Zircon U–Pb Ages and Geochemistry of Granite Porphyries in the Yangla Cu Deposit, SW China: Constraints on Petrogenesis and Tectonic Evolution of the Jinshajiang Suture Belt

Located in the eastern part of the Tethyan tectonic domain, the Jinshajiang Suture Belt (JSB), northwestern Yunnan, China, is notable for its large-scale distribution of Jurassic to Triassic granitoids that are genetically related to the evolution of the PaleoTethys Ocean and polymetallic mineralization. In this study, geochronological and geochemical analyses were conducted on three samples of these granite porphyries (GPs) using laser ablation inductively coupled plasma mass spectrometry and zircon U–Pb aging to reveal ages of 213 ± 15, 198:4 ± 8:6, and 195:3 ± 6:4Ma, respectively. These ages are younger than the emplacement ages of the granodiorites, at 208–239Ma, suggesting that magmatic activities in the Yangla mining district likely continued for ~44Ma. These GPs are rich in large-ion lithophile elements such as Rb, Ba, Th, U, K, and La but are deficient in high field strength elements such as Ta, Nb, Ce, Zr, Hf, and Ti. Significant Pb enrichment and P depletion were noted, as were varying degrees of metallogenic element enrichment in the order of Cu > Pb > Zn. The total content of rare earth elements (ΣREEs) of the GPs is in the range of 50.41–127.27 ppm and the LREE/HREE ratio is in the rage of 4.46–10.54. The GPs are rich in LREEs, with a high degree of differentiation noted between the LREEs and HREEs. The δEu (EuN/Eu∗) and δCe (CeN/Ce∗) values, at 0.53–0.86 and 0.79–0.98, indicate weak and slightly weak negative anomalies, respectively. The geochemical characteristics of the GPs indicate that these bodies are slightly metaluminous to peraluminous S-type granites in a calc–alkaline series that formed in a late-collisional or postcollisional tectonic setting. Three-component mixing of magmas including those of upper crust, lower crust, and mantle materials in addition to subsequent partial melting could have been responsible for the generation of these GPs in an epithermal low-pressure setting at <5 kbar.


Introduction
The Sanjiang Metallogenic Belt (SMB), including the Jinshajiang, Lancangjiang, and Nujiang rivers, is an economic skarn-porphyry Cu polymetallic metallogenic belt situated in SW China (Figures 1(a) and 1(b)). The metallogenic processes in the SMB occurred mainly during a Mesozoic (~230 Ma) late-collisional or postcollisional tectonic setting [1][2][3]. This belt consists mainly of seven geotectonic units including the Ganzi-Litang Suture Belt, Zhongzan-Zhongdian Plates, Jinshajiang Suture Belt (JSB), Qamdo-Simao Terranes, Nujiang Suture Belt, Lancangjiang Suture Belt, and Lhasa Terranes from east to west [2,4]. The SMB includes widespread ore-related granites, including Indosinian (Triassic to Late Jurassic) granitoids in large proportions [2][3][4]. Granitic porphyries (GPs) closely associated with Cu mineralization were discovered in 2014 by geological prospectors of the Yunnan Copper Industry Group in a tunnel at depths of 3250 m and 3275 m. The locations of these GPs suggest the potential contribution of porphyry plutons to the Cu deposits at depth. However, the ore-related GPs in the deep part of the Yangla mining district have received little research attention. Previous studies have shown that the JSB and its surrounding district contain the Sanjiang region's most important Cu-Pb-Zn-Au metallogenic belt, which is genetically associated with host granite plutons [1-3, 5, 6]. Therefore, obtaining accurate constraints on the nature and age of these ore-related GPs has a particular significance for our understanding of the tectonic evolution and metallogeny of the JSB.
The JSB is situated in the eastern Sanjiang domain and likely connects with the Ailaoshan Suture to the southeast, which underwent a complex evolution process from the late Paleozoic to the Neogene involving subduction of the Jinshajiang Ocean, arc-continent collision, post-collisional processes, and strike-slip faulting [15,16]. Published U-Pb zircon ages of igneous rocks in this area indicate that the Jinshajiang Ocean likely formed during the early Carboniferous (343.5-347 Ma [17,18]) with westward-directed subduction occurring beneath the Qamdo-Simao Terrane in the Early Permian (285 Ma [17,19]). Subsequently, the Jinshajiang Ocean gradually closed and ultimately disappeared. The earliest phases of collision produced high-silica rhyolites of Early Triassic age (247-246 Ma [20]). At the same time, the subduction and closure of the Jinshajiang Ocean resulted in partial melting of the lower crust, which formed large amounts of intermediate-to-evolved magma and resulted in large-scale volcanic and magmatic activity. These events, represented by high-K calc-alkaline granitoids 234-214 Ma in age, suggest that the Late Triassic was a period of early tectonic collapse and thermal relaxation in a postcollisional setting [2][3][4]15]. Associated felsic intrusive activity and metal mineralization have been identified in this region. The Triassic granitoids are represented by the Baimaxueshan (~248 Ma [21]), Ludian (234-214 Ma [21]), and Jiaren (~230 Ma [4]) intrusions, which formed possibly  [52]). 3 Geofluids after the closure of the Jinshajiang Ocean in a postcollisional tectonic setting [4,15]. Secondary ion mass spectrometry (SIMS) zircon U-Pb analysis has indicated an age of 230 Ma for the Jiaren intrusions, which are located south of the Yangla ore district in an area of~150 km 2 [2,4].
Accordingly, the YCD is suggested to have a genetic association with the Jiaren intrusion in the JSB [2][3][4].

Geofluids
The structure in the Yangla mining district is well developed and includes folds and faults. The Jinshajiang Fault is a regional-scale thrust fault that dips to the west at 60-80°, and the Yangla Fault dips to the east at 30-70° [3]. These faults controlled the distribution of the regional magmatic zone. The NE-trending normal fault F4, which is approximately 6 km long, and the related parallel faults in the Yangla mining district have dip direction NW and dip angles in the range of 42-80°, and controlled the spatial orientation of the Cu ore body and intrusions (Figure 1(c)). In addition, fracture zones and secondary structural fissures, which were widely developed by regional compression during the Triassic Indosinian Orogeny and by emplacement of the Jiaren granitoid at 230 Ma [22], controlled the spatial orientation, outcrop occurrence, and morphology of the skarn Cu ore bodies and intrusions. The Linong Anticline and Jiangbian Syncline are the major fold structures in the Yangla mining district [5,6].
The magmatic rocks in the YCD, including basalt, granodiorite, quartz-monzonite porphyry, and diabase, are distributed over a relatively large area. The zircon U-Pb ages of the basalts (362:0 ± 8:0 Ma and 296:1 ± 7:0 Ma), which crop out in the northwest part of the Yangla mining district [24] (Table 1, Figure 3), suggest basalt formation during the Hercynian period. These basalts could have formed in the expanded setting of the enriched mantle source area or by ocean spreading of the ocean basin behind the arc of the Jinshajiang; however, these events are not significantly related to the Cu mineralization [24][25][26]. The granodiorite and quartz-monzonite porphyry intrusion occurs in the middle part of the Yangla and exhibits an oval shape that is approximately 2 km in length and 1.5 km in width with a total exposed area of 2.6 km 2 [2,4]. The granodiorite has been identified as I-type granite containing a mixed source of crustal-and mantle-derived magma [2,3,6]. Previous studies have shown that the granodiorite, with emplacement ages mostly in the range of 208-239 Ma (Table 1, Figure 3) [8,25,[27][28][29][30], formed during the Indosinian orogeny, and might have formed in the late-collisional or postcollisional setting of the Jiangda-Weixi volcanic arc and the Qamdo-Simao block, which are closely related to the Cu mineralization [25]. The whole rock Rb-Sr and zircon U-Pb ages of the quartz-monzonite porphyry are 202 Ma and 261:0 ± 3:3 Ma, respectively, and have little relation with the Cu mineralization [30,31]. The zircon U-Pb age of the diabase is 222:0 ± 1:0 Ma, indicating formation during the Indo-China epoch [8,32]. This body also has little relation with the Cu mineralization.   Figure 6). Zone I: weak chloritization-pyritization-silicification; Zone II: fine-veined calcitized-pyritized granite porphyry; Zone III: strong silicification-calcitization-weak pyritization; Zone IV: granite porphyry vein with strong silicification and calcitization, pyritization, chalcopyritization, and molybdenitization; Zone V: skarn-type copper ore body; Zone VI: fracture crushing zone; Zone VII: massive ore-rich body; Zone VIII: fracture crushing zone; Zone IX: yellowish-brown-brown massive garnet skarn; Zone X: massive skarn-type ore body; and Zone XI: weakly skarnified sericitic sandy slate and metamorphic quartz sandstone.

Geofluids
The YCD Cu ore bodies in the exoskarn zones or within the intrusion-distal interlayer fracture zones are generally stratiform, stratoid, bedded, veined, or lenticular and dip gently to the west at angles of 30°-40°. The main ore body types are skarn, hornfels, porphyries, and hydrothermal veins [33]. The major ore bodies KT2, KT4, and KT5 are mainly skarn ore bodies and account for 90% of the Cu resources in the Linong ore block. The molybdenite Re-Os ages of the skarn ore bodies are 228-234 Ma, with an average age of 230 Ma (Table 1, Figure 3) [1,25,27,34,35]. This indicates that the skarn ore bodies formed during the Indo-China epoch, which is consistent with the emplacement ages (208-239 Ma) of the granodiorites with an average age of 230 Ma. The predominant ore minerals are chalcopyrite, pyrite, and pyrrhotite; small amounts of bornite, galena, molybdenite, sphalerite, malachite, and covellite are also present [36]. The gangue minerals include quartz, calcite, mica, plagioclase, diopside, and garnet [36,37]. Automorphic-xenomorphic granular, cataclastic, and interstitial textures are most common in the sulfide ores; the ore structures are mainly dense massive, disseminated, veined, or banded [26,33,36]. fault zone that has a NE strike of 60°and a NW dip of approximately 40°. The contact boundary lies between the GPs and the wall rocks are irregular; the internal and external contact zones underwent minor alterations including silicification, sericitization, chloritization, carbonation, and argillization ( Figure 5, Figure 6).
The grayish-white GPs exhibit porphyritic texture and massive structure (Figures 7(a)-7(f)). The main phenocrysts are quartz and plagioclase, at approximately 20% and 10%, respectively, with a small amount of biotite at less than 2%. The size of the quartz phenocrysts is generally 1-5 mm, although the largest are almost 20 mm. The shapes are mostly hexagonal, quadrangular, irregular, and euhedral to subhedral, with some exhibiting corrosion edges. Most of the plagioclase phenocrysts have particle sizes in the range of 1-3 mm, with the largest at approximately 20 mm. These phenocrysts are altered as sericite, chlorite, and kaolinite pseudomorp. The biotite phenocrysts are generally less than 2 mm in size and similarly retain only their external shape, having been replaced by sericite and other minerals (Figures 7(g)-7(i)). Zircon, pyrite, chalcopyrite, and other minor sulfide minerals occur as accessory minerals. The matrix is cryptocrystalline-microcrystalline and exhibits felsophyric texture. The main components are quartz and plagioclase, with a small amount of biotite, which underwent minor sericitization, kaolinization, silicification, and carbonation (     (Table 2).

Zircon U-Pb
Dating. Three GP samples were collected from the tunnel in the 3250 m-deep section of the Linong ore block, YCD. The samples were crushed, and single zircons were separated using flotation and electromagnetic methods. Next, zircons with good crystal shape, transparency, and color were selected manually using a binocular microscope. These zircons were attached to an epoxy resin surface and were then polished and photographed under transmitted and reflected light. Zircons with good crystal characteristics were selected for cathodoluminescence (CL) photography, and the CL photographs were used as the basis for selecting typical magmatic zircons for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) dating analysis. The CL imaging of zircons was conducted in the electron probe analysis room of Northwest University in Xi'an. Zircon U-Pb dating was performed at the same institution, although in the LA-ICP-MS room of the State Key Laboratory of Continental Dynamics. The analysis employed a 7500a ICP-MS instrument (Agilent Technologies, Inc., Lexington, Massachusetts. USA) and a

Crystallization Age.
Single zircons were selected from three objects-GP samples 3250-41Lb1, 3250-41Lb2, and 45-R4. One point on each zircon was measured. The CL images of the zircons from the three samples are dark gray in color and exhibit clear crystal shapes of long or short columns approximately 100-300 μm in length. The color of the zircons was quite dark, resulting in relatively weak zircon CL. The zircons are highly automorphic. Magmatic oscillatory belt structures (growth zones) were clearly developed ( Figure 8), which indicates that the zircons are typical magmatic zircons [42]. Data of the LA-ICP-MS zircon U-Pb dating of the GPs are listed in Table 3.    (Figure 9) [43]. The 206 Pb/ 238 U ages of the 11 zircons are 194 ± 2-206 ± 2 Ma, and the weighted average age is 199:7 ± 2:1 Ma, MSWD = 3:4 (n = 11). All of the sample points on the zircon 206 Pb/ 238 U-207 Pb/ 235 U concordia diagram fall on or near the harmonic line ( Figure 10). Good correspondence was noted among the 206 Pb/ 238 U ages of the 11 measurement points, which formed a relatively concentrated zircon group with a harmonic age of 195:3 ± 6:4 Ma, MSWD = 3:3 (n = 11). The harmonic age is essentially consistent with the weighted average age and is likely the GP's replacement age.

Major Elements.
The major element data of the GPs are listed in Table 4. The loss on ignition (LOI) values are high (>4.23 wt.%), suggesting that these rocks might have undergone low-grade hydrothermal alteration during postmagmatic events [44][45][46]. Therefore, the effects of hydrothermal alteration on the related elements are discussed subsequently in Section 5.1.
The SiO 2 -oxide scatter diagram does not show obvious linear correlation between the SiO 2 and other oxides of the GPs (Figure 11), which indicates insignificant fractional crystallization during the diagenetic process. In comparison with the granodiorites of the Yangla mining district, the GPs are relatively rich in SiO 2 and Fe 2 O 3 T but are deficient in K 2 O, Na 2 O, and P 2 O 5 . The GPs plots concentrated in the granodiorite region in the SiO 2 -(Na 2 O + K 2 O) diagram (Figure 12(a)). The K 2 O values of the GPs are higher than those of Na 2 O, with high K 2 O/Na 2 O ratios. All plots on the SiO 2 -K 2 O diagram (Figure 12(b)) are within the range of the calc-alkaline series. The Rittmann index (δ) of the GPs, at 0.13-0.15 (<3.30) with an average value of 0.14 ( Table 4), also confirms that the GPs belong to calc-alkaline series rocks. The alkalinity (AR) is 1.23-1.25, and the aluminum saturation index (A/CNK) is 1.22-1.78. The GPs plots concentrated in the calc-alkaline series on the SiO 2 -AR diagram (Figure 12(c)) also indicate calc-alkaline series characteristics. The influence of low-grade alteration such as silicification and carbonation potentially caused the GPs plots to be relatively dispersed on the A/CNK-A/NK diagram (Figure 12(d)). Nevertheless, all are located within the field of the peraluminous series.   Table 5). The values of the transition elements Sc, V, Cr, Co, and Ni are relatively low. The primitive mantle-normalized spider diagram (Figure 13(a)) shows that the GPs are rich in large-ion lithophile elements (LILEs) such as Rb, Ba, Th, U, K, and La. Specifically, the Ba is relatively depleted compared with the Rb, Th, and U; Sr shows the greatest depletion relative to the LILEs. High field strength elements (HFSEs) such as Ta, Nb, Ce, Zr, Hf, and Ti are depleted compared with the LILEs; Ti shows the greatest depletion. The GPs are significantly rich in Pb but are deficient and slightly deficient in P and Ti, respectively. In addition, the values of metallogenic elements show the trend of Cu > Pb > Zn, Cu in the highest abundance. In the relationship diagram between SiO 2 and trace elements, SiO 2 is negatively correlated with Cu ( Figure 14(a)), Pb (Figure 14(e)), and Y (Figure 14(f)) but positively correlated with Cs ( Figure 14(b)), Ta (Figure 14(c)), and U ( Figure 14(d)). (Table 6)  14 Geofluids   (Figure 15(a)).

Evaluation of Alteration Effects.
Studies have show that the extensive alteration effects occurred during the metallogenic process of the magmatic-hydrothermal deposit and its mineralization often related to granitoid intrusions [44,46]. Previous research indicates the existence of mainly (i)   16 Geofluids potassic, (ii) propylitic, (iii) phyllic, and (iv) argillic alterations as hydrothermal alteration processes of the orebearing porphyry dikes in ore deposit [47,48]. (i) The potassic alteration developed mainly K-feldspar and finegrained hydrothermal biotite, which were controlled strictly by the high-temperature single-phase fluid (initial fluid) [49]. (ii) The propylitic alteration is characterized by abundant hydrous minerals such as quartz + epidote + chlorite + pyrite ± actinolite ± chalcopyrite veins, which were limited by the fluid containing a mixture of magmatic brine and the circulating groundwater heated by the intrusion [50].
(iii) The phyllic alteration is represented by sericite and substantial quartz, which was affected by the low-temperature liquid phase fluid that directly separated from the magma [51]. (iv) The argillic alteration is characterized by kaolinite and illite and overlies the phyllic alteration of Stage (iii). The alteration in this stage was influenced mainly by a lowdensity gas phase originating from the differentiation of the high-temperature single phase fluid in Stage (i) and a lowtemperature liquid phase fluid originating from the lowtemperature liquid phase fluid in Stage (iii) [48].
In the GPs of the YCD, only small amounts of sericite, chlorite, and kaolinite are overlain and filled with the surface of plagioclase and biotite phenocrysts (Figures 5 and 6) and small amounts of secondary veined quartz-calcite and veined-disseminated pyrite and chalcopyrite (Figure 7), which based on the results of the ore field observation, thin-section petrographic observation, and the LOI values >   (Table 4). These features of aforementioned indicated a few of the GP samples could have undergone minor hydrothermal alteration but there were absent of the aforementioned typical altered mineral assemblages. Because the hydrothermal fluids slightly affected the alteration system, medium-temperature-medium salinity and lowtemperature-low salinity ore-forming fluids might be indicated, although such fluids cause only weak hydrothermal alteration in GP dikes [52]. Only a few altered minerals are developed, including minor sericite, chlorite, and kaolinite as well as a few secondary quartz, calcite, pyrite, and chalcopyrite [52]. Therefore, we can roughly speculate that the GPs underwent low-grade hydrothermal alteration as evidenced by the altered mineralogy and hydrothermal fluids. This process might not be related to the evidence forming the basis of discussion on the major and trace elements in this study. Previous studies also have shown that the HFSEs, REEs, and transition elements (e.g., Sc, V, Zr, Nb, Ta, and Hf) are commonly immobile and are unaffected by hydrothermal alteration [44,46,53,54]. Some elements such as Ti, Fe, and P are not transported by hydrothermal alteration [53], whereas Ca, Na, and K as well as LILEs (e.g., Sr, Ba, and Rb) are generally mobile [55]. Thus, the existence of hydrothermal alteration effects can be verified by analyzing the contents of these elements in our samples. In addition, a lack of significant correlation between the ratios of incompatible elements such as Ba/La, Ba/Rb, and Rb/Sr of our samples versus the LOI values (Figures 16(a)-16(c)) indicates that these elemental ratios could be a feature of the source region and were unaffected or slightly affected by hydrothermal alteration [46]. The beginning processes of geochemical systems, such as alteration, commonly lead to mass transfers of specific components [56]. For example, hydrothermal alteration can cause potassium anomalies, and the K 2 O concentrations in a hydrothermal deposit increase during alteration [57].

Geofluids
Our GP samples exhibit variable K 2 O concentrations of 1.20-3.84 wt.% and high K 2 O/Na 2 O ratios. In correspondence, an obvious negative correlation trend between the K 2 O and LOI values except for sericitization and Kmetasomatism (Figure 16(d)) is expected because the Krich alterations are related to K-rich water-bearing minerals such as sericite and chlorite. Similarly, an evident correlation trend between the Sr and K 2 O contents is also expected because K 2 O controls the Sr content in alteration minerals [46]. Such correlation trends do not appear in the Sr versus K 2 O diagram (Figure 16(f)), which indicates that the Sr might not have been affected by hydrothermal alteration. Furthermore, the GPs exhibit low Na 2 O concentrations of 0.05-0.13 wt.%, which might have caused Na depletion in the plagioclase owing to the aforementioned low-grade hydrothermal alteration. However, the Na 2 O versus LOI diagram ( Figure 16(e)) shows a slightly positive correlation, which might be attributed to the formation of small amounts of albite or other Na-rich minerals during hydrothermal alteration. Moreover, no significant difference was noted in the GPs and minor hydrothermal alteration of the Yangla granodiorite plutons (LOI < 3:40 wt:%) in a series of diagrams. These diagrams include major elements versus SiO 2 diagrams, except Na 2 O versus SiO 2 diagrams, in Figure 11(g); K 2 O + Na 2 O versus SiO 2 , K 2 O versus SiO 2 , and AR versus SiO 2 diagrams, except those for A/NK versus A/CNK in Figure 12(d); K 2 O/MgO, Zr, Nb, and Y versus 10000 Ga/Al ACF diagrams in Figure 17; Nb versus Y, Ta versus Yb, Rb versus Yb + Ta, Rb versus Y + Nb, and Rb/30-Hf -3 × Ta diagrams in Figure 18; and Ba versus Sr, Rb versus Sr, δEu versus SiO 2 , and La/Yb versus δEu diagrams in Figure 19. All of these diagrams indicate similar geochemical characteristics and can be further discussed using K-, Na-, and Ca-related diagrams with respect to low-grade hydrothermal alteration. I -t y p e g r a n i t e t r e n d St y p e g r a n i t e t r e n d

Geofluids
We therefore suggest that the Rb, Sr, Ba, HFSEs, REEs, and transition elements (Zr, Nb, Ta, and Hf) can be used to document the petrogenesis and tectonic setting of the GPs to avoid further controversy in this study.

Comparison with Yangla Granodiorite Plutons.
The two zircon U-Pb ages of the GPs, 195:3 ± 6:4 Ma and 198:40 ± 8:6 Ma, are significantly younger than the ages of the Yangla granodiorite plutons, at 208-239 Ma, indicating that the GPs formed slightly later. One zircon U-Pb age of a GP, 213 ± 15 Ma, clearly falls in the Yangla granodiorite pluton age range (without error ranges). The Yangla granodiorite plutons have only one hornblende Rb-Sr age, at 208 Ma, which is younger than the zircon U-Pb age of 213 Ma; all other zircon U-Pb ages are older than 213 Ma (without error ranges) ( Table 1). This can be attributed to variation in the minerals and methods. Therefore, even though the GPs and granodiorite plutons have overlapping age ranges, the GPs are significantly younger than the Yangla granodiorite plutons. This also indicates that magmatic activities in the Yangla mining district might have lasted for~44 Ma.
Although the SiO 2 values in the GPs and Yangla granodiorites are similar, the effects of mineralization and alteration resulted in the former having lower Na 2 O, K 2 O, and P 2 O 5 values than the latter. However, the GPs have higher CaO, LOI, and K 2 O/Na 2 O ratios (Table 4, Table 7, Figure 11) and trace element (Cu, Cs, Ta, Pb, and U) values (Table 5,  Table 7, Figure 13, Figure 14) than the granodiorites. This might have been caused by mineralization and alteration to secondary calcite, sericite, and chlorite. The values of other trace elements in the GPs, such as Sc, V, Cr, Co, Ni, Rb, Sr, and Zr, are relatively low. In addition, the GPs are relatively rich in Cu, Pb, and other metallogenic elements. The ΣREE and LREE values of the GPs are slightly lower than those of the granodiorites. The δCe values of the GPs and granodiorites exhibit slightly weak negative and positive anomalies, respectively. No significant difference was noted between the δEu of the GPs and the granodiorites ( Table 6, Table 7, and Figure 15). This preliminary result indicates that the magmatic source area of the GPs and the Yangla granodiorite plutons might be the same or similar.

Granite Porphyry Type.
Granites are usually classified as I-, S-, A-, or M-types, depending on the properties of the magmatic source areas [58]. I-and S-type granites have similar geochemical characteristics in some elemental properties. I-type granites are crust-mantle mixed-source granites in a collision-related tectonic setting and are composed mainly of quartz, plagioclase, K-feldspar, hornblende, and biotite. They are rich in Na (Na 2 O > K 2 O), Rb, Th, U, P, and A/ CNK < 1:0 and are deficient in Nb, Ta, Ti, and P [4]. S-type granite is peraluminous granite formed by partial melting and crystallization of crust-source sediments. It is composed mainly of quartz, plagioclase, and biotite, showing enrichment in K (K 2 O > Na 2 O), Rb, Ta, U, and A/CNK > 1:1 and depletion of Ba, Ti, and P [59]. The GPs have higher K 2 O values than Na 2 O (1:20-3:84 wt:% > 0:05-0:13 wt:%,) which is consistent with the K-enrichment characteristic of S-type granites (Table 4). According to the Cross, Iddings, Pirrson, and Washington (CIPW) standard minerals calculation results for the GPs and the Yangla granodiorites, the standard corundum and diopside values of S-type granites and I-type granites are 0.59-5.65 wt.% and 0.08-8.03 wt.%, indicating that the GPs and granodiorites might be S-granites and I-type granites, respectively. In addition, the GPs were subjected to low-grade effects of alteration, which resulted in obvious variation ranges for the A/NK and A/CNK ratios. Even though the plots on the A/CNK-A/NK diagram are relatively scattered, they are concentrated mostly in the peraluminous region (Figure 12(d)), which is consistent with the behavior of S-type granites (A/CNK > 1:10). Furthermore, the samples of GPs and granodiorites fall mostly within the fields of S-type granites in the ACF I-S-type granite discriminant diagram (Figure 17(e)), with a few samples falling within the fields of I-type granites. This preliminarily suggests that the GPs and Yangla granodiorites belong to S-I -t y p e g r a n i t e t r e n d St y p e g r a n i t e t r e n d      (Figure 11(h)), which is consistent with the evolution trend of S-type granite. However, the Yangla granodiorite plutons have a negativecorrelation evolution trend (Figure 11(h)) and might belong to I-type granites. The Pb and Y values negatively correlate with the SiO 2 values, which is consistent with the evolutionary trend of S-type granites (Figures 14(e) and 14(f)). This indicates that the GPs might belong to S-type granites [60,61]. The GP samples show clear positive correlation in the Y versus Rb (Figure 14(g)) and Th versus Rb (Figure 14(h)) diagrams, suggesting that the GPs might be I-type granites. However, the granodiorite plutons show clear positive correlations in the Pb versus SiO 2 (Figure 14(e)) and Th versus Rb (Figure 14(h)) diagrams, indicating that the Yangla granodi-orites might be I-type granites. This is consistent with previous research results [2,4,7,28]. Furthermore, clear negative correlations were noted in the Y versus SiO 2 (Figure 14(f)) and Y versus Rb (Figure 14(g)) diagrams, indicating that the granodiorite plutons might belong to S-type granites. Therefore, the aforementioned geochemical characteristics of the GPs and Yangla granodiorite plutons might have the comprehensive characteristics of S-and Itype granites, respectively.

Geofluids
A-type granite represents anhydrous granite produced in an extensional tectonic setting, and its source area has diverse materials. The mineral compositions of A-type granites are quartz, mafic minerals (Fe-rich), alkaline feldspar, and plagioclase, which are characterized by enrichment in Si, Na, Zr, Nb, Ce, Y, Ta, and K and deficiency in Ca, Mg, high      (Figure 17(a)), Zr-10000 Ga/Al (Figure 17(b)), Nb-10000 Ga/Al (Figure 17(c)), and Y-10000 Ga/Al (Figure 17(d)) diagrams. A relative deficit of HFSEs such as Nb, Ta, and Zr, was noted, which is also incon-sistent with the characteristics of A-type granites that are rich in Nb, Ta, and Zr. This indicates that the GPs and granodiorite plutons are not A-type granites, although they might be I-or S-type granites [4,7,25,63]. M-type granites formed during the later stage of the fractional crystallization process of basaltic magma in a tectonic setting of an ocean island arc and a mid-ocean ridge; they belong to mantle-derived granite, with an A/ CNK ≤ 0:6, and deficiencies in Ba, Ti, and P [64]. The geochemical features of the granite plutons from the entire Yangla mining district do not coincide with M-type  29 Geofluids granite and thus do not belong to the M-type granites in this study [4,7,25,[65][66][67].

Implications of Tectonic Setting.
The JSB is an important component of the Paleo-Tethys Ocean; therefore, its evolution is significant for the entire eastern Paleo-Tethys Ocean [2]. It has been suggested that the Jinshajiang Ocean opened in the Late Devonian or Early Carboniferous (~360 Ma) and that the regional collision event ended prior to the Late Triassic (~200 Ma) [2,3]. For the subduction-collision-related events, the Niangjiushan plagiogranites and the Jiyidu granodiorites in the JSB yielded SHRIMP zircon ages of 285 ± 6 Ma and 263 ± 6 Ma [19], implying that the Jinshajiang oceanic slab subducted westward in a postcollisional and latecollisional tectonic setting during the Permian (290-250 Ma) and the Late Triassic (250-200 Ma), respectively. The three GPs have zircon U-Pb ages of 213 ± 15 Ma,198:40 ± 8:6 Ma, and 195:3 ± 6:4 Ma, respectively. Therefore, it is conceivable that these GPs are related to a postcollisional or late-collisional tectonic setting.
Furthermore, within the regional area, the Ludian intrusion (234-214 Ma) and Lincang intrusion (~230 Ma) have similar geochemical characteristics and formation ages as those of the GPs and might have been produced under a postcollisional or late-collisional setting [68]. Additionally, in the tectonic setting discrimination diagram plots (Figure 18), the GPs and Yangla granodiorite samples show the following characteristics: (i) All of the GPs and Yangla granodiorite samples fall within the fields of syncollisional granite (syn-COLG) and volcanic arc granite (VAG) in the Y-Nb (Figure 18(a)), Yb-Ta (Figure 18 (Figure 18(e)) diagrams. Considering the achievements of previous studies, the tectonic setting of the Yangla granodiorites should have been late-or postcollision [2,4,7,25,34,37]. This is consistent with the geotectonic setting of the JSB, which had fully entered the collision-orogenic stage, leading to the formation of COLG [4,7,25,33]. Therefore, the GPs might have been generated under a post-or late-collisional tectonic setting, which is consistent with the Yangla granodiorite plutons.

Magma
Source. The geochemical characteristics of some elements can be used to trace the materials of magmatic source regions [69,70]. In the Al 2 O 3 /ðMgO + FeO T Þ versus CaO/ðMgO + FeO T Þ and Rb/Ba versus Rb/Sr discriminant diagrams (Figure 20), the GPs and granodiorite plutons both exhibit similar source material compositions-mainly claypoor rocks (sandstone and shale) with small amounts of basic-acidic rocks. This indicates that they might share the same (or similar) sources; the predominant source of the original magma was a crust-mantle mixture [2][3][4]. In the (La/Yb) N -δ (Eu) diagram ( Figure 19(d)), the GPs and granodiorite plutons samples also fall mainly within the crust-type and crust-mantle-type fields, respectively. This preliminary study indicates that the initial magma formed through interaction of the mantle and crust and then underwent partial melting in the lower crust before being emplaced as intrusive complexes [71]. Therefore, the samples belong to multistage homologous intrusive complexes. Thus, the GPs and granodiorites might have shared a similar original magma source and genesis and are likely products of the same magmatic system. These inferences are also supported by various factors: (a) The duration of the magmatic activities in the Yangla mining district is likely~30 Ma [28,37]; (b) the GPs and granodiorites, at 195-213 Ma and 208-239 Ma, respectively, have an overlapping region of replacement ages, indicating continuity of magmatic system evolution in the Yangla mining district; and (c) the GPs and granodiorites have nearly identical geochemical characteristics, including those of major and trace elements and REEs, as well as tectonic settings. 5.6. Petrogenetic Process and Model of the GPs. In the La/Sm versus La (Figure 21(a)) and La/Yb versus La (Figure 21(b)) discriminant diagrams of the magmatic process, the GPs and granodiorite plutons show an inclined distribution, suggesting that the diagenetic process involved mainly partial melting rather than fractional crystallization. The GPs and the majority of the granodiorite samples fall within the field of low pressure (<5 kbar) in the (Al 2 O 3 /FeO T + MgO + TiO 2 ) versus (Al 2 O 3 + FeO T + MgO + TiO 2 ) ( Figure 22) pressure discrimination diagram. This suggests that the diagenetic depth of the GPs is slightly less than that of the Yangla granodiorites and is consistent with the characteristics of the stage of magma system evolution in the Yangla mining district. In addition, the Sr-Ba (Figure 19(a)), Sr-Rb (Figure 19(b)), and SiO 2 -δEu ( Figure 19(c)) diagrams indicate crystallization of various . The underplating of mantle-derived magma at the crust-mantle boundary is an important process by which crust-mantle mixing can be triggered [2,72]. Therefore, the diagenetic process of the GPs and Yangla granodiorite plutons can be described as follows. Regional tension in the late-and postcollision tectonic setting could have caused the asthenosphere to surge upward to underplate the base of the lower crust [2][3][4]. Under the conditions of high temperature and decompression, the lower crust remelted xand mixed with the mantle-derived magma. The resultant mixture was thus contaminated with large amounts of upper crustal fusible components including sedimentary materials during its ascent, forming a ternary magma (upper crust + lower crust + mantle). The subsequent partial melting led to the formation of the Yangla granodiorite plutons with I-type granites coupled with minor affinity to S-type granites in the shallow emplacement process (low pressure ≤ 5 kbar). The residual magma, which had more contamination by upper crust sedimentary materials, then entered an epithermal setting of low pressure (<5 kbar) and formed GPs with S-type granites with minor affinity to Itype granites. Therefore, the GPs of the YCD were formed from residual magma following the diagenetic process of the Yangla granodiorites plutons in an epithermal setting ( Figure 23).

Conclusion
We combined zircon U-Pb age dating, whole-rock geochemical data, and REE data to constrain the geochronology, tectonic setting, and petrogenesis of the GPs analyzed in this study. The following conclusions were reached.
(1) The zircon U-Pb dating results revealed GP formation at 195-213 Ma, which is slightly later than that of the Yangla granodiorite plutons, at 208-239 Ma, under a late-or postcollisional tectonic setting. The results suggest that the collision was completed during the Early Jurassic and that the magmatic activities occurring in the Yangla mining district might have lasted for~44 Ma, during 239-195 Ma (2) Compared with the Yangla granodiorite plutons, the GPs share similar major, trace, and REE geochemistry, although they are rich in Cu, Pb, Cs, Ta, and U

Geofluids
and deficient in Rb, P, Ta, Ti, ΣREE, and LREE, with insignificantly negative anomalies of Eu and slightly weak negative anomalies of Ce. This indicates that these granites underwent partial melting with separation of the Ti-bearing phase, plagioclase, and biotite. This preliminary result indicates that the GPs and the Yangla granodiorite plutons might have had the same or similar magmatic source area. Genetically, the GPs are slightly metaluminous to peraluminous S-type granites, whereas the Yangla granodiorite plutons are metaluminous to slightly peraluminous I-type granites (3) Based on the post-or late-collisional tectonic setting, the GPs and Yangla granodiorite plutons likely originated from a ternary mixture of upper crust + lower crust + mantle materials. Such three-component magmas and subsequent partial melting could have been responsible for the generation of the Yangla granodiorite plutons and GPs in a shallow setting under low pressure ≤ 5 kbar and an epithermal setting under low pressure of <5 kbar, respectively

Data Availability
The data used to support the findings of this study are available from the corresponding author upon request.

Conflicts of Interest
The authors declare that they have no conflicts of interest.