U-Pb and Rb-Sr geochronology of the Western Ethiopian Shield

Abstract

Research Article| September 01, 1990 U-Pb and Rb-Sr geochronology of the Western Ethiopian Shield TEKLEWOLD AYALEW; TEKLEWOLD AYALEW 1Ottawa-Carleton Geoscience Centre and Department of Earth Sciences, Carleton University, Ottawa, Canada K1S 5B6 Search for other works by this author on: GSW Google Scholar KEITH BELL; KEITH BELL 1Ottawa-Carleton Geoscience Centre and Department of Earth Sciences, Carleton University, Ottawa, Canada K1S 5B6 Search for other works by this author on: GSW Google Scholar JOHN M. MOORE; JOHN M. MOORE 1Ottawa-Carleton Geoscience Centre and Department of Earth Sciences, Carleton University, Ottawa, Canada K1S 5B6 Search for other works by this author on: GSW Google Scholar RANDALL R. PARRISH RANDALL R. PARRISH 2Geological Survey of Canada, 601 Booth Street Ottawa, Canada K1A 0E8 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1990) 102 (9): 1309–1316. https://doi.org/10.1130/0016-7606(1990)102<1309:UPARSG>2.3.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation TEKLEWOLD AYALEW, KEITH BELL, JOHN M. MOORE, RANDALL R. PARRISH; U-Pb and Rb-Sr geochronology of the Western Ethiopian Shield. GSA Bulletin 1990;; 102 (9): 1309–1316. doi: https://doi.org/10.1130/0016-7606(1990)102<1309:UPARSG>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Five U-Pb zircon and four Rb-Sr whole-rock isochron dates constrain the ages of plutonic rocks and their subsequent history within the Western Ethiopian Shield. The U-Pb data show plutonic activity between 830 and 540 Ma, similar to the time span established for the Pan-African rocks of the Southern Red Sea Hills of the Sudan and the Jeddah terrane of Saudi Arabia. U-Pb zircon ages of 828 +9/-2 and 814 ± 2 Ma, obtained from pre-kinematic plutons of the Birbir Domain, date the time of their emplacement. One of these plutons (Goma) yielded a whole-rock Rb-Sr isochron date of 759 ± 18 Ma. Granite sheets within the high-grade Baro Domain, believed to be anatectic, were dated by U-Pb at 783 +19/-14 Ma. The 780-760 Ma event is interpreted as a period of Pan-African regional metamorphism that correlates with the age of low-grade metamorphism of arc-related rocks elsewhere in northeast Africa. Other reset Rb-Sr whole-rock isochrons from the Western Ethiopian Shield that cluster around 635 Ma provide evidence of significant isotopic homogenization, probably associated with major transcurrent movement parallel to a plate margin. A U-Pb lower-intercept age of 582 +29/-33 Ma from Baro granite sheets denotes a second high-grade metamorphic event and correlates with the age of Mozambiquean amphibolite-facies metamorphism in northwest Kenya. Late- to post-kinematic plutons at 571 +11/-3 and 541 +10/-16 Ma place a minimum age limit on deformation and metamorphism. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.