| The plate carrying the Afro-Arabian continent began to be subducted beneath the oceanic crust of the Tethys at a deep ocean trench. |
| Mud volcanoes indicate that this subcretion occurs where dewatering stiffens the subducted sediments. |
| Site 863 is located at the toe of the landward trench slope above the subducted Chile Ridge, just south of the Chile Triple Junction. |
| It is therefore likely that the radiogenic lead content in these rocks is also the result of a contribution from a subducted sedimentary component. |
| Is the whole crustal section exhumed, or is only part of the subducted crust exhumed? |
| The island contains a suite of rocks deposited in a forearc setting to the west of a magmatic arc, formed as the Pacific plate was subducted beneath Antarctica. |
