Sub-ophiolite metamorphic rocks in the Tungku area, Lahad Datu, eastern Sabah, Malaysia: origin and tectonic significance


Author : Shariff A.K. OmangPublication : Bulletin of the Geological Society of MalaysiaVolume : 39Page : 51-64Year : 1996


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Bulletin of the Geological Society of Malaysia, Volume 39, July 1996, pp. 51 - 64

 

Sub-ophiolite metamorphic rocks in the Tungku area, Lahad Datu, eastern Sabah, Malaysia: origin and tectonic significance

SHARIFF A.K. OMANG

Jabatan Sains Bumi, Fakulti Sains dan Sumber Alam, Universiti Kebangsaan Malaysia Kampus Sabah, Beg Berkunci No. 62, 88996 Kota Kinabalu, Sabah, Malaysia

 

Abstract: Sub-ophiolite metamorphic rocks (garnet amphibolites) found as clasts in late Early Miocene to late Middle Miocene mélange formed at high pressures and temperatures are interpreted as derived from a metamorphic sole underlying the Darvel Bay Ophiolite Complex, formed during subduction of ocean crust and the emplacement of the ophiolite complex in Sabah. Mineral chemistry and bulk rock geochemistry of the garnet amphibolites show that they are MORB tholeiites and represent oceanic crustal materials. These rocks were metamorphosed as pyroxene granulites and garnet amphibolites at high temperatures and pressures characteristic of upper mantle and were deformed and recrystallised with mylonitic textures in the amphibolite facies. A K/Ar age of 76 ± 21 Ma obtained from garnet amphibolite during the present study coincides with the Late Cretaceous-Palaeogene age of subduction beneath the Darvel Bay Ophiolite inferred from the stratigraphic evidence.