Unroofing of active metamorphic core complexes in the D'Entrecasteaux Islands, Papua New Guinea

摘要: Metamorphic core complexes in the D9Entrecasteaux Islands are forming as a result of active extension at western end Woodlark Basin spreading center. High-grade metamorphic rocks exist cores gneissic domes, including eclogites formed minimum depths 45-75 km (i.e., 13-21 kbar). High temperatures were maintained during uplift basement from kbar ( T ≈ 730-900 °C) through 7-11 570-730 to ∼5-6 730 °C). Subsequent rapid cooling (>>100 °C/m.y.) occurred between 1 and 2 Ma (on basis 40 Ar/ 39 Ar geochronology). The core-zone transected by kilometre-scale, amphibolite-facies ductile shear zones 25-35 km. Extensive intrusion granodiorite plutons occurred, age intrusions constrains late-stage shear-zone activity ∼2 younger. Unroofing was accomplished faults bounding gneiss juxtaposing them against ultramafic sedimentary deposits. Surface continues today has led topographic elevations up 2.5