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Geosciences 2018, 8(4), 120; https://doi.org/10.3390/geosciences8040120

Article
Geology and Isotope Systematics of the Jianchaling Au Deposit, Shaanxi Province, China: Implications for Mineral Genesis
1
School of Jewellery, Guangzhou College South China University of Technology, Guangzhou 510800, China
2
Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
3
School of Marine Sciences, Sun Yat-sen University, Guangzhou 510006, China
4
Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Guangzhou 510006, China
5
Centre for Exploration Targeting, The University of Western Australia, Crawley, WA 6009, Australia
6
MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, CAGS, Beijing 100037, China
7
Institute of Deep-Sea scicence and Engineering, CAS Sanya 572000, China
8
Guangdong Institute of Marine Geological Survey, Guangzhou 510080, China
*
Authors to whom correspondence should be addressed.
Received: 9 March 2018 / Accepted: 29 March 2018 / Published: 3 April 2018

Abstract

:
The giant Jianchaling Au (52 t Au) deposit is located in the Mian-Lue-Yang Terrane in the southern part of the Qinling Orogen of central China and is hosted by metamorphosed carbonate rocks of the Late Neoproterozoic Duantouya Formation. The deposit consists of multiple generations of mineralised quartz(-carbonate) veins in WNW-trending extensional ductile-brittle shear zones. Based on the mineral assemblages and cross-cutting relationships between the quartz(-carbonate) veins, the paragenesis is characterised by an early coarse-grained pyrite-pyrrhotite-pentlandite-dolomite-quartz assemblage (I), followed by pyrite-sphalerite-galena-carbonate-arsenopyrite-fuchsite-carbonate-quartz containing gold (II), and fine-grained pyrite-dolomite-calcite-quartz-realgar (As2S2)-orpiment (As2S3) (III). The H-O-C isotope systematics for the three vein sets indicate that the mineralising fluid is probably sourced from the metamorphic dehydration of carbonate rocks in the Duantouya Formation, and gradually mixed with meteoric water during the emplacement of the third vein set. The δ34S values for sulfides (6.3–16.6‰) from the second auriferous vein set are greater than zero, indicating sulfates reduction from the Neoproterozoic metamorphic rocks (Duantouya Fm). The (206Pb/204Pb)i ratios from pyrite (17.521–18.477) from each of the vein sets overlap those of the ultramafic rocks (18.324–18.717) and the Bikou Group (17.399–18.417), indicating that the units are possible sources for the sulfides in the mineralisation. Both εNd(t) and Isr(t) of sulfide overlap with the meta-ultramafic field and Duantouya formation and dominated with mature Sr-Nd character, which indicated that the Duantouya may play an important role during the ore formation and there may exist a minor ultramafic source that is involved in the ore fluid. The S-Pb-Sr-Nd isotopic ratios are closely related to those of the Bikou Group and Duantouya Formation, which indicates that the mineralised fluid has interacted with both units. Combining the previously published data with data from this study on the mineralised area, we surmise that Jianchaling is characteristic of an orogenic-type gold deposit related to the Triassic Qinling Orogeny associated with continental collision.
Keywords:
Jianchaling Au deposit; isotope geochemistry; ore genesis; orogenic-type gold deposit; Qinling Orogen; central China

1. Introduction

The different tectonic events are accompanied by different types of mineralisation and associated hydrothermal alteration of different ages [1,2,3], including orogenic-Au deposits [4,5,6]. Many of these deposits record multiple deformation events, making then difficult to study and leading to uncertainty in their genesis [7,8,9]. Nonetheless, some of the deposits have been identified as orogenic-types, such as the Juneau Gold Belt in America [10], the Sukhoi Log gold deposit in Russia [11], the Victorian gold province in SE Australia [12], the Jiaodong gold province in China [13] and the Shanggong, Wenyu and Huachanggou Au deposits, and Tieluping, Weishancheng, Yindonggou, Wangpingxigou, Dahu and Zhifang Ag-Au-Mo deposits [14,15,16,17,18,19,20,21,22,23,24,25,26] in China of the Qinling Orogen.
Other deposits present in the Qinling Orogen include porphyry-, skarn-, breccia pipe-, hydrothermal-, Carlin-, and epizonal-types, which have been studied in detail [1,27,28,29,30,31,32,33,34,35,36,37,38]. Orogenic gold deposits recognised in the orogen include Jianchaling, Lijiagou and Huachanggou [8,25,39], of which Jianchaling is the largest (Figure 1). However, the genesis of the giant Jianchaling Au deposit is still poorly understood.
The Jianchaling Au deposit is located in the triangular area marked by Mianxian, Lueyang, and Yangpingguan towns (MLY), in the South Qinling Terrane of the Qinling Orogen (Figure 1c). The deposit has a measured resource of 52 t Au with an average grade of 5 g/t hosted by quartz-veins in a ductile-brittle shear zone [21,39,40,41,42,43]. Even though the genesis of the mineralisation at the deposit has been studied, the source of the metals and nature of the mineralising fluids have remained unclear.
This contribution summarises the geology, mineralisation, and H–O–C–S stable and Pb–Sr–Nd isotopic systematics for the giant Jianchaling deposit with the aim to clarify the source of the metals and nature of the mineralising fluid. This, in turn, provides a better understanding of the tectonic and mineralising processes in MLY.

2. Geological Setting

The Qinling Orogen is located south of the North China Block (NCB) and has experienced a complex tectonic history [44,45,46]. It is located in the central portion of the east-trending Central China Orogen, and developed during the Mesozoic collision between the North China and Yangtze blocks (Figure 1a,b) [1,47,48,49]. The Luanchuan Fault is the northern boundary of the orogen, and the southern boundary is the Longmenshan Fault. Deformation associated with the orogen extends into the Huaxiong Domain that is also included in the southern part of the Precambrian North China Block. The subdivisions of the orogen are shown in Figure 1b.
The Jianchaling deposit is a fault-controlled lode-gold deposit hosted by the Neoproterozoic Duantouya Fm in the eastern part of the MLY (Figure 1). The group unconformably underlies Late Paleozoic turbiditic successions in the Songpan-Ganzi Basin situated between the Mian-lue Suture to the north and Han Jiang Suture to the south (Figure 1c). The area is an important part of the Qinling Orogen and hosts many mineral deposits (e.g., Au, Cu, Ni, Zn, Pb, Mn) in various lithological and structural settings (Figure 1c), and is commonly known as the Golden Triangle [42].
The rock-types in the MLY area include metamorphosed Neoarchean granite-greenstones in the Yudongzi Complex, Neoproterozoic volcanic sequences in the Bikou Group, Late Neoproterozoic calcareous units in the Duantouya and Jiudaoguai formations, and Paleozoic carbonate in the Lueyang Formation (Figure 2). The Bikou Group is widespread in the area and consists of greenschist to amphibolite facies felsic and mafic volcanic protoliths. Various generations of metamorphism and ductile to brittle NE- and NW-trending faults (including thrusts and basin-forming extensional faults) have developed in the area, which control the location of felsic, mafic and ultramafic intrusive rocks and mineralisation (Figure 2).

3. Geology and Mineralization of the Jianchaling Area

Rocks outcropping in the Jianchaling area Neoarchean Yudongzi Complex, Neoproterozoic Bikou Group, Late Neoproterozoic Duantouya and Jiudaoguai formations, and Paleozoic Lueyang Group (Figure 2). The deposit can be subdivided into northern and southern zones containing five lenticular mineralisation in the WNW-trending Hejiayan and NW-trending Xiqugou faults and their splays. The richest mineralisation is the “No.1 Au orebody” that is 1950 m long, up to 23 m wide, and dips >43° N.
The Hejiayan and Xiqugou faults are brittle-ductile shear zones [50], and host mineralised lenticular quartz veins at the contact between ultramafic rocks and calcareous beds in the Late Neoproterozoic Duantouya and Jiudaoguai formations (Figure 2 and Figure 3). The quartz veins shallowly dip between 20° and 40° WSW is places in steeply dipping sections of the fault.
The mineralisation includes native gold and lesser amounts of electrum and native silver associated with pyrite and minor amounts of hematite, magnetite, limonite, chromite, marcasite, realgar, and orpiment. The gangue minerals are dolomite, calcite and quartz, with minor amounts of serpentine, fuchsite, and albite (Figure 4a–c) [39].
Yue [21,39] recognized early deformed and recrystallised quartz—pyrite—carbonate vein crosscut by the quartz—gold—fuchsite—arsenopyrite—pyrite—magnetite second generation vein set, and the third generation of dolomite—calcite—quartz—fine-grained pyrite—realgar—orpiment veins (Figure 4c). The pyrite associated with each of the vein sets are also distinct from each other. The first vein set contains pyrite that is >2 mm across, variably fractured, anhedral to subhedral in shape, and intergrown with euhedral fuchsite and serpentine (Figure 4d,e). The second pyrite generation is not deformed, subhedral, 1–2 mm across, and commonly has cores or inclusions of the first generation pyrite, chalcopyrite, and sphalerite (Figure 4f,g). This pyrite is also commonly altered to hematite with martite pseudomorphing magnetite (Figure 4h). The third generation of pyrite is <10 μm across, subhedral to euhedral, and present in alteration zones containing the third vein (Figure 4i). The paragenesis is illustrated in Figure 5.

4. Sampling and Analytical Methods

Fresh samples were collected from each of the vein sets at depth in the Jianchaling mine. The samples were examined in thin section to confirm their paragenetic relationship. The sample characteristics are listed in Table 1.
Six samples of pyrite from the second (mineralised) vein set and five samples of the Duantouya Formation and meta-ultramafic from the wall-rock were collected for lead, strontium, and neodymium isotopic studies. The samples were crushed into power.
The samples were then crushed to a minus 10 mesh size (420 microns, and sulfide and carbonate fragments were handpicked under a binocular microscope. Between 10 and 50 mg of the powder was leached in acetone and washed in distilled and deionised water to remove contamination, then dried in an oven at 60 °C. The samples were then dissolved in a solution of HF + HNO3 + HClO4, dried, and redissolved in 6 N HCl, redried, and redissolved in 0.5 N HCl (for Sr and Nd separation) or 0.5 N HBr (for Pb separation). The Sr and Nd fractions were separated following standard chromatographic techniques using AG50 × 8 and PTFE–HDEHP resins with HCl as eluent. The Pb fraction was separated using a strong alkali anion exchange resin with HBr and HCl as eluents.
The lead isotopes were analysed using a MAT-261 thermal ionization mass spectrometer with the standard NBS 981 in the Analytical Laboratory at the Beijing Research Institute of Uranium Geology, China. Measurements of the common-Pb standard NBS 981 gave average 208Pb/206Pb values of 2.1681 ± 0.0008, 207Pb/206Pb of 0.91464 ± 0.00033, and 204Pb/206Pb values of 0.059042 ± 0.000037; the uncertainty is of <0.1% at the 95% confidence level. Some of the U, Th and Pb values were used to estimate the Pb isotope ratios assuming an age of 198 Ma, which is the 40Ar/39Ar date determined on fuchsite from the Jianchaling deposit [39]. These Pb isotopic ratios are presented as (208Pb/204Pb)i, (207Pb/204Pb)i and (206Pb/204Pb)i.
A TRITON thermal ionization mass spectrometer was used to measure the Sr and Nd isotopes in the Analytical Laboratory at the Tianjin Institute of Geology and Mineral Resources, China. The 87Sr/86Sr isotope ratios were normalized against the 86Sr/88Sr = 0.1194 and 143Nd/144Nd isotope ratios to 146Nd/144Nd = 0.7219. The JNdi Nd-Standard yielded 143Nd/144Nd ratios of 0.512118 ± 0.3 against a reference value of 0.512115 ± 0.7 [52], and the NBS 987 Sr standard with a reference level of 0.710248 was used yielding 87Sr/86Sr ratios of 0.710250 ± 0.7. The Sr and Nd isotopic compositions were measured with a thermal ionization ISOPROBE-T mass spectrometer.

5. Isotope Results

The following are isotopic values determined from samples from the Jianchaling deposit.

5.1. Carbon, Oxygen and Hydrogen Isotopes

The δ13C, δ18O and δD values from quartz and carbonate from each of the three vein sets and the surroundings rocks are listed in Table 2. These results are published on [21]. The δ13C values for first vein set ranges from −4.4 to 0.6‰, the δ13C values for the second (mineralised) vein set ranges from −2.9 to −0.4‰, and the δ13C value for the third vein set is between −4.4 to 2.2‰ (Table 2).
The δ18O values from carbonate and quartz for the first vein set forms two groups of 18.9–23.4‰ and 14.0–17.3‰. The δ18O values from the second vein set are between 13.8 and 19.0‰ (averaging 16.4‰), and for the third vein set are between 11.9 and 16.3‰ (Table 2).

5.2. Sulfur Isotopes

The δ34S isotopic values for the sulfides samples are listed in Table 3 and cited from [21]. The Jianchaling deposit is characterized by highly δ34S positive values with a narrow range. The first vein set has a δ34S value of 14.3‰ (Table 3). The second vein set has δ34S values between 8.2 and 14.3‰. One shale rock sample of the Duantouya Formation have δ34S values of 16.6‰. Two samples of the metamorphosed ultramafic rocks (listwanite and serpentinite) have δ34S values of 6.1 to 8.6‰.

5.3. Lead Isotopes of Sulfides and Wall Rocks

The Pb isotopic analyses completed for this study and previous data are listed in Table 4. In order to compare the contribution of the wall rocks, we also put the lead isotopes of the wall rocks including Yudongzi Fm, Porphyritic granite, Duantouya Fm and Bikou Group in Table 3. Sulfides from gold deposits have 206Pb/204Pb values between 17.257 and 18.477, 207Pb/204Pb values between 15.530 and 15.704, and 208Pb/204Pb values of 36.927 to 38.757 (Table 4). Their calculated (206Pb/204Pb)i, (207Pb/204Pb)i and (208Pb/204Pb)i values are the same as the measured values due to their very low U and Th contents. Therefore, the analytical data is interpreted as being reliable and representative of the source for metals in the mineralising fluid. The ultramafic rocks have 206Pb/204Pb values of 17.952–19.193, 207Pb/204Pb values of 15.520–15.785, and 208Pb/204Pb ratios of 36.029–38.920 (Table 4).

5.4. Strontium and Neodymium Isotopes of Sulfides and Wall Rocks

Four pyrite samples from the gold-bearing second generation vein set have ISr values in the range 0.706709–0.715929 (average of 0.711973, Table 5), which is similar to that of the meta-ultramafic rocks. The (143Nd/144Nd)i values of the samples are between 0.511376 and 0.512453 (average of 0.511823, Table 6), and the εNd values are between −19.6 and 1.4.
Samples from the Duantouya Formation have (143Nd/144Nd)i values of 0.511865–0.512114 (average of 0.511953, Table 6), and εNd values of −10.1 to −5.3. The meta-ultramafic samples have (143Nd/144Nd)i values of 0.512137–0.512152 (average of 0.512144, Table 6), and εNd values between −4.8 and −4.5.

6. Discussion

6.1. Sources of Metals and Mineralising Fluids

6.1.1. Oxygen and Hydrogen Stable Isotopes

The oxygen and hydrogen stable isotopes are often used to indicate the source of mineralised hydrothermal fluids [62]. However, the overlap in the metamorphic and magmatic fields in δD versus δ18O diagrams creates uncertainty in deciphering the genesis of mineralisation [63]. This is the case for the mineralising fluid at Jianchaling, which has been interpreted as being magmatic [64,65], meteoric [53], mixed metamorphic and magmatic [42,43,51], and primarily metamorphic [39]. This places a significant doubt on the usefulness of the δD and δ18O values in directly pinpointing the origin of the mineralising fluid at Jianchaling.
Using fluid-inclusion homogenisation temperatures and detailed paragenetic studies by Yue [39] (Table 2), the δ18Owater values were calculated using the quartz–water equation by [54] and carbonate–water equation by [55]. The calculated quartz-carbonate δ18O values for the hydrothermal fluid associated with the first vein set range from 7.5 to 17.7‰, the mineralised second vein set have δ18O values between 5.7 and 11.1‰, and the third vein set range from 1.3 to 4.3‰ (Table 2). Using this data, the δ18O and δD values for first vein set plot in the magmatic field and close to the metamorphic field (Figure 6). However, assuming that magmatic fluids are generated above the lowest eutectic point at temperatures above 573 °C [66], continuous cooling and water-rock reactions result in reduction of δ18Owater values during the crystallisation of hydrothermal minerals such as quartz and alkali feldspar [66]. Furthermore, magmatic fluids have average δ18Owater values of 18.8‰ at temperatures of 355 °C [39], which is the average homogenization temperature of fluid inclusions from first vein generation (Table 2). This means that the initial δ18Owater value must have been higher than 18.8‰ at temperatures above 355 °C, which is higher than the 5.7–11.1‰ range for the mineralised second vein set. In addition, the Late Triassic to Early Jurassic plutons in the southern part of the Qinling Orogen commonly have δ18O values of <18.8‰. The high δ18O values for the early hydrothermal fluids are consistent with a major contribution from metamorphic sources (rather than a minor contribution as suggested by Figure 6). This interpretation is supported by the low salinity and high CO2 content of fluid inclusions in the first vein set [7,39]. Furthermore, the δ18O values for quartz in granite porphyry and aplite in the area range between 11.3 and 14.5‰ [67]. This indicates that the δ18Owater value of 10.0‰ calculated at a temperature of ~573 °C for the first vein set cannot exceed the δ18Owater value of 13.2‰ for the second vein set that crystallised at ~300 °C (as determined from the fluid inclusion homogenisation temperatures). In addition, the regional metamorphism in the Jianchaling area is at the greenschist facies [68], further supporting a ~300 °C temperature for the crystallisation of the mineralised second vein set.
The 3rd vein δ18Owater values are between 1.3 and 4.3‰, with a δD value of −81‰, they are plot in the meteoric field in Figure 6 and Figure 7. The δ18Owater values of carbonate-quartz from the mineralised vein set vary between 5.7 and 11.1‰, which are values between those for the first and third vein sets. Exactly, on the base of the δ18Owater values (5.7–11.1‰), we think the 2nd vein set is similar to lode gold deposits and add the possible range of the 2nd vein set in Figure 6 that based on the feature of many lode gold deposits worldwide. This is indicative of the mixing of metamorphic and meteoric fluids during mineralisation (Figure 6).
The δ 18O values for quartz from lode-gold deposits around the world are higher than 10‰ with the values for the mineralising fluids ranging between 5 and 25‰ [6]. The δ18Owater values of the gold deposits on the Jiaodong Peninsula of eastern China range from 4.9 to 10.9‰, with corresponding δ D values of −78 to −101‰ (Figure 6) [69,70]. The δ 18O and δD values for mineralising fluids at Jianchaling plot in the lode-gold deposit field (Figure 6; Table 2; [6]). Figure 6 also shows that the first vein set containing higher δ18O and δD values are sourced from metamorphic fluids. In contrast, the mineralised second vein set are similar lode gold deposits, and the fluids related to the third vein set have (again) a composition close to that of meteoric fluid.

6.1.2. Carbon and Oxygen Isotopes

The δ13CCO2 values determined for quartz-carbonate from each of the vein sets are essentially the same, hovering around approximated zero (Figure 7). The corresponding δ18OSMOW values show a significant trend with the first vein set being approximately 15‰, the mineralised second vein measuring around 9‰, and the third being around 3‰ (Figure 7). The implication for this trend is that all of the vein sets have similar sources for carbon with a gradual decrease in available oxygen in the hydrothermal fluid with time. Another implication is that there was only one hydrothermal fluid that has changed in composition with time.
The δ13CCO2 values for the hydrothermal fluids related to the three vein sets are significantly higher than the values for organic matter (averaging −27‰) [62], the content of CO2 in the atmosphere (−11 to −7‰ [62]), freshwater carbonate (−20 to −9‰ [72]), magmatic rocks (−30 to −3‰ [72]), the continental crustal (−7‰ [73]), and the mantle (−7 to −5‰ [72]). However, marine carbonate (i.e., −3 to 2‰ δ13CCO2 [72]) and carbonate in the wall rock (i.e., −0.4‰ to 2.3‰ δ13CCO2; Table 2), are similar in δ13CCO2 composition. This indicates a local source for the hydrothermal fluids related to each of the vein sets. In addition, the close relationship between the ultramafic rocks and the vein sets shown in Figure 7 indicates that the ultramafic rocks are also local sources for the carbon and oxygen in the hydrothermal fluids.
On the other hand, the δ13CCO2 and δ18OSMOW of the mineralised fluids overlap with those of the forming fluid of Archean Au deposits (Figure 7). δ18OSMOW value of the third vein sets are similar with the meteoric water, indicating meteoric water mixed into the fluid system in late stage.

6.1.3. Sulfur Isotopes

The δ34S signatures for various in the MLY and others from throughout the world are presented in Figure 8. The figure shows that most of the sulfides in the MLY have δ34S signatures greater than zero, are predominantly higher than those for orogenic Au deposits throughout the world, and higher than those for basaltic magmatic rocks, overlap the sulfide values in ultramafic rocks, and are coincide with the high end of sulfides in metamorphic rocks. In fact, the δ34S signatures for the metamorphic rocks are the best fit, which includes the wallrocks at Jianchaling (Table 3). Such heavy δ34S values for the sulfides at Jianchaling is consistent with derivation from sulfates that are characterised by heavy δ34S values [77,78]. It is envisages that organic material derived by the metasedimentary rocks in the study area would have reacted with sulfate resulting in the crystallisation of sulfides [78,79]. Examples of such reducing agents are CH4, C2H6, H2S and graphite, which have been detected in fluid inclusions using Laser Raman [39]. The conversion of sulfate to sulfide will proceed in the following chemical reaction:
CH4 + SO42− ←→ H2S + H2O + CO32− and H2S + Fe2+ ←→ FeS + 2H+
Therefore, the Neoproterozoic metamorphic rocks in the MLY are likely sources for sulfur in the Jianchaling area.

6.1.4. Lead Isotopes

The country rocks in the Jianchaling area have a wider range in Pb isotopic (206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb) ratios than the sulfides in the Jianchaling mineralisation (Table 4). The range of the Pb-isotopes is shown in Figure 9 that includes trends defining tectonic settings [83]. The range of Pb-isotopes shown in Figure 9 correlates with defined tectonic setting of orogenic and upper crustal fields, even though there is a limited number of 10 data points. This is in agreement with the observations made in the discussion section above.
Furthermore, these Pb signatures of the sulfides from the mineralisation overlap those of the ultramafic rocks and the Bikou Group, indicating that the units are possible sources for the sulfides in the mineralisation. In contrast, the distinct incongruence of the sulfides from the mineralisation and the granitic rocks indicates that the granitic rocks are not the source for the sulfides in the mineralisation (Figure 9).

6.1.5. Strontium and Neodymium Isotopes

The ISr(t) values of sulfide samples from the Jianchaling deposit range from 0.706709 to 0.715929 (Table 5; Figure 10a). These values are higher than the mean values (0.703 to 0.705) established for mantle-derived oceanic basalt (MORB, OIB, IAB) and continental basalt, and are suggestive of a crustal source [84,85].
The ISr(t) values for the sulfide samples from the deposit are also lower than those for the Duantouya Formation (Table 5), and the (143Nd/144Nd)i sulfide ratios for the mineralised second vein set overlap with those of the Duantouya Formation and the meta-ultramafic rocks (Table 6; Figure 10a,b). The εNd (t) and Isr (t) of sulfide are indicative of a crustal source and dominated with mature Sr-Nd character (Table 5 and Table 6; Figure 10a), and εNd (t) overlaps with meta-ultramafic field, indicated that the Duantouya may play an important role during the ore formation and there may exist minor ultramafic source been involved in the ore fluid.
The Bikou Group has ISr(t) values that overlap with those from the Mian-Lue ophiolite, meta-ultramafic rocks, partly with the second vein set, and are lower than those from the Duantouya Formation (Figure 10a; Table 5 and Table 6) [60,61,86]. Although the pyrite in audiferous rocks has ISr(t) values that overlap with porphyritic granite partly (Figure 10c), it is unlikely to come from porphyritic granite, the evidence is mainly from lead isotopes, as mentioned above.
These relationships can be explained with a mixing model where the mineralised sulfide-bearing fluids interacted with lithological units (Figure 10). This interpretation is supported by the conclusion drawn from the Pb isotope data collected from the Huachanggou gold deposit in the northwestern part of MLY [25,59] (Figure 1c).

6.2. Mineralisation Type

Various mineral-types have been proposed for the Jianchaling Au deposit. These include: (1) a magmatic hydrothermal source associated with Triassic magmatism [65]; (2) Carlin-like affiliations [8]; (3) orogenic affiliations [43]; and (4) sourced from structurally controlled altered rocks [40,53].
Fuchsite separated from the mineralised second vein set yield a well-defined 40Ar/39Ar isotopic age of 198 ± 2 Ma, which suggests that the mineralisation took place during the Triassic Indosinian Orogeny [39]. Implications of this are that the Neoproterozoic (ca. 927 Ma) magma-hydrothermal event associated with the emplacement of ultramafic intrusions. Triassic (ca. 216 Ma) porphyritic granites in the area are ~18 Ma older than the Jianchaling mineralisation, again indicating that the granites are not related to the gold mineralisation.
The C, H and O stable isotopes indicate that the ore-forming fluids are predominantly metamorphosed in origin and contaminated with meteoric fluid during the deposition of the gold at Jianchaling. On the other words, the mineralising fluid is probably sourced from the metamorphic dehydration of carbonate rocks in the Duantouya Formation, and gradually mixed with meteoric water. The 87Sr/86Sr, ISr(t), εNd, Pb and S isotopic data (Figure 10) confirm that the sulfides in the mineralised are sourced from the metamorphosed Duantouya Formation, Bikou Group and minor ultramafic rocks.
From the discussion above, combining the comparison of the geological characteristics between Jianchaling and Orogenic gold deposit (Table 7), the Jianchaling deposit is here interpreted as an orogenic-type deposit and summarised in Figure 11.

7. Conclusions

Hydrogen, oxygen and carbon isotopic systematics indicate that the ore-forming fluids at the Jianchaling Au deposit progressively evolved from an early stage represented by the first vein set associated with deformation and metamorphism of the country rocks. This was succeeded by a late tectonic stage represented by the mineralised second vein set sourced from a mixed metamorphic and meteoric fluid, and progressed to a late stage represented by the third vein set. The S-Pb-Sr-Nd isotopic data indicate that the mineralising fluids were sourced locally around Jianchaling. From these observations, the Jianchaling Au deposit is interpreted as an orogenic Au deposit formed during the Mesozoic Indosinian Orogeny.

Acknowledgments

The National Natural Science Foundation (Numbers 41403032, 41502070 and 41202050), and the National Crisis Mine Prospecting Foundation (Number 20089934) financially supports this study. We are grateful to Wenping Zhu for help during isotope analyses and the Exploration Team ‘711’ of Northwest Mining and Geology Group Co., Ltd. for their help during field. Yanjing Chen, Huayong Chen and three anonymous reviewers are thanked for their constructive suggestions, which have greatly improved this manuscript.

Author Contributions

Su-Wei Yue and Zhen-Wen Lin participated in field samples collection; Su-Wei Yue conceived and designed the experiments; Su-Wei Yue and Jing Fang performed the experiments; Deng-Feng Li and Leon Bagas analyzed the data; Su-Wei Yue wrote the paper, assisted by all other authors.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Geological maps showing: (a) the tectonic setting of China; (b) tectonic subdivision of Qinling Orogen and location of the Mianxian, Lueyang, and Yangpingguan (MLY) area [18]; and (c) regional geology and location of gold deposits in the MLY [39].
Figure 1. Geological maps showing: (a) the tectonic setting of China; (b) tectonic subdivision of Qinling Orogen and location of the Mianxian, Lueyang, and Yangpingguan (MLY) area [18]; and (c) regional geology and location of gold deposits in the MLY [39].
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Figure 2. Geological sketch map of the Jianchaling Au deposit [21,39].
Figure 2. Geological sketch map of the Jianchaling Au deposit [21,39].
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Figure 3. Cross-section of the of the Jianchaling Au deposit at a 870 m elevation showing the relationship of the mineralisation and fault [21,51].
Figure 3. Cross-section of the of the Jianchaling Au deposit at a 870 m elevation showing the relationship of the mineralisation and fault [21,51].
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Figure 4. Photomicrographs of samples from the Jianchaling Au eposit showing: (a) intergrown pyrite and fuchsite in the mineralised second vein set; (b) a second vein set with quartz containing pyrite; (c) third vein set with comb-like quartz, calcite and dolomite vein orpiment and realgar; (d) pyrite in the first vein set intergrowth; (e) fine-grained cataclastic pyrite following schistosity developed during brittle-ductile deformation before emplacement of the mineralised second vein set; (f) pyrite wrapping sphalerite and chalcopyrite in the mineralised second vein set; (g) pyrite in the first vein set overgrown by pyrite related to the mineralised second vein set; (h) hematite formed from pyrite, and martite; (i) euhedral fine-grained pyrite in the third vein set. Abbreviations: Cal = calcite; Car = carbonates; Cpy = chalcopyrite; Dol = dolomite; Fuc = fuchsite; Hm = hematite; Orp = orpiment; Py = pyrite; Q = quartz; Rea = realgar; Sph = sphalerite.
Figure 4. Photomicrographs of samples from the Jianchaling Au eposit showing: (a) intergrown pyrite and fuchsite in the mineralised second vein set; (b) a second vein set with quartz containing pyrite; (c) third vein set with comb-like quartz, calcite and dolomite vein orpiment and realgar; (d) pyrite in the first vein set intergrowth; (e) fine-grained cataclastic pyrite following schistosity developed during brittle-ductile deformation before emplacement of the mineralised second vein set; (f) pyrite wrapping sphalerite and chalcopyrite in the mineralised second vein set; (g) pyrite in the first vein set overgrown by pyrite related to the mineralised second vein set; (h) hematite formed from pyrite, and martite; (i) euhedral fine-grained pyrite in the third vein set. Abbreviations: Cal = calcite; Car = carbonates; Cpy = chalcopyrite; Dol = dolomite; Fuc = fuchsite; Hm = hematite; Orp = orpiment; Py = pyrite; Q = quartz; Rea = realgar; Sph = sphalerite.
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Figure 5. Paragenetic relationship of the minerals at the Jianchaling Au deposit [21].
Figure 5. Paragenetic relationship of the minerals at the Jianchaling Au deposit [21].
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Figure 6. Stable isotope (δD versus δ18O) plot for mineralised fluids at the Jianchaling Au deposit [71]. Included are the fields for the Xiaoqinling and Jiaodong gold deposits [69]; Juneau gold belt, Mother Lode, Victorian Goldfields and Meguma Terrace Au deposits [6].
Figure 6. Stable isotope (δD versus δ18O) plot for mineralised fluids at the Jianchaling Au deposit [71]. Included are the fields for the Xiaoqinling and Jiaodong gold deposits [69]; Juneau gold belt, Mother Lode, Victorian Goldfields and Meguma Terrace Au deposits [6].
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Figure 7. δ18OSMOW versus δ13CV-PDB plot for the Jianchaling Au deposit [21]. Data sources: greenschist facies carbonate rocks after [74]; reduced C in sedimentary and metamorphic rocks after [75]; carbonates in most orogenic Au deposits after [76].
Figure 7. δ18OSMOW versus δ13CV-PDB plot for the Jianchaling Au deposit [21]. Data sources: greenschist facies carbonate rocks after [74]; reduced C in sedimentary and metamorphic rocks after [75]; carbonates in most orogenic Au deposits after [76].
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Figure 8. δ34S values for hydrothermal sulfides from the Jianchaling Au deposit. Data sources: Basaltic rocks, Granitic rocks, Metamorphic rocks and Sedimentary rocks after [62,72,80]; Juneau gold belt, Bendigo Au, Kumtor Au and Major orogenic Au deposits in the world after [12,81]; Shanggong Au and Tieluping Ag after [44]; Yindongpo Au after [66]; Poshan Ag after [82]; Major Au deposits in the Qinling Orogen [24].
Figure 8. δ34S values for hydrothermal sulfides from the Jianchaling Au deposit. Data sources: Basaltic rocks, Granitic rocks, Metamorphic rocks and Sedimentary rocks after [62,72,80]; Juneau gold belt, Bendigo Au, Kumtor Au and Major orogenic Au deposits in the world after [12,81]; Shanggong Au and Tieluping Ag after [44]; Yindongpo Au after [66]; Poshan Ag after [82]; Major Au deposits in the Qinling Orogen [24].
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Figure 9. The plumbotectonic model for Pb isotopic systematics for the Jianchaling Au deposit. (a) 206Pb/204Pb versus 208Pb/204Pb; (b) 206Pb/204Pb versus 207Pb/204Pb.
Figure 9. The plumbotectonic model for Pb isotopic systematics for the Jianchaling Au deposit. (a) 206Pb/204Pb versus 208Pb/204Pb; (b) 206Pb/204Pb versus 207Pb/204Pb.
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Figure 10. Isotope systematics for the Jianchaling Au deposit showing: (a) ISr(t) versus εNd(t) plot (data for the Bikou Group is from [86]); (b) (143Nd/144Nd)i plot; and (c) 87Sr/86Sr plot. The range of the Mian-lue ophiolite is from [23]. T = 198 Ma.
Figure 10. Isotope systematics for the Jianchaling Au deposit showing: (a) ISr(t) versus εNd(t) plot (data for the Bikou Group is from [86]); (b) (143Nd/144Nd)i plot; and (c) 87Sr/86Sr plot. The range of the Mian-lue ophiolite is from [23]. T = 198 Ma.
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Figure 11. Tectonic model for the Jianchaling Au deposit [39].
Figure 11. Tectonic model for the Jianchaling Au deposit [39].
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Table 1. The geological characteristics of samples from the Jianchaling Au deposit (modified from [21]).
Table 1. The geological characteristics of samples from the Jianchaling Au deposit (modified from [21]).
Sample NO.MineralSample DescriptionStageAnalyzed Isotope
800-53-2DolomiteDolomite veins in the Serpentinite with shear deformation1C, O
860-52-7DolomiteDolomite veins in the Serpentinite with shear deformation1C, O
J-6DolomitePale green dolomite veins in the cataclastic dolomite1C, O
913-32-7CalciteCalcite veins in the cataclastic dolomite with a small number of pyrites2C, O
913-32-6CalciteCalcite veins in the cataclastic dolomite with a small number of pyrites2C, O
913-1DolomiteMilky white dolomite vein3C, O
913-2DolomiteMilky white dolomite vein3C, O
960-38-1DolomiteMilky white dolomite vein3C, O
860-51-5DolomiteDolomite veins in the listwanite with a small number of pyrites3C, O
860-51-6DolomiteDolomite veins in the listwanite with a small number of pyrites3C, O
hjy-8PyriteGrain cluster pyrite with shear deformation1S, Pb
J3PyriteMassive sulfide ore2S, Pb, Sr, Nd
J3PyrrhotiteMassive sulfide ore2S
hjy-1PyriteSilicified and fuchsite dolomite ore rocks with disseminated pyrites2S, Pb, Sr, Nd
hjy-12PyriteSilicified and fuchsite dolomite ore rocks with disseminated pyrites2S, Pb, Sr, Nd
hjy-10PyriteIntensive silicified and fuchsite dolomite ore rocks with disseminated pyrites2S, Pb, Sr, Nd
hjy-20PyriteSilicified and fuchsite dolomite ore rocks with disseminated pyrites2S, Pb, Sr, Nd
hjy-14PyriteWeak silicified and fuchsite dolomite ore rocks with disseminated pyrites2S, Pb, Sr, Nd
H-4Whole-rockShale (Duantouya Formation) S, Pb, Sr, Nd
960-34-1Whole-rockDolomite S, Pb, Nd
960-28-1Whole-rockDolomite S, Pb, Sr, Nd
780-50-3Whole-rockSerpentinite S, Pb, Sr, Nd
800-52-1Whole-rockListwanite S, Pb, Sr, Nd
Table 2. C-H-O isotope composition of mineralisation at the Jianchaling Au deposit (modified from [21]).
Table 2. C-H-O isotope composition of mineralisation at the Jianchaling Au deposit (modified from [21]).
Sample No.SampleVein SetMineralδ18Omineral (‰)Average δ18OWater (‰)δDWater (‰)δ13C V−PDB (‰)Average δ13CCO2 (‰)T# (°C)Reference
MS-57Au mineralisation1quartz17.310.8 (8.3 to 12.1)−72 310 (250 to 355)[53]
MS-79Au mineralisation1quartz17.010.5 (8.0 to 11.8)−85 310 (250 to 355)[53]
MS-52Au mineralisation1quartz16.610.1 (7.6 to 11.4)−79 310 (250 to 355)[53]
MS-77Au mineralisation1quartz14.07.5 (5.0 to 8.8)−70 310 (250 to 355)[53]
800-53-2Au mineralisation1dolomite23.417.7 (15.7 to 18.8) −0.31.7 (0.7 to 2.2)310 (250 to 355)[53]
J6Au mineralisation1dolomite18.913.2 (11.2 to 14.3) 0.62.6 (1.6 to 3.1)310 (250 to 355)[53]
860-52-7Au mineralisation1dolomite19.113.4 (11.4 to 14.5) −4.4−2.4 (−3.4 to −1.9)310 (250 to 355)[53]
Average 18.011.9 (9.6 to 13.1)−77−1.40.6 (−0.4 to 1.1)
913-32-6Au mineralisation2calcite17.09.1 (7.2 to 11.2) −2.9−1.9 (−3.0 to −0.9)240 (200 to 300)[21]
913-32-7Au mineralisation2calcite16.58.6 (6.7 to 10.7) −1.7−0.7 (−1.8 to 0.3)240 (200 to 300)[21]
P633-61-I1Au mineralisation2calcite19.011.1 (9.2 to 13.2) −0.60.4 (−0.7 to 1.4)240 (200 to 300)[41]
J163Au mineralisation2dolomite16.48.3 (6.4 to 10.4) −1.6−0.8 (−1.8 to 0.3)240 (200 to 300)[41]
J170Au mineralisation2dolomite13.85.7 (3.8 to 7.8) −0.40.4 (−0.6 to 1.5)240 (200 to 300)[41]
J180Au mineralisation2dolomite14.66.5 (4.6 to 8.6) −1.2−0.4 (−1.4 to 0.7)240 (200 to 300)[41]
J14Au mineralisation2ferrocalcite17.59.6 (7.7 to 11.7) −1.1−0.1 (−1.2 to 0.9)240 (200 to 300)[41]
Average 16.48.4 (6.5 to 10.5) −1.4−0.4 (−1.5 to 0.6)
913-1Au mineralisation3dolomite13.83.2 (0.4 to 4.8) 1.61.0 (−0.5 to 1.9)190 (150 to 220)[21]
913-2Au mineralisation3dolomite11.91.3 (−1.5 to 2.9) 2.21.6 (0.1 to 2.5)190 (150 to 220)[21]
960-38-1Au mineralisation3dolomite13.12.5 (−0.3 to 4.1) 0.60 (−1.5 to 0.9)190 (150 to 220)[21]
860-51-5Au mineralisation3dolomite14.84.2 (1.4 to 5.8) −4.4−5.0 (−6.5 to −4.1)190 (150 to 220)[21]
860-51-6Au mineralisation3dolomite14.94.3 (1.5 to 5.9) −4.1−4.7 (−6.2 to −3.8)190 (150 to 220)[21]
MS-69Au mineralisation3quartz16.33.9 (0.8 to 5.8)−81 190 (150 to 220)[41]
Average3 14.13.2(0.4 to 4.9) −0.8−0.7(−2.9 to −0.5)
P404-44B-2Mineralized dolostone dolomite22.9 0.0 [41]
P404-43BAltered dolostone dolomite18.0 0.1 [41]
P406-Y-43wAltered dolostone dolomite16.9 0.7 [41]
J142Dolostone dolomite22.5 2.3 [41]
J171Dolostone dolomite23.1 2.3 [41]
J25Dolostone dolomite22.3 −0.4 [41]
Average 21.0 0.8 [41]
J167Serpentinite dolomite15.0 −3.8 [41]
J42-1Listwanite magnesite14.3 −2.7 [41]
J59Listwanite magnesite16.3 −3 [41]
Y-MgListwanite listwanite13.8 −3.2 [41]
Y-MgListwanite listwanite13.8 −3.2 [41]
G-MgListwanite listwanite13.4 −2.2 [41]
Average 14.5 −3.0
Notation: # the peak of homogenization temperatures (the range of homogenization temperatures) are from [39]. The δ18Owtaer values were calculated using equations for quartz–water and carbonate–water [54,55]. The δ13C in CO2 equilibrated with dolomite and calcite were calculated using the equations of [56,57].
Table 3. Sulfur isotope composition of sulfides and whole rocks in the Jianchaling area (modified from [21]).
Table 3. Sulfur isotope composition of sulfides and whole rocks in the Jianchaling area (modified from [21]).
SampleMineralδ34Sv-CDT (‰)SampleMineralδ34Sv-CDT (‰)
hjy-1 (second vein set)cPy11.3Carbonate (Duantouya Fm) aPy16.4
hjy-12 (second vein set) cPy10.0Carbonaceous shale (Duantouya Fm) aPy5.4
hjy-10 (second vein set) cPy10.8Carbonaceous shale (Duantouya Fm) aPy10.6
J3 (second vein set) cPo8.2Carbonate (Duantouya Fm) aPy12.5
J3 (second vein set) cPy8.7Hc-Py1 (serpentinite) aCpy12.0
hjy-20 (second vein set) cPy13.2L-Py-Mt (listwanite) aPo10.5
hjy-14 (second vein set) cPy14.3Ni-bearing ultramafics aPy9.3
hjy-8 (first vein set) cPy14.3Ni-bearing ultramafics aPy11.3
H-4 Shale (Duantouya Formation) cWhole rock16.6Ni-bearing ultramafics aPy13.2
800-52-1 (listwanite) cWhole rock6.1Ni-bearing ultramafics aPy10.9
780-50-3 (serpentinite) cWhole rock8.6Ni-bearing ultramafics aPy11.1
965-Y-45-46 IIPy8.5Ni-bearing ultramafics aPy9.5
PD503-Y-Py1-2 IIPy15.4Ni-bearing ultramafics aPy11.7
PD404-cm43-Py aPy13.9Ni-bearing ultramafics aPy10.5
PD406-cm45N-Py aPy14.2Ni-bearing ultramafics aPy12.3
PD404-cm45S-Py aPy18.5Ni-bearing ultramafics aPy14.1
PD503-Ym-Py3 aPy17.3Ni-bearing ultramafics aPy12.1
PD404-cm43B-Py1 aPy12.8Ni-bearing ultramafics aPy11.7
965-47E-Ym aRea, Orp10.9Ni-bearing ultramafics aPy11.7
PD383-cm58-H1 aRea, Orp10.5Ni-bearing ultramafics aPy11.4
PD633-cm43B-Py1 aPy12.6Ni-bearing ultramafics aPy10.0
G-E-1 aPy17.0Ni-bearing ultramafics aPy10.9
PD383-Y-Py1 aPy12.6Ni-bearing ultramafics aPy6.1
PD633-Ym-59 aPy12.0Ni-bearing ultramafics aPy12.9
97-ZHE-H1 aPy11.2Ni-bearing ultramafics aPo7.8
Au mineralisationPy6.3Ni-bearing ultramafics aPo10.6
Au mineralisationPy15.3Ni-bearing ultramafics aPo9.1
Sm-P (albite porphyry) aPy11.0Ni-bearing ultramafics aPo10.0
N124 (albite porphyry) aPy14.6Ni-bearing ultramafics aPo12.5
L-Py (albite porphyry) aPy12.9Ni-bearing ultramafics aPo10.7
Porphyritic granite aPy11.8Ni-bearing ultramafics aPo12.3
Porphyritic granite aPy12.8Ni-bearing ultramafics aPo11.4
Porphyritic granite aPy17.5Ni-bearing ultramafics aPo10.9
Porphyritic granite aPo11.6Ni-bearing ultramafics aPo11.4
Porphyritic granite aPo13.7Ni-bearing ultramafics aPo11.8
Porphyritic granite aPy9.0Ni-bearing ultramafics aPo11.1
Porphyritic granite aPy15.2Ni-bearing ultramafics aPo8.2
Porphyritic granite aPy15.2Ni-bearing ultramafics aPo10.5
Porphyritic granite aPy15.2Ni-bearing ultramafics aPo11.6
Porphyritic granite aPy8.3Ni-bearing ultramafics aPo10.2
Porphyritic granite aPy10.6Ni-bearing ultramafics aPy10.3
Porphyritic granite aPy9.5Ni-bearing ultramafics aPy12.1
Porphyritic granite aPy9.9Ni-bearing ultramafics aPy9.9
Carbonate (Duantouya Fm) aPy15.0Ni-bearing ultramafics aPy11.4
Carbonate (Duantouya Fm) aPy18.5Ni-bearing ultramafics aPy11.5
Carbonate (Duantouya Fm) aPo18.6Ni-bearing ultramafics aPy13.3
Carbonate (Duantouya Fm) aPo16.5Ni-bearing ultramafics aPy12.3
Carbonate (Duantouya Fm) aPy10.3Porphyritic granite bPy10.0
Superscripts: a [41]; b [50]; c [21]. Abbreviations: Cyp = chalcopyrite; Orp = orpiment; Py = pyrite, Po = pyrrhotite; Rea = realgar.
Table 4. Lead isotope composition of ore sulfide and wallrocks at the Jianchaling deposit and in the Bikou Group.
Table 4. Lead isotope composition of ore sulfide and wallrocks at the Jianchaling deposit and in the Bikou Group.
Sample No.SamplePbThU208Pb/204Pb207Pb/204Pb206Pb/204Pb(208Pb/204Pb)i(207Pb/204Pb)i(206Pb/204Pb)iReference
Au mineralised-rocks
hjy-1pyrite905.0000.3330.21638.75715.70418.47738.75715.70418.477This study
hjy-12pyrite170.0000.0700.15837.99615.53918.12637.99615.53918.124This study
hjy-10pyrite50.0000.0350.53937.08815.55017.60037.08815.54917.579This study
hjy-20pyrite60.9000.2660.04737.18015.56617.52237.17715.56617.521This study
hjy-14pyrite53.8000.0410.19337.13515.57717.68337.13515.57717.676This study
hjy-8pyrite352.0000.0190.06837.27515.54917.81137.27515.54917.811This study
J3pyrite395.0000.0640.22638.54715.61118.38138.54715.61118.380This study
pyrrhotite 37.49315.57917.931 [41]
pyrite 37.05515.55317.863 [41]
pyrite 36.92715.53017.257 [41]
Average 37.54515.57617.86537.71115.58517.938
Meta-ultramafic rocks
listwanite 36.02915.52017.952 [41]
listwanite 38.59115.52118.599 [41]
listwanite 38.60415.78519.193 [41]
800-52-1listwanite21.5000.0160.06238.06915.64118.72338.06915.64118.717This study
listwanite 38.15015.59718.260 [41]
antigorite 38.11815.63218.390 [41]
antigorite 38.48915.61618.633 [41]
780-50-3serpentinite31.5000.0410.05237.74815.61518.32737.74715.61518.324This study
serpentinite 38.92015.65718.553 [41]
serpentinite 38.03215.57018.833 [41]
meta-ultramafic 38.53315.53618.281 [58]
Average 38.11715.60818.52237.90815.62818.521
Yudongzi Fm
Sericite-quartz-schist 38.20415.66318.432 [41]
leptynite 39.16115.48117.863 [41]
Average 38.68315.57218.148
Porphyritic granite
magnetite 40.35915.80521.881 [41]
pyrrhotite 39.26515.77120.922 [41]
pyrite 38.33815.76521.637 [41]
Average 39.32115.78021.480
Duantouya Fm
H4shale115.0009.1204.58039.15615.76819.81939.10315.76419.737This study
960-34-1dolostone15.6000.0640.25037.51815.66719.16437.51515.66519.132This study
960-28-1dolostone31.8000.0160.21738.17015.82822.36438.17015.82722.350This study
limestone 38.17215.60118.365 [41]
dolomite 38.78315.56018.931 [58]
Average 38.36015.68519.72938.26315.75220.406
Bikou Group
spilite 37.62115.49117.661 [59]
phyllite 35.32815.38316.308 [59]
phyllite 36.95115.44717.076 [59]
quartz schist 37.86615.48617.677 [59]
phyllite3.21.30.438.12815.47117.64437.86915.45917.399[59]
siltstone3.21.30.438.39415.55218.12638.13215.54017.879[59]
phyllite3.21.30.438.06415.55318.01637.80315.54117.770[59]
metadolerite11.87.581.9940.06915.92818.76339.63915.91118.417[60]
metadolerite1.140.340.1239.15715.83318.01738.96215.82217.806[60]
metadolerite1.390.260.0938.94515.81417.91038.82315.80817.781[60]
Average 38.05215.59617.72038.53815.68017.842
Table 5. The Sr isotope ratios of sulfides and wallrocks at the Jianchaling Au deposit and in the Bikou Group.
Table 5. The Sr isotope ratios of sulfides and wallrocks at the Jianchaling Au deposit and in the Bikou Group.
No.MaterialVein SetRb (ppm)Sr (ppm)87Rb/86Sr87Sr/86SrIsrReferences
Mineralised rock
hjy-1Pyrite21.152.48- This study
hjy-10Pyrite20.5612.920.5562330.7141790.0012220.712613This study
hjy-12Pyrite20.6713.370.5764650.7142650.0012600.712642This study
hjy-14Pyrite20.8856.72- This study
hjy-20Pyrite20.4052.870.4086700.7170800.0009610.715929This study
J3Pyrite20.5311.580.9725530.7094470.0020040.706709This study
AverageN = 4 0.711973
PD404-43BAltered dolostone236.2089.6013.1647800.7134000.0024010.710107[41]
PD404-44B-2Mineralised rock24.207.8319.5936240.7184000.0031800.714026[41]
PD633-61-11Quartz2 0.720900 [41]
PD633-Y-57Calcite3 0.717300 [41]
AverageN = 2 0.712066
Wall rocks
J-15Porphyritic granite 77.5636.676.1363440.7355430.0124940.718266[41]
J-16Porphyritic granite 83.3948.794.9599440.7381590.0101870.724194[41]
J-18Porphyritic granite 83.6831.217.7895010.7496890.0160650.727757[41]
J-19Porphyritic granite 64.7830.826.1009340.7403880.0125080.723210[41]
J-60Porphyritic granite 58.00220.700.7605280.7097680.0015970.707627[41]
J-66Porphyritic granite 75.0379.032.7544930.7359190.0057040.728164[41]
J-69Porphyritic granite 86.9435.307.1435930.7329220.0144310.712809[41]
L-Py1Albite-rich intrusive 21.2058.801.0446310.7219000.0021840.718959[41]
AverageN = 8 0.720123
J-17Meta-ultramafics 0.2717.160.0455730.7184550.0004980.718327[41]
J-55Meta-ultramafics 1.5913.470.3414310.7046740.0008270.703713[41]
J-102Meta-ultramafics 1.335.580.6893010.7027610.0014460.700820[41]
J-118Meta-ultramafics 0.2535.270.0205010.7038700.0004720.703812[41]
G-E-MtMeta-ultramafics 2.9264.300.1314520.7123000.0005490.711930[41]
Hc-Fe-1(1)Meta-ultramafics 0.466.590.2020650.7128000.0006310.712231[41]
Hg-N-1Meta-ultramafics 0.333.920.2436950.7128000.0006880.712114[41]
97-Hw-1Meta-ultramafics 1.111.015.3584520.7296000.0065230.720628[41]
J-45Meta-ultramafics 1.904.582.8426410.7258620.0025100.722476[41]
J-50Meta-ultramafics 0.532.112.2183630.7177230.0015530.715675[41]
J-42-3Meta-ultramafics 0.280.694.3849710.7262830.0024600.722971[41]
Y-MgMeta-ultramafics 0.333.661.1533340.7134000.0007140.712665[41]
G-MgMeta-ultramafics 0.292.571.6667480.7134000.0008170.712480[41]
780-50-3Meta-ultramafics 1.572.971.5312510.7195170.0031400.715206This study
800-52-1Meta-ultramafics 0.100.800.3762580.7110250.0008950.709965This study
AverageN = 15 0.713001
PX406-Y-43WDuantouya Fm 1.69108.000.4477470.7190000.0004990.718872[41]
G-E-1Duantouya Fm 8.89101.002.6917450.7233000.0007200.722582[41]
H4Duantouya Fm 105.0057.205.3121340.7340270.0108560.719034This study
960-28-1Duantouya Fm 0.0317.900.0043700.7205820.0004930.720570This study
AverageN = 4 0.720265
2000224Bikou Group 19.55594.591.4632810.7044710.0005070.704203[61]
2000225Bikou Group 5.33118.582.0884920.7048990.0005380.704533[61]
2000226Bikou Group 3.9541.584.6016660.7032110.0007200.702438[61]
2000228Bikou Group 3.8718.1510.7569750.7035340.0013120.701797[61]
2000230Bikou Group 3.7339.704.9316850.7026500.0007150.701884[61]
2000231Bikou Group 23.01243.965.1269250.7133250.0007320.712556[61]
BK1Bikou Group 23.40563.002.3421300.7104190.0005360.710080[60]
BK2Bikou Group 0.21111.000.1103860.7073530.0004750.707338[60]
BK3Bikou Group 0.13143.000.0548470.7066680.0004740.706661[60]
AverageN = 9 0.705721
Table 6. The Nd isotope ratios of sulfides and wallrocks at the Jianchaling deposit.
Table 6. The Nd isotope ratios of sulfides and wallrocks at the Jianchaling deposit.
No.SampleStageSmNd143Nd/144Nd147Sm/144Nd(143Nd/144Nd)ifSm/NdεNd(198)
Sulfides
hjy-1Pyrite20.0520.1670.5124260.18830.512182–0.04–3.9
hjy-10Pyrite2 0.018
hjy-12Pyrite20.0850.7470.5133000.06880.512453–0.651.4
hjy-14Pyrite20.0120.0410.5119410.17690.511712–0.10–13.1
hjy-20Pyrite20.060.4250.5115000.08530.511389–0.57–19.4
J3Pyrite20.0260.1940.5114810.08100.511376–0.59–19.6
AverageN = 5 0.511823 10.9
Wallrocks
H4Duantouya Fm 3.79160.5120510.14320.511865–0.27–10.1
960-34-1Duantouya Fm 0.2161.290.5120120.10120.511881–0.49–9.8
960-28-1Duantouya Fm 0.0390.1290.5123500.18280.512114–0.07–5.3
AverageN = 3 0.5119530.288.4
780-50-3Meta-ultramafic rock 0.0580.2420.5123250.14490.512137–0.26–4.8
800-52-1Meta-ultramafic rock 0.0040.0130.5123930.18600.512152–0.05–4.5
AverageN = 2 0.5121440.164.7
Table 7. Geological characteristics comparison between the Jianchaling and Orogenic gold deposit.
Table 7. Geological characteristics comparison between the Jianchaling and Orogenic gold deposit.
Orogenic Gold Deposit aJianchaling Gold Deposit b
Tectonic settingSubduction hyperplasia, continental collision, intracontinental strike-slip and intracontinental compressional orogenic beltContinental collision
Ore-bearing terraneMetamorphic terraneMetamorphic and sedimentary terrane
Ore-controlling lithologyUltramafic volcanic rocks, intrusive rocks, miscellaneous sandstones, slateUltramafic and dolomite
Metamorphism of the host rockGreenschist facies (low green schist to low granulite)Greenschist to low amphibolite facies
Ore-controlling structuresIn the secondary or lower faults of the super-lithospheric fracture zone, the ore-forming structures is mainly the high angle oblique slip belt, the reverse overthrust belt, and also the transverse fracture, the ductile-brittle zoneIn the brittle fracture of the ductile shear zone (high angle thrust belt) in the basement fault zone
Ore and gangue mineralsMostly pyriteArsenic pyrite, marcasite, arsenopyrite, orpiment, realgar, quartz and calcite
Ore typeQuartz vein and altered rockAltered rock
Metallogenic hydrothermal fluids characteristicsAqueous solution with low salinity and low density, containing CO2 ± CH4 ± N2 ± H2S. The fluids inclusion type has H2O-CO2, rich CO2 (with an unquantifiable CH4 and a small amount of H2O) and gas-liquid two-phase H2O inclusionsAqueous solution with low salinity and low density, containing CO2 ± CH4 ± H2S. The fluids inclusion type has NaCl-H2O, CO2-H2O-NaCl ± CH4 and pure CO2-CH4
Metallogenic fluids salinity3–12 wt % NaCl equiv.0.4–15.6 wt % NaCl. equiv.
Main metallogenic temperature350 ± 50 °C200–320 °C
Mineralization pressure50–400 MPa117–354 MPa
Initial metallogenic fluids featureMetamorphic fluidsMetamorphic fluids
Superscripts: a [63,87,88]; b [21,39].

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