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The Dabieshan massif is famous as a portion of the world's largest HP-UHP metamorphic belt in east-central China that was built by the Triassic North-South China collision. The central domain of the Dabieshan massif is occupied by a huge migmatite-cored dome [i.e., the central Dabieshan dome (CDD)]. Origin of this domal structure remains controversial. Synthesizing previous and our new structural and geochronological data, we define the Cretaceous Dabieshan as an orogen-scale metamorphic core complex (MCC) with a multistage history. Onset of lithospheric extension in the Dabieshan area occurred as early as the commencement of crustal anatexis at the earliest Cretaceous (ca. 145 Ma), which was followed by primary (early-stage) detachment during 142-130 Ma. The central Dabieshan complex in the footwall and surrounding detachment faults recorded a consistently top-to-the-NW shearing. It is thus inferred that the primary detachment was initiated from a flat-lying detachment zone at the middle crust level. Removal of the orogenic root by delamination at ca. 130 Ma came into the extensional climax, and subsequently isostatic rebound resulted in rapid doming. Along with exhumation of the footwall, the mid-crustal detachment zone had been warped as shear zones around the CDD. After 120 Ma, the detachment system probably experienced a migration accommodated to the crustal adjustment, which led to secondary (late-stage) detachment with localized ductile shearing at ca. 110 Ma. The migmatite-gneiss with HP/UHP relicts in the CDD (i.e., the central Dabieshan complex) was product of the Cretaceous crustal anatexis that consumed the deep-seated part of the HP-UHP slices and the underlying para-autochthonous basement. Compared with the contemporaneous MCCs widely developed along the eastern margin of the Eurasian continent, we proposed that occurrence of the Dabieshan MCC shares the same tectonic setting as the 'destruction of the North China craton'. However, geodynamic trigger of the Cretaceous continental-scale NW-SE extension in eastern Asia is still a mystery. [ABSTRACT FROM AUTHOR]

The south-western Chinese Tianshan orogenic belt is famous for its omphacite-bearing blueschists and associated eclogite-facies metavolcanic rocks. Although numerous petrologic, geochemical and geochronological studies are available, structural data and interpretations are still rare. This paper provides new structural data, including bulk geometry of structures and kinematic analyses, based on field and laboratory studies along the Akyazhi, Keburt and Muzaert Rivers. The study area is divided into three tectonic units, namely (1) a Southern Unit composed of weakly metamorphosed sedimentary rocks of Silurian age; (2) a Central HP/LT Unit composed of blueschist-eclogite-facies metamorphic rocks derived from basalts, pelites and volcaniclastic rocks; (3) a Northern Unit, which consists of a Carboniferous magmatic arc developed upon an amphibolite-facies metamorphic continental basement. Our structural analysis documents a polyphase deformation. The main event (D1) is reflected by Devonian to Carboniferous top-to-the northwest ductile shearing, coeval with HP/LT metamorphism. This is followed by north-directed thrusting (D2) of the Southern Unit over the Central HP/LT Unit, coeval with retrogression of the high-pressure rocks. A top-to-the-S (SE) deformation (D3) overprints the earliest events and is observed in the Northern and Central Units. Lastly, Permian dextral ductile-brittle wrenching (D4) overprints the older flat-lying fabrics. D4 is conspicuous along the Nalati Fault that separates the Northern Unit from the Central HP/LT Unit. The absolute timing of these deformation events is discussed in the light of available radiometric dating. The structural, metamorphic and geochronological data are integrated into a geodynamic model of the south-western Chinese Tianshan that emphasizes south-directed subduction of microcontinents located between Tarim and Junggar. [ABSTRACT FROM AUTHOR]