Tectonic evolution from subduction to arc-continent collision of the Junggar ocean: Constraints from U-Pb dating and Hf isotopes of detrital zircons from the North Tianshan belt, NW China

Abstract

The Junggar ocean, once situated north (present coordinate) of the Yili and Central Tianshan blocks during early Paleozoic to late Carboniferous time, was a major southern branch of the Paleo-Asian Ocean, the opening, expansion, and final closure of which led to the development of the Central Asian Orogenic Belt between Eastern Europe-Siberia and Tarim-North China. However, the detailed evolution of the Junggar ocean has not been well constrained. This paper reports U-Pb and Lu-Hf isotopic data of detrital zircons from sandstones in the North Tianshan belt, which can provide new insights into understanding the Paleozoic development of the Junggar ocean. Most detrital zircons exhibit oscillatory zoning and high Th/U ratios, typical of igneous origin. The predominant Paleozoic zircons yield major age populations at ca. 294, 313-327, 338-375, 440-455, and 474-502 Ma and are interpreted to have been derived from the long-lived volcanicand island-arc systems formed by the southward subduction of the Junggar ocean and subsequent collisional and postcollisional magmatism. The minor Precambrian zircons yield ages scattering at ca. 550

Paleozoic magmatism and metamorphism in the Central Tianshan block revealed by U–Pb and Lu–Hf isotope studies of detrital zircons from the South Tianshan belt, NW China

“…Ma adakites (zircon ε Hf (t) = -0.8~+2.7; Mao et al, 2010b) and 397 ± 3 Ma K-feldspar granite By contrast, Precambrian detrital zircons in this study correspond well with those previously reported Precambrian detrital zircons (Ma et al, 2012a(Ma et al, , 2012bZhang et al, 2015) and…”

“…8 and 9;Zhang et al, 2015). A recent detrital zircon study of sedimentary rocks from the southern margin of the Junggar Basin has also revealed that the detrital zircons were derived dominantly from the southern Chinese Tianshan since the initiation of the basin in the Late Carboniferous (Yang et al, 2013).…”

“…(Hu et al, 2007;Ma et al, 2013bMa et al, , 2014Mao et al, 2010a;Shi et al, 2014;Yang et al, 2012) and the permanent dominance of such-aged detrital zircons in Paleozoic sedimentary strata in the CTS (Ma et al, 2012b), NTS (Zhang et al, 2015), STS and even northern Tarim (Han et al, 2015). Highly-evolved Hf isotopic signatures of these zircons (mean ε Hf (t) = -10) suggest magma formation primarily through melting of ancient continental crust, further matching those of zircons (zircon ε Hf (475) = -12.9~-6.0, ε Hf (458) = -13.1~-6.9, ε Hf (450) = -17.4~-14.7 and ε Hf (442) = -11.9~-6.3) in contemporary arc-related granitoids in the CTS block (Ma et al, 2013bShi et al, 2014;Yang et al, 2012).…”

“…8d), were derived from the NTS island arcs, which were probably formed during slab rollback of the Junggar ocean (Zhang et al, 2015). 2006b; Zhang et al, 2015).…”

Provenance of late Paleozoic strata in the Yili Basin: Implications for tectonic evolution of the South Tianshan orogenic belt

“…This study is mainly focused on the western part of the Tianshan orogenic collage, since the eastern Tianshan has probably undergone a discrete Paleozoic evolution (Y.G. Han et al, , 2016aZhang et al, 2016).…”