Christmas Island in the Indian Ocean contains basalts and trachytes.
Geochemical & isotopic analyses of these rocks document heterogeneities within the upper mantle.
The LVS exhibits an enriched mantle (EM-2) type end member composition.
The UVS is a product of plate flexure produced on the outer rise of the flexed oceanic lithosphere.
The UVS has EM-2 signature suggesting older composition is still present.