Petrogenesis and tectonic implications of Early Paleozoic granitoids in the Baoshan deposit, Guangxi, South China

The Early Paleozoic tectonic setting and geological processes of the South China Block have long been a subject of debate. This study presented zircon U-Pb geochronology and Hf isotope, and whole-rock geochemical analyses for the Early Paleozoic granitoids in the Baoshan deposit of the Dayaoshan Uplift. LA–ICP–MS zircon U ‒ Pb results suggest that the diorites, granite porphyries, granodiorites and its mafic microgranular enclaves in the Baoshan deposit formed at 449–430 Ma. Their formation ages are consistent with those of granite, MMEs and mafic rocks found in the Dayaoshan region. The granite porphyries, granodiorites, diorites and their MMEs in the Baoshan deposit have high Eu/Eu*ratios, low Zr + Nb + Y + Ce contents, 10,000×Ga/Al values, and A/CNK ratios (0.74–1.08), belonging to metaluminous to weakly peraluminous calc-alkaline I-type granitoids. Based on zircon Hf isotopic compositions ( ε Hf (t) from −5.5 to +3.1), it is unlikely that these rocks were solely originated from a crustal source, and mantle-derived magma also played a significant role in the formation of these intrusive rocks. It is inferred that the granitoids in the Baoshan deposit were probably formed through the underplating of mantle-derived magmas during a transitional collision to extension tectonic setting, which led to the remelting of Mesoproterozoic crust.


Introduction
The Dayaoshan Uplift in the eastern Guangxi Zhuang Autonomous Region is a significant component of the southwest segment of the Qin-Hang metallogenic belt in the South China Block (SCB; Figure 1A) (Faure et al., 2009;Yang et al., 2009;Ma et al., 2024).This region exhibits intense magmatic and tectonic activities, along with a broad distribution of intermediate-acidic magmatic rocks and associated W-Mo-Cu-Au-Ag-Pb-Zn deposits (Chen et al., 2011;Hu et al., 2012;Li et al., 2014;Liu et al., 2023).Recent high-precision geochronological investigations have shown that the majority of granitic plutons in this area were emplaced during the Early Paleozoic , Late Paleozoic to Early Mesozoic Lyu et al. 10.3389/feart.2024.1444751 (270-240 Ma), and Late Mesozoic (170-150 and 110-90 Ma) periods.Among these, mineralization associated with intermediate-acidic granitoids primarily occurred during the Early Paleozoic and Late Mesozoic periods (Wu et al., 2015;Ye et al., 2015;Jiang et al., 2017;Lyu et al., 2020;Ma et al., 2024).Nevertheless, the Early Paleozoic granitoids have received less attention in comparison to Late Mesozoic granitoids (Zhou, 2003;Guo and Liu, 2021;Ma et al., 2024).Furthermore, existing research has predominantly concentrated on Early Paleozoic S-type granitoids (Wang et al., 2007;Wang et al., 2011;Song et al., 2015), with limited emphasis on Early Paleozoic I-type granitoids.The Early Paleozoic tectonic setting of the SCB remains debated, and previous studies focused on the sedimentary provenance (Lyu et al., 2020;Gan et al., 2023).Therefore, further investigation about the Early Paleozoic intrusive rocks in this region, particularly I-type granitoids, is essential for a comprehensive understanding of the Early Paleozoic geological processes in the SCB.
The Baoshan deposit, a newly discovered copper deposit, is located in the south-central Dayaoshan Uplift (Qiu, 2021).While much research has been done on the Late Mesozoic granitoids (Bi et al., 2015;Zhang et al., 2018;Huang et al., 2019), there have been few studies on the petrogenesis and tectonic implications of Early Paleozoic intrusive rocks in the Baoshan deposit.Some of these intrusive rocks, particularly granodioritic rocks, contain abundant MMEs.These MMEs are usually considered to be indicative of magma mixing and commonly found in calc-alkaline granitic rocks (Didier and Barbarin, 1991;Cheng et al., 2009;Liu Y. et al., 2010;Chen et al., 2018).MMEs can provide important information about magma sources, petrogenetic histories, and deep magmatic processes of granitic rocks (Barbarin, 2005;Yang et al., 2007).Magmatic mixing involves significant material exchange, which can offer insights into the geochemical information of the magma source.Petrology and zircon Hf isotope evidence is often well-preserved during magma evolution and can be used to assess the occurrence of magma mixing (Janoušek et al., 2004;Hawkesworth and Kemp, 2006;Guan et al., 2016).Thus, systematic zircon geochronology and Hf isotope, and whole-rock geochemistry analyses in this study were conducted on the Early Paleozoic intrusive rocks and MMEs in the Baoshan deposit to constrain their petrogenesis and tectonic setting.The new zircon U-Pb geochronology and Hf isotopic data and whole-rock geochemical compositions help determine the timing and origin of the Early Paleozoic magmatism (Liu et al., 2024).Based on these results, this study aims to explore the characteristics of tectonomagmatic activity and tectonic setting during the Early Paleozoic era in the SCB.

Geological setting
Since the Late Proterozoic, the Dayaoshan Uplift has experienced multiple periods of tectonic evolution, such as the Caledonian, Hercynian, Indosinian and Yanshanian movements (Shu et al., 2023;Tang et al., 2023).These multiple tectonic movements have formed a series of regional faults in the study area, accompanied by magma emplacement and hydrothermal activities, and forming a polymetallic mineralization belt dominated by gold, silver, tungsten, molybdenum, and other minerals (Mao et al., 2013;Mao et al., 2021).The Dayaoshan Uplift has a central uplift area and a surrounding fault basin, with a total area of nearly 18,000 km 2 (Figure 1B).It is a region with a weakly metamorphosed basement primarily made up of Cambrian and minor Sinian strata.Both the Cambrian and Sinian sedimentary rocks are mainly flysch deposits with a total thickness of >9000 m, consisting of sandstone, siltstone, phyllite, and carbonaceous shale (Jiang et al., 2017).The main structures in the region include the E-W-trending Dayaoshan anticlinorium and the NE-striking Pingxiang-Dali deep fault superimposed by late N-E-, N-W-and S-N-trending structures, forming a gridded ore-controlling structure (Chen et al., 2011).
The Baoshan deposit is a part of the southwestern Shedong W-Mo ore district in Cangwu County.Neritic flyschoid outcrops in the ore district are represented by the lower Cambrian Huangdongkou Formation.This formation is composed of finegrained sandstone and siltstone with interbedded shale and carbonaceous shale.The ore district is located at the eastern Pingxiang-Dali deep fault, with the faults in the NW direction.The NW-trending normal fault with an attitude of 215°∠80°is most closely related to diagenesis and mineralization.This fault cuts the main granodiorites body and controls the attitude of the concealed quartz porphyry body.The width of the fault is 2-10 m, extending nearly 1 km, with strong silicification (or quartz veining), pyritization, fluoritization and other alteration and mineralization, forming the ore-controlling structure of the Baoshan deposit (Jiang et al., 2015).
The Baoshan pluton intruded into Cambrian strata and consists of granodiorites and granite porphyries.The pluton extends in a NW direction with 3 km in length and 1 km in width.The granodiorites contain abundant MMEs, quartz-vein-type scheelite and galena mineralization, and a small amount of molybdenite mineralization (Jiang et al., 2017).The granite porphyries have an intrusive contact with the granodiorites (Figure 1C).The Baoshan deposit is small in size, with Cu concentrations of 0.2%-3.1%,Pb concentrations of 1.1%-4.9%and Zn concentrations of 0.8%-4.1% (Huang et al., 2019).

Sample descriptions
The granite porphyry samples were collected from borehole ZK28003, granodiorite samples from boreholes ZK28805 and ZK28003, diorite dyke samples from borehole ZK1108, and MMEs samples from boreholes ZK28805 and ZK1108 in the Baoshan deposit.
The granite porphyry samples are greyish white in color and show a porphyritic texture (Figure 2J-I).The phenocrysts are composed of plagioclase (∼30%), K-feldspar (40%), quartz (∼30%), and the fine-grained microcrystalline matrix have similar mineralogy associations.Plagioclase crystals are granular or short-prismatic in shape, ranging from 1.0 to 2.0 mm in size, and some of them have undergone strong sericitization.K-feldspar crystals are tabular and 2.0-3.5 mm in size.Quartz crystals are granular and 1.0-2.0mm in size, and biotites are 1.0-2.0mm in size.
Many MMEs are visible in the granodiorite samples.The MMEs are black, irregular, elliptical or lenticular in shape, 5-20 cm in length (up to 50 cm).They typically display sharp contacts with their host rocks and have weak chilled margins (Figures 2A-C).The MMEs are dominated by hornblende (40%), biotite (∼27%), plagioclase (20%), and quartz (∼10%), with subordinate accessory minerals (e.g., apatite and zircon).In comparison to the host granodiorites, MMEs are obviously enriched in dark mafic minerals, such as hornblende and biotite.Lyu et al. 10.3389/feart.2024.14447513.2 Zircon U-Pb dating geochronology and Lu-Hf isotope analyses Zircons were separated using heavy liquid and magnetic techniques and then purified by hand picking under a binocular microscope.Sample grains were selected randomly, mounted in epoxy, and polished for further analysis.The internal structures of the zircons were examined using cathodoluminescence (CL) imaging prior to isotopic analysis.
Zircon U-Pb dating and in situ trace element analyses were simultaneously performed with an Agilent 7500a inductively coupled plasma-mass spectrometry (ICP-MS) instrument coupled with a Resonetics Resolution M-50 (193 nm ArF excimer) laser ablation (LA) system at the State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (GIGCAS).Sample mounts were placed in a specially designed double volume sample cell flushed with Ar and He.The laser beam was set to 30 μm, 2 J•cm −2 and 5 Hz for the diameter, energy density and repetition rate, respectively.The ablated material was carried by He-Ar gas via a Squid system to homogenize the signal into the ICP-MS instrument.Each analysis incorporated a background acquisition time of approximately 20-30 s (gas blank) followed by 50 s of data acquisition during ablation.Detailed analytical procedures followed those described by Liu Y. S. et al. (2010).Off-line selection and integration of background and analyzed signals and time-drift correction and quantitative calibration for trace element analyses and U-Pb dating were performed using the in-house program ICPMSDataCal 8.3 (Liu Y. S. et al., 2010).Zircon 91,500 was used as an external standard, and zircon GJ-1 was used as an internal standard for U-Pb dating.Timedependent drift of U-Th-Pb isotopic ratios was corrected using linear interpolation every five analyses and was monitored using variations in zircon 91,500.The obtained mean 206 Pb/ 238 U ages of 91,500 and GJ-1 are within experimental error of their recommended values (Jackson et al., 2004).The absolute abundances of U, Th and rare earth elements (REEs) were determined using an external standard glass NIST SRM 610, and 29 Si was used as the internal standard.Concordia diagrams and weighted mean calculations were made using Isoplot (V.3.0) (Ludwing, 2003).
In situ zircon Lu-Hf isotopic analyses were carried out with a Neptune Plus multicollector (MC)-ICP-MS equipped with an ArF excimer laser ablation system at the State Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences, Wuhan.Zircons were ablated with a laser beam with a diameter of 44 μm, laser repetition rate of 10 Hz, and laser energy of 15 J•cm −2 .The aerosol was carried by He gas to the MC-ICP-MS system.Based on an exponential law, instrumental mass bias corrections of Yb and Hf isotope ratios were performed by normalizing 172 Yb/ 173 Yb by 0.7325 and 179 Hf/ 177 Hf by 0.7325 (Patchett et al., 1982;Huang and Wang, 2019), respectively.Two reference standards were also analyzed during the Hf isotopic analyses: the 91,500 zircon and Penglai zircon.Raw data for Hf isotopic analyses were reduced using software ICPMSDataCal (Liu Y. S. et al., 2010) and the results are reported with 1σ error.

Whole-rock major and trace element analyses
For major and trace element analyses, the fresh whole-rock chips were cleaned and crushed to 200 mesh in an agate mill.The loss on ignition (LOI) was determined after heating the samples to 1,000 C for 3 h.Major element contents were measured by X-ray fluorescence (XRF) spectrometry on fused glass beads using a Rigaku 100e spectrometer at the ALS Laboratory group.The precision for major elements was better than 1%.Details of the XRF procedures are described by Li et al. (2005).The trace element contents were measured by a Finnigan MAT ELEMENT magnetic sector ICP-MS with precision better than 10% at the ALS Laboratory group.The details of the analytical procedure are outlined in Qi et al. (2000).International standard AMH-1 (Mount Hood andesite) (Thompson et al., 1999) was used as the standard for quality control.
Zircon grains from MMEs (sample ZK28805-6) are mostly long-prismatic or granular and darker than the zircon grains in host granodiorites.These zircons are 50-250 μm in length and have length-to-width ratios of 1:1-5:1.The zircon grains show obvious magmatic oscillatory zoning.The analytical results show that REEs exhibit listric-shaped LREE-enriched patterns, without obvious negative Eu anomalies (av. of 0.91) and high Th/U ratios (0.73-1.66), indicating that limited plagioclase fractionation occurred in the Frontiers in Earth Science 05 frontiersin.orgmelt and that these zircons are also typical magmatic zircons.After excluding discordant and inherited ages, 20 grains plot on or near a U-Pb concordia line, yielding a weighted mean 206 Pb/ 238 U age of 449.2 ± 6.3 Ma (MSWD = 0.29) (Figures 3A, E), which is interpreted to be the formation age of the MMEs.This age is in close proximity to the age of host granodiorites.

Whole-rock geochemistry
Geochemical data for granite porphyries, granodiorites, diorites and MMEs from the Baoshan deposit are listed in Table 1.In general, high field strength elements, rare earth elements and transition elements are stable during intense hydrothermal alteration, and Mg in intermediate-acidic igneous rock is also stable due to the lack of olivine and pyroxene.Ti, P, Al, Fe, Mn and other major elements are not easily affected by hydrothermal activity, while Ca, Na, K and some large ion lithophile elements (such as Sr, Ba, and Rb) are very unstable, and the obtained data may not accurately reflect the geochemical characteristics of rocks.Therefore, before interpreting the data, the impact of alteration should be fully considered to eliminate "distorted" data.All samples in this article have low LOI values (1.16%-2.18%),and there is no significant linear relationship between the contents of TiO 2 , Al 2 O 3 , Fe 2 O 3 T , MnO, MgO, CaO and LOI, suggesting slight effects of alteration on the studied samples.This is further supported by their subparallel REE and multi-element patterns (Figure 6).After deducting the LOI, the granodiorites have moderate SiO 2 (65.12%-67.75%),Al 2 O 3 (14.90%-16.00%),Fe 2 O 3 T (4.72%-5.63%), MgO (1.89%-2.37%),and CaO (4.34%-4.73%)contents.These rocks exhibit high Mg # values (38.7-59.0)and relatively low alkali contents.On a SiO 2 vs Na 2 O + K 2 O (TAS) diagram, data for the samples plot mainly in the quartz diorite and granodiorite fields (Figure 4A).When compared to the granodiorites, the granite porphyries have higher SiO 2 contents (75.21%) and lower Fe 2 O 3 T (1.20%), MgO (0.32%), and CaO (0.83%) contents, falling into the granite field (Figure 4A).When compared to the granodiorites and granite porphyries, the diorites havelower SiO 2 contents (59.06%) and higher Fe 2 O 3 T (8.01%), MgO (3.41%), and CaO (6.67%) contents.On a TAS diagram, data for the sample plot mainly in the diorite field (Figure 4A).On a SiO 2 vs K 2 O diagram, the granite porphyries, granodiorites and diorites are classified as high-K calc-alkaline-shoshonite series, high-K calc-alkaline series and intermediate-K calc-alkaline series, respectively (Figure 4B).In an A/CNK vs A/NK diagram, the granodiorite and diorite samples plot mostly in the subalkaline-metaluminous field, whereas the granite porphyries plot in the weakly peraluminous field (Figure 4C).6A).In primitive mantle-normalized trace element patterns, many MMEs show characteristics similar to both the granodiorites and diorites, exhibiting enrichment of largeion lithophile elements (e.g., Rb and K) and depletion of high-fieldstrength elements (e.g., Nb, Ta, and Ti).However, other MMEs have similar patterns to those of the granite porphyries, exhibiting no negative Ta anomalies (Figure 6B).The Sc, Cr, Ni, V, and Co concentrations of the MMEs are the highest, followed by the granodiorites and diorites, and those of the granite porphyries are the lowest.Rb/Nb ratios of the granite porphyries, granodiorites, diorites and MMEs (31.74,10.12,magmatic granite (0.05), while the Rb/Sr ratio of granite porphyries (2.56) is higher than that of crust-derived magmatic granite (0.5) (Sylvester, 1998).The Nb/Ta ratios of the granodiorites, diorites and MMEs (9.05-12.44, 13.11, and 9.75-14.81, respectively) are intermediate between the continental crust (8.30) and primitive mantle (17.50), while the Nb/Ta ratio of the granite porphyries (4.96) are lower than the value for continental crust (Sun and McDonough, 1989).The Mg # value of granodiorites, diorites and 49.80,.00,respectively) are higher than the value of crust-derived granite (<40) (Atherton and Petford, 1993), while the Mg # value of granite porphyries (38.7) are lower than the value of crust-derived granite.

Hf isotopes
The samples have low zircon 176 Lu/ 177 Hf ratios (less than 0.002), indicating little accumulation of radiogenic Hf after zircon formation (Wu et al., 2007a).The zircon εHf(t) values of the granite porphyries, granodiorites, diorites and MMEs range from −3.2 to −0.3, from −2.9 to −0.6, from −5.5 to +3.1, and from −2.3 to +0.6, respectively (Figure 7A).Such variations are much larger than analytical uncertainties, indicating that these samples have heterogeneous zircon Hf isotopic compositions.Correspondingly, the two-stage Hf isotope model ages of the samples primarily range from 1.1 Ga to 1.6 Ga (Figure 7B, Supplementary Table S2).

I-type granitoids in the Baoshan deposit
According to the magma source and tectonic setting, the granites can be divided into four types: M-, A-, S-, and I-type granites (Whalen et al., 1987;Chappell, 1999).M-type granite, also known as mantle-derived granite, is formed by fractional crystallization from a tholeiitic magma series (Wu et al., 2007b).The granite porphyries, granodiorites and their MMEs are part of the calc-alkaline magma series (Figures 4A, B), and most of zircon ε Hf (t) values are negative (Figure 7), indicating that they are mainly derived from crust rather than mantle.The zircon Ti temperatures of granite porphyries, granodiorites and their MMEs are of 671°C-775°C (av. of 726 C), 683°C-751°C (av. of 716°C) and 648°C-708°C (av. of 679°C), indicating a low formation temperature (Ferry and Watson, 2007).This is not consistent with the A-type granite formed in a hightemperature and low-pressure environment.The typical A-type granites have important mineralogical and geochemical signatures, such as alkaline dark minerals, high 10,000×Ga/Al (>2.6), and high Zr + Nb + Ce + Y (>350 ppm) (Whalen et al., 1987).The granodiorites and granite porphyries have low 10,000×Ga/Al (1.6-2.0)ratios and low Zr + Nb + Ce + Y (117-211 ppm) contents without any alkaline dark minerals found under the microscope, further supporting that the granodiorites and granite porphyries are not A-type granites (Figures 8A, B).
S-type granite is mainly a product of partial melting of crustal sedimentary rocks.The typical S-type granite is strongly peraluminous, and show an A/CNK value (>1.1) and a significant Eu anomaly (Miller, 1985).The A/CNK values (0.74-1.08) of granite porphyries, granodiorites and their MMEs are less than 1.1, which plot in the metaluminous to weakly peraluminous area (Figure 4C).Their Eu anomalies are not obvious (0.60-0.83), indicating that the granite porphyries, granodiorites and their MMEs are not Stype granitoids.I-type granite is mainly the product of partial Frontiers in Earth Science 09 frontiersin.org(A-H) Harker diagrams for intrusive rocks in the Baoshan deposit.Symbols are the same as in Figure 4B.
melting of crustal igneous rocks.The characteristic minerals of Itype granite are hornblende and pyroxene, with an A/CNK value less than 1.1.Components like biotite and hornblende are commonly found in the granite porphyries, granodiorites and their MMEs (Figure 2), showing an I-type granite affinity (Chappell and White, 1974).On the diagrams of FeO t /MgO-Zr + Nb + Ce + Y and 10,000×Ga/Al-Zr + Nb + Ce + Y (Figures 8A, B), granite porphyries and granodiorites are situated within the undifferentiated I-, S-, and M-type granitoids.On the SiO 2 versus P 2 O 5 diagram (Figure 5H), the samples show evolutionary trends typical of I-type granitoids (Wang et al., 2022).The samples in this study contain hornblende (Figure 2).Thus, the granite porphyries, granodiorites and its associated MMEs from the Baoshan deposit belong to I-type granitoids.

Petrogenesis of the intrusive rocks and mantle-derived contribution
The genesis of calc-alkaline I-type granites has been attributed to the following mechanisms: 1) partial melting of residual basaltic oceanic crust and sediment (Castro et al., 2010;Huang et al., 2014;Zhang Y. et al., 2016;Shao et al., 2017); 2) assimilation-fractional crystallization and contamination (AFC) of mantle-derived basaltic Chondrite-normalized REE (A) and primitive-mantle-normalized trace element patterns (B) for intrusive rocks in the Baoshan deposit.Normalizing values for chondrite and primitive mantle are from Sun and McDonough (1989).Symbols are the same as in Figure 4B.Age versus εHf (t) diagram of zircons in intrusive rocks in the Baoshan deposit (Nowell et al., 1998;Vervoort and Blichert-Toft, 1999).Symbols are the same as in Figure 4B.
For granitic rocks, if the Hf isotope model age is similar to its formation age, then its source is juvenile crust (Ferry and Watson, 2007).The zircon ε Hf (t) values of granite porphyries, diorites, granodiorites and MMEs (∼450-430 Ma) mainly range from −5.5 to + 3.1, and the corresponding T DM2 ages range from 1.1 Ga to 1.6 Ga, indicating that the intrusive rocks in the Baoshan deposit mainly originated from partial melting of Mesoproterozoic crust.In addition, the zircon ( 176 Hf/ 177 Hf) i values (0.28182-0.28258)are lower than those of chondrites (0.28277), also indicating that their diagenetic materials mainly originated from the crust.
The granite porphyry samples fall in the field of the partial melt of metagreywacke or metapelite (Figures 9A, C), whereas the diorites, granodiorites, and their MMEs are plotted in the partial melt extending from metabasalt to metatonalite (Figures 9A, C).This distinction suggests that granite porphyries and other rocks may have undergone partial melting in varying source materials.
They exhibit lower Al 2 O 3 /TiO 2 , Rb/Sr and Rb/Ba ratios but higher CaO/Na 2 O ratio compared to the typical metapelite derived melt (Figures 9B, D).Such signatures indicate variations in the compositions and origins of these rocks, and such compositions could not solely originate from crustal-derived sources.Instead, an evident transitional trend between pelite and basalt-derived melts reveals the input of mantle-derived materials cannot be precluded in the genesis of the I-type granites.
The samples show an obvious magmatic mingling trend in the MgO-FeO T diagram (Figure 10A).The minerals in MMEs are euhedral-subhedral and much smaller than those in the host granodiorites (Figure 2).The zircon Eu anomalies of MMEs are much weaker than those of the host granodiorites.MMEs and their host granodiorites have a clear boundary and present a dark grey condensation edge (Figure 2F), further indicating that they formed through the mixing of magmas derived from different sources (Nitoi et al., 2002;Perugini et al., 2003).In contrast, there is no obvious fractional crystallization trend in the Sr-Eu/Eu * , 10,000 * Ga/Al-Rb/Sr and Rb-Ba diagrams, indicating that fractional crystallization had little effect on magma genesis (Figures 10B-D).In addition, the zircon εHf(t) values of the samples show a large variation (2-24 ε units), and the range of the ( 176 Hf/ 177 Hf) i values is also relatively large.Considering that zircon Hf isotopes cannot be altered by fractional crystallization or partial melting, such zircon Hf isotope variations have been interpreted to result from magma mingling between mantleand crust-derived magmas (Bolhar et al., 2008;Zhu et al., 2009;Ji et al., 2018).
2017a) and mafic rocks (Nong et al., 2017b) in the Dayaoshan region, it is confirmed that the tectonic environment of this area may have been collision to extension transition during the Early Paleozoic.In addition, the existence of Early Paleozoic high-Mg basalts in northern Guangdong Province (ca.442-435 Ma) (Wang et al., 2013), the lamprophyre found near the Daning pluton in northeastern Guangxi (ca.440 Ma) (Yao et al., 2012;Jia et al., 2017), and the dacites found in northern Guangdong Province (ca.450 Ma) (Yi et al., 2014) indicates that the transition from collision to extension was likely postponed to at least 450-435 Ma.  (Hanson and Sun, 1976;Ewart and Griffin, 1994).Symbols are the same as in Figure 4B.The granite porphyries, diorites, granodiorites and their MMEs in the Baoshan deposit were formed at 450-430 Ma.Therefore, these rocks in the study area were formed in the local extension-thinning environment of the lithosphere following the intra-continental collision orogeny.The geochemical characteristics of the diorites, granodiorites, and their MMEs are similar to those in the Daning, Gulong, and Dacun plutons of northeastern Guangxi (438-435 Ma) (Li et al., 2006;Nong et al., 2017a;Liu et al., 2020) and the Longxin, Liandong, and Xiaying plutons of southeastern Guangxi (447-434 Ma) (Liu et al., 2021;Zhou et al., 2023), indicating a crust-mantle mixing origin.These previous studies also confirmed that mingling of magmas derived from the crust and mantle played an important role in the formation of Early Paleozoic granitoids in the SCB.These I-type granitoids with these petrogenetic characteristics are consistent with an origin in an extensional setting.On tectonic discrimination diagrams (Figure 11), our studied samples and previously-published data plot within the volcanic arc granites and the post-collisional extensional granites field.The zircon Hf isotope results indicate that the mantle components are indeed involved in the formation of granites, and underplating may be a geological process that is closely related to the genesis of granite (Petford and Gallagher, 2001;Annen and Sparks, 2002).Based on this result, combined with the above discussion, we propose that the granite porphyries, diorites, granodiorites and its MMEs in the Baoshan deposit were probably produced by the remelting of Mesoproterozoic crust as a result of underplating of mantlederived magma, and magma mingling occurred during the tectonic transition from collision to extension in the Early Paleozoic.The mantle-derived magmas played an important role in the formation of the Early Paleozoic intrusive rocks and MMEs via their heat and material input.
(3) The granite porphyries, diorites, granodiorites, and their associated MMEs were mainly derived from partial melting of Mesoproterozoic crust with the input of few mantle-derived materials, in response to a transition from a collisional tectonic setting to an extensional environment.

FIGURE 7
FIGURE 7 FIGURE 8 (A) Zr + Nb + Ce + Y versus FeO t /MgO and (B) Zr + Nb + Ce + Y versus 10,000 * Ga/Al (Whalen et al., 1987) diagrams for intrusive rocks in the Baoshan deposit.OGT-field for I-, S-, and M-type granitoids; FG-field for fractionated I-type granitoids.Symbols are the same as in Figure 4B.

TABLE 1
Major elements (wt%) and trace elements (ppm) analytical results for the intrusive rocks in the Baoshan deposit.
and SiO 2 in the early Paleozoic intrusive rocks in the Baoshan deposit are negative, while the correlations between Na 2 O and SiO 2 are positive (Figures5A-H).The total rare earth element (REE) contents of granite porphyries, granodiorites, diorites and MMEs from the Baoshan

TABLE 1 (
(Sun and McDonough, 1989) (wt%) and trace elements (ppm) analytical results for the intrusive rocks in the Baoshan deposit.=EuN /(Sm N × Gd N ) 0.5 .whereNrepresents normalization value after(Sun and McDonough, 1989)."t" means "in total", assuming that total Fe in rocks appear as Fe 2 O 3 .