Abstract

• The ophiolite of the study area is a remnant of the Tethyan ophiolites preserved at the eastern margin of the Indo-Myanmar Orogenic Belt. Mineralogical features, textural relations and relative abundance of constituent minerals reveal that the samples are dominated by spinel lherzolite and spinel harzburgite with minor dunite, and characterized by olivine (>40 % volume) with varying amount of orthopyroxene and clinopyroxene. The samples display the preferred orientation of olivine, strain shadow, undulose extinction, kink bands of cleavage traces in pyroxenes, and are essentially spinel bearing suggesting derivation from deeper source in the mantle beyond the stability limit of plagioclase. Magnetite forms along fractures and rims of the spinel grains due to the result of cation exchange between spinels and coexisting silicates forming low pressure and low temperature metamorphic alteration. The samples have relatively homogeneous whole-rock compositions with Mg# values (90–92), and SiO2 (43.6 – 44.8 wt%), Al2O3 (2.5–2.9 wt%) and CaO (2.3–2.5 wt%) contents and enriched in transition metals. The samples have negative correlations between SiO2, Fe2O3, and CaO with MgO and are more similar to mid-oceanic ridge type. Correlating with the northern segment of the Western Ophiolite Belt it is likely suggest that the peridotite rock exposed in the northern and southern segment were formed in the mid-oceanic ridge setting and were accreted to the Indo-Myanmar Ranges from the downgoing Tethyan plate as part of subduction-accretion processes.