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Petrogenesis and Tectonic Setting of the Late Permian Granitoid in the East Kunlun Orogenic Belt, NW China: Constraints from Petrology, Geochemistry and Zircon U-Pb-Lu-Hf Isotopes

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17 February 2025

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18 February 2025

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Abstract

Permian magmatic rocks are extensively distributed in the East Kunlun Orogenic Belt (EKOB), yet controversies persist regarding the petrogenesis of granitoid and the tectonic evolution of the Buqingshan-A’nyemaqing Ocean (BAO), a Paleo-Tethys oceanic branch. This study addresses these debates through petrological analyses, whole-rock geochemistry, and zircon U-Pb-Lu-Hf isotopic investigations of newly identified granitoids in the EKOB. The monzogranite (MG) and quartz porphyry (QP) yield weighted mean ages of 254.7 ± 1.1 Ma and 254.3 ± 1.1 Ma, respectively. Geochemically, the MG shows metaluminous to weakly peraluminous low-K calc-alkaline I-type granites, characterized by high SiO2, low K2O, MgO, FeOT contents, and marked enrichment in light rare earth elements (LREEs), but depletion in Eu, Ba, Sr, P and Ti anomalies. In contrast, the QP exhibits peraluminous high-K calc-alkaline I-type affinities, displaying high SiO2 but low Na2O and P2O5 contents. It is enriched in LREEs and Rb but displays negative Nb, Sr, P, and Ti anomalies. Zircon εHf(t) values range from −1.6 to 2.6 (MG) and −4.4 to 1.5 (QP). We suggest the MG and QP are derived from the partial melting of the juvenile mafic lower crust, and the MG has undergone highly fractional crystallization. Synthesis of multiscale geological evidence allows us to delineate a five-stage tectonic evolution for the BAO in the EKOB: (1) oceanic basin initiation prior to ca. 345 Ma; (2) incipient northward subduction commencing at ca. 278 Ma; (3) slab roll-back stage (263–240 Ma); (4) syn-collisional compression (240–230 Ma); and (5) post-collisional extension (230–195 Ma).

Keywords: 
east Kunlun orogenic belt
;  
Permian granitoids
;  
Paleo-Tethys Ocean
;  
slab roll-back
;  
tectonic evolution
Subject: 
Environmental and Earth Sciences  -   Geochemistry and Petrology

1. Introduction

The east Kunlun orogenic belt (EKOB), a prototype subduction-accretion orogen, preserves multistage tectonomagmatic records, associated with Cambrian-Devonian Proto-Tethys and Carboniferous-Triassic Paleo-Tethys oceanic cycles [1,2,3,4,5,6,7,8,9,10]. While consensus exists on the Paleo-Tethyan oceanic opening prior to the Early Carboniferous [11,12,13] and initial northward subduction around 278 Ma [14]. Three principal controversies persist regarding its geodynamic evolution: (1) Majority view: Prolonged subduction (278–240 Ma) followed by collisional (240–230 Ma) and post-collisional phases (230–190 Ma) [3,5,7,8,15,16,17]. (2) Alternative model 1: Early collision initiation (pre-251 Ma) transitioning to post-collisional extension by 247Ma [18,19]. (3) Alternative model 2: Continuous subduction through the Late Triassic prior to terminal collision [20,21,22]. Petrogenetic investigations of EKOB granitoids document diverse magma provenance systems, including: (1) Subducted oceanic plate with overlying sedimentary [18,23], (2) lower crust [4,24], (3) juvenile mafic crust [25,26], (4) enriched mantle [27,28], (5) hybrid mantle-crust systems [29,30].
To address these debates, we conducted an integrated petrogenetic investigation of two Permian granitoids (monzogranite and quartz porphyry) from the Xingshugou area within EKOB. Through combined petrological analysis, whole-rock geochemistry, zircon U-Pb geochronology, and in-situ zircon Hf isotopic studies, this work aims to: (1) Constrain the magmatic sources and petrogenetic processes, (2) reconstruct the Paleo-Tethyan geodynamic evolution during critical Permian–Triassic transition.

2. Geological Setting and Samples

2.1. Regional Geology

The EKOB, situated along the northern margin of the Tibet Plateau in northwest China (Figure 1a), is bounded by four principal tectonic domains: the Qaidam Block to the north, the A’nyemaqen ophiolitic belt (AOB) to the south, the Altyn Tagh strike-slip fault system to the west, and the Wenquangou-Wahongshan fault to the east (Figure 1b). This orogen expends approximately 1,500 km in an E-W direction with a width of 50–200 km [2,22]. The Wutumeiren Township divides the EKOB into western and eastern sectors [31]. The EKOB is subdivided into three belts, which are the Caledonian back-arc basin of Northern East Kunlun Orogenic Belt (NKB), uplifted granitic basement of Central East Kunlun Orogenic Belt (CKB), and composite accretion of the Southern East Kunlun Orogenic Belt (SKB) from north to south, respectively (Figure1 b). The boundaries of them are northern east Kunlun fault (NEKF, also named as Nalinggele Fault in the western EKOB), central east Kunlun fault (CEKF), and southern east Kunlun fault (SEKF) from north to south, respectively (Figure1 b) [2,32]. The basement compositions exhibit spatial heterogeneity: (1) the NKB and CKB are Paleo-proterozoic Jinshuikou Group, (2) while the SKB is Meso- to Neo-proterozoic Wanbaogou basaltic oceanic plateau, which was produced by a mantle plume [32]. The EKOB records a protracted tectonic evolution involving (1) Cambrian–Devonian Proto-Tethys Ocean and Carboniferous–Triassic Paleo-Tethys Ocean [2,3,5,6,11,22,32,33]. Notably, Phanerozoic granitoids cover an area of approximately 47,500km2, with Permian–Triassic granitoids accounting for 23,000km2 (approximately 48% of total exposure) [31].

2.2. Geology of Study Area

The Xingshugou (XSG) study area is situated within the SKB, approximately 70 km south of Nuomuhong Township (Figure 1b). The region exposes a complex intrusive suite dominated by granodiorite, monzogranite, quartz porphyry and gabbro, with subordinate moyite. These plutons intrude the Lower Carboniferous Halaguole Formation, which comprises andesite sequences interbedded with carbonaceous slate (Figure 1c). Structural analysis reveals two predominant fault systems: (1) NW-SE trending and E-W oriented primary faults, and (2) secondary N-S trending fractures (Figure 1c). Notably, the magmatic complex is spatially associated with an epithermal low-sulfidation Au deposit (Figure 1c), suggesting potential genetic links between magmatism and hydrothermal mineralization.

2.3. Sample Descriptions

Two representative granitoid samples were systematically collected from XSG magmatic complex (Figure 1c).
(1) Monzogranite (MG), which was collected at 96°32′07″E, 35°51′07″N (Figure 1c), is flesh-pink and fine- to medium-grained granitic texture. It consists of plagioclase (~ 30 vol.%), potassium feldspar (~ 25 vol.%), quartz (~ 40 vol.%), biotite (< 5 vol.%), and accessory minerals including apatite, zircon, and opaque minerals (Figure 2a, b).
(2) Quartz porphyry (QP), which was collected at 96°32′17″E, 35°51′07″N (Figure 1c), is light gray and porphyritic texture. The phenocrysts are potassium feldspar (~ 10 vol.%), plagioclase (~ 10 vol.%), and quartz (~ 10 vol.%), the groundmass consists of plagioclase (~ 20 vol.%), K-feldspar (~ 20 vol.%), quartz (~ 20 vol.%), biotite (< 5 vol.%), and accessory minerals including apatite, zircon and opaque minerals (Figure 2c, d).

3. Analytical Methods

3.1. Zircon U-Pb Dating

Zircons were separated and selected for dating at Langfang Tuoxuan Rock and Mineral Testing Service Co., Ltd., Langfang, China, through the methods of heavy liquid and electromagnetic sorting combined with hand selection under the stereobinocular microscope. Then, an epoxy resin target was made for imaging in transmitted-reflected light and cathodoluminescence (CL). Zircon U-Pb isotope and trace elements were carried out at Yanduzhongshi Geological Analysis Laboratories Ltd., Langfang, China, by using an NWR193 laser-ablation microprobe (Elemental Scientific Lasers LLC), attached to an Analytikjena PlasmaQuant MS quadrupole ICP-MS. In this test, the diameter of the ablation spot is 32 μm. Detailed analytical methods were reported by [15], Data analytical ICP-MS-DATACAL program was used to calculate the isotopic data [35,36]. ISOPLOT toolkit for Microsoft Excel was used to calculate the weighted average ages and plot the concordia diagram [37].

3.2. Whole-Rock Major and Trace Elements Analyses

Major and trace elements of whole rock were conducted at the Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Natural Resources of China, Jilin University. Fresh samples were powdered to 200 mesh by an agate ring mill. Major elements were analyzed by X-ray fluorescence (XRF) spectrometer. For trace elements analyses, samples were digested by HF + HNO3 in Teflon bombs, then analyzed with an Agilent 7500a inductively coupled plasma mass spectrometry (ICP-MS). The precision for major and trace elements is better than 1% and 5%, respectively.

3.3. Zircon In Situ Lu-Hf Isotope Analyses

Zircon in situ Lu-Hf isotope analysis was carried out at Yanduzhongshi Geological Analysis Laboratories Ltd., Beijing, China. By using a NWR193 laser-ablation microprobe (Elemental Scientific Lasers LLC) attached to a Neptune multi-collector ICP-MS. The size of the laser beam spot is 38 μm in diameter. In situ Hf isotope analyzed position was the same spots as the U-Pb dating. Detailed analytical and data processing methods are presented by [15] and [38].

4. Results

4.1. Zircon U-Pb Dating

Zircon crystals from samples MG (18XSG1) and QP (18XSG2) exhibit transparent, light brown and euhedral morphologies (80–200 μm) with well-developed prismatic faces and oscillatory zoning in CL images (Figure 3c, f). High Th/U ratios (0.28–5.39) confirm their magmatic origin [39]. The zircon U-Pb isotopic data is presented in Table 1. Zircon U-Pb concordia 206Pb/238U ages of MG and QP yield 254.7 ± 0.57 Ma (MSWD = 0.26, n = 26) (Figure 3a) and 254.3 ± 0.57 Ma (MSWD = 0.035, n = 26) (Figure 3d), respectively. Zircon U-Pb weighted mean 206Pb/238U ages of MG and QP yield 254.7 ± 1.1 Ma (MSWD = 0.26, n = 26) (Figure 3b) and 254.3 ± 1.1 Ma (MSWD = 0.116, n = 26) (Figure 3e), respectively. Therefore, the crystallization timing of both intrusions is the Late Permian.

4.2. Major And Trace Elements

The data of major and trace elements is presented in Table 2.

4.2.1. Monzonitic Granite (MG)

The MG shows high SiO2 (73.00 - 79.56 wt%) contents, but low K2O (0.31–3.97 wt%), TiO2 (0.08–0.21 wt%), FeOT (FeOT = FeO + Fe2O3 * 0.8998, 1.01–1.76 wt%), MnO (0.02–0.06 wt%), P2O5 (0.01–0.05 wt%) and MgO (0.11–0.24 wt%) contents and Mg# (Mg# = 100 × molar MgO/(MgO + FeOT), 12.71–19.99) (Figure 4b, c). The value of A/CNK (A/CNK = molar Al2O3/(CaO + Na2O + K2O) ranges from 0.84 to 1.16 (Figure 4d). All of the above suggested the MG was low-K subalkaline metaluminous rock. It is enriched in light rare earth elements (LREEs) with (La/Yb)N ((La/Yb)N = (LaSample/LaCI)/(YbSample/YbCI)) of 7.07–49.23 (Figure 5a) and large ion lithophile elements (LILEs, such as Rb and Th) (Figure 5b). They also show significant negative Eu anomalies (Eu/Eu* = 0.28–0.32, one outlier at 1.23; Eu/Eu* = (EuSample/EuCI)/{[(SmSample/SmCI) * (GdSample/GdCI) ]^ (1/2)}) (Figure 5a), and depleted in Ba, K, Sr, P, Ti (Figure 5b).
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Figure 4. (a) Diagrams of QAP, after [40]; (b) Na2O + K2O (wt%) vs. SiO2 (wt%), after [41]; (c) K2O vs. SiO2, after [42]; (d) A/CNK vs. SiO2.
Figure 4. (a) Diagrams of QAP, after [40]; (b) Na2O + K2O (wt%) vs. SiO2 (wt%), after [41]; (c) K2O vs. SiO2, after [42]; (d) A/CNK vs. SiO2.
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Figure 5. Chondrite-normalized REEs and primitive mantle-normalized trace elements patterns. (a, b) Monzogranite (18XSG1); (c, d) quartz porphyry (18XSG2). Normalization values are from [43].
Figure 5. Chondrite-normalized REEs and primitive mantle-normalized trace elements patterns. (a, b) Monzogranite (18XSG1); (c, d) quartz porphyry (18XSG2). Normalization values are from [43].
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Table 2. Major(wt%) and trace elements (ppm) data for Xingshugou monzogranite (18XSG1) and quartz porphyry (18XSG2).
Table 2. Major(wt%) and trace elements (ppm) data for Xingshugou monzogranite (18XSG1) and quartz porphyry (18XSG2).
Rock type monzogranite quartz porphyry
Sample No. 18XSG1-1 18XSG1-2 18XSG1-3 18XSG1-4 18XSG1-5 18XSG2-1 18XSG2-2 18XSG2-3 18XSG2-4 18XSG2-5
Major elements (wt%)
SiO2 78.21 73.00 78.29 79.56 79.01 74.32 65.86 66.68 68.91 72.31
TiO2 0.10 0.21 0.10 0.08 0.10 0.39 0.81 0.58 0.46 0.45
Al2O3 11.65 14.46 12.17 10.49 11.49 11.22 20.20 14.76 12.92 12.95
Fe2O3 0.43 1.22 0.40 0.29 0.77 4.00 4.44 2.17 1.67 3.28
FeO 0.81 0.64 0.79 0.73 0.79 1.59 1.45 2.94 3.27 1.85
MnO 0.03 0.06 0.02 0.03 0.03 0.16 0.20 0.21 0.28 0.16
MgO 0.12 0.24 0.11 0.11 0.12 0.78 1.01 1.51 1.69 0.87
CaO 1.45 0.76 0.27 2.05 0.34 1.45 1.61 2.02 3.44 1.38
Na2O 5.77 4.10 6.24 5.11 5.67 0.29 0.12 0.17 0.16 0.22
K2O 0.36 3.97 0.50 0.31 0.61 4.40 2.66 7.56 5.77 5.21
P2O5 0.02 0.05 0.02 0.02 0.01 0.12 0.20 0.16 0.15 0.15
LOI 0.90 1.25 0.70 1.20 0.85 1.20 1.00 1.10 0.80 1.10
Total 99.86 99.96 99.61 99.99 99.79 99.92 99.57 99.86 99.51 99.90
FeOT 1.21 1.76 1.16 1.01 1.50 5.25 5.53 4.95 4.83 4.85
Mg# 15.29 19.99 14.69 16.79 12.71 21.25 25.03 35.66 38.92 24.64
A/CNK 0.93 1.16 1.08 0.84 1.08 1.42 3.36 1.21 1.01 1.52
A/NK 1.18 1.31 1.13 1.20 1.15 2.14 6.57 1.74 1.98 2.15
Trace elements (ppm)
Li 0.25 4.01 2.19 4.02 2.66 21.81 48.51 22.86 14.37 20.46
Be 1.96 1.18 1.58 1.32 1.06 0.87 1.54 0.86 0.89 0.93
B 11.49 18.19 8.33 9.35 6.57 11.76 19.34 14.52 8.98 12.21
Sc 1.09 1.11 2.14 1.81 1.67 7.73 10.27 9.08 7.58 7.56
Ti 537.80 1298.00 564.60 421.40 472.20 2275.00 3990.00 3129.00 2380.00 2497.00
V 3.22 16.18 2.51 3.06 3.65 59.89 92.46 74.28 58.62 64.67
Cr 5.27 6.65 4.08 5.54 3.91 7.70 4.71 4.95 6.34 5.85
Mn 154.80 370.20 103.60 139.40 164.50 1171.00 1327.00 1396.00 1823.00 1075.00
Co 2.86 4.10 3.16 2.25 3.54 10.41 10.14 7.59 87.14 7.46
Ni 2.50 3.13 1.70 2.22 1.32 4.01 3.39 2.77 4.98 3.11
Cu 4.01 36.72 4.03 4.08 3.32 152.00 93.74 516.90 280.10 273.20
Zn 9.70 63.54 7.41 9.01 8.17 163.90 184.50 157.10 112.20 147.50
Ga 7.47 11.05 10.51 10.70 8.87 11.16 17.50 12.54 10.50 11.73
As 7.46 9.82 2.73 3.45 2.06 18.23 13.55 6.61 5.41 8.36
Se 1.14 1.08 1.25 1.22 1.06 1.70 1.76 1.42 1.47 1.48
Rb 17.68 119.50 22.19 15.21 26.93 154.50 127.80 254.90 168.00 182.70
Sr 56.41 309.10 63.22 81.85 52.61 55.72 32.52 74.41 103.40 56.50
Y 9.83 7.67 13.03 14.79 11.42 12.58 19.36 15.37 14.42 13.64
Zr 63.48 165.60 62.83 59.17 55.76 109.10 194.90 149.40 113.30 120.00
Nb 11.56 4.74 12.39 11.46 13.83 4.29 6.95 5.30 4.06 5.01
Mo 5.49 1.50 0.50 0.84 3.10 1.42 5.32 0.49 1.24 0.65
Ag 0.09 0.17 0.08 0.09 0.06 1.16 0.83 0.98 1.12 0.46
Cd 0.44 1.14 0.40 0.39 0.35 0.77 1.43 1.01 0.77 0.90
Sn 2.33 1.09 1.10 1.25 1.03 1.40 1.60 1.19 1.71 1.70
Sb 132.50 125.60 32.66 60.10 29.31 11.86 35.39 26.90 44.45 638.60
Cs 0.55 2.22 0.57 0.73 0.74 2.23 4.00 3.56 1.85 2.90
Ba 27.92 1670.00 61.86 49.33 70.10 1186.00 154.40 1466.00 1400.00 1609.00
La 21.51 59.99 28.61 35.10 17.11 23.35 36.78 14.84 37.11 17.02
Ce 41.25 101.30 51.45 63.35 32.10 41.48 65.29 27.78 61.85 32.34
Pr 3.95 10.40 5.14 6.08 3.25 4.42 7.01 2.98 6.43 3.52
Nd 12.24 31.03 15.73 17.99 10.02 15.69 23.66 10.91 22.22 12.53
Sm 2.04 3.52 2.55 2.99 1.91 2.73 3.73 2.09 3.47 2.33
Eu 0.19 1.23 0.25 0.26 0.19 0.80 0.79 0.71 0.94 0.77
Gd 1.80 2.70 2.21 2.70 1.88 2.58 3.64 2.35 3.18 2.50
Tb 0.27 0.30 0.33 0.39 0.31 0.37 0.51 0.39 0.45 0.39
Dy 1.64 1.48 2.06 2.20 1.90 2.20 3.25 2.52 2.65 2.36
Ho 0.35 0.30 0.46 0.50 0.42 0.48 0.73 0.57 0.54 0.50
Er 1.11 0.89 1.44 1.57 1.33 1.46 2.31 1.73 1.56 1.50
Tm 0.18 0.14 0.25 0.26 0.23 0.24 0.36 0.27 0.25 0.23
Yb 1.32 0.98 1.75 1.85 1.59 1.66 2.43 1.82 1.57 1.51
Lu 0.21 0.16 0.29 0.31 0.27 0.28 0.39 0.29 0.25 0.23
Hf 3.94 6.29 3.87 3.67 3.48 4.30 7.83 6.02 4.54 4.82
Ta 1.27 0.37 1.17 1.22 1.05 0.32 0.54 0.42 0.33 0.40
W 31.53 29.66 28.61 30.77 22.49 21.76 15.94 18.53 15.19 93.29
Tl 0.20 1.12 0.22 0.19 0.23 1.45 1.01 2.35 1.71 1.68
Pb 5.03 23.05 2.62 5.55 3.04 277.10 59.12 17.47 37.36 15.90
Bi 0.20 0.52 0.15 0.20 0.10 0.14 0.09 0.07 0.12 0.08
Th 23.37 16.39 34.20 28.95 27.73 8.32 12.60 9.97 7.68 8.21
U 1.98 4.34 2.07 3.76 2.25 1.78 2.76 2.37 1.57 1.61
ΣREEs 88.06 214.41 112.52 135.54 72.50 97.74 150.88 69.27 142.46 77.72
ΣLREEs 81.17 207.47 103.73 125.77 64.58 88.47 137.26 59.31 132.02 68.51
ΣHREEs 6.89 6.94 8.79 9.77 7.92 9.27 13.62 9.96 10.44 9.22
(La/Yb)N 11.71 43.94 11.71 13.59 7.70 10.08 10.87 5.85 16.94 8.11
Eu/Eu* 0.30 1.23 0.32 0.28 0.31 0.92 0.66 0.99 0.87 0.98
TZr(℃) 647.73 761.73 666.20 630.77 658.52 753.40 889.96 748.40 698.63 767.19
* LOI=loss on ignition; FeOT = FeO + Fe2O3 * 0.8998; Mg# = 100 × molar MgO/(MgO + FeOT); A/CNK = molar Al2O3/(CaO + Na2O + K2O); A/NK = molar Al2O3/(Na2O + K2O); ( La/Yb)N = (LaSample/LaCI)/(YbSample/YbCI); Eu/Eu* = (EuSample/EuCI)/{[(SmSample/SmCI) * (GdSample/GdCI) ]^ (1/2)}; TZr(℃)(zirconium saturation temperature) is calculated by [44]. Normalization values are from [43].

4.2.2. Quartz Porphyry (QP)

The QP shows high SiO2 (65.86–74.32 wt%) and K2O (2.66–7.56 wt%) contents, but low Na2O (0.12–0.29 wt%), FeOT (4.82–5.53 wt%), MnO (0.16–0.28 wt%), TiO2 (0.39–0.81 wt%) and P2O5 (0.12–0.20 wt%) contents and Mg# (21.25–38.92). The value of A/CNK ranges from 1.01 to 3.36 (Figure 4d). All of the above suggested the QP was high-K subalkaline peraluminous rock. It is enriched in LREEs with (La/Yb)N of 5.85–16.94 (Figure 5c) and LILEs (Figure 5d). It also shows weakly negative Eu anomalies (0.90–0.970) (Figure 5c) and depletes in Nb, Sr, P. Ti (Figure 5d).

4.3. In Situ Zircon Hf Isotope

The data is presented in Table 3. All the 176Lu/177Hf ratios were less than 0.002, which indicated that the decay of 177Hf by 176Lu was rare, so the measured 176Hf/177Hf ratios likely represent the initial composition of the magmatic system [45,46]. The initial 176Hf/177Hf ratios of MG (18XSG1) and QP (18XSG2), which were calculated back to 254 Ma, ranged from 0.282576 to 0.282693 and 0.282495 to 0.282665, respectively. Additionally, the value of εHf(t) ranges from −1.6 to 2.6 and −4.4 to 1.5, respectively (Figure 6). The two-stage model age (TDM2) yielded from 1003 to 1301Ma and 947 to 1161Ma, respectively.

5. Discussion

5.1. Petrogenesis of the XSG Granitoids

I-, S-, M- and A-type granite have been presented according to the different source and geochemical characteristics [50,51]. While I- S-, and A- granites have been documented in the EKOB [3,18,19,26,52], our integrated analyses constrain the petrogenetic affinity of the XSG intrusions.
The absence of alkaline dark minerals in both MG and QP, coupled with depletion in HFSEs (Figure 5b, d), low zircon saturation temperature (TZr = 694–800 ℃ for MG, 752–880 ℃ for QP) [44,53], as well as subdued value of 10000Ga/Al ratios (1.21–1.93) and Zr + Nb + Ce + Y contents (113.11–286.50 ppm) below typical A-type granite (Figure 7e, f, g, h), collectively preclude an A-type affinity [50]. Furthermore, the scarcity of voluminous coeval mafic intrusions in the study area [31], absence of aluminum minerals (e.g., muscovite, garnet and cordierite) and negative relationship between P2O5 and SiO2 in samples (Figure 7d) confirm an I-type granite classification [51,54,55].
The MG shows high SiO2 contents (73.00–79.56 wt%) but low TiO2 (0.08–0.21 wt%), MgO (0.11–0.24 wt%), FeOT (1.01–1.76 wt%), P2O5 (0.01–0.05 wt%) and MnO (0.02–0.06 wt%) contents (Figure 7a, b, c), as well as depletes in Eu (Eu/Eu* = 0.28–0.32, one outlier at 1.23), Ba, and Sr (Figure 5a, b). The MG shows higher value of FeOT/MgO ratios (7.20–12.36) and (K2O + Na2O)/CaO ratios (2.64–18.50) than QP (2.83–6.67, 1.72–3.94, respectively), and it plots into FG (fractionated granites) area in the diagrams of FeOT/MgO vs. Zr + Nb + Ce + Y and (K2O + Na2O)/CaO vs. Zr + Nb + Ce + Y (Figure 7e, f). All of the above indicate the MG underwent higher degree fractional crystallization than QP. The samples of MG show significantly fractional crystallization of K-feldspar and plagioclase on the Ba/Sr–Sr and Ba–Sr diagrams (Figure 8a, b) coupled with the highly depleted Eu for MG (Figure 5a). The Rb/Sr ratios of MG are positively correlated with Sr (Figure 8c), which implies that the fractional crystallization of biotite. The (La/Yb)N–La diagram shows significant fractional crystallization of titanite and apatite for MG (Figure 8d). These features collectively support the classification of the MG as metaluminous to weakly peraluminous low K calc-alkaline I-type granite that underwent extensive fractional crystallization (Figure 4b,c, d, 7, 8), contrasting with the less differentiated high K calc-alkaline I-type QP (Figure 4b,c,d, 7, 8) [51,56].
I-type granite genesis typically involves three principal mechanisms: (1) mixing of crustal and mantle-derived melts [57,58], (2) Assimilation fractional crystallization (AFC) of mantle-derived basaltic magma during ascent through continental crust [49,59], (3) partial melting of the lower crust [60,61,62,63].
Absence of mafic microgranular enclaves (MMEs) in MG and QP (Figure 2) and restricted zircon εHf(t) value (−1.6 to 2.6 for MG, −4.4 to 1.5 for QP) (Figure 6), precluded the magma mixing as a viable mechanism, because such a process would produce scattered isotopic signatures (Δε > 10 units) [61,64].
The high SiO2 contents (exceeding 55 wt%) and low concentrations of compatible elements contents, such as Cr (3.91–6.65 ppm for MG, 4.71–7.70 ppm for QP), Ni (1.32–3.13 ppm for MG, 2.77–4.98 ppm for QP), and Co (2.25–4.01ppm for MG, 7.46–87.14 ppm for QP), suggested they couldn’t generate from the mantle [65]. According to the relative incompatibility of Nb, Th, Ta and U (DNb ≈ DTh < DTa ≈ DU), Nb* (= [Nb/Th]Sample/[Nb/Th]PM) and Ta* (= [Ta/U]Sample/[Ta/U]PM) ratios are normally inherited from the source region and remain constant during the subsequent differentiation [66]. The lower Nb* and Ta* ratios compared to those of the Bulk Continental Crust (BCC) (Figure 9a) further suggest that they were not derived from the mantle. To produce one piece of granites needs more than three times of basaltic magma [49], but we haven’t found so much coeval mafic magma in EKOB [25,67,68]. Consequently, we have ruled out the mechanism involving the fractionation of mantle-derived magma.
The Nb/Ta ratios of the MG and QP samples range from 9.10 to 13.23 and 12.23 to 13.39, respectively (Figure 9b). These ratios cluster near BCC values (11.43), deviating markedly from primitive mantle (PM) values (17.5), indicating a crustal affinity (Figure 9b) [43,72,73]. The MG exhibits high (Na2O + K2O)/(Fe2O3 + MgO + TiO2) and Al2O3/(Fe2O3 + MgO + TiO2) ratios, whereas the QP shows low ratios of these parameters (Figure 9c, d). We believe that the MG also should be plotted into the amphibolites area (Figure 9c, d), as it has undergone some degree of fractional crystallization, leading to a decrease in Fe, Mg, and Ti contents. Therefore, we propose that the MG and QP are derived from mafic lower crust [69,70]. The εHf(t) values are mostly positive (Figure 6), which indicating a mantle component. The two-stage Hf model ages of the MG and QP range from 1.0 to 1.3 Ga and 0.9 to 1.1 Ga, respectively. The MG and QP display higher Ba/Th ratios but lower La/Sm ratios (Figure 9e), which implied the source was modified by fluids released from subducted slab. The intense interaction of mantle-crustal magma has been enhanced, as evidenced by the widespread coeval MMEs during Late Permian-Middle Triassic [18,27,33].
In summary, we propose that the MG and QP originated from the partial melting of the metasomatized Meso- to Neo-Proterozoic juvenile lower crust. This process was triggered by the underplating of mantle-derived mafic magma at the boundary between the lithospheric mantle and the lower crust. Additionally, fractional crystallization occurred in the MG during magmatic evolution.

5.2. Geochronology and Tectonic Implications

Zircon U-Pb geochronology constraints the crystallization ages of the MG and QP to 254.7 ± 1.1 Ma (MSWD = 0.26, Figure 3b) and 254.3 ± 1.1 Ma (MSWD = 0.116, Figure 3e), respectively, with magmatic origins confirmed by well-developed oscillatory zoning textures (Figure 3c, f) and elevated Th/U ratios ( 0.28 to 5.39, Table 1) [39]. These Late Permian granitoids record critical magmatic activity during the Paleo-Tethyan evolution of the EKOB, displaying diagnostic arc-related geochemical signatures including LILEs enrichment, HFSEs depletion (Figure 5), and systematic clustering within the volcanic arc granite (VAG) field on the tectonic discrimination diagrams (e.g., Nb vs. Y and Ta vs. Yb, Figure 10) [74]. Their coherent spatial-temporal distribution and subduction-related geochemical fingerprints collectively affirm generation in an active continental margin setting associated with northward Paleo-Tethyan oceanic slab subduction.
The tectonic evolution of the Buqingshan-A’nyemaqing Ocean (BAO), a Paleo-Tethys branch, has been progressively constrained though decades of multidisciplinary research. Current consensus recognizes oceanic opening prior to the Early Carboniferous, evidenced by ophiolitic suites including Haerguole gabbro (ca. 332 Ma [13]) and Dur’ngoi basalts (ca. 308 Ma [11]; ca. 345 Ma [12]). Northeastward subduction initiation at ca. 278 Ma is well-documented by the Xiaomiao mafic dike swarm [14], yet persistent controversies surround the timing and mechanisms of subduction-to-collision transition. Three principal models have emerged: (1) A dominant view advocates continuous subduction until ca. 240 Ma followed by Lake Triassic collision (240 Ma to 225 Ma) and post-collisional stage [2,17,32,75]. (2) Alternative interpretations propose prolonged subduction through the Late Triassic with Jurassic collision onset [20,21,22,76]. (3) Contrasting models posit pre-Late Permian collision [18,19,23,77]. These discrepancies stem from two key factors: methodological limitations in tectonic discrimination using granitoid geochemistry alone [26,31,67,78,79,80], compounded by evolving interpretations of expanding geochemical and geological datasets [8,9,10,30,81,82,83]. To reconcile these conflicts, we propose an integrated geodynamic model synthesizing stratigraphic records, petrogenetic constraints, metallogenic patterns, and regional tectonics, augmented by recent high-resolution geochronological and isotopic datasets.
The first stage (345–278 Ma): The tectonic evolution of the BAO initiated with oceanic opening prior to ca. 345 Ma, as evidenced by Haerguole and Dur’ngoi ophiolites [12], while Carboniferous shallow-marine sequences dominated by volcanic-carbonate strata reflect passive continental margin [84] without arc-magmatism (Figure 11).
The second stage (278–240 Ma): Northward subduction commenced by ca. 278 Ma, marked by the Xiaomiao mafic dike swarm [14] and corroborated by the angular unconformity between the Upper Permian Gequ Formation and underlying units [84]. The Upper Permian Gequ Formation, Lower Triassic Hongshuichuan Formation, and Middle Triassic Naocangjiangou Formation record progressive subduction [85], transitioning from low-angle slab (278–263 Ma) with limited magmatism to intense mantle-crust interaction during 263-240 Ma (Figure 11). This magmatic flare-up, characterized by diverse magmatic rocks such as I-/A2-type granite, adakitic, and mafic rocks (Yingzhuagou olivine gabbro-norite: 263 ± 4Ma [86]; Zhongzaohuo pyroxenite: 261.2 ± 3.0 Ma [87]; Bairiqiligou mafic dike swarms: 251 ± 2 Ma [88]; Kengdenongshe granite porphyry: 257.0 ± 2.0 Ma [52]) coincided with the asthenospheric upwelling indued by the slab rollback. Mantle sources varied from enriched [68,87] to hybrid depleted-enriched compositions [86], while crustal melts derived from lower crust [89], juvenile mafic lower crust [90], and subducted slab and overlying sediments [18]. Concurrent Cu-Ni mineralized mafic-ultramafic complexes (263–252 Ma) [86,87,88] further attest to this extensional regime, where rollback-driven lithospheric thinning facilitated large-scale magma generation and crustal recycling through mantle-crust hybridization (Figure 11).
The Third stage (240–230 Ma): The incipient collision phase is evidenced by a micro-angular unconformity between middle Triassic Xilikete Formation and Naocangjiangou Formation, signaling initial collision between Bayanhar block and EKOB [84]. Although slab break-off has been invoked by some studies in the EKOB [91], the conspicuous magmatic quiescence during this interval (Figure 11) provides stronger evidence for syn-collisional compressional tectonics, as evidenced by localized Xilikete Formation deposition in uplifted terranes [84].
The fourth stage (230–195 Ma): The pronounced angular unconformity between the Upper Triassic Babaoshan Formation and underlying strata reflects large-scale collision during this period [84]. Geophysical constraints reveal lower crustal thinning [92,93], attributed to eclogitization-drived lithospheric delamination that triggered asthenospheric upwelling and renewed magmatic flare-up (Figure 11). This stage generated voluminous A2-type and adakitic magma [19,26,75,79,80,94,95,96], their emplacement facilitated by gravitational instability of densified lithospheric roots.
Synthesizing multidisciplinary evidence, we reconstruct the BAO evolutionary sequence: (1) The BAO has opened before early Carboniferous (ca. 345 Ma); (2) the oceanic slab has initiated to subduct before 278 Ma; (3) then it evolved into the low-angle subduction during 278–263 Ma and high-angle subduction caused by slab roll-back during 263–240 Ma; (4) the EKOB and Bayanhar has collided together during 240–230 Ma; (5) finally, the EKOB has evolved into the post-collisional setting during 230–195 Ma.

6. Conclusions

(1) Zircon U-Pb geochronology constrains the emplacement of monzogranite and quartz porphyry to ca. 254 Ma, classifying as low-K calc-alkaline I-type granites which underwent highly fractional crystallization, and high-K calc-alkaline I-type granites, respectively.
(2) Petrogenetic modeling indicates these granitoids originated through partial melting of juvenile mafic lower crust, a process initiated by mantle-derived magma underplating.
(3) The integrated geodynamic evolution of Buqingshan-A’nyemaqing ocean (a branch of Paleo-Tethys Ocean) has been established as follows: (1) oceanic spreading initiates before ca. 345 Ma, (2) low-angle subduction stage ranges from ca. 278 to 263 Ma, (3) slab roll-back stage ranges from ca. 263 to 240 Ma, (4) syn-collisional stage ranges from ca. 240 to 230 Ma, (5) post-collisional stage ranges from 230 to 195 Ma.

Supplementary Materials

The following supporting information can be downloaded at the website of this paper posted on Preprints.org. Table S1: Summary of the published zircon Hf isotopic data of granites in the EKOB. Table S2: Summary of ages of the Permian-Triassic igneous rocks in the eastern of the East Kunlun Orogenic Belt.

Author Contributions

Conceptualization, Chao Hui and Fengyue Sun; Formal analysis, Tao Yu; Funding acquisition, Tao Wang, Yanqian Yang and Yun Chai; Investigation, Yanqian Yang, Bile Li, Xingsen Chen, Chengxian Liu and Xinran Zhu; Methodology, Chao Hui; Project administration, Desheng Dou; Software, Bakht Shahzas; Supervision, Fengyue Sun; Validation, Jiaming Yan; Visualization, Yajing Zhang, Yuxiang Wang, Zhengsong Wang, Hanran Li and Renyi Song; Writing – original draft, Chao Hui; Writing – review & editing, Fengyue Sun. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by Qinghai Geological Survey Project and Technology Innovation Center for Exploration and Exploitation of Strategic Mineral Resources in Plateau Desert Region, Ministry of Natural Resources Project, grant number 2021074005ky005, 2023085029ky004, No. 2022012005ky005, No. 2023085026ky001.

Data Availability Statement

The original contributions presented in the study are included in the
article/Supplementary Material.

Acknowledgments

We would like to thank Electron Microscope Center, Jilin University, the Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Natural Resources of China, Jilin University, Langfang Tuoxuan Rock and Mineral Testing Service Co., Ltd., for helping in the analyses. We thank all the editors and anonymous reviewers for their constructive comments to improve this manuscript.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
EKOB East Kunlun Orogenic Belt
BAO Buqingshan-A’nyemaqing Ocean
AOB A’nyemaqen ophiolitic belt
NKB Caledonian back-arc basin of Northern East Kunlun Orogenic Belt
CKB uplifted granitic basement of Central East Kunlun Orogenic Belt
SKB composite accretion of the Southern East Kunlun Orogenic Belt
NEKF northern east Kunlun fault
CEKF central east Kunlun fault
SEKF southern east Kunlun fault
ATF Altyn Tagh strike-slip fault
MMF Wenquangou-Wahongshan fault
XSG Xingshugou
MG Monzogranite
Qtz quartz
Pl plagioclase
Kfs potassium feldspar
QP Quartz porphyry
CL cathodoluminescence
LREEs light rare earth elements
TDM2 two-stage model age

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Figure 1. (a) Simplified tectonic map of China (after [34]), (b) Outline of tectonic map of the EKOB showing the three major faults and tectonic belts (modified from [2,32]), (c) Geological map of Xingshugou area and sample location. ATF: Altyn Tagh strike-slip fault, WWF: Wenquangou-Wahongshan fault, NEKF: northern east Kunlun fault, CEKF: central east Kunlun fault, SEKF: southern east Kunlun fault, NKB: Caledonian back-arc basin Belt of Northern East Kunlun, CKB: uplifted granitic basement of Central East Kunlun, SKB: composite accretion belt of the Southern East Kunlun, AOB: A’nyemaqen ophiolitic belt.
Figure 1. (a) Simplified tectonic map of China (after [34]), (b) Outline of tectonic map of the EKOB showing the three major faults and tectonic belts (modified from [2,32]), (c) Geological map of Xingshugou area and sample location. ATF: Altyn Tagh strike-slip fault, WWF: Wenquangou-Wahongshan fault, NEKF: northern east Kunlun fault, CEKF: central east Kunlun fault, SEKF: southern east Kunlun fault, NKB: Caledonian back-arc basin Belt of Northern East Kunlun, CKB: uplifted granitic basement of Central East Kunlun, SKB: composite accretion belt of the Southern East Kunlun, AOB: A’nyemaqen ophiolitic belt.
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Figure 2. The field photographs and photomicrographs of monzogranite (a, b) and quartz porphyry (c, d). Qtz: quartz, Pl: plagioclase, Kfs: K-feldspar.
Figure 2. The field photographs and photomicrographs of monzogranite (a, b) and quartz porphyry (c, d). Qtz: quartz, Pl: plagioclase, Kfs: K-feldspar.
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Figure 3. Zircon U-Pb concordia diagrams, weighted mean age diagrams and representative zircon CL images for samples. (a–c) Monzogranite (18XSG1); (d–f) quartz porphyry (18XSG2).
Figure 3. Zircon U-Pb concordia diagrams, weighted mean age diagrams and representative zircon CL images for samples. (a–c) Monzogranite (18XSG1); (d–f) quartz porphyry (18XSG2).
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Figure 6. Diagrams of εHf (t) vs. U-Pb age. The published zircon Hf isotopic data of granites in the EKOB is present in Supplementary Table S1.
Figure 6. Diagrams of εHf (t) vs. U-Pb age. The published zircon Hf isotopic data of granites in the EKOB is present in Supplementary Table S1.
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Figure 7. Diagrams of (a) TiO2 (wt%) vs. SiO2 (wt%); (b) MgO (wt%) vs. SiO2 (wt%); (c) FeOT (wt%) vs. SiO2 (wt%); (d) P2O5 (wt%) vs. SiO2 (wt%); (e) FeOT/MgO vs. Zr + Nb + Ce + Y (ppm); (f) (K2O + Na2O)/CaO vs. Zr + Nb + Ce + Y (ppm); (g) Nb (ppm) vs. 10000Ga/Al; (h) Ce (ppm) vs. 10000Ga/Al. e–h are from [50]. FT = fractionated granites, OGT = unfractionated granites.
Figure 7. Diagrams of (a) TiO2 (wt%) vs. SiO2 (wt%); (b) MgO (wt%) vs. SiO2 (wt%); (c) FeOT (wt%) vs. SiO2 (wt%); (d) P2O5 (wt%) vs. SiO2 (wt%); (e) FeOT/MgO vs. Zr + Nb + Ce + Y (ppm); (f) (K2O + Na2O)/CaO vs. Zr + Nb + Ce + Y (ppm); (g) Nb (ppm) vs. 10000Ga/Al; (h) Ce (ppm) vs. 10000Ga/Al. e–h are from [50]. FT = fractionated granites, OGT = unfractionated granites.
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Figure 8. Diagrams of (a) Ba/Sr vs. Sr (ppm); (b) Ba (ppm) vs. Sr (ppm); (c) Rb/Sr vs. Sr (ppm); (d) (La/Yb)N vs. La (ppm). Pl = plagioclase; Kfs = K-feldspar; Bi = biotite; Amp = amphibole; Ms = muscovite; Cpx = clinopyroxene; Opx = orthopyroxene; Aln = allanite; Mon = monazite; Ap = apatite; Tit = titanite; Zr = zircon.
Figure 8. Diagrams of (a) Ba/Sr vs. Sr (ppm); (b) Ba (ppm) vs. Sr (ppm); (c) Rb/Sr vs. Sr (ppm); (d) (La/Yb)N vs. La (ppm). Pl = plagioclase; Kfs = K-feldspar; Bi = biotite; Amp = amphibole; Ms = muscovite; Cpx = clinopyroxene; Opx = orthopyroxene; Aln = allanite; Mon = monazite; Ap = apatite; Tit = titanite; Zr = zircon.
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Figure 9. Diagrams of magmatic source discrimination. (a) Nb* vs. Ta* [66]; (b)SiO2 vs. Nb/Ta; (c) Al2O3/(Fe2O3 + MgO + TiO2) vs. Al2O3 + Fe2O3 + MgO + TiO2 (wt%) [69,70]; (d) (Na2O + K2O)/(Fe2O3 + MgO + TiO2) vs. Na2O + K2O + Fe2O3 + MgO + TiO2 (wt%) [69,70]; (e) La/Sm vs. Ba/Th [71]. Data of primitive mantle and average oceanic basalts (OIB, E-MORB, N-MORB) are from [43], crust composition (BCC, LCC, UCC) are from [72]. Nb* (= [Nb/Th]Sample/[Nb/Th]PM) and Ta* (= [Ta/U]Sample/[Ta/U]PM).
Figure 9. Diagrams of magmatic source discrimination. (a) Nb* vs. Ta* [66]; (b)SiO2 vs. Nb/Ta; (c) Al2O3/(Fe2O3 + MgO + TiO2) vs. Al2O3 + Fe2O3 + MgO + TiO2 (wt%) [69,70]; (d) (Na2O + K2O)/(Fe2O3 + MgO + TiO2) vs. Na2O + K2O + Fe2O3 + MgO + TiO2 (wt%) [69,70]; (e) La/Sm vs. Ba/Th [71]. Data of primitive mantle and average oceanic basalts (OIB, E-MORB, N-MORB) are from [43], crust composition (BCC, LCC, UCC) are from [72]. Nb* (= [Nb/Th]Sample/[Nb/Th]PM) and Ta* (= [Ta/U]Sample/[Ta/U]PM).
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Figure 10. Diagrams of granite tectonic discrimination [74].
Figure 10. Diagrams of granite tectonic discrimination [74].
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Figure 11. Histograms of zircon U-Pb ages of the Carboniferous-Triassic magmatic rocks in the EKOB. Published ages are presented in Supplementary Table S2.
Figure 11. Histograms of zircon U-Pb ages of the Carboniferous-Triassic magmatic rocks in the EKOB. Published ages are presented in Supplementary Table S2.
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Table 1. LA-ICP-MS U-Pb isotopic data for zircons for Xingshugou monzogranite (18XSG1) and quartz porphyry (18XSG2).
Table 1. LA-ICP-MS U-Pb isotopic data for zircons for Xingshugou monzogranite (18XSG1) and quartz porphyry (18XSG2).
Sample Name Content (ppm) 　 Isotopic ratios Isotopic ages (Ma)
U Th Pb Th/U 207Pb/206Pb 1σ 207Pb/235U 1σ 206Pb/238U 1σ 207Pb/206Pb 1σ 207Pb/235U 1σ 206Pb/238U 1σ
18XSG1-monzogranite, weighted mean age: 254.7 ± 1.1 Ma, MSWD = 0.26
18XSG11-1 136 169 8 1.25 0.05140 0.00192 0.27890 0.01040 0.03956 0.00049 258.71648 85.75895 249.78293 8.25463 250.10093 3.06022
18XSG11-2 272 309 15 1.14 0.05199 0.00109 0.28480 0.00581 0.03989 0.00033 284.81419 47.85650 254.45604 4.59370 252.12208 2.01725
18XSG11-3 250 302 14 1.21 0.05211 0.00190 0.28639 0.01016 0.04016 0.00055 290.31512 83.26791 255.71640 8.01661 253.84337 3.42558
18XSG11-4 245 298 14 1.22 0.05164 0.00128 0.28393 0.00657 0.04020 0.00040 269.32848 56.90187 253.77020 5.19438 254.04809 2.50053
18XSG11-5 433 478 24 1.10 0.05084 0.00117 0.28095 0.00696 0.04021 0.00053 233.45662 53.10910 251.41094 5.51512 254.15459 3.29228
18XSG11-6 377 377 20 1.00 0.05193 0.00107 0.28701 0.00624 0.04021 0.00043 282.41105 47.03537 256.20248 4.92545 254.15973 2.65871
18XSG11-7 216 222 12 1.03 0.05150 0.00165 0.28270 0.00820 0.04023 0.00049 263.41689 73.36666 252.79409 6.48970 254.27459 3.05476
18XSG11-8 363 429 20 1.18 0.05153 0.00112 0.28503 0.00600 0.04027 0.00039 264.59209 49.92739 254.63626 4.73928 254.53441 2.39550
18XSG11-9 311 381 18 1.23 0.05163 0.00115 0.28569 0.00593 0.04028 0.00034 269.21598 51.21303 255.16324 4.68715 254.56553 2.09772
18XSG11-10 351 363 18 1.03 0.05048 0.00180 0.28014 0.01045 0.04028 0.00058 217.07634 82.60975 250.76554 8.28831 254.58830 3.57059
18XSG11-11 322 448 19 1.39 0.05149 0.00104 0.28413 0.00549 0.04029 0.00034 262.61823 46.40960 253.92821 4.34425 254.60255 2.09825
18XSG11-12 347 491 21 1.42 0.05102 0.00100 0.28297 0.00570 0.04033 0.00035 241.61252 45.39917 253.00693 4.50891 254.85231 2.16833
18XSG11-13 303 303 16 1.00 0.05172 0.00129 0.28600 0.00688 0.04033 0.00052 273.23716 57.01755 255.40424 5.43600 254.86556 3.22598
18XSG11-14 277 271 15 0.98 0.05060 0.00141 0.28129 0.00866 0.04035 0.00058 222.55786 64.31826 251.68285 6.86413 254.99052 3.61131
18XSG11-15 432 531 24 1.23 0.05167 0.00123 0.28679 0.00699 0.04036 0.00044 270.91240 54.51252 256.03325 5.51555 255.07438 2.70824
18XSG11-16 219 256 12 1.17 0.05085 0.00271 0.28257 0.01494 0.04039 0.00060 233.94178 122.80923 252.69145 11.83102 255.23405 3.69472
18XSG11-17 266 332 15 1.25 0.05170 0.00220 0.28728 0.01208 0.04046 0.00065 272.18221 97.36731 256.41435 9.52978 255.69555 3.99674
18XSG11-18 2214 1479 112 0.67 0.05077 0.00118 0.28405 0.00706 0.04048 0.00063 230.32009 53.50437 253.86754 5.58259 255.82961 3.90924
18XSG11-19 258 308 14 1.19 0.05059 0.00171 0.28314 0.01071 0.04048 0.00065 222.30992 77.94628 253.14426 8.47522 255.83191 4.03556
18XSG11-20 284 334 16 1.18 0.05119 0.00099 0.28513 0.00504 0.04049 0.00035 249.51167 44.49065 254.71927 3.98139 255.89568 2.18967
18XSG11-21 270 275 15 1.02 0.05173 0.00128 0.28864 0.00750 0.04051 0.00054 273.27247 56.80927 257.48545 5.91149 256.01441 3.33372
18XSG11-22 247 279 14 1.13 0.05180 0.00171 0.28863 0.00978 0.04054 0.00058 276.62797 75.54745 257.47784 7.70645 256.20665 3.57857
18XSG11-23 192 216 11 1.13 0.05169 0.00142 0.28860 0.00783 0.04055 0.00041 271.84486 63.17471 257.45876 6.16958 256.26289 2.55778
18XSG11-24 237 242 13 1.02 0.05031 0.00146 0.27965 0.00791 0.04057 0.00058 209.12693 67.14474 250.37762 6.27272 256.36658 3.59743
18XSG11-25 253 342 14 1.35 0.05013 0.00220 0.27987 0.01161 0.04065 0.00083 200.79700 101.82341 250.55223 9.21420 256.88298 5.15797
18XSG11-26 339 520 21 1.53 0.05086 0.00163 0.28376 0.00878 0.04065 0.00046 234.69723 74.06923 253.63532 6.94197 256.88476 2.82308
18XSG2-quartz porphyry, weighted mean age: 254.3 ± 1.1 Ma, MSWD = 0.116
18XSG21-1 622 315 29 0.51 0.05108 0.00082 0.28144 0.00490 0.03996 0.00034 244.62329 37.16388 251.79940 3.88583 252.56887 2.10306
18XSG21-2 404 558 24 1.38 0.05184 0.00155 0.28623 0.00814 0.04008 0.00040 278.41178 68.55784 255.59015 6.42689 253.35592 2.46419
18XSG21-3 796 518 40 0.65 0.05098 0.00087 0.28212 0.00444 0.04011 0.00039 240.00655 39.54202 252.33405 3.51374 253.51168 2.42252
18XSG21-4 322 229 16 0.71 0.05155 0.00121 0.28455 0.00654 0.04011 0.00040 265.71394 53.95271 254.25664 5.17224 253.53616 2.50892
18XSG21-5 411 326 21 0.79 0.05088 0.00138 0.28126 0.00792 0.04012 0.00046 235.20489 62.51900 251.65580 6.27676 253.55114 2.87919
18XSG21-6 653 501 34 0.77 0.05240 0.00101 0.29010 0.00568 0.04014 0.00039 302.95284 44.07263 258.64185 4.47002 253.67520 2.40100
18XSG21-7 495 481 26 0.97 0.05156 0.00084 0.28509 0.00482 0.04014 0.00037 265.73063 37.57581 254.68690 3.80942 253.71665 2.27398
18XSG21-8 548 155 25 0.28 0.05132 0.00087 0.28504 0.00544 0.04016 0.00037 255.37216 38.99096 254.64898 4.29857 253.83307 2.31534
18XSG21-9 399 294 21 0.74 0.05114 0.00156 0.28403 0.00892 0.04019 0.00043 247.17875 70.42622 253.84980 7.05674 254.00163 2.67342
18XSG21-10 491 431 25 0.88 0.05169 0.00125 0.28724 0.00721 0.04020 0.00054 271.71940 55.27211 256.38561 5.68736 254.06274 3.32777
18XSG21-11 570 528 31 0.93 0.05137 0.00081 0.28510 0.00507 0.04029 0.00035 257.53897 36.37910 254.69304 4.00320 254.61519 2.13993
18XSG21-12 169 108 8 0.64 0.05172 0.00162 0.28464 0.00923 0.04031 0.00047 273.25698 71.91713 254.32936 7.29228 254.73663 2.91313
18XSG21-13 406 370 22 0.91 0.05126 0.00109 0.28449 0.00603 0.04031 0.00037 252.75751 48.75249 254.21339 4.76385 254.77976 2.29346
18XSG21-14 479 523 27 1.09 0.05148 0.00137 0.28600 0.00760 0.04033 0.00046 262.20087 60.97490 255.40573 6.00082 254.85345 2.83598
18XSG21-15 374 285 19 0.76 0.05098 0.00107 0.28395 0.00654 0.04034 0.00043 239.75846 48.33665 253.78688 5.16854 254.94869 2.65390
18XSG21-16 266 158 13 0.60 0.05093 0.00143 0.28384 0.00832 0.04036 0.00055 237.65258 64.53973 253.70299 6.58242 255.07761 3.41664
18XSG21-17 837 540 42 0.65 0.05114 0.00073 0.28510 0.00417 0.04037 0.00046 247.32116 33.06678 254.69482 3.29436 255.12577 2.84464
18XSG21-18 603 468 31 0.78 0.05114 0.00086 0.28604 0.00587 0.04040 0.00037 247.13819 38.88435 255.43923 4.63591 255.29862 2.31669
18XSG21-19 277 289 15 1.04 0.05160 0.00153 0.28690 0.00883 0.04041 0.00045 267.91562 67.81175 256.11619 6.96804 255.39846 2.81089
18XSG21-20 67 62 4 0.92 0.05213 0.00282 0.28623 0.01467 0.04043 0.00066 291.01991 123.70139 255.58632 11.57792 255.50768 4.11349
18XSG21-21 361 298 19 0.82 0.05114 0.00120 0.28502 0.00688 0.04046 0.00043 247.08752 54.01408 254.63222 5.43348 255.70845 2.67330
18XSG21-22 45 241 5 5.39 0.05249 0.00310 0.28681 0.01701 0.04054 0.00083 306.83536 134.44840 256.04430 13.42563 256.20864 5.12164
Table 3. Zircon in-situ Lu-Hf isotopic data for Xingshugou monzogranite (18XSG1) and quartz porphyry (18XSG2).
Table 3. Zircon in-situ Lu-Hf isotopic data for Xingshugou monzogranite (18XSG1) and quartz porphyry (18XSG2).
Sample name t (Ma) 176Yb/177Hf 2σ 176Lu/177Hf 2σ 176Hf/177Hf 2σ εHf(0) εHf(t) 2σ TDM1 TDM2 fLu/Hf
18XSG1-monzogranite
18XSG11-1 254 0.034836 0.000313 0.001295 0.000010 0.282638 0.000018 -4.7 0.6 0.6 876 1238 -0.96
18XSG11-2 254 0.050784 0.001333 0.001922 0.000038 0.282665 0.000020 -3.8 1.5 0.7 853 1186 -0.94
18XSG11-3 254 0.043135 0.000270 0.001606 0.000003 0.282639 0.000025 -4.7 0.6 0.9 882 1239 -0.95
18XSG11-4 254 0.065785 0.000262 0.002489 0.000020 0.282606 0.000018 -5.9 -0.7 0.6 952 1324 -0.93
18XSG11-5 254 0.041405 0.000424 0.001573 0.000009 0.282617 0.000017 -5.5 -0.2 0.6 913 1290 -0.95
18XSG11-6 254 0.029869 0.000413 0.001132 0.000018 0.282660 0.000018 -4.0 1.4 0.6 842 1189 -0.97
18XSG11-7 254 0.038559 0.000794 0.001436 0.000019 0.282590 0.000016 -6.4 -1.1 0.6 948 1349 -0.96
18XSG11-8 254 0.039654 0.000854 0.001438 0.000041 0.282615 0.000026 -5.6 -0.2 0.9 912 1292 -0.96
18XSG11-9 254 0.046882 0.000158 0.001802 0.000017 0.282618 0.000018 -5.4 -0.2 0.6 917 1289 -0.95
18XSG11-10 254 0.039331 0.000520 0.001508 0.000024 0.282616 0.000018 -5.5 -0.2 0.6 913 1292 -0.95
18XSG11-11 254 0.043702 0.001075 0.001638 0.000054 0.282498 0.000017 -9.7 -4.4 0.6 1084 1556 -0.95
18XSG11-12 254 0.043832 0.000219 0.001601 0.000015 0.282573 0.000023 -7.1 -1.7 0.8 977 1389 -0.95
18XSG11-13 254 0.050955 0.000358 0.001969 0.000009 0.282617 0.000019 -5.5 -0.2 0.7 922 1293 -0.94
18XSG11-14 254 0.038604 0.000614 0.001469 0.000029 0.282609 0.000017 -5.8 -0.4 0.6 922 1306 -0.96
18XSG11-15 254 0.033969 0.000432 0.001268 0.000020 0.282641 0.000016 -4.6 0.7 0.6 872 1233 -0.96
18XSG2-quartz porphyry
18XSG21-1 254 0.035607 0.000158 0.001366 0.000014 0.282686 0.000022 -3.0 2.3 0.8 809 1132 -0.96
18XSG21-2 254 0.036748 0.000397 0.001443 0.000010 0.282630 0.000025 -5.0 0.3 0.9 892 1260 -0.96
18XSG21-3 254 0.033863 0.000710 0.001309 0.000020 0.282693 0.000022 -2.8 2.6 0.8 798 1116 -0.96
18XSG21-4 254 0.037836 0.000151 0.001444 0.000006 0.282623 0.000026 -5.3 0.1 0.9 902 1275 -0.96
18XSG21-5 254 0.046779 0.000269 0.001818 0.000006 0.282652 0.000019 -4.3 1.0 0.7 869 1214 -0.95
18XSG21-6 254 0.039969 0.000349 0.001492 0.000011 0.282631 0.000023 -5.0 0.4 0.8 891 1256 -0.96
18XSG21-7 254 0.040807 0.000935 0.001567 0.000027 0.282634 0.000021 -4.9 0.4 0.7 888 1251 -0.95
18XSG21-8 254 0.038238 0.000165 0.001481 0.000013 0.282660 0.000029 -4.0 1.4 1.0 850 1192 -0.96
18XSG21-9 254 0.032690 0.000530 0.001213 0.000012 0.282682 0.000022 -3.2 2.2 0.8 812 1140 -0.96
18XSG21-10 254 0.043326 0.000585 0.001721 0.000033 0.282618 0.000029 -5.4 -0.2 1.0 915 1289 -0.95
18XSG21-11 254 0.041520 0.000398 0.001574 0.000013 0.282644 0.000025 -4.5 0.8 0.9 875 1230 -0.95
18XSG21-12 254 0.036700 0.000303 0.001430 0.000014 0.282665 0.000025 -3.8 1.6 0.9 841 1180 -0.96
18XSG21-13 254 0.032437 0.000125 0.001222 0.000003 0.282646 0.000025 -4.5 0.9 0.9 863 1221 -0.96
18XSG21-14 254 0.040993 0.001448 0.001493 0.000048 0.282623 0.000024 -5.3 0.0 0.8 903 1276 -0.96
18XSG21-15 254 0.042193 0.000783 0.001620 0.000032 0.282576 0.000025 -6.9 -1.6 0.9 973 1382 -0.95
* The parameter used in our calculations: (176Lu/177Hf)CHUR = 0.0332, (176Hf/177Hf)CHUR = 0.282772 [47]; (176Lu/177Hf)DM = 0.0384, (176Hf/177Hf)DM = 0.28325 [48]; λ(176Lu) = 1.867×10−11 a−1 [49]. The 176Lu/177Hf (C) = 0.015 [48]. t = 254Ma.
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