Evolution of the Pan‐African Wadi Haimur metamorphic sole, Eastern Desert, Egypt

Abstract

By comparison with the general features of metamorphic soles (e.g. vertical and lateral extension, metamorphic grade and diagnostic mineral parageneses, deformation and dominant rock types), it is inferred that the amphibolites, metagabbros and hornblendites of the Wadi Um Ghalaga–Wadi Haimur area in the southern part of the Eastern Desert of Egypt represent the metamorphic sole of the Wadi Haimur ophiolite belt. The overlying ultramafic rocks represent overthrusted mantle peridotite. Mineral compositions and thermobarometric studies indicate that the rocks of the metamorphic sole record metamorphic conditions typical of such an environment. The highest P–T conditions (c. 700 °C and 6.5–8.5 kbar) are preserved in clinopyroxene amphibolites and garnet amphibolites from the top of the metamorphic sole, which is exposed in the southern part of the study area. The massive amphibolites and metagabbros further north (Wadi Haimur) represent the basal parts of the sole and show the lowest P–T conditions (450–620 °C and 4.7–7.8 kbar). The sole is the product of dynamothermal metamorphism associated with the tectonic displacement of ultramafic rocks. Heat was derived mainly from the hot overlying mantle peridotites, and an inverted P–T gradient was caused by dynamic shearing during ophiolite emplacement. Sm/Nd dating of whole‐rock–metamorphic mineral pairs yields similar ages of c. 630 Ma for clinopyroxene and hornblende, which is interpreted as a lower age limit for ophiolite formation and an upper age limit for metamorphism. A younger Sm/Nd age for a garnet‐bearing rock (c. 590 Ma) is interpreted as reflecting a meaningful cooling age close to the metamorphic peak. Hornblende K/Ar ages in the range 570–550 Ma may reflect thermal events during late orogenic granite magmatism.

Multiple records from osmium, neodymium, and strontium isotope systems of the Nikubuchi ultramafic complex in the Sambagawa metamorphic belt, central Shikoku, Japan

“…Three main factors could serve to exclude the possibility that the Sambagawa metamorphism is responsible for the isochron age: 1) each sample retains the protogranular texture, 2) the major and trace element abundances plot on single lines with MgO abundance (Fig. 3), and 3) several reports show that clinopyroxene sometimes holds older isotopic information than garnet (Mørk and Mearns, 1986;El-Naby et al, 2000). The SmNd system in this study is strongly dependant on the modal abundance of clinopyroxene.…”

“…The closure temperature of the Sm-Nd system in garnet is 700-750°C (Möller et al, 2002). Mørk and Mearns (1986) and El-Naby et al (2000) reported that clinopyroxene sometimes retains older isotopic information than does garnet. The closure temperature of clinopyroxene would be comparable to or higher than that of garnet.…”

Geochemical constraints from the Hafafit Metamorphic Complex (HMC): Evidence of Neoproterozoic back-arc basin development in the central Eastern Desert of Egypt

“…Frisch and Al Shanti, 1977;Vail, 1985;Krö ner et al, 1988;Stern, 1994;Abdel Rahman, 1995;Abd El-Naby et al, 2000).…”

Spectral analysis of ASTER data covering part of the Neoproterozoic Allaqi-Heiani suture, Southern Egypt

“…It is dominated by volcano-sedimentary rocks, dismembered ophiolites, and syn-and post-tectonic granitoids as shown in Fig. 1 (Stern, 1994;Abdelsalam and Stern, 1996;El-Nisr, 1997;Abd El-Naby et al, 2000;El-Kazzaz and Taylor, 2001;Ramadan et al, 2001;Abdelsalam et al, 2003). It is comprised of a 30 km wide zone of highly deformed ophiolitic assemblages, shelf metasediments, arc volcanics and volcaniclastics, and granitoids (Abdelsalam et al, 2003).…”