Granulitic metamorphism in the Laouni terrane (Central Hoggar, Tuareg Shield, Algeria) Abderrahmane Bendaoud a, * , Amel Derridj b , Khadidja Ouzegane a , Jean-Robert Kienast c a Faculte ´ des Sciences de la Terre, de Ge ´ographie et dÕAme ´nagement du Territoire, U.S.T.H.B., B.P. 32, Dar el Beida, Algiers, Algeria b Faculte ´ des Hydrocarbures et de la Chimie, Universite ´mÕHamed Bougara, 35000 Boumerde ´s, Algeria c Laboratoire de Pe ´trologie, CNRS UMR 7097 IPGP, Universite ´ de Paris 7, Tour 26-O, 4 place Jussieu, 75252 Paris, France Available online 30 September 2004 Abstract In the Laouni terrane, which belongs to the polycyclic Central Hoggar domain, various areas contain outcrops of formations showing granulite-facies parageneses. This high-temperature metamorphism was accompanied by migmatization and the emplace- ment of two types of magmatic suite, one of continental affinity (garnet pyroxenites and granulites with orthoferrossilite–fayalite– quartz), and the other of arc affinity (layered metanorites). Paragenetic, thermobarometric and fluid-inclusion studies of the migmatitic metapelites and metabasites make it possible to reconstruct the P–T–aH 2 O path undergone by these formations. This path is clockwise in the three studied areas, being characterized by a major decompression (Tamanrasset: 10.5 kbar at 825 °C to 6 kbar at 700 °C; Tidjenouine: 7.5 kbar at 875 °C; to 3.5 kbar at 700 °C; Tin Begane: 13.5 kbar at 850 °C; to 5 kbar at 720 °C), followed by amphibolitization that corresponds to a fall of temperature (from 700 to 600 °C) and an increase in water activity (from 0.2–0.4 to almost 1). The main observed features are in favour of petrogenesis and exhumation related to the Eburnean orogeny. However, the lacks of good-quality dating work and a comparison with juvenile Pan-African formations having undergone high-pressure metamor- phism, in some cases reaching the eclogite facies, do not rule out the possibility that high-temperature parageneses are locally due to Pan-African events. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Laouni; Hoggar; LATEA; Granulite; Eburnean Pan-African 1. Introduction The Central Hoggar is located at the core of the Tua- reg Shield (Fig. 1(A)), providing an example of a Pre- cambrian domain that has undergone a polycyclic history. Indeed, the available dating suggests that this domain consists of Eburnean crust (Paleoprotero- zoic  2000 Ma), including some Archaean zones, onto which juvenile Pan-African (850–550 Ma) material was locally accreted (Lie ´geois et al., 2003; Peucat et al., 2003). Thus, the set of formations in this area corre- sponds to a superposition of Pan-African nappes reworking Archean–Eburnean material to a variable ex- tent. The base of some of these nappes is picked out by relatively well-preserved eclogitic layers. During the Pan-African orogeny (850–550 Ma), to which the region owes its current structure, the Tuareg Shield was built up from the amalgamation of different terranes and was involved in two major collisions, one with the West African Craton and the other with the Saharan Craton (Black et al., 1994). 0899-5362/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jafrearsci.2004.07.050 * Corresponding author. Tel: +213 21 24 76 47; fax: +213 21 24 76 47. E-mail address: abderbendaoud@hotmail.com (A. Bendaoud). www.elsevier.com/locate/jafrearsci Journal of African Earth Sciences 39 (2004) 187–192