Model Answer
0 min readIntroduction
The Singhbhum Shear Zone (SSZ) is a Proterozoic crustal-scale deformation zone extending for over 250 km across the eastern Indian shield, encompassing parts of Jharkhand and West Bengal. It represents a major boundary between the Chotanagpur Granite Gneiss Terrane and the Ganganagar Terrane. This zone isn’t merely a structural feature; it’s a highly prospective geological terrain, renowned for its significant mineralization of iron ore, copper, uranium, gold, and other valuable metals. The SSZ’s unique geological history and structural characteristics have played a pivotal role in the formation and concentration of these ore deposits, making it a crucial area for economic geological studies and exploration.
Geological Setting of the Singhbhum Shear Zone
The SSZ originated during the Archean-Proterozoic transition (around 3.5-3.0 Ga) and experienced multiple phases of deformation, metamorphism, and fluid flow. It’s characterized by:
- Shear Fabrics: Intense shearing and mylonitization, creating zones of weakness and permeability.
- Lithological Variations: A complex assemblage of rocks including granite-gneiss, metasedimentary rocks (iron formations, quartzites, shales), and mafic-ultramafic intrusions.
- Structural Features: Presence of faults, folds, and shear bands, providing pathways for fluid migration.
- Metamorphic Grade: Variable metamorphic grades, influencing the stability of ore minerals.
Role of the SSZ as a Guide to Mineralization
The SSZ acts as a guide to mineralization through several key mechanisms:
1. Fluid Flow and Hydrothermal Activity
The shear zone provides conduits for the circulation of hydrothermal fluids derived from magmatic sources, metamorphic devolatilization, and meteoric water. These fluids, often enriched in metals, react with the surrounding rocks, leading to the precipitation of ore minerals. The permeability enhanced by shearing is critical for this process.
2. Metamorphic Processes
Regional metamorphism associated with the SSZ has played a significant role in mobilizing and concentrating ore elements. For example, the formation of banded iron formations (BIFs) is closely linked to the metamorphic history of the region. Metamorphic fluids can also transport and redeposit ore minerals along shear planes.
3. Structural Trapping
Faults, folds, and shear bands within the SSZ act as structural traps, focusing ore-bearing fluids and creating localized zones of mineralization. These structures provide physical and chemical environments conducive to ore deposition.
4. Lithological Control
The specific lithologies within the SSZ influence the type and concentration of mineralization. For instance, iron formations are the primary source of iron ore, while ultramafic rocks can host nickel and chromium mineralization. The reactive nature of certain rock types with hydrothermal fluids also plays a role.
Ore-Forming Processes and Mineralization Types
The SSZ hosts a diverse range of ore deposits formed through various processes:
- Iron Ore: Banded Iron Formations (BIFs) are the most significant iron ore deposits, particularly in the Kiriburu and Meghahatuburu mines. These deposits formed through chemical precipitation from seawater during the Proterozoic era.
- Copper Mineralization: Copper mineralization is associated with hydrothermal veins and disseminations within shear zones and altered rocks. The Rakha mines are a prime example.
- Uranium Mineralization: Uranium deposits are found in association with granite-gneiss and sedimentary rocks within the SSZ, often linked to hydrothermal alteration. Jaduguda and Narwapahar are important uranium mining centers.
- Gold Mineralization: Gold occurs as free gold or in association with sulfide minerals within quartz veins and shear zones.
- Manganese Ore: Manganese mineralization is found in association with banded iron formations and sedimentary rocks.
Specific Examples of Mines within the SSZ
| Mine Name | Mineral | Location |
|---|---|---|
| Kiriburu | Iron Ore | West Singhbhum, Jharkhand |
| Meghahatuburu | Iron Ore | West Singhbhum, Jharkhand |
| Rakha | Copper | Singhbhum, Jharkhand |
| Jaduguda | Uranium | East Singhbhum, Jharkhand |
| Narwapahar | Uranium | Singhbhum, Jharkhand |
Conclusion
The Singhbhum Shear Zone stands as a testament to the intricate relationship between geological structures and ore formation. Its long and complex history of deformation, metamorphism, and fluid flow has created a highly favorable environment for the concentration of a diverse suite of economically important minerals. Continued exploration and detailed geological studies within the SSZ are crucial for unlocking its full mineral potential and contributing to India’s economic growth. Understanding the ore-forming processes within this zone also provides valuable insights into similar mineralized terrains globally.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.