0000000000465269
AUTHOR
Mengist Teklay
Geochemistry, geochronology and isotope geology of Nakfa intrusive rocks, northern Eritrea: products of a tectonically thickened Neoproterozoic arc crust
Abstract The north-south-trending Neoproterozoic volcano-sedimentary plutonic associations in northern Eritrea are part of the Nubian Shield. The Nakfa intrusive rocks range in composition from gabbro to syeno-diorite to granite and alkaline syenite and intrude supracrustal rocks of volcanic and sedimentary origin. All granitoid rocks are metaluminous or slightly peraluminous and have typical I-type chemical signatures. The calc-alkaline intrusive rocks and the alkaline syenites have geochemical characteristics (e.g. low Nb values) typical of arc intrusives and plot as volcanic arc granites on various discriminant diagrams. Single zircon evaporation Pb-Pb ages and conventional multigrain U-…
Geochemistry, PbPb single zircon ages and NdSr isotope composition of Precambrian rocks from southern and eastern Ethiopia: implications for crustal evolution in East Africa
Abstract Geochemical and isotope data for granitoid rocks from southern and eastern Ethiopia delineate the presumed margin of the Pan-African juvenile terrain of the Arabian-Nubian Shield against an older crustal segment of unknown origin extending from eastern Ethiopia to northern Somalia. Granitoids from southern Ethiopia have higher Na2O and Na 2 0 K 2 O and lower Cr and Ni than granitoids with comparable SiO2 values from eastern Ethiopia. In southern Ethiopia three periods of magmatism are identified on the basis on single zircon 207 Pb 206 Pb evaporation ages, namely at ∼850, ∼750-700 and ∼650-550 Ma, and these correlate well with events documented from other parts of Ethiopia and the …