Recovery of Iron Values with the Advanced Characterization and the Reduction Kinetics of Banded Hematite With Coal

CONTENTS

Certificate

Acknowledgement

Bio-Data

Publications

Preface

Abstract

Contents

List of Tables

List of Figures

Abbreviations & Symbols

Chapter -1. Introduction
1.1. Objective of the Present Research
1.2. Scope of the Present Investigation

Chapter – 2. Geological Configuration
2.1. General Concept on Evolutionary Trend of Archean Basement
2.2. Chronostratigraphic arrangement of the Singhbhum-Orissa Craton
2.3. Generalised chronostratigraphic succession of the Singhbhum- North Orissa Craton
2.4. Metallogenic development during the Crustal Evolution of Archean
2.5. Geology of the Research Area
2.6. Local Geology of the Ghatkuri Iron Ore Deposits

Chapter – 3. Characterisation of ore
3.1 Introduction
3.2 Literature study
3.3 Materials and Method
3.3.1 Materials
3.3.2 Methods
3.3.2.1 Physical Characterisation
3.3.2.1a Ore Microscopy (Reflected light microscopy)
3.3.2.1b Petrography (transmitted light microscopy)
3.3.2.2. Mechanical Characterisation
3.3.2.2a. Bond Work Index analysis (BWIA)
3.3.2.2b. Vickers Hardness Number (VHN)
3.3.2.2c. Grain Size analysis
3.3.2.2d. Liberation Study
3.3.2.2e. Davis tube test
3.3.2.2f. Chemical analysis
3.3.2.2g. Size-Wise chemical analysis
3.3.2.2h. Sink and Float analysis
3.3.2.3. Metallurgical Characterisation
3.3.2.3a. XRD, SEM-EDS
3.4. Results and Discussion
3.4.1. Physical attributes
3.4.2. Microscopic observation
3.4.3. Power input estimation through Bond Work Index
3.4.4. Mechanical nature of grains through Vickers Hardness Number
3.4.5. Results of Grain Size Analysis
3.4.6. Nature of grain alignment through liberation characteristics
3.4.7. Davis Tube Test for the untreated BHJ
3.4.8. Chemical and Material Characterisation
3.4.9. Result of the size wise chemical assay
3.4.10. Result of sink and float analysis of BHJ
3.5. Conclusions

Chapter – 4. Kinetics Of Reduction Of Banded Haematite Jasper Ore With Coal
4.1. Introduction
4.2. Literature Study
4.3. Materials and Methods
4.3.1. Materials
4.3.1a. Raw Materials
4.3.1b. Apparatus
(i) Empty Quartz Capsule
(ii) Horizontal Tabular Furnace
4.3.2 Methods
4.3.2.1. Chemical Analysis
4.3.2.2. Characterisation Studies
4.3.2.2a. X-Ray Diffraction Analysis
4.3.2.2b. Scanning Electron Microscopy
4.3.2.3. Experimental Procedure
4.3.2.4. Rate laws in reduction
4.3.2.5. Factors controlling the rate of reduction
4.3.2.6. Various Kinetic Models used in present work
4.3.2.7. Determination of Activation Energy
4.3.2.8. Metallurgical System and Approaches in Kinetic Analysis
4.3.2.8a. Factors Determining Rate
4.4. Results and Discussion
4.4.1. Reduction of BHJ with Coal
4.4.2. Degree of reduction
4.4.3. Reduction of BHJ sample of Ghatkuri (Gua); West Singhbhum, Jharkhand at 1000 °C at constant time with varying temperature
4.4.4. Kinetics of Reduction of BHJ with Coal
4.4.5. Calculation of Activation Energy
4.4.6. Characterisation Studies
4.4.6a. X-ray Diffraction
4.4.6b. Scanning Electron Microscopy

Chapter –5. Reduction roasting of Banded Hematite Jasper with Coke Oven Gas
5.1. Introduction
5.1.1. Reduction roasting
5.1.2. Magnetic behaviour of the elements
5.2. Literature study
5.3. Materials and Methods
5.3.1. Materials
5.3.2. Methods
5.3.2a. Reactions involved in the Iron Ore Reduction
5.4. Results and Discussion
5.4.1. Effect of Particle size
5.4.2. Effect of Roasting Temperature
5.4.3. Effect of varying Roasting time
5.5. Conclusion

References

Publication (SCI)

CERTIFICATE

This is to certify that the thesis entitled “Recovery of iron values with the advanced characterization and the reduction kinetics of Banded Hematite Jasper of Ghatkuri (Gua), West Singhbhum, Jharkhand, India with coal.” being submitted by Sanjeev Kumar Das (Roll No. 2013PGPHDMM02) for the Award of the Degree of Doctor of Philosophy in Metallurgical and Materials Engineering is a record of bonafide research work carried out by him at the Department of Metallurgical and Materials Engineering, National Institute of Technology, Jamshedpur, India, and the Directorate of Atomic Minerals (ER), Jamshedpur, India under our supervision and guidance. In our opinion, the thesis fulfils the requirement according to the regulations of the Institute relating to nature and standard of the work for the award of Ph. D degree. The results embodied in this thesis are original and have not been submitted to any institute or university for the award of any Degrees.

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ACKNOWLEDGEMENTS

At the outset, the author wishes to express his ineffable sense of profound gratitude to his research supervisors; Dr. Ranjit Prasad, Associate Professor and Dr. R.P. Singh, Professor; Department of Metallurgical and Materials Engineering, National Institute of Technology, Jamshedpur for their expert guidance, encouragement and in particular for being almost always available for critical technical discussions throughout this research programme.

The author is thankful to Prof. Karunesh Kumar Shukla, Director, and Dr. Ram Babu Kodali; the former Director, National Institute of Technology, Jamshedpur, and all the concerned authorities for providing me the kind opportunity for undergoing Ph.D. at this esteemed organization.

The author is also grateful to Dr. M. K. Agrawal former Head, Department of Metallurgical and Materials Engineering & Registrar, National Institute of Technology, Jamshedpur, Dr. Ashok Kumar (DSC Member), Prof. Binod Kumar Singh, Mr. C.S. Choudhary and Dr. Rina Sahu, for their instant support throughout the Ph. D work.

The author is also indebted to Dr. Anil Kumar Choudhary, Associate Professor, Department of Civil Engineering, National Institute of Technology, Jamshedpur, for volunteering his help every now and then in various ways during the research tenure.

The author submits his sincere thanks to Dr. Srinivasan Ranganathan, Chief Scientist, and Dr. Abhilash, Scientist, MER Division, National Metallurgical Laboratory, Jamshedpur for their encouraging support and guidance during the kinetics of reduction of Banded Hematite Jasper with coal.

The author is also thankful to the Dr. Vinod Kumar (Technical Officer), MNP Division, Dr. R.K. Rath, Dr. Ari Vidyadhar, Dr. M.K. Mohanta, Dr. Mamta Kumari (CSIR-National Metallurgical Laboratory), Jamshedpur for their instant support and continuing discussion in resolving the critical matter surge during the entire PhD work.

The author is also grateful to Dr. Ajit Kumar Behra (Assistant Professor), Department of Metallurgical and Materials Engineering, National Institute of Technology, Rourkela (Odisha) for his indubitable support during the SEM-EDAX of the roasted sample.

The author is also grateful to Dr. Ajay Kumar (Scientist) Eastern Region, Directorate of Atomic Mineral, for his support in the Polished Section, Thin Section and Vickers Hardness Test of the BHJ ore.

The author is also grateful to Hirak Majumdar, General Manager, Rungta Iron Ore Mines Limited, for providing internal support to collect samples from the Ghatkuri Iron Ore Mines, Gua, West Singhbhum, Jharkhand.

The author is also thankful to the all Technical Staff, officials, and colleagues from Department of Metallurgical and Materials Engineering for their support in every steps of the research work.

The author has no words to express his deep sense of gratitude to his elder brothers Pinaki Prasad Das and Deo Prasad Das for their sentimental attachment and encouragement during the entire work.

The author is indebted to his parents- Shri Trilochan Das and Smt. Shishu Rani Das for their constant encouragement to pursue higher study, everlasting love and affection.

Last but not the least the author is thankful to the ALMIGHTY who kept him fit for the necessary hard work during this period.

Place: Jamshedpur

Date:

(Sanjeev Kumar Das)

BIO-DATA

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- Preparation and study of Polished and Thin section of rock. (30 days intensive training in the Department of Atomic Energy; Atomic Minerals Directorate for Exploration and Research: Eastern Region, Jamshedpur)
- Working experience of more than 24 months in Horizontal Tabular Furnace in CSIR- National Metallurgical Laboratory; Jamshedpur.

Publications

Science Citation Index Expanded (Journal)

Sanjeev Kumar Das, Ranjit Prasad, R.P. Singh and Abhilash, 2017 Physical, Mechanical and Metallurgical Characteristics Of Banded Hematite Jasper Of Ghatkuri (Gua), Jharkhand. Journal Geological Society of India (Springer), Vol.90, pp. 623-627.

Sanjeev Kumar Das, Ranjit Prasad and Rajendra Prasad Singh, 2018. Characterisation- Assisted Reduction Roasting of BHJ, West Singhbhum, Jharkhand, India, Transactions of the Indian Institute of Metals (Springer), https://doi.org/10.1007/s12666-017-1270-z.

Science Citation Index (Journal)

Sanjeev Kumar Das, Ranjit Prasad, Rajendra Prasad Singh and Srinivasan Ranganathan, 2017. Kinetics of Reduction of Banded Haematite Jasper Ore With Coal, Transactions of the Institutions of Mining and Metallurgy: Section C (Mineral Processing and Extractive Metallurgy) (communicated).

International Conference/ Seminar Proceedings

Sanjeev Kumar Das and Ranjit Prasad, Megascopic & Microscopic study of BHQ, In: The International Conference on Processing of Lean Grade and Urban Ores (IC-LGO 2015), Jamshedpur (CSIR- National Metallurgical Laboratory), pp. 23.

Sanjeev Kumar Das and Ranjit Prasad, Physical and Optical Characterisation of Three Iron Ore Mines of Noamundi, West Singhbhum, Jharkhand, In: The 16th International Seminar on Mineral Processing Technology, 1-3 February 2017, Mahabalipuram, Chennai (Tamilnadu), pp. 659-665.

National Conference/ Symposium

Sanjeev Kumar Das and Ranjit Prasad, The role of characterisation in beneficiation of BHJ, West Singhbhum, Jharkhand, (Poster) In: 71st Annual Technical Meeting (NMD- 2017), 11-14 November 2017, BITS Pilani, Goa, India, pp. 1.

Sumit Kumar Das, Sanjeev Kumar Das and Dr. Ranjit Prasad, Characterisation of Banded Hematite Jasper, In: 67th Annual Technical Meeting (NMD-2013), 12-15 November 2013 , IIT-BHU.

Sanjeev Kumar Das and Ranjit Prasad, BHJ/ BHQ is an alternative source of ceramic industry, In: National Conference on Environmental Challenges and solutions (NC-ECS 2015), 5-6 November 2015, CSIR-National Metallurgical Laboratory, Jamshedpur, India.

Sanjeev Kumar Das, Dr. Ranjit Prasad and Dr. Vinod Kumar, Bond Work Index analysis of BHJ of Noamundi area, West Singhbhum, Jharkhand, In: 70th Annual Technical Meeting (NMD-ATM 2016), 11-14 November 2016, IIT Kanpur.

Aswini Majhi, Sanjeev Kumar Das, Dr. D.N.Sadhu and Dr. B. Kumar, Prospect of Pellet Plant in Iron Ore Belt of Singhbhum, Jharkhand, India, In: XVI Annual National Geography Conference, 31st January- 01st February 2015. Kolhan University, Chaibasa.

Technical Seminar

Sanjeev Kumar Das, Use of low grade ore in steel industries for sustainable development, In: Silver Jubilee Celebration (Usha Martin) on Opportunities and Challenges in Present Steel Scenario, 14th December 2015 (SNTI Auditorium) Jamshedpur.

PREFACE

In view of the surging demand of iron ore and continuously depleting high grade resources; the policy makers have made stringent regulations for the protection and conservation of the high grade ore for the sustainable development of the society. They have stressed on the use of the low grade ore i.e. Banded Hematite Jasper, Banded Hematite Quartzite, fines, slimes and other low grade goethitic iron ore. The use of such an ore also reduces the environmental impact and health hazards. It also reduces the over burden and area of dumping. Taking all these aspects into consideration a research programme has been designed under the co-supervision of Dr. Ranjit Prasad, HOD & Associate Professor and Dr. R.P. Singh, Professor, National Institute of Technology, Jamshedpur. In this regard, comprehensive literature study has been carried out to understand its utilisation in the industry and the current parameters employed for its processing. The research study also deals with the kinetics of reduction of Banded Hematite Jasper with coal to understand its reduction behaviour with varying temperature and time. The thesis has been divided into several chapters dealing with extensive literature and experimental studies. It focuses on the geological aspects (i.e. correlation with other mineral/ rock in the type area, lithological alignment, availability of different types of fauna and flora and the geomorphological attributes. Second part of the thesis is based on the experimental aspects of Banded Hematite Jasper. It includes different methods of characterisation and its implications on the development of new processes for beneficiation. These experimental techniques also help in understanding the interlocking pattern, % of ore & gangue, extent of liberation and magnetic behaviour of the ore. The experimental section also describes the mechanical and metallurgical behaviour of the ore (Bond Work Index, Vickers Hardness Test). Those parameters help in knowing inter-molecular structure, presence of hydroxyl ion and up to some extent it reveals the quantitative nature of the ore. The experimental part also describes the kinetic behaviour of the ore with coal (i.e. extent of metallisation, factors responsible for reducibility and the activation energy) required for the ore. The experimental section describes the temperature of reduction of the ore with coke oven gas. In this section focus has been given to evolve a correlation between the grain size and the residence time with varying temperature.

Abstract

Iron ore is the basic raw material for steel industries. It appears in Nature in different forms- hematite, magnetite (high grade) to detritus goethite (low grade) with different proportion of ore and gangue minerals depending upon their mode of deposition. The iron and steel industry has traditionally used only the highest grade of ore due to its abundance in India. However, due to the rapidly expanding demand for steel, the high grade reserves are depleting very fast rate. In order to avoid a crisis due to limited availability of the ore, the government has inacted regulations to encourage enhanced usage of low grade ores. As the high grade ore gets depleted, the mines produce higher proportion of low grade ores. The steel industry is keen to develop processes for establishing the low grade ores. A main reason for this is the low transportation cost which would compensate any cost increase due to the lower quality of the ore, in the production of iron. Banded Hematite Quartzite and Banded Hematite Jasper have huge potential to form the source of iron ore for the next generation. It contains almost 30- 40% iron values. Millions of tons of BHJ, BHQ are stockpiled in or around the mine site, where hematite ore is mined. Geologically, the ore belongs to the Iron-Ore-Group of Singhbhum-Orissa region. This ore is present in other parts of India, also. As of today; exploitation of these ores is still quite limited in absence of an economically viable process. The use of the ores would not only reduce the overburden but also contribute as a low cost of source of iron. Therefore, a study was carried out to lay a foundation for future development for exploitation of this ore. Investigations were carried out to understand the physical, mechanical and metallurgical behaviour of the ore. Microscopic observation of the polished sections showed specks of iron ore embedded in highly intricate fine grained silicate ground mass. It also revealed that a thin silica vein cut across the foliation plane. In some locations, leaching out of silica has been noticed as evidenced by tinge of reddish brown colour. Bond Work Index and Vickers Hardness test show that the ore is highly compact with low porosity and less permeability. Bond Work Index suggests that liberation of iron oxide from the matrix may prove to be uneconomical; using traditional beneficiation routes. Vickers Hardness Number shows that the majority of grains are hematitic in composition. Metallurgical characteristics show that 18-25 % concentration in the size range of -125+106 micron and only the 0.50 % was in the size range of -212+180 micron. There is 4-6% loss of mass during the experiment. The ore contained 45.08 % Fe (T) and 35.64 % SiO2, the rest being gangue minerals. Iron- bearing minerals and silica were embedded in a fine grained matrix of oxy-hydrated mineral and kaolinite. EDS spectra revealed very low sulphur. XRD revealed that the banded hematite jasper was oxy-hydroxy hematitic in composition. Hematite and silica were the major phases observed under XRD while alumina (Al2O3) was a minor phase. The XRD analysis also corroborated the petrography of the ore body. Investigations were carried out to understand the kinetics of the Banded Hematite Jasper with coal. Experiments were conducted on the temperature range of 1000-1200 °C. At 1000 and 1100 °C, the degree of reduction was low. It increased four folds at 1200 °C compared to the reduction at lower temperatures. Silicon carbide (SiC) was formed as the predominant phase during reduction at 1000- 1100 °C. This hindered the reduction of iron oxide in the ore. This phase appears to be unstable at temperatures above 1200 °C. Absence of this phase accelerated the reduction of iron oxide at higher temperatures. At 1000 °C, reduction was controlled by chemical reaction kinetics. At higher temperature, it was controlled by diffusion. The activation energy for reduction at higher temperature was 601 kJ/mol. This indicates that reduction was controlled by the Bouduoard reaction. The relatively high temperature required for the reduction of iron oxide in the ore is an important feature that should be taken into consideration when processes are developed for the exploitation of this as a source of iron.

The ore was feebly magnetic owing to the fact that it is hematitic. This hematite and silica were intermingled with each other at micro level therefore direct beneficiation of the Banded Hematite Jasper was very difficult. Experiments were carried out on the low temperature reduction roasting of Banded Hematite Jasper with coke oven gas. In this process, non-magnetic or feebly magnetised substances Banded Hematite Jasper was converted into the magnetite or metallic iron under weakly reducing atmosphere at (500-900 °C). In this case, excess reduction was always avoided as there will be the possibility of diffusion inside the operating system and the formation of wustite (unstable below 570 °C). It was found that when magnetite was stable at higher operating temperature improves the kinetics. From Boudouard Equilibrium Curve, it was clear that when a solid carbonaceous reductant is present in the ore mix, heating above 650 °C reduces magnetite to wustite. Reduction roasting of the Banded Hematite Jasper with coke oven gas was highly energy-efficient and subsequent grinding of the ore was much easier compared to other processes and gives better separation of the concentrates of the iron values. Results show that the optimised parameters for reduction roasting were reduction temperature of 600 °C with a residence time of 60 minutes. A particle size of 13 mm gave the best results with respect to total recovery of iron.

LIST OF TABLES

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LIST OF FIGURES

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Abbreviations

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Symbols

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CHAPTER-1

INTRODUCTION

Steel is v ry mport nt ompon nt o ny ountry s onomy n s t r v n or of modern civilisation. In India, Iron is produced in integrated steel plants, almost exclusively from the hematite ore. But, the demand for the ore is increasing so rapidly that the available reserves of hematite may not be sufficient to feed the industry beyond twenty years from now (Indian Mineral Year Book, 2015). The total resources of iron ore in India is expected to be around 28.52 billion tons of which about 17.88 billion tons of haematite and 10.64 billion tons of magnetite ore. In order to ensure that the iron and steel industry survives beyond the next two decades, it must quickly adapt to the utilisation of low grade ores. In India, a large variety of iron ores are found. Of these, some cannot be mined economically. According to the Steel and Metallurgy, (2015) about 30% low grade iron ore (5.34BT) of total reserves is available for supply to iron and steel industry. In India; very little work has been carried out on the use of the low grade ores and work on the Banded Hematite Jasper and Banded Hematite Quartzite is also quite meagre. It is estimated that at the present rate of usage; high grade hematite reserve shall be depleted in next twenty years (Indian Mineral Year Book, 2015) and BHJ and BHQ are expected to be the main source of iron for the industry. In the current investigation, Banded Hematite Jasper which is one of the low grades of ores available in significant quantity in India has been studied. It is estimated that the total reserves of this ore may be about ten times that of the available reserves of Haematite ore (Iron and Steel Vision 2020, 2011). Previous studies reported in literature have shown that this iron is hard and compact, less porous and less permeable and contains low alumina and phosphorus. Those properties make this ore a promising future raw material for the steel industry. In fact, it is known that the formation of hematite is due to the leaching out of silica from the parent BHJ rock unit (Upadhyay et al., 2009). BHJ forms the base of iron ore deposits of the Singhbhum district. This study focuses on the mineralogical characterisation of the ore and investigations on the carbothermic reduction. It is expected that this study would lay the foundation for future process developments for the economical exploitation of this ore in the iron and steel industry.

1.1. Objective of the Present Research:

The current research is basically focused on the recovery of iron values with the advanced characterisation and the reduction kinetics of Banded Hematite Jasper with coal.

The primary objectives of the proposed research are

- To understand the physical, optical and mechanical characteristics of the ore collected from Ghatkuri Iron Ore Mines; Gua, West Singhbhum, Jharkhand, India through detailed characterisation.
- To upgrade the ore from study area at low cost and low energy consumption.
- To study the effect of various parameters on the reduction of the ore from study area at low temperature with coke oven gas.
- To understand the reduction kinetics of Banded Hematite Jasper with coal from study area.

1.2. Scope of the Present Investigation:

The present study deals with both basic and applied studies on the Banded Hematite Jasper. It will focus on the utilisation of mine waste (i.e. in the form of tailings, fines and lump of BHJ/BHQ). In this study, a comprehensive mineralogical characterisation- both quantitative and qualitative- has been carried out. It is one of the basic aspects that has to get due attention before any attempt for processing of ore is made. Mineral processing technology has played an important role in separating and recovering ore minerals from gangue in a commercially viable method and is mainly based on the process of mineral liberation and the process of mineral separation. Therefore it is important to get a clear understanding about the ore and gangue, its texture, structure and interlocking pattern. The present study also deals with the kinetic behaviour of the ore with the coal. It will be used for estimating the extent of metallisation and the energy consumed during the processing of the ore. These studies will help in developing new processes for the utilisation of this low grade ore.

The scope of this research includes the physical, optical and mechanical characterisation. Experiments have been carried out to evolve a suitable process for beneficiation of the ore. Low temperature reduction roasting using coke oven gas followed by magnetic separation has been used for beneficiation. The work plan under this research programme has been structured in three different parts: Characterisation, Reduction Roasting followed by magnetic separation and Kinetic study of BHJ with coal.

CHAPTER – 2

GEOLOGICAL CONFIGURATION

2.1. General Concept on Evolutionary Trend of Archean Basement

There were many stage wise theories regarding the origin and formation of iron ore in the Supracrustal Precambrian Basement of Singhbhum. The Precambrian Basement evolved in four successive phases of sedimentatation, magmatism, plutonism and orogeny. These phases were well delineated by the structure of the area. The lower stage was characterised by the presence of basic rocks in the form of primordial crust. These rocks were preserved as undigested masses of xenoliths in vast country of granitic gneisses that were formed at the second stage of evolution of the Precambrian Basement. The granitic gneisses were formed either by the differentiation of the basaltic magma or by the matasomatic transformation of earlier existing rocks. At the third stage, the protogeosynclines were formed over a basement of granitic rocks. In this stage, rich metalliferrous deposits of iron, manganese and chromium were laid down in protogeosyncline. They later on faced volcanic activity. This phenomenon occurred intermittently and the present form is found as volcano-sedimentary rock units. At some places, they appear in rhythm. The protogeosynclines experienced an inversion phase at the close of the sedimentary history. The inversion phase was represented by the orogenic deformation and emplacement of granitic rocks that marks the fourth stage of the evolution of the Precambrian Basement. The earliest phase was represented by Archean Era and well characterised by repeated phases of orogenic deformation, plutonism and high grade metamorphism (Kumar, 1992).

There is disagreement among the geologists and researchers regarding the age of formation of the rock. Geochronology of Archean is illustrated below in Table No. 2.1.

Table 2.1: Geochronology of Archean

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Source: Fundamentals of Historical Geology and Stratigraphy of India (Kumar, 1992).

The oldest orogenic cycle of Early Archean age (more than 3.2 billion years ago) are observed only as relics in some Archean areas. The orogenic cycle of middle archean age (more than 2.9 billion years ago) has been well established in the Singhbhum Keonjhar region of north eastern peninsula as Iron-Ore-Orogeny.

Singhbhum-Orissa Province: The Singhbhum region (Noamundi, Gua, Jamda, Kiriburu and Manoharpur) and Mayurbhanj, Keonjhar and Bonai district of Orissa are well known for their high grade iron ore deposits. The region is traversed by Singhbhum Shear Zone (Copper Belt Thrust) extending over a strike length of 160 km. It trends eastward from Porahat and then takes a southward swing to Jamshedpur. The shear zone separates a northern terrain of more highly metamorphosed rocks and southern terrain of relatively less metamorphosed rocks. Sarkar and Saha (1977) have shown that this shear zone separates two Precambrian provinces of the Indian Shield: an older province in the south which stabilised after Iron-Ore-Orogenic cycle closing about 2900 million years ago and a younger province in the north that underwent the Singhbhum Orogenic cycle closing at about 850 million years ago.

The rock succession of the tract in the south of Singhbhum Shear Zone consists of a lower archean basement of Older Metamorphic Group invaded by the Biotite-Tonalite-Gneiss. The Iron Ore Group rocks are unconformably deposited over the eroded lower archean Basement. These rocks are folded and trending towards NNE-NNW and experienced the low grade metamorphism of the Singhbhum Granite (Iron Ore Orogeny). After a long period of erosion, the rocks of Singhbhum Group were deposited along the northern edge of the stabilised Iron-Ore-Craton. The rocks of the Singhbhum Group went through a first generation of folding and uplift leading to retreat of ocean and sub-aerial erosion (Kumar, 1992).

2.2. Chronostratigraphic arrangement of the Singhbhum-Orissa Craton

The major chronostratigraphic units of the Singhbhum-Orissa Craton and its chief mineral assemblages are summarised as follows:

Older Metamorphic Group (OMG): The older rocks possibly lying to the south of Singhbhum Shear Zone were named by Dunn (1929) as the Older Metamorphics. The rocks consist predominantly with metamorphosed pelitic, arenaceous, occasionally calcareous sediments and mafic-ultramafic rocks. The rocks are regionally metamorphosed to amphibolite facies. The meta-sediments are mainly represented by quartz-muscovite-biotite-schist, quartz-sericite-schist, quartzite, quartz-magnetite-gneiss and quartz-magnetite-cummingtonite-schist. The metamorphosed mafic ultramafic rocks are mainly schistose and banded amphibolites. Saha et al. (1984) based on mineralogy and geochemistry believed that hornblende schist and some massive varieties are formed from magmatic rocks (ortho-amphibolite), whereas the banded amphibolites are formed by metamorphism of calc magnesian sediments (para- amphibolite). These rocks are considered to occur as isolated exposures within the general mass of Singhbhum-Granite.

Older Metamorphic Tonalite Gneiss (OMTG ) : The OMG rocks are intruded and partly granitised by a suite of OMTG. Compositionally they vary from biotite/hornblende rich tonalite through trondhjemite to granodiorite and shows structural similarity with the OMG rocks. A prominent gneissic foliation is pervasive in OMTG. Saha et al. (1984) compared OMTG with early Archean tonalities and trondhjemites from different parts of the world and showed that the composition of OMTG in the FeO-MgO-(Na2O+K2O) diagram mainly falls in the calc-alkaline field. Saha (1994) proposed that OMTG was possibly formed by fractional crystallization of basaltic/ultramafic magma or by partial fusion-cum-contamination of the parent rock like quartz-eclogite/garnet or amphibolite/amphibolite/greywacke. OMTG also contains some small rafts of the possible greenstone rocks including BIF (Misra et al., 1999). The closing date of metamorphism and emplacement of the tonalite gneiss as indicated by Rb-Sr and K-Ar mineral and whole rock dating is 3200 million years (Sarkar et al., 1979).

Singhbhum Granite: The Singhbhum Granite batholithic complex is composed of at least 12 separate magmatic bodies which are emplaced in three successive but closely related phases (Saha, 1972) viz. Phase-I and Phase-II i.e. SBG-A and Phase-III as SBG-B. Phase-I rocks vary from K-poor granodiorite to trondhjemite mainly, whereas Phase- II and Phase-III rocks range from granodiorite to adamellite mainly. At margins of the batholiths, chloritic or epidotic granodiorites and pyroxene diorite have developed. The main mass shows distinct N-S or NNE-SSW foliation in parallelism with the foliation of the host rock of the Iron Ore Group. Roof pendents of rocks of Iron Ore Group and patches of granitised amphibolites of the Older Metamorphic Group are known to occur within the Singhbhum Granite. The time of emplacement of the Singhbhum Granite is regarded as syn- to post- tectonic to the deformation of the rocks of the Iron Ore Group.

Rb-Sr whole rock isochron date is around 2950 million years. (Sarkar and Saha, 1982).

Iron Ore Group: The rocks were exposed over Older Metamorphics and found in southern Singhbhum and Keonjhar Dist of Orissa. The series was first named as Iron Ore Series by Jones (1934). The IOG comprises typical greenstone rocks with a thick pile of low grade metamorphosed sediments, volcanics and mafic-ultramafic plutons. The rocks are phyllites, Tuffaceous shales/phyllites, manganese ores, BIF ( banded hematite jasper/quartzite, banded martite jasper/quartzite, banded magnetite quartzite/jasper ) with iron ores, ferruginous quartzite, cherty banded quartzite, local dolomitic rocks and conglomerate, basic to acid volcanics, mafic-ultramafic plutons with titaniferous magnetite and chromite ores, etc. The rocks are localized mainly in the two major NNE trending greenstone belts and sedimentary basins. The western belt is also called as Jamda-Koira belt (named after two type areas) which comprises the Noamundi basin. At least two phases of isoclinal folding and a later open-type cross fold are discernable in the IOG rocks of this belt. The eastern greenstone belt comprises the IOG rocks of Gorumahisani-Sulaipat-Badampahar and Tomka-Daitari iron ore basins. The trend of the Tomka-Daitari basin (ENE) is a little different from that of the Gorumahisani- Sulaipat-Badampahar basin (NNE) due to later deformational effects, but continuity of structures and lithology of these two regions are found in some apparently isolated IOG outcrops in the intervening areas [ Banerji (1977), Chakraborty and Majumder (2002), Acharya (2002)] observed at least three major phases of folding in the Tomka-Daitari area. The Gorumahisani-Sulaipat- Badampahar part with a general NNE-trend, locally changing to NNW near Gorumahisani, also shows at least two earlier phases of isoclinal folding and a later cross fold . This eastern belt contains rocks like phyllites, tuffaceous shales/phyllites, carbonaceous phyllite, chloritic shale/phyllite, agglomerate cherty/gritty quartzite, fuchsite-quartzite, grunerite- quartzite, Banded Iron Formation (banded hematite jasper/quartzite, banded magnetite jasper/quartzite) with iron ores, conglomerate, hornblende schist, amphibolite, talc- tremolite-schist, quartz-chlorite actinolite-schist, serpentinite various ultramafics and associated chromite ores, gabbro-norite-anorthosite with titaniferous magnetite etc. The basal conglomerate contains pebbles of SBG-A, OMTG and OMG. The ore is mainly composed of magnetite but considerably martitized in places. In Badampahar mines, the ore is mainly hematitic (hard, laminated ore) and associated with banded hematite quartzite and phyllite, all of which dipping northerly. The south eastern wing of the Badampahar range shows a large synclinal structure in the basal quartzite where bands of fuchsite-quartzite and dark grey or nearly black cherty quartzite are also present. Saha et al. (1988) proposed that the IOG rocks should have been formed between the emplacement of SBG-A (3300 Ma) and SBG-B (3100 Ma), but (Mukhopadhyay et al., 2008) reported 3506+/_2.3 Ma U-Pb SHRIMP zircon age for dacitic lava of the IOG from Tomka-Daittari area.

Singhbhum Group: Lying north of the Singhbhum Shear Zone and extends over 200 km. in east west direction of Singhbhum Shear Zone. Dunn and Dey (1942) correlated this succession with the succession of Iron Ore Group lying in the south of Singhbhum Shear Zone on the basis of general lithological similarities and the presence of iron ore beds in the upper part of the succession. Sarkar and Saha (1963, 1977) renamed the succession lying to the north of Singhbhum Shear Zone as Singhbhum Group.

Dhanjori Group: The Dhanjori Group includes the Dhanjori basin proper in the northern part and the Simlipal basin in the southern part. The general trend of this mobile belt is north-south and both the basins comprise sediments and magmatic rocks. The Dhanjori basin suffered multiphase tectonic deformation and contains mainly intercalated sediments and basic volcanics. The lower part of Dhanjori lava is komatiitic and the upper part is more tholeiitic. The metavolcanic rocks are chlorite-phyllite, chlorite-biotite schist, talc-chlorite-schist/phyllite etc. The sediments are mostly transformed to different types of quartzite and meta-pelites. The Dhanjori rocks are separated from the Singhbhum Group by the Singhbhum Thrust Zone. Dhanjoris are the possible parent rocks for Cu, Ni, Mo, Au, Fe, Ti, V, P, U, Rare Earth Elements mineralization in the eastern part of the Singhbhum Thrust Zone. The Simlipal basin attains a lopolithic structure containing intermittent bands of volcanics (mainly spilitic lavas and tuffs) and orthoquartzitic sandstones (Iyenger and Banerjee, 1964). A differentiated tholeiitic sill (Amjori sill) has intruded the Simlipal volcanics and sediments near the centre of the basin. This sill is about 800 meter thick and contains dunite at the bottom passing upward to peridotite, picrate gabbro and quartz-diorite. Recently prospecting has been going on for platinum group elements in different parts of the Simlipal.

Jagannathpur-Malangtoli Belt: The JMB is almost entirely composed of tholeiitic lavas with minor andesitic flows. The lavas are mostly vesicular in character and at places contain pillow structures. Banerjee (1982) estimated it is approximately 25-30 flows. Saha (1994) observed that in the east and south JMB overlies unconformably over the Singhbhum Granite but it is faulted against the Noamundi iron ore basin. Near Malangtoli some quartzitic sandstone and conglomerate (Kolhan) overlie the lava sequence with an Unconformity.

Mayurbhanj granite: Mayurbhanj granite surrounded by Singhbhum Granite batholiths and occurs on the east of the Gorumahisani-Badampahar iron ore belt. It is composed of three units (Saha et al., 1977) fine-grained granophyric biotite- hornblende-alkali feldspar granite, a coarse-grained ferrohastingsite-biotite-granite and a biotite-aplogranite. Iyenger et al. (1981) from Rb-Sr isochron, determined the age of Mayurbhanj granophyres as 2084 +/- 70 Ma which also corresponds to the c. 2100 Ma age of Mayurbhanj granite by [ Saha et al. (1988) Dunn and Dey, (1942)] also justifies Mayurbhanj granite to be a part of Singhbhum granite which has also been supported by 3100 Ma Pb-Pb isochron age of Misra et al. (1999) This indicates possibly that the Mayurbhanj granite belongs to part of the Singhbhum granite Phase – II.

Nilgiri Granite: Nilgiri granite occurs on the southeast of the Singhbhum granite batholith and it is principally composed of tonalite, granodiorite and granite. The Pb-Pb isochron ages of Nilgiri granite are determined as 3308 Ma, 3292 Ma, 3225 Ma and 3294 Ma, whereas the Sm-Nd isochron ages of the same rocks are 3715 Ma, 3270 Ma, 3290 Ma and 3130 Ma respectively (Saha 1994). Thus petrologically and geochronologically Nilgiri granite is comparable with SBG-A except the first one i.e. 3715 Ma which may be a still older unit.

Bonai Granite: Bonai granite on the southwest of the Noamundi-Jamda- Koira iron ore belt comprises mainly porphyritic granite and equigranular granite with numerous tonalitic xenoliths. It occurs mainly at the core of the regional antiform adjacent to the Noamundi synclinorium. Sengupta et al. (1991) from Pb-Pb isochron, reported the average age of Bonai granitoids as 3163 +/_ 126 Ma and those of tonalite younger major part of Bonai granite is comparable with SBG-B, while the older tonalitic and trondhjemitic parts may be synchronous with OMTG or SBG-A.

2.3. Generalised chronostratigraphic succession of the Singhbhum- North Orissa Craton (Saha; 1988)

Abbildung in dieser Leseprobe nicht enthalten

2.4. Metallogenic development during the Crustal Evolution of Archean:

Mineralisation in the Archean belt is divided into five subgroup. They are well placed in different phases of Iron Ore Group rocks.

- Fe-Mn ores associated with BIFs and phyllites.
- Chromite ore associated with ultramafics.
- Titaniferous magnetite ore associated with gabbro-norite- anorthosite.
- Gold associated with metamorphosed mafic-ultramafics and hydrothermal veins.
- Platinum group metals, Cu-Ni associated with mafics and ultra-mafics.

Fe-Mn Ores: The vast sedimentary deposits of Iron and Manganese ore has been found in the Iron Ore Group in the three major iron ore belt in the east, west and south of Singhbhum Granite batholiths in association with BIF (banded hematite jasper/quartzite, banded magnetite jasper/quartzite). In the western greenstone belt i.e. Noamundi-Jamda-Koira belt rich deposits of iron ore with over 60% Fe occur in Noamundi, Joda, Thakurani hills, Khondband, Kalimati, Barsua, Koira, Kiriburu, Meghataburu, Lutuburu, Pansiraburu, Ghatkuri, Bolani, Jamda, Gua and Chiria areas distributed in a regional synclinorium (Noamundi synclinorium) which is isoclinally folded with NNE – plunging axis. The western iron ore belt of this regional syncline is relatively continuous (about 50 km long), but the eastern belt is highly dissected by numerous faults and minor folds. At least two phases of isoclinal folding and a later open-type cross fold are evident in these iron ore areas. Mineralogically the iron ore is mainly composed of hematite or martite and the silicate band is mainly made of jasper. The following types of iron ores are usually found in the Noamundi-Jamda-Koira belt:

i) Massive ore – Dark brown to steel grey compact hematite with faint trace of bedding. Fe is usually greater than 65%.
ii) Laminated hard ore – Dark brown well bedded or laminated hematitic ore with minimum siliceous band.
iii) Flaky friable ore and relatively soft ore having open spaces in between the laminae and the open spaces usually filled by finely granular dusty hematite with some silica.
iv) Blue dust is fine grained or flaky hematite having a metallic blue colour and almost devoid of silica. It is high grade iron ore.
v) Lateritic ore composed of hematite and iron hydroxide minerals mainly. It is low grade iron ore (Fe = 50-60%) and usually occurs as thin cover over the higher grade massive or laminated ore.

In all types of iron ores the constituent ore minerals are mainly hematite or martite with variable amounts of goethite and minor amounts of magnetite and siderite. The gangue material is principally composed of cherty silica (in the form of jasper or quartzite), kaolinitic clay and minor amounts of chlorite, quartz, biotite and rutile. Spencer and Percival (1940) also found some oolitic grains of hematite in the ore. In the Noamundi- Jamda-Koira belt, manganese mineralization is a very conspicuous feature in close association with iron 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. Mineralogically, the manganese ores are principally composed of pyrolusite, cryptomelane and manganite i.e. low temperature higher oxides of Mn,

Chromite ore: Chromite ore was deposited in association with Iron Ore Group ultramafics in the eastern, southern and western parts of Greenstone-granite terrain. In the eastern part, chromite ores occur in Baula, Nuasahi, Bangur areas of Mayurbhanj district, Odisha. In the southern part chromite mineralization is found in Sukinda valley including Kathapal, Kalrangi, Sukrangi, Kaliapani and Saruabil areas of Dhenkanal and Cuttack districts, Odisha (Baidya, 2015). The chromite ores in the above two sectors belong to the eastern greenstone belt. Chromite mineralized zone runs from the Chitang Buru hill on the NNW to Roro hill on the SSE over a length of about 1 km. The host rocks along with the chromite bands also show open type folds plunging low to moderate towards east. Chromite ore bodies are mainly of lensoid and banded types.

Titaniferous Magnetite Ores: These ores are associated with gabbro-norite-anorthosite suite of rocks which belong to a part of the eastern greenstone belt. Ore deposits are found in Kumhardubi, Betjharan, Dublabera, Baula and Nuasahi areas in parts of Jharkhand and Odisha. Ore bodies occur as lenses, veins and massive bands. Dunn (1937), Roy (1955), Dasgupta (1969) and Banerjee (1984) reported significant concentration of vanadium in these titaniferous magnetite ores.

Gold mineralisation: Gold mineralization is associated with both eastern and western greenstone belts. In the eastern greenstone belt and near Gorumahisani iron ore mines, gold mineralization is reported from Kundarkocha and Digarsahi areas of the Singhbhum district, Jharkhand. The gold-quartz veins are associated with Iron Ore Group rocks like metamorphosed ultramafics and komatiitic rocks (talc-tremolite-schist and talc-chlorite schist), fuchsite-quartzite, biotite-chlorite-quartzite, Banded Iron Formation, carbonaceous and sulphide-bearing phyllites, mica-schist, metamorphosed calc-magnesian rocks, banded cherts etc. Dunn (1937) suggested that the gold-quartz veins are parallel to the sharply folded or kinked monoclinal structure of the associated schists. The gold-quartz veins vary from a few mm to nearly 2m in thickness. The gold- quartz lodes mostly occur at the contact of nearly black carbonaceous phyllite (footwall) and the green cherty phyllite (hanging wall). The lodes are mostly dark grey/bluish grey in colour where gold occurs as hair-thin veinlets or fine disseminated crystals.

Platinum Group Elements and Cu-Ni-Mineralization: In the chromiferous ultramafics of the Baula-Nuasahi area of the eastern greenstone belt, platinum group of elements have been reported by the Geological Survey of India, 1996.

2.5. Geology of the Research Area:

Topographical Overview: The Ghatkuri Iron Ore Mines belongs to the M/S Rungta Mines Private Limited occupies an area of 229.863 hectares. The area is situated in between the Survey of India toposheet no. F45H8 and F45H7 (73F/8 NE and 73F/7 SE) (1:25,000). The area is located 750 meter far from the western bank of the Karo river. The area is surrounded by certain small hills and with network of streams. The lease area falls under Ghatkuri Reserve Forest. The highest and lowest contours are 804 meter and 413 meter respectively. These streams form the drainage pattern of the area and at the eastern side they join with the Karo river. The area is a dense forest dominated by various kinds of fauna (Jackal, Monkey, Rabbit and Squirrel) and flora (herb, shrubs, sal, mahua, kendu and pipal). The temperature varies from 108 °F (at summer) to 40 °F (at winter). The ground water level remains at a depth of 13 meter from the surface during the dry season but rise to about 5 meter depth during rainy season (M/S Rungta Iron Ore Mines Limited; Chaibasa, Personal communications).

Regional/ General Geology: The Ghatkuri Iron Ore deposit forms a part of Precambrian Sedimentary Formations of the Iron Ore Group of rocks developed in South Singhbhum and the adjoining districts of Sundergarh and Keonjhar. It is bounded by latitude 22°20' N to 20°40'N and longitude 85°32'E to 85°50'E. The general strike of the formations in the North Singhbhum is EW but gradually changing over to NW-SE in the eastern part and in the adjoining area of Mayurbhanj district of Orissa. This part of Singhbhum is marked by a zone of shear along which rocks have thrust towards the south and metamorphosed. The shear zone shows intrusions of soda- granophyre and contains deposits of copper, apatite and magnetite. Rocks lying at the north of the shear zone consist of phyllites and tuffs with basic intrusives at the bottom. Above them appear a series of lava flows which occupy a fairly broad belt of the country.

The iron ore group of rocks consists mainly of Banded Hematite Quartzite and shale with intercalations of lava flows and tuffs. Dunn (1942) believes that certain phyllites and shale in Eastern and Southern Singhbhum were originally volcanic tuffs and they have been either silicified or replaced by iron ore to some extent, when the latter in contact with banded ferruginous rocks. In some places the phyllites are manganiferous and have been partly replaced by manganese ore.

The iron ore group of rocks is overlain by the kolhan series which is assumed to be equivalent of the Cuddapah group of rocks. The kolhan group consists of basal conglomerate and sandstone overlain by some limestone and shale. This group is found to overlap the various stages of iron ore group of rocks and also the intrusive granites when followed from North to South. (M/S Rungta Iron Ore Mines Limited; Chaibasa, Personal communications)

The general geological succession of the study area is as follows: Kolhan Group (Basal Conglomerates and sand stone).

----------------------Unconformity-----------------------------

Phyllites and tuffs with magnesite and sometimes dolomite. Banded Hematite Quartzite.

Phyllites and tuffs, Sangramsai Conglomerates and basic igneous rocks.

The rocks of the South Singhbhum, Keonjhar and Sundergarh have rugged topography. The beds of Banded Hematite Jasper form prominent ridges rising to about 760 meter to 915 meter in altitude. The lower ground is occupied by phyllite, shale and lavas. The entire succession of rocks is folded into a series of asymmetrical or slightly overturned anticline and syncline. The strike direction is NNE-SSW and dipping towards west. The rocks show syncline structure with an over folded western limb in which occur the most important iron ore deposit of Keonjhar. The Banded Hematite Jasper consists of alternating bands of jasper or chalcedony and hematite containing varying proportions of iron oxide and silica. They are very hard and compact and stand as prominent ridges. On weathered surfaces (during the leaching out of silica) the hematite bands often stand up while the jasper bands form depressions. The bands vary in colour from brown to red in Jasper while grey to steel grey in the case of iron band. The maximum thickness of the Hematite- Jasper formation is about 915 meter in Bonai and about 305 meter in the main iron ore range on the border of Keonjhar and Sundergarh.

The iron ore derived from the Hematite Jasper is of different physical forms i.e. massive, laminated and powdery.

The massive ore exposed at the surface are dark brown to steel grey and have a specific gravity of about 5 and contains 60 to 70% Fe.

In laminated ore, the bedding planes are well seen but there may be small open spaces between the laminae. These open spaces may be partly or wholly filled with powdery ore or more often by shaly substance. The ore is mainly porous but compact variety is also observed in abundance. The laminated ore is supposed to be formed by leaching out of silica from banded hematite jasper and filling by iron.

Shaly ore has foliated structure with iron content of about 50%. This might have been formed by enrichment of shales of iron ore group of rocks by infiltration of iron bearing solution.

Powdery ore occurs in the form of lenses and large pocket deposits. It is slightly disturbed by folding activities and sometimes shows bedding with small turbidity. It is dark blue-grey to black in colour and consists mainly of hematite with some quantity of martite. It contains 66-69% Fe with slightly higher alumina content than hard lumpy ore.

A report from M/S Rungta Iron Ore Mines Limited, Chaibasa, (Personal communications) shows boreholes drilled by various agencies working independently have shown that the hard massive rocks were largely confined to the surface but may extend to a depth of 12 to 25 meters. Compact laminated ore may extend to various depths from the surface. They often contain intercalation and masses of un-replaced hematite Jasper and powdery ore. This may indicate that while the ore near the surface has been completely leached of its silica and alumina with the consequent filling of all the pore spaces by the ore, there are still unfilled spaces left between the layers at depth. The banded iron ore formation developed in the upper Pre-Cambrian period is very common in different parts of the world. Similar formation has not been found to any appreciable extent in the Cambrian and later period. They are generally considered as marine deposits formed by rhythmic precipitation of alternating layers of colloidal silica and ferric hydroxide and in some cases iron carbonate and iron silicate. High content of carbon dioxide, high humidity and temperature prevailing in Pre-Cambrian atmosphere must have helped in leaching away of silica and iron from the rocks exposed at that time. Silica and iron form by submarine volcanism also contributed to this process.

2.6. Local Geology of the Ghatkuri Iron Ore Deposits:

A Ghatkuri Iron Ore deposit is the part of Banded Iron Formation (BHJ/BHQ). It faces various phases of deformational events and creates folding pattern. The rock has weather resistant property (hard and compact). Therefore it is difficult to establish the exact succession of the litho units. The assumed succession of the area is as follows:

Abbildung in dieser Leseprobe nicht enthalten

Source: M/s Rungta Iron Ore Mines Limited; Chaibasa (Personal communications)

The ridges consist mainly of BHJ capped by iron ore and finally by laterite. The plain area made up of phyllites/shales. It is generally yellowish to buff coloured. Blue dust is exposed along the cutting of stream. Structural variation on dip direction and dip amount is a block indicative of synclinal fold.

On the basis of the prominent stream which seems to run along a fault plane, the lease r s v nto two blo ks n m ly “A” Blo k (t sout rn s o t str m) n “B” Blo k (t nort rn s o t str m). “B” Blo k s n sub v nto J m H s n “C” Blo k. “B” Blo k s ms to b the down thrown side of the fault and seems to go down by about 50 meters. As a result of this faulting, the phyllitic rock is xpos t t bottom o t “A” Blo k.

In “A” Blo k, t t top o t ll, s l s ov rl n by BHJ. Abov BHJ 4 to 5 m t rs, thick laterite capping is noticed which forms the hill top. The iron ore in this area is m nly sso t w t l t r t . At t nort rn p rt o “A” Blo k, blu ust s not extending over a large area.

In “B” Blo k, t l t olo y n s bruptly rom t t o “A” Blo k n t n t l n of division to be the fault plane. In the Jamda-Hesa area, the top of the area is occupied by BHJ of about 6 to 8 meters thickness. This hard BHJ is underlain by laminated iron ore. At many places (as evident from the quarry faces) the laminated and hard compact ore is found to contain large pocket of blue dust. The iron ore occurring at the top of “B” Blo k s omp r t v ly b tt r n qu l ty n omp r son to t or o urr n t “C” Block where it is associated with laterite.

Table 2.2: Annual Production of Run of Mines in Ghatkuri Iron Ore Mines

Abbildung in dieser Leseprobe nicht enthalten

Source: M/s Rungta Iron Ore Mines Limited; Chaibasa (Personal communications).

Table 2.3: Grade wise Annual Production in Lumps and Fines

Abbildung in dieser Leseprobe nicht enthalten

Source: M/S Rungta Iron Ore Mines Limited; Chaibasa (Personal communications).

Abbildung in dieser Leseprobe nicht enthalten

Fig. 2.1: Generalised Geological Map (Mondal, 2009)

Abbildung in dieser Leseprobe nicht enthalten

CHAPTER - 3

CHARACTERISATION OF ORE

3.1. Introduction

Mineral characterisation involves the study of minerals/ore in terms of their size, shape, chemical composition, morphology, textural position, association and other attributes. In recent years the demand for raw materials is increasing rapidly whereas the reserve of high grade ores is getting depleted considerably. To meet future challenges of raw ore requirements focus has been given to the low grade ore. Characterisation of the ore in a comprehensive manner with the aid of micro analytical tools gives much more information than has been possible in the past. It not only helps in preserving the reserve of high grade ore but gives crucial information required for optimising appropriate process parameters for the beneficiation of the ore. Mineral characterisation thus optimises the mineral processing cost, saves time and energy and so helps in maximising profit. Presently, millions of tons of BHJ, BHQ have been stockpiled in or around the site, where iron ore is mined. They have not been properly utilized till date due to the high energy consumption and the lack of cost-effective parameters. In the current investigation, a scientific approach has been adopted to explore the suitability of BHJ as a substitute for the high grade ore. In this investigation, physical, mechanical and metallurgical characteristics of Banded Hematite Jasper have been studied in detail.

3.2. Literature study

Roy et al. (2007) studied characterisation behaviour of Jilling Area of eastern India using transmitted and reflected light microscopy, SEM-EDS, XRD and XRF with a view to testing the amenability of the ore for beneficiation. Roy and Venkatesh (2009) discussed the geological complexities of banded iron formation (BIF) and associated iron ores of Jilling-Langalata iron ore deposits belonging to Iron-Ore-Group (IOG) eastern India. They also studied the geochemical evaluation of different iron ores. The geochemical and mineralogical characterisation suggests that the massive, hard laminated, soft laminated ore and the blue dust had a genetic lineage from Banded Iron Formations aided with certain input from hydrothermal activity. Upadhyay et al. (2009) studied the geological aspects (mineralogy and ore genesis) of Noamundi (Singhbhum), Joda and Khondbond (Keonjhar, Orissa) to examine the suitable beneficiation methods. He used four specific types of ores i.e. massive hard ore, laminated hard ore, fine powdery ore and blue dust ore. Observations indicate that the above ores do not require complex processing. Again, Upadhyay et al. (2010) studied the various aspects of ore characterisation such as chemical analysis, ore and mineral petrography, XRD analysis, SEM and electron probe micro analysis (EPMA) of Joda and Khondbond region. The ore chemistry indicates that the massive hard ores and the blue dust have high iron, low alumina and phosphorus contents. As the ore becomes higher in quality, they do not require any specialised beneficiation technique for up- gradation. Rao et al. (2009) studied the role of geochemical and mineralogical characterisation using microscope, TG, XRD and EPMA of Bellary-Hospet sector of Karnataka. They found that Quartz and Hematite were major phases while clay minerals like (gibbsite and kaolinite) and goethite were the minor phases. They observed under microscope the presence of pyrite and absence of iron silicate and iron carbonate. hey found evidence of. Roy et al. (2008) also made a comparison between the two important Precambrian Iron ore deposits of India and Krivoy Rog province of the central Ukrainian Shield. They observed that the Jilling-Langalata deposits contained considerable amounts of blue dust that is absent in the Chitradurga deposits. The Indian iron ores are relatively richer in iron and contains higher amounts of alumina and phosphorus compared with those of the Krivoy Rog deposits. The Indian iron ore samples contain porous and friable oxides and hydroxides of iron along with kaolinite, gibbsite and quartz. In contrast, the ores from Krivoy Rog are massive with negligible clay and a higher quartz content leading to very low alumina and very high silica contents in the ores and slimes. Nayak (2014) characterised the low grade iron ore from Barsua iron ore deposits. In her studies, she found that the sample contained huge quantity of partially weathered goethite and interlocked hematite. She also observed the presence of gibbsite and kaolinite as a gangue mineral in different proportions. She finally concluded on the basis of mineralogical studies that the final concentrate product quality depended upon the presence of goethite. Das et al. (2010) focussed on mineralogy, texture and chemical composition of the iron ore (Goethite) from Joda- Barbil region of the Jamda-Koira valley. The iron ore samples have been investigated by optical microscopy, EPMA, XRD, and TG-DTA. The optical microscopy studies have indicated three dominant textural types of goethite, such as (a) colloform-banded vitreous, (b) massive vitreous, and (c) earthy or ochreous goethite. The vitreous goethite is hard and crystalline, whereas ochreous goethite is clayey and consists of ultrafine crystallites often intimately admixed with kaolinite and gibbsite. EPMA studies indicated that (a) ochreous and colloform-banded goethite contain more alumina compared to massive vitreous goethite and (b) colloform-banded goethite has higher phosphorus contents (P2O5: 0.90–2.25%). Krishna et al. (2013) studied a few process characterisations of some Indian ion ores. They dealt with the tentative ascending order of process refractoriness of iron ores is massive hematite/magnetite < marine black iron oxide sands < laminated soft friable siliceous ore fines < massive banded magnetite quartzite < laminated soft friable clayey aluminous ore fines < massive banded hematite quartzite/jasper < massive clayey hydrated iron oxide ore < manganese bearing iron ores massive < Ti–V bearing magnetite magmatic ore < ferruginous cherty quartzite. Based on diagnostic process characterization, the ores have been classified and generic process has been adopted for some Indian iron ores. Mohanty et al. (2012) gave a deep insight into the different mineralogical attributes, various characterisation studies megascopic, microscopic (both optical & electron), XRD, mossbauer and Vibrating Sample Magnetometer to determine out the most effective way of utilization, of the Banded Iron Ores of Orissa area. Behera et al. (2010) made an attempt to explore alternative uses of goethite rich iron ore. They inferred that substantial amount of goethite was present in the iron ore, using various characterisation techniques such as optical microscopy and XRD. On heating in air, the goethite content was completely converted into hematite at 400 °C. Mohapatra et al. (2010) investigated the bog manganese ore associated with BIF in Iron Ore Group. They characterised the ore, studying the physical, optical and chemical properties. Physically the ore was powdery, fine-grained, blackish to brown in colour, very soft and soiled the finger. Mineralogically, the ore consisted of two phases and the ore contained around 23% Mn and 28% Fe and 7% of combined alumina and silica. They concluded that the ore was supposed to be of low grade and did not respond to any sort of physical beneficiation. They emphasized silica content could be reduced through simple size reduction. Gurulaxmi et al. (2010) characterized the BHJ with a view to recover iron values. They used size wise chemical assay of the iron and silica content, mineralogical studies and textural alignment of the ore. The ore contained 40% Fe (T) with 41% silica. Mineralogical studies revealed hematite and quartz were the major phases and texturally showed complex intergrowth. Kumar et al. (2010) focussed on the characterisation and beneficiation of high alumina iron ores from Noamundi Mines of Jharkhand, where environmental friendly methods will be studied for their sustainable exploitation. They studied on low grade iron ores from selected deposits using microscopy, petrography and ore mineral characterisation. They observed that ores of the area basically consisted of hematite (two generations), goethite (two generations) and limonitic materials (younger generation) in association with major gangue minerals such as clay minerals (Kaolinite, Gibbsite), cryptocrystalline silica (Jasper, Chert) and crystalline quartz and apatite. Mohapatra et al. (2017) using mineralogy, petrography and micro-chemical characteristics studied on the enclaves of mylonitic Banded Iron Formations within Sukinda Ultramafic Complex. They observed that rocks were fine grained, weathered and limonitised; containing quartz, magnetite, hematite, martite and goethite. They also noticed the rare presence of banding and lamination but largely exhibited mylonitic fabric. Electron Probe Micro Analysis of iron-rich phase in Mylonitic Magnetite Quartzite indicates the enrichment of Ni, Mg and Cr in the magnetite phase of MMQ. Kumar and Mandre (2015) carried out mineralogical studies on the iron ore tailings. They observed that hematite and goethite were major iron bearing mineral phases while quartz and kaolinite was major gangue minerals. Chokshi et al. (2015) studied the mineralogical aspects of the Low-Grade Iron Ore (BIF) from Jharkhand–Orissa Region, India, using X-ray fluorescence spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive analytical X-ray and optical microscopy techniques. The main aim of the study was to document the morphology, texture, phase identification and properties of iron ore. Mineralogical study revealed that hematite, goethite, quartz, kaolinite and Al–Fe siliceous phases were present. Microscopic observation showed hematite phases were interlocked by fine gangue grains, and also they were covered by gangue grains on finer scale. Most of the hematite grains were highly altered and the mineral alteration zones were clearly visible. In SEM analysis, cavities were observed which contained the weathered products such as goethite and kaolinite. By EDX analysis, phases were spot analyzed and elemental information was collected. From mineralogical and characterization analyses, it may be observed that the liberation of the ore minerals from the gangue minerals is difficult. It is suggested that a washing treatment be employed after each mineral dressing operation. In this process quartz and clay minerals separate progressively. Mohapatra et al. (2007) discuss the Goethite morphology and composition in Banded Iron Formation. They observed that Goethite was reported to occur as a ubiquitous phase in many iron ore types and is particularly abundant in BIF of Precambrian. Study using electron microscopy indicated several goethite morphotypes i.e. botryoidal, nodular, spheroidal, platy stalactitic and flaky. These different morphotypes display intergranular, intragranular, wedge, reniform, comb, prismatic, cavity-line and bead microstructures. EPMA indicated wide variation in different morphotypes and microstructures. Goethite replacing hematite is generally devoid of deleterious elements while re-precipitated goethite generally contained adsorbed alumina, silica and or phosphorus. Rath et al. (2010) studied on the low grade iron ore (lumps+fines) from eastern India for the suitability of sinter and pellet feed. They observed that the sample contained more or less hematitic grains and considerable amount of goethitic and limoniic materials. They found that quartz and clay were present as impurities. Their studies also showed that iron bearing phases were poorly l b r t bov 300 μm. How v r, b low 300 μm t l b r t on su nly mprov r n bout 70% b low t s z r t on 250 μm n bout 80% l b ration is v b low 150 μm. Das et al. (2010) discuss the magnetic and flotation studies of banded hematite quartzite ore for the production of pellet grade concentrate. They focus on the intergrowth pattern of the silica and hematite grains. They observe that hematite and quartz grains are interlocked up to very fine size. The impurities in this sample are silicate minerals, which are associated as hard banded form with iron. They conclude that on account of the fine liberation and texture of the ore, it is essential to grind the sample to a very fine size for effective liberation of both iron and silica particles. Anupam et al. (2010) emphasize that both the ores require fine grinding to a size of 200 mesh to achieve effective liberation. Rachappa et al. (2015) discuss the difficulty of processing and utilisation of the low grade iron ore. They realised that these difficulties arose due to their mineralogical characteristics, soft nature of the ores and high silica content. They used X-Ray Diffraction and liberation point counting technique. Roy and Das (2008) characterized the low-grade iron ore slime from Jilling Langalota deposit, India. They used the size analysis, chemical analysis, x-ray diffraction (XRD), scanning electron microscopy (SEM) with EDAX (Energy Dispersive Analysis by X-ray), image analysis, microscopic studies, and heavy liquid separation studies and observed that the data indicated that a substantial amount of the sample was below 20 mm in size. The finer fraction contained larger amount of gangue while the coarser fraction was richer in iron. Roy et al. (2007) studied the low grade iron ore slime from Chitradurga, India. Their study using the different advanced aspects of characterisation found that the bulk ore was found very low grade containing porous and friable oxide and hydroxide of iron along with kaolinite and quartz. The nature and texture of the ore is believed to be mainly responsible for the formation of slime during mining, processing, and handling of ores. The occurrence of kaolinite along the cavities and weaker mineral plane renders the ore highly fragile and causes high alumina content in the slime. The present study established the excellent rejection of silica and alumina.

3.3. Materials and Method

3.3.1. Materials

Raw Materials

About 500 kg of Banded Hematite Jasper samples were collected from the selected study area through open pits along and across the strike of the bedding plane. The samples were picked up according to the variation in the physical appearance (i.e. on the basis of the thickness of the bands (macro and micro), packed and labelled and finally transported to the laboratory. These samples were primarily washed through the spray of clean water in order to eliminate any contamination. Washing helps in removing adhered aluminosilicate particle also. The study area was located in Survey of India toposheet number E45H8 (73 F/8) in between latitude 22°20‟ N – 22°40‟ N n longitude between 85°22 – 85°50 near Ghatkuri (Gua), West Singhbhum, Jharkhand; which comes under Singhbhum-Orissa Iron-Ore-Series of Precambrian Supracrustal Basement famous for world class iron ore deposits. It hosts almost all varieties of iron ore from fine-grained powdery ore (fines and slimes) to hard lumpy ore and laminated Banded Hematite Jasper and Banded Hematite Quartzite. Banded Iron Formation (BIF) is an important volcano-sedimentary rock association of Iron Ore Group. It includes BIF, laterites, shale (micro-bands) and some goethite rock materials in the form of high stratified deposits. These are capable of high resistance to weathering and resemble a topographical feature in the form of hillocks.

3.3.2. Methods

This study include physical characteristics, qualitative and quantitative evaluation by polished thick sections in Image Analyser, microscopic study of a thin section in an optical microscope having transmitted and reflected light facilities, Bond Work Index analysis, Vickers Hardness Test, Grain size analysis, chemical analysis, SEM-EDX, XRD, liberation analysis, Devies tube test and Sink and Float analysis.

3.3.2.1. Physical Characterisation

3.3.2.1a. Ore Microscopy (Reflected light microscopy)

Polished section of the Banded Hematite Jasper was made using diamond wheel rock cutting machine and its subsequent polishing using corborundum powder of different micron sizes (from 60,80,100,150,200 and 240). At the final stage, it was polished using diamond paste (6-OS-375) and Hiffin Fluid (OS) in high speed cloth polishing machine, and finally subjected to high-resolution microscopy (LEICA-BM-6000™).

3.3.2.1 b. Petrography (transmitted light microscopy)

A piece of thin lamellae of Banded Hematite Jasper was cut using diamond wheel rock cutting machine. It was ground till levelled on both sides of the surface by different micron size (from 60 to 240) carborundum powder. It was glued on (25x50mm) glass slab using Canada-Balsum ground and later polished till achieving the first order gray interference colour.

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