Garnet hornblendite in the Meatiq Core Complex, Central Eastern Desert of Egypt: Implications for crustal thickening preceding the ∼600 Ma extensional regime in the Arabian-Nubian Shield

摘要: Abstract Dike-like bodies of garnet (Py 77.04–84.66 ) hornblendites were recorded, for the first time, in structurally lowest parts gneiss Meatiq Core Complex Central Eastern Desert Egypt. They are composed mainly hornblende (pargasite to pargasitic hornblende), [depleted LREE with flat HREE segments (normalized CI-chondrite), and enriched LILE N-MORB)] crystallized from sub-arc tholeiitic melt that derived wet mantle wedge (615–600 Ma ago), at P = 23–27 kbar T = 510–600 °C. Diapirism hot due decompression caused partial dehydration melting (P = ∼12 kbar T = 800–>1100 °C) into pyrope-almandine diopside (Wo 49–51 En 32–34 Fs 16–17.5 ). The clockwise P-T path continued by isothermal decomposition (10–11 kbar) hercynite-rich spinel ( X Fe 2+  = 0.46–0.64) quartz. By continuous cooling probably introduction Abu Ziran granite-related solutions, followed a retrograde greenschist facies hydration path, including transformation tremolite (T = 280–420 °C pressure > 5 kb) chlorite (T = 190–345 °C). In addition, metasomatic minerals feldspars titanite, minor ilmenite, rutile, topaz calcite formed, as well composition original amphibole changed having increases FeO, TiO 2 K O decreases Al 3 , MgO Na O. Deep source implies probable local crustal thickening shortening, while their exhumation was most accompanied NW-SE extension thinning previously thickened crust occurred during oblique island arc convergence closure Mozambique ocean collision East West Gondwanaland.