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UPSC MainsGEOGRAPHY-PAPER-II201920 Marks
Q25.

Discuss distribution, mode of occurrence, mineralogy and genesis of Precambrian Iron ore deposits of India.

How to Approach

This question requires a detailed understanding of Precambrian iron ore deposits in India. The answer should be structured around distribution (major belts), mode of occurrence (geological settings), mineralogy (types of iron ores), and genesis (formation processes). A geographical approach, linking these aspects, is crucial. Focus on the key formations like the Banded Iron Formations (BIFs) and their geological context. Include specific locations and examples to illustrate the points.

Model Answer

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Introduction

India possesses substantial reserves of iron ore, a crucial raw material for the steel industry. A significant portion of these reserves occurs in Precambrian formations, representing some of the oldest and largest iron ore deposits globally. These deposits, primarily Banded Iron Formations (BIFs), formed during the Archean and Proterozoic eons under unique geochemical conditions. Understanding their distribution, mode of occurrence, mineralogy, and genesis is vital for resource management and geological research. The exploitation of these deposits has played a pivotal role in India’s industrial development, and continued exploration is essential to meet future demands.

Distribution of Precambrian Iron Ore Deposits in India

The Precambrian iron ore deposits of India are concentrated in four major geological belts:

  • Eastern India (Odisha-Jharkhand Belt): This is the most important iron ore producing region, accounting for over 80% of India’s total reserves. Key locations include:
    • Badampahar, Bonai, Keonjhar (Odisha): Characterized by high-grade hematite ores.
    • Kiriburu, Meghahatuburu (Jharkhand): Known for magnetite ores.
  • Central India (Madhya Pradesh-Maharashtra Belt): Deposits are found in the Balaghat, Jabalpur, and Chandrapur districts. These are generally lower grade compared to eastern India.
  • Southern India (Karnataka-Andhra Pradesh-Tamil Nadu Belt): The Kudremukh iron ore deposit in Karnataka is a significant example. Also found in Bellary-Hospet range (Karnataka) and Anantapur district (Andhra Pradesh).
  • North-Eastern India (Assam): Smaller deposits are found in the Lohit and Tirap districts.

Mode of Occurrence

Precambrian iron ore deposits in India predominantly occur as:

  • Banded Iron Formations (BIFs): These are the most common mode of occurrence. BIFs are sedimentary rocks consisting of alternating layers of iron oxides (hematite, magnetite, goethite) and chert (silica). They formed in shallow marine environments during the Archean and Proterozoic eons.
  • Hematite-Quartzite Deposits: These are formed by the alteration of BIFs through weathering and metamorphism.
  • Magnetite-Taconite Deposits: These are fine-grained, iron-rich sedimentary rocks containing magnetite.
  • Iron Ore Placer Deposits: Less common, these are formed by the concentration of heavy iron minerals in alluvial deposits.

Mineralogy

The mineralogy of Precambrian iron ore deposits in India is diverse, but the following are the most common iron-bearing minerals:

  • Hematite (Fe2O3): The most abundant iron ore mineral, often found in massive or disseminated form.
  • Magnetite (Fe3O4): A strongly magnetic iron oxide, commonly associated with BIFs.
  • Goethite (FeO(OH)): A hydrated iron oxide, formed by the weathering of hematite and magnetite.
  • Limonite (FeO(OH)·nH2O): A mixture of hydrated iron oxides, often found in surface zones.
  • Siderite (FeCO3): An iron carbonate mineral, less common but present in some deposits.
  • Chert (SiO2): A microcrystalline form of silica, intimately associated with BIFs.

Genesis of Precambrian Iron Ore Deposits

The genesis of Precambrian iron ore deposits is a complex process, but the prevailing theory involves the following stages:

  • Source of Iron: Iron was likely derived from hydrothermal vents and volcanic activity in the Archean oceans.
  • Transport of Iron: Iron was transported in solution as ferrous iron (Fe2+) in anoxic (oxygen-deficient) marine environments.
  • Precipitation of Iron: The precipitation of iron oxides was triggered by several factors, including:
    • Increase in Oxygen Levels: The Great Oxidation Event (around 2.4 billion years ago) led to the oxidation of ferrous iron to ferric iron (Fe3+), which precipitated as iron oxides.
    • Biological Activity: Photosynthetic bacteria played a role in oxygen production and iron precipitation.
    • Changes in pH and Redox Potential: Fluctuations in these parameters also influenced iron precipitation.
  • Formation of BIFs: Alternating layers of iron oxides and chert were deposited over long periods, forming BIFs.
  • Subsequent Alteration: Metamorphism, weathering, and hydrothermal alteration modified the original BIFs, leading to the formation of hematite-quartzite and other iron ore deposits.

The genesis is also linked to the evolution of Earth’s atmosphere and oceans. The initial anoxic conditions allowed for the transport of dissolved iron, while the subsequent oxygenation of the atmosphere led to its precipitation and the formation of massive iron ore deposits.

Conclusion

The Precambrian iron ore deposits of India represent a significant geological and economic resource. Their distribution is concentrated in specific geological belts, and their formation is linked to the unique geochemical conditions of the Archean and Proterozoic eons. Understanding the mode of occurrence, mineralogy, and genesis of these deposits is crucial for sustainable resource management and future exploration. Continued research and technological advancements are needed to optimize extraction processes and minimize environmental impacts.

Answer Length

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Additional Resources

Key Definitions

Archean Eon
The earliest eon of Earth's history, from approximately 4.0 to 2.5 billion years ago, during which the first continents formed and the conditions for the formation of BIFs were established.

Key Statistics

As of 2021, India holds approximately 31.85 billion tonnes of iron ore reserves, with about 94% being hematite. (Source: National Mineral Inventory, Controller General of Indian Geology)

Source: National Mineral Inventory, Controller General of Indian Geology (2021)

Odisha accounts for over 55% of India’s total iron ore production as of 2022-23. (Source: Ministry of Mines, Annual Report)

Source: Ministry of Mines, Annual Report (2022-23)

Examples

Kudremukh Iron Ore Deposit

Located in Karnataka, Kudremukh is a significant magnetite deposit associated with BIFs. It was a major producer of iron ore until its closure in 2006 due to environmental concerns, highlighting the need for sustainable mining practices.

Frequently Asked Questions

▶What is the significance of the Great Oxidation Event in the formation of Precambrian iron ore deposits?

The Great Oxidation Event, a period of significant increase in atmospheric oxygen around 2.4 billion years ago, played a crucial role in precipitating dissolved iron from the oceans, leading to the formation of massive BIFs.

Topics Covered

GeologyEconomic GeologyOre DepositsIron FormationOre GenesisIndian Geology
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