Paleomagnetism And Tectonics Of Manda Hararo Rift Of North Afar Ethiopia

This study explains tectonics and Paleomagnetism of Manda Hararo rift in north afar. The fieldrntrip which was organized by scientists from New Zealand, Ethiopia and UK was made to studyrnthe Dabbahu magmatic segment in northern part of Manda Hararo rift. A total of 271 orientedrncore samples were collected for paleomagnetic study from 34 sites within Manda Hararo rift.rnAvailable age data of Basalts from the sampled localities show that the age ranges betweenrn0.09Ma to 1.11Ma. 175 specimens were subjected to progressive Alternating Field (AF)rndemagnetization after routine sample preparation in the laboratory. Almost all specimens showrnfairly simple demagnetization behavior. AF between 0 to 30mT often isolates the firstrncomponent. Median Destructive Field for most specimens ranges between 20 and 35mT,rnsuggesting that Pseudo single domain grains as remnant magnetization carriers. Among 34 sites,rn30 sites show normal polarities and four sites show reversed polarities. The normal and reversedrnpolarities are 1800 apart, showing that the ChRM are free of secondary NRM components.rnMagnetic polarities were found to be coincident with Geomagnetic Polarity Time Scale (GPTS)rnof Cande and Kent (1995). Geomagnetic Polarity Time Scale of Langeries et al., (1997), Lund etrnal., (1998) and Nowaczyk & Frederichs (1999) were used to explain and determine age of thernreversed polarity site PMAF04 from Afdera. The overall mean direction for 33 sites is D=357.10,rnI=10.60 (k=32.6 and α95=4.40). Comparison of observed mean direction with predicted directionrnof Kidane et al., 2003 for stable Africa for ~2Ma (D=359.70, I=16.40, α95=5.70), indicates nornstatistically significant vertical axis rotation has occurred in Manda Hararo rift. Comparison ofrnmean direction from Kori and Saha with the predicted direction of Kidane et al., 2003 indicatesrnthat significant amount of counter clock wise rotation (~5.90±8.60) has occurred. Furtherrncomparison of mean values from the two sites with the Apparent Polar Wander Path curve ofrnBesse and Courtillot, 1991, shows a counter clock wise rotation of 7.10±6.70. This local rotationrnis due to the overlap of Red Sea propagators, Erta’ale-Dader in the east and Erta’ale-MandarnHararo in the west. A reference pole is determined based on 33 sites. It is located at λ=83.10N,rnф=238.80E(α95=4.00).

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