Late Miocene coesite-eclogite exhumed in the Woodlark Rift
Abstract
Late Miocene-Pliocene eclogites were exhumed in the WoodlarkRift of eastern Papua New Guinea, an actively extending regionwest of the Woodlark Basin seafloor spreading center. We reportthe discovery of coesite in late Miocene eclogite from the lowerplate of one of the D'Entrecasteaux Islands metamorphic corecomplexes within the Woodlark Rift. Zircon crystallization temperatures(650-675 °C) and 238U/206Pb age (ca. 8 Ma), and rutilethermometry (695-743 °C) combined with garnet-pyroxenethermometry (600-760 °C) and garnet-pyroxene-phengitebarometry (18-27 kbar), indicate that the coesite-eclogitewas exhumed from mantle depths (<IMG SRC="/math/ge.gif" ALT="≥" BORDER="0">90 km) to the Earth's surfaceat plate tectonic rates (cm yr-1). This late Miocene coesite-eclogiteis the youngest exhumed ultrahigh-pressure (UHP) rock on Earth,and its preservation ahead of the westward-propagating seafloorspreading center forces reevaluation of models for UHP exhumation,as well as the geologic and tectonic evolution of the WoodlarkRift.
- Publication:
-
Geology
- Pub Date:
- September 2008
- DOI:
- 10.1130/G25144A.1
- Bibcode:
- 2008Geo....36..735B