Reunion hotspot

Reunion hotspot
Name	Reunion hotspot
Location	Indian Ocean
Coordinates	21°S 55°E
Type	Mantle plume
Age	~65 Ma to present
Last eruption	Ongoing (Piton de la Fournaise)
Notable	Deccan Traps, Mascarene Islands, Piton de la Fournaise

Reunion hotspot is a long-lived mantle plume source in the southwestern Indian Ocean that produced the Deccan Traps, the Chagos-Laccadive Ridge, and the Mascarene Plateau leading to volcanic islands such as Réunion (French overseas department), Mauritius, and Rodrigues. It is central to debates linking deep mantle plume processes to surface volcanism, plate motion reconstructions, and large igneous provinces like the Deccan Traps and the Cretaceous–Paleogene extinction event.

Geology and Tectonic Setting

The hotspot is situated near the eastern margin of the Somali Plate and the western margin of the Indian Plate, interacting with the Mid-Indian Ocean Ridge, the Carlsberg Ridge, and the Makran Trench influenced by motions recorded in the Indian tectonic plate track and the Seychelles microcontinent. The plume track aligns with the Deccan Traps, the Laccadive Ridge, the Chagos Bank, the Maldives Ridge, and the Mascarene Islands sequence, reflecting the relative motion between the Indian Plate, the Somali Plate, and the African Plate since the Late Cretaceous. Plate reconstructions that incorporate data from the Kerguelen Plateau, the Broken Ridge, and the Carlsberg Ridge are used to correlate hotspot-derived magmatism with paleo-plate boundaries and the emplacement of the Deccan Traps flood basalts.

Volcanic Features and Petrology

Volcanic centers associated with the hotspot include Piton de la Fournaise and older edifices on Réunion (French overseas department), Mauritius, and submarine seamount chains such as the Mascarenes and the Cargados Carajos Shoals, showing a range from highly alkaline basalts to tholeiitic flood basalts similar to those in the Deccan Traps and the Kerguelen Plateau. Petrological studies compare mineral assemblages and whole-rock geochemistry—including trace elements and isotopes such as Sr isotope, Nd isotope, Pb isotope, and He isotope ratios—linking erupted lavas to deep-mantle signatures observed beneath the Hawaii hotspot and the Iceland hotspot and distinguishing plume components from lithospheric contamination derived from the Seychelles microcontinent and continental fragments. Hydrothermal alteration and pillow-lava morphologies on submarine portions are mapped alongside subaerial stratigraphy at Piton de la Fournaise to constrain eruption styles comparable to those documented for Kilauea and Etna.

Geochronology and Evolution

Radiometric dating methods including 40Ar/39Ar dating, U-Pb dating, and palaeomagnetic stratigraphy establish a plume initiation age near the end of the Cretaceous (~65 Ma) contemporaneous with the Deccan Traps eruptions, followed by age-progressive volcanism along the track producing the Chagos-Laccadive Ridge, Maldives, and Mascarene sequences. The temporal correlation with the Deccan Traps and sedimentary records in the Gondwana remnants supports models tying plume flux pulses to climatic and biotic events such as the Cretaceous–Paleogene extinction event and Paleogene warming episodes recorded in Foraminifera assemblages and stable isotope excursions. High-precision dating on Piton de la Fournaise lavas yields Holocene to historic ages analogous to eruption chronologies compiled for Eyjafjallajökull and Mount St. Helens.

Geophysical Imaging and Mantle Structure

Seismic tomography, including body-wave and surface-wave models, reveals a low-velocity seismic anomaly beneath the southwest Indian Ocean extending from the upper mantle toward the lower mantle, comparable to imaged plume conduits under the Hawaii hotspot and the Iceland hotspot. Shear-wave splitting, receiver-function analyses, and mantle transition-zone thickness variations correlate with geochemical plume signatures seen in He isotope ratios, implying a deep-mantle, possibly Large Low-Shear-Velocity Province-related source. Gravity anomalies, magnetotelluric surveys, and seismic reflection profiles across the Mascarene Plateau and Ninetyeast Ridge complement tomographic models, constraining plume buoyancy flux and lithospheric flexure analogous to studies of the Reykjanes Ridge and the Kerguelen hotspot.

Relationship to Regional Plate Dynamics

The plume's interaction with the northward-moving Indian Plate produced the age-progressive volcanic track and influenced rift propagation during the fragmentation of Gondwana, impacting the separation of the Seychelles microcontinent and the opening of the Indian Ocean basins. Comparisons with contemporaneous plume events such as the Kerguelen plume and correlations with spreading rates at the Carlsberg Ridge allow testing of plume-ridge interaction models and plume-pulse hypotheses invoked for other large igneous provinces like the Siberian Traps. Reconstructions using paleomagnetic poles from India and surrounding terranes, as well as hotspot reference frames tied to Hawaii and Reykjanes, are employed to resolve absolute plate motion and plume drift scenarios.

Human and Environmental Impact

Active volcanism at Piton de la Fournaise drives hazards on Réunion (French overseas department), affecting infrastructure, air traffic, and tourism with lava flows, ash emissions, and airborne particulate impacts comparable to historic events at Mount Etna and Krakatoa. The ancient Deccan eruptions linked to the plume are implicated in major environmental perturbations recorded in marine and terrestrial records, influencing global climate, ocean acidification, and biotic turnover events paralleling those studied in the context of the Cretaceous–Paleogene extinction event. Conservation and monitoring efforts on Réunion (French overseas department), Mauritius, and adjacent marine protected areas involve institutions such as IPGP and national geological surveys to mitigate risks and study ongoing plume-related processes.

Category:Hotspots Category:Volcanism of the Indian Ocean Category:Geology of Réunion