Provenance and paleotectonic setting of the triassic to lower jurassic adigrat sandstone around Yejube, Blue Nile Basin, Central Ethiopia

Abstract

Mineralogical and geochemical (major and trace element) data are presented for the Adigrat Sandstone exposed around Yejube, located in the Blue Nile Basin of central Ethiopia, to determine its provenance and tectonic setting. On the Q-F-L diagram, the Yejube Adigrat Sandstone falls within the sublitharenite to quartzarenite fields, consistent with its chemical classification. The Yejube Adigrat Sandstone comprises a higher amount of sub-rounded to rounded quartz grains (~ 89.98%), with subordinate amounts of rock fragments and feldspars associated with higher SiO₂/Al₂O₃ and K₂O/Na₂O ratios, which suggest that it is highly reworked, recycled, and matured. Mineralogical and major element analyses of the Yejube Adigrat Sandstone demonstrate a quartzose sedimentary provenance. However, the immobile trace elemental ratios (La/Sc, Th/Co, La/Co, Cr/Th, and Th/Sc), high LREE/HREE ratios, and low Eu/Eu* values (Eu/Eu* = 0.5) strongly support a felsic (granitic and gneissic) source. Furthermore, a comparison of provenance studies for the Adigrat Sandstone in the Yejube and Dejen–Gohatsion areas of the Blue Nile Basin and the Mekelle outlier indicates that the sediments of the former were primarily derived from felsic source rocks, similar to those of the Mekelle outlier, in contrast to the mafic to intermediate sources identified at Dejen–Gohatsion in the Blue Nile Basin. The higher quartz content (~ 89.98%), SiO₂/Al₂O₃, and K₂O/Na₂O ratios, the enrichment in immobile trace elements (e.g., La, Th, Zr, Co, Sc, Hf), the negative Eu anomaly, and the rare earth element (REE) pattern, which are almost like that of the typical average upper continental crust, infer that the Yejube Adigrat Sandstone was deposited in a passive margin tectonic setting. Moreover, the tectonic discrimination diagram for Yejube Adigrat sandstone indicates a passive margin tectonic setting.