Paleomagnetic Investigation of Saha and Surrounding Area Volcanic Rocks, Central Afar, Northeast Ethiopia
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Date
2017-05
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Addis Ababa Universty
Abstract
The paleomagnetic investigation was located in the area of Saha and surrounding area, central
Afar. The paleomagnetic samples were collected from nine lava flow unit outcrop of basalt (Gulf
basalt) which exposed Saha and surrounding area (Central Afar). Five to nine samples were
collected from each lava flow. The specimens conducted to partial demagnetize by using
Alternating field (AF) and Thermal (TH) demagnetization techniques, as well as magnetize by
Impulse magnetizer techniques (IM). The paleomagnetic results were measured by using JR-
6ASpinner Magnetometer from School of Earth Science paleomanetic laboratory in Addis Ababa
University. The Natural Remenant magnetization (NRM) direction explains the specimens which
display components of magnetizations were low stability component (secondary NRM) was
removed by AF about 10mT- 30mT, by heating about 120°C- 300°C were as high stability
components (primary NRM or characteristic remenant magnetization) above these steps and the
vector straight line is directed towards the origin from orthogonal vector diagrams. The results of
magnetization curve plots for magnetic rock analysis shows that magnetic mineralogy dominated
by Ti- poor titanomagnetite, magnetite and few presence of maghemite. Principal component
analysis and site mean direction calculated from both normal and reverse polarities. An overall
mean direction was calculated from 9 individual site mean, the result obtained: D= 352.5°, I=
12.5°, K= 13.2, α95=14.7°, N= 9 and comparison with expected Geomagnetic Axial Dipole
based on Apparent Polar Wander Path curve for 1Ma Mile- Gewane Ali Sabieh, (Kidane et
al.,2003), as stable Africa plate Besse and Courtillot (2002). The mean paleomagnetic pole was
calculated from the combined individual VGP, λ= 80.9°., ф =277.8°. , K = 22.8, α95 =11°. The
declination difference which explains rotation of blocks about vertical axis was: =-7.2 ±6.6;
difference in inclination was: = 3.9±3.2 obtained. This declination difference explains counter
clock wise rotation about vertical axis due to the young propagation rift.
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of Saha and Surrounding