Origin and serpentinization of ultramafic rocks of Manipur Ophiolite Complex in the Indo-Myanmar subduction zone, Northeast India

The Manipur Ophiolite Complex (MOC) is part of the Manipur-Nagaland ophiolite belt (MNOB). The belt is exposed in the eastern margin of the Indo-Myanmar Ranges (IMRs), which formed by the collision between the India and Myanmar continental plates. Several contrasting views were put forward concerning the origin of the MNOB. The complex represents a dismembered ophiolite sequence with serpentinite as the largest litho-unit formed. Petrography and Raman spectroscopy of the serpentinite suggest that they are serpentinized ultramafic cumulate and peridotite. The serpentinization may have occurred at a condition of low pressure and low temperature metamorphism. Geochemical signatures of the rocks and spinel grains revealed that the protolith be an abyssal peridotite, derived from a less depleted fertile mantle melt at a MORB setting after low degree (10–15%) partial melting. The study concluded that the serpentinite may have been created at a slow-spreading ridge, rather than a supra-subduction-zone setting. These rocks were later obducted and incorporated into the IMR of Indo-Myanmar suture zone.

► Ultramafic rocks are serpentinized in low P-T conditions. ► The protoliths were abyssal peridotite, derived from less depleted mantle melt. ► They are originated at an MORB setting after low degree (10–15%) partial melting. ► Serpentinite may have created at slow-spreading ridges, rather than a SSZ setting. ► We develop a model of origin and tectonic evolution of the Indo-Myanmar Ranges.