Molucca Sea Collision Zone

The Molucca Sea Collision Zone is postulated by paleogeologists to explain the tectonics of the area based on the Molucca Sea in Indonesia, and adjacent involved areas.

The tectonic relationship of the Sangihe Plate, Halmahera Plate, and the Molucca Sea Plate, plus the volcanic Halmahera Arc and the Sangihe Arc is complex. Their interrelationship constitutes the Molucca Sea Collision Zone. The north of this zone interlinks with the Philippine Mobile Belt. Some call this linkage the Philippine–Halmahera Arc and consider it an integral part of the elongated zone of convergence extending north through the Philippines into eastern Taiwan. In the Molucca Sea Collision Zone model, the Molucca Sea Plate has been totally consumed by the arc-arc collision of the Halmahera Arc and the Sangihe Arc of eastern Indonesia.

The Molucca Sea Collision Zone is the site of an orthogonal collision between two active subduction systems. Both the Halmahera subduction system to the east, and the Sangihe subduction system to the west, have subducted oceanic lithosphere of the Molucca Sea plate, which has been completely consumed, with the Sangihe arc now over-riding the Halmahera forearc. Both volcanic arcs have been active since the Neogene. Both arcs show increased evidence for sediment recycling as the collision progressed, but for differing reasons. In Halmahera, this may represent an increased sediment flux through the arc front, while in Sangihe it may simply reflect a greater opportunity for melting of sediment-fluxed portions of the mantle wedge. In both cases the change in arc geochemistry can be related to the evolving architecture of that particular subduction zone. The Halmahera lavas also record a temporal change in the chemistry of the mantle component that resulted from induced convection above the falling Molucca Sea Plate drawing compositionally distinct peridotite into the mantle wedge.

...
Wikipedia