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Previous paleomagnetic studies performed in the central North-Algeria (Chellif and Mitidja basins) on Neogene formations pointed out tectonic clockwise blocks rotations. This deformation pattern was interpreted as resulting from a bookshelf neotectonics, consequence of the Africa-Eurasia plates convergence. A new paleomagnetic study was conducted on the Neogene volcanic rocks outcropping in the northwestern Algeria (Marset Ben Mhidi, Ain Temouchent, Tifaraouine area). The obtained stable remanent magnetization is mainly carried by Ti-poor titanomagnetite. The paleomagnetic data show that, since the lava emplacement, the northwestern Algeria underwent a mean moderate clockwise block rotation of 9.3° ± 4.5°. For the Algerian margin, this confirms a context of transpression and blocks rotations in a strike-slip tectonic setting. A decreasing deformation gradient from the E to the W affected the different basins of this margin, from strong rotations within the Mitidja, to the moderate ones in the Chellif and to Marset Ben Mhidi, Ain Temouchent, Tifaraouine area, where rotation magnitudes are significantly lower.

International audience; The present day architecture of the Western Mediterranean mainly results from the interplay of different litho-spheric plates and the Cenozoic consumption of various branches of the Alpine Tethys and Neo-Tethys Oceans.Identifying relicsofthese oceanic domains inthe peri-Mediterranean belts enables pinpointing the earlieststagesof this evolutionary framework. In NE Algeria, the Kef Lakhal Complex (Edough Massif) is composed of amphib-olites and meta-gabbros metamorphosed under amphibolite facies conditions and thrust onto the northernAfrican margin during earliest Miocene. Geochemical analyses reveal that amphibolites and metagabbros havemajor and trace element signatures characteristic of tholeiitic basalts and gabbros and display N-MORB (La/SmN=0.7–0.9) toE-MORB (La/SmN=1.1–1.2) affinities. Enrichments in U and alkalis (Cs, Rb) and high87Sr/86Sriratios on bulk rocks and minerals (up to 0.70856) are typical of seawater alteration and indicate thatthe Kef Lakhal Complex represents a piece of altered oceanic crust. Parental magmas were derived from a De-pleted Mantle source (WRεNdi= 8.2–9.9 andεHfi= 10.4–14.4) that preserved some canonical MORB ratios(Ti/Eu = 5700–7600 and Y/Ho = 27.4–29.0), but which was contaminated by a component akin to recycled oce-anic crust and associated sediments (Ce/Pb = 10.5–22.2;206Pb/204Pbi=18.41–18.74;207Pb/204Pbi=15.49–15.59;208Pb/204Pbi=37.73–38.37). The sedimentary component is consistent with a volcaniclastic originand substantiatesanintra-oceanic setting.The geochemicalcharacteristics oftheKef Lakhalrocksare comparableto present day (Mariana, W Pacific Ocean) or fossil (Xigaze, SE Tibet) fore-arc oceanic crust. An overview of theWestern Mediterranean geodynamic indicates that the most likely period for initiating formation of a fore-arccorresponds either to the Early/Late Cretaceous or to the Middle Eocene.40Ar/39Ar dating on amphibole furtherindicate that after thrusting onto the African margin, the Kef Lakhal Complex cooled down toc.550 °C at18.14 ± 0.27 Ma (2σ).

International audience; In North Africa, the Algerian margin is made of basement blocks that drifted away from the European margin, namely the Kabylia, and docked to the African continental crust in the Early Miocene. This young margin is now inverted, as dated Miocene (17 Ma) granites outcrop alongshore, evidencing kilometre-scale exhumation since their emplacement. Age of inversion is actually unknown, although Pliocene is often considered in the offshore domain. To decipher the exhumation history of the margin between 17 and 5 Ma, we performed a coupled apatite fission track (AFT) and (U-Th-Sm)/He (AHe) study in the Cap Bougaroun Miocene granite. AFT dates range between 7 +/- 1 and 10 +/- 1 Ma, and mean AHe dates between 8 +/- 2 and 10 +/- 1 Ma. These data evidence rapid and multi-kilometre exhumation during Tortonian times. This event cannot be related to slab break-off but instead to the onset of margin inversion that has since developed as an in-sequence north-verging deforming prism.

International audience; Miocene (17-11 Ma) magmatic activity in the Kabylies emplaced K-rich (and minor medium-K) calc-alkaline plutonic and volcanic rocks in five zones, delineating a ∼450 km long EW trending strip located along the northern coast of Algeria, between Annaba and Algiers. Their most likely source is the Kabylian subcontinental lithospheric mantle previously metasomatized during the Paleogene subduction of the Tethys oceanic lithosphere. Our preferred tectono-magmatic model involves a Tethyan slab detachment combined with African mantle delamination and crustal stacking, leading to the superimposition of the African continental crust over the Kabylian metasomatized lithospheric mantle. At ca. 17 Ma, the asthenospheric upwelling arising from lithospheric delamination and Tethyan slab tear triggered the thermal erosion of the latter mantle, inducing its partial melting. The corresponding mafic medium-K calc-alkaline magmas interacted with the African basement units during their ascent, generating intermediate to felsic K-rich calc-alkaline melts that display a characteristic trace element and isotopic crustal signature. Later on, slab tears propagated eastward and westward, promoting slab rollback perpendicular to plate convergence and inducing the emplacement of magmatic rocks of decreasing ages from central-eastern Algeria towards Tunisia and Morocco.

Miocene K-rich calc-alkaline magmatic rocks are exposed over a ~ 150 km2 area in Cap de Fer and West Edough, along the NE Algerian Mediterranean coast. They include andesitic pyroclastic and lava flows, small dioritic plutons, and large microgranodioritic intrusions that intrude and/or overlie Miocene sediments. New 40K-40Ar ages obtained on the igneous rocks range from 16.84 ± 0.58 to 12.91 ± 0.31 Ma and define three successive magmatic pulses at ~ 16.5, ~ 15, and ~ 13 Ma. These data are in good agreement with biostratigraphic data obtained on the Miocene marls that yielded Langhian (N8 biozone) to Late Langhian-Serravallian ages (N9–N10 biozones). This consistency suggests that the time span (~ 3.5 m.y.) deduced from K-Ar datings is not due to perturbations of the K-Ar clock; it is more likely related to long-lasting tectono-magmatic processes. According to the regional context (“no-slab” area), these processes result from the uprise of hot asthenospheric mantle through the tear generated by the detachment of the oceanic part of the African slab beneath the Algerian margin that triggered the partial melting of the overlying metasomatized lithospheric mantle of the Kabylides.

The high-level sub-circular North Tihimatine granitic pluton, intrusive in the In Ouzzal terrane, has been dated at 600 ± 5 Ma (LA-ICP-MS U–Pb zircon) and at 602 ± 4 Ma (SHRIMP U–Pb zircon). At this time, while Tihimatine intruded a brittle In Ouzzal without major metamorphism, large high-K calc-alkaline granitoid batholiths emplaced in the adjacent terranes under ductile conditions and regional amphibolite facies metamorphism. Outside In Ouzzal, high-level plutons emplaced under brittle conditions are known only at c. 580 Ma. The In Ouzzal terrane (500 km × 80 to 5 km), made of c. 2 Ga very high-temperature granulitic lithologies with Archean protoliths, is the sole terrane within the Tuareg Shield to have been largely unaffected by the Pan-African orogeny. The field, petrographic, geochemical and isotopic characteristics of the In Ouzzal granitic plutons studied herein, give keys for the understanding of the atypical behavior of the In Ouzzal terrane. The In Ouzzal Pan-African granitoids present chemical compositions varying from medium-K to high-K calc-alkaline to alkaline compositions. This is recorded by the Sr and Nd radiogenic isotopes (−4 < ɛNd < −30; 0.704 < ISr < 0.713), pointing to a mixing between a heterogeneous and old Rb-depleted source, the Eburnean granulitic In Ouzzal crust, and a Pan-African mantle. The latter is represented by the nearby bimodal Tin Zebane dyke swarm (ɛNd = +6.2, ISr = 0.7028; Hadj Kaddour et al. in Lithos 45:223–243, 1998), emplaced along the mega-shear zone bounding the In Ouzzal terrane to the west. Trace element composition and Sr–Nd isotope modeling indicate that 20–40% of different crustal lithologies outcropping in the In Ouzzal terrane mixed with mantle melts. At least two, most probably three, Eburnean granulitic reservoirs with Archean protoliths are needed to explain the chemical variability of the In Ouzzal plutons. The Pan-African post-collisional period is related to a northward tectonic escape of the Tuareg terranes, including the rigid In Ouzzal terrane, bounded by major shear zones. Blocking of the movement of the In Ouzzal terrane, which occurred 20 Ma earlier (at 600 Ma) on the western side than on the eastern side, induced its fracturing along oblique faults inside the terrane. This process allowed asthenosphere to rise and to locally melt the In Ouzzal crust, giving rise to the studied plutons. This corresponds to a metacratonization process. The In Ouzzal terrane demonstrates that a relatively small rigid block can survive within a major orogen affected by a post-collisional tectonic escape at the cost of a metacratonization, particularly at depth along faults.

The magnetic fabric obtained in the Hoggar shield on several plutons is related to various origins: simple flow, syn-deformation flow, stress field during late-magmatic stage and solid-state deformation. These results also evidenced the important role of hosting frame, acting as a more or less efficient “protection” against the effects on the magnetic fabric of the regional stress field. Combined studies, on neighboring sites of the main intrusion and of late-magmatic dykes crosscutting it, yield key-arguments about the acquisition age of this fabric. P′(Km) diagrams clearly highlight the strain gradient in plutons very close to shear zones. The fact that K1 axis is mainly a mineral lineation, at least in three plutons, is evidenced by the determination of the magnetic zone axis. The plutons AMS is associated with different Pan-African stages in the Hoggar: gneissification of Eburnean plutons, syn-thrust pluton emplacement, pluton emplacement under regional shearing context. Accordingly, the main movements along the major shear zones, related to the oblique collision of the Hoggar shield with the West African Craton, are contemporaneous of the first stages. Shearing context during the following period points out that this collision had still active effects, probably associated with a progressive change in orientation of the continental convergence.

In Ordovician and Silurian sedimentary formations of the Murzuq basin (Saharan platform, Algeria), different remagnetization processes have been highlighted. These magnetic overprints totally replaced the primary magnetization. They are mainly due to chemical phenomena. Even in a site affected by contact metamorphism during Devonian, chemical changes, associated to the acquisition of the thermo-remanent overprint, were important, affecting the characteristics of the magnetite grains. In the remaining sites, remagnetizations of Cenozoic age have also a chemical origin and are carried by magnetite as well as by hematite. Contrary to what is generally deemed, these remagnetizations processes appeared limited to very short duration of acquisition, and to very local geographical extension.

To improve paleocontinental reconstructions, paleomagnetic reference curves (Apparent Polar Wander Path: APWP) feature for large continents have to be continuously refined by adding up new high-quality data. For stable Africa, the Moscovian period was favorable for such aim, with well-dated and widespread geological formations. A new study has been conducted in the Upper “Dembaba” geological formation of Lower Moscovian age outcropping in the western part of the “Murzuq” basin (Saharan platform). Well-defined ChRMs, combined with remagnetization circles data, both constrained in age by a positive fold test, yield a new significant paleomagnetic pole (λ = 25.2°S, ϕ = 59.9°E, K = 55, A95 = 5.4°). When joined with previous African data of the same age, it gives an improved reference pole for Africa (λ = 28.9°S, ϕ = 54.5°E, K = 106, A95 = 3.6°). The Mean Moscovian paleomagnetic pole determined from an updated Gondwana Paleozoic APWP (λ = 29.4°S, ϕ = 51.5°E, K = 11, A95 = 1.8°), associated with the corresponding Laurussia pole ( Domeier et al., 2012 ), yields a more constrained paleocontinental reconstruction for 310 Ma.

International audience; The eastern Alboran basin and its transition to the Algerian basin is a key area in the Mediterranean realm where controversial kinematic and geodynamical models are proposed. Models imply striking differences regarding the nature of the crust, the prevalence of brittle faulting and ductile shear, the origin of magmatism, the style of Miocene deformation and the driving mechanisms of the Alboran plate kinematics. Combining a new chronostratigraphic chart of the Alboran and Algerian basins based on the Habibas (HBB-1) core drill, deep seismic sections striking WSW-ENE and SSE-NNW, and potential field data, we re-assess the tectonic evolution that controlled the sedimentation and basement deformation of the westernmost limit of the Algerian basin and its transition with the Alboran domain. A WSW-directed extensional tectonic phase has shaped a stretched continental crust with typical tilted blocks along ∼100 km from Burdigalian to Tortonian times, which is assumed to result from the WSW-directed migration of the Alboran block driven by a narrow slab rollback. In the Algerian basin, this event was followed by the emplacement of an oceanic-type crust. Potential field signatures of the deep basin as well as geometrical correlations with onland outcrops of inner zones suggest a minimum WSW-directed displacement of the Alboran terrane of ∼200 km. At the southern foot of the Algerian basin, the continent-ocean transition is sharp and may result from the westward propagation of a slab tear at depth, forming two segments of STEP (Subduction-Transform Edge Propagator) margins. Our results support models of intense shear tractions at the base of an overriding plate governed by slab rollback-induced mantle flow. Finally, Messinian salt tectonics affected overlying deposits until today. A late Tortonian to Quaternary dominantly transpressive tectonic episode linked to the Africa-Iberia convergence post-dates previous events, deforming the whole margin.

The arch-and-basin geometry that characterizes North Africa was achieved at the end of Paleozoic times. It has been subsequently reactivated during the Mesozoic-Cenozoic with, in particular, the development of large topographic anomalies. Among these, the Tuareg Shield forms a topographic high in which the Pan-African basement reaches 2400 m above sea level (Hoggar core). While Cretaceous sedimentary remnants suggest a possible stage of subsidence during the Mesozoic, currently the area forms a swell, emphasized by Cenozoic volcanic episodes since 35 Ma. In this context, we present the first apatite (U-Th)/He thermochronological data acquired across this swell, with mean ages ranging from 78 ± 22 Ma to 13 ± 3 Ma. These results demonstrate the existence of a widespread Eocene exhumation of the shield before volcanic activity began, which reflects large-scale vertical processes. In the northeastern part of the swell, Cretaceous continental sedimentary remnants unconformably lying on the basement close to our samples evidence that they were near the surface at that time. This study shows that basement rocks have undergone subsequent heating at ∼60–80 °C, suggesting a burial of more than 1 km after the Early Cretaceous. This conclusion can be possibly extended over the whole Tuareg Shield.

International audience; The ultramafic rocks of the Collo region in northeastern Algeria crop out as “stratified” masses that cut across older metamorphic formations of the Petite Kabylie basement. Based on petrological compositions and mineralogical observations, these rocks are mainly peridotites and serpentinites. The peridotites are identified as lherzolites, but dunites may occur rarely. The lherzolites are composed of olivine, orthopyroxene, clinopyroxene and chromian spinel. Their chemical composition shows high MgO (34.4–37.5 wt%), Cr (0.14–0.27 wt%), Ni (0.14–0.26 wt%) and Co (34–133 ppm) contents and low CaO and Al2O3 concentrations (0.02–2.2 wt% and 0.5 to 2.8 wt%, respectively). The chromite, which represents approximately 1–3% of the rock, is ubiquitous and shows two different generations: primary millimetric euhedral crystals and secondary fine xenomorphic grains and interstitial aggregates. The primary chromites are alumino-ferro-magnesian crystals that show high Al2O3 (25.77%–27.36%) and MgO (10.70%–13.36%). Cr# (100 × Cr/(Al + Cr)) ranges from 45 to 48, and Mg# (100 × Mg/(Mg + Fe2+)) from 49 to 59. The secondary interstitial grains are iron-rich chromites. They show low Al2O3 (4.67%–9.54%) and MgO (4.60%–4.65%). Cr# is relatively high (77–88), whereas Mg# shows relatively low values, ranging from 22 to 25. Primary chromite and whole-rock chemistry show that the Collo ultramafic rocks belong to Alpine-type peridotites that were emplaced within an orogenic setting. The oxygen isotopic composition of both peridotites and chromites is consistent with their derivation from a mantle source (δ18O ranges from +3.0 to +5.9‰). Low δ18O values (

Diamond-bearing UHP metamorphic rocks witness for subduction of lithospheric slabs into the mantle and their return to shallow levels. In this study we present U–Pb and trace elements analyses of zircon and rutile inclusions from a diamond-bearing garnet megacryst collected in a melange unit exposed on the northern margin of Africa (Edough Massif, NE Algeria). Large rutile crystals (up to 300 μm in size) analyzed in situ provide a U–Pb age of 32.4 ± 3.3 Ma interpreted as dating the prograde to peak subduction stage of the mafic protolith. Trace element analyses of minute zircons (≤30 μm) indicate that they formed in equilibrium with the garnet megacryst at a temperature of 740–810 °C, most likely during HP retrograde metamorphism. U–Pb analyses provide a significantly younger age of 20.7 ± 2.3 Ma attributed to exhumation of the UHP units. This study allows bracketing the age of UHP metamorphism in the Western Mediterranean Orogen to the Oligocene/early Miocene, thus unambiguously relating UHP metamorphism to the Alpine history. Exhumation of these UHP units is coeval with the counterclockwise rotation of the Corsica–Sardinia block and most likely resulted from subduction rollback that was driven by slab pull.

article i nfo In this paper, we show with examples that cratons involved in intercontinental collisions in a lower plate position are often affected by orogenic events, leading to the transformation of their margins. In some cases, craton interiors can also be shaped by intense collisional processes, leading to the generation of intra- cratonic orogenic belts. We propose to call these events "metacratonization" and the resulting lithospheric tract "metacraton". Metacratons can appear similar to typical orogenic belts (i.e. active margin transformed by collisional processes) but are actually sharply different. Their main distinctive characteristics (not all are present in each metacraton) are: (1) absence of pre-collisional events; (2) absence of lithospheric thickening, high-pressure metamorphism being generated by subduction, leading to high gradient in strain and meta- morphic intensity; (3) preservation of allochthonous pre-collisional oceanic terranes; (4) abundant post- collisional magmatism associated with shear zones but not with lithospheric thickening; (5) presence of high-temperature-low-pressure metamorphism associated with post-collisional magmatism; (6) intraconti- nental orogenic belts unrelated to subduction and oceanic basin closures. Reactivation of the rigid but fractured metacratonic lithosphere will cause doming, asthenospheric volcanism emplacement, and mineral- izations due to repetitive mineral enrichments. This paper provides several geological cases exemplifying these different metacratonic features in Scandinavia, Sahara, Central Africa and elsewhere. A special focus is given to the Saharan Metacraton because it is where the term "metacraton" originated and it is a vastly ex- panded tract of continental crust (5,000,000 km 2

International audience; Bougaroun is the largest pluton (~ 200 km2) in the 1200 km-long Neogene magmatic belt located along the Mediterranean coast of Maghreb. New U–Pb dating on zircons and K–Ar ages on whole rocks and separated minerals document its emplacement at 17 Ma within the Lesser Kabylian basement, a continental block that collided with the African margin during the Neogene. This Upper Burdigalian intrusion is therefore the oldest presently identified K-rich calc-alkaline massif in the whole Maghrebides magmatic lineament and marks the onset of its activity. The Bougaroun peraluminous felsic rocks display a very strong crustal imprint. Associated mafic rocks (LREE-enriched gabbros) have preserved the “orogenic” (subduction-related) geochemical signature of their mantle source. Older depleted gabbros cropping out at Cap Bougaroun are devoid of clear subduction-related imprint and yielded Ar–Ar hornblende ages of 27.0 ± 3.0 Ma and 23.3 ± 3.2 Ma. We suggest that they are related to the Upper Oligocene back-arc rifted margin and Early Miocene oceanic crust formation of the nearby Jijel basin, an extension of the Algerian basin developed during the African (Tethyan) slab rollback. The fact that the Bougaroun pluton intrudes exhumed Kabylian lower crustal units, mantle slices and flysch nappes indicates that the Kabylian margin was already stretched and in a post-collisional setting at 17 Ma. We propose a tectono-magmatic model involving an Early Miocene Tethyan slab breakoff combined with delamination of the edges of the African and Kabylian continental lithospheres. At 17 Ma, the asthenospheric thermal flux upwelling through the slab tear induced the thermal erosion of the Kabylian lithospheric mantle metasomatized during the previous subduction event and triggered its partial melting. We attribute the strong trace element and isotopic crustal signature of Bougaroun felsic rocks to extensive interactions between ascending mafic melts and the African crust underthrust beneath the Kabylie de Collo basement.

International audience; The Algerian offshore is part of the southern margin of the western Mediterranean Sea. The western part of this offshore area represents the transitional margin between the South Algero-Balearic Basin and the Alboran Basin. The study area includes the southern and eastern parts of the Alboran Basin and the northwestern part of the Algerian margin and is in the western part of the plate boundary between Eurasia and Africa (Figure 1). The Yusuf-Habibas Ridge is a major EW-striking structure of this complex plate boundary, separating the eastern and southern parts of the Alboran Basin from the South Algero-Balearic Basin (Martinez-Garcia et al., 2011, and references therein). The ridge played an important role during the Neogene Alboran westward block migration between the Africa and Iberia plates, while the Kabylies blocks migrated southward and accreted to Africa. Furthermore, the ongoing NW-SE convergence between Africa and Iberia has induced a new stress field, since 7 Ma ago, replacing an earlier stress field (Fernandez-Ibañez et al., 2007) and leading to reactivation and polyphased deformation on the main structures in the basin, including the Yusuf-Habibas Ridge.

This study describes the deformation in zones affected by regional shearing, and its relation with local factors, in particular rock compositions. The Tihaliouine and Teg Orak plutons were emplaced close to a major shear zone of the Tuareg shield. Their magmatic to sub-magmatic fabrics were determined by using measurements of anisotropy of magnetic susceptibility; they are similar to those of some other late Panafrican plutons of the Tuareg shield. The eastern part of the Teg Orak pluton displays a coherent fabric with a subhorizontal lineation oblique to the 4°50 major shear zone located just to the east. This fabric is clearly related to shearing by a dextral strain-slip movement along the shear zone during magma crystallization. The fabric in the western part of the Teg Orak pluton and in the Tihaliouine massif presents much more scattered principal axes. It was much less affected by shearing along the shear zone. This difference strongly depends on the nature of the host-rocks: Granitic host-rocks around the Tihaliouine and the western part of the Teg Orak acted as a rigid block, protecting the intrusions from regional deformation, while basic plutonic and metamorphic host-rocks around the eastern part of the Teg Orak pluton had a more plastic behavior and transmitted the regional strain to the intrusion.

The Temaguessine high-level subcircular pluton is intrusive into the LATEA metacraton (Central Hoggar) Eburnian (2 Ga) basement and in the Pan-African (615 Ma) granitic batholiths along a major NW–SE oriented major shear zone. It is dated here (SHRIMP U–Pb on zircon) at 582 ± 5 Ma. Composed of amphibole–biotite granite and biotite syenogranite, it comprises abundant enclaves: mafic magmatic enclaves, country-rock xenoliths and remarkable Fe-cordierite (#Fe = 0.87) orbicules. The orbicules have a core rich in cordierite (40%) and a leucocratic quartz–feldspar rim. They are interpreted as resulting from the incongruent melting of the meta-wacke xenoliths collapsed into the magma: the breakdown of the biotite + quartz assemblage produced the cordierite and a quartz–feldspar minimum melt that is expelled, forming the leucocratic rim. The orbicule generation occurred at T < 850� and P < 0.3 GPa. The Fe-rich character of the cordierite resulted from the Fe-rich protolith (wacke with 4% Fe2O3 for 72% SiO2). Strongly negative eNd (� 9.6 to � 11.2), Nd TDM model ages between 1.64 and 1.92 Ga, inherited zircons between 1.76 and 2.04 Ga and low to moderately high ISr (0.704–0.710) indicate a Rb-depleted lower continental crust source for the Temaguessine pluton; regional considerations impose however also the participation of asthenospheric material. The Temaguessine pluton, together with other high-level subcircular pluton, is considered as marking the end of the Pan-African magma generation in the LATEA metacraton, resulting from the linear delamination along mega-shear zones, allowing asthenospheric uprise and melting of the lower continental crust. This implies that the younger Taourirt granitic province (535– 520 Ma) should be considered as a Cambrian intraplate anorogenic event and not as a very late Pan-African event. � 2007 Elsevier Ltd. All rights reserved.

The Late Panafrican evolution of the Hoggar shield is characterized by emplacement of magmatic intrusions and by occurrence of major shear zones separating different terranes. In Telloukh granite is close to the In Guezzam faults (western border of the Tin Serririne basin). Analysis of its visible and magnetic fabrics suggests an emplacement mode and deformation that are not related to the In Guezzam faults, but most likely to a N–S compression, an event not yet identified. Dioritic dykes crosscutting the granite have a very different magnetic fabric, which is related on the contrary to dextral strike-slip movements along the In Guezzam faults. In both cases, no visible fabric can be correlated with the magnetic fabric, which has been likely acquired during late magmatic stages. This magnetic fabric was not significantly affected by the tectonic events that took place after entire crystallization of the magma. The In Guezzam faults and the major 7°30 and 4°50 shear zones are close to intrusions such as In Telloukh dykes and the Alous En Tides and Tesnou plutons where quite similar magnetic fabrics are observed, all related with dextral strike-slip movements along these structures.

The Tuareg Shield, to which Hoggar (southern Algeria) belongs, has a swellshaped morphology of lithospheric scale of ~1000 km in diameter linked to Cenozoic volcanism occurring in several regions, including Atakor, the center of the swell, which reaches nearly 3000 m in altitude. The lack of high-resolution geophysical data for constraining its deep structure is at the origin of a controversy about its innermost nature and about the origin of the Cenozoic volcanism. During the course of this study, magnetotelluric (MT) broadband data were collected at 18 sites forming a northeast-southwest profi le 170 km long within the Atakor region. The electrical resistivity model obtained by inverting the magnetotelluric data reveals lithospheric structure down to a depth of ~100 km. From this depth to the surface, the model does not show any regional anomaly that may result from a metasomatized lithosphere or from an asthenospheric upwelling, including a mantle plume. MT data reveal rather a lithosphere affected by a set of rather thin subvertical conductors that can be attributed to the electrical signature of some known shear zones resulting from the Pan-African evolution of the LATEA metacraton, which globally corresponds to the uplifted Central Hoggar swell. The main anomaly is deeply rooted in the lithosphere and underlies the Atakor-Manzaz volcanic districts. As a whole, MT data are therefore properly integrated within the hypothesis of the reactivation of shear zones due the intraplate deformation related to the collision between Africa and Europe since the Eocene, applied onto the metacratonic region.

Âge 40K/40Ar, Carbonifere inferieur, du magmatisme basique filonien du synclinal paleozoique de Tin Serririne, Sud-Est du Hoggar (Algerie) Lower Carboniferous 40K/40Ar dating of intrusive basic magmatism of the Paleozoic syncline of Tin Serririne, southeastern Hoggar (Algeria) Les series primaires des Tassilis Oua-n-Ahaggar (Sud-Est du Hoggar) exposent, dans le synclinal de Tin Serririne, des passees magmatiques basiques alcalines. Le leger metamorphisme de contact qui affecte la couche les recouvrant et des etudes d'anisotropie de susceptibilite magnetique de ces dolerites ont permis de preciser que ces dernieres correspondaient a des sills et a des dykes. Les datations 40K/40Ar d'un echantillon sur roche totale et sur feldspaths separes et de deux autres echantillons sur roche totale se recoupent a Click to view the MathML source (pour Click to view the MathML source), indiquant de ce fait un âge qui correspond au Carbonifere inferieur (Tournaisien). La prise en compte de l'âge de ce magmatisme et des donnees stratigraphiques et structurales sur ce secteur suggerent une mise en place de ces magmas au cours d'une distension liee au rejeu d'accidents tardi-panafricains. Pour citer cet article : H. Djellit et al., C. R. Geoscience 338 (2006).

Miocene igneous rocks (diorites, andesites, dacites, rhyolites and microgranites) of Chetaibi and Cap de Fer massif, NE Algeria, are high-K calc-alkaline to shoshonitic rocks. Fresh diorites have δ34S and δ18O values ranging between −2.5‰ and +5.9‰, +6.5‰ and +6.7‰ respectively, indicating a mantle origin. The relatively low δ34S values (−5.4‰ to −12.2‰) and high δ18O (+8.3‰ to +9.0‰) of altered diorites indicate the input of a crustal component to the initial magma. The microgranites’ I-type signature is indicated by the geochemical data and the δ34S and δ18O values of −1.2‰ and −3.6‰, and +7.8‰ to +10.4‰ respectively. The andesites show a large variation of δ34S, between −33.2‰ and +25.7‰. Massive andesites with δ34S between +6.8‰ and +7.6‰ preserve a 34S-enriched mantle signature. The δ34S of the lava flows between +25.7‰ and +25.8‰ are attributed to open system magma degassing, whereas the low δ34S of two andesitic dyke samples (−13.7‰ and −33.2‰) strongly suggest a crustal sulphur input. High δ18O (+9.2‰ to +15.7‰) of andesites indicate post-magmatic alteration (mainly silicification); the flyschs with δ18O between of +13.3‰ and +21.7‰ are most likely the contaminant. Quartz veins within the andesites gave a δ18O value of +23.0‰ while silica-filling vesicles yielded a value of +13.8‰. Initial Sr-isotope data are rather high for all the rocks (diorites: 0.707–0.708, andesites: 0.707–0.710, and microgranites and rhyolites: 0.717–0.719), and because geochemical and stable isotope data do not indicate a substantial amount of crustal assimilation, an extensive enrichment of the mantle source by subducted sediments is called for. A metasomatized-mantle source, characterized by high radiogenic Sr and relatively high δ18O, has also been indicated for the genesis of similar Tertiary igneous rocks in the Western Mediterranean basin, e.g. the Volcanic Province of southeasten Spain [Benito, R., Lopez-Ruiz, J., Cebria, J.M., Hertogen, J., Doblas M., Oyarzun, R., Demaiffe, D., 1999. Sr and O isotope constraints on source and crustal contamination in the high-K calc-alkaline and shoshonitic neogene volcanic rocks of SE Spain. Lithos 46, 773–802] and some plutons of northeastern Algeria [Ouabadi, A., 1994. Petrologie, geochimie et origine des granitoides peralumineux a cordierite (Cap Bougaroun, Beni-Touffout et Filfila), Algerie nord-orientale. These de Doctorat, Universite de Rennes I, France, 257p; Fourcade, S., Capdevila, R., Ouabadi, A., Martineau, F., 2001. The origin and geodynamic significance of the Alpine cordierite-bearing granitoids of northern Algeria. A combined petrological, mineralogical, geochemical and isotopic (O, H, Sr, Nd) study. Lithos 57, 187–216].

The Alous-En-Tides pluton intruded within one of the most important Late Panafrican N–S shear zones, the 7°30 shear zone in the southern Hoggar shield. A magnetic fabric study points out strong preferred orientations of the magnetite grains. The orientation is coherent in the whole massif. However it cannot be correlated with any of the visible structures in the field or in thin section. Strongly oriented magnetites are thus disseminated within all the rock. The main rock-forming minerals in this pluton were not preferably oriented during their crystallization, showing that magma was emplaced without strongly oriented stresses. Magnetite orientations on the contrary reflect a strong stress field. Strike-slip movements along the 7°30 shear zone probably generated local relative distension, allowing pluton emplacement. During the last magmatic phase, they put the intrusion under the regional compressional stress field, causing orientation of the magnetite. The magnetic fabric then reveals the regional ENE–WSW stress field during Late Panafrican times. In part of the pluton, which was later affected by very intense solid-state deformation during dextral movement, the magnetic fabric remains mainly in connection with this initial magnetite fabric.

The Anfeg batholith (or composite laccolith) occupies a large surface (2000 km 2 ) at the northern tip of the Laouni terrane, just south of Tamanrasset in Hoggar. It is granodioritic to granitic in composition and comprises abundant enclaves that are either mafic microgranular enclaves (MME) or gneissic xenoliths. It intruded an Eburnian (� 2 Ga) high-grade basement belonging to the LATEA metacraton at approximately 608 Ma (recalculated from the U–Pb dating of [Tectonics 5 (1986) 955]) and cooled at approximately 4 kbar, with a temperature of about 750 � C. This emplacement occurred mainly along subhorizontal thrust planes related to Pan-African subvertical mega-shear zones close to the attachment zone of a strike-slip partitioned transpression system. Although affected by some LILE mobility, the Anfeg batholith can be ascribed to a high-K calc-alkaline suite but characterized by low heavy REE contents and high LREE/HREE ratios. The MME belong to the Anfeg magmatic trend while some xenoliths belong to Neoproterozoic island arc rocks. The Anfeg batholith defines a Nd–Sr isotopic initial ratios trend (eNd/( 87 Sr/ 86 Sr)i from )2.8/0.7068 to )11.8/0.7111) pointing to a mixing between a depleted mantle and an old Rb-depleted granulitic lower crust. Both sources have been identified within LATEA and elsewhere in the Tuareg shield (eNd/ 87 Sr/ 86 Sr)i of +6.2/0.7028 for the depleted mantle, )22/0.708 for the old lower crust. The model proposed relates the above geochemical features to a lithospheric delamination along the subvertical mega-shear zones that dissected the rigid LATEA former passive margin without major crustal thickening (metacratonization) during the general northward tectonic escape of the Tuareg terranes, a consequence of the collision with the West African craton. This delamination allowed the uprise of the asthenosphere. In turn, this induced the melting of the asthenosphere by adiabatic pressure release and of the old felsic and mafic lower crust due to the high heat flow. A gradient in the mantle/crust ratio within the source of the Pan-African magmatism is observed in LATEA from the northeast (Eg�� terrane) where rare plutons are rooted within the Archaean/Eburnian basement to the southwest (Laouni terrane) where abundant batholiths, including Anfeg, have a mixed signature. Some mantle melts with only slight crustal contamination (Laouni troctolitic layered intrusions) are even present. This suggests that the southern boundary of LATEA microcontinent is not far south of the Tuareg shield. � 2003 Elsevier Ltd. All rights reserved.

The petrogenesis of igneous, metamorphic and mineralized rocks in the Edough massif, NE Algeria, indicates an interplay between crustal and magmatic sources, and magmatic and surface fluids, as determined by sulphur and oxygen isotopic analyses. The Tertiary igneous rocks (microgranites and rhyolites) show a tendency towards I-type granitoids with δ34S values of +5.4±2.2‰ (1σ) and δ18O between +5.6‰ and +6.9‰, with the most hydrothermally altered rocks having the lowest δ18O values. This is indicative of seawater being a major component of the hydrothermal fluids. Seawater interaction with the granitoids produced enrichment in 34S of sulphide-sulphur in both the microgranites and associated skarn mineralization. However, in the Beleleita W–Sn–(Au) deposit, magmatic fluids dominated the mineralization, reflected by δ34S values of +1.7‰ and +1.8‰. The basement amphibolites of Kef Lakhal indicate derivation from a basaltic magma with δ18O ranging from +4.9‰ to +8.6‰. Locally altered amphibolite has the lowest δ18O values suggestive of meteoric water interaction, whereas the highest δ18O indicate the incorporation of crustal material during the genesis of the amphibolites. Crustal contamination is also reflected in their δ34S of −18‰ to +2.1‰, with the most contaminated rocks having the lowest δ34S. Host Palaeozoic mica schists with δ18O of +12.7‰ and δ34S of −13.2‰ and associated marbles (δ34S −9.9‰ to −17.4‰) are thought to be the most likely contaminants. At the Ain Barbar Fe–Cu–Pb–Zn deposit, δ34S values range between −9.6‰ and −10.8‰, indicating that the sulphide-sulphur and base-metals were likely leached from the host Cretaceous flysch and/or the underlying mica schists, with local Tertiary magmatic rocks providing the heat for local convection cells. At Boumaiza Fe-deposit, δ34S values of the sulphide-sulphur extend from −1.2‰ to −8.1‰ indicative of magmatic sulphur with the incorporation of substantial amounts of sulphur derived from the host mica schists.

International audience; We report for the first time the discovery of diamond inclusions (5–30 μm in size), identified by Raman spectroscopy and the characteristic sharp band at 1332 cm− 1 for crystalline diamond, in a garnet megacryst (≥ 5 cm) from the Edough Massif (NE Algeria). The garnet is adjacent to actinolite and ultramafic boudins and slices of marbles that are inserted within a major mylonite–ultramylonite band. This tectonic contact sharply delineates the Kef Lakhal oceanic unit from the granite-gneiss core below. The host garnet is almandine-dominant and is rich in exsolution of acicular rutile needles. Major and trace elements show a gradual but significant zonation from core to rim, and a sharp increase in grossular component in the rim. Trace element analyses of prismatic rutile inclusions up to 300 μm in size indicate that the host metamorphic rock was a mafic protolith of MORB affinity. The Zr-in-rutile thermometry indicates a temperature range of 724–778 °C that we relate to rutile growth, either during prograde metamorphism or under peak UHP metamorphic conditions of ≥ 3.6 GPa that were reached during subduction of the UHP-rock precursors. We suggest that the mafic protolith originates from the subducted retreating Calabrian branch of the Tethyan slab, that broke or tore, and which fragments were dragged upward and thrust onto the North African margin along with the Kef Lakhal unit, shortly followed by formation of the Edough dome and opening of the Algerian basin.

In northern Algeria, the coastal area displays a very variegated magmatism of Miocene age, extending E–W over 900 km with a width of less than 50 km. This magmatism includes both plutonic and volcanic massifs containing basic, intermediate to acidic rock types. Two groups may be identified on the basis of the chemistry and mineralogy. The first group has a calc-alkaline metaluminous chemistry and contains mainly “ high-K” types, sometimes “ medium-K” and exceptionally “low-K” types. They are gabbros and basalts, diorites and andesites, tonalites and dacites. Some granitoids (quartz-monzonites, granodiorites and syenogranites) possess affinities with this magmatism (Bejaia–Amizour and Thenia intrusions). Only mafic to intermediate enclaves of magmatic origin are found in granitoids from this group. The second group has strongly peraluminous compositions: they are cordierite-bearing granodiorites, monzogranites and microgranites, as well as dacites and rhyolites (ignimbrites). Two types of enclaves exist in these granitoids: (i) microgranular metaluminous hornblende-bearing enclaves of igneous derivation, (ii) strongly peraluminous enclaves of metapelitic compositions. Textures and mineralogical associations indicate that the enclaves experienced heating at decreasing pressures and also partial melting. Therefore, they are indicative of assimilation, not of restite unmixing. After removing the local effects of hydrothermal alteration, the O, Sr, Nd isotopic compositions of parent magmas were determined: they span a very large range of values, e.g., eNd (T) varies from +12 (Cap Bougaroun gabbros) to −10 (Crd-bearing granitoids). From the covariation of Sr–Nd isotopic compositions and the constraints of O isotopic ratios, the following sources are proposed for the different rock types: Mafic to intermediate rocks contain a subduction-related component but most of them require contamination at crustal levels. The source of metaluminous granitoids is predominantly crustal as constrained by their high O isotopic composition (δ18O ranging from +9.3‰ up to +13‰), but they might contain a minor component derived from the mafic sources. Most of the cordierite-bearing granitoids are thought to be formed through assimilation of pelitic metasediments by a less aluminous parental magma. The general tectonic setting of this Neogene (limited, linear but variegated) magmatism is explanable in terms of the slab detachment models recently advocated by several authors in the western Mediterranean domains. This study argues that cordierite-bearing granitoids may be produced in areas of high heat flow, in crustal domains which did not experience important thickening.

A 1 200 km-long linear magmatic belt extends along the Mediterranean coast of the Maghreb from Eastern Tunisia to Morocco. This belt is mainly composed of Langhian calc-alkaline metaluminous to peraluminous granitoids and associated andesites/dacites in Central and Eastern Algeria. In Tunisia and Oranie/Western Morocco, calc-alkaline activity started later (during the Serravallian) and was followed by the emplacement of alkali basalts and basanites since the Tortonian to the Pliocene and, in some places, the Pleistocene. Available data on the tectonic setting, petrology, age and geochemistry of this belt show that most of its striking features, e.g. (1) very low magma production rate, subduction-related geochemical imprint, extensive crustal contamination for the calc-alkaline magmatism and (2) progressive magmatic change from calc-alkaline to alkaline, are consistent with magma generation during a slab breakoff process as proposed by Carminati et al. in 1998. The magmatism associated with this breakoff started in Central Eastern Algeria at 16 Ma, then propagated eastwards and westwards. The upward flow of asthenospheric enriched plume-type mantle through the tear in the downgoing slab first triggered melting of the overlying lithospheric mantle which had been metasomatised during a previous subduction period. Heat supply from this uprising asthenosphere may have warmed up the continental crust and made its involvement in assimilation processes easier. As the asthenosphere ascended through the ‘window’ in the slab, partial melting occurred at the uprising boundary between asthenosphere and lithosphere, generating basalts with transitional characteristics between those of calc-alkaline and alkaline basalts. As the asthenospheric upwelling proceeded, partial melting then occurred in the sole asthenospheric mantle, producing alkali basalts.

International audience; In the Arokam Tenere, the three studied massifs of granitoids are located around the N-S oriented Raghane mega-shear zone, which separates two of the main domains of the Tuareg shield, the Saharan metacraton and the Central Hoggar. The field observations, AMS analyses and U-Pb zircon dating were completed by a study of Landsat images because of the scarcity of outcrops in several parts of the studied area.;The image analysis allows to distinguish Arokam-East and Abdou granitoids in the eastern plutonic complex. It has also shown that the western plutonic complex corresponds to two different intrusions: the Yvonne granite and granodiorite. This is confirmed by the magnetic fabric that presents different characteristics in the different granitoids. U-Pb zircon dating and field observations show that the Arokam-West basement granite is much older (1915 Ma) than the Hanane granodiorite (582 Ma) in the central plutonic complex. Arokam-East and -West granites then belong to the Eburnean basement. The magnetic fabric of these granites is mainly associated with a post-magmatic deformation, probably of Pan-African age. Yvonne granodiorite is likely contemporaneous of the main displacement along the Raghane shear zone. The Yvonne granite (594 Ma) and Hanane granodiorite have a fabric similar to that previously obtained in most plutons of the Tiririne area. This fabric is related to the regional stress field, associated with the activity of the Raghane shear zone, during the late-magmatic phase in the plutons. On the contrary, the magnetic fabric of the Abdou pluton is still reflecting only the magma flow.

International audience; The Eastern Hoggar is by far the least well known part of the Tuareg Shield. It is composed, from west to east, of the Aouzegueur, Edembo and Djanet Terranes. The Djanet Terrane is the easternmost Hoggar terrane and comprises a greenschist-facies clastic sedimentary sequence, the Djanet Group, intruded by granitoids. Laser ablation (LA-) ICP-MS U-Pb zircon ages of detrital zircons from these sediments yield a large range of ages similar to ages known in Central and Western Hoggar; the youngest is 590 +/- 10 Ma (2 sigma), which is the maximum age of deposition of the Djanet Croup. The Djanet Group is intruded by the Djanet Batholith (571 +/- 16 Ma), by high-level subcircular plutons such as the Tin Bedjane Pluton (568 +/- 5 Ma) and finally by the felsic Tin Amali Dyke Swarm (558 +/- 5 Ma), all ages being SHRIMP U-Pb zircon. The deposition and metamorphism of the Djanet Group thus occurred between 590 Ma (the age of the youngest detrital zircons analyzed in the Djanet Group) and c. 570 Ma (the age of intrusive granitoids). Nd T-DM two-stage model ages (1.30-2.03 Ga), initial Sr-87/Sr-86 ratios (0.7035-0.7095) and epsilon(Nd) (-3 to -11) of the three intrusive suites, all being high-K calc-alkaline in composition, indicate mainly an old, Rb-depleted continental source. Migmatization in the adjacent Edembo Terrane is dated at 568 +/- 4 Ma (U-Pb zircon SHRIMP age), contemporaneous with the intrusion of the Djanet plutons. Rocks and events in the Edembo and Djanet Terranes are all intracontinental. We propose that the Djanet Terrane lies on the boundary of a craton located to the north-east, that we defined here as the Murzuq craton. The existence of the Murzuq craton is supported by sedimentary and geophysical data. We suggest that the deformation of Eastern Hoggar occurred 575-555 Ma, due to the indentation of the Murzuq craton and has no link with the older convergence with the West African craton as was the case for the central and western parts of the Tuareg Shield. This determines a late Ediacaran intracontinental Murzukian event that probably also occurred to the east in the Tibesti area.

International audience; The N-S oriented Raghane shear zone (8 degrees 30') delineates the western boundary of the Saharan metacraton and is, with the 4 degrees 50' shear zone, the most important shear zone in the Tuareg shield. It can be followed on 1000 km in the basement from southern Air, Niger to NE Hoggar, Algeria. Large subhorizontal movements have occurred during the Pan-African orogeny and several groups of granitoids intruded during the Neoproterozoic. We report U-Pb zircon datings (laser ICP-MS) showing that three magmatic suites of granitoids emplaced close to the Raghane shear zone at c. 790 Ma, c. 590 and c. 550 Ma. A comprehensive and detailed (158 sites, more than 1000 cores) magnetic fabric study was performed on 8 plutons belonging to the three magmatic suites and distributed on 200 km along the Raghane shear zone. The main minerals in all the target plutons do not show visible preferential magmatic orientation except in narrow shear zones. The AMS study shows that all plutons have a magnetic lineation and foliation compatible with the deformed zones that are zones deformed lately in post-solidus conditions. These structures are related to the nearby mega-shear zones, the Raghane shear zone for most of them. The old c. 793 Ma Touffok granite preserved locally its original structures. The magnetic structures of the c. 593 Ma Ohergehem pluton, intruded in the Aouzegueur terrane, are related to thrust structures generated by the Raghane shear zone while it is not the case of the contemporaneous plutons in the Assode-Issalane terrane whose structures are only related to the subvertical shear zones. Finally, the c. 550 Ma granite group has magnetic structure related to the N-S oriented Raghane shear zone and its associated NNE-SSW structures when close to them, but NW-SE oriented when further. These NW-SE oriented structures appear to be characteristic of the late Neoproterozoic evolution of the Saharan metacraton and are in relation to the convergence with the Murzuq craton. This evolution reflects the rheological contrast existing along the Raghane shear zone marking the western boundary of the Saharan metacraton.

International audience; A paleomagnetic study has been conducted on intrusive doleritic rocks cropping out within Devonian horizontal tabular formations of the Saharan craton (Tin Serririne basin, South of Hoggar shield). The 40K/40Ar dating of the dolerites gave an age of 347.6 ± 8.1 Ma, i.e. Tournaisian. The paleomagnetic data present three different directions. The first has a paleomagnetic pole close to the previous African poles of Permian age. This direction is therefore interpreted as a Permian remagnetization. The second direction, which is defined by both linear regression and remagnetization circles analysis, is considered as the primary magnetization. It yields a new African Tournaisian paleomagnetic pole (λ = 18.8° S, phi = 31.2° E, K = 29, A95 = 7.5°) very close to the Ben Zireg Tounaisian pole [Aifa, T., Feinberg, H., Pozzi, J.P., 1990. Devonian/Carboniferous paleopoles for Africa. Consequences for Hercynian geodynamics. Tectonophysics, 179, 288–304]. The third direction has intermediate orientation between those of the first or second directions and that of the Upper Cenozoic field. It is interpreted as related to a composite magnetization. This new Tin Serririne pole improves the APWP of Gondwana, for this key period of the evolution of the Pangea. This APWP confirms the previous paleogeographic reconstruction which shows that the pre-Hercynian ocean between Gondwana and Laurussia is still not close during the beginning of the Carboniferous.

The Miocene igneous activity in Lesser Kabylia includes a ~130 km-long EW-trending lineament that extends along the eastern Algerian margin from Kabylie de Collo to Ouest-Edough-Cap de Fer area. It includes mostly medium-K to High-K calc-alkaline plutonic and volcanic rocks. In the studied area, these magmatic rocks crosscut and/or overlie the inner zones of the Maghrebides represented by basement and Kabylian cretaceous and Numidian flyschs nappes. New U-Pb dating on zircons and K-Ar ages on whole rocks and separated minerals document a 17 Ma onset for the post-collisional K-rich calc-alkaline magmatism. These Upper Burdigalian ages obtained on the Bougaroun pluton are the oldest presently identified for Krich calc-alkaline rocks in the whole 1200 km-long EW trending magmatic belt located along the Mediterranean coast of Maghreb. However, according to new K-Ar ages, magmatic activity started in Ouest Edough zone at ~16 then persisted intermittently in the two studied areas at ~15.5 Ma, 14-13 Ma and stopped at ~11 Ma, with the emplacement of mafic and felsic dykes in Kabylie de Collo. In addition, we measured older (Upper Oligocene) Ar-Ar hornblende ages of 27.0 ± 3.0 Ma and 23.3 ± 3.2 Ma on LREE-depleted gabbros outcropping at Cap Bougaroun sensu stricto. According to our new geochemical and isotopic data, we distinguish two sources for magmatic rocks in the studied area: a depleted mantle source which could represent the ambient asthenosphere still not modified by the subduction processes at the time of emplacement of the Upper Oligocene LREE-depleted gabbros. The latter could be related to the Upper-Oligocene rifting before the back-arc crust formation in Algerian basin or to dyke systems or gabbroic intrusions crosscutting the stretched Kabylian continental crust. An enriched mantle source modified by a subduction component (melt or fluid) escaping from a northward-dipping subducted Tethyan oceanic lithosphere. The enriched mafic magmas are believed to come from this metasomatized mantle and are genetically related to the differentiated rocks through crystal fractionation and assimilation of large amounts of crustal lithologies, during their ascent through the African continental crust. We propose a tectono-magmatic model involving an Early Miocene Tethyan slab breakoff combined with delamination of the edges of the African and Kabylian continental lithospheres. At 17 Ma, the asthenospheric thermal flux upwelling through the slab tear induced the thermal erosion of the Kabylian lithospheric mantle metasomatized during the previous subduction event and triggered its partial melting. We attribute the strong trace element and isotopic crustal signature of Bougaroun felsic rocks to extensive interactions between ascending mafic melts and the African crust underthrust beneath the Kabylie de Collo basement.; L’activité magmatique miocène en Petite Kabylie s’exprime par la mise en place de roches plutoniques et volcaniques de composition majoritairement riche en K ainsi que moyennement riches en K. Ces roches forment des pointements dispersés sur près de 130 km le long de la marge méditerranéenne de l’Algérie. Dans les deux secteurs d’étude : la Kabylie de Collo et l’Ouest Edough-Cap de Fer, elles recoupent les empilements de nappes de socle et de flyschs crétacés et numidiens. De nouvelles datations U-Pb sur zircons et K-Ar sur roche totale et minéraux séparés ont permis de fixer à 17 Ma le début de l’activité magmatique post-collisionnelle à affinité calco-alcaline riche en K2O. Ces âges obtenus sur le batholithe granitique de Bougaroun (200 km2) sont les plus anciens jamais obtenus dans toute la Marge Méditerranéenne du Maghreb. L’activité magmatique s’étend vers l’Est et atteint la zone ouest-Edough-Cap de Fer vers ~16 Ma puis se poursuit de façon intermittente dans les deux secteurs d’étude à ~15 Ma, 14-13 Ma jusqu’à 11 Ma avec la mise en place de corps filoniens mafiques et felsiques en Kabylie de Collo. En outre, un âge oligocène supérieur (27.0 ± 3.0 Ma et 23.3 ± 3.2 Ma) a été mesuré par la méthode Ar/Ar sur amphiboles des gabbros à caractère océanique du Cap Bougaroun s.s (Kabylie de Collo). Les nouvelles données géochimiques et isotopiques ont permis de mettre en évidence deux sources pour le magmatisme dans les deux secteurs étudiés. Une première source mantellique appauvrie, non modifiée par un composant de subduction qui est à l’origine des gabbros à caractère océanique du Cap Bougaroun s.s et de Bou Maïza au Sud de l’Edough. Ceux-ci pourraient représenter des reliques du stade de rifting d’âge oligocène supérieur en prélude à l’ouverture en position arrière-arc du bassin algérien. Une deuxième source enrichie en terres rares légères et en éléments mobiles est représentée par le manteau lithosphérique subcontinental kabyle précédemment métasomatisé durant la subduction à vergence nord de la lithosphère océanique téthysienne au Paléogène. Les magmas mafiques enrichis en LREE issues de cette source ont ensuite évolué par cristallisation fractionnée et contamination crustale pour former les roches intermédiaires et felsiques de la marge est-algérienne. Nous proposons un modèle tectono-magmatique de rupture de slab téthysien associée à une délamination crustale au niveau des bordures des deux lithosphères continentales africaine et kabyle. A 17 Ma, le flux thermique d’origine asthénosphérique ascendant à travers la déchirure du slab téthysien induit la fusion du manteau téthysien. Les magmas mafiques calco-calcalins moyennement potassiques subissent des échanges chimiques avec le socle africain durant leur ascension à travers celui-ci, générant les magmas intermédiaires et felsiques calco-alcalins riches en K caractérisés par une importante signature crustale.