Arc-continent collision in Papua Guinea: Constraints from fission track thermochronology

The Papua New Guinea (PNG) Mobile, Belt adjacent to the Finisterre Are was formerly the leading NE corner of the Australian plate that converged obliq uely with the Pacific plate. Forty new apatite and zircon fission track ana lyses of Mobile Belt rocks previously dated by K-Ar and Rb-Sr analyses cons train Neogene time-temperature paths and tectonic models. The Paleogene are along the southern margin of the Caroline plate was juxtaposed against PNG in the early Miocene, coeval with locking up of the west dipping Solomon s ubduction tent: by the Ontong Java Plateau. These events initiated wrenchin g along the northern PNG margin and increased westward subduction of the So lomon Sea plate beneath the eastern margin. The Mobile Belt underwent exten sion above the downgoing slab with rapid cooling of metamorphic rocks at si milar to 17 Ma, immediately prior to emplacement of the Maramuni Are from 1 7 to 12 Ma. A change in plate motion at similar to 12-10 Ma terminated the are and caused PNC-Caroline plate convergence, creating the orogenic belt i n New Guinea from 12 to 4 Ma. This resulted in similar to 4.5 km of uplift and similar to 3 km of denudation and cooling of the entire Mobile Belt in the late Miocene, propagating westward along the Mobile Belt at 8-5 Ma and southward into the Fold Belt at 5-4 Ma. The compression caused thrusting of Miocene strata within the Mesozoic type section. A further change in plate motion at 4-3 Ma returned the margin to transpression with local compressi on along strike-slip faults and ongoing collision of the Finisterre Are ter rane.