Source Of Ore-forming Materials Research Articles

Micro-Nanoscale Characteristics of Pyrite and Its Implications for Gold Mineralization: Two Cases of Gold Deposits in the Youjiang Basin and Southwestern Tianshan Mountains.

The mineralogical and compositional characteristics of gold-bearing minerals and the occurrence of gold are not only of great significance to exploring the sources of ore-forming materials and their formation mechanisms but also helpful for designing reasonable beneficiations and smelting schemes and achieving remarkable economic benefits. This paper presents an integrated study on the crystal characteristics, elemental composition and distribution of pyrite (the main gold-bearing minerals), on the basis of electron probe microanalysis (EPMA), scanning electron microscopy (SEM), laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and nano-secondary ion mass spectrometry (NanoSIMS). The occurrence of gold in the Shuiyindong gold deposit and Ashawayi gold deposit has been studied by means of microscopy, SEM, and EPMA images, elemental correlations, S-Fe-As ternary diagrams, logAs-logAu diagrams and Au/As ratios. The gold in pyrite of the Shuiyindong deposit is in the form of nano gold inclusions and lattice gold. The gold in pyrite of the Ashawayi deposit dominantly exists in the form of nano gold inclusions or is present as micro-nano gold particles in the cracks or edges of pyrite, some of which can exist as lattice gold. The ore-forming hydrothermal solution of the Shuiyindong gold deposit is mainly underground hot brine, but it may be reformed by a deep magmatic hydrothermal solution or volcanic-subvolcanic hydrothermal solution. The ore-forming hydrothermal solution of the Ashawayi gold deposit is mainly derived from the metamorphic hydrothermal solution formed during the orogenic process, and the ore-forming process or post-mineralization process may be reformed by the leaching of underground hot brine. Finally, the characteristics of ore-forming fluids and evolution of the two types of deposits are determined via pyrite element surface scanning. This paper shows that micro-nanoscale study of gold-bearing pyrite is of great significance to understanding the gold mineralization process and is worth further study.

Origin of the giant Luziyuan Zn-Pb-Fe(-Cu) distal skarn deposit, Baoshan block, SE Tibet: Constraints from Pb–Sr isotopes, calcite C–O isotopes, trace elements and Sm–Nd dating

Abstract The giant Luziyuan Zn-Pb-Fe(-Cu) deposit is located in the southern Baoshan block of SE Tibet. The deposit hosts over 4.2 million tonnes (Mt) of contained Zn + Pb metal and 301 Mt Fe ore reserve. The stratiform-/vein-type orebodies are hosted along the interlayer fractures in the Upper Cambrian Shahechang Formation marble and skarn. Three alteration/mineralization stages have been identified: (I) pre-ore, (II) syn-ore (oxide-ore and sulfide-ore), and (III) post-ore. An increasing Fe(-Cu) and decreasing Zn-Pb trend is present from the shallow-level SW to deep-level NE Luziyuan. Lead isotope compositions are similar among all Luziyuan ore sulfide types, and show positive correlations plotted between the regional Early Cretaceous granites and local wallrocks in both uranogenic and thorogenic diagrams, suggesting a mixed Pb source between intermediate-felsic magmatic fluids and sedimentary wallrocks. This is similar to many coeval northern Baoshan skarn deposits, e.g., Jinchanghe and Hetaoping. Initial 87Sr/86Sr ratios of the pre-ore (0.715919–0.720102), syn-ore (0.713502–0.719259) and post-ore (0.714091–0.720304) minerals lie between those of coeval granitoids and skarn deposits in the region and the average continental crust. This further supports a mixed ore-forming material source, and is suggestive of distal-skarn mineralization type. Syn-ore calcite samples yielded an Early Cretaceous Sm–Nd isochron age (130 ± 15 Ma). Regional tectonic evolution suggests that the Luziyuan mineralization was likely formed under post-collisional extension after the Lhasa-Tengchong accretion onto the Eurasian margin along Baoshan-Sibumasu. Such an extension had most likely induced crustal anatexis and the formation of the ore-causative S-type granites.

In situ geochemistry of dyke−marble interfaces obtained by portable X-ray fluorescence (pXRF) spectroscopy: Implications for sources of ore-forming materials in the Baiyinnuo'er Zn–Pb deposit, inner Mongolia, China

In situ analysis performed by portable X-ray fluorescence (pXRF) spectroscopy was used to measure two different contact interfaces of dyke and marble in the Baiyinnuo'er Zn–Pb deposit located in Inner Mongolia, China. The limit of detection (LOD) standardisation method was used to assess pXRF readings through dividing readings into low, medium and high concentrations, and readings were screened according to the concentration range distribution. Spatial trend analysis and enrichment factor calculation were used for data processing. In both profiles of quartz porphyry−marble (Q−M) and granodiorite−marble (G−M), high values of Ca and Mg, and Si, Al and K, respectively, could be used to distinguish the distribution of marble and dykes. However, there were significant differences in the distributions of ore-forming elements between the two profiles. No ore-forming elements were enriched near the contact interface of the Q−M profile, but all ore-forming elements, such as Zn, Pb, Cu and Fe, were significantly enriched in the skarns located between granodiorite and marble. Therefore, the intrusion of granodiorite resulted in the enrichment of ore-forming elements, and provided metals for mineralisation. Based on the results of the calculated enrichment factor for the G−M profile, the enrichment degree of selected elements in descending order was Pb, Zn > Ca > Fe > Al, Si > K in skarns relative to granodiorite, and Pb, Fe > Si, Al > Zn > K > Ca in skarns relative to marble. Zn and Pb were enriched in skarns relative to granodiorite but partially depleted relative to marble, indicating the high background Zn and Pb in marble; therefore, marble could provide at least part of the Zn and Pb. As a consequence, the intrusion of granodiorite resulted in skarnisation and mineralisation, and introduced ore-forming elements including Zn, Pb, Cu and Fe, but marble also provided at least part of the Zn and Pb, and the deposit was considered to be a skarn Zn–Pb deposit. In situ geochemical analysis at the outcrop scale is a useful approach for research into geological processes including skarnisation and mineralisation, as well as determining the source of ore-forming materials.

Mineralogy, geochemistry, and Sr–Pb and in situ S isotopic compositions of hydrothermal precipitates from the Tangyin hydrothermal field, southern Okinawa Trough: Evaluation of the contribution of magmatic fluids and sediments to hydrothermal systems

The Okinawa Trough (OT), is a back-arc basin where rifting is in its initial stages, and where hydrothermal fields (HTFs) have developed above terrigenous sediments and volcaniclastics layers of variable thickness. The source of ore-forming materials within the hydrothermal systems of the OT is complex, and may include seawater, magmatic rock, magmatic fluid, and sediments. The contribution of magmatic fluids and sediments to the hydrothermal systems of the OT is still uncertain. At least 10 modern seafloor HTFs have been reported from the OT, including the Jade, Hakurei, Iheya North Knoll, CLAM, Tangyin, Yonaguni Knoll IV, Hatoma, and Irabu. Here, we report results of mineralogical, geochemical, and whole-rock Sr–Pb and in situ S isotopic analyses of hydrothermal precipitates from the Tangyin HTF in the southern OT. This field was discovered during the HOBAB3 cruise in 2014 and contains four types of hydrothermal precipitates: Fe–Zn- and Zn–Pb-rich massive sulfides, silica-rich precipitates, and native sulfur-rich samples. Sulfates in Zn–Pb-, Fe–Zn-, and silica-rich samples have 87Sr/86Sr ratios of 0.71068–0.71750, which are higher than those of modern seawater and magmatic rocks, and indicate that the Sr is derived mainly from seawater and sediments. The Zn–Pb-, Fe–Zn-, and silica-rich samples have 206Pb/204Pb (18.5129–18.5307), 207Pb/204Pb (15.6374–15.6489), and 208Pb/204Pb (38.8759–38.9113) ratios that are intermediate between sediments and magmatic rocks, suggesting the Pb is a mixture of sediment- and magmatic-rock-derived Pb. The in situ S isotopic data indicate that the ore-forming fluids associated with all sample types had low δ34S values, with the Fe–Zn- (mean δ34S = 1.27‰ ± 1.38‰; SD, n = 12) and Zn–Pb-rich (mean δ34S = 0.93‰ ± 0.32‰; n = 36) massive sulfides, and silica-rich precipitates (mean δ34S = 2.85‰ ± 1.14‰; n = 58) having lower δ34S values than those of native sulfur-rich samples (mean δ34S = 4.23‰ ± 0.72‰; n = 5). The Zn–Pb- and Fe–Zn-rich massive sulfides, and silica-rich precipitates represent the medium–high temperature (>120 °C) early–middle stages of mineralization, formed under reducing conditions at low sulfur fugacity (fS2), based on the occurrence of low-fS2 mineral assemblages (e.g. high-Fe sphalerite ± isocubanite ± pyrrhotite). The low δ34S values of these three types of samples, and of the Hakurei and CLAM HTFs with low-fS2 mineral assemblages and low concentrations of Cu, Bi, and Au, most likely reflect the incorporation of biological sulfur previously formed by MSR within the sediments. The native sulfur-rich samples of the Tangyin HTF formed at low temperatures (<120 °C), and have slightly higher δ34S values than the Fe–Zn-, Zn–Pb-, and silica-rich samples, may reflect the incorporation of biological sulfur formed mainly by MSR during hydrothermal flow in a seawater recharge zone. Some sulfates in the Jade and Iheya North Knoll HTFs have δ34S values lower than that of modern seawater; this, in combination with high-fS2 oxidizing hydrothermal fluids, and high concentrations of Cu and Au in sulfide samples, indicates a magmatic fluid contribution to these HTFs.

Genesis of the Maoping carbonate-hosted Pb–Zn deposit, northeastern Yunnan Province, China: evidences from geology and C–O–S–Pb isotopes

The Maoping Pb–Zn deposit (~ 3 Mt Pb + Zn reserves with grades of 12–30 wt%) is one of the largest Pb–Zn deposits in the Sichuan–Yunnan–Guizhou (SYG) metallogenic province, which has contributed a tremendous amount of lead and zinc resources for China. To obtain a further understanding of the sources of ore-forming materials and ore genesis of the deposit, S–Pb isotopes of sulfides and C–O isotopes of ore-stage calcites were systematically collected from representative orebodies at different elevations with a Finnigan MAT-253 mass spectrometer. The calcites separated from the sulfides of the No I and No II orebodies shared identical δ13CPDB values (− 5.3 to − 0.8 ‰) and δ18OSMOW values (+ 14.5 to + 21.8 ‰) with those of the calcites in the SYG region, suggesting that CO2 in regional ore-forming fluids possibly had a homologous C–O source that originated from a ternary mixture of the dissolution of marine carbonate rocks, degassing process of the Emeishan mantle plume, and dehydroxylation of sedimentary organic matter. The No. I-1 and No. I-2 orebody was hosted in the same strata, but the sulfur source of No. I-1 orebody (+ 13.1 to + 19.0 ‰) with equilibrated sulfur fractionation (δ34Ssphalerite δ34Sgalena) were different. They were derived from the allopatry thermochemical sulfate reduction (TSR) of overlying Carboniferous sulfates in the ore-hosting strata and local TSR of sulfates in the ore-bearing Upper Devonian Zaige Formation, respectively. The narrow and uniform Pb isotopic ratios of single galena grains collected from sulfides with 206Pb/204Pb of 18.713–18.759, 207Pb/204Pb of 15.772–15.776 and 208Pb/204Pb of 39.383–39.467 indicate a well-mixed metal source(s) that consist of Proterozoic Kunyang and Huili Group basement rocks and Devonian to Middle Permian ore-hosting sedimentary rocks. Besides, the late Permian Emeishan basalts are difficult to contribute metals for regional Pb–Zn mineralization despite a closely spatial relationship with the distribution of the Pb–Zn deposit. This is supported by Pb isotopic ratios plotting above the average upper crustal Pb evolution curves and staying far away from that of the age-corrected Emeishan basalts. Hence, taking into account of the similarities in tectonic setting, ore-hosting rock, ore assemblage, wall rock alteration, ore-controlling structure, and ore-forming materials and the differences in relationship with regional magmatism, fluid inclusion characteristic and ore grade between the Maoping deposit and typical MVT Pb–Zn deposit, the ore genesis of the Maoping deposit should be an MVT like Pb–Zn deposit.

Geochronology, geochemistry, and Sr–Nd–Pb–Hf–S isotopes of the wall rocks of the Kanggur gold polymetallic deposit, Chinese North Tianshan: Implications for petrogenesis and sources of ore-forming materials

The Kanggur gold polymetallic deposit, located in the western segment of the Kanggur–Huangshan Shear Zone (KHSZ) of the Chinese North Tianshan, is the largest shear zone-controlled gold polymetallic deposit in this region. The gold mineralization is hosted by Early Carboniferous volcanic rocks of the Yamansu Formation, which is predominantly composed of andesite, dacite, and tuff. In this contribution, we present U–Pb age data and Hf isotopes of zircon from wall rocks associated with mineralization in the Kanggur deposit, as well as whole-rock geochemistry of the wall rocks with the goal of characterizing the petrogenesis of the deposit, and the sources of the ore-forming materials. Our new LA–ICP–MS zircon age data indicate that the wall rocks formed at ca. 340 Ma in the Early Carboniferous (andesite at 338.0 ± 1.7 Ma, dacite at 338.1 ± 2.2 Ma, rhyolite 332.4 ± 2.8 Ma, and granite porphyry at 342.6 ± 1.9 Ma). These wall rocks are enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs; e.g., U, K, and Pb), and depleted in high field strength elements (HFSEs; e.g., Nb, Ta, and Ti). Based on the lack of ancient crustal basement rocks in the Qoltag Arc, the lithological assemblage of andesite–dacite–rhyolite, the presence of chert, and the enrichment of andesite and dacite in Na2O (3.35–6.89 wt%) relative to K2O (0.67–2.42 wt%), it is inferred that the Early Carboniferous volcanic wall rocks of the deposit formed in an oceanic arc setting. Considering the similar isotopic compositions of andesite, dacite, rhyolite, and granite porphyry (εNd (t) = −0.12 to 0.64 and εHf(t) = 6.05 to 8.96 for andesite, εNd(t) = 1.01 to 3.02 for dacite; εNd(t) = 4.20 to 4.91 and εHf(t) = 11.02 to 13.79 for rhyolite, and εNd(t) = 1.65 to 2.13 and εHf(t) = 4.70 to 6.80 for granite porphyry) and juvenile Hf model ages (TDM1 = 610 to 730 Ma for andesite, TDM2 = 460 to 640 Ma for rhyolite, and TDM2 = 910 to 1050 for granite porphyry), it is suggested that the primary magma from which the andesite and dacite crystallized was derived from partial melting of metasomatized mantle wedge, whereas, the magma from which the rhyolite and granite porphyry crystallized was derived from partial melting of juvenile lower crust. The bulk S isotope composition (δ34SV-CDT) of these wall rocks varies from −0.8 to 8.7‰ (average of 4.8‰), with the S isotope composition of the andesite and rhyolite being similar to that of pyrite in mineralized rock. The bulk Pb isotope composition of these wall rocks ranges from 17.561 to 18.258 206Pb/204Pb, 15.535 to 15.602 207Pb/204Pb, and 37.593 to 38.118 208Pb/204Pb, with the Pb isotope composition of andesite being similar to that of pyrite from gold-bearing ores in the Kanggur deposit. The high abundance of sulfides in the wall rocks, and the similar S–Pb isotope compositions of ores and andesite suggests that the ore-forming materials were likely derived from the andesite wall rocks.

Timing and origin of multi-stage magmatism and related W–Mo–Pb–Zn–Fe–Cu mineralization in the Huangshaping deposit, South China: An integrated zircon study

The Huangshaping deposit (South China) is closely related to hypabyssal granites (e.g., quartz porphyry, granophyre, and granite porphyry), developing massive skarn-type W–Mo–Fe polymetallic mineralization, skarn-type Pb–Zn–Cu mineralization, and vein-type PbZn (Cu) mineralization. To better constrain the geochronology, fluid composition, magma source, metallogenic affinity, and source of ore-forming materials in the Huangshaping deposit, morphological, textural, in situ geochronological, compositional, and LuHf isotopic studies on zircons hosted in granitoids, skarns (ores), and wall rocks have been carried out. Overall, five types of zircons are identified: low-U magmatic (abbreviated as LUMZ), high-U magmatic (HUMZ), hydrothermally-altered metamict (HAZ), inherited, and detrital types. Round-shaped inherited and detrital zircons with low trace element compositions are rarely captured in the granite porphyry and largely hosted in sulfide skarn ores and wall rocks. The HUMZ are mainly observed in the granophyre and are easily distinguished from LUMZ by their much higher U, Th, and Y contents, black CL images, and stronger Eu anomalies. In addition, the crystallization time of HUMZ was later than that of LUMZ. The HAZ uniquely exists in granite porphyry and genetic-related skarns with cracked and porous textures and strong enrichment of many trace elements. These zircons were originally HUMZ that have undergone rapid partial metamictization and subsequent fluid-zircon interaction. This study demonstrates that the granophyre is a two-stage intrusion with ages of 179 ± 0.3 Ma and 163 ± 0.7 Ma, whereas the granite porphyry yields younger ages of 157 ± 0.5 Ma. The discovery of Triassic inherited zircons in the latter leads us to propose the presence of a concealed Triassic pluton (~220 Ma). The zircon populations of W−Mo−Fe mineralized garnet skarns are mainly composed of ~160 and 180 Ma magmatic zircons, whereas magnetite skarn ores contain both magmatic zircons (~50%) and inherited zircons (~50%). In contrast, inherited zircons are the dominant zircon population of the skarn Pb−Zn ores. This may indicate that the granite porphyry (the foremost one) and granophyre mostly contributed to the skarn-type W−Mo−Fe mineralization, whereas the Carboniferous and Devonian carbonate strata significantly contributed to the skarn-type Pb−Zn (Cu) mineralization. Fluids separated from the granite porphyry that modified the zircons are likely the principal ore-forming fluids, which are enriched in F, U, Th, Y, REE, Nb, Ta, Hf, Ca, P, Ti, Pb W, Mo, and Fe. Zircon Hf isotopes suggest that these magmas, at least the granophyre and granite porphyry, were generated by reworking of Mesoproterozoic crustal rocks without significant input of mantle materials. This study highlights the use of different types and generations of zircons from variable rock types to reveal fluid compositions and mineralization potentials in complex metallogenic systems.

Geology, isotope geochemistry, and geochronology of the Huamuqing carbonate-hosted Pb–Zn deposit, southwest China

As a carbonate-hosted deposit, the Huamuqing Pb–Zn deposit is situated in the western margin of the Yangtze Block. The strata-bound, irregular or vein-type Pb–Zn orebodies of the Huamuqing Pb–Zn deposit are mainly hosted by carbonate rocks of the Sinian Dengying Formation or Cambrian Meishucun Formation. Ores metallic minerals include mainly sphalerite, galena, and pyrite, whereas non-metallic minerals include mainly quartz and calcite. The alteration/mineralization can be divided into three stages: (I) the pyrite-quartz stage, (II) the polymetallic sulfide-quartz stage, and (III) the pyrite-calcite stage. The C–O isotopes of stage III hydrothermal calcite and multi-isotopes (S, Pb, Rb, Sr) of stage II sulfides were analyzed to constrain the ore-forming material source and mineralization timing at Huamuqing. The ranges of δ13CPDB and δ18OSMOW values for the stage III calcites are from − 0.641 to + 0.180‰ and + 17.542 to + 18.443‰, respectively. This suggests that the carbon of stage III was mainly derived from the Sinian dolostone, and the O isotope signatures of stage III were probably in connection with water/rock (W/R) interactions between the δ18O-depleted fluids and δ18O-enriched Sinian dolostone. The stage II sulfide δ34SCDT values vary from + 13.037 to +20.696‰, indicating that the reduced sulfur was originated mainly from Sinian to Triassic evaporites. The stage II sulfide 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ranges are from 18.184 to 18.393, 15.575 to 15.691, and 38.325 to 38.436, respectively. This demonstrates multiple Pb sources, which may have included sedimentary rocks, basement rocks, and basalts. Initial 87Sr/86Sr ratios of eight sphalerite samples range from 0.70815 to 0.71399, indicating that the ore fluids most probably came from or percolated through basement rocks, basalts, and sedimentary rocks. The mineralization timing was sphalerite Rb–Sr dated to be Late Triassic (204 ± 2 Ma), reflecting the Huamuqing deposit formed during late Indosinian. Hence, the Huamuqing deposit is a carbonate-hosted, thrust fault–controlled epigenetic Pb-Zn deposit that has a mixed source of ore-forming metals and ore-forming fluids.

Metallogenesis and major challenges of porphyry copper systems above subduction zones

Porphyry copper±molybdenum±gold deposits (PCDs) are the most representative magmatic-hydrothermal metallogenic system above subduction zones with important economic value. Previous studies revealed that large PCDs are generally formed from initial arc magmas (from subduction-induced partial melting of the mantle wedge), which eventually ascend to the shallow crust (3–5 km) for mineralization after a series of complex evolution processes. These processes include (1) the dehydration or partial melting of subducting slab, which induces partial melting of the metasomatized mantle wedge; (2) the ascent of mantle-derived magma to the bottom of the lower crust, which subsequently undergoes crustal processes such as assimilation plus fractional crystallization (AFC) or melting, assimilation, storage and homogenization (MASH); (3) the magma chamber formation at the bottom of the lower, middle and upper crust; (4) the final emplacement and volatilization of porphyry stocks; and (5) the accumulation of ore-forming fluids and metal precipitation. Despite the many decades of research, many issues involving the PCD metallogenic mechanism still remain to resolve, such as (1) the tectonic control on the geochemical characteristics of ore-forming magma; (2) the reason for the different lifespans of the long-term magmatic arc evolution and geologically “instantaneous” mineralization processes; (3) the source of ore-forming materials; (4) the relative contributions of metal pre-enrichment to mineralization by the magma source and by magmatic evolution; and (5) the decoupling behaviors of Cu and Au during the pre-enrichment. These issues point out the direction for future PCD metallogenic research, and the resolution to them will deepen our understanding of the metallogenesis at convergent plate boundaries.

Sources of the Laoxiongdong carbonate-hosted Pb–Zn deposit in Southwest China: constraints from S–Pb–Zn isotopic compositions

The Sichuan–Yunnan–Guizhou (SYG) Pb–Zn mineral province, which has significant Pb–Zn repositories in China, is situated in the western Yangtze Block. Despite decades of research, the Pb–Zn source of deposits is still disputed between the basement rocks, sedimentary wall rocks, or the Emeishan flood basalts. The newly-discovered Laoxiongdong Pb–Zn deposit is hosted by the Late Ediacaran Dengying Formation in the SYG province. Moreover, the Laoxiongdong orebodies lie between regional deep faults and close to the Proterozoic basement and Emeishan basalts. Hence, this deposit represents a good case study on the ore-forming material source for the regional Pb–Zn mineralization. The Laoxiongdong Pb–Zn ores are massive, vein, or disseminated and have mainly sphalerite, galena, pyrite, quartz, and calcite. In this paper, we present new sulfide S–Pb–Zn isotope data of the deposit. The sulfide δ34SCDT values (+ 11.8 to + 16.5 ‰) suggest that the reduced sulfur was mainly sourced from evaporites in the Late Ediacaran–Cambrian sequences. Pb isotopic ratios (206Pb/204Pb = 18.004–18.107, 207Pb/204Pb = 15.652–15.667, and 208Pb/204Pb = 38.037–38.248) suggest that the lead metal was primarily originated from the basement rocks. The sphalerite δ66Zn values (+ 0.16 to + 0.37 ‰) are also highly similar (within error) to those of basement rocks (+ 0.10 to + 0.34 ‰), suggesting a basement-rocks zinc source with minor contributions from the carbonate host rocks and Emeishan flood basalts. The narrow sphalerite Zn isotopic range (0.21 ‰) also indicates that the Zn isotopic fractionation between the sphalerite and initial fluid was limited during the sphalerite ore precipitation. Therefore, we propose that both the Late Ediacaran Dengying Formation rocks and Proterozoic basement rocks were important ore-forming material source for the Laoxiongdong deposit, whereas the Emeishan flood basalts represent only a minor ore-material source.

Geology, Fluid Inclusions and Stable Isotopes of the Xialiugou Polymetallic Deposit in North Qilian, Northwest China: Constraints on its Metallogenesis

The Xialiugou polymetallic deposit is located in the North Qilian Orogenic Belt, Northwest China, of which the main ore-bearing strata are the Middle Cambrian Heicigou Group. The mineralization is zoned with “black” orebodies (galena–sphalerite), which are stratigraphically above the “yellow” orebodies (pyrite–chalcopyrite–tennantite) at the lower zone, corresponding to the alteration assemblages of quartz–sericite in the ore-proximal zone and chlorite in the ore-distal zone. The Xialiugou mineralization can be divided into three stages: (1) Stage I (pyrite); (2) Stage II (chalcopyrite–tennantite–sphalerite); and (3) Stage III (galena–sphalerite). Fluid inclusions data indicate that the physicochemical conditions that lead to ore formation were the medium–low temperature (157–350 °C) and low salinity (0.17–6.87 wt % NaCleqv), and that the ore-forming temperature tended to decrease with the successive mineralization processes. Taking the H–O isotopic compositions (δDV-SMOW = −51.0‰ to −40.5‰, δ18OH2O = −0.4‰ to 8.6‰) into consideration, the ore-forming fluids were most likely derived from seawater with a small amount of magmatic- and meteoric-fluids input. In addition, the combined S (−3.70‰ to 0.10‰) and Pb isotopic (206Pb/204Pb = 18.357 to 18.422, 207Pb/204Pb = 15.615 to 15.687, 208Pb/204Pb = 38.056 to 38.248) data of pyrite indicate that the ore-bearing volcanic rocks may be an important source of ore-forming materials. Finally, we inferred that the Xialiugou deposit shares similarities with the most important volcanogenic massive sulfide (VMS) deposits (Baiyinchang ore field) in China and typical “black ore” type VMS deposits worldwide.

Major types and Metallogenic model of Early Cretaceous Pb-Zn and associated metal deposits in the southern Great Xing’an Range, NE China

The southern Great Xing’an Range (SGXR) is one of the most important non-ferrous metal ore concentrating areas in China, and a large number of Pb-Zn and associated metal deposits have been found and mined in this area. The Early Cretaceous deposits of SGXR can be divided into three principal types according to their geological characteristics: skarn type deposits, porphyry type deposits and hydrothermal vein type deposits. In this contribution, we list some important Early Cretaceous deposits in the SGXR and summarize their geological characteristics. Research of stable isotope and fluid inclusion reveal that the sources and properties of ore-forming fluids varied between different types of mineral deposits, while the sources of ore-forming materials of different deposits are similar(characterized by deep-seated magmatic activities). We therefore conclude that the Early Cretaceous porphyry, skarn and hydrothermal vein type deposits in SGXR belong to a unified metallogenic series and developed a synthetical model for these deposits.

Geology and Genesis of Xianglushan Fe-Cu Orefield in Sichuan (SW China): Evidence from C-O-S-Pb Isotopes

The Proterozoic Xianglushan Fe-Cu orefield (western Sichuan) is located in the Huili–Dongchuan ore belt on the southwestern margin of the Yangtze Block in SW China. The orefield has experienced complex magmatotectonic activities, and hosts a wide variety of Fe oxide-(Cu-Au) deposits. At Xianglushan, the orebodies are made of stratabound magnetite–hematite orebodies superimposed by vein-type chalcopyrite mineralization. The stratabound Fe orebodies are hosted mainly in the Proterozoic volcanic-sedimentary rocks of the lower Yinmin Formation, whilst the Cu vein or stockwork ores were mainly emplaced into the upper part of the footwall volcanic rocks and the lower part of the Fe orebodies. We divided the alteration/mineralization and their fluid inclusions (FIs) into the (I) sodic-calcic alteration, (II) potassic-silicic-sericite alteration and Fe-(Cu) mineralization, and (III) carbonate alteration and Cu mineralization stages. Stage II FIs are mainly two-phase (vapor-liquid), and are featured by medium temperature (348 to 379 °C) and high salinity (21.8 to 22.9 wt % NaCl eqv). Their generally negative calcite δ13C (−4.1‰ to −3.1‰) and δ18OH2O (12.2‰ to 15.3‰) values reveal that the Stage II ore fluids have had a seawater-magmatic fluid mixed source. Late Stage II pyrite has δ34S (−3.3‰ to 13.7‰), 206Pb/204Pb (17.663 to 18.982), 207Pb/204Pb (15.498 to 15.824) and 208Pb/204Pb (37.784 to 38.985), suggesting that the ore-forming materials were derived from dominantly upper crustal source. Stage III FIs are also mainly two-phase (vapor-liquid), and are featured by lower temperature (206 to 267 °C) and salinity (19.0 to 22.5 wt % NaCl eqv) than their Stage II counterparts. The Stage III ore fluids were also likely derived from a meteoric–magmatic mixed source with greater magmatic influence, as indicated by the generally negative calcite δ13C (−6.9‰ to −4.6‰) and δ18OH2O (6.3‰ to 9.2‰) values. Similar to the late Stage II pyrite, the Stage III chalcopyrite δ34S (−4.6‰ to 5.2‰) and Pb isotopes (206Pb/204Pb = 18.198 to 18.987; 207Pb/204Pb = 15.534 to 15.876; and 208Pb/204Pb = 37.685 to 39.476) also suggest a crustal ore-forming material source. Therefore, we suggest that the Fe-(Cu) and Cu mineralization at Xianglushan had similar ore fluid and material sources, although the magmatic influence increased in the later stage. This resembles many Fe-(Cu) deposits in the Huili–Dongchuan ore belt. We conclude that the Xianglushan Fe-Cu deposits are both similar to and different from typical iron-oxide copper gold (IOCG) deposits in terms of alteration styles and hydrothermal mineral assemblages, and are thus best classified as IOCG-like deposits hosted in submarine volcanic-sedimentary rocks. Considering the Mesoproterozoic regional tectonics in the southwestern Yangtze Block, we propose that the Xianglushan ore formation occurred in an intra-/back-arc inversion setting, possibly related to the closure of the Anning ocean basin.

Ore-forming material sources of the Jurassic Cu–Pb–Zn mineralization in the Qin–Hang ore belt, South China: Constraints from S–Pb isotopes

The Qin–Hang ore belt in South China, which serves as the boundary between the Yangtze and Cathaysia blocks, is marked by extensive Jurassic porphyry-skarn-metasomatic Cu–Pb–Zn polymetallic mineralization. In this contribution, S and Pb isotopic compositions of the Baoshan Cu–Pb–Zn deposit in the western portion of the Qin–Hang ore belt were analyzed to determine the ore-forming material sources in the area. This is coupled by the first systematic collection, compilation and interpretation of previously published S and Pb isotopic data of multiple sulfide minerals to reveal the metal origin and accumulation mechanism of the Cu–Pb–Zn mineralization from the significant deposits in the region (i.e., Dexing, Qibaoshan, Shuikoushan, Baoshan, Huangshaping, Tongshanling and Dabaoshan). The results show that Cu mineralization is characterized by low and narrow δ34S (‰) range of values (–5 to 6) and Pb isotopic ratios (208Pb/204Pb = 38.0–39.0, 207Pb/204Pb = 15.4–15.8, and 206Pb/204Pb = 17.7–18.7), which are consistent with those of local porphyries. In contrast, the Pb–Zn mineralization reveals higher and more variable δ34S (‰) values (–4 to 18) and Pb isotopic ratios (208Pb/204Pb = 38.0–39.5, 207Pb/204Pb = 15.3–16.0, and 206Pb/204Pb = 18.0–19.0) that correspond to wall-rock and basement rock compositions in the region. This indicates that the sulfur and lead that formed the Cu mineralization in the Qin–Hang ore belt was mainly sourced from regional magmatism with mantle contributions, whereas the sulfur and lead for the Pb–Zn mineralization was likely derived from the host sedimentary rocks and Proterozoic metamorphic basement rocks, respectively. The S and Pb isotopic data, combined with the geochemical signatures of mineralization-related porphyries, suggest that the Cu was sourced from the deeper levels along with mantle-derived magmas. In contrast, the Pb–Zn probably originated from the crust, with partial melting of the crystalline basement in the Cathaysia Block. Consequently, a three-stage genetic model is proposed to explain the ore-forming processes of the Qin–Hang Cu-polymetallic belt in South China.

In situ sulfur isotope analysis by laser ablation MC-ICPMS and a case study of the Erlihe Zn-Pb ore deposit, Qinling orogenic belt, Central China

Sulfur isotopic composition is useful for tracing sources of ore-forming materials. In situ sulfur isotope analysis by laser ablation coupled with multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICPMS) has an advantage over traditional bulk analysis in tracing sources of sulfur in an ore deposit that has complex mineral types and multiple ore-forming processes. However, in using this method, matrix effects exist widely for sulfides from ore deposits. In this work, matrix effects of different sulfides were examined by matrix-unmatched tests, in which the δ34S values of different types of sulfides were calibrated against a laboratory pyrite standard. The results show that the δ34S values of pyrrhotite, chalcopyrite, molybdenite, sphalerite, and arsenopyrite are in agreement with the reference values, suggesting that the matrix effect was negligible. However, a significant matrix effect occurred in the analyses of Ag2S and galena, leading to significant deviations in δ34S values of up to 1.2‰ and 3.2‰, respectively. The matrix effect occurred not only during the laser ablation stage but also during the transition of ions into the mass spectrometer, resulting in significant space charge effects caused by heavy-mass elements. Thus, pyrite can be used as an external bracketing standard for sulfides that do not have a heavy-mass matrix.Based on our matrix-effect study, the following available external standards were selected for the in situ sulfur isotope analysis of complex-type minerals from the Erlihe Zn-Pb deposit. The coarse-grained sphalerite grains (Sph1) and euhedral to subhedral pyrite grains (Py1) from massive ores have δ34S values ranging from 9.2‰ to 18.1‰. Such heavy sulfur isotopic compositions indicate the derivation of sulfur from the deposits of seawater sulfate, related to a thermochemical reducing process. Fine-grained sphalerite (Sph2) and pyrite (Py2) from vein and disseminated ores coexist with pyrrhotite and chalcopyrite, and have relatively light sulfur isotopic compositions, with δ34S values of about 7‰. The slightly positive δ34S values are similar to those of sulfides from sulfide-rich quartz veins, which contain δ34S values of about 4‰, and granodiorite rocks, with δ34S values of about 6‰. Based on previous studies, the light sulfur of the late-stage sulfides may have resulted from a metamorphic or magmatic hydrothermal event during the Indosinian orogeny. In situ sulfur analysis by LA-MC-ICPMS provides new evidence for sources of sulfur from each stage of mineralization in the Erlihe deposit, suggesting that this is a promising method for studying complex ore deposits.

Petrogenesis of igneous rocks and ore-forming material source of the Nating porphyry Cu (Au) deposit in the western section of the Bangong Co-Nujiang metallogenic belt, Tibet

位于西藏班公湖-怒江成矿带西段多龙矿集区内的拿厅斑岩Cu（Au）矿床是近年来开展勘查取得重大找矿突破的矿床之一，控制Cu资源量已达到大型规模。但目前对该矿床的地质特征、成矿岩石成因及成矿物质来源还缺乏深入的了解和研究。本文基于系统的野外地质观察、岩相学研究，结合精细的锆石SIMS U-Pb定年、锆石Hf-O同位素、岩石地球化学和蚀变-矿石矿物的H-O-S同位素分析，认为该矿床是形成于121~118Ma的斑岩型Cu（Au）矿床，与多龙Cu（Au）矿集区内多不杂、波龙、拿顿、色那、拿若和铁格隆南（荣那）矿床为同一期岩浆-热液成矿事件，其成岩-成矿峰期为120~118Ma。拿厅斑岩铜（金）矿床成矿岩体显示轻稀土富集的分配型式和缺少Eu异常，且富集大离子亲石元素（如Rb、Ba等），而亏损高场强元素（如Nb、Ta等），显示弧岩浆的特征，形成于班公湖-怒江洋向北俯冲的大陆边缘弧背景。锆石Hf-O同位素模拟结果显示，矿区早期的安山-英安质次火山岩（eHf（t）=-2.0~10.3；δ18O=5.07‰~6.77‰）具有早期幔源岩浆和经历MASH过程混入壳源的岩浆（10%~20%壳源物质）的特征；而二长花岗斑岩和成矿花岗闪长斑岩（eHf（t）=1.7~3.3；δ18O=6.40‰~6.95‰）则是MASH过程逐渐演化（壳源-幔源混合，约20%~40%壳源物质）的产物。在形成拿厅斑岩铜金矿成矿岩浆的过程中，没有发生陆壳加厚的过程；岩浆演化过程中有较少斜长石分离结晶，主要为角闪石和钛铁氧化物结晶分异。另外，热液蚀变（石英、磁铁矿）和硫酸盐-硫化物（硬石膏、黄铜矿、黄铁矿）的H-O-S同位素结果显示，拿厅成矿流体和成矿物质主要来源于岩浆，与岩浆流体出溶过程密切有关。

Geochemical characteristics and genetic type of a lithium ore (mineralized) body in the central Yunnan Province, China

ABSTRACT Lithium ore (mineralized) bodies in the area A of central Yunnan Province belong to a sedimentary-type, which are controlled by stratum. The studied ore (mineralized) body mainly occurs in the Middle Permian Liangshan Formation. This work described the morphology, structures, main ore types and geochemical characteristics of this ore body in detail, and discussed the ore-forming material source, occurrence state of lithium and the formation mechanism of lithium ores to clarify the prospecting marks. In the further exploration, comprehensive evaluation of the lithium resources of known bauxite ore bodies in central Yunnan Province should be strengthened, and the exploration of hidden lithium ore bodies should be intensified in order to discover more large and super-large lithium orebodies, which will fill the gap of the national demand for lithium resources, and promote the national defense construction and new energy industry development.

Ore-forming material sources of the Dachayuan uranium deposit, Zhejiang Province: Evidence from C-O and Sr-Nd isotopes

赣杭铀成矿带是我国最大的火山岩型铀成矿带，大茶园（661）铀矿床是该成矿带东段最重要的火山岩型铀矿床，矿体赋存于晚中生代磨石山群九里坪组流纹岩中。为探讨该铀矿床成矿物质来源，对采自大茶园铀矿床中的脉石矿物开展了系统的C-O和Sr-Nd同位素研究。结果表明，成矿流体中矿化剂∑CO2主要来源于地幔，部分来自于基底大理岩或沉积碳酸盐岩碳；成矿期后方解石碳同位素组成靠近基底大理岩或沉积碳酸盐岩组成，可能主要为壳源碳酸盐岩的贡献；成矿期流体中∑CO2以HCO3-为主，CO2去气作用为方解石沉淀形成的主要机制。成矿期不同阶段方解石与萤石的Sr、Nd同位素组成没有明显差别且变化较小，显示矿床中脉石矿物的同源性。通过与基底陈蔡群变质岩和盖层火山岩的Sr、Nd同位素组成对比发现，成矿期萤石与盖层火山岩具有类似的Sr同位素组成，表明大茶园铀矿床成矿物质以壳源为主，主要来自于赋矿火山岩，而Nd同位素进一步表明成矿物质可能来源于赋矿的流纹岩。岩石圈伸展控制着富CO2热液的形成，富CO2热液在上升过程中萃取壳源（尤其是富铀火山岩）中成矿物质，并在有利的成矿部位通过CO2去气作用导致铀沉淀成矿。

Sulfur and lead isotopic variations in the giant Yulong porphyry Cu (Mo[sbnd]Au) deposit from the eastern Tibetan Plateau: Implications for origins of S and Pb, and metal precipitation

The giant Yulong porphyry Cu (MoAu) deposit, located in the eastern Tibetan Plateau, is a typical post-subduction porphyry Cu ± Mo ± Au deposit formed in an intracontinental strike-slip fault system, and it is also one of the largest porphyry Cu deposits in China with reserves of 6.5Mt Cu @ 0.62% and 0.41Mt Mo @ 0.042%, respectively. In this study, sulfur and lead isotopic compositions of sulfides and ore-related porphyry samples were determined to constrain the sources of ore-forming materials and ore-forming process. Sulfides (e.g., pyrite, chalcopyrite and molybdenite) from phyllic alteration zone, where the Cu and Mo mineralization mainly occurred, have uniform δ34S values ranging from −0.6 to +2.1‰ (average + 1.1‰), which indicates a magmatic origin of the sulfur. In situ Nano-SIMS sulfur isotope analysis further reveals that pyrites formed in potassic alteration stage have systematically negative δ34S values ranging from −0.2 to −9.7‰ (average − 4.5‰), whereas pyrites formed in phyllic alteration stage have systematically positive δ34S values ranging from +1.1 to +3.2‰ (average + 2.1‰). This regular variation is considered to be resulted from disproportionation of aqueous SO2 and subsequent sulfate reduction, further suggesting a magmatic origin of the sulfur. The sulfides have initial Pb isotopic compositions ((206Pb/204Pb)i = 18.616–18.812, (207Pb/204Pb)i = 15.670–15.740, (208Pb/204Pb)i = 38.956–39.080) deviating from those of the ore-related porphyries ((206Pb/204Pb)i = 18.549–18.718, (207Pb/204Pb)i = 15.647–15.662, (208Pb/204Pb)i = 38.794–39.888), but more close to those of the ore-hosting strata ((206Pb/204Pb)i = 18.423–18.761, (207Pb/204Pb)i = 15.654–15.713, (208Pb/204Pb)i = 38.867–39.062). The shift of Pb isotopic compositions of sulfide minerals toward those of ore-hosting strata indicates that the ore-hosting strata had provided a significant amount of Pb for ore formation, and most probably suggests fluid-rock interaction processes in the hydrothermal system. Our study represents a case study in which ore-hosting strata had provided a significant amount of ore-forming materials for porphyry Cu ± Mo ± Au formation in the post-subduction setting.

Genesis of the Dongguashan skarn Cu-(Au) deposit in Tongling, Eastern China: Evidence from fluid inclusions and H-O-S-Pb isotopes

The Dongguashan copper-(gold) deposit is located in the Eastern Tongling ore district of the Middle-Lower Yangtze River Valley Metallogenic Belt (MLYRB), Eastern China. The Cu-(Au) mineralization is associated with the Qingshanjiao quartz monzodiorite and consists of various types including stratiform, porphyry, vein-like and skarn. There are three deposit models, including: 1) stratabound skarn-type; 2) exhalative sedimentary (SEDEX)-hydrothermal superimposition-type; and 3) exhalative sedimentary (SEDEX) type. The ore-forming processes can be divided into the prograde skarn alteration (Stage I), retrograde alteration (Stage II) and quartz-carbonate alteration (Stage III). Four types of fluid inclusions (FIs) are recognized at Dongguashan: Vapor-rich two-phase aqueous (Type I), liquid-rich two-phase aqueous (Type II), daughter-mineral-bearing three-phase (homogenized to liquid by the disappearance of vapor phase; Type III), and daughter-mineral-bearing three-phase (homogenized to liquid by the disappearance of daughter minerals; Type IV). All four types of FIs are present in Stage II. Stage I does not contain Type IV FIs, and only Type II FIs are found in Stage III. For Stage I, Type I, II and III FIs homogenized at 379–548 °C, 319–522 °C and 450–512 °C, respectively, with salinities of 10.1–19.6, 5.9–19.4 and 36.7–43.3 wt% NaCl equivalent. For Stage II, Type I, II, III and IV FIs homogenized at 286–378 °C, 235–372 °C, 265–349 °C and 324–350 °C, respectively, with salinities of 1.4–17.0, 4.3–16.1, 34.7–40.6 and 34.4–41.0 wt% NaCl equivalent. The Type I to III FIs in Stage I and II have similar homogenization temperatures but different salinities, which indicates the occurrence of fluid immiscibility. Hydrogen-oxygen isotopes of the quartz (δD = −84.0 to −71.5‰, δ18OH2O = +4.51 to +8.97‰) and calcite (δD = −70.7 to −60.95‰, δ18OH2O = +4.41 to +4.91‰) suggest that the ore-forming fluids were principally magmatic-derived. δ34S values of the stratiform orebodies (+4.1 to +5.3‰), vein-like orebodies (+4.2 to +5.7‰), skarn orebodies (+4.9‰), porphyry orebodies (+5.1 to +5.7‰) and the Qingshanjiao pluton (−2.2 to +5.2‰) are different from those of the wall rocks (−29.5 to −4.6‰), suggesting that wall rocks were unlikely to be a major sulfur source. Lead isotopes of the sulfides from the different orebody types are similar to those of the plagioclase from the Mesozoic intermediate-felsic rocks in the MLYRB, suggesting that they have had similar Pb source. Sulfur and lead isotopes suggest that the ore-forming materials were derived from a deep-seated magmatic source. The ore-forming fluid immiscibility during Stage I and II may have altered the physicochemical conditions of the hydrothermal fluid system, leading to the Cu-(Au) sulfide precipitation. Based on the ore geological and alteration/mineralization features, mineral assemblages, ore-forming material source and fluid evolution, we consider that Dongguashan is best classified as a porphyry–skarn Cu-(Au) deposit.