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Gang Chen1Dechao Li1,2*
Xijun Liu1,2,3*Pengde Liu3Zhihan Bai1
Xiao Liu1,2
Rongguo Hu1,2Hao Tian1Yande Liu1Wenmin Huang1Yao Xiao1- 1Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, College of Earth Sciences, Guilin University of Technology, Guilin, China
- 2Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resources in Guangxi, Guilin University of Technology, Guilin, China
- 3National Key Laboratory of Arid Area Ecological Security and Sustainable Development, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, China
Paleozoic intrusive rocks are exposed in the Longshoushan area in NW China, in the Northern Qilian Block and on the southern edge of the Alxa Block. Understanding the petrogenesis and tectonic setting of these intrusive rocks is crucial for reconstructing the tectonic evolution and tectonomagmatic processes that occurred along the North Qilian Orogenic Belt between the Alxa and Central Qilian blocks. This study presents an integrated analysis of petrology, zircon U-Pb geochronology, whole-rock geochemistry, along with Sr–Nd–Pb isotopic data and zircon Hf–O isotopic analyses for these intrusive rocks. The Shandan intrusive rocks consist primarily of calc-alkaline quartz diorite (∼430 Ma) and diorite (∼403 Ma). These diorites are enriched in large-ion lithophile elements (e.g., Ba and U) and depleted in high field strength elements (e.g., Nb, Ta, and Ti), similar to subduction-related magmas. The Shandan diorites have enriched Sr and Nd isotopic compositions, with high initial 87Sr/86Sr ratios (0.705247–0.70618), variable εNd(t) values (−1.58 to −3.53), positive zircon εHf(t) values (+0.08 to +3.55) and low zircon δ18O values (5.75‰–6.38‰). The older zircon grains (430 Ma) yield εHf(t) values of +0.14 to +6.58 and the younger grains (403 Ma) yield negative εHf(t) values (+2.24 to −11.0). The geochemical and isotopic data suggest that the diorites were derived through low-degree partial melting of enriched subcontinental lithospheric mantle with the addition of crustal material and subduction-related sediment-derived melts. We suggest that the formation of the Shandan diorites was dominated by slab breakoff at ∼430 Ma, which created a window that enabled the upwelling of asthenospheric material and induced partial melting of the subcontinental lithospheric mantle and crust. At ∼403 Ma, slab breakoff was nearing end, leading to weaker asthenospheric upwelling.
1 Introduction
Post-collisional magmatism offers insights into orogenic tectonics, magma evolution, and crust–mantle interactions (Jahn et al., 1999; Liégeois, 1998). These processes are important in regional reconstructions and shed light on the mechanisms applicable to similar orogenic settings worldwide (Zhang et al., 2023). The post-collisional phase represents a transition from crustal thickening to thinning, attributed to gravitational collapse or extension of the lithosphere (Liégeois, 1998; Vanderhaeghe and Teyssier, 2001). This sequence typically includes slab breakoff, lithospheric delamination, and convective thinning due to thickening of the lithospheric mantle (e.g., Bird, 1979; Houseman et al., 1981; Kay and Mahlburg Kay, 1993; Molnar et al., 1998; von Blanckenburg and Davies, 1995). Slab breakoff typically occurs ∼1–5 Myr after continental collision due to density contrasts between the subducting oceanic and overriding continental lithospheres (Huw Davies and von Blanckenburg, 1995; von Blanckenburg and Davies, 1995). Slab breakoff induces convective upwelling in the asthenosphere, resulting in conductive heating that leads to the melting of the overlying mantle lithosphere. In turn, this results in the generation of basaltic and intermediate magmas, leading to granitic magmatism in the crust (van Hunen and Miller, 2015). The petrogenesis of post-collisional magmatic rocks, therefore, serves as a direct probe into the timing, triggers, and geodynamic consequences of slab breakoff, offering a window into deep lithospheric processes.
The North Qilian Orogenic Belt (NQOB), located between the Alxa and Central Qilian–Qaidam blocks in northeastern Tibet, is a typical Phanerozoic accretionary-to-collisional orogenic belt (Fu et al., 2020; Figure 1a). Numerous ophiolites, high-pressure/low-temperature metamorphic rocks, arc-related volcanic and intrusive suites, and flysch formations in the NQOB record the history of the North Qilian Ocean from seafloor spreading to subduction and closure (Song et al., 2013). Volcanic arc granitoids in the NQOB formed between 520 and 460 Ma and consist of diorite, granodiorite (Song et al., 2013; Wu et al., 2011), and S-type granite (Chen et al., 2014). The southern and northern margins of the Alxa Block are separated from the Central Asian and Qilian orogenic belts by the Badanjilin and Longshoushan faults, respectively. The extensive Paleozoic magmatic rocks in the Alxa Block provide an opportunity to study the tectonic evolution of the Paleo-Asian and Qilian oceans. Abundant Paleozoic volcanic rocks with crystallization ages of 460–230 Ma are exposed in the Alxa Block (Liu et al., 2016; Zeng et al., 2016).
Figure 1
Figure 1. (a) Major tectonic units in China. (b) Geological map showing the distribution of magmatic rocks in the Qilian Orogenic Belt and Alxa Block (after Song et al., 2013; Zhang L. Q. et al., 2017).
The Longshoushan Belt, which is situated on the southern margin of the Alxa Block and the northern margin of the NQOB (Figure 1b), hosts abundant early Paleozoic intermediate to felsic igneous rocks (Zhang L. Q. et al., 2017). The early Paleozoic magmatic activity is thought to have been associated with northward subduction of the Northern Qilian oceanic crust followed by collision and post-collisional activity (Song et al., 2013; Zhang L. Q. et al., 2017). Previous investigations into the 445–403 Ma magmatic rocks in the Northern Qilian region suggest that they were emplaced in a post-collisional setting after closure of the Paleozoic Northern Qilian Ocean (Cao and Song, 2009; Song et al., 2013; Wang et al., 2005; Xu et al., 2010); however, the post-collisional evolution of the Longshoushan Belt during the Paleozoic is poorly constrained. The uncertainty is centered on the petrogenesis of the 444–400 Ma arc granitoids of the Longshoushan Belt (Duan et al., 2015; Wang et al., 2019; Zhang et al., 2019). The 444–400 Ma intermediate to felsic igneous rocks in the Longshoushan Belt are thought to have originated from partial melting of the Precambrian Longshoushan Group with limited input of mantle material (Zhao et al., 2016; Zhou et al., 2016) or through the mixing of re-melted felsic igneous rocks and mantle-derived magmas (Wang et al., 2019; Zhang et al., 2018). A fundamental enigma persists: discerning the precise geodynamic mechanisms driving this magmatism, particularly the transition from collisional to post-collisional extension. The Middle Silurian Shandan diorites, exposed along the North Qilian Orogenic Belt (NQOB) and the southern margin of the Alxa Block, represent a crucial, yet hitherto under-examined, component of this post-collisional magmatic suite. Their emplacement age, spanning approximately 430 to 420 Ma, coincides with the inferred timing of slab breakoff following the closure of the North Qilian Ocean (Song et al., 2013; Wang et al., 2005). These diorites display geochemical characteristics consistent with significant mantle-crust interaction, rendering them an ideal lithological unit for investigating the intricate interplay between slab breakoff, mantle dynamics, and crustal anatexis. However, the unresolved questions surrounding their petrogenesis, source regions, and broader tectonic significance currently hinder a comprehensive understanding of the post-collisional evolutionary trajectory of the NQOB.
This study presents zircon U–Pb geochronology, Hf–O isotopes, whole-rock geochemistry, and Sr–Nd–Pb isotopic data from the Shandan diorites. We aim to (1) constrain their emplacement age and elucidate their petrogenetic processes, (2) identify mantle and crustal contributions to their source, and (3) evaluate their implications for post-collisional slab breakoff dynamics. By addressing these fundamental questions, we seek to illuminate the role of slab breakoff in driving Silurian magmatism and lithospheric reworking within the NQOB, thereby providing new constraints on the transition from collisional thickening to post-collisional extensional tectonics in the North Qilian orogen.
2 Geological setting
The Alxa Block is a triangular-shaped terrane adjacent to the northern part of the NQOB, bounded by the North China Craton to the east, the Central Asian Orogenic Belt to the north, the Tarim Craton to the west, and the Qilian Block to the south (Zhang L. Q. et al., 2017; Figure 1). The northwest-trending Longshoushan Belt is 30 km wide and extends for ∼300 km along the southwestern margin of the Alxa Block. It is bounded to the south by the dextral northwest-to west-striking Longshoushan Fault, which was active during the early Paleozoic Qilian Orogeny (Song et al., 2013; Zhang L. Q. et al., 2017). Large Palaeozoic granitic plutons occur along the boundary between the North Qilian Suture Zone and the Longshoushan Belt. Igneous rocks, ranging from ultrabasic dunite to granite, are abundant in the Longshoushan region (Gong et al., 2013; Liu et al., 2020). The sedimentary sequence above the Paleoproterozoic Longshoushan Group ranges from Mesoproterozoic to Paleozoic in age, beginning with the Mesoproterozoic Dunzigou Group, which unconformably overlies the basement rocks and consists mainly of low-grade metamorphic siliciclastic and carbonate formations (e.g., Gong et al., 2016; Wu et al., 2021). The Dunzigou Group is overlain by the Neoproterozoic Hanmushan Group (e.g., Gong et al., 2013), which contains rift-related siliciclastic rocks, limestone, mafic volcanic rocks, and glacial deposits. The Hanmushan Group is overlain by Cambrian strata, which are mostly exposed to the south of the Shandan Complex and consist of quartz sandstone, slate, and volcanic rocks intruded by late Paleozoic granitoids (e.g., Liu et al., 2020; Xue et al., 2017; Figure 2).
Figure 2
Figure 2. Simplified geological map of the Longshoushan region (modified after Duan et al., 2015).
During the Paleozoic, the Longshoushan region was influenced mainly by the North Qilian Ocean tectonic regime to the south. The NQOB, also referred to as the North Qilian Accretionary Belt, is an elongate NW–SE-trending belt that extends for >1,000 km between the Alxa Block to the north and the Qilian Block to the south (Song et al., 2017; Zhang J. X. et al., 2017). The NQOB consists of two ophiolite belts, volcanic rocks, granitoids, high-pressure metamorphic rocks, and accretionary complexes, and provides an important record of the geological processes that occurred at an ancient convergent plate margin (Song et al., 2014; Song et al., 2013; Song et al., 2007; Wang et al., 2005; Wei and Song, 2008; Wei et al., 2009; Wu et al., 1993; Zhang J. X. et al., 2017; Zhang L. Q. et al., 2017). A Cambrian–Ordovician arc complex (∼516–446 Ma), located between the two ophiolite belts, consists of boninitic complexes, felsic calc-alkaline volcanic rocks, and granitoid plutons (Song et al., 2013; Wang et al., 2005; Wu et al., 2010; Xia et al., 2003; Xia et al., 2012).
The Shandan Complex, which is located in the eastern segment of the northern margin of the NQOB (Figure 1b), consists primarily of ultramafic and mafic rocks, along with accretionary complexes containing serpentinized harzburgite, gabbro, basalt, and siliceous–argillaceous rocks. Extensive Paleozoic intrusive and volcanic rocks crop out in this area (Figures 2, 3). These rocks were emplaced sporadically during the Caledonian orogeny and are composed of quartz syenite, diorite, granodiorite, granite-diorite porphyrite dikes, and mafic dikes. The Shandan diorite is located at the southeastern part of the Shandan complex (Figure 3), intruding into the Cambrian Hanmushan Group’s limestone, schist and tuff, with an intrusive contact relationship with both granite and granodiorite. The contact zone between the Shandan diorite body and the surrounding rocks exhibits well-developed schistosity and is distributed along N-W regional fault zones.
Figure 3
Figure 3. Geological map of the Shandan area, showing the distribution of Shandan Complex and sample locations.
3 Sample description and analytical methods
3.1 Samples
Abundant magmatic rocks are exposed in the Shandan area to the west of the Longshoushan Fault. We collected several fresh samples of diorite and quartz diorite from the Shandan area. These rocks are part of the Neoproterozoic Hanmushan Formation, which has been fractured and exposed due to subsequent tectonic movements. The sample locations are shown in Figures 2, 3.
The quartz diorite samples are fine-to medium-grained and consist mainly of plagioclase (40–45 vol%), amphibole (30–40 vol%), pyroxene (8–10 vol%), quartz (5–8 vol%), and titanite (2–4 vol%) (Figures 4a, 5a, b). Most crystals are euhedral to subhedral. Plagioclase occurs as subhedral laths 0.1–5.0 mm in length. Amphibole occurs as anhedral to subhedral crystals located between plagioclase crystals and is 0.1–1.5 mm in length.
Figure 4
Figure 4. Field photographs of the Shandan quartz diorite and diorite in the Longshoushan region. Outcrops of (a) the Shandan quartz diorite, (b-d) the Shandan diorite.
Figure 5
Figure 5. Photomicrographs of the Shandan intrusions. (a, b) Quartz diorite and (c, d) diorite. Pl: plagioclase, Cpx: clinopyroxene, Hb: hornblende, Qtz: quartz. a and c are cpl; b and d are ppl.
The diorite is light to dark grey and medium-grained. It has a granular texture and is composed of plagioclase (55 vol%), amphibole (15–20 vol%), clinopyroxene (10–15 vol%), and magnetite (Figures 4b-d). Plagioclase grains are generally subhedral to anhedral and 0.3–1.0 mm in length. Anhedral to subhedral clinopyroxene (0.2–0.5 mm) and hornblende (0.25–3.0 mm) occur in interstices between plagioclase grains. Accessory minerals include Fe–Ti oxides and apatite (Figures 5b, c).
3.2 Zircon U–Pb dating and Hf-O isotope
All analyses were carried out at the Guangxi Key Laboratory of Hidden Metallic Ore Deposit Exploration, Guilin University of Technology, Guangxi, China. We separated zircon grains from three diorites (21SD-282, 21SD-74 and 21SD-79) using conventional heavy-liquid and magnetic methods, which we mounted in epoxy resin and polished with 0.25 μm diamond paste. The internal textures of the grains were carefully examined using transmitted- and reflected-light photomicrographs as well as cathodoluminescence (CL) images. The CL imaging was performed using a JXA-8230 R electron microprobe.
Zircon U–Pb dating and trace element analyses were carried out simultaneously using laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) comprising a quadrupole ICP–MS instrument (Agilent 7900) coupled to a GeoLas HD 193 nm ArF excimer laser with an automatic positioning system. The laser spots were 24 μm in diameter. Each analysis included ∼20–30 s of background acquisition (using a gas blank) followed by 50 s of acquisition of U, Th, 204Pb, 206Pb, 207Pb, and 208Pb data from the sample. Trace element contents were calibrated using NIST 610 glass and Si as external and internal standards, respectively. Isotopic fractionation was corrected using Plešovice zircon as an external standard. ICPMSDataCal (Liu et al., 2008) was used to calculate trace element contents and U–Pb isotopic ratios. Concordia ages and diagrams were obtained using Isoplot/Ex (Ludwig, 2003).
Hf isotopic analyses of the same zircon grains were conducted using an ArF excimer LA system attached to a Neptune Plasma multi collector (MC)–ICP–MS with a beam diameter of 44 μm, 30 s of ablation, repetition rate of 6 Hz, and laser beam energy density of 6 J/cm2. During data acquisition, the GJ-1 zircon standard was analyzed as an external standard to check the reliability and stability of the instrument.
Zircon oxygen isotope was measured using a Cameca IMS-1280-HR SIMS (secondary ion mass spectrometer) at the SKLaBIG, GIG-CAS. The detailed analytical procedures were similar to those described by Li et al. (2009) and Yang Q. et al. (2018). The 133Cs+ primary beam was accelerated at 10 kV with an intensity of about 2 nA and a beam size of about 20 μm. A normal incidence electron gun was activated to compensate for sample charging during analysis. Mass resolution of ca. 2,500 was obtained with multi-collection mode. The nuclear magnetic resonance (NMR) probe was used for magnetic field control. Oxygen isotope 18O and 16O were measured in two off-axis Faraday cups H1 and L′2, respectively. Each spot analysis took less than 3 min consisting of pre-sputtering (ca. 30 s), automatic secondary beam centering (ca. 60 s) and integration of oxygen isotopes (4 s/cycle × 16 cycles).
Measured 18O/16O ratios are reported as δ18O per mil (‰) values calculated relatively to oxygen isotopic composition of Vienna Standard Mean Ocean Water (18O/16O) VSMOW = 0.0020052 (Baertschi, 1976). The instrumental mass fractionation factor (IMF) for zircon was corrected using zircon standard Penglai (5.31‰, Li et al., 2010). All the fourteen measurements of the Qinghu zircon standard yielded a weighted-mean δ18O values of 5.6‰ ± 0.1‰ (2σ), within errors of the reported value of 5.4‰ ± 0.2‰ (Li et al., 2013).
3.3 Whole-rock geochemistry
Five samples of fresh rock were selected and crushed into small chips. Any chips that were strongly altered or included secondary veins were removed, and the remaining chips were soaked in 4 N hydrochloric acid for 30 min to leach out alteration minerals. The rock chips were then powdered using an alumina ceramic shatter box. Major-element compositions were determined using a ZSX Primus II X-ray fluorescence spectrometer. Calibration lines used in quantification were produced by bivariate regression of data from 36 reference materials encompassing a wide range of silicate compositions (Li et al., 2005). Analytical uncertainties are between 1% and 5%. The loss on ignition (LOI) of each sample was measured before major-element analyses, which were carried out after calcination.
Trace-element analyses were performed using an Agilent 7500CX ICP–MS instrument, employing the acid-solution method of (Liu et al., 2021). First, ∼50 mg of sample powder was placed in a bomb, and 0.5 mL of purified HNO3 and 1.0 mL of HF were added. The bomb was then placed in a high-pressure valve at 190°C for 48 h. After evaporation, 0.5 mL of purified HNO3 was added to the bomb, and this step was repeated. Subsequently, 4 mL of purified 4 N HNO3 was added to the bomb, which was then placed in the high-pressure valve at 170°C for 4 h. Finally, the solution was diluted 1,000 times, and 10 ppb of Rh was added as an internal standard to correct for instrument drift.
Sr–Nd–Pb isotopic compositions were determined using the method of Zhang Z. G. et al. (2021). The sample powder was dissolved in a Savillex Teflon cup by adding 2 mL of 22 N HF and 1 mL of 8 N HNO3, and then heated to 120°C on a hot plate for 5–7 days. After drying, 3 mL of HNO3 was added to dissolve the sample again. Sr was separated using SR-B50-A (100–150 µm) resin. Rare earth elements (REEs) were separated with AG 50-X8 cation exchange resin, and Nd was purified with HDEHP resin. Blanks contained <300 pg of Rb and Sr, and <100 pg of Sm and Nd. Mass fractionation was corrected by assuming an 88Sr/86Sr ratio of 8.375209 and a146Nd/144Nd ratio of 0.7219. Instrument stability was monitored using NBS-987 and JNdi-1 standard solutions for Sr and Nd isotopic compositions, respectively. Repeated analyses of NBS-987 and JNdi-1 yielded a mean 87Sr/86Sr ratio of 0.710294 ± 0.000016 (n = 40, 2 SD) and a mean 143Nd/144Nd ratio of 0.512081 ± 0.000008 (n = 40, 2 SD), respectively. The mean measured 87Sr/86Sr and 143Nd/144Nd ratios of BHVO-2 were 0.703549 ± 0.000008 and 0.512965 ± 0.000004, respectively.
Lead was extracted by placing sample powders in Teflon beakers and dissolving by adding 3 mL of concentrated HF and 1 mL of concentrated HNO3, then heating at 120°C for 5–7 days. Lead was purified using the conventional cation exchange technique (AG 1-X8, 200–400 resin) with diluted HBr as an eluant. The total procedural blanks contained <50 pg of Pb.
4 Results
4.1 Zircon U–Pb geochronology and zircon Hf–O isotopic compositions
We selected three intrusive rocks from Shandan, including diorite and quartz diorite, for zircon U–Pb age and Hf-O isotopic analyses (Figures 6, 7). The results of the zircon U–Pb geochronology and Hf-O isotopic analyses are listed in Supplementary Tables S1–S3, and the representative zircon CL images are presented in Figure 6d. Zircon grains from the three samples are euhedral, and most have lengths of 150–200 μm and widths of 80–140 μm. All the analyzed grains have euhedral concentric zoning and high U (431–9,800 ppm) and Th (43.2–11,492 ppm) contents and Th/U ratios (0.08–1.48), suggesting an igneous origin for the zircon grains and that their U–Pb ages represent the timing of crystallization of the Shandan intrusive rocks (Hoskin and Black, 2000).
Figure 6
Figure 6. (a–c) U–Pb concordia diagrams for the analyzed samples and (d) cathodoluminescence images of representative zircon grains.
Figure 7
Figure 7. (a) Zircon εHf(t) values versus age (Zhang L. Q. et al., 2021; Zhang L. Q. et al., 2017) and (b) zircon O–Hf isotopic composition diagrams for the quartz diorites and diorites in the Shandan area. The mean zircon δ18O value of mantle magmas (5.3‰ ± 0.3‰, 1σ) is from Valley et al. (1998).
The diorite sample 21SD-282 yielded a weighted mean 206Pb/238U age of 403 ± 3.1 (1σ, MSWD = 0.16), suggesting that it crystallized during the Early Devonian. The εHf(t) values are variable, ranging from +2.24 to −11.0, with TDM model ages of 1,271–927 Ma (Figure 6a). Zircon grains from the quartz diorite samples 21SD-274 and 21SD-279 yielded weighted mean 206Pb/238U ages of 430 ± 1.6 (1σ, MSWD = 0.01) and 430 ± 1.9 (1σ, MSWD = 0.36), respectively (Figures 6b, c), suggesting that they crystallized during the middle Silurian. Their εHf(t) values are variable, ranging from +0.14 to +6.58, with TDM model ages of 1,023–751 Ma (Figure 7a). In situ zircon Hf–O isotopic data for the quartz diorite sample 21SD-279 are listed in Supplementary Table S5. The quartz diorite has intermediate zircon δ18O values (5.75‰ ± 0.18‰–6.38‰ ± 0.18‰) and variable zircon εHf(t) values (+0.08 to +3.55), with two-stage Hf model ages of 1,416–1,196 Ma (Figure 7; Supplementary Table S5).
4.2 Whole-rock major and trace elements
The major and trace element compositions of the studied Shandan diorites are listed in Supplementary Table S4 and shown in Figures 8, 9. The LOI values for the sampled analyzed in this study were 2.21–2.69 wt%. All major oxide contents were normalized to LOI-free values before interpretation.
Figure 8
Figure 8. Major element discrimination diagrams for the Shandan diorites. (a) Total alkali (Na2O+ K2O) versus SiO2 diagram (after Maitre et al., 1986). (b) K2O versus SiO2 diagram (after Gill, 1981). Data for the Longshoushan post-collisional rocks are from Duan et al. (2015).
Figure 9
Figure 9. (a) Chondrite-normalized REE and (b) primitive-mantle-normalized trace element diagrams for the Shandan intrusive rocks. Chondrite and primitive mantle values are from Sun and McDonough (1989); Data for the Longshoushan post-collisional rocks are from Duan et al. (2015).
The Shandan diorites are characterized by intermediate SiO2 contents (52.47–55.69 wt%) and relatively high Al2O3 (16.57–18.49 wt%), CaO (5.99–7.29 wt%) and MgO (3.91–4.66 wt%) contents, with Mg# (Mg# = 100 × M Mg/[Mg + Fe2+]) of 48.2–59.4 and Na2O + K2O contents of 1.74–5.50 wt%. The rocks plot in the monzodiorite field on a total alkali versus silica diagram (Figure 8a). All rocks plot along the medium to high-K calc-alkaline series on a SiO2 versus K2O diagram (Figure 7b).
The rocks yield a restricted range of trace element contents. Chondrite-normalized REE patterns show enrichment in light REEs (LREEs) relative to heavy REEs (HREEs), with (La/Yb)N ratios of 12.7–23.6. The samples are also characterized by weakly negative Eu anomalies (Eu/Eu* = 0.91–0.97), suggesting slight fractionation of plagioclase during crystallization (Figure 9a). They show a remarkable enrichment in large-ion lithophile elements (LILEs; e.g., Ba and U) and depletion of high field strength elements (HFSEs; e.g., Nb, Ta, and Ti) on a primitive-mantle-normalized trace element diagram (Figure 9b), similar to subduction-related magmas. They have high Sr contents (192–374 ppm), low Y contents (192–374 ppm), and high Sr/Y ratios (11–25).
4.3 Whole-rock Sr–Nd–Pb isotopic compositions
The whole-rock initial Sr–Nd–Pb isotopic compositions of the Shandan diorites are listed in Supplementary Table S5 and shown in Figure 10. Their (87Sr/86Sr)i ratios and εNd(t) values were calculated using crystallization ages of 430–403 Ma (Figure 9). All samples yield a limited range of (87Sr/86Sr)i ratios (0.705247–0.706181) and εNd(t) values (−1.58 to −4.74), with two-stage Nd model ages of 1,374–1,447 Ma. The age-corrected Pb isotopic ratios of these diorites are variable, with 206Pb/204Pb(t) ratios of 17.996–18.225, 207Pb/204Pb(t) ratios of 15.566–15.576, and 208Pb/204Pb(t) ratios of 37.943–38.126. In plots of 207Pb/204Pb(t) and 208Pb/204Pb(t) versus 206Pb/204Pb(t) (Figure 11), all the samples plot above the Northern Hemisphere reference line and have similar isotopic compositions to those of typical Indian MORB.
Figure 10
Figure 10. εNd(t) vs. 87Sr/86Sr ratios for Shandan diorites, showing mixing trends between depleted mantle and lower crustal components. (Fu et al., 2020; Zhang et al., 2023). Data for the late Paleozoic intrusions on the northern margin of the North China Craton (NCC) are from Wu et al. (2006) and Zhang et al. (2018). Data for the Longshoushan post-collisional rocks are from Duan et al. (2015); The composition of the subcontinental lithospheric mantle (SCLM) beneath the NCC was estimated using xenoliths and perovskites in Paleozoic kimberlites (Yang et al., 2009). DM: depleted mantle (Workman and Hart, 2005). Data for Archean mafic lower crust and TTG gneisses in the NCC are from Chen et al. (2014) and Griffin et al. (2002).
Figure 11
Figure 11. Age-corrected (a) 207Pb/204Pb(t) and (b) 208Pb/204Pb(t) versus 206Pb/204Pb(t) ratios of diorites (430 Ma) from the Shandan area. Data for present-day Pacific–North Atlantic and Indian MORB are from the PetDB database (http://www.petdb.org/) and the compilation of Liu et al. (2014). Subducted sediments are from Plank and Langmuir (1998); Vervoort and Blichert-Toft (1999); Vervoort et al. (2011). The Northern Hemisphere reference line (NHRL) is from Hart (1984).
5 Discussion
5.1 Petrogenesis for the shandan diorite
The relatively high LILE and LREE contents of the Shandan diorites suggest they were contaminated by continental crust; therefore, before discussing the source of magma, we must assess whether crustal contamination occurred during their formation. The Zr/Nb ratios of most samples (8.32–15.6) are lower than that of the continental crust (11.43; Rudnick and Gao, 2003), with only sample 21SD-279 having a higher Zr/Nb ratio. All samples lack older inherited zircon grains, and their relatively homogeneous zircon Hf isotopic compositions indicate a limited extent of crustal contamination. In addition, the narrow range of SiO2 contents in the Shandan diorites suggests limited magma mixing during their evolution.
The Mg# (48–59) and Cr (5–63 ppm) and Ni (6.6–15.9 ppm) contents of the Shandan diorites are relatively low, below those of primitive-mantle-derived magmas (Mg# = 68–76, Cr = 300–500 ppm, Ni = 300–400 ppm; Hess, 1992). This suggests they experienced fractional crystallization. The variations in TiO2 (1.09–2.04 wt%) and Fe2O3T (7.42–10.19 wt%) contents are small, with a weak Ti anomaly (Figures 9a, b), indicating that Fe–Ti oxides were not a significant fractionating phase during crystallization. The Eu (Eu/Eu* = 0.91–0.97) and Sr anomalies of the Shandan diorites are small, indicating negligible fractionation or accumulation of plagioclase. The Ni content is nearly constant, and the positive correlation between V and Cr contents suggests that the petrogenesis of the Shandan diorites was dominated by the fractional crystallization of clinopyroxene and hornblende (Zhang et al., 2023; Figures 12a, b).
Figure 12
Figure 12. (a) V versus Cr, (b) Ni versus Cr, (c) Sr/Y versus Y (Defant and Drummond, 1990), (d) Th/La versus Ce/Pb (Mazza et al., 2020), (e) Th/Yb versus Ta/Yb (Pearce and Peate, 1995), and (f) La/Ba versus La/Nb diagrams for the Shandan diorites (Saunders et al., 1992). MORB, mid-ocean ridge basalt; WPB, within-plate basalt; SH, shoshonite; CA, calc-alkaline; TH, tholeiite; ALK, alkaline; TR, transitional. Data for the Longshoushan post-collisional rocks are from Duan et al. (2015); The reference fields for OIB, MORB, and high-U/Pb mantle (HIMU) sources are from Saunders et al. (1992).
The zircon ages (430–403 Ma) of the studied Shandan diorites indicate they formed during the middle Silurian and Early Devonian. The diorites have island-arc-like trace element compositions, with enrichment in LILEs and LREEs and depletion in HFSEs (Figure 9). The samples have low Nb/La (0.24–0.29), Nb/Th (1.04–3.31), and Nb/U (5.13–10.01) ratios, similar to subduction-related magmas and Longshoushan post-collisional rocks (Dilek and Furnes, 2014; Duan et al., 2015; Pearce et al., 2014). Magma can be produced in a subduction-related environment by (a) the release of fluids during dehydration of the subducting oceanic slab, (b) partial melting of sediments from the oceanic slab, and (c) partial melting of the oceanic slab itself (Tatsumi and Takahashi, 2006). Direct melting of the oceanic slab is unlikely in the present case, because it is often accompanied by the formation of adakites, an intermediate rock characterized by low Y and high Sr contents, and LREE-enriched REE patterns (Defant and Drummond, 1990). In contrast, the diorites of this study have low Sr/Y ratios and high Y contents and similar to Longshoushan post-collisional rocks (Figure 12c; Duan et al., 2015). Therefore, we suggest that these diorites were not derived through the direct partial melting of the oceanic slab. The enrichment of the studied rocks in LILEs and LREEs relative to HFSEs and HREEs suggests they were associated with subducted material (Figure 9; Pearce and Parkinson, 1993). The Shandan diorites have low and uniform Ce/Pb ratios, but variable Th/La ratios (Figure 12d), suggesting a significant input of sediment or sediment-derived melt into their source. The Th contents of sediments are more than two orders of magnitude greater than that of the mantle (Hawkesworth et al., 1997; Plank and Langmuir, 1998); therefore, the addition of sediment-derived melt to a source result in increasing Th/Yb ratios but has little effect on Ta/Yb ratios (Pearce, 2008). We can use the Th/Yb and Ta/Yb ratios help constrain the magma source of Shandan diorites, as they remain stable during partial melting and fractional crystallization (Pearce and Peate, 1995). The Shandan diorites yield a narrow range of Th/Yb and Ta/Yb ratios (Figure 12e). The Th/Yb ratio of all samples are higher than those of the MORB–ocean island basalt (OIB) array, implying that the Shandan diorites added the subducted sediment melt elevated the Th abundance in the source. This suggests that contributions from subduction-related sediment-derived melts to their source.
The Shandan diorites are characterized by high MgO (3.91–4.66 wt%) and Mg# (48–59), Cr (5.18–63.3 ppm) and Ni (7.1–46.8 ppm) contents. In contrast, their SiO2 contents (52.48–50.72 wt%) are lower than that of the continental crust (SiO2 = 60.6 wt%), suggesting the incorporation of mantle-derived components (Pearce et al., 2014). LILEs and LREEs are enriched in the samples, with high Sr contents and Th/U ratios (2.81–4.79), similar to the incompatible element enrichment in the lithospheric mantle (Hawkesworth et al., 1993; Liu et al., 2023). This enrichment can be attributed to metasomatic processes associated with subduction or partial melting. In addition, the Shandan diorites yield high La/Nb ratios (3.43–4.41) and low La/Ba ratios (0.02–0.06) (Figure 12f), similar to subcontinental lithospheric mantle melts influenced by subduction (Thompson et al., 2008). Therefore, it is plausible that the Shandan diorites originated from an enriched source in subcontinental lithospheric mantle and similar to Longshoushan post-collisional rocks (Duan et al., 2015).
The whole-rock Sr–Nd–Pb and zircon Hf isotopic data further constrain the characteristics of the mantle source of the Shandan diorites. The Shandan diorites yield enriched Sr and Nd isotopic compositions, with high initial 87Sr/86Sr ratios (0.705,247–0.706,181) and variable initial εNd(t) values (−1.58 to −4.74). Their Sr–Nd isotopic signature suggests the possible incorporation of subcontinental lithospheric mantle and the mafic lower crust into their magma source, similar to the Longshoushan post-collision rocks (Duan et al., 2015). The samples yield a narrow range of 207Pb/204Pb(t) and 208Pb/204Pb(t) ratios. Due to the mobility of Pb, the Pb isotopic composition of the mantle can be altered by the addition of slab-derived fluids or sedimentary melts, allowing us to identify subducted-sediment-derived melts in the mantle source (Liu et al., 2014; Liu et al., 2021b; Pearce and Peate, 1995). On 207Pb/204Pb(t) versus 206Pb/204Pb(t) and 208Pb/204Pb(t) versus 206Pb/204Pb(t) diagrams (Figures 11, 13a), the Shandan diorites fall in the overlapping Indian Ocean MORB and subducted sediment fields, suggesting an Indian Ocean MORB-like source with the incorporation of subducted sediment.
Figure 13
Figure 13. (a) 143Nd/144Nd(t) versus Th/Nd diagram for the Shandan diorites, showing mixing models between GLOSS or GLOSS melt and DMM. (b) In situ zircon εHf(t) versus δ18O values (modified from Li et al., 2009). Data for subducted sediment are from Nowell et al. (1998); Plank and Langmuir (1998); Vervoort et al. (2011). The fields for present-day Pacific–North Atlantic and Indian MORB are from Liu et al. (2014), DMM trace element contents are from Workman and Hart (2005), and sediment/melt and sediment/fluid partition coefficients are from Johnson and Plank (2000).
Moreover, as the sediments have undergone surface weathering, they yield considerably higher δ18O values (>8.0‰) than those of the mantle (δ18O = 5.3‰ ± 0.3‰; Li et al., 2009). Zircons derived from the Earth’s mantle typically have δ18O values between approximately 5.3‰ ± 0.3‰ (Li et al., 2009). For Shandan diorites, the δ18O values of zircon between 5.75‰ and 6.38‰ is generally indicating the primary source remained mantle-derived, but the slight enrichment in δ18O in zircons within the diorite suggests the mantle source partially influenced by subduction components or crustal contamination (Figure 7b). On a zircon Hf–O isotopic diagram, the Shandan intrusive rock plots between the Qinghu monzogranite (representing mantle O isotopic compositions; Li et al., 2009) and Himalayan leucogranite (representing sedimentary O isotopic compositions (Hopkinson et al., 2017; Figure 13b), indicating the incorporation of sediment into its source. Therefore, it is highly likely that the Shandan diorites originated from an enriched subcontinental lithospheric mantle source metasomatized by subducted-sediment-derived melts.
In addition, the zircon ages and Hf isotopic compositions of the Shandan diorites suggest two stages of magmatism with different sources (Figure 7a). The zircon grains from the first stage (430 Ma) yield initial εHf(t) values ranging from moderately positive (+0.14) to highly positive (+6.58), with model ages of 1,023–751 Ma, suggesting that they were derived predominantly from enriched mantle components with only a minor crustal contribution. The zircon grains from the second stage (403 Ma) yield negative εHf(t) values (2.24 to −11.0), with model ages of 1,271–927 Ma, suggesting that the magma was influenced primarily by the addition of Mesoproterozoic to Neoproterozoic crustal material and mixed with the enriched mantle components source (Zhang L. Q. et al., 2017). Therefore, the zircon Hf isotopic characteristics of the Shandan diorites with ages of 430–403 Ma indicates a decrease in the contribution of enriched mantle material and a greater incorporation of continental crustal material (Jahn et al., 1999). In conclusion, the trace element and isotopic data suggest that the Shandan diorites originated from the enriched subcontinental lithospheric mantle mixed with crustal material melts.
The trace element and isotopic data suggest that the Shandan diorites were formed by the partial melting of enriched subcontinental lithospheric mantle contaminated with a mixture of subduction-related sediment-derived melts and crustal material. We further discuss the nature of the contributions from sediment and the mafic lower crust. We used a two-endmember 87Sr/86Sr versus εNd(t) mixing model to quantitatively estimate the contribution of crustal material to the Shandan samples (Figure 10). We selected lower continental crust (LCC; Jahn et al., 1999) as the crustal endmember and depleted mantle (DM) as the mantle endmember (Workman and Hart, 2005; Zindler and Hart, 1986). The results indicate that the basaltic magma consists of ∼95%–94% DM-derived material and ∼5%–6% LCC magma.
We evaluated the contribution of sediment-derived melt using 143Nd/144Nd(t) versus Th/Nd ratios and the zircon Hf–O isotopic composition of the endmember of the two-component mixing model for the Shandan diorites (Figure 13). Th and Nd are not mobile in fluid released during the dehydration of subducted oceanic crust and sediment, but are mobile in sediment-derived melt (Class et al., 2000; Johnson and Plank, 2000; Plank and Langmuir, 1998); therefore, we calculated the range of Th/Nd ratios at a given 143Nd/144Nd value that would be produced by the mixing of global bulk subducted sediment (GLOSS; Plank and Langmuir, 1998) and partial melts of sediment with depleted mantle MORB (DMM; Figure 13a; Liu et al., 2014). The results show that mixing bulk GLOSS and DMM cannot produce the high Th/Nd ratios of the Shandan diorites (Figure 13a); however, <5% partial melting of GLOSS yielded the Th/Nd and 143Nd/144Nd(t) ratios of the Shandan diorites. A Hf–O isotopic mixing model using the Qinghu monzonite as the mantle endmember and Himalayan leucogranite as the sedimentary endmember also suggests that the source of the Shandan diorites contains 10%–20% sediment (Li et al., 2009; Figure 13b). Thus, the addition of 10%–50% sediment-derived partial melt to a DMM source can produce the parental magmas of the Shandan diorites.
5.2 Implication for the timing of slab breakoff
Orogenic processes in the region between the NQOB and Alxa Block generated intermediate to felsic magmas during various stages of convergence, including during the oceanic subduction, arc–continent collision, post-collision, and continental subduction stages (Song et al., 2014; Song et al., 2007; Zhang L. Q. et al., 2017). This magmatic activity provides important insights into the relationship between geodynamic processes and tectonic evolution, improving our understanding of the interactions between the asthenosphere, lithospheric mantle, and continental crust (Dewey, 1988). Previous studies on the intermediate to felsic magmatic rocks, including diorite and granite in the Longshoushan Belt on the southwestern margin of the Alxa Block, suggested a close association with collision between the Alxa and Qilian–Qaidam blocks and post-collisional extension resulting from the continued subduction of the early Paleozoic North Qilian oceanic crust (Fu et al., 2019; Kang et al., 2018; Yang X. Q. et al., 2018). During the Cambrian–Silurian, the North Qilian oceanic crust was subducted northward beneath the Alxa Block, leading to back-arc extension in the NQOB (Xia et al., 2012). The lithospheric mantle was extensively metasomatized by fluids and melts derived from the oceanic crust and sediments. This process resulted in the formation of early Paleozoic intermediate to felsic magmatic rocks in the oceanic crust and subcontinental lithospheric mantle beneath the Alxa Block, as observed in the North Qilian belt (Qian et al., 2001; Song et al., 2013; Xia et al., 2003). Therefore, we can review the tectonic evolution of the Longshoushan and Shandan areas by considering the early Paleozoic intermediate to felsic magmatic rocks from the North Qilian and Longshoushan regions.
Figure 14a compares the timing of Paleozoic magmatic activity in the North Qilian and Longshoushan regions. Previous studies of the intermediate to felsic magmatic rocks in the Longshoushan area of the Alxa Block focused mainly on the Jinchuan quartz syenite (433 Ma; Zeng et al., 2016) and the fine-grained Qingshanbao granite (430 Ma; Liu et al., 2019), and inferred that these rocks formed in a post-collisional intraplate extensional environment. The Dafusi alkali feldspar granite in the western segment of the Longshoushan Belt formed during the late Silurian (426 ± 2 Ma) in a post-collisional extensional environment, as did the Silurian Hexibao granite in the eastern segment of the Longshoushan Belt (Fang et al., 1997). Previous studies of the intermediate to felsic magmatic rocks in the NQOB examined the 516–505 Ma high-Al Chaidanuo granite (Chen et al., 2014), the 501 Ma Kekeqi quartz syenite, the 477 Ma Niuxinshan granite, and the 457–441 Ma adakitic granite (Tseng et al., 2009; Yu et al., 2015; Zhang L. Q. et al., 2017), which are associated with the formation of oceanic crust and subduction–accretion processes. During this period (516–441 Ma), magmatic rocks were generated through the partial melting of oceanic crust during the initial stages of northward subduction of the Qilian oceanic crust (Wu et al., 2011; Wu et al., 2010; Wu et al., 2004). Studies of the 430 Ma Laohushan granite, 427 Ma Laohushan diorite, 424 Ma Jinfosi S-type granite, and 427–414 Ma Wuwei‒Jinchang pluton (Chen et al., 2016; Tseng et al., 2009; Zhang L. Q. et al., 2017) suggest that the Alxa Block was in a syn-collisional or post-collisional setting along with the Central Qilian‒Qaidam Block duirng 435–414 Ma. Furthermore, younger post-orogenic granites (∼403–374 Ma) occur in the northern part of the NQOB (Song et al., 2013; Wu et al., 2010; Wu et al., 2004). Previous studies of the intermediate to felsic magmatic rocks in the Longshoushan and North Qilian areas suggest that the Shandan diorites (430–403 Ma) formed in a post-collisional environment associated with the final closure of the North Qilian Ocean and collision between the Alxa and Qilian blocks.
Figure 14
Figure 14. (a) Ages of Paleozoic magmatic rocks in the North Qilian and Longshoushan areas. Age data are listed in Supplementary Table S6; (b) Rb versus Y + Nb (after Pearce, 1996) and (c) Nb versus Y (after Eby, 1992) diagrams for the Shandan diorites. ORG: ocean ridge granitoid, syn-COLG: syn-collisional granitoid, VAG: volcanic arc granitoid, WPG: within-plate granitoid.
Magmatic activity during the post-collisional stage is associated with slab breakoff and lithospheric delamination. These processes lead to upwelling of the asthenosphere, providing a source of material and heat for post-collisional magmatic activity (Bird, 1979; Huw Davies and von Blanckenburg, 1995). The trace element contents (e.g., enriched LILEs, depleted HFSEs) and Sr–Nd–Pb–Hf–O isotopic compositions of the Shandan intrusions suggest that they formed through the partial melting of enriched subcontinental lithospheric mantle and the incorporation of crustal material and subduction-related sediment-derived melts. The tectonic setting of the Shandan intrusions can be constrained further using Rb versus Y + Nb and Y versus Nb discrimination diagrams (Pearce, 1996; Pearce and Peate, 1995; Figures 14b, c). In these diagrams, the Shandan diorites plot in the transitional zone between within-plate and island arc settings, as well as in the post-collision area, suggesting that they formed in post-collisional extension. These features align with slab breakoff models, where detachment of the subducted oceanic slab triggered asthenospheric upwelling, heating the overlying SCLM and facilitating partial melting (von Blanckenburg and Davies, 1995; van Hunen and Miller, 2015). Moreover, previous studies on the A-type granites magmatic activity in the Longshoushan Jinchuan regions suggest that asthenospheric upwelling was triggered by the post-collisional slab breakoff of the northern Qilian oceanic crust (433 Ma; Zeng et al., 2016). Therefore, we infer that the Shandan intrusions formed during post-collisional slab breakoff, which created a window for upwelling asthenospheric material, inducing partial melting of the subcontinental lithospheric mantle and crust. Zircon Hf isotopes further constrain the timing and duration of slab breakoff. The gradual decline in mean εHf(t) values from +6.85 at 430 Ma to +1.2 at 403 Ma (Figure 15) reflects waning mantle input, possibly due to the end of slab detachment and weaker asthenospheric upwelling leading to a gradual decrease in crust–mantle interaction. This isotopic trend correlates with the cessation of magmatic activity by ∼403 Ma, suggesting slab breakoff concluded by this time.
Figure 15
Figure 15. Tectonic model for the Shandan area between the middle Silurian and Early Devonian in the North Qilian Orogenic Belt and Alxa Block. (a) Slab break-off occurred around 430 Ma, creating a window for upwelling asthenospheric material; (b) Slab break-off was nearing end at 403 Ma, leading to weaker asthenospheric upwelling. SCLM, subcontinental lithospheric mantle.
In summary, subduction of the North Qilian oceanic crust led to the consumption of oceanic crust and eventual collision between the Alxa and Central Qilian blocks at ∼440 Ma (Song et al., 2014; Song et al., 2013; Xia et al., 2003). Due to differences in density, slab breakoff occurred around 430 Ma, creating a window for upwelling asthenospheric material and inducing the partial melting of subcontinental lithospheric mantle and crust. At ∼403 Ma, slab breakoff was nearing end, leading to weaker asthenospheric upwelling. This model is consistent with global examples, where slab break-off has driven short-lived (<30 million years) post-collisional magmatic activity (von Blanckenburg and Davies, 1995). Thus, the Shandan diorites serve as a chronometer for slab detachment in the NQOB, constraining its onset to approximately 430 Ma and cessation by around 403 Ma.
6 Conclusion
We studied the petrology, geochronology, whole–rock geochemistry, Sr–Nd–Pb isotopic compositions, and zircon Hf–O isotopic compositions of the Shandan diorites in the Longshoushan area, allowing us to draw the following conclusions. The Shandan diorites consist mainly of middle Silurian (430 Ma) quartz diorites and Early Devonian (403 Ma) diorite. The intermediate εNd(t), zircon εHf(t), and low δ18O values (5.75‰–6.38‰), along with radiogenic Sr isotopic signatures, suggest derivation from partial melting of enriched subcontinental lithospheric mantle with contributions from subduction-related components. These rocks formed in association with slab breakoff at ∼430 Ma, which created a window for upwelling asthenospheric material and induced the partial melting of subcontinental lithospheric mantle and crust. At ∼403 Ma, slab breakoff was nearing its end, leading to weaker asthenospheric upwelling.
Data availability statement
The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding authors.
Author contributions
GC: Data curation, Methodology, Software, Writing–original draft. DL: Data curation, Formal Analysis, Investigation, Software, Supervision, Writing–original draft. XJL: Conceptualization, Methodology, Resources, Software, Supervision, Writing–original draft, Writing–review and editing. PL: Data curation, Formal Analysis, Methodology, Software, Validation, Writing–review and editing. ZB: Data curation, Formal Analysis, Software, Writing–review and editing. XL: Formal Analysis, Methodology, Writing–review and editing. RH: Investigation, Methodology, Writing–review and editing. HT: Data curation, Formal Analysis, Methodology, Writing–review and editing. YL: Formal Analysis, Methodology, Software, Writing–review and editing. WH: Data curation, Formal Analysis, Software, Visualization, Writing–review and editing. YX: Data curation, Formal Analysis, Writing–review and editing.
Funding
The author(s) declare that financial support was received for the research and/or publication of this article. This study was supported financially by funds from the National Natural Science Foundation of China (No. 92055208, 42473063, 42203051), Deep Earth National Science and Technology Key Project (2024ZD1001503) and the Natural Science Foundation of Guangxi Province for Young Scholars (No. GuikeAD23026175, 2022GXNSFBA035538). This research is a contribution to “Xinjiang Tianchi Distinguished Expert” by Xi-Jun Liu.
Conflict of interest
The 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.
Generative AI statement
The author(s) declare that no Generative AI was used in the creation of this manuscript.
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Supplementary material
The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/feart.2025.1562893/full#supplementary-material
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Keywords: slab breakoff, Sr-Nd-Pb isotopic compositions, zircon Hf-O isotopic compositions, Shandan diorites, Longshoushan area
Citation: Chen G, Li D, Liu X, Liu P, Bai Z, Liu X, Hu R, Tian H, Liu Y, Huang W and Xiao Y (2025) Petrogenesis of Middle Silurian Shandan diorites in North Qilian Orogenic Belt, NW China: Insights into post-collisional slab breakoff. Front. Earth Sci. 13:1562893. doi: 10.3389/feart.2025.1562893
Received: 18 January 2025; Accepted: 26 February 2025;
Published: 19 March 2025.
Edited by:
Zhongliang Wang, China University of Geosciences, ChinaReviewed by:
Liang Qiu, China University of Geosciences, ChinaDapeng Li, China University of Geosciences, China
Copyright © 2025 Chen, Li, Liu, Liu, Bai, Liu, Hu, Tian, Liu, Huang and Xiao. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Dechao Li, MTc1MTQ4MzYxQHFxLmNvbQ==; Xijun Liu, eGlqdW5saXVAZ2x1dC5lZHUuY24=