International audienceThe Chinese Tianshan belt is a major part of the southern Central Asian Orogenic Belt, extending westward to Kyrgyzstan and Kazakhstan. Its Paleozoic tectonic evolution, crucial for understanding the amalgamation of Central Asia, comprises two stages of subduction-collision. The first collisional stage built the Eo-Tianshan Mountains, before a Visean unconformity, in which all structures are verging north. It implied a southward subduction of the Central Tianshan Ocean beneath the Tarim active margin, that induced the Ordovician-Early Devonian Central Tianshan arc, to the south of which the South Tianshan back-arc basin opened. During the Late Devonian, the closure of this ocean led to a collision between Central Tianshan arc and the Kazakhstan-Yili-North Tianshan Block, and subsequently closure of the South Tianhan back-arc basin, producing two suture zones, namely the Central Tianshan and South Tianshan suture zones where ophiolitic mélanges and HP metamorphic rocks were emplaced northward. The second stage included the Late Devonian-Carboniferous southward subduction of North Tianshan Ocean beneath the Eo-Tianshan active margin, underlined by the Yili-North Tianshan arc, leading to the collision between the Kazakhstan-Yili-NTS plate and an inferred Junggar Block at Late Carboniferous-Early Permian time. The North Tianshan Suture Zone underlines likely the last oceanic closure of Central Asia Orogenic Belt; all the oceanic domains were consumed before the Middle Permian. The amalgamated units were affected by a Permian major wrenching, dextral in the Tianshan. The correlation with the Kazakh and Kyrgyz Tianshan is clarified. The Kyrgyz South Tianshan is equivalent to the whole part of Chinese Tianshan (CTS and STS) located to the south of Narat Fault and Main Tianshan Shear Zone; the so-called Middle Tianshan thins out toward the east. The South Tianshan Suture of Kyrgyzstan correlates with the Central Tianshan Suture of Chinese Tianshan. The evolution of this southern domain remains similar from east (Gangou area) to west until the Talas-Ferghana Fault, which reflects the convergence history between the Kazakhstan and Tarim blocks

The Internal Zone of the Betic Cordilleras consists of several superimposed major thrust sheets with different P-T-t evolutions. On the basis of an integrated field, miCroscopic and laboratory study, the tectono-metamorphic history of the Mulhacen Complex and Almanzora Unit has been reconstructed in detail. The Mulhacen Complex has been af€ected by at least five phases of penetrative deformation, which have been labelled Dx-,, D. , DX+,, D,,, and DX++ D,-, and D, are related to continent-continent collision, which is indicated by high pressure-low temperature (WILT) and subsequent intermediate PIT metamorphic conditions. D,,, is related to crustal thinning and heterogeneous extension. During this event the ALmanzora Unit was juxtaposed against the Mulhacen Complex. This phase was succeeded by the establishment of low pressure-high temperature (LPIHT) conditions and at least two phases of folding and overthrusting. The Almanzora Unit shows a comparable tectono-metamorphic evolution p t D,,,. However, the P I T conditions prior to D.,, indicate a higher crustal position with respect to the Mulhacen Complex during the collisional event.

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In order to de®ne the mechanisms involved during exhumation of the eclogite-facies rocks from the Champtoceaux Complex (Armorican Massif, France), Sm-Nd, Rb-Sr and 40 Ar/ 39 Ar methods are combined with a petrological study to construct a pressure±temperature±time (P±T±t) path for the Cellier Unit.The Champtoceaux Complex is a crustal-scale thrust sheet located in the South Armorican Domain. The lower unit, the Cellier Unit, consists of leucocratic gneisses, mica-schists and well-preserved eclogites. Petrological data on selected samples from different lithologies show (1) preservation of growth zoning in garnet, (2) no amphibolite-or greenschist-facies overprint in the eclogite and (3) variations in the Si content of phengite as a function of bulk-rock chemistry, P±T conditions and partial reequilibration during decompression.Sm-Nd analyses on the eclogite sample give a Grt±Cpx±whole-rock age of 362 AE 25 Ma, consistent with the U-Pb age of 356 AE 8 Ma (recalculated) obtained from the same sample by J. L. Paquette in 1987. Preservation of growth zoning in the garnet and the absence of late overprint show that resetting of both Sm-Nd and U-Pb systems is unlikely. The age of c. 360 Ma is thus interpreted as the age of the high-pressure event.Eight 40 Ar/ 39 Ar plateau ages, ranging from 352.0 AE 1.6 to 340.5 AE 1.4 Ma, are obtained from phengite single grains from six samples. The existence of Ar inheritance is unlikely, because (1) 40 Ar/ 39 Ar ages are younger than the age of the high-pressure event as deduced from U-Pb and Sm-Nd ages, (2) duplicates display a high reproducibility of plateau ages in all cases, and (3) a concordant Rb-Sr age is obtained on one common sample. These plateau ages probably represent closure temperatures (possibly on the order of 450±500 C) for the best preserved and oldest samples, whereas the younger plateau ages may represent a later closure of the K/Ar system due to continuous deformation and chemical re-equilibration during retrogression.

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