In News:

Recent scientific studies have traced the evolution of the Ladakh Magmatic Arc (LMA) in the north-western Himalaya, providing new insights into the geological history of the Indian subcontinent and plate tectonic processes.

About Ladakh Magmatic Arc (LMA)

• The Ladakh Magmatic Arc is a belt of igneous rocks located in the Trans-Himalayan region. It represents a long-extinct volcanic arc system formed due to tectonic activity associated with the closure of the Neo-Tethys Ocean.
• Time Period: Formed between the Jurassic and Eocene periods (~201 million years ago to ~34 million years ago)

Geological Formation Process

Role of Plate Tectonics

• The region was once part of the Neo-Tethys Ocean.
• The Indian Plate moved northwards and subducted beneath the Eurasian Plate.
• This subduction led to melting in the mantle, generating magma.
• The rising magma formed a chain of volcanic features, giving rise to the magmatic arc.

Phases of Evolution of LMA

1. Early Island Arc Formation (160–110 Ma)

• Ladakh initially resembled a chain of volcanic islands.
• Represented by the Dras–Nidar Island Arc Complex (DNIAC).
• Magma was primarily derived from the mantle, with minimal sediment contribution.

2. Crustal Enrichment & Batholith Formation (103–45 Ma)

• Occurred during intensified convergence between the Indian and Eurasian plates.
• Formation of large granitic bodies known as the Ladakh Batholith.
• Increased contribution from:
  • Continental crust
  • Subducted sediments
• Indicates magma mixing and deep crustal processes.
• This phase coincided with the approaching continental collision.

3. Post-Collisional Magmatism (<45 Ma)

• Continued tectonic activity even after the closure of the Neo-Tethys Ocean.
• Formation of mafic dykes (vertical intrusions of magma).
• Magma sourced from an enriched mantle.
• Suggests lingering magmatic activity post-collision.

Key Geological Features

• Ladakh Batholith: Large granitic intrusions indicating crustal melting.
• Mafic Dykes: Evidence of late-stage magmatic activity.
• DNIAC: Represents early volcanic island arc phase.