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Ascent of Ultrahigh-Pressure Rocks in Southeastern Papua New Guinea, as Revealed by Ti-in-Quartz Thermometry and Rb-Sr Dating
thesis
posted on 2022-03-02, 19:27 authored by Megan S. KorchinskiDebate concerns the timing of ultra-high pressure (UHP) metamorphism and
the kinematics of exhumation of the world’s youngest known
eclogite-facies rocks (U-Pb ages of 4 – 8 Ma) in the Woodlark Rift of
southeastern Papua New Guinea. End-member kinematic models that have
been proposed for the crustal exhumation of metamorphic gneiss domes
that host these young eclogites include detachment-related (asymmetric)
gneiss doming (metamorphic core complexes), and pure shear-dominated
(symmetric or diapiric) gneiss doming. The former is predicted to
exhume the deepest structural levels of the domes adjacent to a major
normal fault. The latter is predicted to yield a concentric pattern of
exhumation levels with the deepest rocks located near the center of the
domes. As far as can be determined, there are no mappable field
gradients with respect to either the high-pressure metamorphism or the
later pervasive amphibolite-facies overprint in the lower crust. This
apparent uniformity contributes to uncertainty regarding the
distribution of vertical strain in the body, and thus to the mode of
dome emplacement.