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High-grade metamorphism related to peridotite emplacement near Atapupu, Timor with reference to the Kaibobo Peridotite on Seram, Indonesia
Helmers, H.; Sopaheluwakan, J.; Tjokrosapoetro, S.; Surya Nila, E. (1989). High-grade metamorphism related to peridotite emplacement near Atapupu, Timor with reference to the Kaibobo Peridotite on Seram, Indonesia. Neth. J. Sea Res. 24(2-3): 357-371
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579, more
Peer reviewed article  

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Keyword
    Marine

Authors  Top 
  • Helmers, H.
  • Sopaheluwakan, J.
  • Tjokrosapoetro, S.
  • Surya Nila, E.

Abstract
    Spinel peridotites from Kaibobo (Seram) and Atapupu (Timor) show a cooling and deformation history starting at 1060 to 1030°C above 8 kbar, deformed and partly recrystallized at 900 ± 40°C above 6.5 kbar until 710 ± 30°C at 5.8 to 3.7 kbar, suffering a continuous grain-size reduction. Then they recrystallized partly to tremolite-talc and serpentine schists. Net-veined complexes of hornblende diorite formed in the peridotite above 860°C at 6.5 to 7 kbar fluid pressure and recrystallized after deformation at 660 ± 15°C. Metamorphic conditions in pelitic and mafic rocks underneath the peridotite in Atapupu corresponded to over 800°C at 6 to 7 kbar. Prograde metamorphism is nearly obliterated. Continuous mylonitization accompanied metamorphic re-equilibration to about 640°C at 4 to 4.5 kbar. Subsequent re-equilibration after the mylonitization occurred from 600 ± 20°C to about 500°C at 4 to 3 kbar in combination with or followed by partial epidotization, chloritization, prehnitization and zeolitization in spots or veins. A granitic to trondjemitic melt formed from the metamorphites above 750 ± 30°C at aH2 0 = 0.7 to 0.8. Mylonitic leucosome is scarcely present. It is suggested that the displaced part of this melt is included in the late granitic bodies crosscutting the peridotite. Axial directions of four successive folding phases at Atapupu are consistent with NS-shortening during subduction, if clockwise rotation related to strike-slip movement during peridotite emplacement is envisaged. Folding and mylonitization are simultaneous because the first three phases deform high-grade mylonites and are partly obliterated in medium-grade ones. The shape of the metamorphic loop suggests a higher uplift rate at Kaibobo (Seram) in respect to Atapupu (Timor).

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