Abstract
Mineralogical and petrological study of ultramafic rocks of Bela Ophiolite of Cretaceous age revealed serpentinization after harzburgite. It is further evident on SiO2/MgO vs. Al2O3, molar ratio Si/Mg+Fe vs. LOI and MgO-SiO2-LOI diagrams. The XRD analysis also showed occurrence of olivine, different members of pyroxene and serpentine groups. The three polymorphous of serpentines can be distinguished on (Fe2++ Mg2+)/(Fe3++A13+) vs. H2O diagram, reflecting thermal regime in the study area. The analyzed samples of the study area showed relevance with Alpine peridotites. The plots MgO versus CaO and Ni show relation with average primitive mantle. The high amount of Ni and low content of Al2O3 in the study area indicates depleted-mantle peridotite. The parent rock is classified on the basis of Al/Si (av. 0.031) and Mg/Si (av. 1.05) ratios as harzburgite. The altered harzburgites displayed as serpentines on SiO2 vs. LOI plot and SiO2-(Al2O3+Fe2O3)-MgO triangular diagram.
Highlights
Samples of serpentinized ultramafic rocks of Bela Ophiolite (BO) were collected from eighteen different locations (Figure 1)
The BO is originated from obduction of Neotethyan oceanic plate on the rifted western margin of Indian plate (MOR), obducted floor of a back-arc basin (SSZ) and an associated island arc originated in a large oceanic fracture zone (Sheth, 2008 and Yingqian et al, 2008)
Petrology and mineralogy reveals that the studied rocks are serpentinites after harzburgite containing variable proportions of olivine and pyroxene
Summary
Samples of serpentinized ultramafic rocks of BO were collected from eighteen different locations (Figure 1). The pulverized rock samples were fused with lithium metaborate in a platinum crucible. Silica (SiO2) was estimated gravimetrically using hydrofluoric (HF) acid. The chemical composition of major and trace elements were determined by an atomic absorption spectrophotometer (Hitachi Model, Z 5000). X-ray analysis of rock samples were carried out using a Bruker AXS 5000 X-ray diffractometer. K α radiation was used during the analysis. Thin sections of relatively fresh ultramafic rocks were studied using Laborlus Pols microscope and photographed on Leica Microsystem, (DFC 280)
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