Formation of HP–LT rocks and their tectonic implications in the western Tianshan Orogen, NW China: geochemical and age constraints

Paleozoic tectonics of the southern Chinese Tianshan: Insights from structural, chronological and geochemical studies of the Heiyingshan ophiolitic mélange (NW China)

“…The first one is the age of the orogeny which some authors considered as to be late Paleozoic (e.g., Gao et al, 1998Gao et al, , 2009Wang et al, 2010) but, alternatively, others ague for Triassic (e.g., Zhang et al, 2007;Xiao et al, 2008). The second issue concerns the polarity of subduction of the paleo-Tianshan Ocean, a north-directed subduction was proposed by Windley et al (1990), Xiao et al (2004Xiao et al ( , 2008, Gao et al (1998) and Gao and Klemd (2003); whereas, a southward subdution is more likely consistent with newly published data (Charvet et al, 2007;Wang et al, 2008;Lin et al, 2009); and a compromise of bi-directional subduction was suggested by Gao et al (2009).…”

“…This belt consists of greenschist-, blueschist-and eclogite-facies rocks, which were probably transformed from sea-floor deposits and basaltic rocks (Gao et al, , 1999Ai et al, 2006). Isotopic ages of 415-343 Ma (phengite 40 Ar/ 39 Ar plateau and Sm-Nd isochron) were obtained for eclogite and blueschist (Dobretsov et al, 1987;Xiao et al, 1992;Gao et al, 1995bGao et al, , 2000Gao et al, , 2006Gao and Klemd, 2003), and the peak HP metamorphism was considered to have occurred at ~345 Ma (Gao and Klemd, 2003;Klemd et al, 2005). In addition, eclogites and blueschists yielded younger ages of 331~302 Ma (recrystallized phengite 40 Ar/ 39 Ar plateau and Rb-Sr isochron) that were regarded as reflecting the timing of retrograde metamorphism during exhumation of the HP metamorphic rocks (Gao and Klemd, 2003;Stupakov et al, 2004;Klemd et al, 2005;Simonov et al, 2008;Wang et al, 2010).…”

“…The final closure of the South Tianshan back-arc basin resulted in northward emplacement of the ophiolitic mélanges upon the Central Tianshan. Synchronously, the Paleo-Tianshan Ocean was closed, and the collision between the Kazakhstan-Yili block and the Central Tianshan-Tarim assemblage occurred during the Late Devonian to early Carboniferous (e.g., Gao and Klemd, 2003;Wang et al, 2010; Fig. 13D).…”

Geochronology and geochemistry of igneous rocks in the Bailingshan area: Implications for the tectonic setting of late Paleozoic magmatism and iron skarn mineralization in the eastern Tianshan, NW China

“…Li et al, 2002Li et al, , 2006Wang et al, 2014 Ar plateau ages of phengite (ca. 334 and 331 Ma) from an omphacite-phengite-bearing blueschist, which formed in a Paleozoic accretionary wedge on the southern side of the Yili-Central Tianshan (YCT) block, Gao and Klemd (2003) considered that the subduction of the South Tianshan Ocean plate (which separated the Tarim craton and the YCT block) may have been completely finished by the end of the Early Carboniferous (Fig. 15a, b).…”

Geochemistry of primary-carbonate bearing K-rich igneous rocks in the Awulale Mountains, western Tianshan: Implications for carbon-recycling in subduction zone

“…In southwestern Tianshan, a huge high-P and low-T metamorphic belt -comprised of mafic metavolcanic rocks, metavolcaniclastic rocks, metagreywacke, marble and serpentinite with a length of at least 200 km and width of over 10 km as so far reported (Gao and Klemd, 2003) -was formed within a Paleozoic accretionary wedge on the south side of the Kazakhstan-Yili plate. The discovery of coesitebearing schists and eclogites and magnesite dissociation in the metapelites (Zhang et al, 2002a,b;Zhang et al, 2003) indicates that the metapelites experienced ultrahigh-pressure metamorphism with a peak metamorphic age of 320 ± 3.7 Ma and peak metamorphic P-T conditions of 565°C and 29 kbar (Yang et al, 2013).…”