Spectral characteristics and petrology of Sinai Mesozoic basaltic rocks: Gebel Farsh El Azraq-Gebel Himayir area, Um Bogma, southwestern Sinai, Egypt

Abstract

Sinai Mesozoic basalts are restricted in its southwestern portion at Um Bogma area, where they occur as intra-continental fissure-fed sills, dykes, plugs and lava flows, following mainly the older structural and crustal weaknesses planes. During Late Paleozoic - Middle to Late Triassic, Egypt had witnessed sporadic tectonic disturbances and faulting activities accompanied by volcanisms. Faulting activity continued during Early to Middle Jurassic and was associated with crustal stretching and basaltic volcanism. At Um Bogma area, southwestern Sinai Peninsula, Middle Triassic, and Early Jurassic basaltic exposures intruded/extruded the Carboniferous sandstones. The main Mesozoic basalts outcrop at Gebel Farsh El Azraq - Gebel Himayir area, where they were successfully discriminated from their surrounding country rocks using Landsat-8 dataset. The Mesozoic basaltic rocks are the least reflective rocks and exhibit a characteristic spectral curve, compared to their country rocks. Landsat-8 bands 7, 5, 3 in RGB and Principal Component Analyses (PCA) technique were used in lithological discrimination of the Mesozoic basalts and their surrounding Late Neoproterozoic basement rocks and Phanerozoic sedimentary succession. Accordingly, a new geological map was produced for the study area. Petrography and geochemistry of these basalts were addressed. Characteristically they contain substantial MgO contents (22.24 to 7.09 wt%) and exhibit low TiO2 (1.56–0.77 wt%) and P2O5 (0.30–0.15 wt%) contents. Geochemically, they pertain to the low P2O5 –TiO2 continental tholeiitic to transitional basalts and point out to enriched MORB magma sources. They suggest derivation from spinel-garnet lherzolite source by moderate non-modal partial melting (ca 20–30%). Their petrogenesis was discussed and fractional crystallization modeling was performed as a plausible mechanism to be accounted for their evolutions.