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... The contiguous Sichuan-Yunnan-Guizhou Pb-Zn metallogenic triangle area (SYGT) (Figure 1(a)), located in the southwestern margin of the Yangtze Block in China, is an important part of the South China low-temperature metallogenic domain [1][2][3][4]. There are more than 440 carbonatehosted Pb-Zn deposits distributed in the SYGT and the metal resources exceed 26 million tons, which makes SYGT the largest Pb-Zn mining area and the area with the highest metallogenic potential in China [5]. ...
The Laoyingqing Pb–Zn deposit is located on the southwestern margin of the Yangtze block and on the east side of the Xiaojiang deep fault in the Sichuan–Yunnan–Guizhou Pb–Zn metallogenic triangle area (SYGT). This deposit was first discovered in the silty and carbonaceous slate of the Middle Proterozoic Kunyang Group that is structurally controlled by thrust faults and anticlines. This study is aimed at investigating whether the Laoyingqing deposit has the same ore-forming age and type as other Pb–Zn deposits related to the Pb–Zn metallogenic system and prospecting prediction of the deep and peripheral areas of the deposits in the SYGT. Based on the sphalerite Rb–Sr age dating and S–Sr–Pb isotopic composition analysis of the Laoyingqing Pb–Zn deposit, the following results were obtained. First, the Rb–Sr isochron age of sphalerite is 209.8±5.2 million years (Ma), consistent with the ages of most Pb–Zn deposits in the SYGT (approximately 200Ma), thereby potentially indicating that these Pb–Zn deposits may have been formed synchronously during the late Indosinian orogeny. Second, the Pb isotopic compositions of sulfides show a linear trend on the average crustal Pb evolution curve in ²⁰⁷Pb/²⁰⁴Pb vs. ²⁰⁶Pb/²⁰⁴Pb plot. In addition, Pb isotopic ratios were consistent with the age-corrected Pb isotopic ratios of basement rocks, consequently suggesting that the source of mixed crustal Pb is mainly derived from basement rocks. Combined with the initial ⁸⁷Sr/⁸⁶Sr ratios of sphalerite between the (⁸⁷Sr/⁸⁶Sr)200Ma value of the basement rocks and that of the Upper Sinian–Permian carbonates, it can be concluded that the ore-forming metals were mainly derived from basement rocks. Third, sulfur isotopic composition of sphalerite from the Laoyingqing deposits shows δ³⁴SCDT values that range mainly from -2.62‰ to 1.42‰, which is evidently lower than the δ³⁴SCDT values of sulfides (8–20‰) from other Pb–Zn deposits in the SYGT. This can be interpreted as a result of mixing with reduced S that was mainly derived from the thermochemically reduced S in the overlying strata and a small amount of reduced S produced by the pyrolysis of S-containing organic matter. We conclude that the Laoyingqing deposit and most of the Pb–Zn deposits in the SYGT are Mississippi Valley-type deposits, thereby providing new ideas for investigating the deep and peripheral areas of Pb–Zn deposits.
... Gold, As, Sb and Ag are the main ore-forming elements found within the low-temperature mineralisation. The conditions of low-temperature mineralisation have been defined differently by several authors, but temperatures are typically agreed to be 150-250 • C (Roedder, 1984;Li, 1999;Hu et al., 2016). Other temperature classifications are considered arbitrary, and there is a continuum between medium-low temperature and high-low temperature metamorphism. ...
Chalcophile elements hosted by black shales of the Lower Cambrian Niutitang Formation, South China Block, contribute to low-temperature mineralisation in southwest China. To study the mobilisation and migration of ore-forming elements, hydrothermal experiments were performed to simulate leaching of Au, As, Sb and Ag from an Au-rich black shale from the Kaiyang Phosphate Mine (KYPM), China. The experiments were designed to simulate low-temperature mineralisation at 150 °C, with solvent concentrations of ∼5%, durations of 15 d and 30 d, and water/rock mass ratios of 13:1 and 26:1. Reagent-grade NaCl, NaHCO3 and Na2S were used to provide the common anions found in hydrothermal systems. The results show that solutions containing Cl⁻ ions in oxidised acidic systems leached Au most effectively. Weakly alkaline systems containing HCO3⁻ ions leached Au less effectively. Solutions containing HS⁻ ions did not leach Au effectively, and Au precipitated within the HS⁻-bearing system. The results for Ag were similar to those for Au, and Ag-leaching was most effective in the oxidised acidic system containing Cl⁻ ions. As-leaching does not occur in the Cl⁻-bearing system, but As is leached effectively by HS⁻-bearing and HCO3⁻-bearing solutions. Sb was not leached by our experiments. Oxidised fluids produced by deep-sourced magma during the Indosinian and Yanshanian tectonic events infiltrated black shales affected by extensional deformation through faults, joints and fractures. Fluid–rock interaction leached a range of elements in these structural settings. These experiments provide insights into migration of chalcophile elements, particularly Au and Ag, and the source of large-scale low-temperature mineralisation within the South China Block.
... Metallogenic domains are defined as huge regions that contain a large number of ore deposits. An extremely important group of low-temperature (generally below 200-250°C), hydrothermal deposits, has been termed the South China low-temperature metallogenic domain (LTMD; Tu, 1998Tu, , 2002Li, 1999). This domain extends over an area of $500,000 km 2 in the southwestern part of the Yangtze Block and includes world-class Carlin-type gold deposits, vein-type Sb, Hg and As deposits and Mississippi Valley-type (MVT) Pb-Zn deposits Su et al., 2008Su et al., , 2009aSu et al., , 2009bSu et al., , 2012Hu and Zhou, 2012;Peng et al., 2003b;Zhou et al., 2001;Zhou et al., 2013aZhou et al., , 2013bZhou et al., , 2013c; J.X. Zhou et al., 2015;Chen et al., 2015). ...
The South China Craton was formed by amalgamation of the Yangtze and Cathaysia Blocks during the Neoproterozoic. During the Mesozoic, voluminous granitic plutons and associated W-Sn polymetallic deposits were formed in the Cathaysia Block. The giant South China low-temperature metallogenic domain (LTMD) includes an area of ∼500,000 km² in the Yangtze Block and is composed of the Chuan-Dian-Qian Pb-Zn, Youjiang Au-As-Sb-Hg and Xiangzhong Sb-Au metallogenic provinces. The Chuan-Dian-Qian Pb-Zn province contains numerous MVT Pb-Zn deposits, whereas the other two provinces are characterized by Carlin-type Au deposits and vein-type Sb, Hg and As deposits. These epigenetic deposits, which formed under low temperature conditions (∼100-250°C), are typically hosted in sedimentary rocks and are locally controlled by faults and fractures. The deposits formed dominantly at 200-230 Ma and 130-160 Ma, corresponding to Indosinian (Triassic) and Yanshanian (Jurassic to Cretaceous) orogenies, respectively. Indosinian mineralization is recognized in all three provinces, but Yanshanian mineralization occurred only in the Youjiang and Xiangzhong provinces. The Indosinian orogeny, which involved collision of the Indochina Block with the South China Craton, resulted in circulation of basinal brines that leached ore-forming elements from adjacent sedimentary strata to form the Chuan-Dian-Qian Pb-Zn province. Deep-seated granitic magmas generated during this orogeny caused extensive circulation of meteoric water that mobilized ore-forming elements from the sedimentary strata to form the Carlin-type Au deposits in the Youjiang province, and the Sb-Au deposits in the Xiangzhong province. The Indosinian orogeny was the key factor in establishing the metallogenic framework of the LTMD. It produced widespread mineralization in the three metallogenic provinces, each of which has unique features reflecting differences in the nature and composition of the basement rocks. The Yanshanian metallogeny was less important and overprinted the older ore deposits in the Youjiang and Xiangzhong provinces.
... Except for the higher Ca 2+ and Mg 2+ contents, which may be related to the later carbonation stage, the composition of the ore fluid is similar to oil-field brine. Increasing amounts of data indicate that there are close relationships between lowtemperature Pb–Zn deposits and nearby petroleum paleoreservoirs (e.g., Li 1999). For example, the mineralizing fluid of the Laisvall Pb–Zn deposit, Sweden, is rich in hydrocarbons (Rickard et al. 1975). ...
Laser-ablation ICP mass-spectroscopy has been used to investigate the geochemistry of sphalerite in a range of nine Zn–Pb deposits in South China. The deposits, which are of different ages and belong to different metallogenic provinces, have been assigned to the following genetic types: skarn (Hetaoping, Luziyuan), syngenetic massive sulphide (Dabaoshan, Laochang and Bainiuchang) and Mississippi-Valley-type (Huize, Mengxing, Niujiaotang) based on the features of the ore, even though their origin is heavily debated based on other criteria. The giant Jinding deposit is considered separately. Sphalerite from each genetic class of deposit shows a distinct chemical signature. Sphalerite from the skarn deposits is characterised by elevated, lattice-bound concentrations of Co and Mn. The distal character of these skarn systems is reflected by the low In content of sphalerite. The three syngenetic massive sulphide deposits feature sphalerite strongly enriched in In, Sn and Ga, whereas the deposits of MVT-type are typically enriched in Ge, Cd, Tl and As. These divergent characters are reflected in absolute element abundances as well as in element ratios.Time-resolved depth profiles for sphalerite from the Chinese deposits confirm the presence of elements such as Co, In, Ge, Ga, and Cd in solid solution, but the dataset expands the understanding of sphalerite mineral chemistry by also indicating that other elements, whose ability to enter the crystal structure of sphalerite has been previously debated (Ag, Sn, Tl, Sb), may also be in solid solution.Sphalerite is a refractory mineral and trace element analysis of sphalerite shows promise as a tracer of ore genesis even in overprinted ores. Systematic work on larger sample suites may help define the geochemical signature of different metallogenic epochs in regions as geologically complex as South China and help resolve the mechanism by which many of the debated ore deposits were formed.
The Baidi Au-Sb deposit, which contains 8 t of Au and 10,979 Mt of Sb, is a typical and rare paragenetic deposit located in southwestern Guizhou Province, China. Previous studies have focused on individual ores, but have not combined them to identify their paragenetic mechanism or metallogenic regularity. Therefore, we used field investigations, microscopic observations, and in situ analyses to identify the spatial distribution, mineral paragenesis, compositional evolution, and metallogenic material sources of the ore bodies. We also determined the Au and Sb paragenetic characteristics and the metallogenesis of the deposit. The main Au-bearing minerals in the deposit were early (Apy1–2) and late (Apy3) stage arsenopyrites, as well as pre-mineralization (Py1), mineralization (Py2–5), and late mineralization (Py6–7) stage pyrites. The main Sb-bearing minerals were stibnite (Snt), skinnerite, bournonite, and valentinite. The minerals formed in the order of Py1, Py2–3 + Apy1, Py4–5 + Apy2, Snt, and Py6–7 + Apy3. The δ34S values of the arsenopyrites and pyrites ranged from − 5 to 5‰, while those of stibnite were mostly less than − 5‰ in the later mineralization stages. Sulfur was provided by deep magmatic hydrothermal fluids, but sedimentary sulfur was added in the later stages. Moreover, the trace elemental contents fluctuated and eventually became similar to those of the sedimentary strata. By comprehensively considering the ores along with the geological characteristics of the deposit, we determined that deep magma provided the Au during ore formation. Later tectonic changes provided Sb from the sedimentary strata, which precipitated along fault expansion areas and produced Au and Sb paragenesis.
In this paper, we determined the 3-D P-wave velocity structure beneath the South China block by applying arrival times from 269 teleseismic events recorded by 240 seismic stations in our study region. Our tomography results reveal deep structural characteristics of the major tectonic units and ore-concentration areas. There are obvious high velocity anomalies beneath the ancient Yangtze block and the Cathaysia block, and the lithosphere of the Cathaysia block is thinner than that of the Yangtze block; the Jiangnan orogenic belt located in the combined zone of two blocks is a high and low velocity anomaly conversion zone; The famous metallogenic belts of Edongnan, Youjiang Basin and cathaysia block are obviously low-velocity areas with different metallogenic mechanisms. The deep ore-forming materials source in Edongnan metallogenic belt is different from that of cathaysia block. The low-velocity anomaly under the Cathaysia block related to mineralization is the upwelling of mantle material caused by the joint action of Paleotethian tectonic domain, the Paleo-Pacific tectonic domain and the Hainan mantle plume migration and erosion from northeast to southwest since 80 Ma.The low-temperature mineralization mechanism of youjiang Basin should be considered not only from the influence of the Emeishan mantle plume in the west and the Paleotethian tectonic domain in the south, but also from the influence of the upwelling of asthenosphere material Paleo-Pacific tectonic domain in the east.
Over 400 carbonate-hosted Pb-Zn deposits in the western Yangtze block constitute the giant Sichuan-Yunnan-Guizhou (SYG) Pb-Zn metallogenic province. The majority of Pb-Zn deposits hosted in Devonian carbonates are characterized by low δ³⁴S values, causing debates on their ore genesis. To address this issue, the Yunluheba Pb-Zn deposit is chosen as a case study. Ore bodies of this deposit are hosted in middle Devonian carbonates. Ore minerals are sphalerite, galena and pyrite. Sphalerite Rb-Sr dating yields an isochron age of 206.2 ± 4.9 Ma, consistent with ages of most Pb-Zn deposits in the SYG province, arguing for a regional intensive Pb-Zn mineralization event during the late Indosinian orogeny. Sulfides have Pb isotopic compositions that form a linear trend above the average crustal Pb growth curve in the ²⁰⁷Pb/²⁰⁴Pb vs. ²⁰⁶Pb/²⁰⁴Pb plot. Moreover, Pb isotopic ratios are consistent with the Devonian to Permian carbonates’ age-corrected Pb isotopic ratios, suggesting mixed crustal Pb sources with the majority of Pb derived from country rocks. Combined with initial ⁸⁷Sr/⁸⁶Sr ratios of sphalerite, approximately equal to ⁸⁷Sr/⁸⁶Sr200Ma ratios of the D-P carbonates, ore-forming metals are considered to have been derived mainly from ore-hosting rocks. Sulfides’ δ³⁴SCDT values range mainly from −2.0‰ to 2.9‰, interpreted to be a result of mixing by syn-sedimentary pyrite originated biogenic S and thermochemically reduced S. We conclude that the Yunluheba deposit and other Pb-Zn deposits in the SYG province should belong to Mississippi Valley-type deposits.
Currently, China has achieved a breakthrough in the Lower Silurian Longmaxi shale in Sichuan Basin and its surrounding areas. Compared to the Longmaxi shale, the Lower Cambrian Niutitang shale, which has a greater deposition thickness and wider distribution area, is another significant stratum for China's shale gas. Geophysical well logging is one of the most significant methods used for identification and evaluation of shale gas reservoirs throughout the process of shale gas exploration and development. In this paper, the logging response of the Niutitang shale is summarized to “four high and four low”, this was determined through a comparative analysis of three shale gas wells in the Cen'gong block. The Geochemical logging (GEM) data shows that as the depth goes deeper the content of Si (quartz) increases and the content of Al, Fe, K (Potassium), and Clay minerals decreases. In addition, the Niutitang shale mainly has the feature of a single peak or two continuous peaks in T2 spectrum on the nuclear magnetic resonance (NMR) logging response. This has a longer T2 time and greater amplitude than normal shales. The logging response of various lithology and preservation is summarized by overlapping and a cross-plot analysis with the spectral gamma-ray, resistivity, density, acoustic, and compensated neutron logging data, which are sensitive to organic-rich shales. Moreover, the resistivity and acoustic logging data are sensitive to gas content, fluid properties, and preservation conditions, which can be used as indicators of shale gas content and preservation.
San-Dan mercury metallogenic belt is one of the most important parts of the large-scale low-temperature epithermal metallogenic region in Southwestern China, besides Guizhou-Hunan mercury metallogenic belt. To clarify the source of metallogenetic materials, mineralization ages, and geodynamical background is critical for understanding the mineralization mechanism of this region. Considering that the hydrothermal calcite is one of the main gangue minerals of this belt, Sm-Nd geochronology of hydrothermal calcites is used to date Jiaoli-Lae mercury deposit in the middle of the belt. An isochron age (129±20 Ma, MSWD=0.21, εNd=-12.9) has been obtained. This age suggests that the Hg mineralization occurred in Late Yanshanian. This provides some important information and clues to discover the formation and evolution of the mercury deposits and other deposits of the large-scale low-temperature epithermal metallogenic region in Southwestern China. Referring to some other previous research, we conclude that this area underwent two main mineralizing stages, i. e., early stage of 145-155 Ma Sb mineralization, and late stage of 120-135 Ma Sb, Au, Hg, As mineralization. The limestone εNd value of wall rocks of the Guotang Formation (Lower Ordovician Series) is -12.6, which is in good agreement with the εNd of the hydrothermal calcite. This indicates that the ore materials of this mercury deposit probably originated from the ore-bearing Ordovician carbonatite.
The Niujiaotang zinc deposit in southeastern Guizhou, China, is a Mississippi Valley-type Zn deposit within Early Cambrian
carbonate rocks. Sphalerite is enriched in cadmium (average 1.4wt.% Cd), which occurs mostly as isomorphous impurities in
the sphalerite lattice. Discrete cadmium minerals (greenockite and otavite) are rare and are found almost exclusively in the
oxidation zone of the deposit, probably formed as secondary minerals during weathering–leaching processes. Geochemical data
show that the sulfides are enriched in heavy sulfur, with δ34S ranging from +10.0‰ to +32.8‰ (mean +22.5‰). The consistent Pb isotopic compositions in different sulfide minerals are similar
to that of Cambrian strata. The ore lead probably came from U- and Th-rich upper crustal rocks, such as the Lower Cambrian
Wuxun Formation. The ore fluid is of low-temperature (101°C to 142°C) type, with a Na–Ca–Mg–Cl-dominant composition, and is
interpreted as oil-field brine. The data indicate that the metals were mainly derived from the Early Cambrian strata (Qingxudong
and Wuxun Formations), whereas sulfur is sourced from sulfate in Cambrian strata or oil-field brines of the Majiang petroleum
paleoreservoir. The genetic model for the deposit invokes an Early Cambrian shallow-sea environment on the Yangtze Platform.
Zinc and Cd in seawater were concentrated in abundant algae via unknown biological mechanisms, resulting in large amounts
of Zn- and Cd-rich algal ooliths. During the Ordovician, concurrent with destruction of the Majiang petroleum paleoreservoir,
oil-field brines migrated from the center of the basin to the margin leaching metals from the Cambrian strata. In the Niujiaotang
area, preexisting Zn and Cd, particularly in the Qingxudong and Wuxun Formation, were further mobilized by hot brines rising
along the Zaolou fault system, forming stratiform and generally conformable Zn–Cd orebodies in reactive carbonate lithologies.
KeywordsSphalerite–Cadmium–Niujiaotang–China
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