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The Central Tianshan Terrane (CTT) in the Eastern Tianshan (Xinjiang, NW China) is an important Pb–Zn metallogenic belt and played a pivotal role in crustal evolution and collisional tectonics of the southern Central Asian Orogenic Belt. The Shaquanzi gabbro and Hongyuan granodiorite are located in the northern margin of the CTT and associated with Pb–Zn mineralization. Zircon U–Pb dating yielded weighted mean ages of 307.2 ± 1.5 Ma and 301.2 ± 1.5 Ma for the Shaquanzi gabbro and the Hongyuan granodiorite, respectively. These rocks are medium-K calc-alkaline series and enriched in large ion lithophile elements (LILEs; e.g., K, Rb, Ba) and depleted in high field strength elements (HFSEs; e.g., Nb, Ta, Ti), displaying typical arc affinities. The Shaquanzi gabbro shows low Nb/Ta (11.0–14.2), a high Mg # range (56–59), positive zircon ε Hf (t) (+ 3.30 − + 7.26) and whole rock ε Nd (t) (+ 0.70 − + 1.38) values, and low I Sr ratios (0.704858–0.705137), which indicate that the protolith was probably derived from the sub-continental lithospheric mantle that had been metasomatized by subduction-related fluids. The Hongyuan granodiorite contains hornblende but lack of Al-rich minerals and has low I Sr ratios (0.704769–0.706211 < 0.707), suggesting an I-type origin. Moreover, the Hongyuan granodiorite has positive ε Hf (t) (+ 1.12 − + 5.57) and ε Nd (t) (+ 0.38 − + 1.86) values, with high Mg # (52), variable Nb/Ta ratios (12.6–12.9), low contents of Ni, Cr and Co and Pb isotopes ( 206 Pb/ 204 Pb = 17.461–18.299, 207 Pb/ 204 Pb = 15.541–15.581, 208 Pb/ 204 Pb = 37.456–38.129), suggesting the Hongyuan granodiorite was generated by partial melting of juvenile crust sources mixed with some mantle-derived materials. Combined published works with our new geochronological, geological, geochemical and isotopic data, we propose that the CTT may have evolved from a continental arc to a syn-collisional setting during the period of ca. 307–301 Ma. The continuing southward subduction of the Junggar oceanic slab beneath the CTT in the Late Carboniferous resulted in extensive arc-related volcanic rocks emplacement that had indirect links to the Pb–Zn mineralization (e.g., reworked/upgraded). [ABSTRACT FROM AUTHOR]

Zircon U–Pb ages of high Mg dioritic dikes in the Mesoproterozoic Kawabulake Group in the Eastern Tianshan area, NW China indicate that they were emplaced in the Early Carboniferous at 353–348 Ma. The dikes consist of medium-grained plagioclase and hornblende with minor clinopyroxene and trace quartz. They are characterized by intermediate SiO 2 (60–62 wt.%), low TiO 2 (0.63–0.71 wt.%), relatively high Al 2 O 3 (15.1–15.8 wt.%) and MgO contents (3.45–4.15 wt.%) with Mg# generally higher than 56 (56–59). The geochemistry of the high Mg diorites suggest they were formed by similar magmatic processes to sanukitoid high Mg Andesites such as those of the Setouchi volcanic belt, Japan. Zircons from the high Mg dioritic dikes have ε Hf( t ) values of −6.8 to +14.5. The dominantly positive values suggest a juvenile source, whereas the small number of negative values suggests mature components were also incorporated into the source. Similarly, the positive ε Nd( t ) values (0 to +2.2) are interpreted to reflect a juvenile source whereas the negative values of (−5.2 to 0) suggest participation of old crustal rocks in the petrogenesis of the diorites. The variable ε Hf( t ) and ε Nd( t ) values suggest that the mature material was assimilated during magma ascent rather than in the mantle wedge which would result in more uniform values. Mass balance calculations suggest that the dioritic dikes were derived from sources composed of approximately 97% juvenile mantle-derived material and 3% sediment. Petrographic, elemental, and isotopic evidence suggest that the dioritic dikes were generated by partial melting of depleted mantle that migrated into the shallow crust where it assimilated older sedimentary rocks of the Mesoproterozoic Kawabulake Group. [ABSTRACT FROM AUTHOR]