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The Luziyuan skarn deposit is the second largest Pb − Zn deposit in the Baoshan block, Yunnan Province, Southwestern China. Rhodonite is a widespread skarn mineral in the host rock, occurring as coarse-grained crystals and veins, and is closely associated with Pb − Zn mineralization. In-situ elemental analysis of rhodonite from three levels (1220 m, 1265 m and 1495 m above sea level) by laser ablation-inductively coupled plasma-mass spectrometry and Sm − Nd isotopic dating of the rhodonite − calcite pair were conducted to constrain the compositions and the timing of Pb − Zn mineralization. The new Sm − Nd isotopic data reveal that the Luziyuan deposit formed during the Early Jurassic (183 ± 2.3 Ma; MSWD = 0.72). These chronological constraints, combined with regional tectonic evolution, suggest that the Luziyuan Pb − Zn mineralization is genetically linked to eastward subduction of the Shan Boundary Ocean beneath the Baoshan block during the Meso-Tethys period. Furthermore, all examined rhodonite samples contain relatively high concentrations of MnO (34.7 − 43.0 wt%) and Zn (536 − 2117 ppm), but generally low contents of FeO (1.07 − 6.08 wt%), Cu, Co, Ni, Ga, Mo, Sn, W and Pb. A positive correlation between Zn and MnO contents among different skarn deposits and nearly chondritic Y/Ho ratio (~ 28) in the Luziyuan rhodonite suggests that this mineral formed from magmatic fluids and its Zn enrichment was controlled by the fluid chemistry. The same data also suggest that Zn-rich rhodonite in skarns may be used as an indicator mineral for Zn exploration when combined with other geological, geophysical, and geochemical criteria. [ABSTRACT FROM AUTHOR]

The western Hunan–eastern Guizhou Zn‐Pb metallogenic belt is one of the important Zn‐Pb mineralization regions in China. The Dadongla deposit, located in the northeast of Guizhou Province, is one of the typical Zn‐Pb deposits in the region and has estimated resources more than 12 million metric tons (Mt) with an average grade of 4.11 wt% Zn+Pb. Its orebodies are hosted in the lower Cambrian Aoxi Formation dolomite, occurring as bedded, para‐bedded in shape, and in conformity with the wall rock. The ore mineral assemblage is simple, dominated by sphalerite with minor pyrite and galena, and the gangue minerals are composed of dolomite, calcite with minor bitumen and barite. In view of the lack of geological and geochemical researches, the genesis of Zn‐Pb ore is still unclear. Laser ablation‐inductively coupled plasma mass spectrometry (LA‐ICPMS) spot and mapping analyses were used to obtain sphalerite trace element chemistry in the Dadongla Zn‐Pb deposit in Guizhou, China, aiming to constrain its ore genesis. The results show that sphalerite is characterized by the enrichment of Cd, Fe, Ge and Hg, corresponding with that of typical MVT deposits. Four zones were identified in the sphalerite crystal from Dadongla from the center to margin according to the color bands, in which the zone in the center, representing the early ore‐stage sphalerite, is characterized by enrichment of Cd relatively, while the zone forming at late ore‐stage is enriched in Ge and Hg relatively. The finding was controlled by differential leached metals content in ore‐forming fluid from its source rock. Notably, critical element Ge trends to be enriched at the late ore‐stage and follows a substitution of 2Zn2+↔ Ge4++□ (vacancy). Moreover, the calculated ore‐forming temperature ranges from 79.9°C to 177.6°C by the empirical formula, which is similar to that of typical Mississippi Valley‐type (MVT) deposits. Compared with the features of trace elements in sphalerite from different types of deposits, together with the geology, the Dadongla deposit belongs to an MVT Zn‐Pb deposit. [ABSTRACT FROM AUTHOR]

The Sichuan–Yunnan–Guizhou (SYG) Pb–Zn metallogenic province is one of the most productive areas of Pb–Zn resources in China. The Fule deposit occurs in Permian carbonate and contains Pb–Zn reserves exceeding 1 Mt. To investigate the sulphur source, in situ S isotopic analysis of sphalerite and pyrite was carried out using nanoscale secondary-ion mass spectrometry. The results show that the δ34S values of the sulphide minerals range from +16.1‰ to +23.0‰, higher than that of marine sulphates hosted in Permian carbonate rocks (+11‰), but similar to that of sulphates over a broader area (+12.9‰ to +25.9‰). The sulphates in the regional rocks could therefore represent an important source of S for the Fule deposit via thermochemical sulphate reduction. The S source of the Fule deposit is different from those of most other Pb–Zn deposits in the SYG Pb–Zn mineralization province, which were mainly derived from the ore-bearing strata. The δ34S values of the early to late generations and some single sulphide crystals from the cores to rims show a slight increasing trend, implying that partial Rayleigh fractionation took place in the Fule deposit. It is suggested that the Fule sulphide precipitation resulted from the mixing of a metalliferous fluid with a H2S-rich fluid derived from the regional strata. Combining the geology, mineralogy and S isotope results with previous Pb isotope studies, it is suggested that the Fule deposit should be attributed to a Mississippi Valley type deposit. [ABSTRACT FROM AUTHOR]

[Display omitted] • REE and metals were transported predominantly as chloride complexes. • H 2 S was sourced from TSR of the evaporite sulfate in ore-hosting strata. • Metals were derived from a mixed source of basement and country rocks. • Fluid mixing between two fluids lead to sulfides precipitation. • The Pb-Zn deposits at Huayuan belong to MVT formed in a foreland basin. The Xiangxi-Qiandong metallogenic belt (>300 Mt sulfide ores @∼4.0 wt% Pb + Zn), located at the southeastern margin of the Yangtze Block, is one of the important Pb-Zn producers in China. Although carbonate-hosted Pb-Zn deposits in this district have attracted great attention during past decades, many issues, particularly the ore genesis and geodynamic setting, remain unclear. In this study, we take the Limei and Yutang deposits as typical case studies, using detailed geology, rare earth elements and yttrium (REY) geochemistry of fluorite and sulfides in situ S-Pb isotopes, to propose a new model for early Cambrian reef limestone-hosted Pb-Zn deposits in the district. REY contents (0.47 to 8.67 ppm; mean = 3.99 ppm) in fluorite from Limei and Yutang slightly deplete in LREE and HREE relative to MREE, indicating that the REEs and metals were transported predominantly as chloride complexes in a low-temperature (<200 °C) hydrothermal fluid with high saline. New δ 34S values of sulfides (+27.66 to + 35.46‰ in Limei and + 24.80 to + 36.07‰ in Yutang) imply that S2- was originated from evaporite sulfate within ore-hosting strata via thermo-chemical reduction (TSR) as the presence of reducing agents (bioclastic limestone and organic matter). In situ δ 34S values show a slightly large range (variation up to 11.27‰) and vary significantly within single grain (up to 4.60‰), which may be inherited from the S composition of H 2 S in the original fluid. In situ Pb isotopic ratios of sulfides from Limei (206Pb/204Pb = 18.001–18.269, 207Pb/204Pb = 15.645–15.796 and 208Pb/204Pb = 38.243–38.597) and Yutang (206Pb/204Pb = 18.135–18.384, 207Pb/204Pb = 15.714–15.924 and 208Pb/204Pb = 38.347–38.874) positively correlates in Pb-Pb diagrams, indicating the mineralizing metals are mainly derived from Proterozoic basement rocks with an amount of contribution from early Cambrian sedimentary rocks. Mineralogy, fluorite REY geochemistry and sulfides in situ S-Pb isotopes together with previously reported mineralization ages suggest that the mixing of metal-rich fluid from basement rocks and the H 2 S-rich fluid originated from ore-hosting strata plays an important role in forming the Pb-Zn deposits of Limei and Yutang. This study provides a typical example for better understanding the genesis and geodynamic setting of MVT deposits in the foreland basin, South China. [ABSTRACT FROM AUTHOR]

Zoning texture in sphalerite has been described in many studies, although its genesis and ore formation process are poorly constrained. In this investigation, we compare the in situ trace element and isotopic composition of colour-zoned sphalerites from Nayongzhi, South China, to explain the zoning growth process. Petrographic observations identified two broad types of zoned sphalerite, core–rim (CR) and core–mantle–rim (CMR) textures. Each zoned sphalerite displays two or three colour zones, including brown core, light colour bands and/or pale-yellow zones. In situ laser ablation inductively coupled plasma mass spectrometry trace-element analyses show that the three colour zones display variable trace-element compositions. Brown cores exhibit distinctly high Mn, Fe, Co, Ge, Tl and Pb concentrations, whereas pale-yellow and light colour zones have elevated Ga, Cd, Sn, In and Sb concentrations. Copper, Sb, In and Sn show slight variations between pale-yellow and light zones, the latter having higher In and Sn, but lower Cu and Sb abundances. Given the low concentration range of Pb, Ge, Tl, Mn Sb, Cd, etc., the colour of sphalerite is attributed mainly to Fe compositional variation. The δ34S values of sphalerite from Nayongzhi range from +22.3 to +27.9‰, suggesting reduced sulfur was generated by thermochemical sulfate reduction of marine sulfate in ore-hosted strata. Single-crystal colour-zoned sphalerite exhibits intracrystalline δ34S variation (up to 4.3‰), which is attributed to the δ34S composition of H2S in the original fluid. The lack of correlation between trace elements and δ34S values indicates episodic ore solution influxes and mixes with the reduced sulfur-rich fluid derived from the aquifers of the ore-hosted strata, which play a key role in the formation of the zoned Nayongzhi sphalerite. In conclusion, in situ trace element and S isotope studies of zoned sphalerite crystals might provide insight into the ore-forming process of MVT deposits. [ABSTRACT FROM AUTHOR]

• Zn-bearing sulfides at Maoping formed under a median-low temperature (<250 °C) condition. • Several trace elements partitioning in sphalerite–galena at temperature below 250 °C hydrothermal system was identified. • Trace elements variation in sphalerite may be mainly controlled by host rock composition. • Trace elements in sphalerite suggest the Maoping deposit belongs to an MVT deposit. The Sichuan-Yunnan-Guizhou metallogenic province (SYGMP) contains over 400 different size Zn-Pb deposits hosted in late Ediacaran to early Permian carbonate sequences and accounts for approximately 27% of the total Zn-Pb production in China. The Maoping deposit is a typical example that is not only mainly hosted in two different strata i.e., Devonian Zaige Formation (Fm.) and Carboniferous Baizuo Fm. but also shows a close spatial relationship with the Emeishan flood basalt. However, its ore genesis is poorly constrained. In this study, LA-ICP-MS trace element maps and spot analyses were generated on the sphalerite and galena selected from Maoping, aiming to establish tarce element partitioning behavior in co-crystallized sphalerite–galena, constrain the possible controls on the variation of trace element, and provide new insights into the ore genesis. The results show that Mn, Cd, Fe, Ge, Cu, In and Sn concentrations in sphalerite are higher than coexisting galena, yet galena is the preferential host for As, Ag, Sb, Tl, and Bi. The sphalerite from Carboniferous Baizuo Fm. is more concentrated in Cu, Ge, As, Ag and Sb than that of Devonian Zaige Fm., but has comparable trace element compositions to many other SYGMP Zn-Pb deposits hosted within the same sediment strata such as Huize and Tianqiao. This difference may be thought to have been controlled by host rock chemical composition with limited effect by physicochemical conditions and/or source(s) of metal elements. Sphalerite from the Maoping deposit is characterized by enrichments in Cd, Ge but depletions in Mn, Fe, In and Co, which are markedly distinct from that of the magma-related hydrothermal system (e.g., high-temperature (high- T) magmatic-hydrothermal, VMS and skarn deposits) but consistent with that of MVT deposits. Based on these results, together with the geological and geochemical features of the deposit, we considered that the Maoping Zn-Pb deposit belong to a MVT deposit. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reduced sulfur for the formation of the Liangyan deposit was derived from thermochemical sulfate reduction of sulfates. • The sulfates were mainly from Carboniferous ore-hosting rocks and partially from Ediacaran-Devonian sedimentary rocks. • Mixing of isotopically distinct sources caused the variable Zn-Cd isotopes of sphalerite. • Basement rocks and Carboniferous wallrocks were the sources of Zn and Cd in sphalerite. • The Liangyan deposit is best classified as a thrust-fault controlled MVT Zn-Pb deposit. Unraveling the metal sources of Zn-Pb deposits is vital to understand the genetic types and ore-forming processes. The Sichuan-Yunnan-Guizhou metallogenic province (SYGMP) hosts abundant Zn-Pb deposits that are variably rich in critical metals such as Ga, Ge, Cd and Tl. However, sources of these critical metals and main metal Zn are still unclear. The Liangyan Cd-rich Zn-Pb deposit as a representative in the SYGMP is hosted in a carbonate sedimentary sequence and controlled by the regional Yadu-Wogong anticline and Yadu-Mangdong thrust fault. S-Zn-Cd isotopes of sulfide minerals from this deposit are obtained in order to understand the sources of metals and origin of the deposit. Sulfur isotopic results of pyrite and sphalerite reveal that sulfur was produced by thermochemical sulfate reduction (TSR) of sulfates from the Carboniferous dolostone and mudstone and the Ediacaran-Devonian carbonates. Sphalerite grains have δ66Zn JMC values that are negatively correlated with the δ114Cd spex values, implying different sources for both Zn and Cd. The variation trend of δ66Zn JMC and Cd/Zn suggests that Zn was mainly sourced from the Neoproterozoic basement with minor from the Carboniferous wallrocks. Besides, sphalerite grains show a negative correlation between δ114Cd spex and Zn/Cd, and these values fall in the field close to the Carboniferous carbonates, but away from the Permian Emeishan basalts, indicating that Cd was derived mainly from the Carboniferous wallrocks with minor from the Emeishan basalts. Together with geological evidence, the multi-isotope data suggest that the Liangyan deposit belongs to a thrust-controlled MVT Zn-Pb deposit. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Zhugongtang deposit belongs to MVT deposits formed in an orogenic thrust belt. • Ores were deposited from low-temperature, low f O 2 and weakly acidic basinal brine. • H 2 S was sourced from synchronous seawater sulfates in ore-hosting sedimentary rocks. • Metals were derived from a mixed source of basement and country rocks. • Sulfide precipitation was triggered by mixing between two different fluids. The Sichuan-Yunan-Guizhou triangle region contains numerous economically important carbonate-hosted Zn-Pb deposits that occur in the Late Indosinian thrust and fold system rather than foreland basin. In this paper, we investigate the thrust-controlled Zhugongtang deposit (>30.0 Mt ores @ 6.76 wt% Zn and 2.27 wt% Pb) as a case study, using ore deposit geology, in-situ trace elements and isotopes in sulfides, to provide new insights into the ore genesis of the MVT deposits in the thrust belts. The sulfide orebody is structurally controlled by a kilometer-scale thrust system and occurs as open-space fillings, vein or replacement structures. Trace elements in pyrite show a low concentration of Co, Ni, Tl and Se, suggesting that the sulfides were formed under low-temperature (100–250 °C) and slightly reduced conditions. The δ13C PDB values (−7.53 to +1.73‰) in calcite lie between the marine carbonate rocks and sedimentary organic matter, and the calculated δ18O fluid values (+3.40 to +13.36‰) are different from that of marine carbonate rocks but partly overlap with the basinal brines. Such C-O isotope signature indicates that the carbon was mainly derived from the host rocks (limestone) with additional contribution from organic carbon. The oxygen isotope values suggest mixing of the basinal brine and the limestone. The δ34S values of sulfides within Permian strata (+12.2 to +15.3‰) and Devonian strata (+18.5 to +23.8‰) are similar to the coeval seawater sulfate within the ore-hosting strata, respectively. This indicates that the reduced sulfur is originated from evaporative sulfate within host rocks by thermo-chemical reduction in the near-close system. In-situ Pb isotopic ratios of galena (206Pb/204Pb = 18.566–18.758, 207Pb/204Pb = 15.757–15.769 and 208Pb/204Pb = 39.061–39.366) are comparable with the Proterozoic basement and the country rocks, indicating the mineralizing metals were mainly derived from basement rocks and partly extracted from country rocks via fluid-rock interaction. Regional geological evidence indicates the timing of Zn-Pb mineralization of Zhugongtang is Late Triassic to Early Jurassic and related to the Indosinian orogeny. Overall, the newly obtained trace element and isotopic data together with geological evidence suggest that the Zhugongtang deposit is an MVT deposit formed in the orogenic thrust belt and that fluid mixing was critical for the ore formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Maoping carbonate-hosted Pb-Zn deposit in SW China is best classified as MVT. • Sphalerite Pb-Zn-Cd isotopes suggest mixing of metal-bearing and reduced S-bearing fluid. • Ore lead was mainly sourced from the Devonian ore-bearing carbonate sequence. • Ore zinc was mainly sourced from the Neoproterozoic metamorphic basement. The Maoping carbonate-hosted Pb-Zn deposit (25 Mt ores @ 12–35% Zn + Pb) is a representative and the third-largest Pb-Zn deposit in the Sichuan-Yunnan-Guizhou Pb-Zn metallogenic province (SYGMP). In this study, Pb-Zn-Cd isotope analyses were performed on sphalerite from Maoping, in order to understand the ore metal source and metallogenesis in the SYGMP. The sphalerite samples have narrow ranges of Pb isotope ratios: 206Pb/204Pb = 18.675–18.751, 207Pb/204Pb = 15.758–15.768, and 208Pb/204Pb = 39.287–38.436. This implies thorough mixing of two Pb sources, which we interpreted to be the Devonian-Carboniferous ore-hosting carbonate wallrocks and the Neoproterozoic Kunyang/Huili Group (Gp.) clastic and metamorphic rocks. The Maoping sphalerite samples have uniform δ66Zn (−80.07 to + 0.25‰) and δ114Cd (−0.10 to + 0.27‰) values, which further support complete source mixing. In the δ66Zn vs. Cd/Zn plot, the Maoping sphalerite data fall close to the field of basement rocks and distal to the carbonate wallrocks, indicating that the ore zinc was mainly derived from the metamorphic basement with heavier δ66Zn values and low Cd/Zn ratios with certain contributions from the minor carbonate wallrock with lower δ66Zn values and high Cd/Zn ratios. In the δ114Cd vs. 1/Cd plot, all Maoping sphalerite samples fall inside the Mississippi Valley-type (MVT) field, and the deposit shares many geological and sulfide geochemical (incl. isotopic) features with MVT deposits. Thus, the Maoping Pb-Zn mineralization is best classified as MVT, and the sulfide precipitation in structural (fault-fold) traps was caused by binary mixing of a metal-bearing and a reduced S-bearing fluid. [ABSTRACT FROM AUTHOR]