Abstract
This study discussed the Sorap Massif which is the ophiolitic fragment composed of the upper mantle and lower crustal section of an ophiolitic sequence. An ophiolitic sequence in Sorap Massif consists of harzburgite, dunite, large distant units of serpentinized wehrlite intrusion and outcrop of confined layered gabbro covered by the Quaternary sand dunes. The basal part of gabbroic intrusion is in contact with mantle rocks and the upper part is juxtaposed with the Kuchakki Volcanic Group. On outcrop-level and in hand specimen, the gabbros exhibit needle-like ferromagnesian minerals including hornblende associated with plagioclase and pyroxene. Petrographically the gabbros are classified into norite, gabbro norite and gabbro. The mineral constituents of norite are plagioclase, orthopyroxene and amphibole, gabbro norite is consists of equal constituents of orthopyroxene and clinopyroxene, plagioclase and amphibole and the gabbro is composed of clinopyroxene, plagioclase and amphibole. The high constituents of minerals such as pyroxene, amphibole and low constituents of olivine in the Sorap gabbros indicates that these gabbros are formed by the immature part of the oceanic plate with dehydration of the oceanic plate subduction.
Highlights
An ophiolite is a distinctive rock unit of ultramafic-mafic rocks sequence from bottom to the top including serpentinized ultramafic rocks at the base, gabbroic rocks periodically indicated the cumulate texture, complex of mafic sheeted dikes and mafic volcanic rock associated with distinctive bodies of chromite, sodic constituents of felsic types of igneous rock overlying with pelagic sedimentary rocks [1]
Ali Muhammad et al, J. mt. area res. 06 (2021) 1-11 mainly accepted that the ophiolite indicates that the oceanic crust has been emplaced onto the continents [3]
The Sorap massif of Ras-Koh Ophiolite is composed of mantle peridotites, ultramafic cumulates and mafic cumulates
Summary
An ophiolite is a distinctive rock unit of ultramafic-mafic rocks sequence from bottom to the top including serpentinized ultramafic rocks at the base, gabbroic rocks periodically indicated the cumulate texture, complex of mafic sheeted dikes and mafic volcanic rock associated with distinctive bodies of chromite, sodic constituents of felsic types of igneous rock overlying with pelagic sedimentary rocks [1]. An ophiolite is a distinctive rocks unit of ultramafic – mafic rocks sequence from bottom to the top including a serpentinized ultramafic rock, gabbroic rocks periodically indicated the cumulate texture, complex of mafic sheeted dikes and mafic volcanic rock associated with distinctive bodies of chromite, sodic constituents of felsic types of igneous rock overlying with sedimentary rock units such as chert, shale and minor bed of limestone [5]. We are going to discuss the geological and petrological features of the gabbroic rock units from Sorap Massif in the RasKoh ophiolite by using their field features and petrography results
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