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EGU 2015-137
Mineralogical and Geochemical Characteristics
of the Noamundi-Koira Basin Iron Ore Deposits
(India)
AZIMUDDIN MIRZA1, S.H.ALVI2, NURDANE ILBEYLI1
1
Akdeniz University, Fac. of Eng., Dept. of Geol. Eng, Antalya-TURKEY
2 Aligarh Muslim University, Dept. of Geol., Aligarh-INDIA
Mineralogical and geochemical characteristics of the
Noamundi-Koira basin iron ore deposits (India)
1
AZIMUDDIN MIRZA1, S.H.ALVI2, NURDANE ILBEYLI1
Akdeniz University, Fac. of Eng., Dept. of Geol. Eng, Antalya-TURKEY
2 Aligarh Muslim University, Dept. of Geol., Aligarh-INDIA
INTRODUCTION
•
•
The Singhbhum craton is made up North and South
Singhbhum shear zones.
The latter shear zone starts with the basement of Old
metamorphic group, older metamorphic tonalite
trondhjemite gneisses, banded iron formation,
metasedimentary rocks and covered by metavolcanic
rocks of the North Singhbhum shear zone.
Fig 1: Simplified geological map of Singhbhum-Orissa Craton (after, Saha 1994)eastern India.
EGU 2015-137
Mineralogical and geochemical characteristics of the
Noamundi-Koira basin iron ore deposits (India)
1
AZIMUDDIN MIRZA1, S.H.ALVI2, NURDANE ILBEYLI1
Akdeniz University, Fac. of Eng., Dept. of Geol. Eng, Antalya-TURKEY
2 Aligarh Muslim University, Dept. of Geol., Aligarh-INDIA
EGU 2015-137
• The presence of disseminated martite in banded hematite jasper (BHJ) suggests that the
magnetite of protore was converted to martite.
• In first stage, unaltered banded iron formation (BIF) by simultaneously oxidizing
magnetite to martite and replacing quartz with hydrous iron oxides.
• In the second stage of supergene processes, deep burial upgrades the hydrous iron
oxides to microplaty hematite.
• Removal of silica from BIF and successive precipitation of iron resulted in the
formation of martite-goethite ore.
• Soft laminated ores were formed where leached out space remains with time and the
interstitial space is generally filled with kaolinite and gibbsite, which make it low grade.
Mineralogical and geochemical characteristics of the
Noamundi-Koira basin iron ore deposits (India)
1
AZIMUDDIN MIRZA1, S.H.ALVI2, NURDANE ILBEYLI1
Akdeniz University, Fac. of Eng., Dept. of Geol. Eng, Antalya-TURKEY
2 Aligarh Muslim University, Dept. of Geol., Aligarh-INDIA
EGU 2015-137
GEOCHEMISTRY
Plots of Fe2O3 (%) vs.
Al2O3
Plots Fe2O3 (%) vs. SiO2
60
80
60
0.3
0.2
CaO
SiO2
Al2O3
40
40
0.1
20
20
Plots of Fe2O3 (%) vs.
MgO
0.2
0
0
Fig.1(d)
100
Fe2O3
200
0
Fig.1 (b)
1.2
1
0.8
0.6
0.4
0.2
0
6
1.5
100
Fe2O3
50
Fe2O3
100
150
0
50
Fig.1 (g)
100
Fe2O3
150
0
Fig.1(f)
Plots of Fe2O3 (%) vs.
TiO2
TiO2
K2O
0
100
Fe2O3
150
0
2
0.5
50
Plots of Fe2O3 (%) vs.
Na2O
1
4
1
0
Fig.1(c)
150
0.5
0
(e)
Plots Fe2O3 (%) vs. K2O
50
Na2O
150
6
MnO2
MgO
0.4
50
100
Fe2O3
P2O5
0
Fig.1(a)
2
0
0
0
Plots of Fe2O3 (%) vs.
CaO
0
0
Fig.1 (h)
100
200
Fe2O3
50
100
Fe2O3
150
Plots of Fe2O3 (%) vs.
MnO2
4
2
0
0
Fig.1(i)
50
Fe100
2O3
150
Mineralogical and geochemical characteristics of the
Noamundi-Koira basin iron ore deposits (India)
1
AZIMUDDIN MIRZA1, S.H.ALVI2, NURDANE ILBEYLI1
Akdeniz University, Fac. of Eng., Dept. of Geol. Eng, Antalya-TURKEY
2 Aligarh Muslim University, Dept. of Geol., Aligarh-INDIA
Relationship Between CIA With Other Shale Oxides
Plot CIA Vs P2O5
Plot CIA Vs Mgo
0.12
0.1
0.06
P2O5
Mgo
0.08
0.04
0.02
0
85
90
Fig .2 (a)
95
100
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
0
CIA
100
150
Fe2O3
100
Plot CIA Vs TiO2
6
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
5
4
TiO2
k2O
Na2O
Fig .2 (c)
95
95
100
CIA
Plot CIA Vs Na2O
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
90
90
Fig .2 (b)
PLOT CIA Vs k2O
85
50
Fig.1 (j)
85
CIA
Plot of Fe2O3 (%) vs LOI
14
12
10
8
6
4
2
0
LOI
• The chemical index of alteration (CIA) depends on the ratio
of Al2O3 to CaO, Na2O and MgO.
EGU 2015-137
3
2
1
0
85
Fig .2 (e)
90
95
CIA
100
85
Fig .2 (d)
90
95
100
CIA
Mineralogical and geochemical characteristics of the
Noamundi-Koira basin iron ore deposits (India)
1
AZIMUDDIN MIRZA1, S.H.ALVI2, NURDANE ILBEYLI1
Akdeniz University, Fac. of Eng., Dept. of Geol. Eng, Antalya-TURKEY
2 Aligarh Muslim University, Dept. of Geol., Aligarh-INDIA
CONCLUSION
• Shows that
precipitates.
they
are
detritus-
EGU 2015-137
10
free
chemical
• Hard laminated ores, martite-goethite ore and soft
laminated ore are resultant of desilicification process
through the action of hydrothermal fluids.
Passive Margin
1
Active Continental
Margin
0.1
• Mineralogy study suggests that magnetite was the
principal iron oxide mineral, now a relict phase whose
depositional history is preserved in BHJ, where it
remain in the form of martite. The platy hematite is
mainly the product of martite.
• The presence of martite in massive ore along with
their gradational contact of with BHJ suggests its
syngenetic origin with BHJ.
Island Arc
0.01
0
10
20
30
40
50
60
70
80
90
100
Fig:4.1. SiO2 vs. Log K2O/Na2O discrimination diagram(after Roser and Korsch, 1986)
showing all the studied Iron samples plot in the Island Arc Field.
Screen PICO2.1.
SUMMARY
•
In this study the banded iron formation and associated iron ores of Noamundi–Koira iron
ore deposits (Singhbhum- Orissa craton) that points out the study of different iron ores
along with the composition of major elements and geological characteristics.
•
The Singhbhum craton is made up North and South Singhbhum shear zones. The latter
shear zone starts with the basement of Old metamorphic group, older metamorphic
tonalite trondhjemite gneisses, banded iron formation, metasedimentary rocks and
covered by metavolcanic rocks of the North Singhbhum shear zone.
•
The iron ore of Noamundi-Koira can be divided into seven categories (Van Schalkwyk
and Beukes 1986). They are massive, hard laminated, soft laminated, martite-goethite,
powdery blue dust and lateritic ore.
•
It is more or less accepted that the parent rock of iron ore is banded hematite jasper
(BHJ), the presence of disseminated martite in BHJ suggests that the magnetite of protore
was converted to martite.
•
In the first stage, shallow, meteoric fluids affect primary, unaltered banded iron formation
(BIF) by simultaneously oxidizing magnetite to martite and replacing quartz with hydrous
iron oxides.
•
In the second stage of supergene processes, deep burial upgrades the hydrous iron
oxides to microplaty hematite.
•
Removal of silica from BIF and successive precipitation of iron resulted in the
formation of martite-goethite ore. Soft laminated ores were formed where
precipitation of iron was partial or absent. The leached out space remains with time
and the interstitial space is generally filled with kaolinite and gibbsite, which make it
low grade.
•
Massive iron ores are devoid of any lamination and usually associated with BHJ and
lower shale. The thickness of the massive ore layer varies with the location. The
massive iron ore grades in to well-developed bedded BHJ in depth.
•
Blue dust occurs in association with BHJ as pockets and layers. Percolating water
play an important role in the formation of blue dust and the subterranean solution
offers the necessary acidic environment for leaching of quartz from the BHJ.
•
The dissolution of silica and other alkalis are responsible for the formation of blue
dust. The friable and powdery ore on the other hand are formed by soft laminated ore.
As it is formed from the soft laminated ore, its alumina content remains high similar
to soft laminated ore compaired to blue dust.
•
Hard laminated ores, martite-goethite ore and soft laminated ore are resultant of
desilicification process through the action of hydrothermal fluids.
•
The mineralogical and geochemical data suggest that the hard laminated, massive,
soft laminated ores and blue dust had a genetic lineage from BIF’s aided with certain
input from hydrothermal activity.
•
Geochemical data indicate that BIF are in general detritus free chemical precipitates.
Fe2O3 content of BHJ are varies in between 36.6% to 65.04%.
•
In hard laminated ore, Fe2O3 content varies from 93.8% to 96.38%, soft laminated ore
varies from 83.64% to 89.5% and laterite ore varies from 53.5% to 79.11%.
•
Fe2O3 content in Martite-Goethite ore varies from 86.38% to 89.42% and blue dust
having 90.74% to 95.86% and all other oxides like SiO2, Al2O3, CaO, MgO, K2O,
Na2O decrease.
•
Major part of the iron could have been added to the bottom sea water by
hydrothermal solutions derived from hydrothermally active anoxic marine
environments.
•
The presence of intracalated tuffaceous shales pointing towards the genesis of iron,
which could have leached from sea floor by volcanogenic process. Iron and silica of
BIF were provided by the hydrothermal solutions emplaced at the vent sites situated
at the Archean–Mid Oceanic Ridges.
Banded Iron Formation
•
Banded iron formations (BIFs) are a distinctive type of rock often found in primordial
(Precambrian) sedimentary rocks.
•
The structures consist of repeated thin layers of iron oxides, either magnetite (Fe 3O4) or
hematite (Fe2O3), alternating with bands of iron-poor shale and chert.
•
The formations are abundant around the time of the Great oxygenation event, 2400
million years ago (mya), and become less common after 1800 mya.
•
The total amount of oxygen locked up in the banded iron beds is estimated to be perhaps
twenty times the volume of oxygen present in the modern atmosphere.
•
Banded iron beds are an important commercial source of iron ore, such as the
Noamundi–Koira Basin of the Singhbhum Craton.
•
Younger rocks superficially representing BIFs, commonly termed ‘ironstones’, are
distinctly more Al2O3-, P2O5- and Fe2O3-rich and usually have an oolitic or pisolitic
texture (Schopf, 1983).
Table 1. Comparison of typical ironstones with iron formations (after James, 1966)
Characteristics
Ironstones
Iron Formations
Minimum age
Major development
Maximum age
Thickness of major units
Original areal extent, max. dimension
Pliocene
Lower Palaeozoic; Jurassic
Palaeo-Proterozoic (~2.0 Ga)
1-50 m
< 150 km
Late Precambrian
2.5-3.0 Ga
3760 ± 70 Ma
50-600 m
> 100 km
Physical character
massive to poorly banded; silicate thinly bedded; layers of haematite,
and oxide- facies oolitic
magnetite, siderite, or silicate
alternating with chert; chert ~50%
Age
Mineralogy
goethite
haematite
magnetite
chamosite
glauconite
dominant
fairly common
relatively rare
dominant primary silicate
Minor
none
common
common
absent
absent
siderite
common
common
calcite
common
rare
Mineralogy
dolomite
common
fairly common
pelletal collophane
relatively abundant
absent
greenalite
None
dominant primary silicate
quartz (chert)
Rare
major constituent
pyrite
common
common
Chemistry
high iron lower P
low Al, Na, K and minor elements;
much lower P
Genesis of banded iron formation
•
The interpretation of an active continental margin as the depositional environment of the
Minas Supergroup in Brazil, with the results that the same environment could explain the
origin of the Caue Itabirite, a well known iron-formation.
•
In active margins, during the powerful process of subduction, the ocean lithosphere is cut
by faults and fractures through which seawater gains access and hydrothermally leaches
the brittle yet hot lower layers.
•
Currently being studied near mid-ocean ridges when iron and silica, among other
compounds, are driven by thermal convection to the sea floor.
•
In Early Precambrian time, both hydrosphere and atmosphere were anoxic: ferrous iron
was soluble in seawater and the earth's surrounding ozone layer had not yet been formed.
•
A plume of FeO-SiO2-rich seawater was concentrated above and along the trench,
covering the nearby cratonic border. During the sunny hours of the day, iron was oxidized
into ferric hydroxide before precipitation.
•
Most banded iron-formations laid down in early Precambrian time were subducted with
their ocean plates and the only fraction preserved was that deposited above cratonic
borders.
•
The break in iron-formation deposition at the end of that era was due to seawater and
atmosphere oxygenation which produced the ozone-filtering layer around the earth and
also caused extinction of marine anaerobic microorganisms.
•
Banded iron-formations deposited in active or passive continental margins may assist in
the interpretation of the palaeo-environment of the regions where they occur.
•
The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow,
deep purple, to rusty red. The iron itself is usually found in the form of magnetite
(Fe3O4), hematite (Fe2O3), goethite (FeO(OH)), limonite (FeO(OH).n(H2O)) or siderite
(FeCO3).
•
It occurs as hematite (Fe2O3) or as goethite (HFeO2) or limonite (Fe2(OH)3) or siderite
(FeCO3). Pyrite (FeS) is mined more for the sulfur content rather than for iron.
STRATIGRAPHY AND GENERAL
GEOLOGICAL SETTING
•
The Singhbhum-Orissa craton forms a triangular crustal block between latitudes 21°0'
and 23°15' N and longitudes 84°40' and 86°45' E of a surface area ~40,000 sq. km (Saha,
1994).
•
This crustal block is broadly bounded by Chotanagpur Gneissic Complex to the north,
Eastern Ghat Granulite Belt and the Bastar craton to the south and west respectively.
•
The craton consists mainly of granitoids, ranging in composition from tonalite in the
oldest to alkali feldspar granite in the youngest, with engulfed and overlying
metasedimentary and metavolcanic rocks.
•
The central part of the craton is occupied by granitoids of relatively older ages, whereas
the metasediments, basic volcanics and younger granites occur at the margins mainly
along the north, west and east.
•
The basement of the Singhbhum metasedimentary rocks can be traced in a broadly elliptical
pattern of granitoids, with patches of Tonalite-Trondhjemite Granitoids (TTG) rock
assembly, surrounded by metasediments and metavolcanics of Greenstone Belt association.
•
Most of the intrusive rock area is occupied by the Singhbhum granitoid, dated at 3.1 Ga,
(Saha, 1994) and crosscut in rectangular pattern by voluminous Neoarchaean mafic and
ultramafic dike swarms (Roy et al., 2004).
•
An ancient core to the Singhbhum rocks is built by the relatively small remnant of the Older
Metamorphic Group (OMG) and Older Metamorphic Tonalite Gneiss (OMTG) rocks, dated
between 3.4 and 3.5 Ga and metamorphosed to amhibolite facies (Saha et al., 1994;
Sharma, 1994).
•
The Palaeoproterozoic Dhanjori Formation overlies the Singhbhum granitoid and is in turn
overlain by the Chaibasa and Dhalbhum Formations constituting the Singhbhum Group
(Mazumder, 2005).
•
Dhalbhum Formation includes 2 to 4 km thick quartzites, schists and tuffs of an unknown
age and the following Dalma Formation with thick lava and volcano clastic rocks was dated
at a minimum of 1600 Ma.
Fig 1: Simplified geological map of Singhbhum-Orissa Craton (after, Saha 1994) eastern India.
Fig. 2.A simplified geological map of Singhbhum-Orissa craton showing different lithounits (after Saha, 1994, Mukhopadhyay et al. 1990) and their
modified ages of formation as understood from recent studies .Some modification on distribution of SBG-I in the map is made following new
findings of Ghosh et al. (1996). The expected ages of formation of the supracrustals and some other lithounits (which are not dated directly) are
marked by star (*). Abbreviations of lithounit names in alphabetical order: AG- Arkasani Granite, BG- Bonai Granite, CG- Chakradharpur Granite
Gneiss, CGC- Chotanagpur Gneissic Complex, DLV- Dalma Volcanics, DNV- Dhanjori Volcanics, GOND- Gondwana and equivalent sediments,
IOG- Iron Ore Group, JPV- Jagannathpur Volcanics, KG- Kuilapal Granite Gneiss, MBG- Mayurbhanj Granite, MG- Mayurbhanj Gabbro, MTVMalangtoli Volcanics, NG- Nilgiri Granite, OMG- Older Metamorphic Group, OMTG- Older Metamorphic Tonalite Gneiss, SBG-I -Singhbhum
Granite (phase I), SBG-II–Singhbhum Granite (Phase II), SBG-III –Singhbhum Granite (Phase III), SG- Soda Granite, SMB- Singhbhum Mobile
Belt, SPLV- Simlipal volcano-sedimentary basin, UGG- Unclassified granite/ granulites. Solid ellipses- sample locations of Misra et al. (1999), solid
pentagons- sample locations of Roy et al. (2000 a,b). FF- eastern extension of Singhbhum Shear Zone passing through Kendua.
•
Laterally extensive semi-circular Singhbhum Shear Zone (SSZ) which encompasses
mainly Dhanjori quartzites and schists and can be followed for some 200 km along
strike and for few km in width.
•
The thrusting, folding and metamorphism are generally thought to thoroughly
obliterate stratigraphic and sedimentary facies relationships.
•
The degree of metamorphism decreases markedly towards the top of the section and
is much lower in the Dalma and Chandil Formations, probably reaching lower
greenschist facies at the top.
•
The timing of one of the metamorphic events is around 1600 Ma, as is the age of
the shearing/ thrusting along the Singhbhum Shear Zone (Krishna Rao et al., 1977;
Sengupta and Mukhopadhaya, 2000).
Generalized Stratigraphy of Singhbhum Craton
South of Singhbhum Shear Zone
North of Singhbhum Shear Zone
Kolhan Group
Newer Dolerite Dykes (Phase-III)
Newer
Dolerite
Dykes
(Phase-III)
Dalma Metavolcanic Suite
Jagannathpur/Dhanjori/Ongarbio Volcanic Suite and Newer Dolerite Dykes (Phase-II)
newer Dolerite Dykes (Phase-II)
Dhanjori/Sahedba Metasedimentary Rocks
Gabbro-anorthosite
and
associated
Dolerite
Gabbro-anorthosite
Dykes (Phase-I)
Noamundi-Koira
Banded
Iron
Formation
and Dhalbhum Formation
associated Manganese Deposits
Chakradharpur Granite-Gneiss
Bonai Metavolcanic Suite/Simlipal Complex
complex/Soda Granite/Arkasani
Granophyre
Chaibasa Formation
Chaibasa Formation
Singhbhum Granite Complex/Bonai Granite
Gorumahisani-Badampahar Banded Iron
Formation
Older
Metamorphic
Tonalite-Trondhjemite
(TTG)
Gneisses (OMTG)
Older Metamorphic Group (OMG)
Basement(?)
Basement(?)
Noamundi-Koira Basin
•
The BIF in Noamundi-Koira Basin (NKB) trends N-NE and is low plunging
synclinorium with an overturned western limb (Chakraborty and Majumdar, 1986).
•
The clear separation of Iron and manganese into discrete ore bodies in NKB suggest the
dawn of an oxidizing atmosphere near the close of Bonai volcanism.
•
A lower volcanogenic facies devoid of either iron or manganese deposits is represented
by tuff, tuffaceous shale (phyllite) and referred as Lower Shale. This occurs peripheral to
the basin and is poorly exposed in the eastern part of the basin, where its thickness does
not exceed 30 to 50 m (Banerjee, 1975).
•
The overlying transitional chemogenic facies is made up of 300 to 400 m thick Banded
Hematite Jasper (BHJ).
•
The upper facies is represented by manganiferous shale, chert, dolomite and tuff, referred
as Upper Shale in the forms of layers and isolated lenses, few associated with chert and
few with dolomite beds (Murthy and Ghosh, 1971).
•
The shale is usually soft showing distinct lamination of varying thickness and wide range
of colours-grey, pink, brown and yellowish white.
•
The colour band in the shale varies from few millimeters to several centimeters. The
upper shale is distinct from typical Archean, Proterozoic and Phanerozoic shales,
which commonly contain considerable amount of chlorite.
•
The Upper shale comprises kaolinite as a major phase with minor with minor quartz,
plagioclase and calcite.
•
Sambasiva Rao and Das Gupta (1997) found that the majority of the sample contain
only kaolinite and a small proportion of sample comprise both kaolinite and illite.
Hematite, goethite, mangnetite and very rarely ilmenite from the characteristic heavy
mineral assemblage.
GEOCHEMISTRY
•
Geochemical data indicate that BIF are in general detritus free chemical precipitates.
Fe2O3 content of BHJ are varies in between 36.6% to 65.04%.
•
In hard laminated ore, Fe2O3 content varies from 93.8% to 96.38%, Soft laminated ore
varies from 83.64% to 89.5% and laterite ore varies from 53.5% to79.11%.
•
Fe2O3 content in martite-goethite ore varies from 86.38% to 89.42% and blue dust having
90.74% to 95.86% and all other oxides like SiO2, Al2O3, CaO, MgO, K2O, Na2O are
decreases.
•
Major element analysis reveals that the BHJ can contains very little amount of Al 2O3,
TiO2, MgO, MnO2, and CaO. In BHJ with least alteration, the Fe is around 40% and the
total Fe2O3 in the BHJ of Noamundi- Koira basin from 40.75% to 65.04%.
•
Fe2O3 (20% to 98%) and SiO2 (0.1% to 60%.) content of the studied BIF shows that
variation from different localities show clear grouping and mainly discriminate between
the groups on the basis of Fe2O3 and SiO2 content.
•
In the plot of Fe2O3 vs SiO2, Samples show negative trend indicating increase of Fe2O3
with decrease in SiO2.
•
The TiO2 concentration ranges between 0.035% and 0.062% in the BHJ and from 0.04%
to 0.74% on an average in the iron ores.
•
The BHJ of Noamundi- Koira deposits are pure chemical precipitates and hence have
low Al2O3 and TiO2. Both simultaneously increase in laterite and shale represent a time
of increased detrital input.
•
BHJ and high grade ore are depleted in CaO+MgO, suggesting a near absence of calcite
and dolomite which is also clear from the mineralogical information. TiO 2 shows a
positive correlation with Al2O3 in ores.
•
Aluminum and Titanium are considered to be immobile during hydrothermal, diagenetic
and weathering processes . Alkali content (K2O + Na2O) of shales, lateritic ore and BIF
shows considerable variation. Shale samples contain high Na2O, but low K2O content
indicating that the source of the clastic component was of variable composition.
•
The lower shale member contains more silica and higher percentage of silica is due to
presence of quartz, the middle shale member is enriched in Fe2O3 as it is interbedded
with iron ores.
•
The upper shale member shows almost similar Al2O3 content with middle shale member
but lower Fe2O3.The shale samples are enriched in Na2O and K2O and the samples with
high K2O reflect the micaceous nature of some of the terrigenous layers.
•
The lower shale of Noamundi-Koira area contain 0.84% of Na2O and 0.97% of K2O
suggesting their origin from volcanoclastic debris.
•
The average oxide percentage values of various shale members fall in three different fields
closely associated with tuffaceous volcanic/pyroclastics indicating a close relation between
the lower shale and volcanic tuff / pyroclastic rocks.
Plots of Fe2O3 (%) vs. Al2O3
40
CaO
30
20
10
0
0
Fig.1(a)
50
100
150
Fe2O3
0
Fig.1 (b)
Plots of Fe2O3 (%) vs. MgO
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
50
100
150
1.2
1
1
0.8
Na2O
P2O5
MgO
Fig.1(d)
Fe2O3
150
0.4
0.2
0.2
0
0
0
Fig.1(e)
100
0.6
0.4
200
50
Fe2O3
Plots of Fe2O3 (%) vs.
Na2O
Plots of Fe2O3 (%) vs. P2O5
0.6
100
0
Fig.1(c)
Fe2O3
0.8
0
Plots of Fe2O3 (%) vs. CaO
0.3
0.25
0.2
0.15
0.1
0.05
0
50
70
60
50
40
30
20
10
0
Al2O3
SiO2
Plots Fe2O3 (%) vs. SiO2
50
100
Fe2O3
150
0
Fig.1(f)
50
100
Fe2O3
150
Plots of Fe2O3 (%) vs. TiO2
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
6
5
TiO2
K2O
Plots Fe2O3 (%) vs. K2O
4
3
2
1
0
50
Fig.1 (g)
100
0
150
0
Fe2O3
50
Fig.1 (h)
100
150
Fe2O3
Plots of Fe2O3 (%) vs. MnO2
Plot of Fe2O3 (%) vs LOI
6
5
4
3
2
1
0
LOI
MnO2
14
12
10
8
6
4
2
0
0
Fig.1(i)
0
Fig.1 (j)
50
100
50
100
Fe2O3
150
150
Fe2O3
FIg3.(k to t) Shows binary diagram Fe2O3 Vs SiO2, Al2O3, CaO, MgO, P2O5, Na2O, K2O, TiO2, MnO2, LOI. Fe2O3 is
taken as the reference oxide.
Relationship Between CIA With Other Shale Oxides
Plot CIA Vs Mgo
•
The chemical index of alteration (CIA) depends on
the ratio of Al2O3 to CaO, Na2O and MgO.
0.12
0.1
•
If the values of CIA lie in between 50% to 60% then
weathering is low, varies from 60% to 75% rock is
moderately weathered and if they lie from 75% to
90% then rock is highly weathered.
Mgo
0.08
0.06
0.04
0.02
0
85
•
In the plot of CIA vs MgO shows increase
percentage of CIA with decrease concentration of
MgO. From the data it is observed that Mg+2 ions is
easily mobilized during weathering. From binary
diagram, the values of MgO declines (0.11% to
0.03%)
90
Fig .2 (a)
95
100
CIA
Plot CIA Vs P2O5
0.14
0.12
•
In the plot of CIA vs P2O5 shows a positive trend
indicating that the increase in percentage of CIA
with increase concentration of P2O5 are not easily
mobilized because of its HFSE behavior.
P2O5
0.1
0.08
0.06
0.04
0.02
0
85
Fig .2 (b)
90
95
CIA
100
•
k2O
PLOT CIA Vs k2O
In the plot of CIA vs TiO2, it shows a positive trend
indicating that increase of percentage of CIA with
increase of TiO2 concentration.
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
85
90
Fig .2 (c)
95
100
95
100
CIA
Because Titanium ions are immobilized during
weathering. It remains in the rock even when the rock
is completely weathered.
Plot CIA Vs Na2O
Plot CIA Vs TiO2
6
5
4
Na2O
•
In the plots of CIA vs K2O and Na2O. Both shows a
negative trend indicating that increase of weathering
with decrease of K2O and Na2O concentrations. The K+
and Na+ ions are easily dissolved and mobilized during
excessive weathering. The values of K2O declines 1.7%
to 0.1% and Na2O from 1% to 0.3%.
TiO2
•
3
2
1
0
85
Fig .2 (d)
90
95
CIA
100
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
85
Fig .2 (e)
90
CIA
Depositional Environment
10
•
In order to distinguish the tectonic
setting of the depositional site of the
Upper shale K2O/Na2O vs. SiO2
discrimination diagram (Roser and
Korsch, 1986) is used.
•
All the samples having low silica
concentration and K2O/Na2O ratio
falls in the field of island arc and
continental margin setting.
•
Calc-alkaline affinity of Bonai
volcanic suite (Banerjee, 1982),
Bonai Granite (Sen Gupta et al.,
1991) and volcanic arc affinity of the
Singhbhum Granite which forms the
basement and/or intrudes the BIF
(Saha, 1994) also support this
observation.
Passive Margin
1
Active Continental
Margin
0.1
Island Arc
0.01
0
10
20
30
40
50
60
70
80
90
100
Fig:4.1. SiO2 vs. Log K2O/Na2O discrimination diagram(after Roser and Korsch, 1986)
showing all the studied Iron samples plot in the Island Arc Field.
•
Alumina is positively correlated with SiO2, K2O, Na2O and MgO, which suggests the major
composition of volcaniclastics to be potassium aluminum silicates, and/or sodium
aluminum silicates and/or magnesium aluminum silicates.
•
Alumina also shows a strong positive correlation with titanium in both tuffaceous shale
(associated country rock) and in situ Mn ores, indicating their contribution through the
volcaniclastics/terrigenous detritus.
•
Al2O3 is positively correlated with SiO2, Na2O and Mgo and TiO2 like that of associated
manganiferrous shale and hence considered as primary depositional.
•
Partition of minor and trace elements between the Mn oxides and Fe oxides probably took
place during diagenesis of the oxides rather than during their deposition.
•
Preferential enrichment of traces like Li, Co, Ni, Cu, Zn and Pb in Mn oxides during
diagenesis is because of diavalent, trivalent, and tetravalent valence state of Mn.
•
The smaller ionic radius of trivalent Fe and the lesser tendency of Fe to form minerals other
than its simple hydroxide and oxides in oxidizing sedimentary and diagenetic environments
may explain the lower concentration of many trace elements.
•
Positive correlations between Mn oxide and Li, Co, Ni, Cu, Zn and Pb and between Fe
oxide and Y suggest that trace elements get dissolved during leaching, remobilized and
co-precipitated with Mn hydroxides/Fe hydroxides, respectively.
•
During the process of oxidation and recrystallization, many of the trace elements get
expelled from the Mn+4 structure.
•
Some elements (Ba, Cu, and Zn) desorbed from Fe–hydroxide get into solution and are
re-deposited with Mn, As, V and P2O5 showing positive relation with Fe in the insitu
ores did not show any significant relationship in remobilized ores, indicating thereby
their resistance to dissolution.
DISCUSSION
•
High grade BIF –hosted deposits are the world’s most important source of iron ore.
•
The loss of silica and redistribution of iron is the result of strong sub-tropical
weathering (Cope et al 2008).Hard ores rich in hematite and martite in most of the
Indian deposits are believed to have formed during early hydrothermal events
(Mukhopadhyay et al. 2008).
•
Chemical weathering in wet tropical humid-monsoonal climate resulted in extensive
supergene modification of these hydrothermally upgraded iron ores to hematite-martite
ore (Beukes et al 2008).
•
Hard hematite-martite ores in Noamundi region was found by hydrothermal
replacement of BIF protolith through leaching of silica and introduction of iron by
hydrothermal fluids of meteoric origin (Beukes et al. 2008).
•
The iron ore of Noamundi–Koira can be divided into seven categories. They are
massive, hard laminated, soft laminated, martite-goethite, powdery blue dust and
lateritic ore.
•
Although it is more or less accepted that the parent rock of iron ore is BHJ, the
presence of disseminated martite in BHJ suggests that the magnetite of protore was
converted to martite.
•
In the first stage, shallow, meteoric fluids affect primary, unaltered BIF by
simultaneously oxidizing magnetite to martite and replacing quartz with hydrous iron
oxides.
•
In the second stage of supergene processes, deep burial upgrades the hydrous iron
oxides to microplaty hematite. Small and large scale faults and folds similar to those
in BIF are also common in the hard laminated ore body.
•
The porosity of hematite lamina is presented as evidence of leaching of primary silica
by alkaline fluids. Which subsequently precipitated ferric hydroxide as a precursor to
goethite and eventually hematite (Van Schalkwyk and Beukes 1986).
•
Removal of silica from BIF and successive precipitation of iron resulted in the
formation of martite-goethite ore. Soft laminated ores were formed where
precipitation of iron was partial or absent. The leached out space remains with time
and the interstitial space is generally filled with kaolinite and gibbsite, which make it
low grade.
•
Massive iron ore are devoid of any lamination and usually associated with BHJ and
lower shale. The thickness of the massive ore layer varies with the location. The
massive iron ore grades in to well-developed bedded BHJ in depth.
•
Blue dust occurs in association with BHJ as pockets and layers. Although blue dust and
friable ore are both powdery ores, and subjected to variable degree of deformation,
leading to the formation of folding, faulting and joints of complex nature produce
favourable channels.
•
Percolating water play an important role in the formation of blue dust and the
subterranean solution offers the necessary acidic environment for leaching of quartz
from the BHJ.
•
The dissolution of silica and other alkalis are responsible for the formation of blue dust.
The friable and powdery ore on the other hand are formed by soft laminated ore. As it
is formed from the soft laminated ore, its alumina content remains high similar to soft
laminated ore compared to blue dust.
CONCLUSION
•
From the above discussion it is concluded that, Geochemistry of banded iron
formations of the Noamundi-Koira iron ore deposits belongs to Singhbhum-North
Orissa Craton Shows that they are detritus- free chemical precipitates.
•
Presence of intercalated tuffaceous shales point towards genesis of the iron, which
could have leached from sea floor by volcanogenic process. Iron and silica of the BIF
were provided by the hydrothermal solutions emplaced at the vent sites situated at the
Archean Mid-Oceanic Ridges.
•
Due to thermal and chemical potential variation and upwelling, the iron and silica
rich water was transported to the sites of deposition at the shallow shelf.
•
Increased hydrothermal flux, and higher exit temperature appear responsible for
bringing such large quantities of iron and silica into the oceans of Archean
Singhbhum-Orissa basins.
•
Mineralogy study suggests that magnetite was the principal iron oxide mineral, now a
relict phase whose depositional history is preserved in BHJ, where it remain in the
form of martite. The platy hematite is mainly the product of martite.
•
The different types of iron ores are intricately related with the BHJ. Hard laminated
ores, martite-goethite ore and soft laminated ore are resultant of desilicification
process through the action of hydrothermal fluids.
•
Removal of silica from BIF and successive precipitation of iron by hydrothermal
fluids of meteoric origin in the formation of martite-goethtite ore.
•
The hard laminated ore has been formed in the second steps of supergene processes,
where the deep burial upgrades the hydrous iron oxides to hematite.
•
Soft laminated ores and biscuity ore were formed where precipitation of iron was
partial or absent In this case, the leached out space remains with time and the ore
becomes very fragile in between the laminae.
•
Blue dust has been formed owing to circulating waters, which leached away the silica
from protore. The presence of martite in massive ore along with their gradational
contact of with BHJ suggests its syngenetic origin with BHJ.
Table 2: Shows major element constituents of Banded heamatite jasper in Noamundi
–Koira iron basin ore deposits of Singhbhum Orissa Craton.
Sample
Fe2O3
BHJ1
BHJ3
BHJ5
BHJ7
BHJ9
BHJ11
BHJ13
BHJ15
59.5
36.6
49.3
45.75
51.1
51.2
61.5
65.04
47.04
50.49
45.12
45.35
34.52
29.86
35.54
58.2
1.5
1.5
1.5
1.2
2
2.4
2.7
2.5
CaO
0.09
0.16
0.13
0.09
0.19
0.26
0.08
0.2
MgO
0.06
0.09
0.32
0.12
0.16
0.21
0.19
0.19
P2O5
0.0511
0.0549
0.0525
0.045
0.0592
0.0412
0.0323
0.0518
Na2O
0.15
0.13
0.14
0.13
0.15
0.15
0.15
0.15
K2O
0.13
0.06
0.14
0.13
0.07
0.08
0.05
0.08
Total S
0.04
0.04
0.04
0.04
0.04
0.04
0.04
0.04
TiO2
0.058
0.061
0.05
0.035
0.046
0.045
0.061
0.056
MnO2
0.171
0.11
0.154
0.085
0.065
0.055
0.198
0.085
LOI
1.41
1.56
1.25
1.42
1.2
1.82
1.46
1.85
Total
100
100.01
100
100
100
100
100
100
SiO2
Al2O3
Sample
Fe2O3
BHJ17
BHJ19
HLO1
HLO3
HLO5
HLO7
SLO1
SLO3
41.4
41.15
95
95.1
96.38
95
89.5
83.64
55.37
53.93
1.53
1.62
0.67
1.65
5.8
7.1
0.7
2.3
1.33
1.4
0.3
1.5
1.8
4.7
CaO
0.19
0.09
0.05
0.05
0.02
0.09
0.11
0.15
MgO
0.23
0.13
0.06
0.09
0.2
0.2
0.06
0.09
P2O5
0.0425
0.0549
0.046
0.022
0.046
0.023
0.046
0.055
Na2O
0.17
0.17
0.0412
0.042
0.0356
0.0462
0.042
0.05
K2O
0.12
0.13
0.078
0.065
0.044
0.052
0.051
0.076
Total S
0.04
0.04
0.042
0.043
0.042
0.043
0.043
0.043
0.056
0.062
0.041
0.042
0.042
0.046
0.047
0.072
SiO2
Al2O3
TiO2
MnO2
0.095
0.028
0.187
0.055
0.055
0.055
0.055
0.055
LOI
1.59
1.92
1.56
1.47
2.17
1.27
2.45
3.97
Total
100
100
99.97
100
100
99.98
100
100
Shows various oxides with iron ore deposits like soft laminated ore, laterite ore, martite- goethite ore,
hard laminated ore ,blue dust and different layered shale in Noamundi –Koira basin of iron ore deposits of
Singhbhum Orissa Craton.
Sample
Fe2O3
SLO5
LO1
LO3
LO5
LO7
85.9
55.5
79.11
70.81
SiO2
5.3
18.02
6.42
11.52
Al2O3
4.2
14.89
5.32
CaO
0.06
0.13
MgO
0.07
P2O5
MGO1
MGO5
88.54
87.72
86.38
19.11
4.32
4.36
5.34
9.52
16.57
3.24
3.5
4.65
0.05
0.06
0.08
0.11
0.11
0.098
0.07
0.2
0.07
0.12
0.087
0.093
0.098
0.046
0.096
0.062
0.066
0.969
0.057
0.056
0.065
Na2O
0.054
0.12
0.13
0.143
0.098
0.043
0.053
0.059
K2O
0.068
0.129
0.12
0.072
0.15
0.053
0.056
0.067
Total S
0.043
0.074
0.044
0.061
0.065
0.041
0.043
0.044
TiO2
0.059
0.86
0.625
0.612
0.852
0.043
0.045
0.053
MnO2
0.055
0.211
0.11
0.084
0.211
0.167
0.198
0.128
4.1
9.8
7.8
6.97
8.2
3.23
3.7
3
99.97
99.9
99.99
99.99
99.93
99.93
99.93
99.98
LOI
Total
53.5
MGO3
Sample
Fe2O3
BD1
BD3
BD5
US1
US3
US5
MS1
MS3
94.55
95.86
91.36
18.7
18.83
15.95
50.25
54.12
SiO2
1.89
1.75
4.18
20.69
22.93
28.93
16.7
12.46
Al2O3
1.23
0.55
2.14
33.02
29.84
38.12
23.18
21.89
CaO
0.02
0.02
0.02
0.178
0.19
0.167
0.013
0.012
MgO
0.2
0.2
0.2
0.041
0.031
0.036
0.052
0.065
P2O5
0.046
0.046
0.046
0.073
0.08
0.117
0.055
0.057
Na2O
0.054
0.042
0.061
0.343
0.355
0.321
0.529
0.437
K2O
0.065
0.076
0.068
0.246
0.204
0.284
0.02
0.13
Total S
0.038
0.041
0.044
0.043
0.085
0.04
0.04
0.04
TiO2
0.051
0.045
0.058
3.68
5.58
3.31
0.59
0.72
MnO2
0.045
0.045
0.045
5.015
4.047
0.935
0.056
0.057
1.8
1.3
1.7
10.21
11.55
10.3
8.4
9.9
99.99
99.98
99.92
92.24
93.72
98.51
99.89
99.89
LOI
Total
Sample
Fe2O3
MS5
LS1
LS3
LS5
45.6
27.82
25.46
24.7
SiO2
18.4
39.67
45.14
43.93
Al2O3
23.97
19.16
19.52
18.6
CaO
0.16
0.137
0.144
0.186
MgO
0.058
0.087
0.083
0.075
P2O5
0.05
0.048
0.053
0.055
Na2O
0.535
0.81
0.871
0.932
K2O
0.129
1.84
0.129
1.11
Total S
0.04
0.04
0.04
0.04
TiO2
0.96
0.94
1.05
1.68
0.068
0.043
0.049
0.014
9.9
9.32
7.36
8.63
99.87
99.92
99.9
99.95
MnO2
LOI
Total
Table (continued). CIA of various oxides
Sample
CIA
Sio2
Al2o3
Cao
Mgo
P2O5
Na2O
k2O
Tio2
Mn02
LoI
US1
97.7
20.69
33.02
0.178
0.041
0.073
0.343
0.246
3.68
5.015
10.21
US2
98
27.63
33.67
0.056
0.041
0.057
0.366
0.235
3.63
0.253
12.32
US3
97.5
22.93
29.84
0.19
0.031
0.08
0.355
0.204
5.58
4.047
11.55
US4
97.8
23.24
35.66
0.163
0.045
0.082
0.324
0.304
5.43
1.215
12.53
US5
98
28.93
38.12
0.167
0.036
0.117
0.321
0.284
3.31
0.935
10.3
MS1
97.6
16.7
23.18
0.013
0.052
0.055
0.529
0.02
0.59
0.056
8.4
MS2
96.8
15.5
22.11
0.021
0.051
0.117
0.524
0.17
0.55
0.021
8.9
MS3
97.4
12.46
21.89
0.012
0.065
0.057
0.437
0.13
0.72
0.057
9.9
MS4
97.6
16.6
25.13
0.032
0.052
0.055
0.432
0.13
0.89
0.071
10.2
MS5
96.6
18.4
23.97
0.16
0.058
0.05
0.535
0.129
0.96
0.068
9.9
LS1
87.3
39.67
19.16
0.137
0.087
0.048
0.81
1.84
0.94
0.043
9.32
LS2
91.6
41.83
20.2
0.066
0.064
0.055
0.71
1.07
1.21
0.027
8.12
LS3
94.4
45.14
19.52
0.144
0.083
0.053
0.871
0.129
1.05
0.049
7.36
LS4
90.7
44.03
18.452
0.126
0.098
0.057
0.951
0.811
1.06
0.038
7.63
LS5
89.3
43.93
18.6
0.186
0.075
0.055
0.932
1.11
1.68
0.014
8.63
LS6
90.4
44.29
17.08
0.151
0.082
0.073
0.754
0.905
1.58
0.056
8.565
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