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Article

Formation of the Granodiorite-Hosting Magushan Cu–Mo Polymetallic Deposit in Southern Anhui, Eastern China: Evidences from Geochronology and Geochemistry

by
Huasheng Qi
1,2,3,
Sanming Lu
3,*,
Xiaoyong Yang
1,2,*,
Yuzhang Zhou
3,
Lili Zhao
3,
Jianghong Deng
1,4 and
Jianshe Li
3
1
CAS Key laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei 230026, China
2
CAS Center for Excellence in Comparative Planetology, University of Science and Technology of China, Hefei 230026, China
3
Public Geological Survey Management Center of Anhui Province, Hefei 230091, China
4
CAS Key Lab of Marine Geology and Environment, Center of Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
*
Authors to whom correspondence should be addressed.
Minerals 2019, 9(8), 475; https://doi.org/10.3390/min9080475
Submission received: 4 July 2019 / Revised: 25 July 2019 / Accepted: 31 July 2019 / Published: 2 August 2019
(This article belongs to the Special Issue Role of Magmatic Activity in Generation of Ore Deposits)
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Abstract

:
The newly discovered Magushan Cu-Mo polymetallic deposit, located in southeastern Anhui, eastern China, is a middle-scale skarn-type polymetallic deposit with different ore types of veinlets-disseminated skarn (the primary type), quartz veins, and porphyry. LA-ICP-MS zircon U–Pb analyses yielded a crystallization age of 135.7 ± 1.5 Ma for the ore-related granodiorite in Magushan. The granodiorites are I-type granites in nature, characterized by metaluminous and high-K calc-alkaline characteristics. They are enriched in large ion lithophile elements (LILEs, e.g., Ba, Th, and U) and light rare earth elements (LREEs), and depleted in high field strength elements (NFSEs, e.g., Nb, Ta, and Ti) and heavy rare earth element (HREEs), with slightly negative Eu anomalies (Eu/Eu* = 0.81–0.86). These granodiorites show high Mg# (mainly > 40) values, high MgO (1.73–1.96 wt. %) and low Na2O (<4.21 wt. %) contents, with whole-rock (87Sr/86Sr)i ratios (0.708877 to 0.710398), negative εNd(t) values of −5.4 to −5.2, and negative zircon εHf(t) values of −4.60 to −1.37, with old two-stage Hf model ages (TDM2) between 1.2‒1.5 Ga. Besides, they are characterized by high radiogenic Pb isotopic compositions with (206Pb/204Pb)i = 18.44–18.56, (207Pb/204Pb)i = 15.66–15.67, and (208Pb/204Pb)i = 38.77–38.87. These granodiorites are characterized by high zircon Ce4+/Ce3+ ratios (average 893) and Eu/Eu* ratios (average 0.51), indicating high magmatic oxygen fugacities. The distinct geochemical and isotopic features suggest that the Magushan granodiorites could be formed by metasomatized mantle-derived magmas, mixing with materials from Neoproterozoic crust that is widely distributed in the Southern Anhui. This study concludes that the formation of the Magushan Cu-Mo polymetallic deposits may largely depend on an oxidizing environment and multi-sources mixed of mantle- and crust-derived materials.

1. Introduction

The Lower Yangtze region (LYR), located on the eastern segment of Yangtze block, can be separated into two important metallogenic belts: Jiangnan Tungsten belt (JNB) in the south and the Middle-Lower Yangtze River Metallogenic belts (MLYRB) in the north, which are bounded by the Yangxing-Changzhou Fault (YCF) (Figure 1). MLYRB is distinguished by the widespread porphyry- and skarn-type Cu–Au–Fe–Mo deposits, related to the Mesozoic I-type or adakitic granitoids [1,2,3,4,5], whereas the JNB is famous for the tungsten polymetallic mineralization, with occurrence of many giant to large-scale tungsten polymetallic ore deposits, e.g., Zhuxi [6], Dahutang [7], Yangchuling [8], Dongyuan [9], and Xiaoyao [10]. Recently, a variety of large- and medium-sized Cu–Mo polymetallic deposits have been discovered and explored within the Jiangnan Fault region (JNF) between the MLRYB and the JNB, such as Matou Cu–Mo deposit [11], Jitoushan Cu–Mo–W deposit [12], Anzishan Cu–Mo deposit [13], Pailou Mo–Au deposit [13], and Magushan Cu–Mo deposit, showing great ore-prospecting potentials in the region. However, the Cu–Mo polymetallic mineralization and related granitic magmatism have been not well constrained. As reported by previous studies, the large-scale magmatism in this region mainly occurred in the Yanshanian and could be sub-divided into two groups, i.e., 155–135 Ma and 134–120 Ma. The early group is mainly composed of peraluminous to metaluminous and high-K calc-alkaline series (I-type) granodiorite and monzonitic granitoids [9,11,14,15,16], whereas the second group consists of monzonitic granites and syenites with peraluminous calc-alkaline geochemical signatures, which is regarded to be A- and S-type granite [17,18,19,20,21]. Besides, the ore-forming ages of Cu–Mo polymetallic deposits mainly range from 150 to 135 Ma in this region, indicating that these deposits have genetic links with the early stage granitic rocks [13,21,22]. However, the magma origin of these granitic rocks and tectonic evolution of the Jiangnan Fault region (JNF) have been argued in the past decade [11,13,16,21,23]; therefore, the genesis of these granitic rocks and related Cu–Mo deposits remain unclear.
The Magushan skarn Cu–Mo deposit (Figure 1), located in the Jiangnan Fault region (JNF) between the JNB and the MLYRB, is a newly exploited skarn-type polymetallic deposit with 73 Kt of Cu (grade range of 0.6–1.2%) and 8 Kt of Mo (grade range of 0.06–1.2%). It provides an ideal area to study the granitic magmatism and related Cu–Mo metallogenesis in the Jiangnan Fault region (JNF). However, since this deposit is newly founded and explored, few studies have been carried out, and the age and petrogenesis have not been well constrained. Therefore, we have taken detailed geochronological and geochemical studies of the Magushan granodiorites, including precise zircon U–Pb dating, in-situ zircon Lu–Hf isotope, and whole-rock geochemical and Sr–Nd–Pb isotopic analyses, in association with previous studies on other skarn-porphyry type Cu–Mo polymetallic deposits in the JNF region (Table 1), to reveal the petrogenesis and tectonic significance of the granodiorite and its relationship with large-scale Cu–Mo mineralization in the Magushan area.

2. Geological Setting

2.1. Regional Geology

The Jiangnan Fault region (JNF) between the Middle-Lower Yangtze River Metallogenic belts (MLYRB) and Jiangnan Tungsten belt (JNB) is on the southeastern segment of the Yangtze Block, north of YCF. The JNF region and its adjacent area are mainly underlain by the Neoproterozoic basement (Shangxi and Likou Groups, composed of volcanic rocks and epimetamorphic rocks in southern Anhui province) [26,27]. It has endured Jinningian, Caledonian, Hercynian, Indosinian, and Yanshanian multiple stages of tectonic movements and tectonic evolution. Indosinian and Yanshanian movements controlled the tectonic framework in this region [21]. The main units consist of Silurian to Early Triassic marine sedimentary strata and carbonate rocks, Middle Triassic to Early Jurassic marine and terrestrial sedimentary rocks, and Early Cretaceous evaporites, volcanic rocks, and red beds [28]. Indosinian-Yanshanian tectonic movements in this region produced a series of NE-trending complex folds (syncline and anticline), faults (e.g., Gaotan Fault, Jiangnan Fault, Ningguo-Jixi Fault, Zhouwang Fault, and Qimeng-Qiankou Fault). These structures have significant impacts on the emplacement of Mesozoic granites and the related ore deposits [8,10,12,21]. During the Yanshanian stage, this area became active again with extensive magmatism in the intraplate setting [1].
Magmatic activity in this region is dominated by the Jinningian and Yanshanian granitic magmatism. The Jinningian granitic intrusions can be sub-divided into two groups. The early group (850–832 Ma) mainly consists of granodiorite, which are mostly S-type granites, such as the Xucun (850 Ma), Xiuning (832 Ma), and Shexian (838 Ma) plutons [14,19,26]. The latter group, with ages of 823–785 Ma, mainly occurs as granite porphyry and moyite, belonging to high-K calc-alkaline series A-type granites, such as Lingshan (823 Ma), Lianhuashan (814 Ma), and Shiershan (785 Ma) granites [14,19,29]. Practically, the Yanshanian igneous rocks are widely distributed in the Jiangnan Fault region (JNF), which manifested as complex plutons, clearly controlled by fault zones [14]. Numerous polymetallic deposits are associated with intermediate-felsic magmas and hydrothermal activity in the JNF region [23]. Ore deposits in the region include porphyry, skarn, and hydrothermal vein types.

2.2. Geology of Deposit

The Magushan Cu–Mo deposit is a middle-scale skarn-type polymetallic deposit located in the southeastern Anhui province (Figure 2a). The stratum sequences outcropped in this area mainly comprise the middle-upper Carboniferous Huanglong, Chuanshan Formations, and Permian Qixia Formation (Figure 2b). Affected by multi-period tectonic movements, large numbers of secondary folds and NE-trending faults were developed in the Magushan anticline, accompanied by many secondary faults including decollement structures. The most important structures are the decollements in Magushan overturned anticline, which control the location and shape of ore-bodies (Figure 2c). Two copper and molybdenum ore bodies, occurring in the contact zones between the granodiorites and Carboniferous limestones, were exploited in the Magushan deposit, with 0.6–1.2 wt. % of Cu and 0.06–1.2 wt. % of Mo. The alteration of the Magushan deposit consists of silicification, serpentinization, skarnization, K-feldspathization, and marmarization. Chalcopyrite, molybdenite, pyrite, and bornite are main ore minerals (Figure 3a,d,g,h), and garnet, calcite, diopside, quartz, wollastonite, serpentine, and talc are mainly gangue minerals. The Cu–Mo ores also show hypidiomorphic crystal, metasomatic, and corrosion textures (Figure 3g,h), and massive and disseminated structures (Figure 3d).
The granodiorite in the Magushan deposit intrudes into decollement structures of strata and is buried at the core of the Magushan overturned anticline (Figure 3b,c). The granodiorites are composed of plagioclase (40–45%), K-feldspar (15–22%), quartz (18–22%), biotite and hornblende (8–15%) with fine-grained typical granitic texture and massive structure (Figure 3e,f). The accessory minerals are mainly titanite, rutile, and apatite.

3. Methods

3.1. Whole-Rock Major and Trace Elements

Whole-rock major and trace elements of fresh samples were analyzed at the Ministry of Land and Resources P.R.C. Hefei Mineral Resources Supervision and Testing Center. They were ground to >200 mesh using an agate mortar. Major elements were determined by XRF spectrometry, and trace and REE elements solutions were determined by an Elan DRC-II (Element, Finnigan MAT) inductively coupled plasma mass spectrometry (ICP-MS). Details of the analytical method used are described by [30]. The analytical precision of major, trace, and REE elements was generally better than 5% (2σ).

3.2. Zircon U-Pb Isotopes Analyses

Zircon grains were separated from fresh granodiorites, handpicking using a binocular microscope, and then mounted in epoxy resin and polished under buffing machine. The reflected light images of the zircon grains were photographed, and cathodoluminescence (CL) images of the zircons were taken under microanalyses to select the U–Pb dating points at CAS Key Laboratory of Crust-Mantle Materials and Environments in University of Science and Technology of China (USTC). Zircon U–Pb dating and synchronously trace element analyses of zircons using by LA-ICP-MS were conducted at the School of Resources and Environmental Engineering, Hefei University of Technology, China. The laser-ablation system was a GeoLas Pro, applied at an energy of 78 mJ, with a spot beam diameter of 32 μm on the frequency of 7 Hz. Helium was used as carrier gas sampling ablation aerosols to the ICP for Analysis. External calibration were SRM 610 glass and Temora zircons standards and 29Si used as the internal standard. Off-line selection and analyses of trace element and U–Pb dating were performed by ICPMSDataCal 9.6 [31]. Concordia diagrams and weighted mean age calculations were analyzed by Isoplot/Ex_ver3 [32]. All errors are quoted as 2σ.

3.3. Zircon Lu–Hf Isotopes

In-situ Lu–Hf isotopes were measured at the State Key Laboratory of Continental Dynamics in Northwest University, using a Nu Plasma II MC-ICP-MS. The detailed instrumental parameters were described by [33]. The laser-ablated spot beam diameter of was 44 μm, while the constant energy applied was 6 J/cm2, and the laser repetition rate was 6 Hz. All error of the Lu–Hf isotope results are reported in 2σ. Details of the calculation method and parameter used for εHf(t) and old model ages were described by [34,35,36].

3.4. Sr–Nd–Pb Isotopes

All Sr–Nd–Pb isotopes were measured at the CAS Key Laboratory of Crust-Mantle Materials and Environments in USTC. Sr–Nd–Pb isotope ratios were measured by a Finnigan MAT-262 spectrometer. The precision for Sr–Nd and Pb are better than 0.003% and 0.01%, respectively. More details on analytical methods and procedures were given in [37].

4. Results

4.1. Whole-Rock Geochemistry

The major- and trace-element results are listed in Table S1 and plotted in Figure 4 and Figure 5. In addition, we selected granodiorites associated with other Cu–Mo deposit for comparison in the Jiangnan Fault region (JNF).
The Magushan samples (SiO2, 62.75–66.36 wt. %) are granodiorites, based on petrography and geochemistry (Figure 3c,e,f and Figure 4a). The alkali contents of 7.06–8.09% show characteristics of the sub-alkaline series and DI (differentiation index) values of 69–79 indicate that they are not highly fractionated. They are metaluminous with low A/CNK ratios of 0.87–0.97 (Figure 4c), and mostly plotted in the field of the high-K calc-alkaline series on the SiO2 versus K2O diagram (Figure 4b). They are characterized by relatively high Al2O3 (14.52–16.13 wt. %), MgO (1.73–1.96 wt. %) concentrations and Mg# (average 45), moderate Sr concentrations (290–602 ppm), and low Nb, Zr concentrations (9.60–11.32, 148–195 ppm, respectively) and Sr/Y ratios (12.9–27.9). REE distribution patterns of samples show enrichment of LREE, depletion of HREE, evident fractionation between LREE and HREE ((La/Yb)N = 8.31–10.47), and slightly negative anomalies of Eu (Eu/Eu* = 0.81–0.86, Figure 5a). On the PM-normalized trace elements diagram (Figure 5b), they also display enriched large ion lithophile elements (LILEs, e.g., Ba, Th, and U) and depleted high field strength elements (HFSEs), with positive Sr anomalies and negative Nb, Ta, and Ti anomalies.

4.2. Zircon U–Pb Geochronology and Trace Elements

The U–Pb isotopic data of zircon grains from a granodiorite sample (MGS01) are listed in Table S2. Cathodoluminescence (CL) images show typical oscillatory zonings (Figure 6a). In addition, the analyzed zircons are transparent, colorless, euhedral, with a length of 100–200 μm and length/width ratios of 2:1 to 4:1. The zircon Th/U ratios of 0.46–0.81 (Table S2) again support a magmatic origin [42,43]. The measured 206Pb/238U ratios yield a weighted mean age of 135.7 ± 1.5 Ma (MSWD = 0.62, n = 22), which represents the crystallization ages of the Magushan granodiorite (Figure 6b).
Most of the zircons from the Magushan granodiorites also have the same REE distribution patterns with depleted LREE and enriched HREE, obviously positive anomalies of Ce and weak negative Eu anomalies. The calculated zircon Eu/Eu* (0.42–0.66, average 0.51) and Ce4+/Ce3+ ratios (548–1409, average 893) [44], and TTi-in-zircon values (667–735 °C) [45] of the Magushan granodiorites are listed in Table S3 and shown in Figure 13b,c.

4.3. Zircon Lu–Hf Isotopes

The analyzed zircon Lu–Hf isotopic compositions of the granodiorite are listed in Table S4. Zircon 176Hf/177Hf ratios are relatively homogeneous, with values between 0.000784 and 0.001398, (mean = 0.001088). The calculated εHf(t) values are negative and range from −4.60 to −1.37 (mean = −2.88, Figure 7). The Hf-depleted mantle model ages are between 859 and 985 Ma, and the two-stage model ages range from 1280 to 1468 Ma.

4.4. Sr–Nd–Pb Isotopes

The Sr–Nd–Pb isotopic results of the Magushan granodiorites are shown in Table S5. The Sr–Nd isotopes of these rocks show high (87Sr/86Sr)i values (0.708877 to 0.710398) and low εNd(t) values (−5.2 to −5.4, Figure 8), which are similar to the values of granodiorites associated with Cu–Mo deposit in the JNF region. Moreover, they have high radiogenic Pb isotopic compositions with (206Pb/204Pb)i = 18.44–18.56, (207Pb/204Pb)i = 15.66–15.67 and (208Pb/204Pb)i = 38.77–38.87, which are plotted in the field of MORB and near the EM-2 end-member (Figure 9, [49]). These compositions are obviously different from those of lower continental crust (LCC), upper continental crust (UCC), high-μ mantle (HIMU) [49], and lower continental crust-derived Dabie adakites [50].

5. Discussion

5.1. Ages of the Magushan Granodiorites

In the last few years, systematic geochronological studies have revealed the relationship between Late Jurassic-Early Cretaceous magma activity and mineralization in the MLYRB and the JNB [4,5,17,21]. Three stages of magmatism were identified in the MLYRB: (1) first stage (148–135 Ma), adakitic rocks related to Cu–Au polymetallic deposits, (2) second stage (134–129 Ma), sub-alkaline to alkaline mafic to intermediate volcanic/sub-volcanic rocks associated with magnetite-apatite deposits, and (3) third stage (128–124 Ma), A-type granitoid associated with a few uranium and gold mineralizations [4,5,52,61]. In contrast, the JNB can be divided into two sub-stages: (1) mainly calc-alkaline I-type granitoids related to W–Mo–Cu mineralization (155–135 Ma) and (2) mainly ore-barren A-type granite (porphyry) and syengranite (134–124 Ma) [17,20,21,22,62,63]. Recently, several rock- and ore-forming ages for the granitic rocks and related Cu–Mo mineralization in the Jiangnan Fault region (JNF) were reported, for instance, the Matou Cu–Mo deposit with rock-forming age of ca.149 Ma and ore-forming age of ca.150 Ma [13], the Jitoushan Cu–Mo–W skarn deposit with ca.138 Ma rock-forming age and 136.6 ± 1.5 Ma ore-forming age [12], and the Tongshan Cu deposit with rock-forming age of 147.5 ± 2.3 Ma and ore-forming age of 150 ± 1.5 Ma [64]. These ages further indicated that Cu–Mo polymetallic mineralizations in the JNF are closely related to the first stage magmatic activity. In this study, we reported that the zircon U–Pb age of the Magushan granodiorite is 135.7 ± 1.5 Ma, which is consistent with the ages of regional magmatism. It indicates that Cu–Mo mineralization in Magushan is likely genetically linked to the Magushan granodiorite.

5.2. Petrogenesis of the Magushan Granodiorites

5.2.1. Genetic Type: An I-type Affinity

Previous studies have concluded that granitic rocks can be classified into I-, M-, S-, and A-types on the basis of their respective geochemical signatures [65,66,67]. Identifying the genetic type of igneous rocks is meaningful for origin and process of magma, and tectonic setting [68]. Notably, the Magushan granodiorites show some parallel geochemical features with other Mesozoic adakite-like rocks occurred in the MLYRB (e.g., Anqing, Edong-Jiurui and Tongling region). However, the Magushan granodiorites also display clearly distinct geochemical characteristics (low Nb and Sr contents and Sr/Y ratios, high ISr, low εNd(t) and εHf(t) values of zircon) compared to these adakite-like rocks, suggesting different petrogenesis for the magmas. The Magushan granodiorites have comparatively low Sr/Y ratios and (La/Yb)N values (12.97–27.93, and 8.31–10.47, respectively), showing that these samples belong to typical arc rocks (Figure 10f). They also have high contents of CaO and Na2O (Table S1), and relatively low A/CNK ratios (Figure 4c), showing the feature of I-type granite. Meanwhile, the Magushan granodiorites are plotted in the field of unfractionated M-, S-, I-type granites in the (Na2O + K2O)/CaO vs. (Zr + Nb + Ce + Y) diagram (Figure 10a). It is notable that the granodiorites have low P2O5 content and negative correlation between the P2O5 and SiO2 (Figure 10b), consistent with the I-type granite in the Lachalan Fold Belt, Australia [67,69]. In addition, the low concentrations of Zr (149–195 ppm) and moderate Sr concentrations (291–602 ppm) of these samples imply that they most likely belong to the I-type granite, rather than adakite or A-type granites (Figure 10c,e). Moreover, the granodiorites have low Th contents, and show a clear positive correlation with the Rb contents (Figure 10d), which is a common feature of the typical I-type granite [70]. Thus, we propose that the Magushan granodiorite can be classified as high-K calc-alkaline I-type granitoids.

5.2.2. Petrogenesis

It is well accepted that I-type granitoids in the JNF region are closely related to the Cu-, Mo-bearing skarn-porphyry mineralization, whereas the genesis and origin of these granitoids are still controversial topics [12,16,21,72]. Several models have been presented to interpret the formation of these granites: (1) partial melting of oceanic crust [8] or the thickening lower crust [52,72]; (2) fractional crystallization (FC) of basaltic magma with crustal contamination [12,21,73]; and (3) melting of continental crust with involvement of mantle components [10,11,23] or formed by metasomatized mantle-derived magma with addition of Neoproterozoic continental crustal materials [13].
Firstly, evidences for the models of partial melting of the thickening lower crust and/or oceanic crust is inadequate for the Magushan granodiorites. They also have higher (87Sr/86Sr)i ratios (0.708877 to 0.710398), lower εNd(t) (−5.4 to −5.2) and zircon εHf(t) (−4.60 to −1.37) than those of thickened lower crust (Dabie adakites) or slab-derived adakites (Figure 7 and Figure 8), implying that the Magushan granodiorites could not be derived from those origins (Figure 8 and Figure 9). Besides, the melts of lower continental crust display low Mg# and copper concentrations [74,75], inconsistent with the Magushan granodiorites with evident Cu–Mo mineralization, high MgO contents of 1.73–1.96 wt. % and high Mg# values of 42–51 over than 40. In addition, the Magushan granodiorites have obviously lower Ce/Pb ratios (average 4) than those of oceanic crust (~24) [41] and significantly negative anomalies of Nb–Ta (Figure 5b). Thus, these characteristics suggest that the Magushan granodiorites are unlikely produced by partial melting of the thickened lower crust and oceanic crust.
On the basis of our geochronological data of the Magushan granodiorite samples, the model of fractional crystallization (FC) of basaltic magma model is also not the best explanation in this case. In Harker diagrams (Figure 11), there is no clearly correlation relationship between SiO2 and other oxides, combining with the positive correlation between Ta/Sm values ratios and Ta contents, which is consistent with trend of partial melting, indicating that the partial melting (PM) might be the primary mechanism in controlling the component transformation of the Magushan granodiorites rather than the fractional crystallization (Figure 12b). In addition, simple log-log diagrams of compatible elements and incompatible elements recognize trends of fractional crystallization (FC) or partial melting (PM) [76]. On the Rb versus V diagram (Figure 12a), indicating PM played a leading role in the chemical variations than FC path. Therefore, the Magushan granodiorites should unlikely be produced by fractional crystallization process.
Therefore, we are inclined to believe that parting melting of the mantle-derived magmas mixing with continental crust components is the most suitable explanation for the genesis of the Magushan granodiorites, as well as other granitoids that are associated with Cu–Mo mineralization in the JNF region. The relatively high (La/Yb)N and Eu/Eu* ratios of the Magushan granodiorites reveal that they belong to the crust-mantle type granitoids (Figure 12f). In addition, the positive correlation between the 87Sr/86Sr values and SiO2 (Figure 12c), and Ce/Yb and Ce (Figure 12d) also indicate a magma mixing origin.
The Hf isotopic analyses of the Magushan samples suggest that all of the zircon grains have low Hf isotopic values and ancient Hf model ages, with εHf(t) values of  −4.60 to −1.37 (average −2.88) and the two-stage Hf model ages of 1280–1468 Ma. They correspond to the evolution array of the Neoproterozoic intrusive rocks as a response to Neoproterozoic crustal growth within the Lower Yangtze Craton (Figure 7), suggesting that the magmatic source of the Magushan granodiorites has a large proportion of Neoproterozoic crustal materials [77].
The geological characteristics of the Magushan granodiorites indicate the mantle-derived component was also involved in the parent magma. The Magushan granodiorites have relatively higher MgO (1.73–1.96 wt. %) and Mg# (42.8–51.4) than those granites formed from Neoproterozoic crust with additional mantle in Jiangnan W–Mo belt (Figure 12e), implying the involvement of mantle materials. Importantly, the higher εNd(t) and lower 87Sr/86Sr than the Sr–Nd isotopic compositions of the Neoproterozoic basement (Shangxi Group) can be observed (Figure 8). In addition, those isotopic compositions are clearly different from the Neoproterozoic basement (Shangxi Group) and the metasomatized enriched mantle in MLYRB, proposing that the granodiorites were unlikely formed from partial melting of lower crustal material directly as well as those granites in the JNF region. Alternatively, the mantle material should be involved in the source of the granodiorites. Besides, the Magushan granodiorites show comparatively high radiogenic Pb isotopic compositions, plotted in the field of MORB and near the EM-2 end-member. These isotopic features suggest that the metasomatized enriched mantle could also largely contribute into the magmatic source of the Magushan granodiorites, similar to the conditions of MLYRB adakitic rocks [52,78,79,80]. Therefore, the magmatic source of Magushan granodiorites may be a mixture of two end-members, i.g., the Neoproterozoic basement (Shangxi epimetamorphic rocks and Neoproterozoic igneous rocks with εNd(t) values of −8.75 [53]) and the metasomatized enriched mantle (identified as NNS formation volcanic rocks from [52]). Meanwhile, most of the granodiorite samples are plotted on the mixing curve line of the enriched mantle (EM) and Neoproterozoic basement (Figure 8). They show similarities with Cu–Mo related granodiorites in the JNF region are slightly different from those granites in the Jiangnan W–Mo belt, which were proposed to be mostly derived from Neoproterozoic crustal basement with a small amount of mantle material added [6,8,10,81]. Binary mixing model calculation results show that about 55% enriched mantle and 45% additional Neoproterozoic basement materials are involved in the magma source of Magushan granodiorites (Figure 8). All of these observations propose that the Magushan high-K calc-alkaline I-types granodiorites associated with the Cu–Mo mineralization were originated from the partial melting of metasomatized enriched mantle-derived magmas mixing with Neoproterozoic crustal components.

5.2.3. Physical-Chemical Conditions of Magma

Temperature and oxygen fugacity are important indexes for the magma because it can have a huge influence on nature, melting processes, and behavior of the multivalent elements of magma [82,83]. Zircon forming temperature is the main factor that influence the Ti content of zircon, and the thermometer of Ti-in-zircon has been generally applied to verify evolution or metamorphism of the magma [84]. Based on the model proposed by [84], the calculated Ti-in-zircon temperatures of the Magushan granodiorites range from 667–735 °C (average 704 °C), suggesting the crystallization temperature of the Magushan granodiorites.
As zircon is stable, refractory and impervious to late-stage hydrothermal activity, the calculated zircon Ce4+/Ce3+ and log fO2 values are good pointers of the magmatic oxygen fugacity [85,86,87], The calculated log fO2 values of magmatic zircons (Figure 13a) follow the method of [85] range from −17.42 to −19.14, mainly falling within the filed between magnetite-hematite (MH) and fayalite-magnetite-quartz (FMQ) buffers (Figure 13b), suggesting high oxygen fugacities of these magma. Meanwhile, the calculated zircon Ce4+/Ce3+ values (548–1409, average 893) and Eu/Eu* ratios (0.42–0.66, average 0.51) of the Magushan granodiorites (Figure 13c) also indicate that these intrusions were formed under a high-fO2 environment.

5.3. Tectonic Setting of Magmatism and Cu–Mo Mineralization

It was well accepted that eastern China was an active continental margin in the Late Mesozoic and was closely related to the subduction of the Paleo-Pacific oceanic plate, leading to the widespread of Late Mesozoic igneous rocks [88,89,90,91,92,93]. Three stages of the Late Mesozoic magmatism were identified [94]: (1) initial arc rifting type magmatism occurring in intraplate setting at the Early Yanshanian; (2) continental margin igneous tectonic setting at the early Late Yanshanian; and (3) volcanism occurring in extensional setting at the Late Yanshanian stage. In the tectonic discrimination diagrams (Figure 14), the Magushan magmatic rocks in the JNF were mostly plotted in the field of volcanic arc granite (VAG). Combined with the formation age of the Magushan granodiorites, it is suggested that these granodiorites were formed at an active continental margin, linked to subduction of the Paleo-Pacific oceanic plate [11,13,16,23]. Furthermore, the Magushan granodiorite have high Y/Nb ratios (generally >2), enriched light REEs, and LILEs, and depleted HFSEs and heavy REEs (Figure 5), showing the typical feature of subduction-related magmas [75,95].
The Cu–Mo polymetallic mineralization is genetically linked to the I-type granodiorites in the JNF both in time and space [11,12,13,16,23]. It is widely accepted that large-scale Cu–Mo polymetallic mineralization is closely related to high oxygen fugacity magmas in usual [44,78,82,83,96,97,98,99]. Generally, highly oxidized magmas can control the behavior and speciation of sulfide, and the behavior of copper is controlled by sulfur [99]. During partial melting, sulfur could be extracted in the form of sulfate under high oxidizing environment, liberating more chalcophile elements (e.g., Cu, Au) and keeping the melt sulfide under-saturated, therefore elevating further Cu–Mo multi-metallic mineralization [100,101]. Importantly, the metasomatized enriched mantle has not only higher Cu and S contents but also have high fO2 relative to DMM, thus producing more Cu–S bearing magmas during melting processes [13,78,80,89]. The Magushan granodiorites have higher oxygen fugacities than granites from Jiangnan W–Mo belt that were proposed to be derived from Neoproterozoic crustal basement with a small quantity of additional mantle materials (Figure 13c), indicating more mantle components were added in the source. Therefore, the Magushan granodiorites may be more closely related to large Cu-, Mo- polymetallic mineralization than other granites in the Jiangnan Fault region (JNF).
Based on the evidence provided in this study, a simplified geodynamic model involving slab subduction is proposed for the formation of the Magushan deposit (Figure 15). Before ca.148 Ma, the Paleo-Pacific oceanic plate subducted beneath the continental lithosphere of the Yangtze Block at low angles [52,88,89,90]. Eclogization of the oceanic slab resulted in intense dehydration of the subducted sediments and oceanic plate under comparatively high P-T conditions. Simultaneously, the overlying mantle wedge was metasomatized by those released fluids, forming an enriched mantle. Due to the change of subduction angle after 148 Ma, the Jiangnan Fault region (JNF) from continental arc margin to an extensional setting led to the upwelling of asthenosphere and partial melting of the metasomatic lithosphere mantle. Sequentially, the magma intruded into the accreted Neoproterozoic crustal units, and further induced partial melting of the Neoproterozoic crust, ultimately forming a mixed magma with high oxygen fugacity. Then, the mixed magma with abundant copper and molybdenum metals ascent to the shallow crust to from the granodiorites, by reacting with surrounding carbonate rocks to finally from the Cu-Mo polymetallic deposits in the Jiangnan Fault region (JNF), including the Magushan deposit.

6. Conclusions

Based on geological, geochemical, and geochronological studies of the granodiorites from the Magushan Cu–Mo polymetallic deposit, we draw the following conclusions:
(1) The Magushan granodiorite with affinities of metaluminous to slightly peraluminous, high-K calc-alkaline I-type granite was formed at ca. 135.7 Ma of Early Cretaceous, they were proposed to be formed by metasomatized mantle-derived magma mixing with Neoproterozoic crustal components.
(2) The formation of the Cu–Mo polymetallic deposits in the Magushan area may be closely related to a mantle-crust mixed source that has high oxygen fugacities caused by Paleo-Pacific oceanic plate subduction.

Supplementary Materials

The following are available online at https://www.mdpi.com/2075-163X/9/8/475/s1, Table S1: Major (wt.%) and trace element (ppm) results of the Magushan granodiorites; Table S2: Zircon LA-ICP-MS U-Pb analytical data from the Magushan granodiorites; Table S3: Zircon trace elements and Ce4+/Ce3+ ratios and T-Ti in Zircon of the Magushan granodiorites; Table S4: MC-ICP-MS zircon Lu-Hf isotopic compositions of the Magushan granodiorites; Table S5: Whole-rock Sr–Nd–Pb isotopic compositions of the Magushan granodiorites.

Author Contributions

H.Q. wrote the paper; S.L., X.Y. and J.D. designed the experiments; Y.Z., L.Z. and J.L. took part in the field investigation.

Funding

This study is supported by the National Key Research and Development Program of China (2016YFC0600209), Project of Geological Science and Technology of Anhui Province (2016-K-4), and Natural Science Foundation of China (41673040).

Acknowledgments

The authors are grateful to three anonymous reviewers for their helpful comments and suggestions that greatly helped to improve an earlier manuscript version. We appreciate for C. Sun, H. Wang, H.S. Zhang, Y.G. Li, and M.Q. Jin assistance in zircon U–Pb dating and Lu–Hf isotope analyses. Finally, we greatly thank S.L. Qian, Z.J. Xie, Z.F. Yu from No.322 Unit of Bureau of Geology and Mineral Exploration of Anhui Province for field assistance.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Geologic map showing the distribution of porphyry-skarn Cu–Au–Mo–Fe deposits in the Middle-Lower Yangtze River metallogenic belt (MLYRB) in the north and the Jiangnan porphyry-skarn belt (JNB) in the south (modified after [8]). (1) Middle Jurassic to Cretaceous sedimentary and volcanic rocks; (2) Cambrian to Early Triassic strata marine clastic and carbonate rocks and Middle Triassic to Early Jurassic paralic clastic rocks; (3) Jiangnan Massif: Neoproterozoic epimetamorphic and sedimentary rocks; (4) Cretaceous granitoids; (5) Jurassic granitoids; (6) Neoproterozoic granite; (7) Neoproterozoic ophiolite; (8) River and lake; (9) W deposits; (10) Sn deposits; (11) Cu deposits; (12) Au deposits; (13) Cu–Mo deposits; (14) Study area.
Figure 1. Geologic map showing the distribution of porphyry-skarn Cu–Au–Mo–Fe deposits in the Middle-Lower Yangtze River metallogenic belt (MLYRB) in the north and the Jiangnan porphyry-skarn belt (JNB) in the south (modified after [8]). (1) Middle Jurassic to Cretaceous sedimentary and volcanic rocks; (2) Cambrian to Early Triassic strata marine clastic and carbonate rocks and Middle Triassic to Early Jurassic paralic clastic rocks; (3) Jiangnan Massif: Neoproterozoic epimetamorphic and sedimentary rocks; (4) Cretaceous granitoids; (5) Jurassic granitoids; (6) Neoproterozoic granite; (7) Neoproterozoic ophiolite; (8) River and lake; (9) W deposits; (10) Sn deposits; (11) Cu deposits; (12) Au deposits; (13) Cu–Mo deposits; (14) Study area.
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Figure 2. (a) Geological sketch map of the Magushan ore district; (b) Basement geological map of the Magushan Cu–Mo polymetallic deposit (modified after No.322 Unit of Bureau of Geology and Mineral Exploration of Anhui Province); (c) Section A–B of the Magushan Cu–Mo polymetallic deposit with sampling location. Abbreviation: JLSF—Jiulianshan thrust Fault; JNF—Jiangnan Fault.
Figure 2. (a) Geological sketch map of the Magushan ore district; (b) Basement geological map of the Magushan Cu–Mo polymetallic deposit (modified after No.322 Unit of Bureau of Geology and Mineral Exploration of Anhui Province); (c) Section A–B of the Magushan Cu–Mo polymetallic deposit with sampling location. Abbreviation: JLSF—Jiulianshan thrust Fault; JNF—Jiangnan Fault.
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Figure 3. Photographs and photomicrographs of the Magushan Cu–Mo polymetallic deposit. (a) molybdenite ores in the mine tunnel (−250 m); (b) stress-deformed granodiorites in the mine tunnel; (c) sample of the granodiorites; (d) copper molybdenum ores and molybdenites; (e) and (f) photomicrograph of the granodiorites; (g) rosette molybdenite assemblages; (h) fine vein molybdenite cutting chalcopyrite assemblage. Ccp—chalcopyrite; Mol—molybdenite; Qz—quartz; Bi—biotite; Hbl—hornblende; Kfs—K-feldspar; Pl—plagioclase.
Figure 3. Photographs and photomicrographs of the Magushan Cu–Mo polymetallic deposit. (a) molybdenite ores in the mine tunnel (−250 m); (b) stress-deformed granodiorites in the mine tunnel; (c) sample of the granodiorites; (d) copper molybdenum ores and molybdenites; (e) and (f) photomicrograph of the granodiorites; (g) rosette molybdenite assemblages; (h) fine vein molybdenite cutting chalcopyrite assemblage. Ccp—chalcopyrite; Mol—molybdenite; Qz—quartz; Bi—biotite; Hbl—hornblende; Kfs—K-feldspar; Pl—plagioclase.
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Figure 4. Classification diagrams of the lithochemical compositions for the Magushan granodiorites. (a) The Total alkalis vs. silica (TAS) diagram [38]. The alkaline and sub-alkaline division are after [39]. (b) K2O–SiO2 diagram for the Magushan granodiorites. The solid line is from [40]. (c) A/NK versus A/CNK diagram for the Magushan granodiorites. A/NK = Al/(Na + K), A/CNK = Al/(Ca + Na + K) (molar ratio). Literature data of granodiorites related with Cu–Mo deposit in the Jiangnan Fault region (JNF) are from [11] and [13], so are other major and trace elements or geochemical diagrams below.
Figure 4. Classification diagrams of the lithochemical compositions for the Magushan granodiorites. (a) The Total alkalis vs. silica (TAS) diagram [38]. The alkaline and sub-alkaline division are after [39]. (b) K2O–SiO2 diagram for the Magushan granodiorites. The solid line is from [40]. (c) A/NK versus A/CNK diagram for the Magushan granodiorites. A/NK = Al/(Na + K), A/CNK = Al/(Ca + Na + K) (molar ratio). Literature data of granodiorites related with Cu–Mo deposit in the Jiangnan Fault region (JNF) are from [11] and [13], so are other major and trace elements or geochemical diagrams below.
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Figure 5. (a) Chondrite-normalized REEs, and (b) primitive mantle-normalized trace element distribution patterns of the Magushan granodiorites. Chondrite-and primitive mantle-normalized data are taken from [41].
Figure 5. (a) Chondrite-normalized REEs, and (b) primitive mantle-normalized trace element distribution patterns of the Magushan granodiorites. Chondrite-and primitive mantle-normalized data are taken from [41].
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Figure 6. (a) Representative Cathodoluminescence (CL) images of zircon grains. (b) Zircon U–Pb Concordia diagrams and weighted average diagrams of the granodiorites in the Magushan deposit. U–Pb spots: red circles; Hf spots: blue circles.
Figure 6. (a) Representative Cathodoluminescence (CL) images of zircon grains. (b) Zircon U–Pb Concordia diagrams and weighted average diagrams of the granodiorites in the Magushan deposit. U–Pb spots: red circles; Hf spots: blue circles.
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Figure 7. Zircon Lu–Hf isotopic compositions of the Magushan granodiorite. Neoproterozoic granites are sourced from [26] and [27]. Data for the Kongling Group are from [46] and [47]. Data for the Douling complex are from [48].
Figure 7. Zircon Lu–Hf isotopic compositions of the Magushan granodiorite. Neoproterozoic granites are sourced from [26] and [27]. Data for the Kongling Group are from [46] and [47]. Data for the Douling complex are from [48].
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Figure 8. Initial Sr–Nd isotopic compositions of the Magushan granodiorites. Note: End-members used for binary mixing calculated lines are DMM with Sr = 21 ppm, Nd = 0.4 ppm, and 87Sr/86Sr(t) = 0.7022; εNd(t) = 10 [51]; The metamorphic enriched lithospheric mantle is defined by average values of the NNS formation volcanic rocks [52]. Neoproterozoic basement (Shangxi low-grade metamorphic rocks and Neoproterozoic magmatic rocks in the eastern Jiangnan Orogen) with Sr = 150 ppm, Nd = 27 ppm, 87Sr/86Sr(t) = 0.7175, and εNd(t) = -8.75 [53]; Archean Kongling Group with Sr = 315 ppm, Nd = 39 ppm, 87Sr/86Sr(t)) = 0.7177, and εNd(t) = −36.4 [54,55]. Data source: Dabie adakites [50,56], Tongling adakitic rocks [57,58], Granodiorites from the JNF region [11,13,23], Granodiorites from Jiangnan W–Mo belt [6,7,8,10], PM, EM-1, and EM-2 [49].
Figure 8. Initial Sr–Nd isotopic compositions of the Magushan granodiorites. Note: End-members used for binary mixing calculated lines are DMM with Sr = 21 ppm, Nd = 0.4 ppm, and 87Sr/86Sr(t) = 0.7022; εNd(t) = 10 [51]; The metamorphic enriched lithospheric mantle is defined by average values of the NNS formation volcanic rocks [52]. Neoproterozoic basement (Shangxi low-grade metamorphic rocks and Neoproterozoic magmatic rocks in the eastern Jiangnan Orogen) with Sr = 150 ppm, Nd = 27 ppm, 87Sr/86Sr(t) = 0.7175, and εNd(t) = -8.75 [53]; Archean Kongling Group with Sr = 315 ppm, Nd = 39 ppm, 87Sr/86Sr(t)) = 0.7177, and εNd(t) = −36.4 [54,55]. Data source: Dabie adakites [50,56], Tongling adakitic rocks [57,58], Granodiorites from the JNF region [11,13,23], Granodiorites from Jiangnan W–Mo belt [6,7,8,10], PM, EM-1, and EM-2 [49].
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Figure 9. Initial Pb isotope (a. (207Pb/204Pb)i/(206Pb/204Pb)i, b. (208Pb/204Pb)i/(206Pb/204Pb)i) ratios of the Magushan granodiorites. Data sources for MORB, Marine sediments, HIMU, EM-1, and EM-2 are from [49], Early Cretaceous mafic rocks in the LYRB are after [59,60], Dabie adakites [50,56].
Figure 9. Initial Pb isotope (a. (207Pb/204Pb)i/(206Pb/204Pb)i, b. (208Pb/204Pb)i/(206Pb/204Pb)i) ratios of the Magushan granodiorites. Data sources for MORB, Marine sediments, HIMU, EM-1, and EM-2 are from [49], Early Cretaceous mafic rocks in the LYRB are after [59,60], Dabie adakites [50,56].
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Figure 10. Plot of (a) (CaO + K2O)/CaO vs. Zr + Nb + Ce + Y (after [65]), (b) P2O5 vs. SiO2, (c) Zr vs. SiO2, (d) Rb vs. Th, (e) Sr vs. SiO2, and (f) Sr/Y vs. Y (after [71]) for the Magushan granodiorites. The A-type and I-type granite division is after [66]. The A-type, I-type and adakite division is after [63].
Figure 10. Plot of (a) (CaO + K2O)/CaO vs. Zr + Nb + Ce + Y (after [65]), (b) P2O5 vs. SiO2, (c) Zr vs. SiO2, (d) Rb vs. Th, (e) Sr vs. SiO2, and (f) Sr/Y vs. Y (after [71]) for the Magushan granodiorites. The A-type and I-type granite division is after [66]. The A-type, I-type and adakite division is after [63].
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Figure 11. Harker diagram of SiO2 versus the major elements in the Magushan granodiorites. Plot of a. SiO2 vs. Al2O3, b. SiO2 vs. CaO, c. SiO2 vs. Fe2O3T, d. SiO2 vs. Na2O, e. SiO2 vs. MgO, f. SiO2 vs. TiO2 for the Magushan granodiorites.
Figure 11. Harker diagram of SiO2 versus the major elements in the Magushan granodiorites. Plot of a. SiO2 vs. Al2O3, b. SiO2 vs. CaO, c. SiO2 vs. Fe2O3T, d. SiO2 vs. Na2O, e. SiO2 vs. MgO, f. SiO2 vs. TiO2 for the Magushan granodiorites.
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Figure 12. Plot of (a) V versus Rb and (b) Ta/Sm versus Ta (c) 87Sr/86Sr versus SiO2 (wt. %) (d) Ce/Yb versus Ce (e) Mg# versus SiO2 (wt. %) and (f) (La/Yb)N versus Eu/Eu* of the Magushan granodiorites. Note: PM—partial melting, FC—fractional crystallization. Data source: Granodiorites from the Jiangnan Fault region (JNF) [11,13,23], Granodiorites from Jiangnan W–Mo belt [6,7,8,10].
Figure 12. Plot of (a) V versus Rb and (b) Ta/Sm versus Ta (c) 87Sr/86Sr versus SiO2 (wt. %) (d) Ce/Yb versus Ce (e) Mg# versus SiO2 (wt. %) and (f) (La/Yb)N versus Eu/Eu* of the Magushan granodiorites. Note: PM—partial melting, FC—fractional crystallization. Data source: Granodiorites from the Jiangnan Fault region (JNF) [11,13,23], Granodiorites from Jiangnan W–Mo belt [6,7,8,10].
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Figure 13. Plot of (a) Zircon chondrite-normalized REE diagrams, (b) log fO2 vs. T (°C) and (c) Ce4+/Ce3+ value vs. Eu/Eu* value of zircon samples from the Magushan granodiorites. Zircon Ce4+/Ce3+ and Eu/Eu* values are calculated using the method of [85]. MH: magnetite–hematite buffer, FMQ: fayalite–magnetite–quartz buffer, IW: iron–wustite buffer. Data source: Granodiorites from the Jiangnan Fault region (JNF) [11,13], Granodiorites from Jiangnan W–Mo belt (unpublished data).
Figure 13. Plot of (a) Zircon chondrite-normalized REE diagrams, (b) log fO2 vs. T (°C) and (c) Ce4+/Ce3+ value vs. Eu/Eu* value of zircon samples from the Magushan granodiorites. Zircon Ce4+/Ce3+ and Eu/Eu* values are calculated using the method of [85]. MH: magnetite–hematite buffer, FMQ: fayalite–magnetite–quartz buffer, IW: iron–wustite buffer. Data source: Granodiorites from the Jiangnan Fault region (JNF) [11,13], Granodiorites from Jiangnan W–Mo belt (unpublished data).
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Figure 14. Tectonic discrimination diagrams for the granodiorites in Magushan and the JNF. (a) Ta versus Yb, (b) Rb versus (Yb + Ta), (c) Nb versus Y, and (d) Rb versus (Y + Nb) after [102]. VAG, volcanic arc granite (I-type); ORG, oceanic ridge granite; Syn-COLG, syn-collision granite (S-type); and WPG, intra-plate granite (A-type).
Figure 14. Tectonic discrimination diagrams for the granodiorites in Magushan and the JNF. (a) Ta versus Yb, (b) Rb versus (Yb + Ta), (c) Nb versus Y, and (d) Rb versus (Y + Nb) after [102]. VAG, volcanic arc granite (I-type); ORG, oceanic ridge granite; Syn-COLG, syn-collision granite (S-type); and WPG, intra-plate granite (A-type).
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Figure 15. Sketch geodynamic evolution model to explain the formation of the Cu-Mo polymetallic mineralization related granodiorites in the Jiangnan Fault region (JNF) including the Magushan deposit. a. Before ca.148 Ma, the Paleo-Pacific oceanic plate subducted beneath the continental lithosphere of the Yangtze Block at low angles, b. after 148 Ma, upwelling of asthenosphere and partial melting of the metasomatic lithosphere mantle due to the change of subduction angle. Sequentially, the magma intruded into the accreted Neoproterozoic crustal units, and further induced partial melting of the Neoproterozoic crust, ultimately forming a mixed magma. Then, the mixed magma ascent to the shallow crust to from the granodiorites and Cu-Mo polymetallic deposits in the Jiangnan Fault region (JNF).
Figure 15. Sketch geodynamic evolution model to explain the formation of the Cu-Mo polymetallic mineralization related granodiorites in the Jiangnan Fault region (JNF) including the Magushan deposit. a. Before ca.148 Ma, the Paleo-Pacific oceanic plate subducted beneath the continental lithosphere of the Yangtze Block at low angles, b. after 148 Ma, upwelling of asthenosphere and partial melting of the metasomatic lithosphere mantle due to the change of subduction angle. Sequentially, the magma intruded into the accreted Neoproterozoic crustal units, and further induced partial melting of the Neoproterozoic crust, ultimately forming a mixed magma. Then, the mixed magma ascent to the shallow crust to from the granodiorites and Cu-Mo polymetallic deposits in the Jiangnan Fault region (JNF).
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Table
Table 1. Characteristics of Cu–Mo polymetallic deposits in the Jiangnan Fault region (JNF) and Middle-lower Yangtze River Metallogenic belt (MLYRB).
Table 1. Characteristics of Cu–Mo polymetallic deposits in the Jiangnan Fault region (JNF) and Middle-lower Yangtze River Metallogenic belt (MLYRB).
Deposit/County/ProvinceOre TypeResource (mt, kt)/GradeTectonic SettingWall-or/Host-RocksMajor Ore MineralsAlteration MineralsIntrusions RocksReference
Magushan/Xuancheng/AnhuiSkarn Cu–MoCu: 73 Kt @0.6–1.2%; Mo: 8.0Kt @ 0.06–0.12%Northeastern part of the JNFPermian Gufeng-Qixia Fm. LimestoneChalcopyrite, molybdenite, pyriteGrt, Di, Cal, Chl, Ep, KfsGranodiorite,This study
Matou/Chizhou/AnhuiPorphyry Cu–MoMo: 40 Kt @ 0.052%; Cu: >10 Kt @0.2–0.9%Southern part of the JNFSilurian siltstone, shaleMolybdenite, chalcopyrite, pyriteKfs, Ser, Chl, Ep146.7 Ma Granodiorite porphyry[11]
Jitoushan/Chizhou/AnhuiSkarn Cu–Mo–WW: >10 Kt @?; Mo: >10 Kt @?Southern part of the JNFCambrian Yangliugang
Fm. limestone		Scheelite, molybdenite, chalcopyriteGrt, Di, Fl, Ep, Cal, Chl138 Ma Granodiorite[12]
Pailou/Chizhou/AnhuiMo–AuMo: ? @ 0.04–0.13%; Au: ? @ 1.19–22.0 g/tSouthern part of the JNFSilurian-Devonian clastic sedimentary rocksPyrite, molybdenite, stibniteKfs, Ser, Chl, Ep148 Ma Granodiorite porphyry[13]
Anzhishan/Chizhou/AnhuiCu–MoCu: ? @ 0.25–1.0%; Mo: ? @ 0.04–0.1%Southern part of the JNFOrdovician carbonate and Silurian clastic rockschalcopyrite, molybdenite, pyrite, pyrrhotiteCal, Ser, Grt, Chl, DiGranodiorite porphyry[13]
Tongshankou/Daye/HubeiP–S Cu–MoCu: 0.5 Mt @ 0.9–1.0%; Mo: 2 Kt @ 0.02–0.07%Middle-lower Yangtze river Metallogenic beltEarly Triassic Daye Gp.
carbonates		Chalcopyrite, bornite,
molybdenite		Kfs, Bt, Ser, Chl, Grt, Di140.6 Ma Granodiorite porphyries[24]
Chengmenshan/Ruichang/JiangxiP–S Cu–MoCu: 3.07 Mt @ 0.75%; Mo: >10 Kt @ 0.05%Middle-lower Yangtze river Metallogenic beltSilurian-Triassic clastic
rocks and carbonate		Chalcopyrite, scheelite, molybdeniteQ, Cal, Grt, Kfs, BtEarly Cretaceous
Granodiorite porphyry		[2]
Hucunnan/Tongling/AnhuiSkarn Cu–MoMo: ? @ 0.07–0.12%; Cu: 2Mt@ 0.4–0.8%Middle-lower Yangtze river Metallogenic beltPermian Qixia Fm.Molybdenite, chalcopyrite, pyriteQ, Grt, Di, Cal137.5 Ma Granodiorite porphyry[25]
The Jiangnan Fault region (JNF): A transitional zone between Jiangnan domain belt (JNB) and Middle-lower Yangtze River Metallogenic belt (MLYRB). Grt—garnet; Bt—biotite; Chl—chlorite; Ep—epidote; Tr—tremolite; Kfs—K-feldspar; Cal—calcite; Fl—fluorite; Act—actinolite; Pl—plagioclase; Di—diopside; Ser—sericite; Q—quartz.

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Qi, H.; Lu, S.; Yang, X.; Zhou, Y.; Zhao, L.; Deng, J.; Li, J. Formation of the Granodiorite-Hosting Magushan Cu–Mo Polymetallic Deposit in Southern Anhui, Eastern China: Evidences from Geochronology and Geochemistry. Minerals 2019, 9, 475. https://doi.org/10.3390/min9080475

AMA Style

Qi H, Lu S, Yang X, Zhou Y, Zhao L, Deng J, Li J. Formation of the Granodiorite-Hosting Magushan Cu–Mo Polymetallic Deposit in Southern Anhui, Eastern China: Evidences from Geochronology and Geochemistry. Minerals. 2019; 9(8):475. https://doi.org/10.3390/min9080475

Chicago/Turabian Style

Qi, Huasheng, Sanming Lu, Xiaoyong Yang, Yuzhang Zhou, Lili Zhao, Jianghong Deng, and Jianshe Li. 2019. "Formation of the Granodiorite-Hosting Magushan Cu–Mo Polymetallic Deposit in Southern Anhui, Eastern China: Evidences from Geochronology and Geochemistry" Minerals 9, no. 8: 475. https://doi.org/10.3390/min9080475

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