The Neoproterozoic Doushantuo Period represents a critical transition interval in the Earth's history. As one of the key sedimentary records formed during this period, phosphorites provide vital information for deciphering the paleoceanic environment and biological evolution of the era through their trace element and isotopic compositions. This study investigates the Weng'an Yingping phosphorite deposit within the Yangtze Block. Our analysis combines geochemical proxies such as nitrogen and sulfur isotopes (S15N, S34S) with measurements of total nitrogen (TN) and trace elements concentrations to reconstruct paleoenvironmental conditions. The Yingping phosphorite deposit exhibits TN contents of 48.5-373 mg/kg (average 126.80 mg/kg), S15N values of -2.29%o to 7.20%o (average 3.33%o), and S34S values of 20.59 to 32.46%o (average 30.00%o). These results collectively indicate an oxidized water column during the Doushantuo Period, with the marine nitrogen cycle dominated by nitrification and assimilation. A stable and ample nitrate reservoir supplied essential nutrients for biological activity, thereby promoting variations in biomass and biodiversity. Concurrently, biological processes induced variation in nitrogen isotope fractionation, reflecting coupled co-evolution of the nitrogen cycle and biota. Ultimately, intense microbial activity in this environment was pivotal in enriching and precipitating phosphorus, leading to the formation of phosphorites in the late Doushantuo.

Potassium is a critical mineral resource for global agricultural security. Besides soluble potash salts, insoluble potassium resources hosted in black shale series represent an important alternative potash mineral resource. Extensively developed Cambrian potassium-rich black shales occur in the Wanshan District of Tongren, eastern Guizhou Province, southwestern China. They have K₂O contents ranging from 8% to 11% and prospective reserves exceeding 5 billion tons. However, the potassium enrichment mechanism and its controlling factors in the potassium-bearing shales of this region remain unclear currently. Therefore, this study presents petrographic and elemental geochemical analyses of two representative sections in Wanshan, Tongren, Guizhou. The results indicate that potassium-rich felsic terrigenous detritus in the northwestern study area was transported to a passive continental margin setting, and deposited under restricted, suboxic to anoxic-dominated water conditions. The sedimentation-diagenesis stage underwent potassium metasomatism — a process that promoted the transformation of aluminous clay minerals into illite, eventually leading to the formation of potassium-bearing shales with K-feldspar and other minerals as the major potassium-bearing phases. This study provides a scientific basis for understanding potassium enrichment in the Cambrian black shales of eastern Guizhou and offers a valuable reference for exploring and developing potassium resources.

Accurately constraining metal sources in hydrothermal breccia-hosted gold (Au) deposits that occur within pre-mineralization bodies is challenging yet essential for deciphering regional Au mineralization. This study uses geochemical and isotopic (S, Hg) analyses to constrain the genesis of the Yongxin Au deposit in Northeast (NE) China, which is hosted between Early Carboniferous syenogranite (hanging wall) and mylonitized granite (footwall). Geochemical data show that PyI in mylonitized granite is relatively As-rich, while PyII-IV in hydrothermal breccias are enriched in Ag, Te, and Bi, which points to a deep-sourced magmatic fluid. The delta 34S values of pyrite from the Yongxin deposit range from 2.26 to 6.41 %o, with most samples (79 %) falling within the magmatic S range. Some samples show positive deviations, indicating a mixed sulfur source dominated by deep magmatic input with contributions from the upper continental crust. Furthermore, the ores and pyrites from the Yongxin Au deposit exhibit delta 202Hg values (-0.40 +/- 0.31 %o, 1SD, n = 10) higher than those of the mantle, and Delta 199Hg values (0.00 +/- 0.05 %o, 1SD, n = 10) lower than those of contemporaneous epithermal deposits linked to metasomatized deep-sourced melts, indicating minor incorporation of continental upper crustal material into the ore-forming system. Integrating regional tectonic constraints, we propose that during the Early Cretaceous extension driven by Paleo-Pacific plate rollback, deep-soured Au-Ag-Te-Bi-rich melts ascended with some crustal assimilation. Exsolved fluids migrated along granite contacts, and metal precipitated during explosive decompression, forming the Yongxin breccia-hosted Au deposit.

Mantle-derived rocks provide a unique perspective for understanding Earth's interior and tectonic evolution. This study employs laser ablation-inductively coupled plasma-mass spectrometry U-Pb dating of apatite, in situ micro-area Nd isotope analysis, and comprehensive assessments of major-and trace elements in the Leidong minette of South China to elucidate its petrogenesis and geodynamic significance. The SiO2 content of Leidong minette ranges from 53.19 wt% to 55.08 wt%, classifying it as an intermediate magma. It is characterized by high concentrations of K2O (7.64-7.96 wt%), MgO (5.02-5.22 wt%), and K2O/Na2O(molar) ratios (21.22-23.41) indicating that it is an ultrapotassic rock. U-Pb isotopic analysis of apatite reveals an age of ca. 108 Ma, potentially in response to the retreat of the ancient Pacific subduction zone. The apatite 143Nd/144Nd (0.51198-0.51210) and (143Nd/144Nd)i (0.511780-0.511922) show slight variations, with relatively consistent epsilon Nd(t) (-14.0 to -11.2). The whole-rock samples show enrichment in large-ion lithophile elements, depletion in high field strength elements, and negative anomalies of Nb, Ta, and Ti. They also exhibit high Th/Yb (31.7-36.3) and Ta/Yb (1.1-1.2). These data, in conjunction with previously reported whole-rock Sr-Nd-Pb isotopic characteristics, suggest that the source of the Leidong minette is predominantly enriched mantle type II altered by fluid metasomatism from an ancient slab. The geophysical data and whole-rock geochemistry, with (Gd/Yb)N (5.0-5.3), support the hypothesis that the source region for the diamond-bearing minette was at depths of at least 100 km (similar to 3 GPa). Regionally, the lamprophyres and related rocks (ca. 250-90 Ma) in central and northern Guangxi Province, China, represent an orogenic setting, primarily modified by subduction-related fluids, whereas the related rocks (ca. 490-438 Ma) in southeastern Guizhou Province are associated with an intraplate environment, influenced by melt enrichment. This indicates that the boundary between the western margin of the Cathaysia Block and Yangtze Craton may lie between these regions and their amalgamation time is not the late early Paleozoic but the Neoproterozoic. From the analysis of diamond ore-forming conditions, it appears that high-grade, large-scale diamond deposits are unlikely to have formed in the South China region.

Sedimentary manganese (Mn) carbonate deposits, i.e., the land-based major Mn mineral resources on Earth, are of great scientific value for palaeoceanographic research because Mn is a redox-sensitive metal whose deposition is restricted by oceanic redox conditions. The genesis of Mn carbonates remains controversial and the palaeoceanographic implication behind sedimentary Mn carbonate deposits is unclear. Here, we investigate the precipitation mechanisms, spatiotemporal redox, and hydrographic dynamics of the Middle Permian Zunyi Mn carbonate deposits in South China. The preserved original Fe-Mn oxide residues within Mn carbonate nodules, coupled negative delta 98MoNIST+0.25 values (mean: -1.59%0), negative delta 13Ccarbonate values (mean: -7.68%0), and variable Ce anomalies (0.21-1.71), collectively support that Mn(II) carbonates were formed via the diagenetic reduction of original Mn(III/IV) oxides. Multiple lines of evidence (e.g., lithofacies, authigenic Mo and U enrichments, Ce anomalies, delta 34Ssulfide, and delta 98MoNIST+0.25) indicate that the deep-waters in the Qianzhong rift basin rapidly shifted from euxinic-anoxic to suboxic-oxic conditions during Mn deposition. This shift was driven by the rapid shallowing and exposure of the basin induced by continuous crustal uplift and global regression. These insights support an "oxidation expansion model" for the genesis of the Zunyi Mn deposits, which involves the downward expansion of the redoxcline triggering swift oxidation of anoxic deep waters and in situ precipitation of Mn(III/IV) oxides, and subsequently transforming to Mn(II) carbonates via diagenetic reduction. This study concludes that ancient Mn carbonate deposits are reliable proxies for paleoceanic redox fluctuations, and an overview of Mn carbonate deposits in the broad context of geological history supports their close genetic connection with oceanic redox perturbations.

Marine sedimentary manganese deposits can be divided into two types based on their host rock: black shalehosted and carbonate rock-hosted. In contrast to black shale-hosted deposits, carbonate rock-hosted Mn deposits exhibit significant differences in lithology and geochemical composition. Moreover, the precipitation mechanisms and mineralization processes of Mn in carbonate rock-hosted deposits remain a subject of ongoing debate. Central Guangxi is a relatively developed area of carbonate rock-hosted Mn ores, with Longtou Mn deposit as one of the typical representatives, which develops multilayered ore bodies with well-preserved ore textural features. This study focuses on the sedimentology, mineralogy, elemental geochemistry, and carbon isotope, aiming to elucidate the sedimentary mineralization process and its key controlling factors. The primary Mn ore bodies with industrial value in the Longtou deposit mainly have four layers (numbered as I, II, III, and IV), all predominantly hosted in the Lower Carboniferous Baping Formation limestone and chert-bearing limestone. The primary Mn-bearing ores include calcium rhodochrosite, kutnohorite, Mn-calcite, and Mn oxides. Layer I is characterized by well-developed concentric ring structures, primarily composed of kutnohorite, dolomite, and calcite-rich rhodochrosite. In contrast, layer II, III, and IV exhibit a higher abundance of calcium rhodochrosite, kutnohorite, and braunite, with minerals frequently displaying interlocking textures or replacement relationships. The Mn ores exhibit a visible assemblage of acicular pyrophanite, scheelite, and rhodonite. Combined with geochemical parameters such as Y/Ho, and the triangle diagram 10x(Ni + Co + Cu)-Fe-Mn, 100x(Zr + Ce + Y)-15x(Cu + Ni)-(Fe + Mn)/4, these characteristics suggest that submarine hydrothermal activity provided an important material foundation for the mineralization of the Mn ores. Through a comprehensive analysis of lithofacies, delta 13CV-PDB values, total organic carbon (TOC) content, and Ce anomalies, the study suggests potential differences in mineralization mechanisms and processes between the ore layer I and ore layer II, III, and IV. It is proposed that layer I was formed through the upwelling of Mn-rich, anoxic waters into the shallow-water zone, which markedly changed the redox conditions and promoted the precipitation of Mn minerals. This shift also introduced additional dissolved inorganic carbon and nucleation sites for crystal growth, leading to the formation of Mn carbonates with calcite/dolomite cores. Subsequently, as the environmental conditions gradually shifted toward a more oxidizing state, the dissolved Mn2+ in layer II, III, and IV was predominantly precipitated as Mn oxides. These oxides were then reduced by organic matter, forming Mn carbonates. These understandings offer valuable insights into the sedimentary Mn carbonate mineralization process in carbonate rock-hosted deposits and contribute to the broader development of theoretical frameworks for sedimentary Mn carbonate deposit formation.

The Early Cambrian represents a globally significant phosphorus-formation period, particularly noted for producing REY-rich phosphorites in South China. However, substantial differences exist in the REY enrichment levels among these phosphorites. Particularly, the REY contents of the Early Cambrian Meishucun Stage phosphorites from Guizhou and Yunnan exhibit pronounced disparities, with the controlling factors behind these variations remaining a subject of debate. To address this issue, this study conducted comparative analyses of representative REY-bearing phosphorites from Cambrian Meishucun Stage in Bailongtan, Yunnan province, and Zhijin, Guizhou province, China. Advanced analytic techniques, including XRF, ICP-MS, and ICP-OES, were employed to determine major, trace elements and REY concentrations in different phosphorite types. And complementary methodologies including OM, SM, SEM-EDS, and EPMA were utilized to examine the mineralogical and textural features. The results indicated that biofossils preserved in the phosphorites of both regions are small shelly fossils (SSFs), with carbonate fluorapatite as the principal component. Zhijin phosphorites exhibit significantly higher REY enrichment compared with Bailongtan phosphorites, and REY contents positively correlate with the abundance of SSFs. In-situ analyses revealed that REYs are primarily concentrated within SSFs, which were better preserved in oxic and open environments with relatively slow sedimentation rates. The multilayered nested structures of SSFs facilitate the absorption of REYs from seawater and porewater, which corresponding to the biogenic structures of bioapatite observed in modern deep-sea REY-rich sediments. These findings suggested that SSFs play a crucial role in REY enrichment, with Zhijinites potentially serving as the optimal host phase for REY enrichment. Conclusively, biota play an important part in the REY-rich mineralization of phosphorites, offering new insights into the genesis of global sedimentary REY-bearing phosphorites. This understanding also opens new considerations for optimizing REY extraction processes from such phosphorites.

Sedimentary manganese carbonate deposits hosted within the uppermost Doushantuo Formation on the northern margin of the Yangtze Platform formed under contrasting water depth environments, providing critical insights into the sedimentary environmental controls on manganese mineralization. Different biological structures (ooids, stromatolites, and spherulites), particle size of framboidal pyrite and U enrichment identify two distinct depositional facies: shallow-water carbonate platform (Laifeng and Yangjiawan) and deep-water slope (Maliaoxi and ZK2021). Mo/U, delta 13C of carbonate and minerals indicate a strong oxidation-reduction Mn cycle in Laifeng and Yangjiawan, but a weak cycle in Maliaoxi and ZK2021 during the formation period of primary manganese carbonate. The patterns of rare earth elements as well as (Eu/Eu*)PAAS, (Y/Ho) PAAS and (La/La*) PAAS indicate that the alabandite forming fluid and the manganese carbonate fluid are similar, mainly being seawater. Sulfur isotopes (the average delta 34S of alabandite = 6.54 parts per thousand) indicate that the sulfur was mainly sourced from the bacterial sulfate reduction. Differences in the supply of Fe and the alkalinity may cause that a large amount of alabandite (up to 44.6 wt% in ores) formed in Laifeng and Yangjiawan, while there is only a very small amount of alabandite but a high content of pyrite in Maliaoxi and ZK2021. Differences in water depth, redox condition, acid-base and the supply of iron control the cycles of Mn, C and S, promote the differences in mineral assemblage, and restrict the formation process of manganese deposits, which has indicative significances for the mineralization of manganese ore in different environments.

Many gold and antimony deposits in the Yunnan-Guizhou-Guangxi region in SW China are characterized with co-occurrence and symbiotic differentiation of Ao and Sb.However,the metallogenic relationship between Au and Sb and the difference between ore-forming processes of Au and Sb need to be further investigated.Fluorite,a common gangue mineral widely occurred in hydrothermal deposits,has been extensively studied to reveal the formation process of ore deposit.The Qinglong antimony deposit and the Nibao gold deposit in the Youjiang basin,with their matching mineralization ages and wallrock alteration characteristics,are selected as ideal objects for investigating the symbiotic differentiation of gold and antimony mineralization.Therefore,in this paper,we have carried out the in situ LA-ICP-MS trace element study of fluorites from the Qinglong antimony deposit and the Nibao gold deposit,in order to reveal the difference between their respective gold and antimony mineralization processes.Mineralogical and cathodoluminescence(CL)studies of fluorites reveal that three different stages of Sb-mineralization related fluorites in the Qinglong antimony deposit have been identified.Specifically,the first-stage fluorites have right-declined REE patterns with LREE-enriched and HREE-depleted characteristics.The second-stage fluorites are characterized by the MREE enrichment.The third-stage precipitated fluorites generally inherited the characteristics of REE distribution patterns of the second-stage fluorites though the third-stage fluorites have relatively low ∑REE contents.In general,the ∑REE values of fluorites are gredually decreased from the first-stage fluorites,second-stage fluorite to the third-stage fluorites.All fluorites have negative Ce anomalies.There are fluorites of two precipitation stages associated with the gold mineralization in the Nibao gold deposit.The first-stage fluorites have right-declined REE patterns,whilst the second-stage fluorites are characterized with MREE-enriched REE patterns.Their REE patterns are generally similar to those of fluorites in the Qinglong antimony deposit.Diagrams of Y/Ho,La/Ho,Tb/Ca,and Tb/La ratios for fluorites at different stages reveal that there are different genetic characteristics between fluorites of the early-ore-stage and those of the late-ore-stage.Especially,the early-ore-stage fluorite is of the dominant hydrothermal fluid filling genesis,while the late-ore-stage fluorite was formed in close association with the water-rock reaction which resulted in the input of a significant portion of host rock components into the late-stage ore-forming fluid,and the gradual increase of pH values and the decrease of total REE contents of the ore-forming fluids from the early-to late-stage.The comprehensive analysis suggested that the antimony mineralization in the Youjiang Basin is associated with the acidic ore-forming fluid which caused the dissolution of carbonate wallrock through the intensive water-rock reaction and thereby resulted in the formation of a significant of fluorite.Moreover,the increase of pH values and the decreaseof temperatures of the evolved ore-forming fluids could be contributed to the extensive precipitation of stibnite in the antimony deposit.Alternatively,the ore-forming fluids of gold deposits are characterized with weakly acidic to neutral nature.They caused the limited decarbonation of carbonate wallrocks and then resulted in the formation of a little fluorite and a large amount of dolomite,which is conducive to the formation of a large amount of Au-bearing pyrite.Based on the statistic analysis of REE data of stibnite and associated ore-related gangue minerals in antimony deposits in the Youjiang Basin,it is believed that the MREE enrichment characteristics for REE patterns of gangue minerals could be resulted from the LREE super-enrichment of a large amount of hydrothermal stibnite of antimony deposits.

Multistage mineralization overprinting is important for the formation of giant hydrothermal gold deposits. The Youjiang basin in SW China has undergone at least three major deformation phases in the Mesozoic, but their relationship with the large-scale gold accumulation in the region remains enigmatic. Here, we study the large Nibao gold deposit (reserve > 70 t Au) in the northern part of the basin, which has both fault-controlled and stratabound orebodies. We identified a pre-ore stage and syn-ore stage including four tectono-hydrothermal (T-H) substages (i.e., T-H stage 1, 2, 3 and 4) for the local mineralization at Nibao. The pre-ore stage is dominated by coarse-grained pyrite coexisting with TiO2 polymorphs in the Middle-Late Permian basaltic rocks. The T-H substage 1 is characterized in that the sedimentary pyrites are brecciated in bedding-parallel faults. Fluorination and silicification occur in the T-H substage 2, which is re-brecciated at the T-H substage 3 forming the highest gold grade ore in high-angle thrust fault. The T-H substage 4 presents as fault reactivation within minor calcite and pyrite deposition. Mineralogy and in-situ trace element analyses reveal that mineral dissolution and reprecipitation (incl. dolomite, auriferous pyrite and TiO2 polymorphs) is ubiquitous during the multistage tectono-hydrothermal process, and the continuous alteration overprinting may have promoted gold accumulation. This replacement process of different generations of auriferous pyrite is also recorded by their inherited sulfur isotopes, giving a narrow delta S-34 (-3.1 to + 2.1 parts per thousand) range. Anatase is the main accessory phase of TiO2 polymorphs, as identified with LA-ICP-MS trace element and laser Raman spectroscopic analyses. Moreover, the anatase can been divided into two types (type-I and II) based on their texture, alteration and chemistry. The type-I anatase commonly occurring in the stratabound ore is characterized by higher Zr (mean 1,730 ppm), V (mean 1,412 ppm), and Cr (mean 110 ppm) contents than type-II that coexists with zoned pyrite in the fault-controlled ore (mean 26 ppm, 187 ppm, and 38 ppm, respectively). Additionally, W (mean 636 ppm) and Mg (10,021 ppm) in type-II are much higher than type-I ones (mean 135 ppm W and 476 Mg). These features show that the sedimentary-stage Zr-V-Cr-rich type-I anatase was dissolved via fluid metasomatism, and reprecipitated as the hydrothermal-stage W-Mg-rich and Zr-poor anatase, with gold gradually enriched. Besides, the anatase phase of TiO2 polymorphs also indicates that the Nibao gold deposit was formed under low pressure-temperature condition. Overall, we propose that the Nibao is a Carlin-type gold deposit, dominated by multistage tectono-hydrothermal events.

During the Ediacaran–Cambrian transition, a series of stratal continuous and well-preserved siliceous rock and phosphorite assemblages developed in Qingzhen, Guizhou Province, China, facilitating research on the biological evolution, marine chemistry, and palaeoecological environment of this period. Therefore, we investigated the paleontology, trace and rare earth elements, total organic carbon, total sulfur content, and Zn isotopes of the phosphorus-bearing rock series in the Taozichong Formation of the Cambrian period in Qingzhen. Geochemical analysis reveals that the sedimentary rocks in this area were formed in the oxygen-rich seawater environment and were not affected by high-temperature hydrothermal activity. The upwelling ocean current provided abundant rare earth elements and other nutrient elements, as well as conditions for the prosperity of biota in Qingzhen. In addition, the δ66Zn value (−0.21‰–0.41‰ range and 0.17‰ mean) in the Qingzhen phosphorous rock series was much lower than that in seawater, indicating a strong level of biological productivity. The variation trend of δ13C, δ18O, and δ66Zn exhibited four stages and three obvious drift events. The results suggest that climate change during this period led to the intermittent flourishing and extinction of organisms, which triggered the negative drift of δ13C and δ18O in the ocean, resulting in a coordinated response of δ66Zn. The unique ecological environment of the Taozichong Formation in Qingzhen also provides favorable conditions for the population continuation of Ediacaran-type benthic soft-bodied metazoon dominated by discoid fossils, Shaanxilithes, worm fossils, and sponge fossils in the Cambrian strata, as well as participation in the global biological explosion events. The study area provides new insights for rebuilding the global Ediacaran–Cambrian ecosystem during the transition period.

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 & UDelta;199Hg 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 O2 levels in the surface water of the middle Permian ocean in South China, favoring Mn deposition and MSMDs formation.

The turbidite-hosted Au-Sb-Hg deposits in the Sandu-Danzhai area are distributed along the southwestern marginal fault of the Jiangnan Orogen, yet any genetic link among the Au, Sb and Hg mineralization and their respective ore-forming process remain unclear. Here, we investigate the Paiting Au(-Hg) and Miaolong Au-Sb deposits and present a new metallogenic model based on detailed petrographic observations, and in-situ trace element (EPMA and LA-ICP-MS) and sulfur isotope (fs-LA-MC-ICPMS) analyses on sulfide minerals. Our results show that the ore formation in the Sandu-Danzhai metallogenic belt (SDMB) can be divided into Au (pyrite + arsenopyrite + dolomite), Au-Sb (pyrite + arsenopyrite + stibnite + quartz), Sb (stibnite + native antimony + barite + dolomite + quartz) and Hg (cinnabar + calcite) stages, based on mineral paragenetic and vein crosscutting relationships. Trace element compositions suggest that progressive As enrichment in pyrite is accompanied by increasing Au, Sb and Cu contents, implying that these elements may have been leached from the same source via fluid-rock reactions. Sulfur isotope compositions of the sulfates and sulfides in the Au-Sb-Hg ores reveal that the sulfur was originated from thermal-chemical sulfate reduction (TSR) of marine sulfates in the Cambrian ore-bearing strata. Thus, we propose that deep metamorphic fluids (as evidenced from the high fluid CO2 and CH4 contents) may have promoted ore-material (e.g., Au, Sb, As, Hg) mobilization in the metamorphic basement and/or Cambrian strata. As for the metal transport and precipitation mechanism, fluid-rock interaction may have decreased the ore-fluid As content and caused auriferous pyrite precipitation. Meanwhile, changes in temperature and oxygen-sulfur fugacity may have significantly decreased Sb solubility, leading to extensive stibnite precipitation. Cinnabar associated with calcite was likely deposited via carbonate dissolution in the Cambrian strata in late hydrothermal (waning) stage. Overall, we propose that the Au-Sb-Hg deposits in the SDMB are best classified as orogenic type, and the metallogeny was controlled by boundary faults of the Jiangnan Orogen.

Mercury (Hg) anomalies in sedimentary records are a newly developed proxy of large volcanism in the geological past. Tuff layers host abundant volcanic ash. Here, we measured the Hg isotopic composition of several tuff layers in South China. Tuff samples in the Late Ordovician Wufeng Formation and the Middle Triassic Guanling Formation mostly show positive Δ199Hg values of – 0.01 to 0.10‰ and – 0.06 to 0.16‰, respectively, suggesting large-scale arc-related volcanisms due to oceanic subduction of the Yangtze Block underneath the Cathaysia Block oceanic plate subduction in the Late Ordovician and during the closure of the Paleo-Tethys ocean in the Middle Triassic. Tuff samples in the Middle Permian Dachang Layer mostly show near-zero Δ199Hg values (– 0.08 to 0.00‰), suggesting volcanism was driven by the Emeishan large igneous province eruption. Results of this study verify Hg isotopes as a useful proxy of the fate of volcanism in geological history.

Li是一种碱金属元素,由于它不受氧化还原和生物效应的影响,因此在追踪地球元素循环方面非常有利.并且Li在海洋中的留存时间远大于海水混合时间,因此海洋中的Li具有相对均一的组成,从而能够代表对应地质历史时期整体海洋情况.近年来海洋Li同位素被应用在示踪大陆风化模式领域,并取得了很多成果.笔者等在系统总结全球海洋Li循环作用和表生地质作用的Li同位素分馏机制的基础上,通过收集并整理、估算了不同时期海洋Li同位素组成,对地质历史时期海洋Li同位素组成变化与改变大陆风化模式相关的地质事件进行分析,再结合同时期碳酸盐岩C、Sr同位素数据进行对比分析,探讨Li、C、Sr同位素演化与地质事件之间的关系.最后,讨论了目前海洋Li同位素组成方面研究的不足,为后续利用海洋Li同位素记录示踪大陆风化模式的应用提供了参考.

黔西南地区是我国卡林型金矿主要产区之一,已有几十年的开采历史,随着金矿的开采,产生了大量的尾矿资源.为了解黔西南金矿尾矿(渣)资源现状,运用地质块段法、矿物学和地球化学等方法对贞丰—晴隆—安龙地区5个典型金矿尾矿(渣)中金含量、赋存状态及周围环境进行了调查.结果表明:卡林型尾矿(渣)中金以包裹金状态赋存在黄铁矿中,红土型尾矿中金以游离态赋存在铁钛氧化物中.水银洞和烂泥沟金矿尾矿中的金品位超过工业品位,具有二次提金的潜力.同时,对紫马和老万场2个尾矿库周边的土壤、植物和水质进行采样测试,发现样品中的Cd、Hg和As严重超标,对环境有一定的危害.因此,对于未达到工业品位且对环境有影响的黄金尾矿,建议进行复垦种植、采矿充填或加工成建材,这样不仅实现了尾矿(渣)的减量化处理,而且减少了其对周围环境的危害.

Objectives: The siliciclastic rocks of the Middle Permian Maokou Formation at Yingpan, Nayong, Guizhou,are the main object of this study, focusing on the genesis of siliciclastic rocks and the origin of defined silica usingelemental earth methods.Methods: Based on the field investigation work, the ratio characteristics and enrichment patterns of major,trace and rare earth elements were analyzed by elemental geochemical methods, combined with geologicalbackground and petrographic paleogeographic features to discern the siliciclastic genesis and depositionalenvironment.Results: Elemental geochemical correlation ratios and diagrams of diagenetic discrimination indicate that therewas a significant input of hot water material during the formation process, and silicon was mainly derived from thehot water system. The depositional environment is the Qianzhong Terrace Trench in the deep-water phase of thesame sedimentary fracture.Conclusions: The early submarine volcanism of the Emei mantle column or the associated hot water actionprovided the siliceous fraction required for the deposition of siliciclastic rocks at Yingpan, Nayong. And the earlysubmarine volcanism of the Emei mantle column may have an important controlling role on the Permian siliciclasticsedimentation in South China.

黔西北上二叠统峨眉山玄武岩顶部与宣威组底部之间发育一套厚度较为稳定的风化壳,其富集三稀元素.为了揭示三稀元素富集规律,选择威宁县石门坎的毛家坪剖面开展元素地球化学研究.结果表明:三稀元素主要富集于风化壳黏土岩中,且表现为上部三稀元素含量高,下部三稀元素含量低,铝土质黏土岩明显比玄武岩富集铌和稀土元素,尤其是高岭石细脉中异常富集铌(w(Nb2O5)=0.059％)和钇(w(Y)=512.0×10-6),风化壳黏土岩的化学蚀变指数(CIA)多数高达95～100,反映岩石遭受了强烈的化学风化作用.稀土元素球粒陨石标准化配分模式图和微量元素原始地幔标准化蛛网图显示,富铌和稀土元素的风化壳黏土岩物质来源为峨眉山玄武岩.地球元素特征指示成矿环境主要为还原—氧化过渡环境,峨眉山玄武岩遭受长期风化、淋漓作用是形成富稀土元素、铌铝土质黏土岩的关键.