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The Zunyi manganese deposits, which formed during the Middle to Late Permian period and are located in northern Guizhou and adjacent areas, are the core area of a series of large‐medium scale manganese enrichment minerogenesis in the southern margin and interior of the Yangtze platform, Southern China. This study reports the universal enrichment of rare earth elements (REEs) in Zunyi manganese deposits and examines the enrichment characteristics, metallogenic environment and genesis of REEs. The manganese ore bodies present stratiform or stratoid in shape, hosted in the silicon–mud–limestones of the Late Permian Maokou Formation. The manganese ores generally present lamellar, massive, banded and brecciated structures, and mainly consist of rhodochrosite, ropperite, tetalite, capillitite, as well as contains paragenetic gangue minerals including pyrite, chalcopyrite, rutile, barite, tuffaceous clay rock, etc. The manganese ores have higher ΣREE contents range from 158 to 1138.9 ppm (average 509.54 ppm). In addition, the ΣREE contents of tuffaceous clay rock in ore beds vary from 1032.2 to 1824.5 ppm (average 1396.42 ppm). The REEs from manganese deposits are characterized by La, Ce, Nd and Y enriched, and existing in the form of independent minerals (e.g., monazite and xenotime), indicating Zunyi manganese deposits enriched in light rare earth elements (LREE). The Ceanom ratios (average –0.13) and lithofacies and paleogeography characteristics indicate that Zunyi manganese deposits were formed in a weak oxidation‐reduction environment. The (La/Yb)ch, Y/Ho, (La/Nd)N, (Dy/Yb)N, Ce/Ce* and Eu/Eu* values of samples from the Zunyi manganese deposits are 5.53–56.92, 18–39, 1.42–3.15, 0.55–2.20, 0.21–1.76 and 0.48–0.86, respectively, indicating a hydrothermal origin for the manganese mineralization and REEs enrichment. The (δ13CV‐PDB (−0.54 to −18.1%) and (δ18OSMOW (21.6 to 26.0%) characteristics of manganese ores reveal a mixed source of magmatic and organic matter. Moreover, the manganese ore, tuffaceous clay rock and Emeishan basalt have extremely similar REE fractionation characteristic, suggesting REEs enrichment and manganese mineralization have been mainly origin from hydrothermal fluids. [ABSTRACT FROM AUTHOR]

The Permian was a key period of manganese deposition in Southern China, as evidenced by a series of large-to medium-scale manganese deposits along the margin of the Yangtze Block. This study characterizes representative examples that occur in late Middle Permian silicon–mud–limestones in Zunyi and adjacent areas and examines their implications for manganese deposit genesis and sedimentary environment. The manganese deposits are typical carbonates deposits, with the main manganese-bearing mineral being rhodochrosite, followed by calcimangite, capillitite, manganocalcite, and kutnohorite in decreasing abundance. The ore bodies, hosted in the black shale series of the Late Permian Maokou Formation, are mainly stratiform or stratoid in shape, usually have lamellar, massive, banded, fragmental, or pisolitic structures, and contain paragenetic gangue minerals including rutile, barite, pyrite, and chalcopyrite, etc . These features are characteristic of hydrothermal exhalative sedimentary deposits, implying that this was their mode of genesis. The Mn-ores have higher Co, V, Ni, Cu, Sr and total REE content, lower Y/Ho ratios, and characterized by the Fe–Mn–(Cu + Co + Ni) × 10, lgTh vs. lgU, P 2 O 5 vs. Y and Fe/Ti vs. Al/(Al + Fe + Mn) diagrams strongly suggest hydrothermal activity during manganese mineralization. The Th/U, V/Cr and V/(V + Ni) ratios of samples from the Zunyi manganese deposits are 0.38–3.27, 3.11–24.00 and 0.38–0.99, respectively, indicating the sedimentary environment was weakly oxidizing to reducing condition. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ore-forming fluids originated from ELIP volcanism-related hydrothermal activities. • The sedimentary environment likely evolved from anoxic through suboxic to oxic. • Permian Mn mineralization led by ELIP-induced tectono-hydrothermal activities and redox changes. The Permian manganese (Mn) ore belt lies in western South China Block, and contains many large-medium Mn deposits. However, the genesis and metallogenic mechanism of these deposits remains a matter of debate. Here we shed light on this issue based on new mineralogical, geochemical, and Sr isotope data from the Changgou Mn deposit in the Zunyi orefield (Guizhou, SW China). The Mn orebodies occur as lenses and layers, and are hosted in carbonaceous-siliceous limestone, carbonaceous mudstone, and tuffaceous claystone. The ores show a variety of structures (e.g., detrital, brecciated, massive, and banded) and complex mineral compositions (e.g., galena, sphalerite, siegenite, molybdenite, barite, rutile, and monazite). The ore samples are characterized by chalcophile and siderophile element enrichments, low Al 2 O 3 /TiO 2 ratios (mean 10.36), high and varying Mn/Fe ratios (1.26–4.71), distinctly high REY (rare earth and yttrium) contents (mean 766.46 ppm), and high La/Ce (mean 1.04) and low Y/Ho (mean 28.17) ratios. The footwall and ore samples have 87Sr/86Sr ratios of 0.706897 to 0.707093. Integrated mineralogical and geochemical signatures indicate that the ore-forming fluids were most probably originated from hydrothermal activities related to early-stage Emeishan Large Igneous Province (ELIP) subaqueous volcanism. Redox proxies reveal that sedimentary conditions evolved from euxinic-anoxic (footwall deposition), through anoxic-suboxic (Mn mineralization), to oxic (hanging-wall deposition). Such changes were probably resulted from a coeval eustatic sea-level drop and enhanced seawater oxygen supply. Manganese was likely initially enriched in form of Mn2+, and subsequently precipitated with oxidation, and then transformed into Mn carbonate during sediment diagenesis. To conclude, the tectono-hydrothermal activities and major environmental redox changes led by the ELIP volcanism have provided a favorable source-migration-sink system for the Mn mineralization. [ABSTRACT FROM AUTHOR]

[Display omitted] • High Hg anomalies in the Zunyi Mn deposit coincidence with ELIP eruption. • Trace elements in the Zunyi deposit suggest changes in the land–ocean-climate system. • ELIP eruption triggered the formation of Middle Permian Mn deposits in South China. South China hosts a large number of Middle Permian marine sedimentary Mn deposits (MSMDs) coeval to the eruption of the Emeishan Large Igneous Province (ELIP). The linkage between these MSMDs and ELIP eruption remains unclear. Here, we observed anomalously high Hg concentrations and Hg/TOC ratios, and a shift of Δ199Hg to near-zero at the base of the Middle Permian Zunyi MSMD. These results suggest ELIP eruption as a possible driving force for the deposition of the Zunyi MSMD. Principal component analysis (PCA) of trace element concentrations of the Zunyi MSMD samples revealed three clusters of trace elements. Cluster A elements (Cr, Zn, Mo, Sb, and Tl) are anomalously high at the basal of the Zunyi MSMD, confirming ELIP as a driver for the formation of this deposit. Cluster B elements (Ba, Rb, and Cu) are high in the entire deposit, supporting elevated oceanic productivity. A stepwise increase in Cluster C elements (Li, Ga, Sn, Zr, Nb, Hf, Ta, and W) concentrations in the Zunyi MSMD suggests enhanced terrestrial weathering. We infer that the ELIP eruption triggered an increased input of terrestrial nutrients to the ocean, causing increased oceanic productivity and rising dissolved O 2 levels in the surface water of the middle Permian ocean in South China, favoring Mn deposition and MSMDs formation. [ABSTRACT FROM AUTHOR]