Genesis of the Pb−Zn deposits of the Qingchengzi ore field, eastern Liaoning, China: Constraints from carbonate LA−ICPMS trace element analysis and C–O–S–Pb isotopes

Genesis of the Pb−Zn deposits of the Qingchengzi ore field, eastern Liaoning, China: Constraints from carbonate LA−ICPMS trace element analysis and C–O–S–Pb isotopes

Accepted Manuscript Genesis of the Pb−Zn deposits of the Qingchengzi ore field, eastern Liaoning, China: constraints from carbonate LA−ICPMS trace ele...

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Accepted Manuscript Genesis of the Pb−Zn deposits of the Qingchengzi ore field, eastern Liaoning, China: constraints from carbonate LA−ICPMS trace element analysis and C −O−S−Pb isotopes Xiao-xia Duan, Qing-dong Zeng, Yong-bin Wang, Ling-li Zhou, Bin Chen PII: DOI: Reference:

S0169-1368(17)30223-8 http://dx.doi.org/10.1016/j.oregeorev.2017.07.012 OREGEO 2282

To appear in:

Ore Geology Reviews

Received Date: Revised Date: Accepted Date:

25 March 2017 2 July 2017 10 July 2017

Please cite this article as: X-x. Duan, Q-d. Zeng, Y-b. Wang, L-l. Zhou, B. Chen, Genesis of the Pb−Zn deposits of the Qingchengzi ore field, eastern Liaoning, China: constraints from carbonate LA−ICPMS trace element analysis and C−O−S−Pb isotopes, Ore Geology Reviews (2017), doi: http://dx.doi.org/10.1016/j.oregeorev.2017.07.012

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Genesis of the Pb−Zn deposits of the Qingchengzi ore field, eastern Liaoning, China: constraints from carbonate LA−ICPMS trace element analysis and C−O−S−Pb isotopes

Xiao-xia Duana*, Qing-dong Zengb, Yong-bin Wangb, Ling-li Zhoub, Bin Chena a

School of Resources and Environmental Engineering, Hefei University of Technology, Hefei

230009, China b

Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy

of Sciences, Beijing 100029, China

Abstract The Qingchengzi ore field is an important Pb−Zn polymetallic ore district located in northeastern China, where more than ten Pb−Zn deposits and several Au-Ag deposits occur. The Pb−Zn mineralization is mainly hosted in the marble of the Dashiqiao Formation. Three distinct mineralization styles (strata-bound, open-space-filling and transitional type) are recognized. Two genetic models have been proposed to explain the Pb−Zn mineralization in this district: the sedimentary-exhalative model and the superimposed multi-stage model, in which syn-sedimentary deposition is overprinted by metamorphic and magmatic hydrothermal modification. Based on these three mineralization styles, this study provides new C−O−S−Pb isotopic data and LA−ICPMS trace element analyses of carbonates in order to place more constraints on the genesis of the Pb−Zn deposits. The δ13CPDB values of the syn-ore carbonates range from -5.11‰ to -1.06‰, and their δ18OSMOW values range from 3.30‰ to 13.2‰; these values are distinctively lower than those of barren meta-sedimentary rocks (δ13C = -1.98‰ − -0.55‰, δ18O= 19.69‰ − 22.76‰). The depleted C−O isotopic values of syn-ore carbonates are inferred to result from fluid-rock interactions combined with the impact of graphite. In situ LA−ICPMS trace element analyses show that syn-ore carbonates record enriched REE contents, pronounced positive Eu anomalies and lower Y/Ho ratios compared to barren carbonates. The depleted C−O isotopic signatures and distinctive REE characteristics of syn-ore carbonates indicate that the hydrothermal fluid is likely magmatic in origin and has mixed with low 1

δ18O fluids, such as meteoric or formation water. Sulfide minerals have δ34S values ranging from 3.16‰ to 9.14‰ and display a gradually increasing trend from open-space-filling to transitional type to strata-bound mineralization styles, which reflect different mixing proportions of the two end-members of magmatic sulfur and sedimentary sulfur. The Pb isotopic compositions of sulfide minerals are relatively uniform (206Pb/204Pb = 17.511−17.883, 207Pb/204Pb = 15.549−15.64 and 208Pb/204Pb = 37.670 − 38.178) for different mineralization styles; however, the open-space-filling mineralization records relatively lower lead isotope values. The linear correlation of ore lead isotopes between schist and Triassic intrusions indicates that lead may have originated from a mixture of magmatic and sedimentary end-members. The relatively lower Pb isotopes of the open-space-filling mineralization suggest the presence of higher proportions from a magmatic source. Mineralization styles respond to diverse ore-controlling structures and their proximity to the mineralizing source: open-space-filling mineralization shows the least stratigraphic control, with more pronounced “magmatic marks” (i.e., lower S−Pb isotopic values and more depleted C−O values), compared to strata-bound mineralization. These mineralization styles, combined with C−O−S−Pb isotopic geochemistry, consistently preclude a SEDEX origin for the Pb−Zn deposits in the Qingchengzi district, but suggest that they represent a distal hydrothermal mineralization type related to Triassic magmatic activity.

Keywords: C−O−S−Pb isotope; Carbonate LA−ICPMS trace element; Carbonate replacement Pb−Zn mineralization; Jiao−Liao−Ji Belt

1. Introduction The Qingchengzi ore field is an important Pb−Zn polymetallic ore district that is located in eastern Liaoning, to the northeast of the NCC (North China Craton). The mining history of Qingchengzi can be traced back to the Ming dynasty (400 years ago), when silver was mined by local people. The massive exploration of Pb and Zn began last century, when more than 10 Pb−Zn deposits were discovered successively. Several Au-Ag deposits have been found in the periphery of these Pb−Zn deposits in recent years, and the latest exploration discovered skarn Mo mineralization. In total, 12 large-scale Pb−Zn deposits and 4 Au-Ag deposits have been found clustered within the Qingchengzi ore field with proven metal reserves of 150 Mt Pb+Zn, 200 t Au and 1100 t Ag. Many studies have been conducted 2

that have mainly focused on the Pb−Zn deposits, including the geochemical features (Jiang, 1987, 1989; Chen, 2000; Chi, 2002; Chen et al., 2004), structural characteristics (Jiang and Liu, 1990; Liu, 1995; Liu and Ai, 2001), source and geochronology of the ore (Sun et al., 1997; Liu and Ai, 2002; Xue et al., 2003; Yu et al., 2009). The genesis of the Pb−Zn mineralization has long been debated, and two prevailing models have been proposed: 1) strata-bound sedimentary exhalative (metamorphic) mineralization (Deng, 1983; Zhang et al., 1984; Liu et al., 2007; Song, 2010; Wang et al., 2014); and 2) multistage Paleoproterozoic exhalative mineralization overprinted by metamorphic and magmatic hydrothermal modification (Jiang, 1989; Li, 2005; Wang et al., 2010; Ma et al., 2013). The key dispute focuses upon determining whether the Paleoproterozoic SEDEX (metamorphism) or the Mesozoic magmatic hydrothermal event is the most “economical” mineralization event responsible for the Pb−Zn mineralization. Based on evidence collected during field observations, including ore morphologic, textural and mineralogic data, this paper uses the integrated analysis of C−O−S−Pb isotopic compositions and the results of in situ LA−ICPMS trace element analyses of carbonates to constrain the sources of ore-forming fluids and metals and to clarify the dominant genetic model for Pb−Zn mineralization in the Qingchengzi ore field.

2. Regional geological setting Qingchengzi district (123°33′03″−123°42′42″E, 40°41′11″−40°46′14″N) is situated in the Liaodong Peninsula, which is located in the northeastern part of the Jiao−Liao−Ji Belt in the NCC. The basement in this area comprises the formation of the Paleoproterozoic Jiao−Liao−Ji Belt, which is overprinted by the Mesozoic subduction-collision event of the Yangtze Block and the NCC, which was followed by a subsequent Pacific subduction event. The Jiao−Liao−Ji Belt lies at the eastern margin of the Eastern Block of the NCC and is one of three major Paleoproterozoic orogenic/mobile belts in the NCC. The Jiao−Liao−Ji Belt represents the collisional orogenic belt between the Longgang Block in the north and the Nangrim Block in the south. The tectonic setting and evolution of the Jiao−Liao−Ji Belt is controversial, and two competing models have been proposed: an arc-continent collision model, suggesting the development of an island arc and its subsequent collision with continental blocks (Bai, 1993; Faure et al., 2004; Lu et al., 2006; Tam et al., 2011, 2012a,b; Li and Chen, 2014); and an intra-continental rift model, including the opening and closing of a Paleoproterozoic intra-continental rift (Luo et al., 2004, 2008; Li et al., 2005, 2011; Zhao et al., 2005; Li and Zhao, 2007; Lan et al., 3

2015). The Jiao−Liao−Ji Belt is a narrow, elongated domain that trends in the NE−SW direction for 700 km from eastern Shandong through eastern Liaoning and southern Jilin and extends to northern North Korea (Fig. 1). This belt consists of a suite of greenschist- to lower amphibolite-facies metamorphosed volcanic-sedimentary successions and voluminous intrusions. The volcanic-sedimentary succession is composed of a basal clastic-rich sequence with a lower bimodal volcanic sequence, a middle carbonate sequence, and an upper pelite-rich sequence; it formed at 2.24−2.02 Ga and was metamorphosed at 1.93−1.85 Ga (Luo et al., 2004, 2008; Li et al., 2005; Lu et al., 2006; Wan et al., 2006; Li and Zhao, 2007; Zhou et al., 2008). Although the successions present in different regions are comparable in their lithology and geochronology, they are variably named the Fengzishan and Jingshan groups in eastern Shandong; the Liaohe group in eastern Liaoning, the Ji’an and Laoling groups in southern Jilin, and the Macheonayeong group in North Korea (Zhao et al., 2005). Associated with these sedimentary and volcanic successions are Paleoproterozoic granitoids and mafic intrusions (gabbros and dolerites). The granitoid plutons are composed of deformed granites (i.e. hornblende/biotite monzogranitic gneisses) which were emplaced at 2.17−2.09 Ga and metamorphosed at ~1.9 Ga and undeformed porphyritic monzogranites and granites and alkaline syenites which were intruded at 1.87−1.85 Ga (Lu et al., 2006; Wan et al., 2006; Li and Zhao, 2007; Tam et al., 2011). In addition, the pelitic granulites of the South Liaohe groups record evidence of widespread anatexis (partial melting), which produced various felsic irregular veinlets, stockworks and lenticular bodies in the host rocks (with gradual transition relationships). This regional partial melting event was dated at 1.84−1.86 Ga, which suggests that widespread anatexis occurred during the post-peak low-pressure granulite-facies metamorphic stage of the exhumation of the Jiao−Liao−Ji orogenic belt (Liu et al., 2015). During the Mesozoic, the studied region was reactivated and impacted by three major tectonic events, namely, the Central Asian orogenic belt on its northern margin, the Dabie−Sulu orogenic belt on its southern segment and the subduction of the Pacific Plate on its eastern margin. In response, various and vast amounts of magmatic rocks developed in this region, among which the proportion of Late Triassic magmatic rocks (231−210 Ma) was relatively minor. This episode of magmatism, which predominantly comprises alkaline intrusions and associated mafic rocks, as well as granites with enclaves, are documented along Jiaodong-Liaodong and extend north into Korea, which constitutes one Late Triassic magmatic rock belt along the northeastern flank of the Sulu orogenic belt (Yang et al., 4

2005, 2007a, b, 2012; Cho et al., 2008; Peng et al., 2008; Williams et al., 2009). These magmatic rocks are interpreted to be associated with the post-collisional extension of the Yangtze Craton and the North China Craton in the Late Triassic (Chen et al., 2003; Yang and Wu, 2009; Seo et al., 2010). Since the Late Mesozoic, the Liaodong Peninsula has existed within the circum-Pacific tectonic regime, which is characterized by Kula-Pacific Plate subduction and large-scale lithospheric thinning that has induced the following intensive magmatism: (1) the formation of Jurassic (180−153 Ma) tonalite, diorite and gneissic two mica monzogranite, which have experienced ductile deformation; and (2) the formation of Early Cretaceous (131−120 Ma) undeformed to slightly deformed diorite, granodiorite, monzogranite and syenogranite (Wu et al., 2005a,b; Yang et al., 2007a,b, 2012). The Jiao−Liao−Ji Belt is host to both metallic and nonmetallic resources. There are numerous Pb−Zn, Au−Ag, Cu−Co, and Fe deposits that constitute a Pb−Zn−Au−Ag polymetallic ore belt (Fang et al., 1994). In addition, the belt is well-known for its abundant magnesite, talc and boron resources, and several world-class deposits clustered within the belt (i.e., the Haicheng magnesite deposit, the Houxianyu boron deposit, and the Liangshanguan uranium deposit, among others) (Zhang et al., 1988; Chen and Cai, 2000; Zhai, 2005).

3. Geology and mineralization of the Qingchengzi ore field 3.1 Geology of the Qingchengzi ore field The Qingchengzi ore field is largely covered by the Paleoproterozoic Liaohe Group and contains minor outcrops of the Archean Anshan Group (Fig. 2). The Anshan Group, which comprises migmatite and migmatitic granite (aged 3.85−3.2 Ga), represents the basement of this district. Unconformably overlying the Anshan Group is the Liaohe Group, which contains the most important ore-bearing rocks and is further divided into three formations. At the bottom is Gaojiayu Formation which comprises graphite marble, hornblende schist, and wollastonite mica schist. The middle Dashiqiao Formation is composed of dolomitic marble, banded mica marble, tremolite marble, garnet mica schist, and wollastonite mica schist. The Dashiqiao Formation is subdivided into several horizons, which (from bottom to top) are D1, which is a banded graphite-bearing marble; D2, which is a garnet and sillimanite mica schist; D31, which comprises granulite and banded marble interbedded with tremolite marble; D32, which contains mica schist and sillimanite mica schist; D33, which includes dolomite marble and 5

tremolite marble; D34, which comprises leucoleptite and schist; and D35, which consists of dolomite marble and calcite marble. The upper Gaixian Formation mainly consists of mica schist (i.e., mica schist, wollastonite mica schist, and garnet mica schist) with thin layers of marble at the bottom. The Dashiqiao Formation contains the main ore-bearing strata of the Pb−Zn orebodies, while Ag−Au orebodies are mainly hosted in the Gaixian Formation. The Qingchengzi ore field has undergone multiple periods of tectonic and magmatic activity. Various folds and faults comprise the basic structures of the ore field. The NW-trending Jianshanzi fault and the NE-trending Erdao fault confine the frame of the district (Fig. 2). A series of secondary fractures trending to the NW and NE form a diamond-shape pattern; ore-bearing veins, as well as hundreds of small dykes, are also oriented to the NE and NW. There are also several EW-trending broad folds that were formed during the divergent stage of the Liaoji Rift, including the Xinling anticline, the Sikeyangshu syncline, the Zhenzigou anticline and the Nanshan syncline. In addition, some folds were subjected to secondary deformation and have thus formed inverted folds (Fang et al., 1994; Liu, 1995). Magmatism in this district is represented by multiple-stage felsic and mafic igneous rocks (Fig. 2). Three main stages of magmatism occurred during the Paleoproterozoic, the Late Triassic and the Jurassic. Paleoproterozoic magmatism is represented by the Dadingzi intrusion, which crops out in the eastern part of the ore field with a reported K−Ar isochron age of 1620−1740 Ma (Rui et al., 1994). In addition, many Paleoproterozoic granites occupy the core of folds. Late Triassic magmatism was intensive and produced both felsic intrusions and mafic dykes. These felsic intrusions are represented by the Xinling stock (~2 km2) and the Shuangdinggou intrusion (~300 km2), which crop out in the northern and southwestern regions of the district, respectively. Lithologically, the Xinling stock comprises granite porphyry with a porphyritic texture. The Xinling stock records pervasive alteration, including silicification, pyritization and kaolinization. The Shuangdinggou intrusion is a biotite monzogranite that exhibits a porphyritic texture and is relatively fresh. Zircon LA−ICPMS U−Pb ages of 224.2±1.2 Ma and 226.2±1.8 Ma were obtained for the Shuangdinggou and Xinling intrusions, respectively (Duan et al., 2014). In addition, there are also many granite porphyry dykes in the eastern and middle parts of the district, which are closely related to Pb−Zn mineralization. Evidence of Late Triassic mafic magmatic activities mainly include the presence of diorite and lamprophyre dykes. The diorite dyke, which has an emplacement age of 220−214 Ma (Wu et al., 2005), is more than 10 km long 6

and cuts through Paleoproterozoic strata. The lamprophyre dykes are widespread throughout the district; they are generally NE-orientated, 50−500 meters long and 1−10 meters wide. They usually intrude into the marble of the Dashiqiao Formation and the schist of the Gaixian Formation. Jurassic magmatism is represented by the Yaojiagou granite. Zircon LA−ICPMS U−Pb dating of this granite intrusion yielded an age of 165.7±1.3 Ma (Duan, 2015).

3.2 Mineralization of the Qingchengzi Ore field More than ten Pb−Zn deposits containing over 200 Pb−Zn orebodies occur within the Qingchengzi ore field. Large-scale Pb−Zn deposits include the Zhenzigou Pb−Zn deposit, the Diannan Pb−Zn deposit, the Xiquegou Pb deposit, the Nanshan Pb deposit, the Benshan Pb deposit and the Erdao Pb-Zn deposit (Fig. 2). These deposits are mainly hosted by the marble of the Dashiqiao Formation and (to a lesser extent) the marble interbeds of the Gaojiayu and Gaixian formations.

3.2.1 Mineralization styles Based on thorough observations of orebody occurrences, ore fabrics, mineral assemblages, and alteration patterns, three distinctive mineralization styles can be recognized (Table 1). The first is a strata-bound style, which was described by previous researchers as being stratigraphically controlled and interpreted to represent a syn-sedimentary deposit (Zhang et al., 1984; Liu et al., 2007; Song, 2010). However, detailed observations suggest that the orebody occurrence is actually controlled by interlayer fractures and/or the interfaces of different lithological units (i.e., marble and mica schist). Strata-bound mineralization generally occurs as massive sulfide replacement bodies hosted in dolomitic marble, which are often shaped as manto to semi-horizontal sheets with large lateral dimensions (Fig. 4a) as well as various lenticular, podiform, and nodular orebodies. In addition, some orebodies display irregular and discordant contacts with their host marble (Fig. 4b). Representative orebodies include the No. 2, No. 320 and No. 321 orebodies in the Zhenzigou deposit, which constitutes a 2500-m-long, NW-trending ore belt striking NW60°−70° and dipping to the NE with angles of 40°−70°. The individual orebodies of the ore belt show lateral and vertical extensions of 100−150 m and 30−90 m, respectively, with thicknesses of 0.5 m ~ 8 m (Fig. 3b). This mineralization style mainly occurs in the Zhenzigou and Diannan deposits and accounts for ~31% of total Pb−Zn reserves, with an average Pb grade of 2.72% and an average Zn grade of 2.58% (103GT, 1976). The second style is open-space-filling mineralization, which has two subtypes. The first is 7

strata-hosted mineralization in the form of steeply dipping veins, stock veinlets, and sacciform and breccia orebodies (Fig. 4c, d, e, f), which are roughly massive replacement bodies that crosscut bedding. The most striking feature is the strict structural control of orebody occurrences, as orebodies develop along faults, aside lamprophyre dykes or in fractured zones. Orebodies are strictly controlled by NE-trending faults (i.e., the No. 1 and No. 122 faults), and the major mining ore veins No. 6404 and No. 426 occur at the footwall of the No. 1 Fault in the Xiquegou deposit. A series of ore veins collectively form en echelon arrays and constitute a 300-m-long, 300-m-deep and 50-m-wide ore belt that strikes to the NW and pitches to the NE with a pitch angle of 30°. This style of mineralization is widely observed in all deposits, especially in the Xiquegou and Nanshan deposits, and accounts for ~30% of total reserves, with an average Pb grade of 4.42% and an average Zn grade of 1.01% (103GT, 1976). The second is intrusion-hosted mineralization, in which massive coarse-grained sulfide pods and veinlets occur within the granite porphyry and its contact zone with marble (Fig. 4g). Several wide ore veins also occur around the granite porphyry. The intrusion of granite porphyry is controlled by extensional fractures striking to the SN and NNW. The proportion of this style of mineralization is relatively limited, and it is recorded in the 360 m mining level of the Diannan deposit, the 120 m mining level of the Erdao deposit, the No. 614 orebody of the Benshan deposit and the drill core of the Xinling granite. The third type is transitional type mineralization, which occurs where the main fault intersects favorable interlayer fractures. The orebodies display irregular shape, which is formed by the filling of the main fault and replacement along the secondary interlayer fractures between the marble and schist (Fig. 4h). This mineralization style tends to favor the footwall of the fault, and the size of the orebody is confined by the angle between the main faults and the interlayer fractures; the smaller the angle is, the larger the size is. This style of mineralization is widely developed in the Nanshan (Fig. 3a), Diannan and Zhenzigou deposits and represents up to ~30% of total reserves. Its representative orebody is the No. 1 vein in the Nanshan deposit, which strikes NE 20°−40° and dips to the SE with a dipping angle of 10°−30°. The ore vein is 1−2 m thick; it has a lateral extent of 100 m and a vertical extent of 40−50 m. The strata-bound mineralization is controlled by interlayer fractures, whereas the open-space-filling mineralization is controlled by main faults. These two could be linked by the transitional type mineralization, which is controlled by the combination of the main fault and secondary interlayer fractures. These three mineralization styles are considered to represent the same event of structurally 8

controlled mineralization, in which their different morphologies and occurrences are due to the different controlling structures of the host rocks. The dominant ore minerals of the Pb−Zn deposits include pyrite, sphalerite, galena, arsenopyrite, and chalcopyrite, as well as minor amounts of pyrrhotite, tetrahedrite and argentite; gangue minerals mainly consist of dolomite and subordinate quartz and calcite. The ore assemblages of the strata-bound mineralization are characterized by varying proportions of sphalerite, galena, and pyrite with gangue minerals of dolomite, subordinate calcite and rare quartz. Those ores exhibit massive, semi-massive, banded or disseminated structures (Fig. 5a). The dominant sulfides of the open-space-filling mineralization are galena and pyrite, but minor amounts of arsenopyrite, chalcopyrite, and pyrrhotite are also present. Sphalerite is absent or notably less abundant than it is in the strata-bound mineralization. The ores exhibit massive and veinlet structures (Fig. 5b, c). The ore assemblages of transitional type mineralization are similar to those of the open-space-filling style (Fig. 5d). The sulfide assemblages vary within different parts of an individual orebody. The center of the orebody is composed of abundant galena and/or sphalerite, while the abundance of pyrite increases and that of economical sulfide decreases moving to the outskirts of the orebody. Alteration associated with the strata-bound ores is not obvious. Contacts between sulfide bodies and their host marbles are abrupt in some places. Extensive carbonate recrystallization and the replacement of calcite and dolomite by hydrothermal dolomite, calcite, quartz, and sericite are prevalent throughout the ore field. The alteration styles of the intrusion-hosted mineralization are distinct compared to those of the strata-hosted mineralization. The former records evidence of strong and pervasive silicification and sericitization, whereas the latter records locally weak silicification and sericitization.

3.2.2 Paragenetic sequences Based on the crosscutting relationships between ore veins, the occurrence of mineral assemblages, and the textural/growth relationships between minerals, two metallogenic periods can be distinguished and the paragenetic sequences of ore minerals can be inferred (Fig. 6). The first stage is an early preliminary enrichment period, which includes sedimentary deposition and metamorphic modification; this sedimentary stage is recorded by very fine-grained disseminated pyrites with rounded shapes (Fig. 7a). This very early stage is not commonly observed, and its mineral assemblages rarely include sphalerite or galena, thus demonstrating that it has little economic importance. The metamorphic stage 9

is recognized based on the intergrowth relationship of fine-grained sphalerite ± galena with graphite in lamellar ores. Sphalerite, which is usually light brown in color, is disseminated or banded with chlorite or carbonate; it is also commonly replaced by later hydrothermal quartz and carbonates and displays embayed structures. Graphite is common and is intimately associated with sulfide minerals (Fig. 7b). Primary graphite stripes are usually banded and display a preferred alignment (Fig. 7d). In other cases, graphite recrystallizes to a tabular shape or occurs as remnants of later hydrothermal modification. The second hydrothermal mineralization period is the dominant one. Ore veins cut through the graphite alignment and crosscut the foliation of metamorphosed lithologies (Fig. 7d), thus indicating that vein-type mineralization occurred after metamorphism. In addition, in most regions, graphite is absent or only occurs as small remnants left following intensive replacement (Fig. 7c). This period is subdivided into three stages: Stage I features a dolomite-quartz-pyrite assemblage. Pyrite is the main sulfide in this stage and is disseminated as coarse-grained euhedral cubes (0.1–0.3 mm). Pyrite is commonly replaced by sphalerite and galena and exhibits embayed and skeletal textures (Fig. 7e). Stage II is characterized by a pyrite-arsenopyrite-sphalerite-galena-chalcopyrite-dolomite assemblage, and its principal ore minerals are galena, pyrite and sphalerite. Relatively euhedral, reddish-brown sphalerite coexists with recrystallized dolomite. Sphalerite commonly develops chalcopyrite disease and displays banded or latticed chalcopyrite exsolution structures. Galena is often intergrown with argentite and commonly replaces pyrite, sphalerite and dolomite/quartz along the margins and internal fractures of primary minerals; it also exhibits stock veins or embayed structures (Fig. 7f, g). Stage III features prismatic quartz replacing sphalerite and galena as well as dolomite or post-ore calcite ± quartz veins (Fig. 7h), which sometimes contain disseminated fine-grained galena and pyrite. The early sedimentary-metamorphic period only produced fine grained sphalerite and galena, which contribute little to the total metal reserves. In contrast, the hydrothermal mineralization period is the most economically important and is thus the main focus of this study.

4. Sampling and analytical methods Nine carbonate mineral samples displaying paragenetic relationships with Pb−Zn mineralization were selected for C−O isotopic analysis. Additionally, five carbonate samples collected from barren meta-sedimentary rocks were also analyzed for comparison. A total of 45 sulfide (pyrite, galena, sphalerite) samples representing different mineralization styles were widely selected from five deposits 10

(the Xiquegou, Nanshan, Zhenzigou, Diannan and Benshan deposits) for sulfur isotopic measurements. In addition, 33 sulfide samples of different mineralization styles were selected for lead isotopic analysis. Meanwhile, host meta-sedimentary and magmatic rocks were also collected to conduct lead isotopic analysis for comparison, including 13 meta-sedimentary rock samples collected from different formations and 11 magmatic rock samples covering different stages and lithologies. All samples were collected from underground tunnels, except for magmatic rock samples. Paragenetic relationships were first studied in thin section, and all analyzed minerals were handpicked under a binocular microscope to reach >95% purity. Minerals and rock samples were then milled to a size of 200 mesh in an agate mortar. C-O-S isotopic analyses were conducted at the Laboratory for Stable Isotope Geochemistry, Institute of Geology and Geophysics, Chinese Academy of Sciences. For C−O isotopic analysis, approximately 5−10 mg of dry sample powder was dissolved with H3PO4 at 70 °C. After being fully digested, CO2 was reconverted and cryogenically trapped in liquid nitrogen traps (-195℃). The trapped CO2 was then cryogenically transferred to a sample flask and sealed for analysis, which was performed using a MAT253 Thermo Fisher mass spectrometer. Measured C and O isotopic ratios were reported relative to VPDB (Peedee Belemnite), which can be converted to VSMOW using the equation δ18OSMOW=1.03086×δ18OPDB+30.86 (Friedman and O'Neil, 1977). The analytical precision of these measurements is better than 0.2‰. The sulfur isotopic compositions of pyrite, sphalerite, and galena were determined. Sulfide samples were combusted with excess CuO2 and SO2 was produced during the oxidation reaction at 980℃ in a 2.0×10-2 Pa vacuum state. All SO2 gas was collected at vacuum using the frozen method and was analyzed using the MAT253 mass spectrometer. Sulfur isotopic compositions are reported in per mil, relative to the Vienna Canyon Diablo Troilite (CDT) standard. The analytical precision is better than 0.2‰. Lead isotopic compositions were analyzed at the Beijing Institute of Uranium Geology. Measurements were conducted using an ISOPROBE-T Thermal Ionization Mass Spectrometer (TIMS). Approximately 200 mg of sulfides were completely dissolved in crucibles in an ultrapure acid mixture of HClO4 + HF. The residue was redissolved in HCl, dissolved in 0.5 M HBr and then loaded into a column with 50 ml of AG 1-X8 anion resin to separate out the Pb fraction. The extracted Pb was further purified in a second column using a similar method (Belshaw et al., 1998). Errors were numerically propagated throughout all calculations and are reported at the 2σ level. The analytical results for the standard NBS981 are 206Pb/204Pb = 16.937 ± 0.002, 207Pb/204Pb = 11

15.457 ± 0.002 and 208Pb/204Pb = 36.611 ± 0.004 (2σ, n=10); these values are in agreement with the reference values. In situ trace element analyses of carbonates were carried out at the Institute of Geology and Geophysics, Chinese Academy of Sciences. These analyses were performed using an ArF excimer laser ablation system operating at a wavelength of 193 nm (Geolas, Pro, made by Coherent GmbH, Germany), coupled to an Agilent 7500a quadrupole ICP-MS. Ablation was performed on polished thin sections of mineral grains that had previously been analyzed by electron microprobe. Helium was applied as the carrier gas; argon was used as the make-up gas, which was mixed with helium before entering the ICP torch in order to obtain stable and optimal ionization efficiency. The carrier and make-up gas flows were optimized by ablating NIST SRM 610 in order to obtain maximum signal intensities (238U counts >200 Mcps) while reducing oxide ratios (UO+/U <0.5%). The ablation spot sizes during carbonate analyses ranged from 40–60 µm, and the laser used a pulse speed of 4 Hz and an energy density of 10 J/cm2. For each analytical spot, 20 s of background acquisition were followed by 65 s of data acquisition. One analysis of NIST SRM 612 was performed after every 10 spot analyses in order to correct for the time-dependent sensitivity drift and mass discrimination of the ICP-MS. In this method, measurements are calibrated against an external standard (SRM 612), and normalization is performed using 43Ca as internal standard. For a detailed description of this process, refer to Yang et al. (2009). Elemental concentrations were calculated using the GLITTER 4.0 software (Van Achterberg et al., 2001), which yielded an accuracy of better than 10%.

5. Results 5.1. Carbon and oxygen isotopic compositions The carbon and oxygen isotopic data for carbonate minerals are presented in Table 2 and plotted in Fig. 8. The C−O isotopic compositions of syn-ore carbonates are distinct from those of barren meta-sedimentary rocks. Barren rocks record heavy carbon and oxygen isotopic compositions, with high δ13CPDB values ranging from -1.98‰ to -0.55‰ (with an average value of -1.36‰) and distinctively high δ18OSMOW values ranging from 19.69‰ to 22.76‰ (with an average value of 21.22‰). In comparison, ore dolomites have relatively depleted δ13C and δ18O isotopic compositions, which span a wide range and can be subdivided into two distinct groups: group I data record tight 12

distributions of δ13C−δ18O values, with remarkably negative δ13CPDB values ranging from -5.11‰ to -4.71‰ and relatively low δ18OSMOW values ranging from 12.18‰ to 13.16‰. Group II samples record δ13CPDB isotopic compositions ranging from -3.65‰ to -1.06‰; these values are lower than those of barren carbonates but slightly higher than those of group I data. The δ18OSMOW values of group II samples fall within the range of 3.3‰ − 10.88‰ and are thus significantly lower than those of both the group I and barren carbonates. The calculated δ18Ofluid values of group I samples range from 1.83‰ to 2.81‰, while the δ18Ofluid values of group II samples range from -7.06‰ to 1.10‰. Group I samples contain ubiquitous graphite, whereas group II samples commonly do not contain graphite and instead record stronger hydrothermal modification characteristics associated with the second metallogenic period.

5.2. Sulfur isotopic compositions The analyzed sulfur isotopes of 45 sulfide samples from different Pb−Zn deposits in the Qingchengzi ore field are reported in Table 3. Overall, the δ34S values of sulfides fall within a narrow range of 3.16‰ − 9.14‰, with the majority falling between 3‰ − 8‰ (Fig. 9a). Specifically, the δ34S values of sphalerite range from 5.58‰ to 8.25‰, whereas the light brown sphalerite crystals record slightly heavier δ34S values (with most ranging from 7.30‰ to 8.25‰) than the dark brown sphalerite crystals (with most ranging from 5.58‰ to 7.01‰). The δ34S values of galena range from 3.16‰ to 6.40‰, with the majority falling between 3.4‰ − 5.4‰. Pyrite samples record a wider range of δ34S values, ranging from 5.15‰ to 9.14‰. The order of enrichment of δ34S is generally galena< sphalerite< pyrite, which implies that sulfur isotopic equilibrium between sulfides has been reached. The sulfur isotopic compositions record regular changes between different mineralization styles: overall, the open-space-filling mineralization records relatively low δ34S compositions, whereas the strata-bound mineralization records elevated δ34S values with transitional type mineralization in the middle (Fig. 9b).

5.3. Lead isotopic compositions The lead isotopic data of sulfides from different Pb−Zn deposits in the Qingchengzi ore field are presented in Table 4; those of igneous and meta-sedimentary rocks are listed in Table 5. The Pb isotopic data of Pb−Zn ores are relatively uniform: 206Pb/204Pb = 17.511−17.883, 207Pb/204Pb = 15.549−15.64, and 208Pb/204Pb = 37.670−38.178. The Pb isotopic compositions of sphalerite are 206Pb/204Pb = 13

17.666−17.883, 207Pb/204Pb = 15.569−15.600, and 208Pb/204Pb = 37.766−38.066; those of galena are 206

Pb/204Pb = 17.511−17.880, 207Pb/204Pb = 15.549−15.608, and 208Pb/204Pb = 37.670−38.121; and those

of pyrite are 206Pb/204Pb = 17.751−17.800, 207Pb/204 Pb = 15.574−15.640, and 208Pb/204Pb = 37.827−38.178. Although the Pb isotopic compositions of sulfides of different mineralization styles partly overlap with each other, the open-space-filling mineralization records relatively lower lead isotopic compositions on both the 206Pb/204Pb-208Pb/204Pb diagram and the 206Pb/204Pb-207Pb/204Pb diagram (Fig. 10). Magmatic rocks of different stages record uniform lead isotopic compositions. The initial lead isotopes were calculated as follows: the Jurassic Yaojiagou granite has Pb isotopic compositions of 206

Pb/204Pbi = 15.836−16.226, 207Pb/204Pbi = 15.457−15.494 and 208Pb/204Pbi = 35.627−35.876; the

Triassic Shuangdinggou intrusion records initial Pb isotopic compositions of 206Pb/204Pbi = 17.439−17.865, 207Pb/204Pbi = 15.452−15.482 and 208Pb/204Pbi = 35.559−35.737. Triassic mafic dykes record similar lead isotopic compositions of 206Pb/204Pbi = 17.574−17.778, 207Pb/ 204Pbi = 15.464−15.509, and 208Pb/204Pbi = 38.058−38.122. The Paleoproterozoic Dadingzi granite records initial Pb isotopic ratios of 206Pb/204Pbi = 15.596−15.899, 207Pb/204Pbi = 15.455−15.156, and 208Pb/204Pbi = 35.342−35.763. On the other hand, the meta-sedimentary rocks (i.e., marble and mica schist) record significantly different Pb isotopic compositions, which record a much larger spread and are more enriched in heavy lead isotopes: nine marble samples have 206Pb/204Pb ratios of 17.900−39.905, 207Pb/204Pb ratios of 15.562−18.072, and 208Pb/204Pb ratios of 37.075−38.504, whereas four mica schist samples have 206

Pb/204Pb ratios of 18.192−22.297, 207Pb/204Pb ratios of 15.602−16.105, and 208Pb/204Pb ratios of

39.126−42.009.

5.4. LA−ICPMS trace element compositions of carbonates Both syn-ore dolomites from three Pb−Zn ore samples and dolomites from one barren dolomitic marble sample were analyzed; these results are listed in Table 6. Their REE contents are normalized to those of post-Archean Australian shale (PAAS, values from McLenanan, 1989) and are shown in Fig. 11, where the depletion of LREE is indicated by (Nd/Yb)N (Northdurft et al., 2004). The dolomites from the barren marble of the Dashiqiao Formation record low REE contents (∑REE = 17.14−30.56 ppm, with a mean of 25.06 ppm), flat REE patterns and clear enrichments of HREE ((Nd/Yb)N=0.37−0.76), which resemble the patterns of marine carbonates (Elderfield and Greaves,

14

1982). However, they do not exhibit prominent negative Ce anomalies. Their Y/Ho ratios are high (44−69) and have a mean value of 55. In comparison, the dolomites intergrown with sulfides record significantly elevated REE contents (∑REE=22.82−187.22 ppm, with a mean of 102.35 ppm), roof-shaped upward convex REE patterns and marked positive Eu anomalies, with Eu/Eu* values ranging from 1.27 to 4.28 (with an average value of 2.18). The Y/Ho ratios of ore dolomite range from 21 to 44, with a mean value of 35; the majority fall within the range of 29−36. These values are relatively lower than those of the barren dolomite.

6. Discussion 6.1. C−O isotopes and trace elements of carbonates The δ13C and δ18O values of normal marine carbonates are restricted within -1‰ − +2‰ and 10‰ − 26‰, respectively (Shields and Veizer, 2002); thus, the C−O isotopic compositions of barren carbonates in the Qingchengzi ore field (δ13C= -1.98‰ − -0.547‰, δ18O= 19.69‰ − 22.76‰) appear to be consistent with those of normal marine sedimentation. However, the carbon and oxygen isotopic compositions of carbonates can be modified by diagenetic, metamorphic and hydrothermal alteration processes; therefore, any post-depositional processes must first be considered. Metamorphism would decrease the δ13C values of marine carbonates (Rye et al., 1976; Guerrera et al., 1997; Melezhik et al., 2005). Because the Liaohe Group underwent regional lower greenschist- to hornblende-facies metamorphism (1.85−1.93 Ga), the primary sedimentary carbonates would have had higher δ13C compositions. Its positive δ13C values likely reflect the impact of the worldwide 2.06-2.33 Ga Lomgundi Event (also defined as the Great Oxidation Event (GOE)) (Fig. 8), which has already been recognized in contemporary carbonate strata in the Sino-Korean Craton (Chen et al., 2000; Tang et al., 2009; 2011; Song et al., 2011) and particularly the Dashiqiao Formation (Tang et al., 2013a; Fig. 8). The current δ13C and δ18O values represent depleted features modified by post-sedimentation diagenesis and regional metamorphism. The syn-ore carbonates from Pb−Zn deposits record δ13C and δ18O values of -5.11‰− -1.06‰ and 3.30‰−13.16‰, respectively, which are obviously lower than those of barren carbonates. The differences between the ore and barren carbonates indicate that they have different sources or experienced variable isotopic re-equilibrium processes, with the following possibilities: (1) isotopic 15

reset by metamorphic modification: dissolution/decarbonation reactions during metamorphism produce CO2 with δ13C values similar to or more enriched than those of parent rocks (Shieh and Taylor, 1969; Ohmoto and Goldhaber, 1997); however, the δ13C values of syn-ore carbonates in this study are depleted compared to those of the meta-sedimentary rocks. Therefore, this possibility is precluded. (2) The low δ13C values of group I carbonates (-4.71‰ − -5.11‰) are consistent with those of igneous rocks or mantle-derived carbon (-5.0‰ − -8.0‰, Ohmoto, 1986; Bowman, 1998), and are thus indicative of a magmatic origin. Combined with their relatively low δ18O values (δ18OSMOW= 12.18‰ −13.16‰), the ore-forming fluids might be magmatic or deep-seated crustal fluids, which have δ13C values of -4‰ − -9‰ and δ18O values of 6‰ − 15‰ (Zheng and Hoefs, 1993). However, this alternative does not fit the petrological observations of the group II samples. (3) When integrating the two groups of data based on their petrological characteristics, we suggest the two following controlling factors: (a) fluid-rock interactions between dolomitic marble and hydrothermal fluid that is poor in δ13C and δ18O and (b) the impact of graphite. In general, δ18O values record a wider range than δ13C values, since oxygen isotopes are more vulnerable to hydrothermal alteration than carbon isotopes, as hydrothermal alteration can significantly decrease δ18O values (Ohmoto, 1986; Aggarwal et al., 1987; Zheng and Hoefs, 1993; Taylor, 1997). Group I carbonates record pronounced negative δ13C values, which is interpreted to represent the impact of the introduction of organic carbon, which is consistent with widely dispersed graphite present in group I samples. The CO2 generated through the thermal decomposition of organic matter and/or graphite (δ13C = -25 ~ -10%) in sedimentary rocks could effectively produce negative 13C values (Valley, 1986). Group II carbonates, which are absent of graphite, record higher δ13C values that range between those of dolomitic marble and mantle-derived fluids, thus reflecting normal fluid-rock interactions without the impact of graphite. The narrow range of δ18O values of group I carbonates suggests that fluid-rock interaction is relatively limited. In comparison, group II carbonates record variable and pronounced lower δ18O values, which indicate intensive hydrothermal modification, as well as large variations of isotopic compositions, which reflect different degrees of fluid-rock interaction. In addition, the calculated δ18Ofluid values of fluid (-7.06‰−2.81‰) record depleted oxygen isotopic compositions compared to those of magmatic water (6‰−10‰, Sheppard 1986). Integrating this isotopic feature with the trace element characteristics of syn-ore carbonates (see below) indicates that the hydrothermal fluid is likely magmatic in origin and has mixed with low-δ18O fluids, such as meteoric water or formation water. In addition, due to the 16

modification of hydrothermal fluids, mineralized carbonate strata display patterns of C−O isotopic halos that are specialized for different mineralization styles. For SEDEX-type mineralization, the mineralized carbonate rocks record δ18O-enriched and δ13C-depleted isotopic signatures relative to those of barren host rocks (Large et al., 2001), whereas skarn deposits and Pb−Zn−Ag manto deposits are reported to record carbon and oxygen isotopic depletion halos in carbonates (Megaw et al., 1988; Naito et al., 1995; Kesler et al., 1997; Bonsall et al., 2011). The C−O isotopic data of Qingchengzi record patterns that are more similar to those of skarn-type mineralization than SEDEX-type mineralization (Fig. 12). However, due to the addition of non-magmatic material, they deviate from the skarn pattern, especially for open-space-filling mineralization samples. In situ trace element analyses show that syn-ore carbonates and barren carbonates have distinct REE compositions. The low REE contents and relatively enriched HREE features of barren carbonates are indicative of marine sediments and are comparable to those of the Guanmenshan Formation of the Liaohe Group (Tang et al., 2013b). Seawater is characterized by low REE abundances, the depletion of LREE relative to HREE, high Y/Ho ratios and negative Ce anomalies (Elderfield and Greaves, 1982; De Baar et al., 1985; Northdurft et al., 2004), which are then inherited by carbonates formed in marine environments. However, diagenetic and/or metamorphic overprints might cause some minor deviation of REE patterns from the ideal marine signature (Hecht et al., 1999). The absence of Ce anomalies in the barren carbonates in the Qingchengzi ore field might be the result of metamorphic processes. By comparison, syn-ore carbonates are significantly enriched in REE (∑REE ~100 ppm, compared to the ~25 ppm of barren carbonates) and exhibit pronounced positive Eu anomalies and lower Y/Ho ratios relative to barren carbonates. Positive Eu anomalies can develop at high temperatures (generally those above 200−250°C) (Michard, 1989; Bau, 1991; Bolhar et al., 2004). Intensive hydrothermal alteration associated with metamorphic processes results in negative Eu anomalies in carbonate rocks (Bau and Möller, 1993). Therefore, the positive Eu anomalies and flat REE patterns of syn-ore carbonates are indicative of high-temperature hydrothermal fluid. These rocks are subjected to metasomatism by hydrothermal fluids that are unlikely to have been derived from metamorphic process. Y and Ho are geochemical elements that behave coherently in most geological environments (Bau and Dulski, 1999), and the Y/Ho ratios of different aqueous systems have distinct characteristics. Seawater is characterized by high Y/Ho ratios (44–74, Zhang et al., 1994; Bau et al., 1995; Nozaki et al., 1997; Bolhar et al., 2004), and sedimentary carbonates have similar or slightly lower Y/Ho ratios than seawater. Thus, a 17

hydrothermal fluid that mobilizes Y and REE from a marine limestone sequence displays Y/Ho ratios similar to those of sedimentary carbonates (Bau, 1996), which means that the hydrothermal carbonates of SEDEX deposits should have high Y/Ho ratios (>44). The Y/Ho ratios of magmatic hydrothermal origins are lower (Y/Ho = 23–33, Bau, 1996). In addition, the Y/Ho ratios of the syn-ore carbonates of the Qingchengzi Pb−Zn deposits mostly range from 27 to 44, thus suggesting that some amount of magmatic fluids have been involved. Syn-ore carbonates are significantly different from barren carbonates in terms of both their trace element compositions (i.e., enriched REE contents, pronounced positive Eu anomalies and lower Y/Ho ratios) and isotopic compositions (i.e., lighter C−O isotopes) which indicate that the origin of the ore-forming fluids is not seawater and that high-temperature magmatic hydrothermal fluids are involved.

6.2. Possible sources of sulfur The Pb−Zn ores from the Qingchengzi ore field record simple mineral assemblages of galena, sphalerite, pyrite, and arsenopyrite, with no record of sulfate. This lack of sulfate implies that the fluid is dominated by H2S and thus that the δ34S values of sulfides approximately represent the bulk sulfur compositions of the fluid i.e., δ34SΣS≈δ34Ssulfide (Ohmoto, 1972; Seal, 2006). In addition, many studies have shown that sulfur isotopes essentially remain unmodified during metamorphic recrystallization and remobilization (Oliver et al., 1992; Cook and Hoefs, 1997; Alirezaei and Cameron, 2001; Wagner and Boyce, 2006; Bailie et al., 2010), thus suggesting that the original sulfur isotopic compositions have been largely preserved during metamorphic events. Sulfides in the Qingchengzi ore field record enriched δ34S values of 3.2‰ − 9.1‰ (Fig. 9); this narrow spread of δ34S values suggests relatively constant physicochemical conditions during ore deposition (Ohmoto, 1986; McCuaig and Kerrich, 1998). Here, three possible sulfur reservoirs in the studied region are examined: (1) the positive sulfur values could have been derived directly from magmas or the degassing of primary magmatic sulfur. Generally, the δ34S value of mantle-derived magmatic sulfide is normally 0±3‰ (Ohmoto and Goldhaber, 1997; Hoefs, 2009), but magnetite-series granitoids have positive δ34S values (Ishihara and Sasaki, 1989; Santosh and Masuda, 1991; Fig. 9b) and isotopic values of the hydrothermal fluids derived from those oxidized magmatic systems are approximately 3‰−5‰ higher than those of the melt (Ohmoto, 1986). The δ34S values of Triassic intrusions in the Qingchengzi ore field (including the Xinling and Shuangdinggou intrusions) fall within a narrow range of 5.6‰ –7.6‰ (Ding et al., 1992),

18

which overlap with the sulfur compositions of the ore sulfides. (2) The meta-sedimentary rocks in the Qingchengzi deposit could also have acted as a sulfur source. Ding et al. (1992) reported whole rock δ34S values for marble in this region spanning a wide range of -0.5‰ − 13.2‰. The δ34S values of 12.3‰−13.2‰ of sedimentary sulfides (pyrrhotite) have been reported in the Wengquangou ludwigite deposit, which is adjacent to the Qingchengzi ore field (Hu et al., 2014). Therefore, the δ34S values of the sedimentary sulfides of Liaohe Group are inferred to be approximately 10‰, which is slightly higher than those of the ore sulfides. (3) The mixing of sedimentary rocks and magmatic rocks is also probable, with sedimentary sulfur as the high end-member and magmatic sulfur as the low end-member. The different sulfur isotopes of different mineralization styles reflect variable mixing proportions of these two end-members: the low δ34S values of the open-space-filling mineralization indicate that more magmatic sulfur has been incorporated, whereas the elevated δ34S values of the strata-bound mineralization imply that more proportions of the sedimentary source have been introduced.

6.3. Possible sources of lead Sulfide minerals have U and Th concentrations that are too low to influence Pb isotopic compositions, whereas the whole-rock compositions of igneous and sedimentary rocks need to be adjusted and the mineralization age of 225 Ma needs to be used to correct the Pb isotopic compositions of the country rocks. The country rocks (i.e., the marble of the Dashiqiao Formation and the schist of the Gaixian Formation) record more radiogenic and isotopically variable Pb values; they also plot above the upper crust model Pb curve (Fig. 10), thus suggesting that they have an upper crustal source. Triassic intrusions (including the Shuangdinggou monzogranite, lamprophyre and diorite) reveal relatively restricted Pb isotopic values, which cluster between the orogenic and mantle curves. The depleted Pb isotopic values imply that in addition to an orogenic origin, a mantle source is also involved and/or that magma mixing may have occurred. The Paleoproterozoic and Jurassic intrusions both yield low 206Pb/204Pb and 208Pb/204Pb ratios, which indicates that they have an upper crustal origin. The lead isotopic data for the Pb−Zn ores are relatively concentrated (206Pb/204Pb=17.511−17.883, 207

Pb/204Pb=15.549−15.64 and 208Pb/204Pb =37.67−38.178) for different mineralization styles; the

open-space-filling mineralization records slightly depleted lead isotopic compositions (Fig. 10c, d). They mainly plot between the orogenic and upper crustal evolution curves (Fig. 10c, d). When compared to host rocks, ore sulfides record a narrow range of lead isotope values that are significantly

19

lighter than those of meta-sedimentary rocks. Compared to magmatic rocks, ore sulfides record relatively heavier lead isotopic values than the Paleoproterozoic and Jurassic intrusions, whereas they are close to and partly overlap those of the Triassic intrusions (Fig. 10a, b), thus indicating that the Triassic magmatic rocks might have contributed metals for mineralization. The linear correlation of the lead isotopes of the ore with those of the host meta-sedimentary rocks and magmatic rocks indicate they may have originated from mixed sources, including the schist-represented upper crustal source and the Triassic magma-represented mantle source (Fig. 10a, b). In addition, the relatively lower Pb isotopic compositions of open-space-filling mineralization compared to strata-bound mineralization suggest that more proportions of a magmatic source were involved in the former and that increased amounts of sedimentary material were involved in the latter; this conclusion is consistent with the sulfur isotopic signatures.

6.4. Genetic type of the Pb−Zn mineralization The Qingchengzi ore field, along with other Pb-Zn deposits in the Liaoji Rift, is often classified as SEDEX deposits related to Paleoproterozoic rifting (Song, 2010; Wang et al., 2014; Ma et al., 2016). However, integrated studies of C−O−S−Pb isotopic and carbonate trace element analyses argue against a typical SEDEX origin of the Qingchengzi Pb-Zn deposits for several reasons: 1. Different mineralization styles: typical SEDEX deposits are dominantly stratiform and comprise finely laminated sulfide minerals; orebodies consist of sheets or tabular lenses that are parallel to bedding (Large et al., 2005; Leach et al., 2005, 2010). In contrast, the Pb−Zn orebodies in Qingchengzi are dominantly irregular veins that crosscut meta-sedimentary rocks as well as strata-bound mantos/sheets. The remnants of country rocks are commonly enveloped by orebodies. The mineralization patterns in the Qingchengzi ore district demonstrate post-sedimentary open-space-filling/metasomatic characteristics, rather than characteristics of the syn-sedimentary/syn-diagenetic replacement of SEDEX mineralization. There is only fine-grained proto-ore formation in the primary sedimentary-metamorphic period, among which metamorphic modification is notable for the recrystallization and reactivation of primary ore-forming materials. 2. Trace element and isotope geochemistry: syn-ore carbonates are significantly different than barren meta-sedimentary carbonates in terms of both their trace element compositions (i.e., enriched REE contents, pronounced positive Eu anomalies and lower Y/Ho ratios) and isotopic compositions,

20

which preclude a syn-sedimentary or metamorphic origin. Water-rock interaction plays the dominant role in the carbon-oxygen isotopic deviation between syn-ore carbonates and barren meta-sedimentary rocks. The linear correlation of ore lead isotopes between schist and Triassic intrusions indicates

that lead may result from the mixture of a magmatic and sedimentary end-member. Based on the above, we propose that although a preliminary enrichment occurred during sedimentary-metamorphic processes in the Paleoproterozoic, the dominant event responsible for the majority of Pb−Zn deposits is hydrothermal mineralization in the Mesozoic. C and O isotopic characteristics indicate that in addition to magmatic fluid, non-magmatic components (i.e., meteoric or formation water) were also involved in ore-forming fluids and that the sulfur and lead isotopic compositions reflect the contributions of meta-sedimentary rocks to ore-forming materials mixed with a magmatic component. These features imply that the Pb−Zn mineralization in Qingchengzi represents the distal part of a magmatic hydrothermal system and can be assigned to the carbonate replacement Pb−Zn type. The Pb−Zn mineralization age is confined within the range of 224–227 Ma (unpublished data), which is consistent with the results of sphalerite Rb−Sr dating (221–225 Ma) from Yu et al. (2009). Geochronological results show that the Pb−Zn mineralization event is coeval with Late Triassic magmatism. Post-collisional extension following the subduction and collision of the Yangtze Block and the NCC induced the Late Triassic magmatic activity (Duan et al., 2014). This magmatic event led to massive magmatic intrusions with the emplacement of the Shuangdinggou and Xinling granitic intrusions and lamprophyre and diorite dykes. Geophysical analysis reveals that there are concealed granitoids seated beneath the Shuangdinggou intrusion, which covers the base of the entire Qingchengzi area (Chai, 2016). Thermal activity and hydrothermal fluids accompanied by this large-scale magmatism were the major drivers of mineralization. Hydrothermal fluids migrated upward and outward along fractures and interlayers of permeable strata, mixing with meteoric water, remobilizing the metal and collecting some ore-forming material (sulfur and metal) through fluid-rock interactions. The fluid was eventually released into favorable spaces for ore deposition (Fig. 13). The three mineralization styles record diverse geological and geochemical characteristics (in terms of their C-O-S-Pb isotopic compositions) that can be attributed to different ore-controlling structures and their proximity to the mineralizing source: when proximal hydrothermal fluids encounter major faults or structure zones where extension created open spaces, such that open-space-filling can occur, forming veins or breccia orebodies. Because open spaces are especially favorable for fluid mixing, 21

fluid-rock interaction is more prominent, as is shown by the large variations and depletions of the carbon and oxygen isotopic values of the syn-ore carbonates. In addition, the low δ34S values and slightly depleted Pb isotopes of ore sulfides indicate that more magmatic components are incorporated into ore-forming materials during open-space-filling. On the other hand, when fluids are deposited along interlayer fractures or secondary faults in distal regions, strata-bound mineralization will occur, producing concordant mantos/sheets that are often closely confined to stratigraphic intervals. In this case, fluid-rock interactions are limited, as is shown by their narrow range of C-O isotopic compositions. The elevated S and Pb isotopes of ore sulfides suggest that ore-forming materials contain less of the magmatic component and more of the sedimentary component in the distal part. In addition, when ore fluids are confined both by major faults and along interlayer fractures, transitional type mineralization will form, thus displaying less of a dependence upon strata.

7. Conclusions 1. Three distinctive mineralization styles are recognized: the strata-bound mineralization is controlled by interlayer fractures, whereas open-space-filling mineralization is controlled by main faults. In addition, the transitional type mineralization is controlled by a combination of the main

fault and secondary interlayer fractures. 2. Syn-ore carbonates are significantly different than barren meta-sedimentary carbonates in terms of both their trace element compositions (i.e., enriched REE contents, pronounced positive Eu anomalies and lower Y/Ho ratios) and C-O isotopic compositions (i.e., depleted C and O isotopic compositions), which indicates that the hydrothermal fluid is likely magmatic in origin and has mixed with low δ18O fluids, such as meteoric water or formation water. 34

3. Observed δ S values gradually increase from open-space-filling to transitional type to strata-bound mineralization styles, which reflects the different mixing proportions of the two end-members of magmatic sulfur and sedimentary sulfur. The linear correlation of ore lead isotopes

between schist and Triassic intrusions indicate that lead may originate from the mixture of magmatic and sedimentary end-members. 4. The different C−O−S−Pb isotopic signatures of the three mineralization styles reflect their different degrees of stratigraphic control with respect to their diverse ore-controlling structures and 22

their proximity to the mineralizing source: open-space-filling mineralization shows the least stratigraphic control, with more pronounced “magmatic marks” (i.e., lower sulfur and lead isotopic values and more depleted C−O values), compared to strata-bound mineralization.

Acknowledgement: This research is sponsored by National Natural Science Foundation of China [No 41390443 and 41602068] and National Key Research and Development Project [No2016YFC0600108]. We are grateful to the geologist Yonggui Li and others in Qingchengzi Mining Co. Ltd. They offer great support for our field work. Dr. Xiaochun Li provided precious advises to improve this paper and the authors pay their gratitude to him. Comments and suggestions from Prof. Franco Pirajno and anonymous reviewers greatly improved the quality of the paper.

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Figure captions: Fig. 1. (a) Geological sketch map of the North China Craton (NCC), illustrating tectonic location of the Jiao−Liao−Ji Belt, which is located in between the Longgang Block and the Nangrim Block. Revised from Zhao et al. (2005) and Li et al. (2011); (b) sketch map of the Liaoji rift zone and locations of major Pb-Zn deposits and Au-Ag deposits, modified after Wang and Qu (2000).

Fig. 2. Geological map of the Qingchengzi ore field. Dash-lined boxes indicate the location of Fig. 3.

34

Fig. 3. (a) The No. 213 exploration section map illustrating transitional type mineralization (irregular shaped orebody) in the Nanshan deposit, which is hosted in interbedded marble and hornfel or interfaces between banded marble and mica schist; (b) two exploration section maps (No. 33 and No. 9) in the Zhenzigou deposit show both vein and strata−bound orebodies that are mainly hosted in interfaces of marble and mica schist.

Fig. 4. Photographs of different mineralization styles in Qingchengzi ore field. (a)-(b) represent strata-bound mineralization, (c)-(g) are open-space-filling mineralization and (h) represents transitional type mineralization. (a) Extended tabular Pb−Zn orebody with width of 1−1.5 m and length of over 80 m, from the 270 m mining level of the Erdao deposit; (b) extended lenticular Pb orebody cuts through carbonate veins that crosscut banded marble, from the 270 m mining level of the Xiquegou deposit; (c) sacciform Pb−Zn orebody crosscuts marble at the 330 m mining level of the Diannan deposit; (d) stock veins hosted in marble at the 300 m mining level of the Xiquegou deposit; (e) breccia Pb orebodies occur in fractured zone, where fragments of marble are cemented by a sulfide matrix of pyrite and galena, from the 420 m mining level of the Zhenzigou deposit; (f) vein stock Pb orebodies hosted in dolomitic marble at the 420 m mining level of the Zhenzigou deposit; (g) ore veins (galena+quartz) developed in sericitized granite porphyry, from the 360 m mining level of the Diannan deposit; (h) transitional type Pb−Zn orebody hosted in banded marble, from the 180 m mining level of the Xiquegou deposit.

Fig. 5. Photographs of ore hand specimens. (a) sample of banded ore (sphalerite+pyrite+dolomite), Zhenzigou deposit; (b) sample of massive ore (pyrite+galena), Nanshan deposit; (c) sample of veinlet ore (sphalerite+galena+dolomite), Zhenzigou deposit; (d) sample of semi-banded ore (pyrite+galena+dolomite+quartz), Zhenzigou deposit.

Fig. 6. Paragenetic sequences of minerals in Qingchengzi Pb−Zn deposits, in which the widths of the lines represent the relative abundances of the minerals.

Fig. 7. Photomicrographs demonstrating mineral paragenesis of two metallogenic periods of the Qingchengzi Pb−Zn deposit: (a) early sedimentary period: fine-grained rounded Py1 and fine-grained 35

disseminated Sp1, partly recrystallized to granular Sp2, which normally coexists with Chl or Cb, reflected light (plane-polarized); (b) granular Gr intergrown with fine−grained Sp1 and Ccp, reflected light (plane-polarized); (c) Gn in hydrothermal mineralization period replaces Py and Gr, reflected light (plane-polarized); (d) Sp−Gn−Ccp vein cuts through Gr alignment in host rocks, reflected light (plane-polarized); (e) second hydrothermal period: stage I euhedral Py grain is replaced by Cb and Sp and exhibits skeletal texture, transmitted light (plane-polarized); (f) stage II Gn fills fractures in Py, reflected light (plane-polarized); (g) stage II Gn partially replaces Py and Sp, leaving embayed remnants of Sp and Py inside Gn, reflected light (plane-polarized); (h) stage III carbonate veins cut through Sp, transmitted light (plane-polarized). Abbreviations: Sp: sphalerite; Gn: galena; Py: pyrite; Cb: carbonate mineral; Qtz: quartz; Gr: graphite; Ccp: chalcopyrite; Chl: chlorite.

Fig. 8. Diagram of δ13CPDB vs. δ18OSMOW for the carbonates of the Pb−Zn ores (group I and group II), as well as barren dolomitic marble and related sources. Data sources: data for the dolomite of the Guanmenshan Formation, the marble of the Dashiqiao Formation and the 2.33−2.06 Ga marine carbonates are from Tang et al. (2011, 2013).

Fig. 9. (a) Histogram of sulfur isotopic compositions of sulfides from Pb−Zn deposits in Qingchengzi ore field; (b) comparison of δ34S values between different mineralization styles and marble and Triassic intrusions (Xinling and Shuangdinggou intrusions). Data source: ranges of δ34S values of marble and Triassic intrusions are from Ding et al. (1992) and Wang et al. (2008).

Fig. 10. Lead isotope plot of ore sulfides and related rocks in the Qingchengzi ore field: (a) 207Pb/204Pb – 206Pb/204Pb diagram and (b) 208Pb/204Pb – 206Pb/204Pb diagram illustrating the relationship between ore sulfides, magmatic rocks and meta-sedimentary rocks; (c) partial 207Pb/204Pb –206Pb/204Pb diagram and (d) 208Pb/204Pb – 206 Pb/204Pb diagram highlighting lead isotopic values of different mineralization styles and their associations with Triassic intrusions. Initial lead isotopic compositions of magmatic rocks are calculated and those of schist and marble samples have been corrected assuming a mineralization age of 225 Ma. The lead evolution curves are from Zartman and Doe (1981). Abbreviations: UC: upper crust, O: orogeny, M: mantle, LC: lower crust.

36

Fig. 11. PAAS-normalized REE patterns of syn-ore dolomite (A, B, C are from samples zz390−5, 330−1 and BS−8, respectively) and barren meta-sedimentary dolomite (D is from sample zza330−1). PAAS data are from McLennan (1989).

Fig. 12. General trends of δ13C and δ18O halos of various types of carbonate-hosted deposits (after Large et al., 2001); HYC and Lady Loretta represent typical SEDEX deposits in North Australia. Note: For open-space-filling mineralization samples, two data points with low δ18O values plot outside the diagram, and only one data point is presented.

Fig. 13. Genetic model and tectonic setting of the Triassic magmatism and metallogenesis of the Qingchengzi ore field: (a) Geodynamics of Late Triassic magmatism. Post-collisional extension following the subduction and collision of the Yangtze Block and the NCC induced Late Triassic magmatic activity (Duan et al., 2014); (b) Genetic model for various styles of Pb−Zn mineralization. The Late Triassic magmatic activity had a significant thermal impact and induced a tremendous volume of hydrothermal fluid, which migrated upward and outward along fractures and interlayers of permeable strata, where they picked up ore-forming material. The fluid was then released into the appropriate sites of ore formation: open-space-filling mineralization occurred when it was deposited in the major fault, transitional type formed when fluid migrated further into the major fault along the interlayer fractures, and strata-bound mineralization formed when deposition occurred along the interlayer fractures in distal regions. Abbreviations: NCC: North China Craton; SCLM: subcontinental mantle lithosphere.

Table captions: Table 1 Summary of different mineralization styles of Pb−Zn deposits in the Qingchengzi ore field Table 2 Carbon and oxygen isotopic compositions of carbonates from Pb−Zn deposits in the Qingchengzi ore field Table 3 Sulfur isotopic compositions of sulfides from Pb−Zn deposits in the Qingchengzi ore field Table 4 Lead isotopic compositions of sulfides from Pb−Zn deposits in the Qingchengzi ore field Table 5 Lead isotopic compositions of meta-sedimentary rocks and igneous rocks in the Qingchengzi 37

ore field Table 6 LA−ICPMS data of syn-ore carbonates and barren meta-sedimentary carbonates in the Qingchengzi ore field

38

39

40

41

42

43

44

45

46

47

48

49

50

51

Table 1 Summary of different mineralization styles of Pb−Zn deposits in the Qingchengzi ore field Mineralization style

strata-bound mineralization

ore body morphology

open-space filling mineralization

transitional ty

strata hosted

intrusion hosted

sheet, tabular,lenticular, podiform, nodular ore bodies

veins, veinlet as well as sacciform and brecciaous ore bodies

veins

irregular oreb

ore structure

massive, semimassive, banded or disseminated

massive, brecciaous

massive and semimassive

massive and s

controlling structure

interlayer fractures/scondary fractures

main faults which crosscut strata

fractures

main faults+i

wall rock alteration

silificiation, carbonatization,sericitization

silification, carbonatization,sericitization

Strong sericitization and silicification

silificiation, carbonatizatio

Zn/Pb ratios

>1

<1

<1

<1

representive orebody

Zhenzigou no.2 and no.289 ore body , controlled by interlayer fracture zones and hosted in graphite-bearing marble and mica schist at the bottom of Dashiqiao Formation

Xiquegou no.6404 and no.426 ore body controlled by parallel No.1 and No. 122 fault and hosted in banded marble with interlayer of hornfel in Dashiqiao Formation

Diannan veinlet ore body, hosted in alterted granite porphyry

Nanshan ore by parallel fa strike NE) an banded marbl Formation

52

Table 2 Carbon and Oxygen isotopic compositions of carbonates from Pb−Zn deposits in the Qingchengzi ore field

Sample no.

Analyzed mineral

δ13 CPDB (‰)

δ18OPDB (‰)

δ18OSMOW (‰)

δ18Ofluid (‰)

390-10-1

dolomite

-5.04

-17.17

13.16

2.81

ZZ390-1

dolomite

-4.92

-17.55

12.77

2.42

ZZ390-5

dolomite

-4.96

-17.44

12.88

2.53

banded Sp-Gn ore

strata-bound

ZZ390-14

dolomite

-5.11

-18.04

12.26

1.91

banded Sp-Gn ore

strata-bound

ZZ390-15

dolomite

-4.71

-18.12

12.18

1.83

banded Sp-Gn ore

strata-bound

390-1-1

dolomite

-3.65

-26.75

3.29

-7.06

massive Gn ore

390-1-3

calcite

-1.06

-23.24

6.90

-2.87

massive Gn ore

390-2

calcite

-1.33

-26.14

3.92

-5.85

massive Gn ore

DN-11

calcite

-2.37

-19.39

10.88

1.10

massive Gn-Py ore transitional type

ZZA150-3

dolomite

-0.69

-9.02

21.56

ZZA150-7

dolomite

-1.07

-9.71

20.85

barren ZZA330-5 carbonate

dolomite

-0.55

-7.86

22.76

ZZA330-8

dolomite

-1.27

-10.84

19.69

XQA360-3

dolomite

-1.98

-9.33

21.25

group I

Occurrence

disseminated Sp-Py ore disseminated Sp ore

group II

Mineralization style strata-bound strata-bound

open-space filling open-space filling open-space filling

D33 dolomitic marble D35 dolomitic marble D1 dolomitic marble D31dolomitic marble D31 dolomitic marble

δ18Ofluid is calculated from fractionation equations of 103lnαcc−fluid = 4.01×106/T2 − 4.66×103/T +1.71 and 103lnαdol−fluid = 4.12×106 +1.71 (Zheng,1999), where temperature is assumed at 200℃ (Duan, 2015)

53

Table 3 Sulfur isotopic compositions of sulfides from Pb−Zn deposits in the Qingchengzi ore field

Sample no.

Analyzed mineral

Occurrence

δ34SCDT ‰

Mineralization style

Sample location

ZZ390-16

Sp

banded Sp ore

8.0

strata-bound

Zhenzigou deposit

ZZ390-1

Sp

disseminated Sp ore

8.2

strata-bound

Zhenzigou deposit

ZZ390-8-2

Sp

massive Sp-Gn ore

8.2

strata-bound

Zhenzigou deposit

390-4-2

Sp

massive Sp-Py ore

7.3

strata-bound

Zhenzigou deposit

390-6-1

Sp

massive Sp-Gn ore

8.0

strata-bound

Zhenzigou deposit

390-10-1

Sp

disseminated Sp-Py ore

7.8

strata-bound

Zhenzigou deposit

390-10-5

Sp

massive Sp-Py ore

7.9

strata-bound

Zhenzigou deposit

ZZW-1

Sp

disseminated Sp ore

7.3

strata-bound

Zhenzigou deposit

DN-1-2

Sp

6.9

transitional type

Diannan deposit

DN-6

Sp

6.3

strata-bound

Diannan deposit

DN150-5

Sp

massive Sp-Py ore

5.7

open-space filling

Diannan deposit

DN150-4

Sp

massive Sp-Py ore

5.6

open-space filling

Diannan deposit

DNBY

Sp

Sp-Gn ore

6.3

open-space filling

Diannan deposit

ZZ390-12

Gn

banded Sp-Gn ore

5.4

strata-bound

Zhenzigou deposit

ZZ390-15

Gn

banded Sp-Gn ore

5.2

strata-bound

Zhenzigou deposit

330-6

Gn

massive Gn-Py ore

3.9

open-space filling

Zhenzigou deposit

390-6-1

Gn

massive Sp-Gn ore

5.6

strata-bound

Zhenzigou deposit

330-5-1

Gn

massive Gn-Py ore

3.5

open-space filling

Zhenzigou deposit

390-7

Gn

massive Gn-Py ore

4.8

strata-bound

Zhenzigou deposit

NS-1-2

Gn

massive Gn-Py ore

5.8

transitional type

Nanshan deposit

NS-60-1

Gn

massive Gn-Py ore

5.2

transitional type

Nanshan deposit

NS-60-6

Gn

massive Gn-Py ore

5.4

transitional type

Nanshan deposit

NS-10

Gn

massive Gn-Py ore

6.4

transitional type

Nanshan deposit

XQ180-2

Gn

massive Py-Gn ore

3.2

open-space filling

Xiquegou deposit

XQ360-1

Gn

massive Gn-Py ore

3.9

open-space filling

Xiquegou deposit

XQA360-7

Gn

massive Py-Gn ore

3.9

open-space filling

Xiquegou deposit

XQ360-3

Gn

massive Py-Gn ore

3.4

open-space filling

Xiquegou deposit

DN-1-1

Gn

massive Gn-Py ore

4.3

transitional type

Diannan deposit

massive Py-Gn-Sp Ore massive Py-Gn-Sp Ore

54

DN-13-2

Gn

massive Gn-Py ore

6.4

transitional type

Diannan deposit

DN360-2

Gn

Gn ore in granite

4.6

open-space filling

Diannan deposit

DN360-3

Gn

Gn ore in granite

4.7

open-space filling

Diannan deposit

DN360-4

Gn

Gn ore in granite

3.7

open-space filling

Diannan deposit

BS-1

Gn

massive Gn ore

4.6

open-space filling

Benshan deposit

BS-4

Gn

massive Gn ore

4.7

open-space filling

Benshan deposit

BS-4

Gn

massive Gn ore

4.7

open-space filling

Benshan deposit

330-12

Py

massive Sp-Py ore

6.7

strata-bound

Zhenzigou deposit

ZZ390-8-1

Py

massive Py ore

9.1

strata-bound

Zhenzigou deposit

XQ180-2

Py

massive Py-Gn ore

6.0

open-space filling

Xiquegou deposit

XQA360-1

Py

massive Py ore

5.2

open-space filling

Xiquegou deposit

XQA180-1

Py

massive Py ore

6.1

open-space filling

Xiquegou deposit

DN-6

Py

massive Py-Gn-Sp Ore

6.4

strata-bound

Diannan deposit

DNBY

Py

Sp-Gn ore

7.2

open-space filling

Diannan deposit

NS-11

Py

massive Py ore

7.9

transitional type

Nanshan deposit

NS-10

Py

massive Gn-Py ore

7.9

transitional type

Nanshan deposit

NS-1-3

Py

massive Gn-Py ore

7.6

transitional type

Nanshan deposit

marble

9.4

marble

13.2

marble

11.4

marble

9.1

marble

−0.5

marble

0.4

Xinling granite

6.3

Triassic intrusion

Xinling granite

5.6

Triassic intrusion

7.0

Triassic intrusion

7.6

Triassic intrusion

*QZ-2 *QZ-10 *QZ-25 *QD-1 *QZ-24 *QD-161 *XDB-1 *XDB-2 *SDB-2 *SDB-5

whole rock whole rock whole rock whole rock whole rock whole rock whole rock whole rock whole rock whole rock

Shuangdinggou granite Shuangdinggou granite

* marked data are cited from Ding et al.(1992), other data are from this study.

55

Dashiqiao Formation Dashiqiao Formation Dashiqiao Formation Dashiqiao Formation Dashiqiao Formation Dashiqiao Formation

Table 4 Lead isotopic compositions of sulfides from Pb−Zn deposits in the Qingchengzi ore field

Pb/204Pb 2σ

207

Pb/204Pb 2σ

208

Pb/204Pb 2σ

Min style

Sample no. Mineral

Occurrence

206

ZZ390-12

Sp

banded Sp-Gn ore

17.833

0.002

15.578

0.002

38.005

0.005

strat

ZZ390-16

Sp

banded Sp ore

17.799

0.001

15.569

0.001

37.982

0.003

strat

ZZ390-1

Sp

disseminated Sp ore

17.872

0.002

15.593

0.002

38.044

0.004

strat

ZZ390-11

Sp

banded Sp ore

17.849

0.002

15.598

0.002

38.066

0.004

strat

ZZ390-8-2

Sp

massive Sp-Gn ore

17.847

0.002

15.581

0.001

38.011

0.003

strat

ZZW-1

Sp

disseminated Sp ore

17.847

0.001

15.591

0.001

38.054

0.003

strat

390-10-5

Sp

massive Sp-Py ore

17.883

0.001

15.571

0.001

38.025

0.002

strat

390-10-1

Sp

17.825

0.002

15.58

0.002

38.015

0.006

strat

DN-1-2

Sp

17.865

0.002

15.593

0.002

38.003

0.004

trans

DN-6

Sp

DN150-5

17.749

0.002

15.573

0.001

38.017

0.003

strat

Sp

disseminated Sp-Py ore massive Py-Gn-Sp ore massive Py-Gn-Sp ore massive Sp-Py ore

17.666

0.001

15.557

0.001

37.941

0.003

open

DNBY

Sp

veinlet Sp-Gn ore

17.795

0.002

15.6

0.002

37.766

0.004

open

ZZ390-12

Gn

banded Sp-Gn ore

17.853

0.002

15.588

0.002

38.03

0.004

strat

ZZ390-15

Gn

banded Sp-Gn ore

17.861

0.002

15.583

0.002

38.019

0.004

strat

DN-13-2

Gn

massive Gn-Py ore

17.773

0.001

15.578

0.001

38.004

0.004

trans

DN1-1

Gn

17.775

0.002

15.608

0.002

38.121

0.005

trans

DN360-3

Gn

17.829

0.001

15.607

0.001

37.791

0.003

open

DN360-4

Gn

massive Gn-Py ore veinlet Gn ore in granite veinlet Gn ore in granite

17.651

0.002

15.568

0.001

37.684

0.003

open

NS-1-2

Gn

massive Gn-Py ore

17.662

0.002

15.558

0.002

37.993

0.005

trans

NS60-6

Gn

massive Gn-Py ore

17.737

0.001

15.574

0.001

38.026

0.003

trans

330-5-1

Gn

massive Gn-Py ore

17.789

0.002

15.566

0.002

38.03

0.004

open

330-6

Gn

massive Gn-Py ore

17.775

0.002

15.574

0.001

38.085

0.003

open

390-7

Gn

massive Gn-Py ore

17.728

0.002

15.564

0.002

38.063

0.004

open

XQ180-2

Gn

massive Py-Gn ore

17.511

0.002

15.549

0.002

37.67

0.004

open

XQA360-7

Gn

massive Py-Gn ore

17.559

0.002

15.563

0.001

37.731

0.004

open

XQ360-3

Gn

massive Py-Gn ore

17.88

0.002

15.589

0.002

38.083

0.004

open

56

330-12

Py

massive Sp-Py ore

17.781

0.001

15.591

0.001

38.14

0.003

strat

XQA360-1

Py

massive Py ore

17.8

0.001

15.575

0.001

38.046

0.003

open

DN-6

Py

DN13-2

17.759

0.001

15.589

0.001

38.073

0.002

strat

Py

massive Py-Gn-Sp ore massive Gn-Py ore

17.781

0.004

15.596

0.003

38.063

0.008

trans

DNBY

Py

veinlet Sp-Gn ore

17.798

0.004

15.617

0.003

37.827

0.008

open

NS-1-3

Py

massive Gn-Py ore

17.755

0.002

15.574

0.002

37.98

0.006

trans

NS-11

Py

massive Py ore

17.751

0.004

15.64

0.003

38.178

0.008

trans

57

Table 5 Lead isotopic compositions of meta-sedimentary rocks and igneous rocks in the Qingchengzi ore field

Sample no.

206

Pb/204Pb



207

Pb/204Pb



208

Pb/204Pb



Pb /ppm

Th /ppm

U /ppm

t(Ma)

(206Pb /204Pb)t

(207Pb /204Pb

metasedimentary rocks of Qingchenzi orefield(corrected for 225 Ma radiogenic Pb) Marble of Dashiqiao Formation ZZA150-3

39.905

0.005

18.072

0.002

37.075

0.004

9.08

0.19

4.18

225

38.346

17.99

ZZA150-6

22.314

0.004

16.065

0.003

37.490

0.007

18.30

0.47

6.88

225

21.295

16.01

ZZA150-7

24.894

0.003

16.327

0.002

37.222

0.004

11.20

0.13

6.37

225

23.301

16.24

ZZA330-1

17.900

0.002

15.562

0.001

38.049

0.003

773.00

5.74

1.67

225

17.895

15.56

ZZA330-5

31.359

0.008

17.206

0.004

37.993

0.009

8.76

1.05

5.50

225

29.421

17.10

ZZA330-8

31.134

0.004

17.012

0.002

37.318

0.004

2.00

0.06

2.23

225

27.735

16.84

XQA360-2

25.418

0.005

16.4

0.003

37.785

0.008

6.69

0.43

4.05

225

23.697

16.31

XQA180-3

19.463

0.004

15.762

0.003

38.504

0.007

4.23

1.14

0.51

225

19.146

15.74

XQA180-2

19.476

0.004

15.751

0.003

38.374

0.007

6.93

1.42

0.60

225

19.247

15.73

#291g

19.489

0.005

15.806

0.004

37.430

0.012

2.09

0.23

0.13

225

19.327

15.79

#291y

22.150

0.004

16.086

0.004

38.367

0.009

2.24

0.64

0.29

225

21.796

16.06

#292g

23.724

0.004

16.281

0.002

37.928

0.006

3.85

0.77

1.16

225

22.885

16.23

#292y

22.635

0.004

16.193

0.004

38.107

0.011

3.08

0.98

1.55

225

21.252

16.12

#296

18.589

0.006

15.709

0.003

38.627

0.007

4.09

0.14

0.70

225

18.143

15.68

*666a

25.147

0.006

16.485

0.003

37.352

0.008

1.27

0.10

0.74

225

23.504

16.40

*666b

22.800

0.008

16.213

0.005

37.678

0.013

1.08

0.08

0.92

225

20.466

16.09

Schist of Gaixian Formation ZZA330-2

19.508

0.002

15.738

0.002

39.126

0.004

12.00

2.49

0.57

225

19.382

15.73

ZZA330-6

18.654

0.002

15.602

0.002

39.273

0.005

11.40

4.33

0.81

225

18.468

15.59

ZZA330-10

18.192

0.002

15.630

0.002

39.192

0.006

36.90

20.20

3.26

225

17.961

15.61

ZK432-4-1

22.297

0.001

16.105

0.001

42.009

0.003

17.90

16.00

4.93

225

21.506

16.06

*663

20.641

0.003

16.003

0.003

39.630

0.007

11.20

13.66

4.44

225

19.561

15.94

*689

18.604

0.002

15.672

0.002

39.945

0.005

16.43

10.79

2.02

225

18.278

15.65

*690

19.775

0.003

15.823

0.002

40.549

0.005

8.71

10.04

1.92

225

19.175

15.79

Magmatic rocks of Qingchengzi orefield DB-37

16.194

0.001

15.459

0.001

35.898

0.003

18.90

0.73

0.36

165

16.160

15.45

DB-40

15.855

0.002

15.460

0.002

35.646

0.004

17.10

0.59

0.19

165

15.836

15.45

DB-41

16.268

0.001

15.496

0.001

35.796

0.003

12.20

0.09

0.29

165

16.226

15.49

58

Db-19

17.711

0.001

15.466

0.001

38.576

0.003

29.10

30.10

3.10

224

17.439

15.45

DB-20

18.333

0.002

15.506

0.001

39.408

0.003

21.40

45.90

3.84

224

17.865

15.48

DB-25

18.385

0.002

15.506

0.001

39.177

0.003

20.10

39.40

4.24

224

17.837

15.47

DN150-1

17.908

0.002

15.481

0.002

38.888

0.005

31.50

30.10

4.17

220

17.574

15.46

DN300-1

17.904

0.001

15.508

0.001

38.288

0.003

15.20

4.39

0.86

220

17.763

15.50

DN300-2

17.954

0.002

15.518

0.002

38.366

0.005

11.60

4.14

0.82

220

17.778

15.50

DB-27

16.017

0.002

15.514

0.001

35.624

0.003

25.00

0.89

0.38

2217

15.596

15.45

Db-33

16.482

0.002

15.537

0.002

36.021

0.004

32.30

1.04

0.67

2217

15.899

15.45

data for samples marked with # are refered from Chen et al.(2005) and * labeled data are cited from Yu et al.(2009)

59

Table 6 LA−ICPMS data of ore carbonates and barren meta-sedimentary carbonates in the Qingchengzi ore field

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y Y/Ho REE (Nd/Yb)N Eu/Eu*

ore carbonates BS-8 BS-8 1 2 5.85 5.57 18.46 12.71 2.74 1.23 11.86 4.93 2.71 0.86 0.69 0.29 2.47 1.01 0.52 0.11 2.02 0.82 0.38 0.14 0.97 0.42 0.12 0.11 0.61 0.40 0.11 0.07 10.13 4.48 27 32 49.51 28.65 1.62 1.02 1.27 1.50

BS-8 3 4.69 9.52 1.00 4.18 0.82 0.25 0.76 0.16 0.62 0.18 0.24 0.07 0.28 0.06 3.74 21 22.82 1.24 1.49

BS-8 4 15.17 34.87 4.00 15.75 3.56 1.26 3.5 0.44 3.33 0.59 1.6 0.18 1.3 0.18 18 31 85.73 1.01 1.72

BS-8 5 4.48 10.11 1.00 3.3 0.75 0.29 0.72 0.14 1.05 0.11 0.43 0.07 0.43 0.08 4.22 39 22.94 0.64 1.86

ZZ390-5 1 3.1 21.46 11.39 52.67 1.52 7.09 7.45 29.37 1.76 7.43 0.69 3.01 1.57 6.5 0.24 1.38 1.36 7.07 0.246 1.43 0.71 4.04 <0.078 0.70 0.58 4.08 0.08 0.67 7.18 58.52 29 41 30.69 146.90 1.07 0.60 1.97 2.05 BS-8 6

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y Y/Ho REE (Nd/Yb)N Eu/Eu*

330-1 2 27.56 44.07 5.31 18.3 3.92 2.26 4.98 0.72 5.50 1.45 3.92 0.67 4.93 0.45 52.88 36 124.04 0.31 2.53

ZZ390-5 3 ZZ390-5 4 ZZ390 25.24 56.05 7.93 31.18 7.78 3.02 8.98 1.37 9.03 1.92 4.9 0.60 4.09 0.77 62.5 33 162.86 0.63 1.78

23.77 56.13 6.51 26.68 5.36 3.99 5.23 0.62 3.91 0.74 1.49 0.16 1.02 0.16 27.15 37 135.76 2.18 3.63

22.48 56.02 7.40 30.31 6.01 3.07 7.48 1.18 7.99 1.83 5.05 0.58 4.25 0.53 57.88 32 154.18 0.59 2.26

barren sedimentary carbonates

ore carbonates 330-1 1 15.39 28.93 3.58 12.33 2.93 1.90 3.05 0.44 4.34 0.93 3.11 0.42 3.51 0.49 32.35 35 81.36 0.29 3.09

ZZ390-5 2 25.03 59.11 7.62 31.82 6.36 2.75 6.29 0.87 6.76 1.25 3.87 0.33 2.38 0.31 45.65 37 154.75 1.11 2.10

330-1 3 7.26 13.98 1.61 7.00 2.5 0.64 2.13 0.25 2.47 0.54 1.92 0.24 2.49 0.41 23.44 43 43.44 0.23 1.31

330-1 4 14.61 29.84 3.49 14.55 3.08 1.61 2.35 0.45 3.35 0.72 2.15 0.30 1.69 0.16 27.45 38 78.35 0.72 2.77

330-1 5 27.6 53.38 5.93 23.85 5.79 1.99 5.96 0.74 4.83 0.89 2.6 0.36 2.15 0.21 35.86 40 136.28 0.92 1.64 60

330-1 6 18.35 36.18 3.66 16.03 2.57 2.45 3.1 0.43 3.65 0.81 2.44 0.31 1.58 0.29 30.28 37 91.85 0.84 4.28

330-1 7 12.09 27.31 3.28 11.79 2.84 1.69 2.79 0.45 2.43 0.48 1.67 0.13 1.4 0.17 21.13 44 68.52 0.70 2.90

ZZA330-1 1 4.47 9.19 0.99 6.41 1.15 0.36 1.43 0.23 1.96 0.54 1.86 0.32 1.44 0.20 29.66 55 30.56 0.37 1.38

ZZA330-1 2 5.13 9.34 1.05 5.63 0.82 0.28 0.77 0.25 1.5 0.37 1.52 0.27 0.62 0.18 20.77 57 27.73 0.76 1.68

ZZA33 3 4.92 8.42 1.06 4.51 0.98 0.22 1.05 0.16 1.23 0.35 0.85 0.16 0.63 0.13 19.53 56 24.67 0.60 1.04

61

Highlights 1. Three distinctive mineralization styles, controlled by diverse structures, are recognized. 2. Ore carbonates show distinct REE patterns and C-O isotopes relative to barren ones. 3. Sulfide S-Pb isotopes indicate variable mixing of magmatic and sedimentary sources. 4. Arguing against SEDEX origin, a distal carbonate replacement genesis is proposed.

62