Bulletin of the Geological Society of Malaysia, Volume 38, Dec. 1995, pp. 31 – 48

Petrology and geochemistry of the mantle-sequence peridotite of the Darvel Bay Ophiolite, Sabah, Malaysia

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

Abstract: The mantle-sequence peridotites of the Darvel Bay Ophiolite are represented predominantly by depleted harzburgites. These rocks are characterised by mineral chemistry of spinel X_Cr = 39, X_Mg = 61; olivine F_o = 90 and orthopyroxene (Opx) En = 88-90, Al₂O₃ – 3.4 wt.%, CaO = 1.8 wt.%), suggesting a mantle residue which has undergone a moderate to high degree of a previously depleted source (oceanic upper mantle). Composition of spinel X_cr-Opx (Al₂O₃) and bulk-chemistry indicate ~20% partial melting of this source. The Darvel Bay harzburgites are less depleted (refractory) mantle than the harzburgites of Oman, Papuan and Halmahera Ophiolites. The Darvel Bay harzburgites represent a supra-subduction zone (SSZ)-ophiolite type, supported by bulk-rock chemistry of TiO₂ contents. The tectonic evolution model of the Darvel bay Ophiolite is much easier to explain using a model of supra-subduction zone (SSZ) ophiolite accreting new material in a forearc region.

https://doi.org/10.7186/bgsm38199504