Crustal evolution in the South Tianshan Terrane: Constraints from detrital zircon geochronology and implications for continental growth in the Central Asian Orogenic Belt

Abstract

The South Tianshan Terrane (STT) is located in the boundary between the south‐western Central Asian Orogenic Belt (CAOB) and the Tarim Craton and is a key area for understanding the geologic and tectonic history of the craton and the orogenic belt. In this paper, we report detrital zircon ages from the Late Palaeozoic and Mesozoic clastic sedimentary rocks from the southern part of STT. In combination with the U–Pb ages for felsic igneous and meta‐igneous rocks exposed in the STT and adjacent tectonic units, we identify several distinct age populations. Provenance analysis suggests that the detrital zircon grains were predominately derived from the felsic magmatic rocks in the Tarim Craton and South Tianshan Terrane. The pre‐Neoproterozoic age populations may be associated with the early history of the Tarim Craton. Several pulses of Neoproterozoic magmatism are revealed by our dataset, presumably related to the assembly and break‐up of the supercontinent Rodinia. The 995 to 901 Ma detrital zircon grains were likely sourced from magmatic rocks associated with the assembly of Neoproterozoic Tarim to Australia. Among the age population of 886 to 752 Ma, the older group might be related to the subduction‐related magmatism after the assembly of Rodinia, and the younger one records a protracted magmatic event in a continental rift‐related setting associated with the break‐up of Rodinia. Two younger Neoproterozoic age populations (736 to 694 Ma and 665 to 610 Ma), showing narrow spreads with weak peaks, represent the waning stages of igneous activities related to the break‐up of Rodinia. Regarding the Palaeozoic evolution, together with other evidence, our data indicate a two‐stage subduction model for the SW Palaeo‐Asian Ocean. The 490 to 384 Ma age population corroborates the existence of Early Palaeozoic continental arc magmatism at the northern margin of Palaeozoic Tarim generated by the bidirectional subduction of the South Tianshan Ocean. After a ~30 My period of tectonomagmatic quiescence, the second stage is marked by the northward subduction of the South Tianshan Terrane during Late Devonian to Early Carboniferous. The final collision of Tarim and the south‐western CAOB likely occurred during the Late Carboniferous, followed by syn‐ and post‐collisional magmatism, as represented by the 320 to 265 Ma age population. Based on the detrital zircon ages in conjunction with the Hf isotopic features of zircons from Palaeozoic igneous rocks, our study does not support the model of large‐scale Phanerozoic net continental growth in the South Tianshan Terrane.

U–Pb age and Hf isotopic composition of detrital zircons from the modern river of the South Tianshan orogenic belt and their implications for Palaeozoic tectonic and crustal evolution

“…310–250 Ma alkaline intrusive rocks, and ca. 300–270 Ma A‐type granites according to the chronology and geochemical characteristics (Gao et al, 2009; Gou & Zhang, 2016; Huang et al, 2019; Ma, Shu, & Meert, 2015; Ma, Shu, Meert, & Li, 2014). They were likely united to form the Yili‐CTS Block before the closure of the South Tianshan Ocean (Gao et al, 2009; Han et al, 2011; Xia, Zhang, Xia, & Bader, 2014; Xiao et al, 2013).…”

“…Several mafic rocks within some of the mélanges show enriched mid‐oceanic ridge basalt (E‐MORB)‐like and oceanic island basalt (OIB)‐like geochemical attributes (Gao et al, 2011; Wang et al, 2011; Zhao et al, 2015). The Early Palaeozoic magmatic rocks are widely distributed along its southern margin, and they generally display calc‐alkaline attribute characteristics (Huang et al, 2013, 2019; Qin et al, 2016). Voluminous Late Palaeozoic A‐type granites and syenites, metaluminous, and high‐K granites were widely developed in the STS (Huang, Zhang, Santosh, & Zhang, 2014; Liu et al, 2013; Ma et al, 2015).…”

“…As far as the crustal evolution is concerned, some scholars have suggested that the growth of new crust in South Tianshan orogenic belt was remarkable according to considerable amounts of juvenile components into magma formation during the Palaeozoic (Long et al, 2011; Tang et al, 2017). Others, in contrast, argued for the continent formation in this belt was characterised by reworking of ancient basement rock with limited or insignificant inputs of juvenile components, its growth pattern is different from other tectonic units in the CAOB (Huang et al, 2019). These controversies are mainly due to the fact that these previous studies are mostly based on the Hf isotopic results of zircons from single or several magmatic rocks.…”

“…The South Tianshan, one of the accretionary orogenic belts in the Tianshan, records the opening‐subduction‐closure history of the South Tianshan Ocean. Although numerous studies on tectonic evolution of this belt, the subduction polarity and final closure time of the South Tianshan Ocean still have not reached a consensus (Han et al, 2015; Han, He, Wang, & Guo, 2011; Huang et al, 2019; Wang et al, 2011; Xiao et al, 2013; Zhang, Zhao, Han, & Sun, 2019). As far as the crustal evolution is concerned, some scholars have suggested that the growth of new crust in South Tianshan orogenic belt was remarkable according to considerable amounts of juvenile components into magma formation during the Palaeozoic (Long et al, 2011; Tang et al, 2017).…”

“…Geologic maps of the southern South Tianshan orogenic belt and adjacent regions (Wang et al, 2007). Compiled sample location: (1) Quexiang area (Han et al, 2016a; Huang, Zhang, Santosh, Cheng, & Wang, 2019; Liu et al, 2013); (2) Heiyingshan area (Liu et al, 2013); (3) Kuche River area (Carroll et al, 2013; Han et al, 2016b; Huang et al, 2019; Wang, Zhang, & Liu, 2015); (4) Kule area (Huang et al, 2019). In Fig.…”