BIF with a fault shows enrichment of fault zone with iron material. With no ore mineral bands- there is no secondary enrichment of faults.

BIF, in Daitari basin, even shows no or very little ore mineral bands for kilometers and the analysis showed only 2-3 per cent of iron in the BIF. This may bring in the question of it being considered as BIF. But along the strike this change of mineral fades does exist (Figure 5.5).

Faults are of immense importance than hitherto realised. They complicate folded rock exposed differently. Older and younger shales (without BIF in between) become difficult for identification. Folding of the fold-axes, folding of fault planes, right side up position of rocks etc. are made difficult for interpretation if continuous mapping is not done in the basin. Thus, it may look strange to observe that shales at Dalki, Fagua,

Joda-west, Inganjharan (joda-east), Dubna-Gonua sector, Rajabasa, Mahulsuka, Patmunda and Koira etc. show older shale with Mn-ore bodies’. Faults even show opposite sides thrown differently causing problems of mapping and interpretations. These faults are found to horse-tail with branches going in different directions.

After checking the roles of structure and stratigraphy in shaping the 3-D configuration of the ore bodies, planning for exploration should be done.

A good part of the shales exposed inside the basin is older shale, which shows certain disturbances uncommon to the upper litho-horizons; this partially explains the complicacies in sequence stratigraphy. The main faults have brought forth sudden depths of the basal floor in the intra-cratonic grabenised basin inside which manganese bearing sediments were filled and later remobilized along the reactivated faults to cause the formation of manganese ore deposits of excellent grade below BIF. (The case of Kachha is one of the good examples). Except a few, towards the middle part of the basin, almost all Mn-ore deposits are fault-controlled. Horse tailing of faults result in cobalt and nickel mineralisation in them as well.

Field occurrence of the BIF deposits in different mines in the region is shown in Figures 5.6a-g.

Most of the shales show a percentage of tuff in them suggesting volcanic activity throughout the period of sedimentation; that even outlasts the younger shale. Volcanism, thus, is pre, syn- and post-basinisation and later evolution.

This brings in the possibility of the role of exhalations during the sedimentation history of the basin. Mn- ore- mineralogy supports the idea as well. Quantification of the ore – deposits -volume, when done, may show if the provenace could have supplied the total amount. An exhalation theory is otherwise, and also normally, should, therefore, be accepted.

The presence of todorokite in Mn-ore supports this view. Like BIF, that shows alternations of chemical bands of iron oxides and silica in the lower shales of Dubna and Churisahi quarries, banded manganese formation does exist.

It is partly chemical, though mostly mechanically formed layers of fine shale due to repetition of incoming Mn-mineral from the medium with fluctuations of Eh and pH indicating formations of Mn-protore was completed prior to the precipitation of the overlying BIF, the former being shaly, is not physiographically prominent and can be traced only in freshly quarried mines while BIF, in contrast, forms regional hill ranges.

Condition of Migration and Deposition of BIF and Iron Ore:

Most of the ore deposits of iron are stratiform and run grossly parallel to BIF while Mn-ore bodies appear along fault planes as well in addition to being syn-sedimentary. At Cheliatoka peak a sizable piece of current bedding feature was found and at two other places BIF showed features simulating current bedding in the basin although plenty of penecontemporaneous deformation feature are available.

These agree with the regional pattern of the basin. The BIFs, therefore, suggest a stage of provenancial peneplanation to account for chemical sedimentation. Volcanics and tuffs support an exhalative hypothesis that takes deeper root because of mineralogy and existence of volcanism in the entire time-span (pre- to post- sedimentation).

Shale patches inside BIF formations are considered regular because clearing of suspended material (like-shale particles) cannot be guaranteed and a flutter in them often may result in shale deposits as intra-BIF occurrence. In normal stratigraphy banded hematite shale is rather commonplace before and after BIF precipitation acting almost as end members with BIF in the center as beginning and end of chemical sedimentation of BIF as a unit.

The provenance of this basin means granite and basalt with older metamorphic complex. While the role of granite may not be that important, the role of volcanics is very valuable. The Keonjhar-Nuakot volcanics shows ≈2 per cent Mn-Oxide while Sandur volcanics (southern India) gives ≈ 7 per cent Mn that shows its reappearance as Mn-deposit in the lower sediments. Add to it the exhalative materials, the answer is then found. In the case of iron, things are somewhat different.

A huge hydrous fluid system has to be brought about to account for transport and migration of metal content to the basin with suitable Eh and pH conditions (a changed P-T milieu) for deposition of oxide of iron sufficiently to form an ore body. Later influx of material enriches the ore- body- grade and also volume.

The capsule is not only fittingly suitable to this basin but also offers an excellent concept to account for the origin and exponential enlargement of size of the ore deposits. Leep and Goldrich (1964) have shown the metal supplying capacity of even granites. The volcanics, capable of a volume-wise better supply, can certainly be counted for more iron for BIFs and ore bodies.

Under normal conditions chert and iron oxide components in BIF are chemically formed and are considered original because their distribution is not controlled by extraneous factors like: metamorphism, deformation, depth of burial, proximity to intrusion, (the basin has only one ultrabasic and a few dykes of late state intrusion).

This is, therefore, superbly suitable for study to conceptualise ideas on formation, evolution and genesis of rocks as well as associated ore deposits. The sedimentary (chemically controlled) and penecontemporaneous deformation feature like current bedding at lower ore body of Gandhamardan and just below Cheliatoka peak and a somewhat larger feature on the last turn of the stream before the Khandadhar fall of Sundergarh district, ‘flowery features’ and ‘flame structures’ at Mankarnacha and many other places, ‘cut and fill’ feature in BIF at Kuradih nala, west of the ridge and a host of many diagenetic feature almost everywhere suggest ideas on formations, development and genesis of the ore deposits. One observes that the oxide fades is most important; the carbonate and sulfide facies are less so.

While a change over from siderite to hematite is normally traceable along the hill-cut road to Khandadhar Township (Figures 5.7-5.8), many other locations indicate that the carbonate facies extended much more than hitherto realized. In Daitari basin this is found at a few places like Ponga.

Thus, BIF shows a range of mineralogical variation inside the iron-oxide bands. In Daitari range banded chert-quartzite shows preferential replacement of saccharoidal quartzite by iron oxide. In banded hematite shale, often the hematite is partly later as traced on the slopes north of Tomka peak and further east.

Thus, the banding in BIF may also be considered to be partly non-sedimentary and is of replacement type; this however, cannot be fully quantified. It is possibly partly true but certainly does not occur as a regionally effective process but nevertheless, has its own importance in places below and above BIF.

With a smaller range of variation of Eh/pH and with a good potential of iron oxide in solution, a 30 m thick ore body has been found below Gandhamardan and elsewhere below BIF; this has slowly allowed coming in of silica that forms bands (≈ 1 cm) of Jasper/chert in contrast to very thick hematite bands.

If presumably they have been deposited in sub-basins (with almost fixed chemical parameters), shown by NNE and E-W faults, on the floor of the basin, continuously formed chemical deposits will be physically discontinuous during their reactivation although they will be in the same strike and have similar attitudinal parameters.

Field evidences indicate infra-BIF ore body gradually gives place to formations of BIF with thicker iron-oxide bands, which upward, give place to thicker silica bands. This interplay has resulted in sedimentary boudins of BIF (horses) in ore and vice-versa.

This finds beautiful expression of itself at Tomka, Champajhar Tungaisani, Kalisagar. In the eastern limb of the BIF-3 basin, iron ore, thus, has excellent grade, which are used for sponge iron due of its compactness because of direct sedimentation with least disturbance by syn -or post structural complications. Massive ore body with 69.2 per cent of iron has been found in Khondband (infra-) and also elsewhere.

It looks that the ore-body type that is an outcome possibly of a syn-sedimentary deformation with associated recommendation and enrichment. This ore body type is of excellent grade, sufficiently compact for any tough use (not much powder) although the sizes of ore boulders are not unduly large. Occurring usually at a few present- day hilltops, they are found below certain ore zones as well, as the exposures change down to other ore-types.

The differently sized flatfish fragments maintain a somewhat parallel nature of existence. They are regarded to be formed by basinal oscillation prior to their consolidation. The groundmass has a differently generated ore mineral and, thus, forms another younger stage of neo-mineralization.

It is known that metamorphism causes recrystallisation that is achieved by regrouping of elements in a different order befitting to the new chemical environment. The Daitari-Tomka Range deposits although underwent metamorphism (of higher grade of green schist/facies but rarely touching amphibolite-facies at depth. Acharya (1964) do not show significant change.

One observes that oxide facies in BIF sedimentation is most flourishing and most of the siderite material is hematitised. The sulfide facies, developed naturally at depth, is of little consequence in ore formation. So is the case with the silicate facies that shows banded grunerite-quartzite in BIF-1 basin extensively, but less so in Daitari basin. It is frequently observed in BIF-I at Gorumahisani and Badampahar west Mayurbhanj district and around Malyagiri.

A pocket of blue dust in BIF and ore bodies indicates in-situ leaching of flux-materials and consequential concentration of iron materials. Between Thakurani and Bolani hills sits Barbil on such a deposit, huge in nature but only at depth and partly mined. The degree of in-situ leaching is prominent.

Minerography Studies:

Studies have shown the role of diagenesis in ore-fluid migrations and readjustment to upgrade ore quality. Diagenesis has enriched the metal content and at times, the impurities as well (silica mostly) complicating the simple nature of primary ore mineralogy. Generations of minerals are introduced into the litho-system upgrading/downgrading the ore deposits and ore minerals in BIF as are the cases location- wise.

Any approach on genesis of ore deposits has to take care of source, transport medium (essentially hydrous), metal migration, deposition and later sequence of enrichment. PT conditions make the deposits mono- or multi-mineralic based on elemental distribution.

In case of iron ore, weathering and lateritization are also big parameters controlling ore body formation and evolution. In the diagrams (Figures 5.9 and 5.10) from the beginning of banding in BIF up to the formation of ore deposits have been shown with microscopic details.

These show how at different solution of ore flux into BIF/ore bodies and upgrade the ore both in quality and quantity and the role of diagenesis as a natural mineraling process at different parts of time specially when continuity of volcanism is evidenced in space and time up to the end of sedimentation.

Thus, it is clear that provenance of volcanism play the most important role/s in supplying the ore-material and sedimentation, followed by diagenesis, compaction, dehydroxidation, weathering and supergene enrichment (where weathering has been possible) have played dominant roles to bring in the deposits. Removal of silica and consequent loosening of ore -bands causes the biscuity ore to form and the dissolved iron oxide migrate bottomward to upgrade the protore bodies or is wasted.

It fixes the iron-oxide into the lower horizon, thus, reducing the volume and upgrading the iron oxide percentage, causing a double benefit. Certain degree of solution (by weathering) is continuously in progress at the top level to reduce the bulk there and to atleast partly refix the ore materials at depth.

The textural evolution of the associated minerals is quite evident. Although partly qualitative, this process of enriching ore deposits should be valid if in space and time these processes do not change and there is no evidence in its favour.

To add to it remanent magnetic studies of ores vis-a vis BIF go a long way to prove both syngenetic /epigenetic nature of the deposits with reference to the host rock. While the Daitari deposit is considered to be both syngenetic and epigenetic (poly-genetic), the ore bodies of JKB are genetically found to be similar but with mutually different time frames and more (in number of times) polygenetic than the former.

With better understanding of genesis in spite of not much of borehole data (bore holes hardly go beyond the bottom of ore bodies) a sequence stratigraphy has been attempted on a rather wide canvas that needs further fine- tuning continuously.

Ore microscopic combined with petrologic studies reveal growth pattern of iron- ore minerals as shown in Table 5.2.

From all these different approaches certain ideas on genesis could be developed which may be drawn up as follows:

Banded Hematite Shale (BHS) as sedimentary iron ore deposits. The ore bodies BIF in general holds BHJ, BHQ, Banded hematite Shale, as the sedimentary iron ore deposits. The ore bodies are stratiform and are infra-, intra- and supra- BIF in occurrence. Sedimentary boudinisation of ore body is to be kept in mind during mining; one can think of a chemical basin manifested this way physically.

The second fold system in JKB is most important in controlling the extension of ore bodies in space. The third one causes thickening and thinning and brings in a variable depth factor to search ore. The infra-BIF ores are low in silica and alumina while the supra- BIF ores outsource Al₂O₃ from upper shale. Crystalline manganese ore bodies are usually remobilized along fault planes and other weaker zones.

Manganese ore below lower shales does not occur. Wad (manganese-shale as mine waste) has 7 to 32 percent Mn and wad is an aggregation of different Mn-rich shale types whose petrochemistry suggests presence of certain important uncommon elements. Both iron and manganese have been outsourced into the Jamda-Koira basin from the provenance and also through exhalation.

The ore bodies are strongly stratiform and structurally controlled and these two features broadly control the shape and size of the deposits. Both biochemical and abiochemical processes have played their roles to precipitate the iron and also manganese minerals are due to processes of mechanical re-concentration at a much later stage. Many such reworked deposits were mined as ‘floats’ since iron ore mining started.

The iron and manganese deposits are essentially sedimentary but increase in size and grade with stages of diagenetic enrichment in time; this is further aided by re-concentration due to weathering as shown in Figure 5.11.