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Article

Geochronology and Petrogenesis of Ahetala Granodiorite in South Tianshan Orogenic Belt, Xinjiang: New Constraints on the Tectonic Evolution of the South Tianshan Ocean

1
Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China
2
Institute of Earth Science, China University of Geosciences, Beijing 100083, China
3
Institute of Geological Survey, China University of Geosciences, Wuhan 430074, China
*
Authors to whom correspondence should be addressed.
Minerals 2022, 12(12), 1588; https://doi.org/10.3390/min12121588
Submission received: 30 October 2022 / Revised: 1 December 2022 / Accepted: 5 December 2022 / Published: 11 December 2022
(This article belongs to the Special Issue Petrology and Geochemistry of Igneous Complexes and Formations)

Abstract

:
The Ahetala granodiorite is located in the western section of the South Tianshan Orogenic Belt (STOB), which is of great significance regarding the dispute on the closing date of the South Tianshan Ocean (STO) and the tectonic evolution of STOB. To determine the tectonic setting and petrogenesis, the study of petrography, electron probe microanalysis (EPMA), LA-ICP-MS zircon U–Pb geochronology, and major and trace elements analyses are carried out for Ahetala granodiorite. Based on LA-ICP-MS U–Pb zircon dating, the granodiorite was emplaced at 282.1 ± 1.3 Ma (MSWD = 1.11). Geochemically, Ahetala granodiorite is characterized by metaluminous (A/CNK = 0.86–0.87), rich alkali (K2O + Na2O = 6.80–7.13), which belongs to high-K calc-alkaline I-type granite. They are enriched in LREE and depleted in HREE (LREE/HREE = 9.02–13.89) and exhibit insignificant Eu anomalies (δEu = 0.94–0.97). Ahetala granodiorite is enriched in large ion lithophile elements (e.g., K, Sr, Ba) and depleted in high field-strength elements (e.g., Ta, Ti, Nb, P). The Nb/Ta values (10.97–18.10), Zr/Hf values (39.41–40.19), and Mg# (54.87–56.02) of the granodiorite and the MgO content of biotites (13.42–14.16), the M value (M = Mg/(Mg + Fe2+)) of amphiboles (0.68–0.75), suggest that granodiorite originates from the crustal contamination of the mantle-derived magmas. Combined with regional geological background, previous research, and the nature of the Ahetala granodiorite, we suggest that Ahetala granodiorite was emplaced at a transitional stage of the volcanic arc (syn-collision) to post-collision setting and the South Tianshan Ocean was closed in the Early Permian.

1. Introduction

The Central Asian Orogenic Belt (CAOB) is one of the essential metallogenic belts in the world and was developed by the closure of the Paleo-Asian Ocean [1,2,3,4,5]. Based on the evidence of ophiolite mélanges, high-ultrahigh pressure metamorphic belts, etc., different studies indicated that the Ancient Tianshan Ocean (Terskey Ocean), the North Tianshan Ocean (Junggar Ocean), and the South Tianshan Ocean (STO) together constitute the southwestern part of the Paleo-Asian Ocean [1,6,7]. The formation, evolution, and extinction of the Paleo-Asian Ocean were accompanied by the multiple accretionary and collisional events of many landmasses (Siberia, Tarim, etc.). The South Tianshan Orogenic Belt (STOB) was formed after the northward subduction of the Tarim Craton underneath the Yili-Central Tianshan plate and the closure of the STO [8,9,10,11,12,13,14]. The formation of the STOB may mark the termination of the central Asian accretionary orogenesis because the Tarim Craton is regarded as the last plate on CAOB following the final closure of the STO [15,16]. Therefore, it is critical to recognize the history of STO.
In order to identify the petrogenesis and tectonic setting, past studies used different methods and techniques to analyze ophiolite mélanges, high-ultrahigh pressure metamorphic minerals, fossils, detrital zircons, granites, etc., in STOB. It is widely accepted that the ophiolite is the direct product of the subduction and collision of oceanic and continental plates, so ophiolite has been used to analyze the subduction of the oceanic lithosphere and the formation and evolution of the arc basin system at the continental margin. According to Qiqijianake [17], Baleigong [18], Kulehu [19], Jigen [20], and Misibulake, Serikeyayibulake, Aertengkesibulake, Changawuzibulake [21], etc., ophiolite mélanges have been discovered in the STOB (Figure 1). It can be seen that these ophiolite mélanges are aged between 390 and 450 Ma, which implies that the Paleozoic ocean basin still existed in the STO during the Silurian to Devonian. Eclogites from the ultra-high pressure metamorphic belt in the southwest Tianshan confirm that the oceanic crust subducted at the Permian (280–290 Ma) [22]. Radiolarian fossils in the Wupatarkan and Aiketike group indicate that the ancient ocean basin may have existed in the STO during the Permian period [23,24].
In addition, different studies have mainly focused on the granitic magmatic activity in STOB. The Chuanwulu igneous complex (286.4 ± 2.5 Ma [25]), Baleigong granite (273 ± 2 Ma [26], 291 ± 3 Ma, 283 ± 3 Ma [27]), and Huoshibulake granite (261.5 ± 2.7 Ma [28], 276 ± 4 Ma [29]), etc., have been discovered in the STOB (Figure 1). The formation of granite was closely related to the tectonic environment and geodynamic process. It is believed that Late Paleozoic collisional granites in this area were formed by the collision between the Tarim Craton and Yili-Central Tianshan plate. However, most of these granites are A-type granites. There are few reports concerning the research of I-type granites in the STOB, which restricts a comprehensive understanding of the tectonic evolution in the STO. The most fundamental question regarding the closure time of the STO is still under debate. Past studies constrain the three possible closure time of STO: prior to the Permian [25,30,31,32,33,34,35], during the Permian [10,23,24,26,36,37,38], and during the Triassic [15,22,39,40,41].
The I-type granodiorite intrusion was discovered at the Ahetala copper deposit in the STOB, which was related to the subduction of the Tarim plate and closure of the STO. To add some insightful information to the above disputes and comprehensively discuss the tectonic evolution and closing time of STO, we systematically sampled and analyzed zircon U–Pb ages, the chemical composition of rock-forming minerals, and the major, trace elements of the Ahetala granodiorite.

2. Geological Setting

The CAOB (i.e., the Altaid Collage [5]) is the largest Phanerozoic accretionary orogen in the world. It is sandwiched between the Eastern European, Siberian, Tarim, and North China Cratons (Figure 1a). Traditionally, the CAOB is subdivided into eastern and western parts by taking 88° E as the boundary. The western CAOB comprises the Altai Mountain, Junggar Basin, Tianshan Mountains, and Tarim Basin [25,52]. The Tianshan Mountains are located in the southern margin of the western CAOB (Figure 1a), extending for ca. 2500 km from the Aral Sea in Uzbekistan to north Xinjiang in China [35,48]. Tectonically, the Tianshan Mountains can be divided into four geological units from south to north: (1) northern margin of Tarim Craton, (2) STOB, (3) Central Tianshan Block (CTB), and (4) North Tianshan Orogenic Belt (NTOB). The STOB is bounded by the Yili-Central Tianshan Suture Belt in the north and the North Tarim Fault in the south (Figure 1b) [25].
The STOB is regarded as a collisional belt and separates the Central Tianshan plate and the Tarim Craton [1,8,9,25,53], which is related to the closure of the STO. Many high-ultrahigh pressure metamorphic rocks (blueschist-, eclogite-, and greenschist-facies meta-sedimentary rocks) have been found in Paleozoic ophiolites/ophiolitic mélanges along the STOB, which has a connection with the closure of the STO [10,27]. The emplacement date of the basic-ultrabasic igneous rocks in ophiolite mainly from the Silurian to the Devonian periods.
The base of the STOB in China is the metamorphic rocks of the Paleo-Proterozoic Xingditagh Formation, which is covered by the Middle Proterozoic Akesu Formation [54]. The South Tianshan mainly includes the Cambrian to Carboniferous and Cenozoic strata [55]. Early Paleozoic limestone, clastic sedimentary rocks, and volcanic rocks are widespread in the STOB. The Cambrian, Ordovician, and Silurian strata are mainly carbonate and clastic rocks. The Devonian strata are mainly clastic sedimentary rocks, volcanic rock, and carbonatite. The Carboniferous strata are mainly sandstone, shale, slate, and limestone.
Most of the outcrop of igneous rocks are granitiods that cover almost 5% of the total STOB [25]. The emplacement age of most intrusive rocks ranges from the Late Carboniferous to Early Permian. The STOB was uplifted by collision and orogeny. In this period, the orogenic magmatic activity gradually decreased and the post-orogenic or non-orogenic magmatic activity increased. From the Heiying mountain to Aheqi county, the intrusive rocks often come into contact with surrounding rocks, thus forming skarn.

3. Local Geology and Petrography

The study area is located about 50 km to the northwest of Aheqi County, Kirgiz Autonomous Prefecture, Xinjiang Uygur Autonomous Region of China. The Ahetala granodiorite is located in the south of the Kokshal anticlinorium and at the juncture of the Toshihan fault and the Tatiertashiqiaoke inverse fault. The granodiorite is related to the mineralization of the skarn copper deposit. The strata in the study area mainly include: (1) the bioclastic limestone and marble of the Tuoshihan Formation. The marble and granodiorite contact in the center of the study area, which is closely related to the mineralization of the copper deposit; (2) the conglomerate, muddy siltstone, and silty mudstone of the Wuqia formation [56,57].
The study area consists of a monoclinal structure with SE dip angle of 15–30°. Several NNW faults are developed and have a relatively significant influence on the area. The Ahetala granodiorite is exposed as stock intrudes into the marble of the Toshihan Formation. The east of the granodiorite is covered by the conglomerate of the Wuqia Formation [56,57] (Figure 1c and Figure 2).
The outcrops define an oval shape with an area of ~0.21 km2. The skarn is observed at the contact belt between the intrusion and surrounding rock. All specimens were sampled at different locations along the strike of Ahetala granodiorite. According to field (Figure 3a) and microscopic observations, the intrusion is granodiorite. Unweathered samples (Figure 3b) in this study show a medium-fine-grained texture and massive structure and are mainly composed of plagioclase (~45–50 vol.%), potassium feldspar (~15–20 vol.%), quartz (~20–25 vol.%), hornblende (~5 vol.%), and biotite (~5 vol.%) with accessory magnetite, zircon, apatite, and titanite (Figure 3c–f). Plagioclase grains are white, euhedral, or hypidiomorphic, with a large diameter, and generally display oscillatory zoning (Figure 3c–f). Potassium feldspars are colorless and have a typical polysynthetic twin (Figure 3c,d). Biotite is brown, plate-like, and shows a clear cleavage {001} (Figure 3e,f). Hornblende is light brown and fusiform (Figure 3d,f).

4. Analytical Techniques

4.1. Zircon U–Pb Dating

Zircons were separated from five samples of granodiorite for Laser Ablation-Inductively Coupled Plasma-Mass Spectrometer (LA-ICP-MS) U–Pb age dating. The zircon grains were separated through conventional density and magnetic separation techniques and carefully picked under the binocular microscope. High quality zircons were selected, mounted in epoxy resins, and finally, polished for analysis. All zircons were studied under transmitted and cathodoluminescence (CL) imaging to observe the morphology and internal structures and to select spots for U–Pb dating. The above work was completed at Beijing GeoAnalysis Co., LTD. (Beijing, China).
The zircon U–Pb dating was tested with an X Series 2 ICP-MS, analyzed with 32 μm laser spot diameter at a frequency of 6 Hz, and housed at the LA-ICP-MS Laboratory of the Institute of Earth Sciences of the China University of Geosciences (Beijing, China). Zircon 91 500 was used as the reference sample for U–Pb dating and optimizing the instrument. A standard zircon mud tank was used for the monitoring sample. The experimental data were processed by ICPMSDataCal software [58].

4.2. Mineral Geochemistry

Fresh samples of granodiorite were selected for making thin sections without coverslip. The surface of the thin section was coated with carbon for better conductivity in the experiment. The chemical composition of rock-forming minerals in granodiorite was analyzed with EPMA-1600 at the China University of Geosciences (Beijing, China). During the electron probe microanalysis, the acceleration voltage was 15 kV and the beam current was 1 × 10−8 A. All the standard samples conformed to the SPI standard of the USA in the experiment.

4.3. Whole-Rock Analyses

Five fresh samples of granodiorite were selected for whole-rock analysis. Major elements were analyzed by Leeman Prodigy ICP-OES, and trace and rare-earth elements were analyzed by Agilent Technologies ICP-MS-7500a at the Experimental Testing Centre of the Institute of Earth Sciences of the China University of Geosciences (Beijing, China). The final results were processed using Agilent 7500a software.

5. Results

5.1. Zircon U–Pb Geochronology

The results of zircon U–Pb dating from the Ahetala granodiorite are shown in Table 1. In CL images (Figure 4a), twenty zircons are colorless, euhedral, and prismatic with clear oscillatory zoning and no inclusions. The lengths of zircon are mostly in the range 100–150 μm, and their length/width ratios are close to 2:1. AHTL-19 displays discordant older 206Pb/238U age, and it is likely to be a xenocrystal. In addition, AHTL-2, -4, -7, and -13 are all below the concordia line of U–Pb zircon, which is caused by lead loss. The concordance of AHTL-2, -4, -7, -13, and -19 are less than 95%. In order to improve the reliability and accuracy of the experimental results, AHTL-2, -4, -7, -13, and -19 were not involved in zircon U–Pb dating (Figure 4b). The zircon samples show 280.3 to 857.76 ppm (average of 500.94 ppm) for Th and 489.91 to 1270.99 ppm (average of 746.59 ppm) for U. Fifteen zircons have high Th/U ratios (0.58~0.75) and typical oscillatory zoning, implying magmatic origin. All spot analyses show concordant ages from 273 to 290 Ma with a weighted mean 206Pb/238U age of 282.1 ± 1.3 Ma (MSWD = 1.11), which is considered to represent the emplacement age of the granodiorite (Figure 4c).

5.2. Mineral Geochemistry

5.2.1. Plagioclase

As the main rock-forming mineral in Ahetala granodiorite, plagioclase can be used to study petrogenesis and magmatic evolution. The plagioclase samples show 56.47 to 58.78 wt.% for SiO2; 24.69 to 26.14 wt.% for Al2O3; 6.88 to 8.43 wt.% for CaO; 7.00 to 7.82 wt.% for Na2O; 31.66 to 38.84% for the An (anorthite) end-member; 58.36 to 65.11% for the Ab (albite) end-member; and 2.31 to 4.00% for the Or (orthoclase) end-member (Table 2). In the plagioclase, the An end-member is decreases and Ab end-member increases from core to rim (Figure 5a). The core is enriched in alkali, and the rim is enriched in acid.

5.2.2. Potassium Feldspar

The potassium feldspar samples show 62.32 to 63.24 wt.% for SiO2; 19.05 to 19.57 wt.% for Al2O3; 13.48 to 13.82 wt.% for K2O; 0.44 to 1.30% for An; 21.10 to 21.79% for Ab; and 77.50 to 78.43% for Or (Table 3). All potassium feldspar is orthoclase (Figure 5a).

5.2.3. Biotite

The biotite samples show 35.52 to 36.25 wt.% for SiO2; 14.77 to 14.91 wt.% for Al2O3; 15.52 to 16.22 wt.% for TFeO; and 13.42 to 14.16 wt.% for MgO (Table 4). The biotite in Ahetala granodiorite belongs to magnesium biotite (Figure 5b).

5.2.4. Hornblende

The hornblende of granodiorite samples show 46.05 to 48.63 wt.% for SiO2; 5.69 to 7.80 wt.% for Al2O3; 13.08 to 14.23 wt.% for TFeO; 13.89 to 15.49 wt.% for MgO; and 11.27 to 11.56 wt.% for CaO (Table 5). All hornblende in granodiorite belongs to the edenite group (Figure 5c).

5.3. Whole-Rock Geochemistry

The results of major, trace and rare earth elements of five samples are listed in Table 6.

5.3.1. Major Elements

The Ahetala granodiorite samples show 61.69 to 63.66 wt.% for SiO2; 3.26 to 3.42 wt.% for MgO; 0.16 to 0.28 wt.% for P2O5; 3.65 to 4.11 wt.% for Na2O; and 2.82 to 3.32 wt.% for K2O. All the samples have a high content of K2O + Na2O (6.80–7.13 wt.%) and relatively low A/CNK ratios (0.86–0.87) (Table 6), indicating a calc-alkaline, metaluminous affinity. Granodiorite has low TFe2O3/MgO ratios (1.40–1.47) and high Mg# values (54.87–56.02) (Mg# = 100 × Mg/(Mg + Fe2+)).
All the samples in the SiO2 vs. Na2O-K2O diagram belong to granodiorite (Figure 6a). The results are consistent with the Q-A-P diagram of intrusive rocks and petrographic observations. In A/NK vs. A/CNK diagram, all the studied samples are plotted in the metaluminous field (Figure 6b). All the samples are plotted in the field of high-k calc-alkaline in the SiO2 vs. K2O diagram (Figure 6c). To sum up, Ahetala granodiorite belongs to high-K calc-alkaline granite.

5.3.2. Trace Elements

The primitive mantle normalized trace element diagrams show that the Ahetala granodiorite is relatively enriched in large ionic lithophile elements (LILEs), such as K, Sr, and Ba, and relatively depleted in high field strength elements (HFSEs), such as Nb, Ta, and Ti (Figure 7a). Yb + Nb range from 16.16 to 18.36; Nb/Ta range from 10.97 to 18.10; Rb/Sr range from 0.07 to 0.17; and Zr/Hf range from 39.41 to 40.19 (Table 6).
The total rare earth elements (ΣREE) of Ahetala granodiorite concentrations range from 78.42 to 180.28 ppm with an average of 144.83 ppm. The contents of light rare earth elements (LREE) are between 70.60 to 167.01 ppm with an average of 133.75 ppm. The contents of heavy rare earth elements (HREE) are between 7.82 to 13.27 ppm with an average of 11.08 ppm. The LREE/HREE ranging from 9.02 to 13.89. LREE are enriched relative to HREE in the chondrite-normalized REE diagram (Figure 7b) with (La/Yb)N ratios ranging from 7.53 to 18.60. The distribution of rare earth elements is a standard right-leaning pattern, and HREE display a relatively flat distribution pattern. The negative Eu anomaly is not obvious (δEu = 0.94–0.97) and is likely affected by the fractionation of plagioclase during the magmatic evolution.

6. Discussion

6.1. Petrogenesis

6.1.1. Geochemical Affinities

All studied samples belong to granodiorite in the TAS diagram (Figure 6a), consistent with petrographic observations. All of the samples are enriched in the K and calc-alkaline series (Figure 6c), which are different from M-type granites that have low K (<1%) [66]. Further, the Ahetala granodiorite belongs to the high-K series (Figure 6c) and has low Nb contents, 10,000 Ga/Al ratios (Figure 8a), TFeO/MgO ratios, Zr+Ce+Y+Nb contents (Figure 8b), and K2O+Na2O/CaO ratios, which preclude them from A-type granite [67,68,69]. Ahetala granodiorite is characterized by low differentiation indices (DI = 64.85−66.41) and is plotted in the field of unfractionated I-, S-, and M-type granites (Figure 8a,b). S-type granites generally have aluminum-rich minerals, such as cordierite, muscovite, tourmaline, and garnet [70]. However, mineralogical observation did not find these minerals in Ahetala granodiorite. The MF value of biotite (MF = [Mg/(Mg + Fe + Mn)] can also be used to distinguish S-type and I-type granite (S-type grantie < 0.5, I-type granite > 0.5 [71]). The MF value of Ahetala granodiorite is ~0.6, thus showing the characteristics of I-type granite.
In addition, the low A/CNK ratios, the negative correlation between P2O5 and SiO2 (Figure 9a), and the positive correlation between Rb and Th, Rb, and Y (Figure 9b,c) indicate the petrogenesis of I-type granites and preclude Ahetala granodiorite from being S-type granite [72,73]. In summary, our petrographic observations and geochemical evidence suggest that Ahetala granodiorite is I-type granite.

6.1.2. Magma Source

Geochemically, the electron probe microanalysis of rock-forming minerals is helpful when analyzing the magmatic source. The An contents of plagioclase decreases with fluctuation from the core to rim, which shows the characteristics of a normal zoning, indicating that the plagioclase was directly formed by the crystallization of mixed magma [74]. The MgO content of biotite from the crust is usually lower than 6 wt.%, while that from the mantle is generally higher than 15% [75,76]. The MgO content of biotites in all the samples is 13.42–14.16 wt.%, which reflects the characteristics of a crust–mantle mixed source (Table 4). In addition, the M value (M = Mg/(Mg + Fe2+)) of amphiboles can also be used to distinguish the magmatic source [77]. The M value of all amphiboles ranging between 0.68 and 0.75 (0.5 < M < 0.7 for crust–mantle type granite and M > 0.7 for mantle type granite) indicates that Ahetala granodiorite has the characteristics of the crust–mantle mixed source. The TFeO/(TFeO + MgO) vs. MgO diagram (Figure 10a) shows that all biotites belong to crust–mantle mixed sources [78]. In the Al2O3 vs. TiO2 diagram, all amphiboles are plotted in the field of the crust–mantle mixed source (Figure 10b). The Nb/Ta ratios of Ahetala granodiorite (10.97–18.10) are similar to those of the crust (~11–12) and mantle (~17.5) [79], indicating that granodiorite is of crust–mantle mixed origin. The Zr/Hf ratios of Ahetala granodiorite (39.41–40.19) are similar to the value of MORB (~36) [65], indicating that mantle-derived material may indeed be involved in magmatic evolution. The Th/U ratios of granodiorite ranging from 2.81 to 6.18 (average of 5.17), which are similar to the lower crust (Th/U = 5.48) [80,81]. Previous studies have shown that magmas with Mg# > 40 are related to the involvement of a mantle component [82], which is consistent with the Mg# (54.87–56.02) of the Ahetala granodiorite. The SiO2 (61.69%–63.66%) and Al2O3 (15.45%–16.29%) values; enriched Zr and Hf; and depleted Nb, Ta, and Ti in samples indicate that mantle-derived materials contribute to magmatic evolution [83].
In addition to the above characteristics, all the plotted samples fall within the field of high-K mafic rocks (Figure 10c), which indicates that the magma may originate from the mafic magmas [84]. Similarly, Ahetala granodiorite shows an obvious tendency towards partial melting (Figure 10d–f). The above geochemical features indicates that the Ahetala granodiorite is mainly generated from the crustal contamination of the mantle-derived mafic magmas.

6.2. Emplacement Age and Tectonic Setting

The STOB is widely accepted as a Paleozoic collision belt formed by the collision of the Tarim Craton and Yili-Central Tianshan block. It has undergone subduction, accretion, collision, crust thickening, and extension-thinning [10,34,35]. However, direct geological evidence of the evolutionary process of STOB was almost eradicated in the subsequent geological evolution. Therefore, it is difficult to infer the evolutionary process of the STO, resulting in controversy about the closing time of the STO and the tectonic setting of the Permian in south Tianshan. Some studies have proposed that the STO was a post-collision setting in the Early Permian (the closure of the STO occurred before the Early Permian) [35,54]. In contrast, others believe it is a volcanic arc setting related to subduction (the closure of the STO occurred in or after the Early Permian) [15,23]. The formation time of tectonic suture belt can be constrained through the youngest ophiolite and the earliest pluton or dikes intruding into the suture belt [13]. Previous studies have shown that the age of the south Tianshan ophiolite belt is 450 Ma to 392 Ma, and these ophiolites belong to supra-subduction zone (SSZ) type ophiolites [17,18,19], which suggests that the south Tianshan oceanic crust had existed since the Silurian. Liu Bin et al. measured the Ar–Ar age (360 Ma) of the glaucophane in the Kumishi area, which indicates a northward subduction of the south Tianshan oceanic crust [88].
High-pressure/ultra-high pressure (HP-UHP) metamorphic belts in the STOB were considered to be the product of the collision between the Tarim Craton and the Yili-Central Tianshan plate [12,89]. Previous studies on the HP metamorphism have shown that the Late Carboniferous (320 Ma) is the initial collision and the upper age limit is 285 Ma [10]. Radiolarian fossils were discovered in the accretionary complex, which confirmed that the relic ancient oceanic basin existed in the western part of the STO during the Early Permian [23]. In the high-pressure metamorphic zone of the northern part of the STOB, the zircon ages of granulite range from 290 to 280 Ma, indicating that subduction finished in the STO during the Early Permian [90].
As shown in Figure 4, the result indicates that the age of granodiorite is 282.1 ± 1.3 Ma (n = 15, MSWD = 1.11), which reflects that granodiorite was emplaced in the Permian. This age is consistent with the emplacement time of granitic rocks in the Kokshal mountains (273~283 Ma) [91]. By studying the Paleozoic granites in the STOB, a large number of studies believe that the STOB was in a critical period of transition from the subduction to collision during the Late Carboniferous to the Early Permian [2].
All samples of Ahetala granodiorite plotted in the field of volcanic arc granites (VAG), syn-collision granites (syn-COLG), and post-collision granites (post-COLG) in the Y vs. Nb and Y + Nb vs. Rb diagrams (Figure 11a,b). In the R1 vs. R2 diagram, all samples plotted on the boundary between the pre-plate collision and post-collision uplift (Figure 11c). Three samples are plotted in the field of VAG, while the other two are plotted in the field of the late to post-orogenic calc-alkaline intrusions (COLG III) and within plate granites (WPG) in the 3Ta-Rb/30-Hf diagram (Figure 11d). In the Y/15-La/10-Nb/8 diagram, four samples are plotted on the boundary of the orogenic domains and late to post orogenic field and one sample is plotted in the late to post orogenic field (Figure 11e). In addition, biotites belong to calc-alkaline subduction-related biotites in the TFeO-MgO-Al2O3 discriminant diagram (Figure 11f) [92]. The enrichment of K, LREEs, and LILEs and the depletion in HFSE (Figure 7b) and minor Eu anomalies (δEu = 0.94–0.97) are signatures characteristically associated with subduction-related magmas [93]. Meanwhile, the negative anomalies of Nb, Ta, and Ti can be found in the primitive mantle-normalized spidergrams, which also indicate that Ahetala granodiorite has the characteristics of arc granites (Figure 7a). However, it is difficult to distinguish between tectonic settings using tectonic discrimination diagrams because they often reach ambiguous conclusions. Nevertheless, it is indisputable that the crust thickens due to the extrusion and collision in the collisional stage. High potassium granite implies crustal thickening after collision [50,94]. In addition, as described in Section 6.1.2, under the dynamic background of subduction and collision, the underplating of the mantle material is considered to be the main factor of crustal thickening [95]. It is only during this period that mantle-derived materials may participate in the magmatic evolution.
Therefore, according to the restriction of the geochemical affinities, magma source, and the multiple tectonic discrimination diagrams, the formation setting of Ahetala granodiorite is the transitional stage of the volcanic arc (syn-collision) and post-collision setting. This means that the STO in this region was closed in the Early Permian (282.1 ± 1.3 Ma).

6.3. Implication for the Tectonic Evolution of the STO

Many granitic rocks of the Late Carboniferan–Early Permian have been studied in STOB, and fruitful data have been accumulated. However, the tectonic evolution of the STOB in the Early Permian is still in debate, because it is not possible to determine the closing time of the STO only based on the evidence of the age and tectonic setting of such granites (most are A-type granites). These intrusions are almost evenly distributed in the STOB over more than 1500 km. No single granitic rock can prove the geodynamic setting of the whole STO in the Late Paleozoic.
Regarding the evolution of the STO in the Paleozoic, most studies argue that the south Tianshan oceanic crust subducted northward beneath the southern margin of the Yili-Central Tianshan plate during the Silurian to Middle Devonian [35,99,100]. Some previous studies believe that oblique collision played a vital role in the closing process of the STO in the late Paleozoic based on studies of large displacement strike-slip faults and paleomagnetism data [99,101]. Other relevant studies argue that the remnant basin of STO gradually closed from east to west in a “scissors-like” collision during the Late Carboniferous to Early Permian [102,103]. In the late Devonian, the eastern part of the Tarim Craton had already collided with the Yili-Central Tianshan plate, leaving a west-facing remnant oceanic basin [99]. Only the final consumption of the remnant oceanic crust means the end of the collision.
We have collected the data of granitic rocks from the Late Carboniferous–Early Permian in the STOB (Table 7). Most are intermediate-acidic metaluminous magmatic rocks (Figure 6), belonging to WPG (A-type granites) and formed in the post-collision (extensional) setting (Figure 8 and Figure 11). The age of these collision-related granites ranging from 261.5 ± 2.1 Ma to 304.2 ± 11.6 Ma, with an average of about 284.4 Ma (Figure 12). The ages of post-collision granites of the eastern part are older than the western part in the STOB. This finding means that the eastern part of STO developed into a post-collision setting earlier than the western part. When the Ahetala granodiorite was formed (282.1 ± 1.3 Ma), the western segment of the STO was still in the transitional stage of the volcanic arc (syn-collision) and post-collision setting. This conclusion also demonstrates the possibility of a “scissors-like” collision of the STO.
Chen et al. also believe that the “scissors-like” collision of the Tarim Craton with the Yili-Central Tianshan plate gave rise to the lithosphere-scale strike-slip and formed the northern Tarim Early Permian magmatic arc [99]. This view is also consistent with the conclusion that Ahetala granodiorites have the characteristics of volcanic arc granite and were formed during the transitional stage between the volcanic arc (syn-collision) and the post-collision setting. Combined with previous research and the nature of Ahetala granodiorite, we believe that the western part of STO, where Ahetala granodiorite is located, was closed in the Early Permian. The Tarim Craton and Yili-Central Tianshan plate were fully amalgamated in the Early Permian (Figure 13).

7. Conclusions

Based on experimental data of Ahetala granodiorite in this paper and previous research results on the Late Paleozoic tectonic evolution in the STOB, we reach the following conclusions:
  • The LA–ICP-MS U–Pb dating of zircons from Ahetala granodiorite yielded a precise crystallization age of 282.1 ± 1.3 Ma (MSWD = 1.11).
  • Ahetala granodiorite belongs to the high-K calc-alkaline series I-type granitoid.
  • Ahetala granodiorite was triggered by the crustal contamination of the mantle-derived magmas, which involved the mixing of crust- and mantle-derived materials.
  • Ahetala granodiorite was emplaced in the transitional stage of the volcanic arc (syn-collision) and the post-collision setting, indicating the STO was closed in the Early Permian.

Author Contributions

Conceptualization, Y.X. and J.Y.; investigation, J.Y., H.X., J.F. and M.F.; data curation, Y.X.; writing—original draft preparation, Y.X.; writing—review and editing, Y.X., J.Y. and C.W.; project administration, J.Y.; funding acquisition, J.Y. and K.X. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported by the National Key Technology Research and Development Program (2017YFC0601500).

Data Availability Statement

The experimental data used to support the conclusions of this study are included within the article.

Acknowledgments

Thanks to Jinhua Hao, Li Su, Wang Kunming, Shen Lijian, Yuwei Gao, Zhenhua Zhang, Fei Zhao, Piao Zhang, Yandong Sun, and other geologists and scholars for their guidance and help. Thanks to the editorial department for its valuable comments and suggestions for revision.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. (a) Sketch map of orogenic collages in Asia (modified from [5]); (b) distribution map of granitoid rocks and ophiolite in the STOB (modified from [25]); (c) regional geological sketch map of the Aheqi county (modified from [23]). Data sources: ①: [25]; ②: [26,27]; ③: [28,29]; ④–⑤: [29,42]; ⑥: [43]; ⑦: [44]; ⑧: [38,45]; ⑨: [45]; ⑩: [46]; ⑪: [47]; ⑫–⑲: [48,49,50,51]; ❶: [20]; ❷: [17]; ❸: [18]; ❼: [19], ❹–❽: [21].
Figure 1. (a) Sketch map of orogenic collages in Asia (modified from [5]); (b) distribution map of granitoid rocks and ophiolite in the STOB (modified from [25]); (c) regional geological sketch map of the Aheqi county (modified from [23]). Data sources: ①: [25]; ②: [26,27]; ③: [28,29]; ④–⑤: [29,42]; ⑥: [43]; ⑦: [44]; ⑧: [38,45]; ⑨: [45]; ⑩: [46]; ⑪: [47]; ⑫–⑲: [48,49,50,51]; ❶: [20]; ❷: [17]; ❸: [18]; ❼: [19], ❹–❽: [21].
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Figure 2. Geological map of Ahetala granodiorite with its main lithologic units (modified from [56,57]).
Figure 2. Geological map of Ahetala granodiorite with its main lithologic units (modified from [56,57]).
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Figure 3. Field photographs and the microscopic images of granodiorite samples. (a,b) Photographs of intrusive rock and sample of Ahetala granodiorite; (c,d) photomicrograph (cross-polarized light) of typical granodiorite texture; (e,f) photomicrograph (plane-polarized light) of typical granodiorite texture. Abbreviations are as follows: Q—Quartz; Bi—Biotite; Pl—Plagioclase; An—Anorthite; Kfs—Potassium feldspar; Hbl—Hornblende; Ap—Apatite.
Figure 3. Field photographs and the microscopic images of granodiorite samples. (a,b) Photographs of intrusive rock and sample of Ahetala granodiorite; (c,d) photomicrograph (cross-polarized light) of typical granodiorite texture; (e,f) photomicrograph (plane-polarized light) of typical granodiorite texture. Abbreviations are as follows: Q—Quartz; Bi—Biotite; Pl—Plagioclase; An—Anorthite; Kfs—Potassium feldspar; Hbl—Hornblende; Ap—Apatite.
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Figure 4. (a) Representative cathodoluminescence (CL) images of zircon grains; (b,c) 207Pb/235U–206Pb/238U concordia diagram and weighted average diagram of the Ahetala granodiorite.
Figure 4. (a) Representative cathodoluminescence (CL) images of zircon grains; (b,c) 207Pb/235U–206Pb/238U concordia diagram and weighted average diagram of the Ahetala granodiorite.
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Figure 5. (a) Microscopic photograph of plagioclase (Bar = 200 μm) and classification graph of feldspar [59]; (b) back scattered electron (BSE) photograph and classification graph of biotite (Bar = 95 μm) [60]; (c) microscopic photograph and classification diagram of hornblende (Bar = 500 μm) [61]. Pl—Plagioclase; Q—Quartz; Kfs—Potassium feldspar; Bi—Biotite; Hbl—Hornblende.
Figure 5. (a) Microscopic photograph of plagioclase (Bar = 200 μm) and classification graph of feldspar [59]; (b) back scattered electron (BSE) photograph and classification graph of biotite (Bar = 95 μm) [60]; (c) microscopic photograph and classification diagram of hornblende (Bar = 500 μm) [61]. Pl—Plagioclase; Q—Quartz; Kfs—Potassium feldspar; Bi—Biotite; Hbl—Hornblende.
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Figure 6. (a) TAS diagram [62]; (b) A/NK vs. A/CNK diagram [63] (A/CNK = Al2O3/(CaO + Na2O + K2O) molar, A/NK = Al2O3/(Na2O + K2O) molar); (c) K2O vs. SiO2 diagram [64]. Data sources: Chuanwulu [25]; Baleigong [26,27]; Kezile and Halajun [29,42]; Mazhashan [43]; Xiaohaizi [44]; Yingmailai [38,45]; Boziguoer [46]; Oxidaban [47]; Djangart, Kok- kiya, Mudryum, and Uchkoshkon [48,49,50,51]; Ahetala (this paper), as in figures in Section 6.1.1 and 6.2.
Figure 6. (a) TAS diagram [62]; (b) A/NK vs. A/CNK diagram [63] (A/CNK = Al2O3/(CaO + Na2O + K2O) molar, A/NK = Al2O3/(Na2O + K2O) molar); (c) K2O vs. SiO2 diagram [64]. Data sources: Chuanwulu [25]; Baleigong [26,27]; Kezile and Halajun [29,42]; Mazhashan [43]; Xiaohaizi [44]; Yingmailai [38,45]; Boziguoer [46]; Oxidaban [47]; Djangart, Kok- kiya, Mudryum, and Uchkoshkon [48,49,50,51]; Ahetala (this paper), as in figures in Section 6.1.1 and 6.2.
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Figure 7. (a) Primitive mantle-normalized spidergrams for Ahetala granodiorite; (b) chondrite-normalized REE patterns for Ahetala granodiorite. The normalized values are from [65].
Figure 7. (a) Primitive mantle-normalized spidergrams for Ahetala granodiorite; (b) chondrite-normalized REE patterns for Ahetala granodiorite. The normalized values are from [65].
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Figure 8. (a) 10,000 Ga/Al vs. Nb and (b) Zr+Ce+Y+Nb vs. TFeO+MgO [68]. I = I-type; S = S-type; M = M-type granite; FG = fractionated felsic granites; OGT = unfractionated I-, S-, and M-type granites.
Figure 8. (a) 10,000 Ga/Al vs. Nb and (b) Zr+Ce+Y+Nb vs. TFeO+MgO [68]. I = I-type; S = S-type; M = M-type granite; FG = fractionated felsic granites; OGT = unfractionated I-, S-, and M-type granites.
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Figure 9. (a) SiO2-P2O5 diagram; (b) Rb-Th diagram; and (c) Rb-Y diagram [72].
Figure 9. (a) SiO2-P2O5 diagram; (b) Rb-Th diagram; and (c) Rb-Y diagram [72].
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Figure 10. (a) The w(MgO)% vs. w(TFeO)%/w(TFeO + MgO)% diagram for the biotites [78]; (b) the w(TiO2)% vs. w(Al2O3)% diagram for the amphiboles [85]; (c) the Al2O3/(TFe2O3 + MgO) − 3 × CaO − 5 × (K2O/Na2O) diagram for the granitoid [84]; (d) La vs. La/Sm and (e) La vs. La/Yb [86]; (f) the Th vs. Th/Nd diagram [87].
Figure 10. (a) The w(MgO)% vs. w(TFeO)%/w(TFeO + MgO)% diagram for the biotites [78]; (b) the w(TiO2)% vs. w(Al2O3)% diagram for the amphiboles [85]; (c) the Al2O3/(TFe2O3 + MgO) − 3 × CaO − 5 × (K2O/Na2O) diagram for the granitoid [84]; (d) La vs. La/Sm and (e) La vs. La/Yb [86]; (f) the Th vs. Th/Nd diagram [87].
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Figure 11. (a) Y + Nb vs. Rb diagram; (b) Y vs. Nb diagram [96] (syn-COLG = syn-collision granites, VAG = volcanic arc granites, WPG = within plate granites, ORG = ocean ridge granites, post-COLG = post-collision granites); (c) R1 vs. R2 diagram [97] (R1 = 4Si − 11(Na + K) − 2(Fe + Ti), R2 = Al + 2Mg + 6Ca); (d) Rb/30-Hf-3Ta diagram [98]; (e) Y/15-La/10-Nb/8 diagram [93]; (f) TFeO-Al2O3-MgO diagram (A: anorogenic alkaline suites; C: calc-alkaline subduction-related suites; P: peraluminous (including S-type) suites) [92].
Figure 11. (a) Y + Nb vs. Rb diagram; (b) Y vs. Nb diagram [96] (syn-COLG = syn-collision granites, VAG = volcanic arc granites, WPG = within plate granites, ORG = ocean ridge granites, post-COLG = post-collision granites); (c) R1 vs. R2 diagram [97] (R1 = 4Si − 11(Na + K) − 2(Fe + Ti), R2 = Al + 2Mg + 6Ca); (d) Rb/30-Hf-3Ta diagram [98]; (e) Y/15-La/10-Nb/8 diagram [93]; (f) TFeO-Al2O3-MgO diagram (A: anorogenic alkaline suites; C: calc-alkaline subduction-related suites; P: peraluminous (including S-type) suites) [92].
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Figure 12. Distribution map of the age and geographic position of intrusions in the South Tianshan Orogenic Belt.
Figure 12. Distribution map of the age and geographic position of intrusions in the South Tianshan Orogenic Belt.
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Figure 13. Tectonic evolutionary schematic diagram of the South Tianshan Ocean in the Paleozoic.
Figure 13. Tectonic evolutionary schematic diagram of the South Tianshan Ocean in the Paleozoic.
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Table 1. LA–ICP-MS analytical data for zircons from samples of the Ahetala granodiorite.
Table 1. LA–ICP-MS analytical data for zircons from samples of the Ahetala granodiorite.
Samplew(Th)/10−6w(U)/10−6Th/U207Pb/235U206Pb/238U206Pb/238U
RatioRatioAge/MaMa
AHTL-1595.94 831.93 0.72 0.3259 0.0201 0.0458 0.0008 288.5 4.9
* AHTL-2814.47 1018.88 0.80 0.3254 0.0190 0.0417 0.0008 263.4 4.8
AHTL-3522.77 703.06 0.74 0.3177 0.0185 0.0437 0.0007 275.5 4.3
* AHTL-4637.86 903.94 0.71 0.3399 0.0221 0.0434 0.0008 274.0 4.9
AHTL-5670.53 898.12 0.75 0.3224 0.0211 0.0447 0.0009 281.7 5.5
AHTL-6402.10 590.27 0.68 0.3306 0.0232 0.0439 0.0011 277.0 6.6
* AHTL-7476.90 721.77 0.66 0.3396 0.0206 0.0421 0.0009 265.6 5.6
AHTL-8597.23 860.11 0.69 0.3267 0.0169 0.0455 0.0007 286.6 4.1
AHTL-9420.98 653.86 0.64 0.3183 0.0222 0.0444 0.0007 280.1 4.2
AHTL-10382.11 639.10 0.60 0.3248 0.0207 0.0449 0.0008 282.8 5.0
AHTL-11702.22 982.57 0.71 0.3240 0.0189 0.0452 0.0009 284.7 5.3
AHTL-12280.30 481.91 0.58 0.3226 0.0195 0.0460 0.0009 289.6 5.6
* AHTL-13525.82 754.34 0.70 0.3386 0.0214 0.0428 0.0009 269.9 5.4
AHTL-14444.02 699.12 0.64 0.3268 0.0188 0.0452 0.0008 284.7 5.0
AHTL-15389.34 581.77 0.67 0.3245 0.0228 0.0454 0.0009 286.1 5.4
AHTL-16857.76 1270.99 0.67 0.3408 0.0190 0.0454 0.0011 286.2 6.6
AHTL-17380.83 613.47 0.62 0.3202 0.0275 0.0432 0.0009 272.5 5.3
AHTL-18387.28 651.93 0.59 0.3379 0.0236 0.0460 0.0010 289.8 6.1
* AHTL-19679.26 980.13 0.69 0.3876 0.0204 0.0490 0.0012 308.3 7.1
AHTL-20480.76 740.62 0.65 0.3274 0.0188 0.0434 0.0008 273.8 4.7
* does not include zircon U–Pb dating.
Table 2. EPMA of plagioclase from Ahetala granodiorite.
Table 2. EPMA of plagioclase from Ahetala granodiorite.
Sample No.AHTL-Pl1AHTL-Pl2AHTL-Pl3AHTL-Pl4AHTL-Pl5AHTL-Pl6AHTL-Pl7AHTL-Pl8
Oxides (wt.%)
Core Minerals 12 01588 i001Rim
SiO256.9156.4757.4258.6858.0458.4258.7858.67
TiO20.08-0.010.100.16--0.20
Al2O325.9226.1425.7225.1925.1924.7825.0324.69
TFeO0.280.240.150.200.130.240.260.25
MnO-0.050.12-0.050.22--
MgO-----0.01-0.06
CaO8.438.408.077.197.397.016.996.88
Na2O7.007.067.237.817.567.647.657.82
K2O0.510.420.470.550.550.730.700.59
BaO0.260.320.41--0.120.17-
Σ99.3999.1099.6099.7299.0799.1799.5899.16
Structural formulae (a.p.f.u.) based on 8 oxygen atoms
Si2.592.582.602.642.642.652.652.66
Al1.391.411.371.341.351.331.331.32
Ca0.410.410.390.350.360.340.340.33
Na0.620.620.640.680.670.670.670.69
K0.030.020.030.030.030.040.040.03
Ba0.010.010.010.000.000.000.010.00
End-members (%)
An38.8438.7537.1732.7234.0232.3032.2631.66
Ab58.3658.9460.2664.3162.9763.7063.8965.11
Or2.802.312.582.983.014.003.853.23
“-” indicates that the detection limit is not reached, the same as below.
Table 3. EPMA of potassium feldspar from Ahetala granodiorite.
Table 3. EPMA of potassium feldspar from Ahetala granodiorite.
Sample No.AHTL-Kfs1AHTL-Kfs2AHTL-Kfs3AHTL-Kfs4AHTL-Kfs5
Oxides (wt.%)
SiO262.34 63.08 62.76 63.24 62.32
TiO21.19 1.07 0.64 0.83 1.02
Al2O319.29 19.29 19.05 19.25 19.57
TFeO0.10 0.19 0.22 0.16 0.05
MnO0.10 0.07 0.01 0.05 0.17
MgO-0.03 0.04 - 0.04
CaO0.13 0.09 0.11 0.17 0.27
Na2O2.49 2.39 2.55 2.49 2.43
K2O13.51 13.48 13.82 13.53 13.58
Σ99.14 99.69 99.20 99.72 99.45
Structural formulae (a.p.f.u.) based on 8 oxygen atoms
Si2.93 2.95 2.94 2.95 2.92
Al1.07 1.06 1.05 1.06 1.08
Ca0.01 0.01 0.01 0.01 0.01
Na0.23 0.22 0.23 0.23 0.22
K0.81 0.80 0.83 0.80 0.81
End-members (%)
An0.63 0.44 0.52 0.82 1.30
Ab21.74 21.13 21.79 21.68 21.10
Or77.63 78.43 77.69 77.50 77.60
Table 4. EPMA of biotite in Ahetala granodiorite.
Table 4. EPMA of biotite in Ahetala granodiorite.
Sample No.AHTL-Bi1AHTL-Bi2AHTL-Bi3AHTL-Bi4AHTL-Bi5
Oxides (wt.%)
SiO236.0836.2535.8035.5236.03
TiO24.104.424.434.304.50
Al2O314.7914.8114.8114.9114.77
TFeO15.7715.6215.6916.2215.52
MnO0.230.330.310.040.21
MgO14.1614.1213.9713.7113.42
CaO0.130.040.02-0.05
Na2O0.370.380.370.530.40
K2O9.259.179.279.339.18
Σ94.8895.1494.6794.5694.08
Structural formulae (a.p.f.u.) based on 11 oxygen atoms
Si2.732.732.722.712.74
AlIV1.271.271.281.291.26
AlVI0.050.050.040.050.07
Ti0.230.250.250.250.26
Fe3+0.150.170.160.130.19
Fe2+0.850.810.840.900.80
Mn0.010.020.020.000.01
Mg1.601.591.581.561.52
Ca0.010.000.000.000.00
Na0.050.060.050.080.06
K0.890.880.900.910.89
MF0.61 0.61 0.61 0.60 0.60
AlVI + Fe3+ + Ti0.430.470.450.420.52
Fe2+ + Mn0.860.830.860.910.81
Table 5. EPMA of hornblende in Ahetala granodiorite.
Table 5. EPMA of hornblende in Ahetala granodiorite.
Sample No.AHTL-Hbl1AHTL-Hbl2AHTL-Hbl3AHTL-Hbl4AHTL-Hbl5
Oxides (wt.%)
SiO248.6348.1546.9946.1846.05
TiO21.071.071.091.291.31
Al2O35.696.156.947.807.56
TFeO13.0813.2213.4114.2313.84
MnO0.300.280.490.440.37
MgO15.4914.9114.7513.8914.25
CaO11.5611.5211.3311.4311.27
Na2O1.401.561.731.731.74
K2O0.510.580.640.790.68
Σ97.7397.4497.3797.7897.07
Structural formulae (a.p.f.u.) based on 23 oxygen atoms
Si7.117.086.946.836.84
AlIV0.890.921.061.171.16
AlVI0.090.140.150.190.17
Ti0.120.120.120.140.15
Fe3+0.470.450.360.330.34
Fe2+1.131.181.301.431.38
Mn0.040.030.060.060.05
Mg3.383.273.253.063.16
Ca1.811.811.791.811.79
Na0.400.440.500.500.50
K0.100.110.120.150.13
Σ15.5315.5515.6415.6715.66
SiT 7.117.086.946.836.84
AlT0.890.921.061.171.16
AlC0.090.140.150.190.17
Fe3+C0.470.450.360.330.34
TiC0.120.120.120.140.15
MgC3.383.273.253.063.16
Fe2+C0.941.031.131.271.19
MnC0.000.000.000.000.00
Fe2+B0.190.150.170.160.19
MnB0.040.030.060.060.05
CaB1.781.811.771.791.76
NaB0.000.000.000.000.00
CaA0.030.000.030.020.03
NaA0.400.440.500.500.50
KA0.100.110.120.150.13
M0.75 0.73 0.71 0.68 0.70
Table 6. Major (in wt%), trace and rare earth element (in ppm) compositions of Ahetala granodiorite.
Table 6. Major (in wt%), trace and rare earth element (in ppm) compositions of Ahetala granodiorite.
Sample No.AHTL-1AHTL-2AHTL-6AHTL-7AHTL-8
SiO262.3563.6661.6962.7462.63
TiO20.560.540.580.530.55
Al2O315.9515.6716.2915.4515.78
TFe2O34.784.754.844.594.89
MnO0.050.070.060.060.07
MgO3.263.303.393.283.42
CaO4.644.654.884.704.79
Na2O4.113.724.083.653.73
K2O2.823.323.053.153.31
P2O50.240.220.280.160.22
LOI0.920.520.690.700.42
total99.68100.4299.8399.0199.81
Na2O + K2O6.937.047.136.807.04
A/NK1.621.611.631.641.62
A/CNK0.870.860.860.860.86
Mg#54.8755.3355.5356.0255.49
DI65.8366.4164.8565.8565.29
Ti34823532386634723506
Ga17.04417.58418.90217.49014.570
Rb801239610532
Sr767723829708481
Zr221222214216209
Nb1416171515
Cs3.1824.9843.4443.0963.586
Ba1130107713621089567
La3038404213
Ce6268807436
Pr7.3767.4249.0747.7643.766
Nd2725322614
Sm4.6364.2025.2204.2422.626
Eu1.3451.2431.5391.2450.790
Gd3.8763.5604.3643.5862.240
Tb0.5400.4900.5970.4900.343
Dy3.0162.7703.2902.7561.971
Ho0.6290.5800.6870.5760.427
Er1.7521.6161.9171.6031.218
Tm0.2560.2440.2860.2410.184
Yb1.7211.6221.8431.6131.242
Lu0.2670.2630.2850.2610.198
Hf5.6125.6115.3625.3695.274
Ta0.7981.2601.2771.3971.006
Pb25.20022.86025.06019.82619.358
Th10.93218.06413.40820.4605.142
U1.9143.5302.1683.4041.829
ΣREE144.35155.47180.28165.6478.42
LREE132.30144.33167.01154.5170.60
HREE12.0611.1413.2711.137.82
LREE/HREE10.9712.9512.5913.899.02
(La/Yb)N12.6816.8215.5418.607.53
δEu0.940.960.960.950.97
δCe0.980.940.980.931.26
Yb + Nb16.1617.5218.3616.9416.49
Nb/Ta18.1012.6212.9310.9715.16
Zr/Hf39.4139.6439.9540.1939.59
La/Yb17.6823.4521.6725.9310.50
Th/Nd0.410.720.420.790.37
La/Sm6.569.057.659.864.97
Th/U5.71 5.12 6.18 6.01 2.81
Rb/Sr0.100.170.120.150.07
Table 7. Late Carboniferous to Early Permian collision-related granitic intrusions in the South Tianshan Orogenic Belt.
Table 7. Late Carboniferous to Early Permian collision-related granitic intrusions in the South Tianshan Orogenic Belt.
PlutonDescriptionMethodAgeTypeEnvironment
Chuanwulu [25,45]Biotite dioriteLA-ICP-MS287.8 ± 4.3 MaIPost-collision
Biotite monzonite286.4 ± 2.5 Ma
Baileigong [26,27]Biotite moyiteLA-ICP-MS273 ± 2 MaA2Post-collision
291 ± 3 Ma
283 ± 3 Ma
Huoshibulake [28,29,45]Alkali-feldspar graniteID-TIMS261.5 ± 2.7 MaA1Post-collision
SHRIMP276 ± 4 Ma
Kezile [42]Biotite graniteLA-ICP-MS272.4 ± 1.1 MaA1Post-collision
Halajun [29,42]GraniteSHRIMP278 ± 3 MaA1Post-collision
Quartz syeniteLA-ICP-MS268.6 ± 1.5 Ma
268.8 ± 1.7 Ma
271.0 ± 2.2 Ma
Mazhashan [43]SyeniteSHRIMP285.9 ± 2.6 MaA1Post-collision
Xiaohaizi [44]SyeniteSIMS279.7 ± 2 MaAPost-collision
Yingmailai [38,45]Biotite monzonite graniteLA-ICP-MS285.0 ± 3.7 MaSSyn-collision-
Post-collision
291.0 ± 2.6 Ma
Boziguoer [46]GraniteLA-ICP-MS290.1 ± 1.4 MaAPost-collision
Oxidaban [47]Monzonitic graniteLA-ICP-MS273 ± 2 MaIPre-collision
Djangart [48,49,50,51]GraniteSIMS296.7 ± 4.2 MaA2Post-collision
Uchkoshkon [48,49,50,51]GraniteSIMS279 ± 8.1 MaA2Post-collision
Mudryum [48,49,50,51]GraniteSIMS281.4 ± 2.2 MaA2Post-collision
Kok-kiya [48,49,50,51]GraniteSIMS278.9 ± 2.7 MaA2Post-collision
Ak-Shiyrak [48,49,50,51]GraniteSHRIMP292 ± 3 MaA2Post-collision
Tashkoro [48,49,50,51]GraniteSHRIMP299 ± 4 MaAPost-collision
Inylchek [48,49,50,51]GraniteSHRIMP295.3 ± 4.4 MaAPost-collision
Maida’adir [48,49,50,51]GraniteSHRIMP288.6 ± 6.3 MaAPost-collision
Mangqisu [32,45,104]GranodioriteSHRIMP296.9 ± 5.4 MaISyn-collision-Post-collision
304.2 ± 11.6 Ma
LA-ICP-MS292 ± 2 Ma
297 ± 4 Ma
294 ± 3 Ma
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Xu, Y.; Yin, J.; Xiao, K.; Wang, C.; Xu, H.; Fang, J.; Fan, M. Geochronology and Petrogenesis of Ahetala Granodiorite in South Tianshan Orogenic Belt, Xinjiang: New Constraints on the Tectonic Evolution of the South Tianshan Ocean. Minerals 2022, 12, 1588. https://doi.org/10.3390/min12121588

AMA Style

Xu Y, Yin J, Xiao K, Wang C, Xu H, Fang J, Fan M. Geochronology and Petrogenesis of Ahetala Granodiorite in South Tianshan Orogenic Belt, Xinjiang: New Constraints on the Tectonic Evolution of the South Tianshan Ocean. Minerals. 2022; 12(12):1588. https://doi.org/10.3390/min12121588

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Xu, Yang, Jingwu Yin, Keyan Xiao, Chunlian Wang, Haiming Xu, Jingling Fang, and Mingjing Fan. 2022. "Geochronology and Petrogenesis of Ahetala Granodiorite in South Tianshan Orogenic Belt, Xinjiang: New Constraints on the Tectonic Evolution of the South Tianshan Ocean" Minerals 12, no. 12: 1588. https://doi.org/10.3390/min12121588

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