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Article

Geochemistry and Zircon U-Pb Chronology of West Kendewula Late Paleozoic A-Type Granites in the East Kunlun Orogenic Belt: Implications for Post-Collision Extension

by
Bang-Shi Dong
1,
Wen-Qin Wang
2,*,
Gen-Hou Wang
1,3,*,
Pei-Lie Zhang
1,
Peng-Sheng Li
1,
Zhao-Lei Ding
1,
Ze-Jun He
1,
Pu Zhao
4,
Jing-Qi Zhang
1 and
Chao Bo
1
1
School of Earth Sciencesand Resources, China University of Geosciences (Beijing), Beijing 100083, China
2
The Second Geological and Mineral Exploration Institute of Gansu Provincial Bureau of Geology and Mineral Exploration and Development, Lanzhou 730020, China
3
Department of Geological Engineering, Qinghai University, Xining 810016, China
4
Xidihuiyou Mining Technology Co., Ltd., Anning District, Lanzhou 730020, China
*
Authors to whom correspondence should be addressed.
Appl. Sci. 2025, 15(12), 6661; https://doi.org/10.3390/app15126661
Submission received: 2 March 2025 / Revised: 22 April 2025 / Accepted: 28 April 2025 / Published: 13 June 2025
(This article belongs to the Special Issue Technologies and Methods for Exploitation of Geological Resources)
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Abstract

The Late Paleozoic granitoids widely distributed in the central section of the East Kunlun Orogenic Belt (EKOB) are responsible for the constraints on its post-collisional extensional processes. We report the whole-rock geochemical compositions, zircon U-Pb ages, and zircon Hf isotope data of granites in the western Kendewula area. The granites, dated between 413.7 Ma and 417.7 Ma, indicate emplacement during the Early Devonian period. The granite is characterized by high silicon content (72.45–78.96 wt%), high and alkali content (7.59–9.35 wt%), high 10,000 × Ga/Al values, and low Al2O3 (11.29–13.32 wt%), CaO (0.07–0.31 wt%), and MgO contents (0.16–0.94 wt%). The rocks exhibit enrichment in large-ion lithophile element (LILE) content and high-field-strength element (HFSE) content, in addition to strong losses, showing significant depletion in Ba, Sr, P and Eu. These geochemical characteristics correspond to A2-type granites. The values of Rb/N and Ba/La and the higher zircon saturation temperature (800~900 °C) indicate that the magma source is mainly crustal, with the participation of mantle materials, although limited. In addition, the zircon εHf(t) values (−4.3–3.69) also support this view. In summary, the A2-type granite exposed in the western Kendewula region formed against a post-collisional extensional setting background, suggesting that the Southern Kunlun Terrane (SKT) entered a post-orogenic extensional phase in the evolution stage since the Early Devonian. The upwelling of the asthenospheric mantle of the crust, triggered by crustal detachment and partial melting, likely contributed to the flare-up of A2-type granite during this period. By studying the nature of granite produced during orogeny, the evolution process of the formation of orogenic belts is discussed, and our understanding of orogenic is enhanced.

1. Introduction

The East Kunlun Orogenic Belt (EKOB) is a significant key component of the East Tethys tectonic domain. The EKOB has preserved many extensive magmatic records from oceanic subduction events to continental collisional events during the Early Paleozoic [1,2,3,4]. There are mafic–ultramafic rocks, granites, and HP-UHP (High pressure-ultrahigh pressure metamorphic rocks) metamorphic rocks that developed from the Early to Late Paleozoic, documenting the change in the Proto-Tethys Ocean [5,6,7,8,9,10]. Geochronological and geochemical evidence from eclogites suggests that the EKOB experienced Proto-Tethys Ocean closure and deep continental crust subduction between the Early Silurian, and it was dominated by S-type granite magmatism in the Early Devonian (433−411 Ma) [7,11,12,13]. Subsequent investigations of mafic intrusive rocks have revealed post-collisional extension during the early part of the Late Paleozoic [14], which was temporally associated with Paleo-Tethys Ocean initiation and localized lithospheric mantle delamination [5,15,16,17,18,19]. With respect to Paleozoic magmatism during the Paleozoic, 2 out of 10 geologists generally suggest that the Early Silurian EKOB entered a collisional orogenic stage during the Early Silurian, in which magmatic activity was mostly dominated by S-type granite magmatism [19,20,21,22,23,24]. In general, several controversies remain: (1) Timing of continental subduction and magmatism—Eclogite evidence suggests that the EKOB may have entered a continental subduction process from the Early Silurian to the Early Devonian [12,13,23,25,26]. However, the age distributions of most A-type granites range from the Late Silurian to Early Devonian (432–410 Ma) [4,27,28]. (2) Deep mechanism of magmatic flare-up—Regarding the deep mechanism of magma flare-up during this stage, several geologists have proposed that this phenomenon is related to the subduction of slab break-off [4,27,29], whereas others have proposed that earlier slab break-off occurs earlier, emphasizing that the role of crustal detachment is greater [23,30]. (3) Spatial distribution of post-collisional magmatism—Some geologists have proposed that the magmatic rocks associated with some researchers argue that post-collisional extension-related magmatism should have been generated to the north of the Central Kunlun Fault. In contrast, the southern part is thought to be dominated by I-type granite [23,27]. These differing interpretations highlight the complexity of the tectonic and magmatic evolution of the EKOB.
Notably, owing to the harsh field environment conditions of the plateau, most scholars have focused primarily on the North Kunlun Terrane. The Late Paleozoic A-type granites emerging from the southern Kunlun Terrane deserve further investigation, particularly with respect to their magma source characteristics and deep geodynamic processes, to better constrain the tectonic process evolution of the EKOB related to the Proto-Tethys Ocean during the Late Paleozoic. Generally, A-type granite intrusions are typically associated with extensional environments (e.g., faulting, rifting, or post-orogenic extension) and often indicate the weakening of orogenic activity and the onset of stable cratonic conditions [31,32,33,34,35]. Its occurrence frequently indicates the weakening of orogenic activity and the commencement of stable cratons [34]. Unlike orogenic S-type granites, A-type granites are typically employed to constrain the identification of post-orogenic tectonic transition transformations in post-orogenic tectonic systems [3,36,37,38,39,40,41,42]. These granites present distinctive geochemical signatures, such as high alkali contents, low CaO contents, high enrichment in large-ion lithophile elements (LILEs), and high concentrations of high-field-strength elements (HFSEs) [10,29,31,33,37,38,40,43,44].
In this work, we report the present zircon U–Pb ages, whole-rock geochemistry data, and zircon Hf isotope data from A-type granite in the western Kendewula area to constrain the genesis of the igneous rocks and reconstruct the post-collisional evolution of the southern Kunlun Terrane during the Late Paleozoic.

2. Regional Geology

The EKOB is located west of the Qin–Qi–Kun orogenic system and east of the Altai fault zone and is an important component that forms a key part of the East Tethys domain. There are three major faults: the North Kunlun Fault, the Central Kunlun Fault, and the Southern Kunlun Fault. The EKOB can be divided into three secondary units: (1) the northern Kunlun Terrane (NKT), (2) the Central Kunlun Belt (CKB), and (3) the southeastern Kunlun Terrane (SKT) (Figure 1b) [6,22,45,46]. This back-arc aulacogen developed between the Qaidam Block and CKB during the Early Paleozoic, resulting in complex lithological assemblages, including a Precambrian metamorphic basement, Late Paleozoic volcanic–sedimentary sequences, and Paleozoic–Triassic granitoids. High-grade metamorphic events at ~1.8 Ga record two phases of Paleozoic tectonothermal activity, which was subsequently overprinted by Late Paleozoic volcanic–sedimentary deposition [10,28,47,48,49]. The CKB is considered a suture zone that has experienced multiple magmatic episodes from the Proterozoic to the Mesozoic, with these widespread intrusions being widely distributed in the Precambrian crystalline basement [17,22,25,50,51]. The SKT primarily consists of Early Paleozoic metamorphic volcanic rocks (Naij–Tai Group), Late Paleozoic to Mesozoic sediments, and Early Paleozoic and Late Triassic granitoids. In particular, more granitoids are present [23,46]. These rocks record the long-term prolonged tectonic evolution of the Proto- and Paleo-Tethys oceans from the Neoproterozoic to the Late Mesozoic, including subduction and collision events [10,22,31,52,53,54]. In particular, during magmatism in the SKT, magmatism is primarily composed of granites, encompassing minor quantities of mafic–ultramafic rocks. These intrusions primarily date to the ages of these rocks, which are largely concentrated in the period from the Central-to-Middle Ordovician–Middle-to-Central Devonian and from the Central-to-Middle Permian–Late-to-Late Triassic. Overall, the majority of the intrusions are dominated by intermediate to acidic magmatic rocks, such as S-type, I-type, and A-type granites, which are associated with collisional orogeny and subsequent extensional processes [3,23,30].

3. Local Geology and Samples

This work is focused on the granitoids distributed along the northern edge of the SKT (Figure 1b). In our study area, all the well-exposed outcrop features are clearly exposed, including Early–Middle–Central Proterozoic chlorite–mica schist (Pt1-2K), Early Paleozoic volcanic rocks of the Naij–Tai Group (OSN), Silurian–Ordovician amphibolite (ΨO), and pyroxenite (νσ). The primary intrusions include Central Silurian granodiorite (γδS2), Early Devonian granite and moyite (Figure 2; ηγD1, Figure 3a,b; ξγD1, Figure 3d,f). Some mafic–ultramafic rocks constitute the main intrusions in the study area (Figure 3c). The Central Silurian granodiorite is in intrusive contact with the Naij–Tai Group. The Central Triassic monzonitic granite was later intruded by early carboniferous K-feldspar granite. Owing to the influence of the Central Kunlun Fault, the study area has undergone significant deformation; it is generally distributed in the NW direction, with additional nearly E–W-trending and N–S-trending faults. This deformation of this belt is highly complex, and the patterns differ, with distinct structural layers. These areas are significantly different, among which the Early Mesoproterozoic mélange shows NW-trending foliation and intense internal trends toward the NW. The interior exhibits strong shear deformation. The specific sample locations are listed in Table S1 in the Supplementary Materials.

4. Results

4.1. Petrography

A total of 10 samples were collected for whole-rock geochemical analysis (Test data from Wuhan SampleSolution Analytical Technology Co., Ltd, the specific test process and data are presented in the appendix). Some plagioclase and hornblende in the 10 samples were slightly altered. Two of these samples were moyite samples (24QKKG-J1 4/10 and 24QKKGJ2) taken for whole-rock geochemical analysis, and three of these samples were selected for zircon U–Pb dating. The granites have a salmon-red appearance, exhibiting typical medium-to-coarse-grained textures and massive structures. The rocks are mainly composed of quartz (30–40%), K-feldspar (30–40%), plagioclase (15–20%), and a small amount of hornblende (~8%) (Figure 3e). The moyites exhibit a flesh red color, similar to typical medium-to-coarse-grained textures, and massive structures, which include quartz (30–35%), K-feldspar (35–40%), plagioclase (10–15%), and a small amount of minor hornblende (~5%) (Figure 3d,f). Petrography reveals that the mineral crystallization particles are relatively large, which may be related to the high content of silica; the magma has a relatively high viscosity that cools slowly, and the duration of mineral separation crystallization is long.

4.2. Zircon U-Pb Chronology

The detailed zircon U–Pb chronology data for three samples—moyite (24QKKG-J1) and granite (24QK0612-4, 24QK0812-1)—are listed in Table S1 (Test data from Wuhan SampleSolution Analytical Technology Co., Ltd, the specific test process and data are presented in the appendix). According to the mineral sorting results, there are no significant differences between zircons from granite and those from moyite. These zircons are predominantly prismatic, with well-formed long and short columns featuring good crystal shapes and uniform sizes, lengths ranging from 120 to 180 μm, and aspect ratios ranging from 2:1 to 3:1. Cathodoluminescence (CL) images reveal distinct oscillatory zoning of clear rhythmic rings of zircon, which is consistent with the typical characteristics of magmatic zircons (Figure 4). The chondrite-normalized rare earth element (REE) patterns (Figure 5) appear to be depleted. In the distribution of standardized rare earth elements (REEs) in chondrites (Figure 5), zircon grains show the depletion of light REEs (LREEs), positive Ce anomalies, and negative Eu anomalies, and the calculated Th/U ratios are greater than 0.1 (Figure 5), with an average value of approximately 0.41, indicating that these zircons are further evidence of their magmatic origin. The weighted average ages of the 24 measured zircon grains are 413.7 ± 2.4 Ma for sample 24QK0612-4, 418.0 ± 3.0 Ma for sample 24QK0812-1, and 417.4 ± 1.8 Ma for sample 24QKKG-J1 (Figure 4). The concordant ages of the three samples (413.7 ± 1.2 Ma, 417.7 ± 1.3 Ma, and 417.5 ± 0.96 Ma) and their weighted mean ages are consistent within the error margin range, indicating that the granites intruded during the Early Devonian.

4.3. Hf Isotope Data

The sites used for U-Pb dating are used for in situ zircon Hf isotope analysis (Supplementary Materials; Figure 6). The ten Hf isotope data points are from sample 24QK0612-4. The 176Yb/177Hf values range from 0.003566 to 0.073000, the values of 176Lu/177Hf range from 0.000083 to 0.001466, and the values of 176Hf/177Hf range from 0.282393 to 0.282632. The zircon εHf(t) values range from −4.30 to +3.69, corresponding to TDM2 model ages between 1.0 Ga and 1.4 Ga. In the εHf(t) vs. age diagram (Figure 5), nearly all the samples are plotted around the chondritic uniform reservoir (CHUR).
Applsci 15 06661 g005
Figure 5. Zircon trace element diagram and U−Pb concordia diagrams of zircons from the west Kendewula granitoids.
Figure 5. Zircon trace element diagram and U−Pb concordia diagrams of zircons from the west Kendewula granitoids.
Applsci 15 06661 g005

4.4. Whole-Rock Major Elements

The major and trace element compositions and correlation coefficients of the 10 samples are listed in Table S1. Evidently, in this study, both granite and potassium feldspar granites contain similar main major element compositions; thus, in this chapter, we do not distinguish between lithological distinctions that are not emphasized in this section. These granitoids have high contents of SiO2 (72.5–79.0 wt.%), high total alkalinity (K2O + Na2O = 7.59–9.13 wt.%), and low contents of CaO (0.16–0.97 wt.%), MgO (0.05–0.36 wt.%), TiO2 (0.06–0.32 wt.%), and P2O5 (0.01–0.07 wt.%), which are characteristics similar to those of A-type granites [55]. In the R1–R2 classification diagram [56,57,58,59], all the samples are plotted within the granite field region (Figure 7a). In the K2O–SiO2 diagram, they are plotted within the shoshonitic and high-K calc-alkaline fields (Figure 7b). Most of the A/CNK values are approximately 1.0, classifying them as mostly weakly peraluminous granites (Figure 7c). In the Na2O–K2O diagram, all the samples are plotted within or near the A-type granites and their boundaries (Figure 7d).

4.5. Whole-Rock Trace and REE Contents

In the primitive mantle-normalized trace element diagrams, these samples present irregular curves with distinct right-inclined trends, marked by strong positive anomalies of Rb, Tb, U, La, Ce, and Nd and negative anomalies of Ba, Nb, Sr, and Li, which are consistent with those of representative A-type granites in the EKOB (Figure 8a). Additionally, the majority of the granitoids have high concentrations of Zr (113.53–338.24 ppm), Nb (14.3–24.3 ppm), Yb (2.26–7.00 ppm), and Ga (20.45–24.07 ppm). For the granites, the total rare-earth elements (∑REEs) in the granites are concentrated in the range of 340.4 × 10−6 to 525.2 × 10−6 ppm, with LREE/HREE ratios ranging from 7.98 to 13.15, indicating an abundance of LREE enrichment. The REE partition pattern clearly has distinct negative Eu anomalies, with δEu values ranging from 0.73 to 1.28. The standardized distribution pattern of REE chondrites clearly shows a characteristic “seagull”-shaped pattern in the chondrite-normalized REE distribution (Figure 8b), which is consistent with the Late Paleozoic granites around the EKOB. Notably, compared with granite, moyite has lower LREE contents and more significantly pronounced negative Eu anomalies (0.037 and 0.076). The REE distribution curve does not show a strong rightward dip. Additionally, the two samples are collected near the contact zone between the intrusion and schist or diabase, which may have resulted in even lower LREE contents (26.76 and 112.16 ppm) and more significant negative Eu depletion anomalies (0.02 and 0.38), likely due to the localized geological interactions.

5. Discussion

5.1. Petrogenesis

The analysis of petrological and genetic data is crucial for understanding granite formation. On the basis of the classification research by Collins [37] on the classification of granites and moyites, the plotting results confirm that all the samples are A-type granites (Figure 9a). The granites and moyites are characterized by high silicon contents (72.45–78.96 wt.%), high alkali-material contents (7.59–9.35 wt.%), high 10,000 × Ga/Al values (mostly greater than > 3), and low Al2O3, CaO and MgO contents. These samples are enriched with large-ion lithophilic elements (Rb, and K), high-field-strength elements (Zr and Hf), and HFSEs (Zr and Hf). The samples are strongly depleted while significantly depleting Ba, Sr and P, and significantly pronounced negative Eu anomalies are present as well. These geochemical characteristics confirm that the granites and moyites exposed in the study area are A-type granites.
However, the high ΣREE content (97.8–525.2 ppm) and the depleted Ta and Nb seem to differentiate these samples from typical A-type granites. In the Nb-10,000 × Ga/Al diagram for A-type granites (Figure 9b), the sample plots are near the boundary between I- and S-type granites and A-type granites, indicating its transitional characteristics. The highly differentiated I- and S-type granites have geochemical compositions similar to those of A-type granites and relatively similar geochemical elemental compositions, making distinction challenging. However, all samples have notably low P2O5 contents (0.01–0.07%), high Na2O contents (2.32–4.08%), and A/CNK values less than 1.1. These characteristics are inconsistent with those of highly fractionated I-type granites. In the mapping results of multiple various granite genetic types, most samples are plotted in the A-type granite field region, confirming their classification. The analysis reveals that the granitoids in this study are A-type granites. Furthermore, according to the diagram of the A-type granite subclassification diagram, the samples plot within the region of the A2-type granite field (Figure 9c,d), and the geochemical composition is characterized by a high Y/Nb ratio (>1.2), which is generally greater than 1.2. These geochemical characteristics suggest that these granitoids formed in a post-orogenic environment and are associated with the partial crustal melting of the crust [3,33,66].

5.2. Magmatic Evolution

With respect to the magmatic sources of A-type granites, scholars have previously drawn the following four main conclusions: (1) A-type granites are formed by the separation and crystallization of mantle-derived alkaline basaltic magma [67]; (2) A-type granites are formed by mixing crustal and mantle-derived magma [68]; (3) A-type granites are formed by the direct partial melting of silicate middle-upper crust [69]; and (4) A-type granites are formed by the partial melting of continental lower crust caused by mantle-derived magma underthrusting [70]. The granites and the moyites are not associated with many basic or intermediate rocks and are covered by a large area of granite in the study area. Many basic magmatic rocks have been found; thus, the A-type granite in this area is unlikely to have formed by the separation and crystallization of mantle-derived alkaline basaltic magma. Moreover, partial melting of mantle-derived material can only form mafic magma or intermediate magma, making it impossible to directly produce granite magma. Second, the content of SiO2 in the A-type granite studied in this paper is extremely high (72.45~78.96), and the ratio of trace rare earth elements is close to the reference value of crustal rocks but quite different from the corresponding ratio of the mantle. These characteristics indicate that the magma source of the A-type granite studied in this paper is the crust rather than the mantle. Combined with the view that the formation of A-type granites proposed by Zhang [4] is independent of the source rock and related only to pressure, the formation of A-type granites can occur only in the lower crust. In addition, the partial melting of silicate-rich middle–upper crust materials occurs in a shallow and low-pressure environment. The required temperature is not high, and the lowest zircon saturation temperature of the A-type granites studied here is 800 °C, which is obviously inconsistent with this environment.
In the εHf(t)–age diagram (Figure 6), almost all samples are plotted between the depleted mantle and chondrite evolution lines. These lines are even closer to the chondrite uniform reservoir evolution line. The Hf model ages (tDM2 = 1.0~1.4Ga εHf(t) = –4.3~3.69 (Table S1)) and the εHf(t) values of most samples are positive and relatively low in value. Rocks with low and positive εHf(t) values indicate that their magma source areas probably involve mantle-derived materials [71,72] and the average value of Ba/La is 10.67, which is slightly greater than the reference value of the crust (9.6) [73,74]. A higher zircon saturation temperature (800~900 °C) supports the contribution of mantle-derived materials during diagenesis, and the two most common methods for mantle-derived materials to participate in the rock-forming process are as follows: (1) mixing with the generated felsic mag in the deep crust and (2) first intruding into the crustal basal rocks to form the primary crust and then undergoing partial melting by dehydration. The A-type granite formed by mantle-derived materials through the second method mostly shows quasi-aluminous characteristics [67], which are different from the weakly over-aluminous characteristics of the A-type granites studied in this work. Abnormal silicon, which is rich in alkalis and significantly depleted in Ca, Mg, Nb, Ta, P, Ti, Eu and other elements shown in this study, indicate that such materials have undergone differentiation evolution [75]. The abnormal depletion of these elements is mostly related to the separation and crystallization of some minerals, such as the significantly poor P and Ti characteristics caused by the separation and crystallization of phosphorite and titanium magnetite and the high distribution coefficient of rutile for Nb and Ta [76]. The low contents of Nb and Ta in the rock may be caused by the separation crystallization of rutile. The strongly negative Eu anomaly indicates the crystallization of plagioclase. Therefore, A-type granites should involve the direct mixing of mantle-derived materials with their induced felsic magma in the crust. However, the mantle-derived materials are limited, and the geochemical properties of these A-type granites are still more similar to those of crustal materials.

5.3. Tectonic Significance

The EKOB is an important key magmatic–tectonic belt that records the Paleozoic evolutionary process of the Proto-Tethys Ocean during the Paleozoic. Due to the sustained subduction of the Central Kunlun Ocean (CKO), the SKB and NKT collided during the Central–Middle Silurian, ultimately resulting in the closure of the CKO [4,23]. Since the Late Silurian, the EKOB has entered a post-orogenic extensional stage characterized by intense magmatism and the widespread distribution of A-type granites and mafic dikes [6,30,35,41,52,77,78,79]. This activity has resulted in the formation of an EW-trending magmatic belt with ages ranging from the Late Silurian to the Central Devonian. As noted above, A2-type granites formed during the post-collisional orogenic setting [33]. All the data from the Early Devonian A-type granites in this study are plotted within the post-collisional field of the Rb–Y + Nb and Nb–Y region diagram (Figure 10a,b), whereas the Hf–3Ta diagram shows that the samples further support their post-collisional characteristics (Figure 10d). In addition, the aluminum and high-K calc–alkaline characteristics of these features are consistent with those of the granites found in the EKOB, which should be related to the final stages of the collision process [4,18,30,31,80]. During the Early Cambrian, the opening and expansion of the Proto-Tethys Ocean had already occurred [81]. From the Late Cambrian to the Late Ordovician, subduction of the Proto-Tethys Ocean occurred leading to island arc magmatism [82]. Many central Silurian S-type granites associated with continental collision have been identified in the EKOB [83], corresponding to a period when the Proto-Tethys Ocean was closed. In the Early Devonian, the ongoing collision between the SKB and the NKT led to the continuous thickening of the crust. This process was followed by the gravitational collapse of the lower part of the overthickened crust and continuous asthenospheric upwelling of the lower asthenosphere, resulting in extensional tectonics [84,85,86]. In addition, the above evidence, including the Late Silurian–central Devonian molasse formation [87] and the coeval mafic-ultramafic magmatism, also provide evidence of a post-orogenic extensional environment that may be caused by delamination and the associated asthenospheric upwelling of the asthenosphere (Figure 11) [23,30,84,88,89]. In addition, there are many 420–450 Ma magmatic rocks in the eastern Kunlun orogenic belt, and the continuous and magmatic activity over the past 30 years supports this view (Table S1). In summary, the Early Devonian A2-type granite in the western Kendewula region formed because of these deep-seated geodynamic processes.

6. Conclusions

Under microscope observation, it is evident that the western Kendewula granitoids of the EKOB are mainly composed of mineral grains and the whole-rock geochemistry reveals extremely high SiO2 contents, alkali and light rare earth element enrichment, positive anomalies of Zr and Ga, negative anomalies of Sr, Ba and Eu, and values of Nb and Ta close to the reference values of crustal rocks. Moreover, we find εHf(t) values of –4.3~3.69, Hf model ages of tDM2 = 1.0~1.2 Ga, and εHf(t) values that are positive and low. Thus, the exposed granites and potash-feldspar granites in Kangduolha west of the eastern Kunlun Mountains are A2-type granites. The magma source is mainly crustal, with the limited participation of mantle materials. Precise zircon U–Pb dating geochronology (zircon U–Pb ages: 413.7–417.7 Ma) confirms that the EKOB enters a post-orogenic extensional stage during the Early Devonian. The asthenospheric upwelling of asthenospheric mantle triggered by crustal detachment and partial melting of the crust is the reason for the flare-up of A2-type granites during this period.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/app15126661/s1; Data compression package. “Supplement S1: Test data” is the result of the analysis of major and trace elements, “Table S1: The ages of the diffente geologic units from various terranes in the East Kunlun Mountains” is mentioned in the caption of Figure 1 in the text.

Author Contributions

Conceptualization: B.-S.D. and W.-Q.W.; Methodology: B.-S.D. and G.-H.W.; Software: P.-L.Z.; Validation: G.-H.W.; Investigation: Z.-J.H., P.Z., Z.-L.D., J.-Q.Z. and C.B.; Data Curation: P.-S.L. and B.-S.D.; Writing—Original Draft: B.-S.D.; Writing—Review and Editing: G.-H.W. and W.-Q.W.; Visualization: P.-L.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This study was financially supported by the Kunlun Talent-Advanced Innovation and Innovative and Entrepreneurial Talent Project of Qinghai Province (20221201), the 1:50,000 mineral exploration and geological survey of the Hongshui (Gulang County), Jingtai region, Gansu Province (202248), the Special Support Fund for the Sixth Batch of Ten Thousand Person Plan Teachers (204301001), and the Development Fund (Gen-Hou Wang, F02041).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in this study are included in the article and Supplementary Material. Further inquiries can be directed to the corresponding authors.

Conflicts of Interest

Author Pu Zhao was employed by the company Xidihuiyou Mining Technology Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Figure 1. (a) Tectonic location of the East Kunlun Orogenic Belt (modified based on from [22,46]). Abbreviations: Altyn Tagh f.—Altyn Tagh Fault, AKS—Animaqing–Kunlun Suture, BNS—Bangong Nujiang Suture, IYS—Indus-Yarlung Suture, JS—Jinsha Suture, KLF—Karakomram Fault, LMS f.—Longmenshan Fault, MFT-Main Front Thrust, XSH-XJ f.—Xianshuihe-Xiaojiang Fault; (b) The simplified tectonic map showing the timing of magmatism along the central part of the East Kunlun Orogenic Belt (modified based on from [22,46]). All the age data and references are listed in Table S1.
Figure 1. (a) Tectonic location of the East Kunlun Orogenic Belt (modified based on from [22,46]). Abbreviations: Altyn Tagh f.—Altyn Tagh Fault, AKS—Animaqing–Kunlun Suture, BNS—Bangong Nujiang Suture, IYS—Indus-Yarlung Suture, JS—Jinsha Suture, KLF—Karakomram Fault, LMS f.—Longmenshan Fault, MFT-Main Front Thrust, XSH-XJ f.—Xianshuihe-Xiaojiang Fault; (b) The simplified tectonic map showing the timing of magmatism along the central part of the East Kunlun Orogenic Belt (modified based on from [22,46]). All the age data and references are listed in Table S1.
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Figure 2. Geological map of the west Kendewula of the East Kunlun Orogenic Belt (from 1:10,000 geological survey).
Figure 2. Geological map of the west Kendewula of the East Kunlun Orogenic Belt (from 1:10,000 geological survey).
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Figure 3. (a–d) Field outcrops; (e,f) sample; (g–i) micrography (the upper one is a single polarized view and the lower one is a cross-polarized view). Q—quartz; K-fsp—K-feldspar; Pl—plagioclase; Hbl—hornblende.
Figure 3. (a–d) Field outcrops; (e,f) sample; (g–i) micrography (the upper one is a single polarized view and the lower one is a cross-polarized view). Q—quartz; K-fsp—K-feldspar; Pl—plagioclase; Hbl—hornblende.
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Figure 4. Cathodoluminescence images, where zircon U-Pb points are white and zircon Hf isotope points are orange.
Figure 4. Cathodoluminescence images, where zircon U-Pb points are white and zircon Hf isotope points are orange.
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Figure 6. Zircon Hf isotope data.
Figure 6. Zircon Hf isotope data.
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Figure 7. (a) TAS classification and nomenclature diagram; (b) SiO2 vs. K2O diagram; (c) A/CNK vs. A/NK diagram; (d) K2O vs. Na2O diagram. (a) Based on [58,60]; (b) based on [59]; (c) based on [57]; (d) based on [56]. The data for granites around the west Kendewula region are from [35,61,62,63].
Figure 7. (a) TAS classification and nomenclature diagram; (b) SiO2 vs. K2O diagram; (c) A/CNK vs. A/NK diagram; (d) K2O vs. Na2O diagram. (a) Based on [58,60]; (b) based on [59]; (c) based on [57]; (d) based on [56]. The data for granites around the west Kendewula region are from [35,61,62,63].
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Figure 8. (a) Primitive mantle-normalized trace element spider diagrams; (b) chondrite-normalized REE patterns (the primitive mantle and chondrite data for normalization are from [64,65]; the data source of granites is the same as that in Figure 7).
Figure 8. (a) Primitive mantle-normalized trace element spider diagrams; (b) chondrite-normalized REE patterns (the primitive mantle and chondrite data for normalization are from [64,65]; the data source of granites is the same as that in Figure 7).
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Figure 9. Discrimination diagrams of genetic types for granites in the western Kendewula region (a) 10,000 × Ga/Al vs. (Na2O + K2O)/CaO diagram; (b) 10,000 × Ga/Al vs. Nb diagram; (c,d) analysis of A-type granite sub-class diagram [33,44].
Figure 9. Discrimination diagrams of genetic types for granites in the western Kendewula region (a) 10,000 × Ga/Al vs. (Na2O + K2O)/CaO diagram; (b) 10,000 × Ga/Al vs. Nb diagram; (c,d) analysis of A-type granite sub-class diagram [33,44].
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Figure 10. Tectonic setting discriminant diagrams of the west Kendewula region, eastern EKOB (based on [90]): (a) Y + Nb vs. Rb diagram; (b) Y vs. Nb diagram; (c) R1 vs. R2 diagram; (d) Yb + Ta vs. Rb diagram, with VAG (volcanic arc granite), ORG (ocean ridge), WPG (in plate granite) syn-LOG (late orogeny granite), POG (post-orogenic granite), post-COLG (post-collisional granite); syn-COLG (syn-collisional granite).
Figure 10. Tectonic setting discriminant diagrams of the west Kendewula region, eastern EKOB (based on [90]): (a) Y + Nb vs. Rb diagram; (b) Y vs. Nb diagram; (c) R1 vs. R2 diagram; (d) Yb + Ta vs. Rb diagram, with VAG (volcanic arc granite), ORG (ocean ridge), WPG (in plate granite) syn-LOG (late orogeny granite), POG (post-orogenic granite), post-COLG (post-collisional granite); syn-COLG (syn-collisional granite).
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Figure 11. Late Paleozoic post-orogenic extension model of the EKOB (modified from [23]). NKT—North Kunlun Terrane; SKT—Southern Kunlun Terrane; CKM—Central Kunlun Melange; CLM—Continent Lithosphere Mantle.
Figure 11. Late Paleozoic post-orogenic extension model of the EKOB (modified from [23]). NKT—North Kunlun Terrane; SKT—Southern Kunlun Terrane; CKM—Central Kunlun Melange; CLM—Continent Lithosphere Mantle.
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Dong, B.-S.; Wang, W.-Q.; Wang, G.-H.; Zhang, P.-L.; Li, P.-S.; Ding, Z.-L.; He, Z.-J.; Zhao, P.; Zhang, J.-Q.; Bo, C. Geochemistry and Zircon U-Pb Chronology of West Kendewula Late Paleozoic A-Type Granites in the East Kunlun Orogenic Belt: Implications for Post-Collision Extension. Appl. Sci. 2025, 15, 6661. https://doi.org/10.3390/app15126661

AMA Style

Dong B-S, Wang W-Q, Wang G-H, Zhang P-L, Li P-S, Ding Z-L, He Z-J, Zhao P, Zhang J-Q, Bo C. Geochemistry and Zircon U-Pb Chronology of West Kendewula Late Paleozoic A-Type Granites in the East Kunlun Orogenic Belt: Implications for Post-Collision Extension. Applied Sciences. 2025; 15(12):6661. https://doi.org/10.3390/app15126661

Chicago/Turabian Style

Dong, Bang-Shi, Wen-Qin Wang, Gen-Hou Wang, Pei-Lie Zhang, Peng-Sheng Li, Zhao-Lei Ding, Ze-Jun He, Pu Zhao, Jing-Qi Zhang, and Chao Bo. 2025. "Geochemistry and Zircon U-Pb Chronology of West Kendewula Late Paleozoic A-Type Granites in the East Kunlun Orogenic Belt: Implications for Post-Collision Extension" Applied Sciences 15, no. 12: 6661. https://doi.org/10.3390/app15126661

APA Style

Dong, B.-S., Wang, W.-Q., Wang, G.-H., Zhang, P.-L., Li, P.-S., Ding, Z.-L., He, Z.-J., Zhao, P., Zhang, J.-Q., & Bo, C. (2025). Geochemistry and Zircon U-Pb Chronology of West Kendewula Late Paleozoic A-Type Granites in the East Kunlun Orogenic Belt: Implications for Post-Collision Extension. Applied Sciences, 15(12), 6661. https://doi.org/10.3390/app15126661

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