Final Assembly of the Southwestern Central Asian Orogenic Belt as Constrained by the Evolution of the South Tianshan Orogen: Links With Gondwana and Pangea

The Central Tianshan microcontinent (CTM) in the southern Central Asian Orogenic Belt is characterized by Precambrian crustal basements and widespread Palaeozoic granitic rocks. However, the Palaeozoic tectonic process and associated crustal evolution of the CTM have not been well constrained. In this paper, we report whole‐rock geochemistry, zircon U–Pb ages, Hf isotopes, and trace elements for the Late Carboniferous granodiorite and monzogranite from the Hongliujingbei area of the eastern CTM. These data were further integrated with previously published whole‐rock geochemistry and zircon Hf isotopic data of the intensive Late Carboniferous (327–300 Ma) magmatic rocks in the CTM in order to gain more insights into the crustal and tectonic evolution of the CTM during the Late Carboniferous. LA‐ICP‐MS zircon U–Pb dating results indicate that the granodiorite and monzogranite from the Hongliujingbei area were emplaced at ~320 Ma. Their highly variable zircon εHf(t) values (−0.1 to +12.9) suggest that the magmas of these rocks were formed by the mixing of mantle‐ and crustal‐derived magmas. The Late Carboniferous magmatic rocks from the CTM, as a whole, show a wide range of zircon εHf(t) values (−3.7 to +13.4) and geochemical characteristics typical for magma evolution in an active continental margin setting. Therefore, we suggest that the Late Carboniferous magmatic rocks in the CTM were probably generated in a continental arc formed by the southward subduction of the North Tianshan Ocean Plate beneath the CTM, and their mostly depleted zircon Hf isotopic compositions indicate that juvenile crustal growth was a dominant process in the CTM during the Late Carboniferous.

Section: Geological Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Late Carboniferous crustal evolution of the Chinese Central Tianshan microcontinent: Insights from zircon U–Pb and Hf isotopes of granites

Wen

2020

“…The Kazakhstan–Yili Block, bounded between the the North Tianshan suture zone and Nikolaev Line–North Nalati suture zone, tectonically belongs to the Kazakhstan microcontinent, which was built by amalgamation of several continental blocks with Precambrian basement and Phanerozoic sedimentary sequences (Alexeiev et al, ; Bazhenov et al, ; Biske & Seltmann, ; Kröner et al, ; Kröner et al, ; Liu, Wang, Shu, Jahn, & Lizuka, ; Mossakovsky, Ruzhentsev, Samygin, & Kheraskova, ; Wang et al, ; Wang et al, 2014; X.‐S. Wang et al, ; Wang et al, 2014). Some researchers consider that the Nikolaev Line–North Nalati suture zone and Southern Central Tianshan suture zone was distributed in Central Tianshan Arc Terrane, but both suture zones should be linked with the same South Tianshan Ocean, which is defined mainly by Bingdaban (Figure ; Dong et al, ), Mishigou (Charvet et al, ; Che et al, ), Gangou (Charvet et al, ; Dong et al, ), and ophiolitic mélange zones, and extended discontinuously to the east in Weiya–Aqikuduk suture zone (Charvet et al, ; Charvet et al, ; Shu et al, ), which even might continue to the west along the Nalati–Kekesu–Atbashy–Inylchek zones (Charvet et al, ; Charvet et al, ; Dong et al, ; Lin et al, ; Wang et al, ; Wang et al, ; Wang et al, ).…”

Section: Geological Backgroundmentioning

confidence: 99%

The youngest Permian Ocean in Central Asian Orogenic Belt: Evidence from Geochronology and Geochemistry of Bingdaban Ophiolitic Mélange in Central Tianshan, northwestern China

Liu

Zhang

et al. 2019

The Tianshan Belt, which lies in the southwest part of Central Asian Orogenic Belt (CAOB), is characterized by abundant ophiolites or ophiolitic mélanges, which are indicators of the existence of oceanic basin can be used for tracking the tectonic evolutionary history of the orogen. The Bindaban (BD) ophiolitic mélange is located in the Central Tianshan Belt, northwest China, which comprises mainly gabbros, diabases, basalts, basaltic lavas (greenschist), and cherts. This paper presents new zircon geochronology, whole‐rock major and trace elements, and Sr, Nd isotope data for mafic rocks in the BD ophiolitic mélanges. In the eastern part of BD ophiolitic mélanges, one normal (N)‐MORB‐type basalt has a U–Pb zircon age of 265.2 ± 1.8 Ma, and one enriched‐MORB‐type dolorite in the western part of BD ophiolitic mélanges has an age of 425.4 ± 3.9 Ma, respectively, indicating either an existing ocean basin from continental rifting to normal oceanic spreading with a long time span from late Silurian to Permain, or two separate ocean basins that formed in late Permian and late Silurian during the Paleo‐Tianshan Ocean evolution. In particular, the 265.2 ± 1.8 Ma age of N‐MORB‐type basalt from BD ophiolitic mélange suggests the youngest oceanic basin (late Permian) existed in southwest CAOB, which reveals that Paleo‐Asian Ocean might last to late Permian, therefore finally closed in or after the late Permian in the North Tianshan area.

“…The Chinese Tianshan orogenic collage comprises the southwestern part of the Central Asian Orogenic Belt (CAOB; Şengör, Natal'in, & Burtman, ), which represents one of the largest accretionary orogens in the world (Cawood et al, ). It has been generally accepted that this orogenic collage underwent a complex subduction/accretion and orogenic process (Charvet et al, ; Gao et al, ; Gao, Li, Xiao, Tang, & He, ; Han & Zhao, ; Khain et al, ; Wang et al, ; Wang et al, ; Windley, Alexeiev, Xiao, Kröner, & Badarch, ; Xiao et al, , ; Xiao et al, ; Xiao et al, ; Xiao, Windley, Allen, & Han, ), which were closely associated with the evolution of three possible major ocean basins once existed, the possible Early Palaeozoic Turskey Ocean (Qian et al, ), the North Tianshan Ocean (NTO; also the Junggar Ocean), and the South Tianshan Ocean (STO; also termed Turkestan Ocean). The latter two oceanic basins have been generally regarded as the main branches of the Paleo‐Asian Ocean (PAO), and were the focus of research during the past several decades (see review by Han & Zhao, ).…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, other authors proposed a roughly synchronous closure of both oceans, but with different opinions on the duration of these oceans, either in the Late Carboniferous (Gao et al, ; Han et al, ; Han, He, Wang, & Guo, ; Klemd, Gao, Li, & Meyer, ) or in the Late Permian to mid‐Triassic (Xiao et al, ; Zhang et al, ). In addition, while traditional models invoke a one‐side, northward subduction of the STO (e.g., Gao et al, , ; Xiao et al, ), several recent studies of the South Tianshan ophiolites (e.g., Jiang et al, ; Wang et al, ; Wang et al, ) and magmatism along the northern margin of the Tarim Block (Ge et al, ; Lin et al, ; Zhao et al, ) indicate southward subduction of this ocean as well.…”

Section: Introductionmentioning

confidence: 99%

Petrogenesis of Carboniferous volcanic rocks from the Gangou area, Chinese North Tianshan: Constraints on the evolution of the North Tianshan Ocean

Yang

Gong

et al. 2019

The time duration and evolution of the major North Tianshan Ocean (also the Junggar Ocean) in the Chinese Tianshan orogenic collage remain poorly constrained. Here we report new geochronological and geochemical data of Carboniferous volcanic rocks documented from the North Tianshan accretionary complex in the Gangou area (Xinjiang, NW China). The studied rocks include basaltic andesites and andesites, with one andesite yielding a zircon U–Pb age of 332 ± 4 Ma. This reflects nearly synchronous eruption of the volcanics with the formation of host Early Carboniferous Yamansu Formation. These rocks are mostly tholeiitic in compositions, with a few samples transitioning to calcalkaline. All the samples show enriched LREE and LILE but depleted HFSE, a ubiquitous subduction signature observed in supra‐subduction zone volcanics. The positive εNd(t) (+5.2 to +6.7) and low initial 87Sr/86Sr (0.7038 to 0.7040) in these rocks suggest derivation from a MORB‐depleted peridotite source. However, the overall low MgO contents (and Mg#) in these rocks compared with typical high‐Mg andesites indicate that they are less likely formed via simple melting of metasomatized mantle wedge peridotites. Instead, partial melting of mafic‐ultramafic metasomes (e.g., pyroxenites) formed by slab melts/fluids‐peridotite interactions may explain these rocks. The studied rocks share many geochemical similarities with those Early Carboniferous volcanic rocks widely documented from the Chinese Western Tianshan and those volcanics from typical continental arcs (e.g., the Gangdese arc). Therefore, we suggest the volcanic rocks, combining with recent results from the North Tianshan ophiolites, tend to support a continued southward subduction of the major North Tianshan Ocean from the Cambrian to the Carboniferous periods.