|Metamorphic complexes in Buru and Seram, northern Banda Arc|
Linthout, K.; Helmers, H.; Sopaheluwakan, J.; Surya Nila, E. (1989). Metamorphic complexes in Buru and Seram, northern Banda Arc. Neth. J. Sea Res. 24(2-3): 345-356
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579, more
|Authors|| || Top |
- Linthout, K.
- Helmers, H.
- Sopaheluwakan, J.
- Surya Nila, E.
The Palaeozoic Wahlua complex of Southeast Buru and the Tehoru complex of Central Seram are chiefly composed of graphitic phyllites/ schists and arkosic quartzites with minor intercalations of marble and amphibolite. The complexes show similar polyphase deformation and pre-Triassic metamorphic history as reflected in their simple (Barrovian-style) PT-loops. Both complexes may very well have originated in the same pre-Triassic metamorphic belt. Mylonite structures in the northern part of the Tehoru complex indicate right-lateral, N300E directed movements, and are explained as strike-slip along a transcurrent fault separating a southern metamorphic block from a northern essentially Triassic and younger non-metamorphic block. These movements in their turn are caused by the anticlockwise rotation of Seram since late-Triassic times. In Kaibobo, phyllonites and amphibolites adjacent to the ultramafic net-veined complex reveal temperatures of metamorphism of up to 740°C; these are explained as superimposed upside-down metamorphism caused by an overriding late-Miocene to early-Pliocene ultramafic sheet. Surprisingly young K/Ar ages of 4 to 5 Ma of biotites and muscovites from Wahlua and Tehoru complex are explained by re-heating of the pre-Triassic mica blasts due to overthrusting by hot mantle slabs, now largely eroded away. An average uplift rate of about 0.1 cm·a -1 during the last 4-5 Ma is calculated for Southeast Buru and Central Seram. Thrusting of metamorphics over non-metamorphics in 'median' Seram and of the ultramafic sheet in Southwest Seram may be also related to the anticlockwise rotation of Seram.