Ladakh Magmatic Arc:
Scientists have traced the evolution of Ladakh Magmatic Arc (LMA) in North West Himalaya.
- Ladakh Magmatic Arc is a belt of igneous rocks in the Trans-Himalaya formed in the period Jurassic to Eocene.
- The LMA is a long-extinct volcanic system evolved through three major phases of geological activity over tens of millions of years.
- Process of Formation:
- Millions of years before the region that is now called Ladakh lay above an ocean called the Neo-Tethys Ocean.
- Below that ancient sea, giant slabs of Earth’s crust slowly plunged into the mantle in a process known as subduction leading to the formation of the Ladakh Magmatic Arc (LMA).
- Phases of Formation
- Island Arc Formation: In its earliest stage, Ladakh resembled a chain of volcanic islands rising from the Neo-Tethys Ocean.
- Represented by the Dras–Nidar Island Arc Complex (DNIAC)
- Magma primarily originated from the mantle
- Minimal contribution from subducted sediments
- Crustal Enrichment and Batholith Formation: As tectonic plates converged, the system evolved:
- Formation of large granite bodies known as the Ladakh Batholith (LB)
- Increased input from continental crust and recycled sediments
- Chemical signatures indicate deep crustal processes and magma mixing
- This phase coincides with the approaching collision between India and Eurasia.
- Island Arc Formation: In its earliest stage, Ladakh resembled a chain of volcanic islands rising from the Neo-Tethys Ocean.
- Post-Collision Magmatism: After the plates collided and the Neo-Tethys Ocean closed, tectonic activity continued:
- Formation of mafic dykes—vertical sheets of volcanic rock
- Magma derived from a previously enriched mantle source
- Indicates lingering tectonic and magmatic activity even after collision.
