Ladakh Magmatic Arc

Ladakh Magmatic Arc Latest News

Recently, scientists have traced the evolution of the Ladakh Magmatic Arc (LMA) in North West Himalaya.

About Ladakh Magmatic Arc

• It is a belt of igneous rocks in the Trans-Himalaya formed in the period Jurassic to Eocene– 201.3 million years ago to 33.9 Million Year (Ma).
• The LMA is a long-extinct volcanic system evolved through three major phases of geological activity over tens of millions of years.
  • 160–110 million years ago: Early island arc formation
  • 103–45 million years ago: Intensified magmatism during plate convergence
  • Less than 45 million years ago: Post-collisional magmatic activity

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Process of Formation of Ladakh Magmatic Arc

• 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 of Ladakh Magmatic Arc

• 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.
• 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

Source: PIB