SEMINAR - Tyrone Rooney
My current research concentrates on the Main Ethiopian Rift from the perspective of geochemical and petrographical variation in the central rift. This central zone is considered a key transition zone between the continental rifting to the south and seafloor spreading to the north. My research investigates key magmatic processes associated with this transitional rifting and evaluates geochemical data in an extensive geophysical framework. This synthesis of geochemical, petrographic and geophysical data at this important location is a primary objective of the EAGLE project that sponsors this work.
Abstract
The East African Rift system is the archetypal example of continental rupture and has global significance in understanding extensional plate tectonic processes. We concentrate on the central Main Ethiopian Rift, which lies between the thicker continental crust in Southern Ethiopia and the thin predominately basaltic crust of the Afar Depression. We utilize Quaternary basaltic lavas erupted in tectono-magmatic fault belts to probe the source of rift magmatism and establish a connection between deeper mantle processes ( e.g. mantle plumes) and continental rifting. This study has also focussed on the relationship between magmatic intrusion in the continental lithosphere and extension. These geochemical results are combined with geophysical studies to produce an integrated geodynamic model for the progression of continental rifting along the Main Ethiopian Rift and call into question the concept of a simple transition between continental rifts and sea floor spreading centers.
Tyrone's seminar title: "An integrated approach to continental breakup: insights from central Ethiopia "; Wednesday the 21st of March 2007
The East African Rift system is the archetypal example of continental rupture and has global significance in understanding extensional plate tectonic processes. We concentrate on the central Main Ethiopian Rift, which lies between the thicker continental crust in Southern Ethiopia and the thin predominately basaltic crust of the Afar Depression. We utilize Quaternary basaltic lavas erupted in tectono-magmatic fault belts to probe the source of rift magmatism and establish a connection between deeper mantle processes ( e.g. mantle plumes) and continental rifting. This study has also focussed on the relationship between magmatic intrusion in the continental lithosphere and extension. These geochemical results are combined with geophysical studies to produce an integrated geodynamic model for the progression of continental rifting along the Main Ethiopian Rift and call into question the concept of a simple transition between continental rifts and sea floor spreading centers.
Tyrone's seminar title: "An integrated approach to continental breakup: insights from central Ethiopia "; Wednesday the 21st of March 2007
2 comments:
Structure of the Ethiopian lithosphere: Xenolith evidence in the Main Ethiopian Rift
TYRONE O. ROONEY,1,* TANYA FURMAN,1 GEZAHEGN YIRGU,2 and DEREJE AYALEW2
1Department of Geosciences, The Pennsylvania State University, University Park, PA 16802, USA
2Department of Geology and Geophysics, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia
(Received August 23, 2004; accepted in revised form March 24, 2005)
Abstract—The lithospheric and sublithospheric processes associated with the transition from continental to oceanic magmatism during continental rifting are poorly understood, but may be investigated in the central Main Ethiopian Rift (MER) using Quaternary xenolith-bearing basalts. Explosive eruptions in the Debre Zeyit (Bishoftu) and Butajira regions, offset 20 km to the west of the contemporaneous main rift axis, host Al-augite, norite and lherzolite xenoliths, xenocrysts and megacrysts. Al-augite xenoliths and megacrysts derived from pressures up to 10 kb are the dominant inclusion in these recent basalts, which were generated as small degree partial melts of fertile peridotite between 15 and 25 kb. Neither the xenoliths nor the host basalts exhibit signs of carbonatitic or hydrous (amphibole phlogopite) metasomatism, suggesting that infiltration of silicate melts resulting in pervasive Al-augite dyking/veining dominates the regional lithospheric mantle. Recent geophysical evidence has indicated that such veining/dyking is pervasive and segmented, supporting the connection of these Al-augite dykes/veins to the formation of a proto ridge axis. Al-augite xenoliths and megacrysts have been reported in other continental rift settings, suggesting that silicate melt metasomatism resulting in Al-augite dykes/veins is a fundamental processes attendant to continental rift development. Copyright © 2005 Elsevier Ltd
Full Text
EAGLE
Ethiopia-Afar Geoscientific Lithosphere Experiment
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