**5.2 The high sinking velocity of the subducted slab**

Given that the emplacement of the La Conception lavas occurred around 29.12 Ma and that the Oligocene subduction zone began at approximately 33.7–35 Ma at a location about 50 km west of New Caledonia (as indicated by a + 100 mGal gravity anomaly, [121, 122], the sinking velocity of the subducted slab to depth ∼119–129 km within the mantle wedge where the La Conception lavas generated [20] ranges from 4.0 to 5.1 cm/year. Such a rapid sinking velocity, combined with the cold nature of the subducting slab, may not allow enough interaction between the sinking slab and the mantle wedge to produce significant volumes of arc magmas [123, 124].
