Petrogenesis and oxidation state of granodiorite porphyry in the Jurassic Chuankeng skarn Cu deposit, South China: Implications for the Cu fertility and mineralization potential

Journal Pre-proofs Petrogenesis and oxidation state of granodiorite porphyry in the Jurassic Chuankeng skarn Cu deposit, South China: Implications for the Cu fertility and mineralization potential Xin Zhang, Pei Ni, Guo-Guang Wang, Yao-Hui Jiang, Ding-Sheng Jiang, SuNing Li, Ming-Sen Fan PII: DOI: Reference:

S1367-9120(19)30536-X https://doi.org/10.1016/j.jseaes.2019.104184 JAES 104184

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Journal of Asian Earth Sciences

Received Date: Revised Date: Accepted Date:

30 May 2019 21 November 2019 3 December 2019

Please cite this article as: Zhang, X., Ni, P., Wang, G-G., Jiang, Y-H., Jiang, D-S., Li, S-N., Fan, M-S., Petrogenesis and oxidation state of granodiorite porphyry in the Jurassic Chuankeng skarn Cu deposit, South China: Implications for the Cu fertility and mineralization potential, Journal of Asian Earth Sciences (2019), doi: https://doi.org/10.1016/j.jseaes.2019.104184

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Petrogenesis and oxidation state of granodiorite porphyry in the Jurassic Chuankeng skarn Cu deposit, South China: Implications for the Cu fertility and mineralization potential Xin Zhang, Pei Ni *, Guo-Guang Wang*, Yao-Hui Jiang, Ding-Sheng Jiang, Su-Ning Li, Ming-Sen Fan

State Key Laboratory for Mineral Deposits Research, Institute of Geo-Fluids, School of Earth Science and Engineering, Nanjing University, Nanjing 210023, China

Correspondence information: Pei Ni*, Nanjing University, NO. 163, Xianlin Avenue, Qixia District, Nanjing City, Jiangsu Province, China E-mail: [email protected] Tel: +86 25 89680883 Fax: +86 25 89682393 Correspondence information: Guo-Guang Wang*, Nanjing University, NO. 163, Xianlin Avenue, Qixia District, Nanjing City, Jiangsu Province, China E-mail: [email protected] Tel: +86 25 89680883 Fax: +86 25 89682393

Abstract Large-scale Jurassic porphyry–skarn Cu mineralization in the Qin-Hang metallogenic belt of South China has attracted much attention, but comparative studies of porphyries in large- and small-scale deposits are lacking. In this paper, we present new zircon U–Pb ages, trace element composition and Hf isotopic composition as well as whole-rock geochemical and Sr–Nd isotopic compositions for the porphyries associated with mineralization in the small-scale Chuankeng Cu deposit. Drawing on our data for the Chuankeng deposit and existing data for the nearby giant Dexing Cu deposit, we aim to identify factors controlling the mineralization potential of both deposits. Granodiorite porphyries of Chuankeng deposit were emplaced at ca. 161–158 Ma. They have moderate SiO2 contents of 61.9–66.1 wt. % and high Sr/Y (59–135) and (La/Yb)N (4–14) ratios. Their high MgO contents (0.2–2.9 wt.%), lack of negative Eu anomaly, depletion in Y and Yb, relatively high initial 86Sr/87Sr ratios (0.7076–0.7078), and low Nd(t) values (−4.5 to −4.9), indicating that the Chuankeng porphyries were derived from partial melting of delaminated lower crust. The Middle–Late Jurassic Chuankeng porphyries are considered to have been formed in a localized intracontinental extension environment along the Jiangshao Fault in response to far-field stress from Paleo-Pacific Plate subduction. Although no Middle–Late Jurassic magmatic arc rocks have been found in the study area, the Chuankeng porphyries display similar characteristics to arc rocks. On the basis of their zircon Hf(t) values (−2.6 to +0.9), two-stage Hf model ages (1.4–1.1 Ga), and regional geological history, we infer that magma source of Chuankeng porphyries were mainly Neoproterozoic

juvenile crust with the involvement of Paleoproterozoic ancient crust. Thus their arclike features were inherited from the Neoproterozoic juvenile crust that formed by subduction of oceanic crust during the Jiangnan orogeny. Chuankeng porphyries have lower zircon Ce4+/Ce3+ and higher Ti-in-zircon temperatures and lower whole rock Nd and zircon Hf values than the Dexing porphyries, indicating they are less oxidized and less hydrous and with more involvement of the ancient crustal material in the magma source, which could explain the relatively small-scale Cu mineralization in Chuankeng. This study highlights the values of integrated studies of whole rock Nd and zircon trace element and Hf isotopic compositions in assessing the potential for Cu mineralization.

Keywords: Chuankeng copper deposit; Neoproterozoic juvenile crust; Adakitic rock; Magma fertility; South China

1. Introduction Porphyry–skarn deposits are the largest sources of Cu, providing 75% of the world’s Cu resources copper (Meinert, 2005; Hou et al., 2009; Sillitoe, 2010; Cooke et al., 2011). They generally display close genetic and spatial links with small-scale intrusions emplaced at shallow crustal levels (Richards, 2007; Chiaradia et al., 2009). However, not all felsic intrusions are associated with economic porphyry–skarn deposits. The productivity of porphyry–skarn deposits are strongly influenced by the source, the oxidation state and water content of the causative magmas (Oyarzun et al., 2001; Cooke, 2005; Jugo, 2009; Richards, 2009; Haschke et al., 2010).

The Qinhang metallogenic belt (QHMB) is an economically important Mesozoic porphyry–skarn Cu–polymetallic metallogenic belt in South China, hosting many large to giant porphyry–skarn Cu deposits (Mao et al., 2013; Ni and Wang, 2017). In addition to large porphyry–skarn Cu deposits related to Jurassic porphyries (Wang et al., 2012a; Wang et al., 2015; Chen et al., 2017a), some Jurassic porphyries occurring in the QHMB are associated with small-scale deposits. An understanding of the distinct geochemical characteristics of intrusions in large and small deposits would aid the prediction of the economic potential of regional porphyry–skarn Cu mineralization (Richards, 2013). Previous studies have explained the origin of some large to giant ore deposits (e.g., the Dexing and Yinshan deposits, Wang et al., 2012a, 2015; Li et al., 2017b), but there has been relatively little study of the geochemical differences of porphyries between giant and small deposits in the QHMB. The Chuankeng skarn Cu deposit is located in the eastern part of QHMB, near the giant Dexing Cu deposit geographically. It hosts 0.3 Mt Cu (Luo, 2015), making it 30 times smaller than the Dexing deposit containing 9 Mt Cu (Zhu et al., 1983). Here, we present new zircon U–Pb ages, trace element and Hf isotopic data as well as wholerock major and trace element compositions and Sr–Nd isotopic data for porphyries associated with mineralization in the Chuankeng deposit are also determined. Using our data for the Chuankeng porphyries and previously published data for ore-related porphyries in the Dexing deposit, we attempt to (1) clarify the magma source and petrogenesis of porphyries in the Chuankeng deposit, (2) examine the different geochemical characteristics of porphyries related to giant- and small-scale

mineralization, and (3) provide a strategy for efficient exploration of economic porphyry–skarn Cu deposits in QHMB.

2. Regional geology South China include the Yangtze Block in the northwest and the Cathaysia Block in the southeast, separated by the NNE-trending Qin-Hang belt (Zheng et al., 2013; Ni et al., 2017; Fig. 1), which extends from the Jiangshan–Shaoxing Fault (hereafter the Jiangshao Fault) in the northeast to Hangzhou Bay in Guangxi Province (Yang and Mei, 1997). This belt is generally considered to represent a tectonic suture zone formed through amalgamation of the two blocks (Mao et al., 2013; Ni et al., 2015). The original amalgamation of the Yangtze and Cathaysia blocks along the Qin-hang belt occurred during the Neoproterozoic, leading to the Jiangnan orogeny (Zhao et al., 2011; Wang et al., 2012b; Charvet, 2013; Ni et al., 2018), after which the unified South China Block underwent Caledonian (middle Paleozoic), Indosinian (Triassic) and Yanshanian (Jurassic–Cretaceous) tectonothermal events (Lepvrier et al., 2004; Shu et al., 2015; Li et al., 2017a; Xu et al., 2017). Numerous Middle to Late Jurassic (171–150 Ma) calcalkaline granitoids rocks and related Cu–Au–Mo–Pb–Zn–W–Sn deposits distributed along the Qin-Hang belt in response to the Jurassic Paleo–Pacific Plate subduction (Wang et al., 2013b; Zhu, 2016; Chen et al., 2017b; Zhang et al., 2017b; Li et al., 2017c). These deposits constitute an important intracontinental Cu-polymetallic metallogenic belt (Qin-Hang metallogenic belt) in South China, with a length of ca. 2000 km and a width of ca. 100–150 km (Mao et al., 2013).

On the basis of structural and tectonic evolution characteristics, the Qin-Hang metallogenic belt (QHMB) can be roughly divided into two parts: the eastern part (Shaoxing–Pingxiang area), characterized by Cu–Au deposits (Liu et al., 2012; Cai et al., 2016; Yuan et al., 2018); and the western part (Nanling area), with W–Sn deposits (Huang et al., 2015; Chen et al., 2018). The pre-Cambrian strata in the eastern QHMB comprises predominantly Mesoproterozoic–Neoproterozoic volcanic and sedimentary rocks, including the Shuangqiaoshan and Shuangxiwu groups to the north of the Jiangshao Fault (Wang et al., 2007; Zhang et al., 2018a) and the Chencai and Zhoutan groups to the south (Li et al., 2011; Shu et al., 2011; Wang et al., 2013c; Yao et al., 2013). The basement strata is overlain by Cambrian–Quaternary rocks including Cambrian–Silurian terrigenous clastic units (Zhu et al., 2016) and Devonian– Middle Triassic sandstone and limestone units. The area also contains widespread Yanshanian intermediate–acidic volcanic rocks and granitoids associated with Cu–polymetallic mineralization. Mineralization in the QHMB includes the Dexing Cu (Mo–Au), Yinshan Cu (Pb–Zn–Au–Ag) and Dongxiang Cu deposits to the north of the Jiangshao Fault (Li et al., 2007a; Zhou et al., 2012; Cai et al., 2016), and the Chuankeng Cu and Yongping Cu (Mo) deposits to the south (Sun et al., 2016; Ni et al., 2017; Zhang et al., 2018b).

3. Deposit geology and petrology Three major formations are recognized in the Chuankeng Cu deposit, from bottom to top: (i) the Lower Triassic Tieshikou Formation comprising siltstone and mudstone

units with limestone interlayers (the main ore-bearing host rock); (ii) the Middle Triassic Yangjia Formation comprising siltstone and shale units; and (iii) Quaternary sedimentary sandstones and conglomerates, separated from the underlying Triassic sediments by an angular unconformity. A NE–SW-trending overturned fold and NEand NW-striking faults occur in the Chuankeng deposit (Fig. 2). Igneous rocks of the Chuankeng deposit were emplaced as NE–SW-striking stocks and dikes. The igneous rocks in association with mineralization are granodiorite porphyries containing idiomorphic phenocrysts of andesine (23%–33%), K-feldspar (10%–15%), quartz (10%–15%), biotite (10%), and amphibole (1%–10%) (Fig. 3A– D). The granodiorite porphyries also contain abundant accessory minerals, including magnetite, apatite, zircon, and titanite. Skarn-type orebodies are located mainly along the contact zone between granodiorite porphyries and Triassic carbonates. Chalcopyrite is the predominant ore mineral, coexisting with pyrite and minor magnetite and sphalerite. The ores have massive, vein-like, and disseminated structures. Gangue minerals include garnet, chlorite, diopside, epidote and quartz. Field and microscope studies indicate that skarn formation and mineralization can be divided into four stages. Stage I involved thermal metamorphism with limestones being converted to marble, while impure carbonate units such as silty limestone or calcareous shale being transformed to hornfels (Fig. 3E, F). Stage II was the prograde alteration stage during which fluid metasomatism resulted in the formation of anhydrous assemblages such as garnet and pyroxene. Stage III was the later retrograde

alteration stage when garnet and clinopyroxene were partly replaced by epidote, chlorite and magnetite, accompanied by quartz, calcite, chalcopyrite, pyrite, magnetite, molybdenite, pyrrhotite, and sphalerite (Fig. 3G–J). During Stage IV, calcite and quartz were predominant, with rare chalcopyrite and pyrite being formed as veinlets crosscutting skarn and sulfides.

4. Analytical methods 4.1. In situ LA–ICP–MS zircon analysis Two samples of porphyries (CK70 and CK135) were collected from the 70 m and 135 m levels of an open pit in the study area, respectively. Samples were crushed and zircons were first separated by standard magnetic and density techniques. Then representative zircons were handpicked under a binocular microscope and mounted in epoxy resin disks that were then polished to reveal zircon interiors and were gold coated. Zircon grains prepared for further study were imaged under transmitted and reflected light at Nanjing University, and cathodoluminescence (CL) was used to examine the internal structures of the zircons at Hongchuang Laboratory, Nanjing, China. Zircon LA-ICP-MS isotopic and trace element analyses were undertaken using an Agilent 7700e ICP-MS coupled to a Geo-LasPro ArF excimer LA system at Shangpu Laboratory, Wuhan, China. Details of the analytical procedures and data reduction are given by Zong et al. (2017) and are briefly summarized here. The LA-ICP-MS analyses used a laser beam with a beam diameter of 32 m and an energy density of 5 J/cm2 at a repetition rate of 5 Hz. Argon was used as a make-up

gas that was mixed with helium carrier gas via a T-connector prior to entering the ICP. Nitrogen was added into the central Ar + He gas flow of the Ar plasma to reduce detection limits and improve precision (Hu et al., 2015). Each analysis incorporated a background acquisition of 20–30 s (gas blank) followed by 50 s of data acquisition. A 91500 standard zircon was used for calibration, mass discrimination, and to monitor U– Th–Pb isotope fractionation using the preferred U–Th–Pb isotopic ratios given by Wiedenbeck et al. (1995). The precision and accuracy of the U–Th–Pb dating by LA–ICP–MS were assessed using a GJ-1 standard zircon (Jackson et al., 1984), and a NIST SRM 610 glass standard (Pearce et al., 1997) used for external standardization of the concentrations of U, Th, Pb, and other trace elements. The off-line selection and integration of background and analyzed signals, time drift corrections, and the quantitative calibration used during U– Th–Pb dating were all undertaken using the ICPMSDataCal software package (Liu et al., 2010). Uncertainties associated with the preferred values for the external 91500 zircon standard were propagated into the final results reported in this paper. Concordia diagrams and weighted mean calculations were made using Isoplot v. 3.0 (Ludwig, 2003). Zircon Ce anomalies and Ti-in-zircon temperatures were calculated using data collected during U–Pb dating, employing parameters such as Ce4+/Ce3+, EuN/EuN* [where the subscript N indicates chondrite normalization, EuN*= (SmN/GdN)1/2)] and zircon thermometry calculated using the methods outlined by Ballard et al. (2002), Baldwin et al. (2007), Ferry and Watson (2007), and Trail et al. (2011, 2012).

4.2. In situ zircon Hf analysis Zircon LA-ICP-MS U–Pb dating was followed by in situ LA-multi-collector (MC)-ICP-MS determination of the Hf isotopic compositions of zircons, employing a Neptune MC-ICP-MS instrument attached to a 193 nm ArF excimer LA system at the State Key Laboratory for Mineral Deposits Research, Nanjing University, Nanjing, China. The instrumental conditions and data acquisition procedures are given by Hou et al. (2007). The in situ Hf isotopic analysis of zircons used a laser beam diameter of 44 m, a laser repetition rate of 8 Hz, and a laser energy of 11.5–13.6 J/cm2. The ablated aliquot was transported from the LA cell via a mixing chamber to the ICP–MS torch using helium as a carrier gas. The isobaric interferences of were corrected using

176Lu/175Lu

and

176Yb/173Yb

176Lu

and

176Yb

on

176Hf

values of 0.02658 and 0.796218,

respectively (Chu et al., 2002). Instrumental mass bias was corrected by normalizing Yb isotopic ratios to a 172Yb/173Yb value of 1.35274 (Chu et al., 2002) and Hf isotopic ratios were normalized to a

179Hf/177Hf

value of 0.7325, both using exponential laws.

Data quality was monitored by the repeat analysis of a 91500 standard zircon (176Hf/177Hf = 0.282293 ± 0.000015; n = 17; 2), yielding results that are consistent with the reported 176Hf/177Hf ratio for this standard (0.282306; Woodhead et al., 2004). Initial

176Hf/177Hf

ratios and Hf (t) values were calculated with reference to the

chondritic reservoir at the time of zircon crystallization from the associated magma, as determined by the U–Pb ages obtained during this study, enabling the clear identification of the timing of magmatism. We have adopted a decay constant for 176Lu of 1.865×10−11 yr−1 (Scherer et al., 2001), and the chondritic ratios of

176Hf/177Hf

(0.282772) and 176Lu/177Hf (0.0332) as derived by Blichert-Toft and Albarede (1997). Single-stage model ages (TDM1) were calculated relative to a modeled depleted mantle with present-day

176Hf/177Hf

and

176Lu/177Hf

values of 0.282772 and 0.0384,

respectively (Vervoort and Blichert-Toft, 1999). Two-stage model ages (TDM2) were calculated relative to a modeled crustal reservoir assuming an average continental crustal 176Lu/177Hf ratio of 0.015 (Griffin et al., 2000).

4.3. Whole-rock major and trace element contents The 10 least-altered samples, as inferred from field and petrographic observations, of the porphyries associated with the mineralization were selected for whole-rock major and trace element analyses. Prior to analysis, the samples were crushed and powdered in an agate mill. Major and trace element concentrations were determined at FocuMS Technology, Nanjing, China. Major elements were analyzed by wet chemistry and Xray fluorescence (XRF) methods with analytical uncertainties <5% in relative terms. Trace and rare earth element (REE) concentrations were determined using ICP-MS, employing pure elemental standard solutions for external calibration. The precision of these data was determined by analyses of AGV–2, W–2, and OU–6 reference standards, yielding uncertainties of <10% in relative terms for elements with abundances of <10 ppm and <5% in relative terms for elements with abundances of >10 ppm. Details of the analytical procedures used for these trace element analyses are given by Gao et al. (2003).

4.4. Whole-rock Sr–Nd isotopic analyses Whole-rock Sr and Nd isotopic compositions were measured using MC-ICP-MS at FocuMS Technology, Nanjing, China. Mass discrimination correction for Sr and Nd were carried out via internal normalization to 88Sr/86Sr ratio of 8.37521 and 146Nd /144Nd ratio of 0.7219 (Lin et al. 2016). The USGS geochemical reference materials BHVO2, BCR-2, and AGV-2 were used as quality controls, which yielded results identical within error to their published values (Li et al. 2017d).

5. Results 5.1. LA-ICP-MS zircon U–Pb dating The results of LA-ICP-MS zircon U-Pb dating are listed in Table 1 and shown in Fig. 4. The zircons are euhedral, 100–300 m long, and generally show oscillatory zoning in CL images, indicating a magmatic origin. A small number of zircons have unzoned cores that appear dark in CL images (Fig. 4). The zircons contain variable concentrations of U (46–602 ppm) and Th (39–409 ppm), yielding Th/U ratios of 0.2– 2.0 (Table 1). Igneous zircons generally have Th/U ratio values ≥0.5 (Hoskin and Schaltegger, 2003), whereas zircons with lower ratios (<0.5) most likely crystallized in the presence of aqueous fluids (Bacon and Lowenstern, 2005). A total of 24 analyses of zircons from sample CK70 yield a weighted mean 206Pb/238U

age of 161 ± 1 Ma [2; mean standard weighted deviation (MSWD) = 0.49].

One of the zircons within this sample has a clear core–rim structure where the core yielded a 206Pb/238U age of 405 Ma (CK70–25) and the rim a 206Pb/238U age of 158 Ma

(CK70–26). A total of 13 analyses of zircons from sample CK135 yielded a weighted mean 206Pb/238U

age of 158 ± 2 Ma (2; MSWD = 0.81). One of the zircons from this sample

has a core–rim structure where the core yielded a 206Pb/238U age of 1476 Ma (CK135– 1) and the rim yielded a 206Pb/238U ages of 158 Ma (CK135–2). A further four analyses of three zircons from this sample yielded 206Pb/238U ages of 603, 432, 345, and 300 Ma (CK135–12, CK135–8, CK135–6, CK135–5, respectively), where the age of 300 Ma represents the minimum age of inherited zircons in this intrusion.

5.2. Whole-rock major and trace elements 5.2.1. Evaluation of the effects of hydrothermal alteration The porphyries in Chuankeng record variable degrees of hydrothermal alteration (Fig. 3). Previous research in this area indicates that Ca, Na, and the large ion lithophile elements (LILE; e.g., Sr, Ba, Pb, and Rb) are generally mobile during this type of alteration, whereas some major elements (e.g., Ti, Al, and P) and the high field strength elements (HFSE) are essentially immobile (Smith and Smith 1976). Magnesium is also easily transported in solution, and concentrations of Mg within some mafic rocks containing olivine and pyroxene show a decrease during alteration. However, Mg behaves differently in intermediate–felsic rocks, tending to be immobile primarily as a result of a lack of olivine and pyroxene (Smith and Smith 1976; Wang et al., 2015; 2018). Consequently, we focus on immobile elements such as TiO2 and MgO, the HFSE (e.g., Zr, Nb, Ta, and Hf), the REE, and isotopic data (e.g., Nd) to interpret the

geochemical data of the weakly altered igneous rock samples.

5.2.2. Major and trace elements Granodiorite porphyries in the Chuankeng deposit display intermediate to felsic compositions with 61.9–66.4 wt. % SiO2 (normalized to 100% volatile-free compositions), and are classified as calc-alkaline (Fig. 5). They also contain relatively high concentrations of MgO (2.6–3.3 wt. %), Cr (30.4–72.7 ppm), and Ni (14.4–46.9 ppm; Fig. 6; Table 2). The Chuankeng porphyries are enriched in the light rare-earth elements (LREEs) and the LILE (e.g., Sr and Th), and are depleted in the heavy rare-earth elements (HREEs) and the HFSE (e.g., Nb, Ta and Ti; Fig. 7), indicating arc-like characteristics. The samples have (La/Yb)N ratios of 4–14 and are generally free of Eu anomalies. These porphyries also contain high concentrations of Sr (556–1514 ppm) and low concentrations of Y (<13 ppm), have high Sr/Y ratios (59 to 135), and are classified as adakitic rocks in Y vs. Sr/Y and (La/Yb)N vs. YbN diagrams (Fig. 8). Granodiorite porphyries in the Dexing deposit are calc-alkaline and have a wider range of SiO2 contents (61.9–70.1 wt. %) than those in the Chuankeng deposit. The Dexing granodiorite porphyries also have similar trace element and REE patterns to the Chuankeng granodiorite porphyries.

5.3 Whole rock Sr–Nd isotopes The whole-rock Sr and Nd isotopic compositions of the granodiorite porphyries in

Chuankeng are given in Table 3. The initial

87Sr/86Sr

values (0.7076–0.7078) of the

Chuankeng porphyries are similar to those of the Dexing porphyries (0.7044–0.7089). However, the Nd (t) values (–4.5 to –4.9) of the Chuankeng porphyries are clearly lower than those of the Dexing porphyries (–1.9 to +0.6), but higher those of the Darongshan granites derived from the partial melting of Paleoproterozoic ancient crust (Fig. 9).

5.4 Zircon Hf isotopes Table 4 lists the results of 35 Hf isotopic analyses of zircons from granodiorite porphyries in Chuankeng (samples CK70 and CK135). A total of 33 zircons with ages of ca. 161–158 Ma yield 176Hf/177Hf values from 0.282488 to 0.282695, associated Hf (t) values from –2.6 to +0.9 (average = –1.2), and two-stage Hf model ages (TDM2) of 1.4–1.1 Ga (Fig. 10). The remaining two inherited zircons yield Hf (t = 300 and t = 604 Ma) values of –6.4 and –3.1, and two-stage Hf model ages (TDM2) of 1.6 and 1.4 Ga, respectively. In comparison, zircons from the granodiorite porphyries in Dexing have more depleted Hf (t) values (+1 to +7) (Fig. 11).

5.5. Zircon trace element compositions and Ti-in-zircon temperatures The trace element compositions of the zircons from the granodiorite porphyries in Chuankeng (samples CK70 and CK135) are given in Table 5. All of these zircons have chondrite-normalized patterns that are depleted in the light REE (LREE), enriched in the heavy REE (HREE), and show positive Ce but variably negative Eu anomalies (Fig. 12A). Zircons from sample CK70 have ΣREE values of 343–1012 ppm (average of 585

ppm) and zircons from sample CK135 have ΣREE values of 253–908 ppm (average of 552 ppm). Samples CK70 and CK135 have calculated Ce4+/Ce3+ ratios of 119–423 (average of 246) and 194–399 (average of 244), respectively. They have EuN/EuN* ratios that are generally >0.5 (0.63–0.82 with an average of 0.72 and 0.56–0.84 with an average of 0.63, respectively). Zircons from these samples show Ce/Nd ratios from 10.6 to 24.1 (average of 16.8) and from 10.6 to 22.2 (average of 17.3). These zircons have smaller Ce anomalies and higher Ce4+/Ce3+ and Ce/Nd ratios than those from the ore-related intrusions in the Dexing deposit. In addition, in EuN/EuN* vs. Ce4+/Ce3+ and Ce/Nd/ vs. U/Th diagrams, they plot above zircons from barren magmatic rocks within the adjacent Yongping area but below zircons from ore-related intrusions in Dexing (Fig. 12B–C). The temperatures of the melts that formed these zircons were determined using the revised Ti-in-zircon thermometer of Ferry and Watson (2007). Given that quartz is one of the dominant phenocryst and groundmass phases in all of the samples, we used a silica activity value of 1 in the calculations. Additionally, due to the absence of rutile, the activity of titanium has been conservatively estimated to be 0.7. These calculations yielded temperatures of 637C–778C (average of 724C) and 696C–827C (average of 745C) for samples CK70 and CK135, respectively (Table 5), with the lower parts of these temperature ranges overlapping with the range of temperatures calculated for the ore-related intrusions in the Dexing deposit (627C–702C with an average of 672C; Fig. 12D).

6. Discussion 6.1. Petrogenesis of the porphyries in the Chuankeng deposit Granodiorite porphyries of the Chuankeng deposit are calc-alkaline rocks with moderate SiO2 contents (61.9–66.1 wt. %) and high MgO contents (2.6–3.3wt. %) (Fig. 5 and Fig. 6). They are enriched in LILE (Sr and Th) and LREEs, depleted in HFSEs (Nb, Ta and Ti) and HREEs, and have no evident Eu anomalies (Fig. 7A, B), all of which indicate an arc-type affinity. These intrusions also have high Sr contents (556– 1514 ppm), and low Y (<12.2 ppm) and Yb (<0.9 ppm) contents, with high Sr/Y (72– 136) and LaN/YbN (19–38) ratios (Fig. 8), indicating an adakitic affinity. Several models have been proposed to explain the origin of adakitic rocks, including derivation from: (1) low-degree partial melting of metasomatized lithosphere mantle (Jiang et al., 2006), or parental basaltic magmas that have undergone assimilation–fractional crystallization (AFC) processes (Castillo, 1999; Macpherson et al., 2006); (2) melting of subducted slab material that interacted with mantle peridotite (Defant and Drummond, 1990; Martin et al., 2005); (3) partial melting of thickened continental crust (Chung et al., 2003; Xiong et al., 2003; Wang et al., 2012a); or (4) partial melting of delaminated lower continental crust (Xu et al., 2002; Wang et al., 2015). It has been suggested that magmas generated by low-degree partial melting of a metasomatically enriched lithospheric mantle can produce rocks with adakitic signatures (Jiang et al., 2006). However, that process typically generates shoshonitic rocks rather than calc-alkaline igneous rocks as occur in Chuankeng, precluding such a

mechanism for the Chuankeng porphyries (Fig. 5). Additionally, parental basaltic magmas that have undergone AFC processes could produce rocks with adakitic signatures (Castillo, 1999; Macpherson et al., 2006), but the Chuankeng porphyries show a partial melting trend in (La/Sm)–Sm and (Zr/Nb)–Nb diagrams (Fig. 13), suggesting that partial melting was more important in their formation than fractional crystallization. Furthermore, the study area does not contain sufficient volumes of mafic rocks for an AFC model of the petrogenesis of Chuankeng porphyries to be appropriate. Alternatively, the Chuankeng porphyries may have been formed by partial melting of subducted slab with a contribution of the asthenospheric mantle wedge materials (Rapp et al., 1999). Adakitic rocks formed in subduction zones commonly coexist with mantle-derived rocks (Martin et al., 2005), but the lack of typical Jurassic arc rocks is inconsistent with a Jurassic subduction-related tectonic setting in the QHMB (Wang et al., 2016). Moreover, these samples also have lower Nd (t) and higher initial 87Sr/86Sr ratios than adakitic rocks generated by partial melting of oceanic crustal material, but are isotopically similar to melts derived from the lower continental crust (Fig. 9). It follows that the Chuankeng porphyries were not generated through partial melting of a subducted slab. Adakitic rocks may be formed by direct partial melting of basaltic thickened lower crust (Zhao and Zhou, 2008; Wang et al., 2012a), with melts so formed having relatively low MgO, Cr, and Ni contents, as indicated by the experimental melting of metabasalts and eclogites at pressures of 1.0–4.0 GPa (Rapp and Watson, 1995; Rapp et al., 1999). This is inconsistent with the high MgO (2.6–3.3 wt. %), Cr (30.4–72.7

ppm), and Ni (14.4–46.9 ppm) contents of the Chuankeng porphyries (Table 2; Fig. 6), precluding this process as well. Considering their high MgO concentrations and Sr/Y ratios, the most likely genetic model for the Chuankeng granodiorite porphyries is partial melting of delaminated lower continental crustal materials, as suggested for the Dexing granodiorite porphyries (Wang et al., 2015). Kay et al. (1993) suggested that this process would add MgO, Ni, and Cr to felsic melts through interaction with mantle peridotite material during ascent. The high Sr/Y nature of the Chuankeng porphyries has been explained by deep, high pressure partial melting condition for delaminated lower crustal material, with such a magma source yielding a garnet-bearing but plagioclase-free residuum after partial melting to form adakitic melts (Rapp and Watson, 1995; Weber et al., 2002; Annen et al., 2006).

6.2. Constraints on the magma source It is generally considered that Yanshanian magmatism in South China was related to subduction of the Paleo-Pacific Plate with at least two competing tectonic models having been proposed involving: subduction environments (Li and Li, 2007; Sun et al., 2010; Zhang et al., 2017b) or intra-plate extension in response to far-field effects of subduction (Li et al., 2003; Wang et al., 2012a, 2015, 2016; Chen et al., 2017b; Xu et al., 2017). Li and Li, (2007) proposed a flat-slab subduction model, with subduction of the Paleo-Pacific Plate leading to a Triassic orogeny and subsequent slab break-off causing vast Jurassic magmatism in the interior of South China. A ridge subduction

model was recently proposed by Zhao et al. (2017b), with the closure of paleo-Tethys Ocean and subduction of the Paleo-Pacific Plate producing local extensional environments in the Late Triassic and slab break-off along the subducted mid-ocean ridge producing Jurassic granites in inland area of South China. If such slab break-off or mid-ocean-ridge subduction occurred during the Jurassic, a suite of arc-like rocks would be expected, but no subduction-related arc magmatism has been observed in the interior of South China Block. However, Wang et al. (2016) have systematically collected the published reliable data of volcanic rocks in the coastal region in South China and suggested that 170–140 Ma arc-type igneous rocks do not occur in the QinHang belt. In addition, the Jurassic intra-plate alkaline basalts, bimodal volcanic– intrusive complexes and A-type granites were produced in the interior part of South China (Li et al., 2003, 2007b; Wang et al., 2003; He et al., 2010). It seems reasonable to infer that the QHMB was in an intra-continental extensional tectonic setting in the Jurassic. The Chuankeng granodiorite porphyries in QHMB were emplaced during Middle-Late Jurassic (ca. 161–158 Ma), but display signatures of arc magmas, so an explanation of such characteristics is required. Recent studies have suggest that the remarkable growth of late Meoproterozoic to early Neoproterozoic juvenile crust along the suture zone of Yangtze and Cathaysia blocks during the Jiangnan orogeny (Wu et al., 2006; Zheng et al., 2008; Wang et al., 2012b, 2018). A suite of Neoproterozoic juvenile arc magmatic rocks that formed along the Jiangshao Fault as a result of oceanic subduction during the early Neoproterozoic also

has

been

distinguished,

showing

depleted

Hf

isotopic

composition,

Mesoproterozoic Hf model ages (1.1–0.9 Ga), and arc-related trace-element features (e.g., the Shuangxiwu and Chencai groups; Li et al., 2009; Yao et al., 2013; Zhang et al., 2018a). The Dexing granodiorite porphyries are enriched in LREEs and LILEs, with depleted Nb, Ta, and Ti, similar to the trace-element signatures of arc magmatic rocks of the Shuangxiwu Group (Wang et al., 2015; Zhang et al., 2018a). The porphyries also have positive zircon εHf(t) values (2–7, average=4.6) and stage model ages of 1000–800 Ma, implying that source rocks were derived from depleted mantle during the early Neoproterozoic (Hou et al., 2013; Wang et al., 2015). Furthermore, the consistency of Nd and Hf isotopic compositions between Dexing granodiorite porphyries and Shuangxiwu rocks suggests that Neoproterozoic juvenile crustal material could have been a source (Wang et al., 2015). The proximity of the Chuankeng and Dexing granodiorite porphyries and their similar arc-magma geochemical signatures imply that igneous rocks of both deposits have close genetic relationships with Neoproterozoic juvenile crustal material (Zhou et al., 2009; Wang et al., 2014d, 2017). Therefore, the typical arc-like characteristic of porphyries in the Chuankeng deposit may be inherited from the juvenile continental crust produced during the oceanic subduction between the Yangtze and Cathaysia Blocks. The Chuankeng porphyries have lower εNd(t) and εHf(t) values than the Dexing porphyries (Figs 9 and 11; Wang et al., 2015), indicating that a much older crustal endmember is required. The Chuankeng deposit is located at the south of Jiangshao Fault and near the northwestern margin of Cathaysia Block, where the Paleoproterozoic ancient crust are distributed (Yu et al., 2009, 2010), thus we speculate older crustal

material may be Paleoproterozoic ancient crust. Moreover, regional basement rocks of the Zhoutan Group contain both Neoproterozoic juvenile crustal materials and Paleoproterozoic ancient crustal materials (Li et al., 2011; Wang et al., 2013c). The Zhoutan Group is also proximal to the Chuankeng deposit, implying that the underlying juvenile and ancient crustal materials may be the source of the Chuankeng granodiorite porphyries. To constrain the amount of the Paleoproterozoic ancient crustal components, a simple two-endmember mixing model based on SiO2, MgO content and εNd(t) values were considered. Calculation results indicate that 20–40% of ancient crustal components were involved in the magma source of the Chuankeng porphyries (Fig. 14).

6.3. Porphyry fertility in the Chuankeng and Dexing deposits The generation of an economic deposit is controlled by a number of factors including oxidation state, water content and magma source (Cooke, 2005; Richards, 2011; Richards et al., 2012; Wang et al., 2014a, b). These factors were compared between granodiorite porphyries of the Chuankeng and Dexing deposits to elucidate their distinct geochemical characteristics and mineralization scales. Redox state of magma plays an important role in the formation of porphyry–skarn Cu mineralization (Mungall, 2002; Richards, 2009). The fertility of magma is usually attributed to the sulfophile features of Cu, which is controlled by sulfide stability and is thus affected by the oxidation state (Jugo et al., 2005; Sun et al., 2013; Zhang et al., 2017a). The high oxygen fugacity would promote the destruction of sulfide and increase

the initial copper content in source. At the same time, sulfate is the dominant sulfur species in the oxidized magma, where the sulfide is in the unsaturated state, resulting in the high Cu concentrations in the evolved magma (Botcharnikov et al., 2011; Lee et al., 2012; Sun et al., 2015). Zircon Ce4+/Ce3+ ratio is commonly used as a proxy for oxidation state of magmatic rocks (Ballard et al., 2002; Muñoz et al., 2012; Burnham et al., 2012; Chelle– Michou et al., 2014). Granodiorite porphyries related to Cu mineralization in the Dexing deposit are oxidized, with high zircon Ce4+/Ce3+ ratios of 226–877 (average 574; Zhang et al., 2017a), similar to porphyries in the Chuquicamata–El Abra porphyry Cu mine of northern Chile and in the Yulong Cu district of Tibet (Ballard et al., 2002; Liang et al., 2006). Chuankeng granodiorite porphyries have moderate zircon Ce4+/Ce3+ values of 71–423 (average of 243) (Fig. 12B), indicating that they are less oxidized than those of the Dexing deposit. Zircon Ce/Nd ratios can also indicate oxidation state (Chelle–Michou et al., 2014; Zhang et al., 2017a), with those of the Chuankeng deposit (8–24; average 23) being lower than those of the Dexing deposit (Fig. 12C), further suggesting that Chuankeng porphyries are less oxidized. Such a lower oxygen fugacity in the Chuankeng deposit would not have been conducive to the decomposition of sulfide and would therefore have reduced the initial Cu content of the source magma. It would also have led to sulfide saturation and removal of Cu from the melt. This may explain the lower degree of Cu mineralization in the Chuankeng deposit. Water contents of the parent magma affects aqueous saturation of magmas at shallow crustal levels and may increase the Cu content of the melt (Sillitoe, 2010;

Zheng et al., 2019). The occurrence of amphibole phenocrysts in the Chuankeng and Dexing porphyries indicates that the magmas related to the Cu mineralization contained >4% H2O (Ridolfi et al., 2010; Jiang et al., 2018). However, the zircons from Chuankeng porphyries yield higher Ti-in-zircon temperatures than those of the Dexing porphyries, indicating that the former have higher crystallization temperatures . Solidus temperatures of rocks may be reduced by decompression or addition of water to the magmatic system (Wang et al., 2013a). The similar porphyry Sr/Y ratios of the Chuankeng and Dexing deposits indicate that their porphyry formation pressures were similar. We therefore infer that parental magma of the Chuankeng porphyries had a lower water content, resulting in higher Ti-in-zircon temperatures, which were not conducive to the exsolution of a water-rich volatile phase and the formation of Cu mineralization. Different magma sources may also influence the initial Cu content (Zhang et al., 2017a). Here, elemental and isotopic signatures indicate that the Dexing porphyries may have been formed through partial melting of Neoproterozoic juvenile crust. Juvenile crust that formed during Neoproterozoic subduction was enriched in Cu-rich sulfides, providing Cu for the Middle Jurassic Dexing Cu mineralization (Wang et al., 2012a, 2015, 2018). Recent studies of porphyry Cu deposits in North America and Tibet have also indicated the major contribution of juvenile lower crust to Cu mineralization (Sillitoe et al., 2014; Hou et al., 2015a). Granodiorite porphyries of the Chuankeng and Dexing deposits have parallel trace element and REE patterns (Fig. 7), but the former have more enriched Sr-Nd-Hf isotopic characteristics (Figs 9 and 11). This indicates

that magma source involved more ancient recycled crust compared with the Dexing deposit. The Cu isotopic compositions of barren adakite-like intrusions derived from ancient materials in Tibet indicate the ancient crust is commonly depleted in Cu (Zheng et al., 2019). The involvement of more ancient crustal material in the Chuankeng deposit may therefore have reduced the Cu content in the magma source, reducing the small-scale Cu mineralization in Chuankeng. Furthermore, ancient crust is generally reduced and dry (Tomkins et al., 2012; Hou et al., 2015b), so its involvement may be responsible for the lower oxygen fugacity and water content of the Chuankeng porphyries. This is consistent with results of recent studies of porphyry Cu systems in Tibet, which indicate that ore-barren magmatic rocks derived from a source region dominated by ancient recycled materials have lower oxygen fugacities and water contents (Zheng et al., 2019; Chen et al., 2019). In summary, lower oxygen fugacity and water contents and more ancient crust in the source are not conducive to the formation of Cu-fertile magma, which may explain the relatively smaller scale of mineralization in Chuankeng. In addition, we suggest the whole-rock Nd and zircon Hf isotopic and trace-element compositions can thus be used together to assess the potential for Cu mineralization.

6.4. Geodynamic model Subduction of the Paleo-Pacific Plate may have been initiated during the Early Jurassic, as indicated by the occurrence of 198–187 Ma arc-related granitoid suites in the East China Sea and Taiwan, and Jurassic accretionary complexes from SW Japan

and East Taiwan to the western Philippines (Xu et al., 2017; Yui et al., 2009, 2017). Seismic reflection data indicate that South China underwent long-wavelength crustal shortening during the Early–Middle Jurassic (190–173 Ma), with compressional forces being exerted by the subducted oceanic lithosphere (Li et al., 2018). Such stresses may have been rapidly propagated to inland areas of South China, reactivating pre-existing deep faults (Cai, 2013). The reactivation of deep faults would have led to localized intra-plate extension that may have allowed asthenospheric mantle upwelling and decompression melting to occur. As a consequence, Jurassic intra-plate alkaline basalts, bimodal volcanic–intrusive complexes, and A-type granites were produced in the interior of South China (Li et al., 2003, 2007b; Wang et al., 2003; He et al., 2010). At the same time, numerous felsic porphyries were generated along the Jiangshao Fault. Considering the Neoproterozoic oceanic crust subduction between Yangtze Block and Cathaysia Block and the occurrence of Dexing and Chuankeng Jurassic adakitic rocks along the Jiangshao Fault (Wang et al., 2007; Zhou et al., 2009; Zhao et al., 2011), We propose a simplified genetic model for these Jurassic rocks (Fig. 15), which can be summarized as follows. Stage1: In the Neoproterozoic, oceanic crust subduction occurred between the Yangtze and Cathaysia blocks (Fig. 15A; Wu et al., 2006; Wang et al., 2012b). During this process, the island-arc magmatism and related volcanogenic massive sulfide (VMS-style) Cu mineralization were generated at Shuangxiwu and Tieshajie in the Jiangnan orogen (Zhou et al., 2002; Chen et al., 2014; Wang et al., 2018). The generated Neoproterozoic arc magma may have been less oxidized owning to crustal interaction (Hildreth and Moorbath, 1988; Zhang et al., 2017a), resulting in

sulfide saturation that would have stripped Cu and Au from the melt, and leaving residual cumulate minerals in the deep lower crust and forming the Cu-rich juvenile crust along the suture zone of the Yangtze and Cathaysia blocks (Richards, 2009, 2011). Stage 2: During the Middle to Late Jurassic, the localized intra-continental localized lithospheric extension took place along the Jiangshao Fault in response to far-field compression stress from the subduction of the Paleo-Pacific Plate (Zhou et al., 2006; Wang et al., 2012a, 2015; Li et al., 2018). This may have led to delamination of the resulting thickened crust in the Early-Middle Jurassic, allowing upwelling of asthenospheric melt and providing heat to trigger partial melting of delaminated thickened juvenile crust (Fig. 15B). The Dexing porphyries were derived from a source comprising predominantly Neoproterozoic Cu-rich juvenile crustal materials, whereas the Chuankeng porphyries originated from Neoproterozoic Cu-rich juvenile crustal materials with some input of Cu-depleted Paleoproterozoic crustal materials.

7. Conclusions (1) Zircon LA–ICP–MS U–Pb dating of granodiorite porphyries in the Chuankeng Cu deposit indicates that the deposit formed in an extensional tectonic setting in the continental interior at 161–158 Ma. (2) The porphyries in the Chuankeng deposit were generated by partial melting of delaminated Neoproterozoic juvenile crust with involvement of Paleoproterozoic ancient crustal materials. (3) Lower magmatic oxygen fugacity and water contents of porphyries and involvement

of ancient recycled crust in the magma source made the Chuankeng deposit less economic than the Dexing deposit (4) Whole-rock Nd and zircon Hf isotopic and trace-element compositions can be used together to assess potential Cu mineralization.

Acknowledgements We thank Tao Wei, Zheng Liu and Yingwen Wei for assistance during fieldwork. Professor Xiaolei Wang is specially thanked for the constructive suggestions on the early version of the manuscript. This research was financially supported by the Ministry of Science and Technology of the People’s Republic of China (Grant No. 2016YFC0600206), the National Natural Science Foundation of China (Grant No. 41772063), and the Fundamental Research Funds for the Central Universities (Grant No. 020614380065).

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Neoproterozoic (ca. 900 Ma) high-grade metamorphism and continental arc formation in the southern Beishan Orogen, southern Central Asian Orogenic Belt (CAOB). Precambrian Research 290, 32–48. Figure captions Fig. 1. Simplified map showing the tectonic framework of the Qin-Hang belt as well as major faults and deposits. The inset is the sketch tectonic map of China.

Fig. 2. Geological map of the Chuankeng copper deposit.

Fig. 3. Representative hand specimens and photomicrographs of the granodiorite porphyries in the Chuankeng deposit. (A, C) Hand specimens of samples CK70 and CK135 from Chuankeng granodiorite porphyries (B, D) Photomicrographs showing the mineralogy of the two porphyries samples from the study area; cross-polarized light. (E) the contact of the granodiorite porphyry with wall rock, and the impure carbonate units are turned into hornfels (F) the calcium wall rock is altered into marble during the thermal

metamorphism

(G)

retrograde

alteration,

epidote-magnetite-pyrite-

chalcopyrite overprint the earlier garnet; sample (H) retrograde alteration, chloride– magnetite–sphalerite overprint the earlier garnet; plane polarized light. (I) the magnetite, hematite and the pyrite replace the garnet (J) Chalcopyrite and pyrite in quartz vein; reflected light. Abbreviations: Bi= biotite, Pl= plagioclase, Amp= Amphibole, Qtz= quartz; Grt= garnet; Epi= Episode; Chl= chlorite; Mt= magnetite; Hem= hematite; Py= pyrite; Ccp= Chalcopyrite; Sp= sphalerite

Fig. 4. Representative CL images and Wetherill concordia diagrams (A–C), and corrected weighted mean 206Pb/238U ages (B–D) for zircons within samples CK70 and CK135 from porphyries in the Chuankeng deposit (uncertainties are given as 2).

Fig. 5. Zr/TiO2 vs. SiO2 classification diagram (after Winchester and Floyd, 1977) for porphyries from the Chuankeng and Dexing deposits. The data for the ore-related porphyries at the Dexing deposit are from Wang et al. (2006, 2015).

Fig. 6. MgO vs. SiO2 diagram for porphyries from the Chuankeng and Dexing deposits. Data for porphyries at the Dexing deposit are from Wang et al. (2006, 2015).

Fig. 7. (A) Chondrite-normalized REE and (B) primitive-mantle-normalized multielement patterns for porphyries in the Chuankeng and Dexing deposits. Red lines represent porphyries in Chuankeng and gray fields represent the compositions of porphyries in Dexing (Wang et al., 2015). Normalizing values from Sun and McDonough (1989).

Fig. 8. Trace element diagrams for porphyries in the Chuankeng and Dexing deposits. (A) LaN/YbN vs. YbN diagram, normalized to chondrite from Sun and McDonough (1989). (B) Sr/Y vs. Y diagram, including the adakite-like rock field of Defant and Drummond (1990). Data for the ore-related porphyries at Dexing are from Wang et al.

(2006, 2015).

Fig. 9. Nd (t) vs. (87Sr/86Sr)i diagram showing variations in the isotopic composition of porphyries in the Chuankeng deposit (this study) and the Dexing deposit. Data source are as follows: Cenozoic subducted oceanic crust-derived adakites; 400–179 Ma MORB; and Dexing adakitic rocks from Wang et al. (2006, 2015); data for Darongshan granites derived from the pre-Cambrian ancient crust from Qi et al., (2007).

Fig. 10. Histograms of in situ zircon Hf (t) values and two-stage Hf model ages showing variations in zircons from porphyries in the Chuankeng copper deposit. Trace element characteristics of zircons from porphyries in the Chuankeng and Dexing deposits.

Fig. 11. Hf (t) vs. U–Pb age diagram for zircons from porphyries in the Chuankeng and Dexing deposits. Crustal extraction lines were calculated using a

176Lu/177Hf

ratio of

0.015 to represent the average continental crust (Griffin et al., 2002). Data for the magmatic rocks of Shuangxiwu, Chencai, and Zhoutan groups are from Li et al. (2009), Yao et al. (2013), and Li et al. (2011) respectively, and data for the Dexing deposit are from Wang et al (2015).

Fig. 12. (A) REE variation diagram normalized to the chondrite composition of Sun and McDonough (1989). (B) EuN/EuN* vs. Ce4+/Ce3+ diagram. (C) Ce/Nd vs. U/Th

diagram. (D) Th/U vs. Tti–zr (°C) diagram. Data for ore-related porphyries at the Dexing deposit are from Zhang et al. (2017b), data for the barren magmatic rocks at Yongping are from Zhang et al. (2018), and data for mineralized and barren porphyries in northern Chile are from Ballard et al. (2002).

Fig. 13. Partial melting trend for porphyries in the Chuankeng deposit (A) La/Sm vs Sm. (B) Zr/Nb vs Nb.

Fig.14. Calculation result of direct magma mixing model, (A) based on the SiO2 contents and εNd(t) values (B) based on the SiO2 contents and εNd(t) values. Hypothesis about this calculation is complete mixing between two end-members (Neoproterozoic juvenile lower crust and Paleoproterozoic ancient lower crust). The Neoproterozoic juvenile lower crust end-member is represented by the porphyries at Dexing (Liu et al., 2012; Wang et al., 2015); The Paleoproterozoic ancient lower crust end-member is represented by the Lapu granites (Liu et al., 2005).

Fig. 15. Model showing the genesis of the Chuankeng and Dexing copper deposits. (A) Neoproterozoic subduction of oceanic crust between the Yangtze and Cathaysia blocks caused extensive island arc-type magmatism and the formation of Cu-rich Neoproterozoic juvenile crust. (B) In the Jurassic, delamination of the lower part of over-thickened lower crust adjacent to the Jiangshao fault enabled the upwelling of asthenospheric material. The porphyries at the giant Dexing deposit are derived from a

magma source dominated by the Neoproterozoic juvenile crustal materials. In comparison, porphyries in the small-scale Chuankeng deposit are derived from the partial melting of Neoproterozoic juvenile crustal material along with Paleoproterozoic ancient crustal materials. Table captions Table 1. Results of LA-ICP-MS zircon U–Pb dating of porphyries in the Chuankeng deposit.

Table 2. Whole-rock geochemical data for porphyries in the Chuankeng deposit.

Table 3. Sr–Nd isotopic compositions of porphyries in the Chuankeng deposit.

Table 4. In situ zircon Hf isotopic data for porphyries in the Chuankeng deposit.

Table 5. Zircon trace element compositions, Ce and Eu anomalies, and Ti-in-zircon temperatures for porphyries in the Chuankeng deposit.

Table 1 Results of LA-ICP-MS zircon U–Pb dating of porphyries in the Chuankeng deposit. Sp ot

Th

U

Th/

207Pb/

ppm

ppm

U

206Pb

164

231

0.7

0.049

0.0

0.17

0.01

0.02

0.00

162

9

162

2

030 0.0 0 028 0.0 0 033 0.0 0 044 0.0 0 030 0.0 0 045 0.0 0 036 0.0 0 058 0.0 0 053 0.0 0 059 0.0 0 027 0.0 0 030 0.0 0 029 0.0 0 039 0.0 0 069 0.0 0 050 0.0 0 037 0.0 0 061 0.0 0 070

270 0.18

000 0.00

550 0.02

040 0.00

170

8

162

2

180 0.17

970 0.01

540 0.02

040 0.00

163

9

160

3

460 0.16

060 0.01

520 0.02

040 0.00

159

12

160

3

980 0.17

390 0.00

510 0.02

050 0.00

165

8

162

2

620 0.18

980 0.01

540 0.02

040 0.00

169

11

161

3

120 0.17

340 0.01

530 0.02

050 0.00

166

9

160

3

720 0.16

080 0.02

520 0.02

040 0.00

153

18

157

4

220 0.16

050 0.01

470 0.02

060 0.00

158

13

159

3

890 0.16

460 0.01

500 0.02

050 0.00

156

12

162

4

590 0.16

390 0.00

550 0.02

060 0.00

153

8

160

2

260 0.17

950 0.00

520 0.02

040 0.00

160

8

161

2

110 0.17

910 0.00

520 0.02

040 0.00

164

8

160

3

580 0.16

950 0.01

520 0.02

040 0.00

158

9

156

3

810 0.18

080 0.01

450 0.02

040 0.00

169

15

166

5

070 0.16

730 0.01

610 0.02

080 0.00

158

13

161

3

820 0.16

470 0.01

530 0.02

050 0.00

159

10

159

3

900 0.16

150 0.01

490 0.02

050 0.00

155

14

160

4

460 0.16

660 0.01

520 0.02

070 0.00

820

710

490

060

158

15

158

4

1σ

207Pb

/235U

1σ

206Pb

/238U

1σ

207Pb

/235U

1σ

206Pb/2 38U

1σ

Ck70 1 22 3 3 4 4 5 56

154

264

0.6

20 0.051

132

196

0.7

70 0.051

116

113

1.0

40 0.049

117

221

0.5

30 0.050

67

94

109

0.9

10 0.053

78 9 8 10 9 11 10 12 11 13

98

168

0.6

00 0.051

123

106

1.2

50 0.048

91

110

0.8

40 0.051

56

64

0.9

00 0.048

131

224

0.6

90 0.046

14 12

258

317

0.8

20 0.049

15 13 16 14 17 15 18 16 19

286

201

1.4

70 0.050

158

134

1.2

90 0.050

20 17

39

46

0.9

10 0.056

129

84

1.5

00 0.049

1.0

80 0.049

1.0

20 0.048

118

21 18 22

62

23 19 24

56

25 20 261 21 22

117 64

58

1.0

70 0.053 70

193

140

1.4

0.051

0.0

0.17

0.01

0.02

0.00

164

9

163

3

102

95

1.1

30 0.051

520 0.17

030 0.01

550 0.02

050 0.00

163

12

163

3

195

149

1.3

20 0.049

470 0.16

410 0.01

570 0.02

060 0.00

157

9

157

3

690 0.17

050 0.01

470 0.02

040 0.00

166

11

162

3

720 0.16

220 0.01

550 0.02

050 0.00

156

14

164

4

640 0.18

620 0.01

570 0.02

060 0.00

170

10

158

3

228 0.50

204 0.01

486 0.06

048 0.00

413

12

405

6

10

033 0.0 0 046 0.0 0 036 0.0 0 043 0.0 0 056 0.0 0 037 0.0 5 020

220

830

490

110

0 0.0

0.16

0.01

0.02

0.00

153

13

152

3

278 0.16

469 0.01

380 0.02

050 0.00

158

9

157

3

876 0.17

055 0.01

465 0.02

050 0.00

163

11

161

3

417

290

532

051

23

143

137

1.0

60 0.052

24

61

63

1.0

30 0.047

1.1

30 0.053

0.3

05 0.056

25 26

0

115 57

107 215

CK135 1

190

111

1.7

0.051

2

305

177

1.7

27 0.050

3

218

131

1.7

56 0.050 99

053 0.0 9 036 0.0 6 042 9

4

245

163

1.5

0.049

0.0

0.16

0.01

0.02

0.00

155

9

155

3

038 0.0 0 034 0.0 8 039 0.0 3 046 0.0 0 037 0.0 0 034 0.0 7 031 0.0 9 029 0.0 2 030 0.0 9 039 0.0 1 046 0.0 4 024 0.0 1 015 0.0 9 022 0.0 3 026

533 0.17

047 0.01

429 0.02

043 0.00

165

9

160

3

612 0.16

090 0.01

513 0.02

040 0.00

156

10

156

3

568 0.17

100 0.01

454 0.02

046 0.00

166

12

157

3

736 0.16

371 0.01

473 0.02

055 0.00

152

9

160

3

178 0.16

074 0.01

514 0.02

047 0.00

154

10

160

3

407 0.16

108 0.01

514 0.02

046 0.00

159

9

159

3

987 0.16

026 0.00

497 0.02

041 0.00

158

8

157

3

889 0.15

893 0.00

468 0.02

040 0.00

149

8

155

2

751 5.72

950 0.19

439 0.25

039 0.00

1934

29

1477

33

060 0.18

422 0.01

744 0.02

640 0.00

173

11

158

3

547 0.34

228 0.01

485 0.04

055 0.00

304

12

300

4

959 0.55

553 0.01

768 0.07

061 0.00

445

10

437

4

050 0.88

540 0.03

007 0.09

072 0.00

646

17

604

9

987 0.40

218 0.01

817 0.05

148 0.00

346

14

346

7

577

956

514

115

5

304

188

1.6

79 0.051

6

230

139

1.7

04 0.050

7

134

103

1.3

81 0.052

8

259

163

1.6

95 0.047

9

252

133

1.9

77 0.046

10

409

213

1.9

73 0.049

11

382

194

2.0

58 0.050

1.6

13 0.047

12

322

205

13

222

265

0.8

46 0.159

14

151

111

1.4

44 0.055

15

215

229

0.9

59 0.053

16

100

602

0.2

10 0.056

17

294

222

1.3

67 0.065

0.5

31 0.053

18

73

140

83

8

Table 2 Whole-rock geochemical data for porphyries in the Chuankeng deposit. Sam

CK

CK

CK

CK

CK

CK

CK

CK

CK

CK1

CK1

CK1

CK1

ple

25

701

702

703

704

705

706

801

802

351

352

353

354

61.3

61.8

62.6

61.7

61.1

62.5

62.1

62.7

58.3

58.3

59.4

59.3

0.73

0.68

0.68

0.67

0.66

0.64

0.70

0.66

0.79

0.78

0.79

0.77

16.1

16.1

16.1

16.6

17.0

16.5

15.6

16.2

15.9

16.0

16.4

16.5

4.43

4.49

3.94

3.94

3.97

3.58

4.64

4.46

5.08

4.98

4.80

4.77

0.03

0.03

0.03

0.03

0.03

0.03

0.03

0.03

0.04

0.04

0.03

0.03

3.13

2.68

2.93

2.44

2.44

2.40

2.68

2.56

2.77

2.87

2.65

2.61

3.10

2.69

2.93

3.17

3.37

3.24

2.59

2.56

3.33

3.40

3.14

3.12

4.36

4.24

4.28

2.57

2.35

2.83

4.21

4.51

4.95

4.97

4.57

4.57

2.51

3.07

2.97

2.17

2.32

2.04

3.02

2.67

2.55

2.57

2.77

2.77

0.28

0.27

0.27

0.27

0.27

0.26

0.27

0.26

0.32

0.32

0.32

0.31

3.41

3.45

3.03

5.99

6.35

5.97

3.78

3.21

5.07

5.10

3.92

3.92

99.1

99.3

98.7

98.6

SiO2

64. 1

TiO

0.6

2

9

Al2

16.

O3

4

Fe2

2.9

O3

7

Mn

0.0

O

2

Mg

2.7

O

2

CaO

3.2 0

Na2

3.9

O

9

K2O

2.5 7

P2O

0.2

5

6

LOI

3.0 6

Tota

99.

l

9

99.3

99.5

99.8

99.6

99.8

0

99.6

99.8

417

441

407

418

404

390

370

424

393

7

8

5

1

0

6

4

9

9

4701

4631

4639

4633

118

101

101

96

89

75

102

106

107

120

109

108

7

62.9

44.9

64.1

40.0

40.6

39.0

50.6

42.7

72.7

49.6

31.0

30.4

271

159

155

145

175

191

161

171

154

126

119

15.0

14.9

6

33.6

24.7

30.1

17.8

19.3

18.4

25.8

23.2

46.9

25.9

14.4

14.4

872

362

316

287

158

413

169

261

334

474

563

531

530

50.2

38.0

47.8

31.1

30.9

33.0

37.5

37.2

38.4

38.7

37.5

36.9

23.9

23.8

21.6

23.2

24.2

23.0

23.1

23.5

25.0

25.6

24.2

24.3

Ti V Cr Co Ni Cu Zn Ga

100.

92. 0 50.

27.

35. 6 23. 6

Rb Sr Y Zr Nb Mo Cs Ba Hf Ta Pb Th U La Ce Pr Nd Sm Eu Gd Tb Dy Ho

50. 4

55.4

63.6

58.2

62.4

60.2

44.9

46.4

45.7

45.8

111

116

119

102

121

9

5

6

556

640

694

5

4

1472

1514

1461

1472

6

10.9

10.3

10.0

9.30

8.85

8.51

10.4

10.0

12.2

12.1

10.9

10.9

123

135

128

118

128

121

135

147

126

147

152

158

158

9.91

8.69

9.75

10.1

9.46

9.45

9.25

8.60

10.1

9.98

9.18

9.12

4.76

1.91

21.6

1.11

2.55

1.36

44.4

7.76

1.16

1.02

9.16

9.28

4

2.76

3.16

2.86

5.84

5.81

5.66

3.12

3.15

2.12

2.10

2.12

2.16

103

117

119

147

114

109

9

7

8

5

213

308

221

2

8

1064

1047

1027

1011

3.47

3.36

3.12

3.42

3.25

3.61

3.72

3.25

3.80

3.82

3.88

3.90

0.94

0.92

0.91

0.91

0.92

0.88

0.98

0.93

0.86

0.83

0.56

0.58

4.84

4.89

5.54

3.98

5.12

4.47

4.80

4.97

4.35

3.38

4.86

4.97

6.33

5.49

5.40

7.05

7.00

7.25

5.51

5.85

6.40

6.48

6.14

6.25

1.12

0.78

1.09

1.12

0.97

1.08

0.83

0.77

1.47

1.38

1.36

1.42

35.4

27.0

25.0

34.3

36.8

30.2

24.0

31.0

36.6

38.5

33.7

34.0

67.4

53.3

48.5

68.1

71.3

62.6

48.6

59.6

74.5

76.7

68.8

68.8

7.42

6.03

5.59

7.33

7.61

6.48

5.62

6.54

8.78

8.89

8.04

8.15

28.5

23.8

22.6

27.7

27.8

24.8

22.8

25.3

32.5

32.5

30.5

30.5

4.80

4.20

4.05

4.66

4.56

4.21

4.10

4.27

5.58

5.50

5.16

5.24

1.23

1.24

1.17

1.23

1.20

1.13

1.22

1.23

1.52

1.52

1.45

1.47

3.56

3.24

3.13

3.39

3.26

3.07

3.14

3.18

4.12

3.96

3.76

3.77

0.47

0.41

0.41

0.43

0.42

0.39

0.41

0.41

0.54

0.53

0.49

0.49

5

2.23

2.03

2.00

1.99

1.89

1.83

2.03

1.96

2.55

2.47

2.33

2.35

0.2

0.39

0.35

0.36

0.34

0.31

0.31

0.36

0.35

0.43

0.43

0.40

0.39

824

56.9

58.4

52.2

8.4

10. 2 0.8 4 1.8

3.3 3 1.2 1 7.8 0 5.5 8 1.0 7 17. 6 35. 7 4.1 4 16. 9 3.1 9 0.9 7 2.5 1 0.3 3 1.6

9 Er Tm Yb Lu

0.7 6

1.02

0.93

0.93

0.84

0.81

0.79

0.92

0.92

1.14

1.12

1.02

1.03

0.14

0.13

0.13

0.11

0.11

0.11

0.13

0.12

0.15

0.15

0.13

0.14

0.87

0.79

0.80

0.66

0.64

0.65

0.80

0.77

0.91

0.92

0.84

0.85

0.13

0.12

0.11

0.10

0.09

0.09

0.12

0.11

0.13

0.13

0.12

0.13

154

123

115

151

157

137

114

136

169

173

157

157

0.1 0 0.6 5 0.1 0

ΣRE

84.

E

8

Table 3 Sr–Nd isotopic compositions of porphyries in the Chuankeng deposit. Sa mpl

TD 87Rb/8

87Sr/

6Sr

86Sr

e

2 σ

(87Sr/86S

147Sm

147Sm/1

r)i

/144Nd

44Nd

M2

εNd(t)

(G a)

CK

0.143

0.70

701

4

8019

CK

0.158

0.70

702

0

8182

CK

0.296

0.70

703

3

8487

CK

0.263

0.70

704

9

8222

87Rb/86Sr

5 5 9 6

0.70769

0.101

0.5123

27

99

01

0.70782

0.106

0.5122

302

67

95

0.70780

0.101

0.5123

499

54

08

0.70761

0.099

0.5123

398

11

05

1. -4.64

33 1.

-4.86

34

-4.47

31

1. 1. -4.48

32

and 147Sm/144Nd ratios are calculated using Rb, Sr, Sm, Nd contents.

(87Sr/86Sr)i=( 87Sr/86Sr)sample−(87Rb/86Sr)sample×(eλ1t−1); εNd(t)={[(143Nd/144Nd)sample−(147Sm/144Nd)sample] {[(143Nd/144Nd)

CHUR(0)

−(143Nd/144Nd)

×

(eλ2t−1)]}

/

λ t CHUR(0)]×(e 2 −1)};

TDM2=1/λ×ln{[1+((143Nd/144Nd)sample− [(147Sm/144Nd)sample−(147Sm/144Nd)c]×(eλt−1)−(143Nd/144Nd)DM ]/[((147Sm/144Nd)c−0.2136}; where t=161 Ma for granodiorite porphyry , (143Nd/144Nd)CHUR(0)= 0.512638,( 0.1967; year−1.

(147Sm/144Nd)

c

= 0.118;

(143Nd/144Nd)

DM

= 0.51315; λ1 =1.42 ×

10−11

143Nd/144Nd)

year−1;

CHUR(0)

λ2 =6.54 ×

=

10−12

Table 4. In situ zircon Hf isotopic data for porphyries in the Chuankeng deposit.

Sample

176Yb/177

Hf

176Lu/177

Hf

176Hf/177

Hf

age error

(Ma

εHf(t )

TDM 2ο

(Ga)

) CK70-1

0.017152

0.000624

0.282618

CK70-3

0.010454

0.000365

0.282632

CK70-5

0.012297

0.000439

0.282607

CK70-6

0.019866

0.000700

0.282638

CK70-8

0.009254

0.000341

0.282605

CK70-10

0.009469

0.000333

0.282617

CK70-12

0.013200

0.000457

0.282647

CK70-13

0.015537

0.000533

0.282594

CK70-15

0.014957

0.000514

0.282646

CK70-16

0.015952

0.000556

0.282630

CK70-17

0.006640

0.000221

0.282611

CK70-18

0.015156

0.000521

0.282662

CK70-19

0.014373

0.000511

0.282645

CK70-20

0.021296

0.000701

0.282601

CK70-25

0.018675

0.000624

0.282616

CK70-26

0.011664

0.000394

0.282629

CK70-28

0.012725

0.000460

0.282629

CK70-29

0.013537

0.000485

0.282641

CK70-30

0.013162

0.000454

0.282638

0.00001 6 0.00001 5 0.00001 5 0.00001 4 0.00001 6 0.00001 8 0.00001 6 0.00001 6 0.00001 7 0.00001 6 0.00001 7 0.00001 6 0.00001 7 0.00001 7 0.00001 6 0.00001 6 0.00001 7 0.00001 7 0.00001

161

-1.7

161

-1.2

161

-2.1

161

-1.0

161

-2.2

161

-1.8

161

-0.7

161

-2.6

161

-0.7

161

-1.3

161

-1.9

161

-0.2

161

-0.8

161

-2.3

161

-1.8

161

-1.3

161

-1.3

161

-0.9

161

-1.0

1

0. 6 0. 5 0. 5 0. 5 0. 6 0. 6 0. 6 0. 5 0. 6 0. 6 0. 6 0. 6 0. 6 0. 6 0. 6 0. 6 0. 6 0. 6 0.

880 854 891 853 891 875 835 911 839 862 880 816 839 905 883 860 861 844 848

TDM 2 ο

2

2ο

(Ga)

4

131

3

7

4

128

1

3

4

133

1

9

3

127

8

2

4

134

4

3

4

131

9

8

4

125

4

0

4

137

3

0

4

125

7

4

4

129

4

0

4

132

7

9

4

121

5

7

4

125

7

4

4

135

9

4

4

132

4

1

4

129

5

1

4

129

7

1

4

126

8

3

4

127

70 66 66 61 72 79 72 70 76 71 77 72 76 78 71 72 76 78 68

5 CK70-31

0.015460

0.000529

0.282650

CK70-34

0.015206

0.000513

0.282619

CK70-35

0.021744

0.000787

0.282607

CK70-36

0.015310

0.000525

0.282658

CK70-39

0.014376

0.000502

0.282640

CK135-3

0.019612

0.000713

0.282649

CK135-4

0.024550

0.000873

0.282646

CK135-5

0.013984

0.000467

0.282488

CK135-7

0.025257

0.000939

0.282695

CK135-8

0.008975

0.000305

0.282580

CK135-9

0.015472

0.000539

0.282643

0.022394

0.000762

0.282631

0.024663

0.000888

0.282631

0.013531

0.000493

0.282626

0.025423

0.000969

0.282629

0.033371

0.001064

0.282613

CK13510 CK13512 CK13515 CK13516 Ck13518

0.00001 7 0.00001 6 0.00001 8 0.00001 7 0.00001 6 0.00002 1 0.00003 3 0.00001 8 0.00002 6 0.00001 5 0.00001 7 0.00001 7 0.00001 8 0.00001 6 0.00003 1 0.00001 9

5 161

-0.6

161

-1.7

161

-2.1

161

-0.3

161

-0.9

158

-0.7

158

-0.8

158

-6.4

158

0.9

158

-3.1

158

-0.9

158

-1.4

158

-1.4

158

-1.5

158

-1.4

158

-2.0

0. 6 0. 6 0. 6 0. 6 0. 6 0. 7 1. 2

833 876 899 822 847 839 846

2

1

4

124

6

3

4

131

5

4

5

134

1

2

4

122

7

6

4

126

5

6

5

125

8

0

9

125

15

4

7

0

74 72 81 75 72 93

0.

105

4

160

6

7

9

8

7

114

11

4

8

7

4

140

1

1

4

126

6

0

4

129

6

1

5

129

0

2

4

129

6

9

8

129

13

7

5

9

5

133

3

2

0. 9 0. 5 0. 6 0. 6 0. 6 0. 6 1. 1 0. 7

779 925 842 865 868 866 872 897

80

67 74 74 79 73

84

εHf (t)=10000×{[(176Hf/177Hf)s−(176Lu/177Hf)s×(eλt−1)]/[(176Lu/177Hf)CHUR.0−(176Lu/177Hf)CHUR×(eλt−1)]−1}. TDM1=1/λ×ln{1+[(176 Hf/177Hf)s−(176Hf/177Hf)DM]/[(176Lu/177Hf)s−176Lu/177Hf)DM]}.TDM2=TDM1−(TDM−t)×[(fcc−fs)/(fcc−fDM)]. fLu/Hf=(176Lu/177Hf)S/(176Lu/177Hf) (176Hf/177Hf)

S

CHUR−1.Where,

λ=1.865 × 10−11/a (Scherer et al., 2001); (

are the measured values of the samples;(

176Lu/177Hf)

CHUR=0.0332,

176Lu/177Hf)

(176Hf/177Hf)

S

and

CHUR.0=0.282772,

(176Lu/177Hf)DM=0.0384 and(176Hf/177Hf) DM =0.28325 (Blichert-Toft and Albarede, 1997; Griffin et al., 2000); (176Lu/177Hf)mean

crust=0.015.

fcc=[(

176Lu/177Hf)mean

crust/(

fDM=[(176Lu/177Hf)DM/(176Lu/177Hf) CHUR]–1; t=crystallization time of zircon.

176Lu/177Hf)

CHUR]−1;

fs=fLu/Hf;

Table 5 Zircon trace element compositions, Ce and Eu anomalies, and Ti-in-zircon temperatures for porphyries in the Chuankeng deposit. Sample

Th

U

Ti

La

Ce

Pr

Nd

Sm

Eu

Gd

Tb

Dy

Ho

Er

Tm

Yb

Lu

ΣREE

Eu/Eu*

Ce4+/Ce3+

Ce/Nd

T℃

CK70-1

164

231

6.20

0.068

25.4

0.11

1.05

2.97

2.04

19.7

6.30

70.2

25.9

115

27.4

297

53.4

646

0.82

388

24.1

735

CK70-2

110

137

7.73

0.009

21.6

0.08

1.21

2.93

1.71

16.7

5.69

64.5

23.6

101

24.3

256

45.4

564

0.75

275

17.9

755

CK70-3

154

264

6.17

0.009

19.6

0.04

1.01

3.45

2.03

22.0

7.34

84.6

28.8

131

31.5

323

57.6

713

0.72

292

19.4

734

CK70-4

132

196

4.88

0.000

18.1

0.03

0.77

2.10

1.37

14.2

5.17

62.2

22.7

101

23.9

245

44.0

541

0.77

423

23.5

713

CK70-5

116

113

6.11

0.000

18.0

0.06

1.40

2.74

1.46

15.5

4.38

52.3

18.1

82.0

18.7

199

36.7

450

0.68

183

12.9

733

CK70-6

117

221

4.59

0.000

20.6

0.02

0.94

3.17

1.97

21.7

7.17

85.1

31.3

140

32.9

346

62.1

753

0.73

366

21.9

708

CK70-7

93.6

109

4.58

0.017

19.4

0.08

1.47

3.13

1.41

15.1

5.39

56.2

20.5

87.5

21.1

216

40.8

488

0.63

186

13.2

708

CK70-8

97.9

168

4.55

0.026

17.8

0.04

0.85

3.11

1.56

17.0

5.47

65.3

24.0

108

27.3

288

54.6

613

0.65

334

21.0

707

CK70-9

196

298

9.75

0.009

31.9

0.10

1.53

4.83

2.55

29.2

9.82

115

43.9

191

44.6

458

82.8

1015

0.66

332

20.9

778

CK70-10

131

224

4.45

0.008

24.3

0.05

1.37

3.19

2.16

21.0

7.27

86.7

32.5

144

34.5

356

66.2

779

0.81

322

17.8

705

CK70-11

258

317

6.69

0.008

40.2

0.04

2.00

4.69

3.17

30.7

10.5

121

43.2

186

43.4

447

80.3

1012

0.81

320

20.1

742

CK70-12

65.4

71.8

7.67

0.000

13.3

0.05

1.14

2.73

1.37

11.7

3.84

42.7

14.9

65.1

16.0

172

32.2

377

0.74

167

11.7

755

CK70-13

129

117

3.76

0.000

19.7

0.05

1.16

3.08

1.79

15.5

4.84

55.1

17.8

76.9

18.2

187

34.4

436

0.79

225

17.1

691

CK70-14

170

142

4.56

0.016

28.0

0.16

2.64

5.83

3.20

29.1

8.76

94.6

30.5

126

28.6

283

49.1

690

0.75

119

10.6

707

CK70-15

286

201

6.48

0.000

38.9

0.14

2.33

5.70

2.88

32.2

10.2

108

34.1

137

30.1

300

52.2

753

0.65

189

16.7

739

CK70-16

158

134

4.29

0.032

28.2

0.13

1.90

4.17

2.38

23.4

7.51

79.6

27.1

117

26.7

267

46.7

632

0.74

198

14.8

702

CK70-17

112

98

9.11

0.000

17.6

0.10

1.46

2.88

1.64

14.7

4.85

51.8

18.2

79.1

17.9

181

34.3

425

0.77

170

12.1

771

CK70-18

118

117

4.67

0.008

23.1

0.10

1.61

4.16

2.01

20.4

6.41

73.4

25.0

108

24.9

247

46.0

582

0.67

192

14.4

709

CK70-19

55.7

58.4

6.15

0.000

9.81

0.06

0.44

1.28

0.74

5.84

2.02

22.2

7.18

31.5

7.47

77.3

14.7

181

0.82

302

22.5

734

CK70-20

85.3

89.1

1.90

0.000

15.2

0.07

0.91

2.12

1.28

11.1

3.45

41.2

14.4

61.8

14.2

149

28.0

343

0.80

251

16.8

637

CK70-21

193

140

6.99

0.008

25.7

0.09

1.63

3.89

1.45

17.3

5.57

61.7

21.1

88.4

20.4

194

35.8

477

0.54

192

15.7

746

CK70-22

102

94.7

3.97

0.223

17.5

0.14

1.50

4.33

2.21

17.6

5.82

59.5

21.9

94.1

22.1

219

42.1

508

0.77

145

11.7

695

CK70-23

143

137

6.42

0.025

25.5

0.13

1.61

4.16

2.05

21.6

6.74

79.3

26.7

112

26.3

265

48.5

619

0.66

216

15.9

738

CK70-24

115

107

5.08

0.000

19.1

0.07

1.65

3.31

1.63

17.2

5.67

62.1

21.8

95.0

22.6

224

41.4

515

0.66

170

11.6

717

CK70-25

250

168

7.21

0.009

28.9

0.12

1.68

4.54

2.11

22.1

6.22

68.7

23.2

96.6

21.2

207

38.8

521

0.64

191

17.3

749

CK135-1

151

111

2.69

0.000

19.5

0.04

0.88

1.92

1.07

11.7

3.69

42.2

14.7

64.0

15.0

153

30.7

358

0.69

399

22.2

663

CK135-2

190

111

5.79

0.000

21.9

0.06

1.05

2.63

1.38

14.5

4.61

45.5

14.9

64.3

13.8

134

25.9

344

0.68

272

20.9

728

CK135-3

305

177

10.73

0.267

39.9

0.14

2.49

5.04

2.63

26.2

8.46

90.3

28.6

113

24.3

225

42.7

609

0.70

198

16.0

788

CK135-4

245

163

4.00

0.111

36.9

0.11

2.47

5.37

2.51

31.4

8.85

97.6

31.5

129

28.4

269

51.4

695

0.59

194

14.9

696

CK135-5

304

188

7.02

0.017

42.8

0.13

2.38

5.29

2.65

31.8

9.50

97.8

32.9

126

27.4

262

49.9

691

0.62

227

18.0

746

CK135-6

230

136

8.05

0.102

28.9

0.09

1.54

3.48

1.73

19.1

6.08

65.1

21.8

90.9

19.8

190

36.7

486

0.65

263

18.8

759

CK135-7

230

139

9.16

0.000

28.1

0.10

1.67

3.76

1.77

19.5

5.77

59.6

20.6

89.2

20.0

195

37.9

483

0.63

233

16.9

772

CK135-8

114

90.6

7.52

0.000

16.6

0.12

1.08

3.54

1.21

13.0

4.05

46.0

17.0

77.1

17.8

183

36.3

417

0.55

227

15.4

753

CK135-9

134

103

8.07

0.017

22.2

0.10

1.21

3.26

1.47

16.6

5.48

62.1

21.9

95.3

21.4

214

42.5

507

0.61

298

18.4

759

CK135-10

259

163

10.18

0.041

35.7

0.15

2.29

5.14

2.51

29.2

8.59

90.9

30.0

123

26.9

261

49.8

665

0.63

204

15.6

782

CK135-11

125

85.4

4.94

0.008

17.2

0.03

0.94

2.41

0.96

10.6

2.98

32.7

10.8

44.5

10.1

100

19.7

253

0.58

222

18.2

714

CK135-12

41.5

47.6

6.33

0.000

8.12

0.03

0.76

1.27

0.85

7.64

2.19

24.6

10.0

45.6

11.4

130

27.2

270

0.84

242

10.6

736

CK135-13

409

213

12.10

0.048

49.8

0.10

2.66

5.78

2.89

35.9

11.1

119

37.8

148

31.2

297

55.4

796

0.61

240

18.7

800

CK135-14

382

194

6.11

0.032

51.9

0.16

2.64

6.91

3.11

41.8

12.1

127

42.7

173

37.1

346

64.2

908

0.56

246

19.7

733

CK135-15

322

205

6.64

0.122

46.6

0.14

2.81

6.21

3.03

39.4

10.9

116

37.0

150

32.3

303

56.1

803

0.59

203

16.6

741

Graphical abstract

Highlights 1.

The Jurassic porphyries at Chuankeng were formed at intra-plate extensional setting.

2.

Magma source are Neoproterozoic juvenile crust with minor Paleoproterozoic ancient crust.

3.

More contributions of ancient crust, lower oxygen fugacity and water contents reduce Cu fertility.

4.

Nd-Hf isotopes, zircon Ce4+/Ce3+and Tti-zr can be used together to assess the potential of Cu mineralization.

Author Contributions: conceptualization, XinZhang, Pei Ni and Guo-Guang Wang; methodology, Xin Zhang ; software, Xin Zhang, Su-Ning Li.; validation, Xin Zhang, Pei Ni, Guo-Guang Wang, Yao-Hui Jiang, Ding-Sheng Jiang; formal analysis, Xin Zhang, Pei Ni, Guo-Guang Wang, Yao-Hui Jiang, Ding-Sheng Jiang; investigation, Xin Zhang, Su-Ning Li, MingSen Fan; data curation, Xin Zhang, Yao-Hui Jiang, Ding-Sheng Jiang, Su-Ning Li, Ming-Sen Fan.; writing-original draft preparation, Xin Zhang, Pei Ni, Guo-Guang Wang, Yao-Hui Jiang, Ding-Sheng Jiang; writing-review and editing, Xin Zhang, Pei Ni, Guo-Guang Wang, Su-Ning Li, Ming-Sen Fan; visualization, Xin Zhang, Pei Ni, Guo-Guang Wang, Ming-Sen Fan; project administration, Xin Zhang, Pei Ni, GuoGuang Wang; funding acquisition, Xin Zhang, Pei Ni, Guo-Guang Wang

Conflict of interest statement

We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled “Petrogenesis and oxidation state of the ore-related granodiorite porphyry in the Jurassic Chuankeng skarn deposit, South China: implications for the assessment of copper mineralization fertility”.