| Abstract Submission No. | ABS-2.1-0203 |
| Title of Abstract | Episodic Explosive Magmatic Degassing of Helium-3 at 67.67°E, eastern Southwest Indian Ridge |
| Authors | Surya Prakash* |
| Organisation | National Centre for Polar and Ocean Research |
| Address | Headland Sada Vasco-da-Gama, Goa, India Pincode: 403804 E-mail: SURYA@NCPOR.RES.IN |
| Country | India |
| Presentation | Oral |
| Abstract | Crustal accretion at the eastern Southwest Indian Ridge (eSWIR) is governed by highly magmato-tectonic regime, where mantle detachment faulting dominates, resulting in peridotite-rich crust interspersed with localized gabbroic intrusions. Volcanic centres are spatially restricted (10¿20 km wide) and characterized by anomalously thick crust (~13 km), attributed to episodic magma injection. Recent investigations into dissolvedethane concentrations in deep waters along the eastern SWIR have identified a hydrothermal field at 67.67°E, associated with three distinct hydrothermal plumes at varying depths: Plume 1 (2300¿3150 m), Plume 2 (3600¿4100 m), and Plume 3 (4200¿4500 m). Plume 1 is particularly notable for its unusual vertical extent (~700 m), elevated turbidity (up to 0.09 NTU), and a significant decrease in oxidation-reduction potential (up to 20 mV), all indicative of an event-type hydrothermal plume. Exceptionally high helium-3 values (112% above a 13% background) further support recent magmatic degassing in this region. Despite these strong hydrothermal signals, methane (6.64 nmol/kg) and manganese (19.53 nmol/L) concentrations in Plume 1 are relatively low. However, the helium-3 to heat (0.014 mol/J) and manganese to heat (0.04 nmol/J) ratios are consistent with values observed in other event plumes, reinforcing the interpretation of recent and possibly transient magmatic activity beneath the ridge. |
| Keywords | Hydrothermal plumes, Southwest Indian Ridge, Mantle degassing |