HR: 18:05h
AN: GP34A-08    [Abstracts]
TI: Inhomogeneous Shearing Around Major Shear Zone: Evidence From the Magnetic Fabric of Late-Panafrican Plutons in the Tuareg Shield (Algeria)
AU: * Henry, B
EM: henry@ipgp.jussieu.fr
AF: Paleomagnetism, IPGP, 4 avenue de Neptune, Saint-Maur, 94 94107, France
AU: Derder, M E
EM:
AF: CRAAG, BP 63, Bouzareah, Alger, 16340, Algeria
AU: Bayou, B
EM:
AF: CRAAG, BP 63, Bouzareah, Alger, 16340, Algeria
AU: Guemache, M
EM:
AF: CRAAG, BP 63, Bouzareah, Alger, 16340, Algeria
AU: Nouar, O
EM:
AF: CRAAG, BP 63, Bouzareah, Alger, 16340, Algeria
AU: Ouabadi, A
EM:
AF: FSTGAT/USTHB, BP 32, El Alia Bab Ezzouar, Alger, 16111, Algeria
AU: Djellit, H
EM:
AF: CRAAG, BP 63, Bouzareah, Alger, 16340, Algeria
AU: Amenna, M
EM:
AF: CRAAG, BP 63, Bouzareah, Alger, 16340, Algeria
AU: Hemmi, A
EM:
AF: CRAAG, BP 63, Bouzareah, Alger, 16340, Algeria
AB: Teg Orak and Tihaliouine are Late-Panafrican granitic intrusions situated in the Tuareg shield, northwest of Tamanrasset. Both plutons are located close to the 4°50 accident, one of the N-S major shear zone cutting the Hoggar. They are constituted of several granitic facies, indicating differentiation and multiphase intrusion. They show only very locally preferred visible orientation of their minerals. Anisotropy of Magnetic Susceptibility (AMS) was determined on samples collected along cross-sections in the Teg Orak (349 samples for 43 sites) and Tihaliouine (160 samples for 21 sites) plutons. At Tihaliouine, the AMS presents relatively scattered directions, with magnetic foliation having often strike similar to that of the plutons border. At Teg Orak, samples collected in the north-western part of the pluton present also AMS rather in relation with orientation of the pluton border. For all the other samples, including those from an aplitic dyke crossing the granite and whatever the facies of the granite, the fabric is very coherent. Magnetic lineation is subhorizontal, striking NW-SE. Magnetic foliation plunges to the NE on the north-eastern part of the plutons, has a weak dip in the central part and plunges to the SW in the south-western part. This disposition indicates deformation of the eastern part of the granite during late magmatic stages in relation with dextral strike-slip movement along the shear zone. Tihaliouine and western Teg Orak (mainly with fabric related with magma flow) intruded within older granite while eastern part of Teg Orak (with fabric related to deformation) is located within diorites and metamorphic rocks. In the Teg Orak - Tihaliouine area, granitic host-rocks acted therefore as a rigid block, protecting the studied plutons from the effect of regional deformation, while metamorphic and more basic plutonic rocks had a more deformable behavior and allowed intrusion strain.
DE: 1518 Magnetic fabrics and anisotropy
DE: 1525 Paleomagnetism applied to tectonics: regional, global
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly