Model Answer
0 min readIntroduction
Chromite (FeCr₂O₄) is a primary ore of chromium, a strategically important metal used in alloy steel production, refractory materials, and chemical industries. India possesses significant chromite reserves, largely concentrated within the Precambrian rocks of the Indian Shield. These deposits are genetically linked to ultramafic and mafic intrusions and associated stratiform sequences. Understanding the geological characteristics of these deposits is crucial for resource assessment and sustainable exploitation. The Indian Shield, comprising Archaean and Proterozoic terrains, provides a diverse geological setting for chromite mineralization, with varying degrees of alteration and enrichment.
Geological Characteristics of Chromite Deposits in the Indian Shield
1. Odisha Chromite Province (Sukinda Valley & Associated Areas)
The Sukinda Valley in Odisha is the most prominent chromite-producing region in India, accounting for over 90% of the country’s reserves. The deposits are hosted within ultramafic rocks (dunite, peridotite, chromitite) of the Mahanadi Group (Early Proterozoic). These ultramafic bodies are emplaced within banded iron formations (BIFs) and associated sedimentary sequences. The chromitite layers occur as stratiform bodies, lenses, and podiform masses. The ore is generally massive, granular, and exhibits varying degrees of alteration (serpentinization, talc alteration). The Sukinda chromites are characterized by high Cr/Fe ratio and relatively low levels of deleterious elements like Ni and Co. Associated minerals include olivine, pyroxene, and magnetite.
2. Eastern Ghats Province (Vizianagaram, Srikakulam Districts, Andhra Pradesh)
Chromite occurrences in the Eastern Ghats are associated with Proterozoic ultramafic intrusions and layered mafic-ultramafic complexes. The deposits are typically podiform and disseminated within peridotites and dunites. The chromitite layers are often conformable to the host rock’s foliation. Alteration is common, with serpentinization being the dominant process. The chromite grains are often intergrown with olivine and pyroxene. The grade of chromite varies, with some occurrences exhibiting relatively low Cr₂O₃ content. The geological setting suggests a magmatic origin, with chromite crystallizing from mantle-derived melts.
3. Maharashtra-Madhya Pradesh Belt (Sausar, Balaghat, Chhindwara)
This belt hosts significant chromite deposits within Proterozoic ultramafic intrusions emplaced within the Gondwana sediments. The deposits are typically stratiform and occur as lenses and bands within peridotites and dunites. The chromitite layers are often associated with banded iron formations. Alteration is prevalent, with serpentinization and talc alteration being common. The chromite grains are often euhedral to subhedral and exhibit varying degrees of oxidation. The deposits are characterized by moderate to high Cr₂O₃ content. The Sausar group is particularly known for its chromite mineralization.
4. Karnataka (Hospet, Sandur)
Chromite deposits in Karnataka are found within Proterozoic ultramafic intrusions associated with banded iron formations. The deposits are generally podiform and disseminated within peridotites and dunites. The chromitite layers are often conformable to the host rock’s foliation. Alteration is common, with serpentinization being the dominant process. The chromite grains are often intergrown with olivine and pyroxene. The grade of chromite varies, and the deposits are often smaller in size compared to those in Odisha.
5. Tamil Nadu (Coimbatore, Salem)
Chromite occurrences in Tamil Nadu are associated with Proterozoic ultramafic intrusions within the Southern Granulite Terrain. The deposits are typically podiform and disseminated within peridotites and dunites. The chromitite layers are often conformable to the host rock’s foliation. Alteration is common, with serpentinization being the dominant process. The chromite grains are often intergrown with olivine and pyroxene. The deposits are generally smaller in size and lower in grade compared to those in Odisha.
| Region | Host Rock | Deposit Type | Alteration | Cr₂O₃ Content |
|---|---|---|---|---|
| Odisha | Dunite, Peridotite | Stratiform, Podiform | Serpentinization, Talc | High (40-55%) |
| Eastern Ghats | Peridotite, Dunite | Podiform, Disseminated | Serpentinization | Moderate (30-45%) |
| Maharashtra-MP | Peridotite, Dunite | Stratiform | Serpentinization, Talc | Moderate to High (35-50%) |
Conclusion
The chromite deposits of the Indian Shield exhibit diverse geological characteristics, reflecting their varied tectonic settings and magmatic histories. The Odisha province remains the dominant source of chromite in India, owing to its large reserves and high-grade mineralization. Understanding the geological controls on chromite mineralization is crucial for future exploration and sustainable resource management. Further research focusing on the petrogenesis of the host magmas and the alteration processes affecting the chromite ore is essential for optimizing extraction techniques and minimizing environmental impacts.
Answer Length
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