Integration of remote-sensing, structural, and geochemical data for characterizing granitoid rocks in Um Naggat pluton, Central Eastern Desert, Egypt

Abstract

Integration of remotely-sensed data, field work in addition to geochemical and mineral chemistry analyses, indicates that the Um Naggat granite pluton (UNP) has distinctive lithologic and structural characteristics. Image transformation techniques of using Landsat-8 Operational Land Imager (OLI) data successfully discriminated lithologic characteristics and highlighted hydrothermally altered areas. Shuttle Radar Topography Mission (SRTM) and OLI data allowed highlighting the structural contacts and revealed that the dominant structural trends are NW-SE, NE-SW, and N-S. Petrographic examination, field, and structural survey results revealed that the (UNP) pluton consists of biotite alkali feldspar granite (BAFG) and alkali granite (AG) in addition to a hybrid granite zone (HGZ). The BAFG phase is dominated by an alkaline suite with composition ranging from granite to alkali feldspar granite and pertains to post-orogenic granite (POG) and within-plate granites (WPG). The AG represents the youngest alkali granite phase of magmatism in the studied pluton. Various enclaves from diorites and microgranites have been recorded within the HGZ. Field relationships confirmed with quantitative analysis of magmatic fabric measurements indicate that the AG granitic phase was emplaced as subparallel-elongated sheets or dike-like masses trending E-W and associated with an extensional regime overprinted by the right-lateral strike-slip regime. This phase of “within plate” hypersolvus granite has excessive of large-ion lithophile (LIL) and high field strength (HFS) elements such as Zr, Nb, and Ga that belongs to A-type granites, being depicted by elevated alkali composition and high Fe2O3t/(Fe2O3t +MgO) ratios, and excessive amount of Zr, Y, Nb, and Ga. Microprobe analysis reveals that the compositions of amphibole mineral in the HGZ extent from magnesio-hornblende to actinolite and the temperature of the plagioclase range from 900 to 1050 °C, while the plagioclase of the BAFG is extremely pure albite in composition.