Molucca Sea Collision Zone

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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.

Contents

Tectonics

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. [1]

Single collision zones

The magmatic systems are reaching the end of their life as island arcs and are becoming a single collision zone, [2] lending weight to the contention that Halmahera and Sangihe should be regarded as tectonic plates rather than volcanic arcs.

Northern extension

Seismic and tomographic discrepancies in the mantle up to 400 km below Mindanao in the Philippines, indicate it is a more advanced northern extension of the Molucca Sea Collision Zone. [3]

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Halmahera Plate has recently (1990s) been postulated to be a microplate within the Molucca Sea Collision Zone of eastern Indonesia.

Sangihe Plate has recently (1990s) been postulated to be a microplate within the Molucca Sea Collision Zone of eastern Indonesia.

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Divergent double subduction Tectonic process in which two parallel subduction zones with different directions are developed on the same oceanic plate

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South China Craton

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Subduction tectonics of the Philippines

The subduction tectonics of the Philippines is the control of geology over the Philippine archipelago. The Philippine region is seismically active and has been progressively constructed by plates converging towards each other in multiple directions. The region is bounded by subduction zones, where surrounding oceanic plates to the east and west slide towards the centre of the Philippine archipelago. Subduction results in deep oceanic trenches, such as the Philippine Trench and Manila Trench, bounding the eastern and western sides of the Philippine archipelago, respectively. The Philippine archipelago is also cut along its length by a left-lateral strike-slip fault known as the Philippine Fault. The region is also known as the Philippine mobile belt due to its complex tectonic setting.

A magmatic lull is a period of declined magmatic activity in volcanically active regions. They may occur as a result of underthrusting of hinterland lithosphere beneath a volcanic arc, changes in subduction parameters such as relative velocity, direction and slab dip, arc-arc collisions and subduction hinge advance. Individual magmatic lulls may last tens of millions of years between periods of volcanicity.

References

  1. Macpherson, Forde, Hall and Thirlwall (2003) in Intra-Oceanic Subduction Systems: Tectonic and Magmatic Processes, ISBN   1-86239-147-5 p208
  2. Colin G Macpherson et ors, Geochemical evolution of magmatism in an arc-arc collision: the Halmahera and Sangihe arcs, eastern Indonesia, in Robert D Larter, ed, (2003) Intra-oceanic Subduction Systems, Geological Society of London. p208
  3. Colin G Macpherson et ors, Geochemical evolution of magmatism in an arc-arc collision: the Halmahera and Sangihe arcs, eastern Indonesia, in Robert D Larter, ed, (2003) Intra-oceanic Subduction Systems, Geological Society of London. p215