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

Shariff A. K. Omang. (1995) Petrology and geochemistry of the mantle-sequence peridotite of the Darvel Bay Ophiolite, Sabah, Malaysia. Bulletin of the Geological Society of Malaysia, 38. pp. 31-48. ISSN 2637-109X

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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 Xcr = 39, XMg = 61; olivine Fo = 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 Xcr-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.

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