Model Answer
0 min readIntroduction
The Palaeozoic Era witnessed significant tectonic and magmatic activity across the globe, and India was no exception. During this period, India was part of the Gondwana supercontinent and experienced various phases of rifting, volcanism, and plutonism. Igneous activities during this time are crucial for understanding the geological evolution of the Indian subcontinent and are intimately linked to the formation of important mineral deposits. The igneous rocks formed during the Palaeozoic provide valuable insights into the mantle processes and crustal evolution of the region. This answer will detail the major igneous events across different regions of India during the Palaeozoic.
Igneous Activities in India during the Palaeozoic Times
1. The Extra-Peninsular Region (Himalayan Belt & Surrounding Areas)
The Palaeozoic igneous activity in this region is primarily associated with the closing of the Paleo-Tethys Ocean and subsequent collision events.
- Early Palaeozoic (Cambrian-Ordovician): Limited igneous activity, mainly represented by granitic intrusions in the Lesser Himalayas. These intrusions are associated with subduction-related magmatism.
- Mid-Palaeozoic (Silurian-Devonian): Increased volcanic activity, particularly in the form of island arc volcanism related to the ongoing subduction. Andesitic and basaltic lava flows and associated dykes and sills are found in the Kumaon Himalayas.
- Late Palaeozoic (Carboniferous-Permian): Extensive granitic intrusions and associated pegmatites occurred, marking the final stages of the collision and crustal thickening. These granites are often rich in tin and tungsten mineralization.
2. The Peninsular India (Gondwana Crust)
Peninsular India, forming the core of the Gondwana landmass, experienced a different style of igneous activity during the Palaeozoic.
- Early to Mid-Palaeozoic (Cambrian-Devonian): Dolerite dykes and sills are common, particularly in the Vindhyan and Cuddapah basins. These are believed to be related to mantle plume activity and continental rifting. The Malani igneous suite of Rajasthan, a large-scale felsic volcanic province, is a significant feature of this period. It consists of rhyolites, granites, and associated volcanic rocks.
- Late Palaeozoic (Carboniferous-Permian): Extensive basaltic lava flows, known as the Deccan Traps precursors, covered large areas of the Gondwana basins. These basalts are associated with the breakup of Gondwana and the initiation of rifting. Granitic intrusions also occurred in the Southern Granulite Terrain (SGT) of Tamil Nadu and Kerala, linked to crustal melting during rifting.
3. Gondwana Basins (Pranhita-Godavari, Talchir, Raniganj)
These basins, representing rift valleys within the Gondwana crust, hosted significant igneous activity.
- Permian-Triassic: Basaltic lava flows and dolerite intrusions are prevalent in these basins, often interbedded with coal and sedimentary rocks. These igneous rocks are associated with the initial stages of the Gondwana breakup and the formation of rift valleys. The basaltic flows are often vesicular and contain amygdules filled with secondary minerals.
4. Regional Variations and Rock Types
The types of igneous rocks formed varied regionally, reflecting the different tectonic settings.
| Region | Dominant Igneous Rocks | Tectonic Setting |
|---|---|---|
| Himalayas | Granites, Andesites, Basalts | Subduction, Island Arc Volcanism, Collision |
| Rajasthan (Malani Suite) | Rhyolites, Granites | Continental Rifting, Mantle Plume |
| Gondwana Basins | Basalts, Dolerites | Continental Rifting, Breakup of Gondwana |
| Southern Granulite Terrain | Granites | Crustal Melting during Rifting |
5. Associated Mineralization
The Palaeozoic igneous activity is associated with several important mineral deposits.
- Tin and Tungsten: Associated with granitic intrusions in the Himalayas and Southern India.
- Base Metals (Lead, Zinc, Copper): Found in volcanogenic massive sulfide (VMS) deposits associated with island arc volcanism in the Himalayas.
- Iron Ore: Banded Iron Formations (BIFs) are often associated with basaltic lava flows in the Gondwana basins.
- Diamondiferous Kimberlites: Although primarily known from later periods, some kimberlite intrusions may have roots in the Palaeozoic mantle.
Conclusion
The Palaeozoic igneous activities in India were diverse and complex, reflecting the dynamic tectonic environment of the time. From subduction-related volcanism in the Himalayas to continental rifting and mantle plume activity in Peninsular India, these events played a crucial role in shaping the geological landscape and forming valuable mineral resources. Further research, including detailed geochronological and geochemical studies, is essential to refine our understanding of the Palaeozoic igneous history of India and its implications for the evolution of the Indian subcontinent.
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