Geochemistry, Zircon U–Pb Ages, and Hf Isotopes of the Devonian Maﬁc and Acidic Dykes of the Jinba Gold Deposit, NW China: Petrogenesis and Tectonic Implications

: The Jinba deposit is an orogenic gold deposit located in the Markakuli shear zone, in the southern part of the Altay orogenic belt, northwestern China. Several granite and diorite dykes are present in the area of the mine, with ore bodies occurring in the diorite dykes. However, the diagenetic age, genesis, and evolution of these magmas, and the tectonic setting of the dyke emplacement process, remain unclear. The present study is based on a detailed geological survey, zircon U–Pb dating, Lu–Hf isotopes, and geochemical analysis of the granitic and diorite dykes. The crystallization ages of the granitic and diorite dykes are 384.5 ± 1.2 Ma and 393.9 ± 3.5 Ma, respectively, which indicates formation in the Early to Middle Devonian. Zircon ε Hf(t) values of the granitic and diorite dykes are 1.43 to 5.2 and − 4.47 to − 1.18, respectively, with a corresponding two-stage model of depleted mantle (T DM2 ) ages of 1046 to 1285 Ma and 1242 to 2623 Ma, respectively. This indicates that the granitic and diorite dykes were formed by the mixing of mantle magma and crustal materials to varying degrees, and diorite dykes are more obviously contaminated by the lower crust. Geochemical analysis shows that the granite dykes have a high SiO 2 (72.51%–74.87%) and moderate Al 2 O 3 (12.88%–14.04%) content, a total alkali of (K 2 O + Na 2 O = 5.51%–6.44%), and aluminous (A/CNK = 1.0–1.02). Granite dykes are enriched in LREE and Th, U, and Pb, and depleted in P, Sr, and Nb elements, with clear Eu negative anomalies ( δ Eu = 0.62~0.66). The SiO 2 content of diorite dykes is 51.48%–53.71%, Al 2 O 3 contents are high (14.70%–15.99%), K 2 O is 1.94%–2.54%, Na 2 O is 2.97%–3.96%, MgO contents are high (5.15%–6.46%), and TFe 2 O 3 is (13.42%–15.13%), enriched Sr, U, Pb, deﬁcient Th elements, rare earth fractionation is not obvious, and Eu anomaly is not obvious ( δ Eu = 0.93~1.1). We conclude that the Early to Middle Devonian magmatism in the southern margin of Altay (which corresponds to the Jinba gold deposit) may have formed in an island arc-related subduction environment.


Introduction
The Altay orogenic belt is located at the junction of China, Mongolia, Russia, and Kazakhstan, and is an important part of the Central Asian Orogenic Belt (CAOB) [1][2][3][4][5][6]. The CAOB experienced Paleozoic accretion and Meso-Cenozoic intracontinental orogenesis [7][8][9][10]. It is characterized by complex tectonic and orogenic activity, frequent magmatic activity, and an extensive distribution of intrusive rocks, volcanic rocks, and subvolcanic rocks. This makes the CAOB, and specifically the Altay area, ideal for the study of tectonic evolution, crustal accretion, and mineralization-tectonics relationships. Indeed, there has been a great deal of research on the intrusive, volcanic, and subvolcanic rocks in the area; however, there are differing opinions on the formation age, source, and evolution of the magmatic materials, tectonic environment, and its relation to mineralization [11][12][13][14][15][16][17].
The Jinba gold deposit is located in the back arc basin of the Kelan in the southern margin of the Altay orogenic belt. Studies on the deposit mainly focus on its geological characteristics, genesis, metallogenic chronology, and exploration potential [18][19][20][21][22]. However, there is little research on the magmatic rocks of the Jinba deposit, especially on granitic and diorite dykes. It is worth noting that some ore bodies of the Jinba gold deposit occur within diorite dykes. In addition, the relationship between the magmatic activity of these dykes and the mineralization at Jinba is not clear at present. The granitic and diorite dykes are specifically located in the Habahe pluton, which is the largest intrusive body in the area.
The Habahe pluton is located on the northeastern side of the Markakuli fault, with an irregular-shaped outcrop area of approximately 180 km 2 [23]. It is a complex massif formed all at once and is mainly composed of medium and coarse-grained tonalite. The study of these dykes plays an important role in the geochronology, mantle origin, and tectonic evolution of the southern Altay, and provides important information on the relationship between the dykes and the coeval intrusive rocks in the area. The age, genesis, and tectonic setting of these dykes is clarified by the comprehensive study of whole-rock geochemical composition, zircon U-Pb chronology, and zircon Lu-Hf isotope data provided in the present study. Based on the results of this study and the available data for magmatic rocks in the southern Altay margin, their Devonian tectonic setting is discussed in order to provide insight into the relationship between dykes and mineralization and the tectonic evolution of the southern margin of the Altay orogenic belt.

Regional Geology
The Jinba deposit is located near the border between China and Kazakhstan and is the extension of the metallogenic belt in the Kazakhstan mining area. Exposed strata mainly include littoral and neritic sedimentary rocks of the Middle and Lower Devonian Tuokesalei formation. Volcano-sedimentary rocks are intercalated with carbonate rocks in the Middle Devonian Ashele formation. The intermediate-acid volcanic rocks of the Upper Devonian Qiye formation are in angular unconformity with the overlying and underlying strata [24]. Quaternary sediments are also present in the area. Fracture development is widespread in the area, with structures present in the northern and western parts of the area, and near north-to-south structures. The region's largest tectonic structure is the Irtysh fault zone, which divides the Siberian plate and the Kazakhstan-Junggar plate, as shown in Figure 1B [25]. The secondary fault system of the Irtysh fault zone, the Markakuli shear zone, affects the spatial distribution of intrusive rocks and ore deposits [26]. Magma activity is frequent in the area, and plutonic intrusive rocks and volcanic rocks are developed. Ultrabasic, basic, and acidic plutonic rocks are exposed, mainly middle to late Variscan intermediate-acidic and acidic units, which are mainly distributed along both sides of the Markakuli fault in the form of bedrock and rock strata and intruding into the strata of the Tuokesalei and Ashele formations. Basic to acidic outcrops occur in the form of rock strata, and the rock mass is relatively complex and small in area. There are also acidic, intermediate, and basic dykes and wall rocks distributed along the direction of the regional fault zone. The volcanic rocks crop out to the northeast of the Markakuli fault, with a NWN-SE distribution. They are mainly intermediate-acidic and intermediate units, with few basic rocks [27]. The Ashele copper-zinc deposit, Zhelande, Saidu, Tuokuzibayi, and Jinba gold deposits have been discovered in the area. (Figure 1A).
At present, six ore bodies have been proved in the Jinba deposit [21] (Figure 2A). Mineralization types can be divided into altered-rock type and quartz-vein type. Alteredrock-type orebodies mainly occur in altered diorite dykes, which are vein-like or lenticular, including orebodies I, II, III, and V ( Figure 2B). At present, six ore bodies have been proved in the Jinba deposit [21] (Figure 2A). Mineralization types can be divided into altered-rock type and quartz-vein type. Alteredrock-type orebodies mainly occur in altered diorite dykes, which are vein-like or lenticular, including orebodies I, II, III, and V ( Figure 2B).  [21]). (B) Geological cross-section of the orebodies (modified after Wang et al. [21]).

Sample Descriptions
The granite dyke intrudes into the Habahe pluton, Habahe County, northwest China. Their hand specimens are predominantly grayish white, with rough granite structures and massive structures ( Figure 3A). The main mineral composition is feldspar (60%), quartz (30%), biotite (10%), and a small amount of hornblende. Quartz contains a small amount of basic mineral inclusions, mainly biotite and hornblende ( Figure 3B). The main  [21]). (B) Geological cross-section of the orebodies (modified after Wang et al. [21]).

Sample Descriptions
The granite dyke intrudes into the Habahe pluton, Habahe County, northwest China. Their hand specimens are predominantly grayish white, with rough granite structures and massive structures ( Figure 3A). The main mineral composition is feldspar (60%), quartz (30%), biotite (10%), and a small amount of hornblende. Quartz contains a small amount of basic mineral inclusions, mainly biotite and hornblende ( Figure 3B). The main accessory minerals are zircon, apatite, and magnetite.

LA-ICP-MS Zircon U-Pb Geochronology
Zircon grains were separated from the diorite and granite sam magnetic and density techniques. Zircon grains free of visible incl were handpicked, embedded in epoxy resin, and polished to expos polished grains were further examined by cathodoluminescence (C JXA-8100 electron microprobe at the Langfang Regional Geologica China. Zircon U-Pb dating and trace element analyses were perfo Yandu Zhongshi Testing Technology Co. LTD (Beijing, China) usin MS. The detailed method has been described by Liu et al., [28]. Data ~20-30 s for blank signal and ~50 s for sample signal. Data processing ICPMS Data Cal software [28]. U-Pb isotope fractionation effects w Diorite dykes are gray in color, with variable complementary semi-idiomorphic granular structure and massive structure ( Figure 3C). Plagioclase: 60%, euhedral, semieuhedral plate, poly-flake double crystal, sodium compound double crystal development, plate length 0.2-1.2 mm, scattered distribution. Hornblende: 35%, columnar, granular, less with hexagonal geometric section, hornblende cleavage development, particle size 0.15-1.2 mm, scattered distribution. Quartz: small amount, xenomorphic granular, particle size 0.1-0.5 mm, star-dot distribution. Apatite: small amount, columnar, granular. Opaque minerals: 2%-3%, xenomorphic granular and irregular granular ( Figure 3D). More distributed in hornblende edge.

LA-ICP-MS Zircon U-Pb Geochronology
Zircon grains were separated from the diorite and granite samples by conventional magnetic and density techniques. Zircon grains free of visible inclusions and fractures were handpicked, embedded in epoxy resin, and polished to expose grain centers. The polished grains were further examined by cathodoluminescence (CL) imaging using a JXA-8100 electron microprobe at the Langfang Regional Geological Survey, Langfang, China. Zircon U-Pb dating and trace element analyses were performed at the Beijing Yandu Zhongshi Testing Technology Co. LTD (Beijing, China) using a Brooke M90 ICP-MS. The detailed method has been described by Liu et al., [28]. Data acquisition time was~20-30 s for blank signal and~50 s for sample signal. Data processing was carried out with ICPMS Data Cal software [28]. U-Pb isotope fractionation effects were calibrated using zircon 91500 as the external standard [29], and NIST 610 glass was used for instrument optimization. Analytical data are presented on U-Pb concordia diagrams with 2σ errors, and weighted mean ages are quoted at the 95% confidence level using ISOPLOT software [30].

Major and Trace Element Analyses
The major and trace element contents of 5 diorite samples and 5 granite samples were obtained at ALS Mineral-ALS Chemex in Guangzhou, China. The samples were first crushed with a steel-jaw crusher and then ground to 200 mesh with an agate mortar. Major elements were analyzed by X-ray fluorescence ME-XRF26X, and trace element concentrations were determined by rare earth mass spectrometry (ME-MS81) and inductively coupled plasma atomic emission spectrometry. A mixture of HF and HNO 3 was added to the melted sample and tartaric acid digestion was performed according to the analytical method of [31] (Method ME-MS61). The samples were stored at 190 • C for 48 h with indium as internal standard and the China National Standard sample as monitoring sample. The analysis accuracy of major and trace elements (REE) is better than 5% and 10%, respectively. Ignition losses (LOI) for all samples were obtained by heating them in a pre-fired silicon crucible at 1000 • C for 1 h and recording the percentage of weight loss.

In Situ Zircon Lu-Hf Isotope Analysis
Zircon Lu-Hf isotope analysis of previous U-Pb sites was performed using a Neptune Plus MC-ICP-MS and a New Wave UP 213 laser ablation detector. The work was conducted at the Beijing Yandu Zhongshi Testing Technology Co., LTD. Beam diameter was 45 µm and laser repetition rate was 10 Hz. Helium and argon were, respectively, used as carrier gas and supplementary gas for analysis. The international zircon standard GJ1 was adopted as the external standard. Operating conditions were provided by [32,33]. Using 91500, MON, and GJ-1 as reference standards, the recommended 176 Hf/ 177 Hf ratios are 0.282307, 0.282739, and 0.282015, respectively. It is assumed that the average crustal 176 Lu/ 177 Hf ratio is 0.015, and the current chondritic 176 Hf/ 177 Hf and 176 Lu/ 177 Hf ratios are 0.282772 and 0.0332, respectively. 176 Lu/ 177 Hf ratios in the mean mantle are 0.28325 and 0.0384 [34,35]. The decay constant of 176 Lu is 1.865 × 10 −11 year −1 [36].

Zircon U-Pb Ages
Zircon LA-ICP-MS, U-Pb dating, and trace element analysis results are shown in Table 1. Most of the zircon specimens in the samples studied show similar signatures. Zircon grains in the samples are irregular in shape ( Figure 4). Grain sizes range from 50 to 200 µm with aspect ratios of 1:1 to 2:1. CL imaging reveals that most grains have fine oscillatory growth zones, which suggest a magmatic origin [37].

Granite Dykes
The 232 Th content of zircons found in granite ranges from 197,307 to 789,253 ppb, 238 U content ranges from 305,346 to 975,726 ppb, and Th/U ratios are between 0.40 and 0.96. Twenty-nine zircon grains fall in the range of 379.6-386.8 Ma with a weighted mean age of 384.5 ± 1.2 Ma (MSWD = 0.42, n = 29) ( Figure 5A), which we interpret as the emplacement age of the granitic dykes.

Zircon Hf isotopic compositions
Zircon Hf isotopic analysis results are shown in Table 2  Thus, it can be seen from the above data that the granitic dyke material originated from the depleted mantle and was mixed with partially molten crust, while the diorite dyke material was derived from the lower crust ( Figure 6).

Zircon Hf isotopic compositions
Zircon Hf isotopic analysis results are shown in Table 2  Thus, it can be seen from the above data that the granitic dyke material originated from the depleted mantle and was mixed with partially molten crust, while the diorite dyke material was derived from the lower crust ( Figure 6).
In the TAS diagram, all granite data points fall into the granite range dykes fall within the monzonite range. In the K2O vs. SiO2 diagram, granit

Major Elements
Elemental analysis data of granite and diorite dykes are shown in

Trace Elements
The total rare earth element content of the granite dykes is 93.80~99.63 μg/g. The standardized chondrite rare earth element diagram (Figure 8a) shows that LREE elements are evidently enriched, and the ratios of (La/Yb)N and La/Yb are 5.44-7.31 and 7.58-10.20, respectively. There is a clear Eu anomaly (Eu/Eu* = 0.62-0.66, average 0.64), and Yb content is 2.03~2.56 μg/g, with an average of 2.26 μg/g. The normalized trace element distribution diagram of the original mantle (Figure 8b) shows that diabase is enriched in LILE (Rb, K, and Sr) and depleted in HFSE (Nb, Ta, Zr, Hf, and Ti).
The total rare earth content of diorite dykes is 50.36~56.52 μg/g. The chondrite normalized REE diagram (Figure 8c  In the TAS diagram, all granite data points fall into the granite range, and diorite dykes fall within the monzonite range. In the K 2 O vs. SiO 2 diagram, granite plots in the calc-alkaline series (Figure 7b), and diorite dykes plots in the high-K, calc-alkaline series. In the A/CNK vs. A/NK diagram (Figure 7c), granite dykes are located at the junction of the metaluminous and peraluminous fields, and diorite dykes fall within the hyperaluminous range.

Trace Elements
The total rare earth element content of the granite dykes is 93.80~99.63 µg/g. The standardized chondrite rare earth element diagram (Figure 8a) shows that LREE elements are evidently enriched, and the ratios of (La/Yb) N  μg/g, with an average of 3.27 μg/g. In the original mantle-normalized trace element distribution curve (Figure 8d), samples show enrichment of LILEs (Rb, Th, Ba, K) and depletion of HFSEs (Ta, Nb, Ti).  [43] (1984) and Sun et al. [44] (1989)).

Emplacement Ages of Dykes and Magmatism
Plagioclase granite dykes (Habahe pluton) are important orebody host rocks of the Jinba gold deposit. This pluton is widely exposed in the region and crops out over an area of 540 km 2 . Researchers have conducted a large number of chronological studies on the Habahe pluton and suggested the emplacement ages of the pluton are within the range of 406 to 390 Ma [23,45]. The age of mafic dykes from the Habahe pluton is 375 Ma [46]. Zircon U-Pb ages of granite and diorite dykes intruding the Habahe pluton are 384.5 ± 1.2 Ma (MSWD = 0.42, n = 29) and 393.0 ± 2.2 Ma (MSWD = 0.10, n = 12), respectively. Extensive alteration and mineralization are observed on the edges and/or inner parts of some diorite dykes, indicating a close relationship with gold mineralization.
There is no accurate mineralization age data for the Jinba gold deposit to date, while a lot of chronological data (Table 4) have been reported for the Zhelande and Saidu gold deposits, located ~15 km and ~10 km northwest of the Jinba deposit, respectively. These three deposits are all emplaced in Devonian strata and within the Markakuli shear zone, which is controlled by NW-trending faults. They all have similar mineralization types (quartz-vein + altered-rock types), mineral assemblages, fluid characters, and isotope

Emplacement Ages of Dykes and Magmatism
Plagioclase granite dykes (Habahe pluton) are important orebody host rocks of the Jinba gold deposit. This pluton is widely exposed in the region and crops out over an area of 540 km 2 . Researchers have conducted a large number of chronological studies on the Habahe pluton and suggested the emplacement ages of the pluton are within the range of 406 to 390 Ma [23,45]. The age of mafic dykes from the Habahe pluton is 375 Ma [46]. Zircon U-Pb ages of granite and diorite dykes intruding the Habahe pluton are 384.5 ± 1.2 Ma (MSWD = 0.42, n = 29) and 393.0 ± 2.2 Ma (MSWD = 0.10, n = 12), respectively. Extensive alteration and mineralization are observed on the edges and/or inner parts of some diorite dykes, indicating a close relationship with gold mineralization.
There is no accurate mineralization age data for the Jinba gold deposit to date, while a lot of chronological data (Table 4) have been reported for the Zhelande and Saidu gold deposits, located~15 km and~10 km northwest of the Jinba deposit, respectively. These three deposits are all emplaced in Devonian strata and within the Markakuli shear zone, which is controlled by NW-trending faults. They all have similar mineralization types (quartz-vein + altered-rock types), mineral assemblages, fluid characters, and isotope composition [47][48][49], suggesting the same geodynamic setting and metallogenic timing. The interpreted age of gold mineralization is based on Rb-Sr, K-Ar, and Ar-Ar ages of alteration minerals and FIs in ore-bearing quartz veins [19,23,45,[50][51][52][53][54]. Mineralization in the region is interpreted to have occurred between ca. 300 and 270 Ma with a peak value of 290 Ma, which is consistent with the period of orogenic events in the region during the Late Carboniferous-Early Permian. It can be seen from the above research that the ore-forming age and the dyke emplacement age of the Jinba gold deposit are not consistent, which indicates that there is no centralized or large-scale mineralization in the initial emplacement of dykes. As an orogenic gold deposit, the minerals of the Jinba gold deposit are mainly derived from diorite and Ashele formation rocks [22], that is to say, diorite dykes provide metal ore-forming materials for mineralization.

Granite Dyke
The granitic dykes are calc-alkaline, weakly peraluminous and have the characteristics of differentiated I-type granites [55]. In addition, the rock does not contain cordierite, garnet, or white mica. The content of P 2 O 5 is far less than 0.15%, and the content of K 2 O + Na 2 O is low. Judging from 10,000 × Ga/Al, the granite dykes are neither S-type nor A-type. It can be seen from Figure 9a,b that the granite dykes are I-type granites. Rb/Sr values in the granitic dykes (0.40-0.88) are significantly higher than the Rb/Sr values in the upper crust (0.25), indicating that the rocks have undergone separation crystallization. As can be seen from Figure 9c, the granitic dykes have also undergone differentiation. Thus, the granite dykes belong to I-type granites which are formed by crystallization differentiation. Moreover, the high εHf(t) and the relatively young TDM of the depleted mantle model suggest that the granitic dykes may have originated from a relatively young source region, possibly through fractional crystallization or early partial melting of mantle-derived magma. The linear relationship between the ratio of K/Rb and K/Cs and SiO2 is not very obvious, suggesting that the fractional crystallization of magma is not strong. At the same time, the relationship between La/Sm and La showed a significant positive correlation, indicating that although a certain degree of crystallization differentiation occurred during the ascending emplacement of magma, it was mainly controlled by partial melting. The Nb/Ta values of all samples range from 11.6 to 13.4, and the Zr/Hf values range from 34.1 to 35.2, which are close to the corresponding crustal element ratios of 11 and 33, respectively. The Th/Ta ratios of the samples range from 12.6 to 14.9, which is comparable to the Th/Ta ratios of the crust (approximately 10) [58]. The samples have low Sr contents (102.5-188 μg/g), Al2O3 (12.9%-14.0%), and Ti/Zr of less than 20 (11.8-14.4), which indicates that the granitic veins are typical partial melting products of the continental crust [59,60]. All the rocks have an obvious negative Eu anomaly, with a strong depletion in Sr, P, Ti, and other elements, Zr/Sm > 10 (32.9-43.6), and high Yb content (2.03-2.56 μg/g), indicating that there are plagioclase, apatite, and hornblende residues in the mineral facies of the asthenosphere [61]. Therefore, it is considered that the granite dykes are mainly formed by mixing and melting of crustal and mantle materials with slight crystallization differentiation. Moreover, the high ε Hf (t) and the relatively young T DM of the depleted mantle model suggest that the granitic dykes may have originated from a relatively young source region, possibly through fractional crystallization or early partial melting of mantle-derived magma. The linear relationship between the ratio of K/Rb and K/Cs and SiO 2 is not very obvious, suggesting that the fractional crystallization of magma is not strong. At the same time, the relationship between La/Sm and La showed a significant positive correlation, indicating that although a certain degree of crystallization differentiation occurred during the ascending emplacement of magma, it was mainly controlled by partial melting. The Nb/Ta values of all samples range from 11.6 to 13.4, and the Zr/Hf values range from 34.1 to 35.2, which are close to the corresponding crustal element ratios of 11 and 33, respectively. The Th/Ta ratios of the samples range from 12.6 to 14.9, which is comparable to the Th/Ta ratios of the crust (approximately 10) [58]. The samples have low Sr contents (102.5-188 µg/g), Al 2 O 3 (12.9%-14.0%), and Ti/Zr of less than 20 (11.8-14.4), which indicates that the granitic veins are typical partial melting products of the continental crust [59,60]. All the rocks have an obvious negative Eu anomaly, with a strong depletion in Sr, P, Ti, and other elements, Zr/Sm > 10 (32.9-43.6), and high Yb content (2.03-2.56 µg/g), indicating that there are plagioclase, apatite, and hornblende residues in the mineral facies of the asthenosphere [61]. Therefore, it is considered that the granite dykes are mainly formed by mixing and melting of crustal and mantle materials with slight crystallization differentiation.

Diorite Dykes
The main elements are positively correlated with the change of MgO content, indicating that there may be some separated crystallization in the process of magmatism. Cr and Ni contents in diorite dykes are low (10-20 µg/g and 4.8-6.7 µg/g), and lower than those of primary basaltic magma (300-400 µg/g and 300-500 µg/g) [62]. This indicates that the diorite dyke magma experienced significant separation crystallization of mafic minerals such as olivine, monoclinic pyroxene, and ferrotitanium oxides. The diorite dykes are depleted of rare earth elements in different degrees and the chondrite normalized REE distribution curve, and all samples have the same variation trend and typical N-MORB REE geochemical characteristics, indicating that the diorite dykes derived from the depleted asthenospheric mantle. All the samples are characterized by an enrichment of large ion lithophile elements (Rb, Th, Ba, K) and depletion of high field strength elements (Ta, Nb, Ti), indicating that the magma source was contaminated and metasomatized by crustal components [63]. Ti/Zr values range from 11.2 to 18.1, and Ti/Y values range from 31.5 to 41.3, which is close to crustal contents (Ti/Zr < 30, Ti/Y < 200) [64,65]. Rb/Sr values range from 0.31 to 0.64, indicating a crustal origin [66]; thus, the original magma was mixed with crustal materials to a certain extent during magma ascension. In addition, the Lu-Hf isotopic system in zircon can explain magma origin and petrogenesis [67,68]. Indeed, ε Hf(t) values of diorite dykes range from −1.18 to −4.47, and T DM2 values range from 1242 to 1668 Ma, indicating that the magma may have both relatively ancient lower crust and depleted mantle components. In addition, the high Nb and Ta contents (1.8-2.8 ppm, 0.11-0.16 ppm) also indicate the obvious crustal mixing. The mixing of depleted mantle and ancient crust led to a change in ε Hf(t) , and the degree of change depends on the mixing ratio of the two [69]. Thus, in general, the diorite dykes were the product of rising mantle magma that underwent mafic mineral crystallization and mixing with crustal material.

Tectonic Setting
The granite dykes have obvious characteristics of I-type granites and high Th/Ta ratio (12.6-14.9), which are geochemical characteristics of subduction zone magma. In addition, the granitic dykes have low Yb, Ta, and Th contents, enrichment of U, Pb, and LREE, depletion of Ti, P, Sr, and Ba, negative Nb and Ta anomalies, and weak negative Eu anomalies, similar to island arc magmatic rocks in subduction zones. In the Nb-Y and Rb-Y + Nb discrimination diagrams for granitic dykes (Figure 10), all samples fall within the volcanic arc granite region. The granitic dykes are depleted of P, Nb, Ti, Sr and enriched in Rb, Th, K, La, and the Hf isotope indicates that the granitic dykes have an obvious addition of continental crust material, indicating that the granitic dykes were formed in an island arc environment on active continental margins. Diorite dykes show similar compositions to N-MORB in Nb/Yb-Th/Yb (Figure 11a), which point towards mantle sources. In addition, the Nb and Ta contents of diorite dykes are 1.8-2.8 μg/g and 0.11-0.16 μg/g, respectively, which are similar to typical island arc tholeiite (1.7-2.7 μg/g, 0.1-0.18 μg/g). In V-Ti/1000 (Figure 11b), the samples all fell into the island arc tholeiite area. In general, diorite dykes are enriched in large ion lithophile Diorite dykes show similar compositions to N-MORB in Nb/Yb-Th/Yb (Figure 11a), which point towards mantle sources. In addition, the Nb and Ta contents of diorite dykes are 1.8-2.8 µg/g and 0.11-0.16 µg/g, respectively, which are similar to typical island arc tholeiite (1.7-2.7 µg/g, 0.1-0.18 µg/g). In V-Ti/1000 (Figure 11b), the samples all fell into the island arc tholeiite area. In general, diorite dykes are enriched in large ion lithophile elements and light rare earth elements and depleted in high field strength elements. Diorite dykes have exactly the same characteristics as subduction-related island arc magmatism [70], so diorite dykes are characterized by continental or island arc magmatism associated with subduction zones [71]. Figure 10. Discriminant diagram of granite dyke tectonic environment in the Jinba deposit (according to Pearce et al. [70]). WPG-intraplate granite; VAG-volcanic arc granite; Syn-COLG-syncollisional granite; ORG-ocean ridge granite.
Diorite dykes show similar compositions to N-MORB in Nb/Yb-Th/Yb (Figure 11a), which point towards mantle sources. In addition, the Nb and Ta contents of diorite dykes are 1.8-2.8 μg/g and 0.11-0.16 μg/g, respectively, which are similar to typical island arc tholeiite (1.7-2.7 μg/g, 0.1-0.18 μg/g). In V-Ti/1000 (Figure 11b), the samples all fell into the island arc tholeiite area. In general, diorite dykes are enriched in large ion lithophile elements and light rare earth elements and depleted in high field strength elements. Diorite dykes have exactly the same characteristics as subduction-related island arc magmatism [70], so diorite dykes are characterized by continental or island arc magmatism associated with subduction zones [71]. Zircon U-Pb ages of granitic and diorite dykes in the Jinba gold deposit are 384 Ma and 393 Ma, respectively, which belong to the products of Early-Mid-Devonian magmatic activity in the southern margin of the Altay belt. Previous studies have proved that the southern margin of Altay was in an active continental margin environment at this time [14,[74][75][76][77][78]. Thus, based on this study, the granitic and diorite dykes of the Jinba gold deposit were formed in an island arc environment related to subduction. Zircon U-Pb ages of granitic and diorite dykes in the Jinba gold deposit are 384 Ma and 393 Ma, respectively, which belong to the products of Early-Mid-Devonian magmatic activity in the southern margin of the Altay belt. Previous studies have proved that the southern margin of Altay was in an active continental margin environment at this time [14,[74][75][76][77][78]. Thus, based on this study, the granitic and diorite dykes of the Jinba gold deposit were formed in an island arc environment related to subduction.

1.
Zircon U-Pb ages of granite and diorite dykes are 384~393 Ma, indicating Early-Middle Devonian magmatic activity. The mineralization age of Jinba gold deposit is Late Carboniferous-Early Permian. The mineralization age of the Jinba gold deposit does not coincide with granite dykes and diorite dykes.

2.
The granite dykes are mainly formed by the mixing and melting of crustal and mantle materials with slight crystallization differentiation, while diorite dykes are the product of rising mantle magma that underwent crystallization of mafic minerals and mixing with crustal material. 3.
The granitic and diorite dykes of the Jinba gold deposit were formed in an island arc environment related to subduction.