Although heterogeneous photo-Fenton reactions on nanoparticulate iron oxides effectively degrade organic pollutants, the underlying surface mechanisms remain debated. Here, we demonstrate how these pathways are modulated by specific hematite crystal facets. To investigate the influence of particle surface structure, methylene blue (MB) adsorption and photodegradation kinetics are examined using facet-engineered hematite nanoparticles with distinct exposed facets. The results reveal that MB photodegradation strongly depends on both pH and facet orientation. When normalized by surface area, (116) facet shows higher photodegradation activity than those with (104) or (001) facets. This enhanced activity is attributed to favorable electronic structure and surface characteristics, including a smaller optical bandgap, faster charge transfer, and superior H2O2 decomposition. In contrast, the photodegradation capacity follows (104) 〉 (116) 〉 (001), primarily due to the higher density of surface-active sites on the (104) facet. These sites promote coupled MB adsorption and degradation, enabling removal of a greater overall quantity of MB. Additionally, under high pH conditions, hematite can degrade MB in the dark, with capacities following (001) ≫ (116) 〉 (104). These findings underscore the critical catalytic role of specific hematite surfaces and advance the understanding of facet-dependent photoinduced redox chemistry at mineral-water interfaces.

Nanoparticle aggregates in solution controls surface reactivity and function. Complete dispersion often requires additive sorbents to impart a net repulsive interaction between particles. Facet engineering of nanocrystals offers an alternative approach to produce monodisperse suspensions simply based on facet-specific interaction with solvent molecules. Here, we measure the dispersion/aggregation of three morphologies of hematite (α-Fe2O3) nanoparticles in varied aqueous solutions using ex situ electron microscopy and in situ small-angle x-ray scattering. We demonstrate a unique tendency of (104) hematite nanoparticles to maintain a monodisperse state across a wide range of solution conditions not observed with (001)- and (116)-dominated particles. Density functional theory calculations reveal an inert, densely hydrogen-bonded first water layer on the (104) facet that favors interparticle dispersion. Results validate the notion that nanoparticle dispersions can be controlled through morphology for specific solvents, which may help in the development of various nanoparticle applications that rely on their interfacial area to be highly accessible in stable suspensions.

Here, we examine how radiation impacts the dissolution behavior of boehmite by subjecting dry nanoparticles of different sizes to Co-60 gamma radiation and subsequently analyzing their dissolution behavior in caustic solutions as a function of temperature. The measured kinetics show that irradiation with an amount 228.24 Mrad significantly slows the dissolution rate, particularly for smaller sizes at lower temperatures. Specifically, the temperature-dependent dissolution rates of irradiated 20 nm boehmite versus pristine material in 3 M NaOH solutions were several times lower (e.g., rate constant of 0.026 vs 0.075 h(-1) at 60 degrees C), with an apparent activation energy 40 kJ mol(-1) higher. Although various imaging techniques and X-ray diffraction measurements consistently revealed no obvious differences between pristine and irradiated samples, after irradiation significant binding energy shifts were detected in the X-ray photoelectron Spectroscopy peaks of Al 2p and O 1s, and a change in their relative intensities indicated a lower O/Al ratio. This suggests that gamma-irradiation may stabilize boehmite particle surfaces by driving their chemistry and structure toward more stable aluminum oxide forms. This finding may help explain slower dissolution rates of boehmite in nuclear waste and may be useful for the development of more robust predictive models and effective strategies for waste processing.

Synthesis of iron oxides with specific phases and particle sizes is a crucial challenge in various fields, including materials science, energy storage, biomedical applications, environmental science, and earth science. However, despite significant advances in this area, much of the current palette of particle outcomes has been based on timeconsuming trial-and-error exploration of synthesis conditions. The present study was designed to explore a very different approach to 1) predict the outcome of synthesis from specified reaction parameters based on using machine learning (ML) techniques, and 2) correlate sets of parameters to obtain products with desired outcomes by a newly designed recommendation algorithm. To achieve this, four ML algorithms were tested, namely random forest, logistic regression, support vector machine, and k-nearest neighbor. Among the models, random forest outperformed the others, attaining 96% and 81% accuracy when predicting the phase and size of iron oxide particles in the test dataset. Surprisingly, the permutation feature importance analysis revealed that volume, which may strongly relate to pressure, was one of the important features, along with precursor concentration, pH, temperature, and time, influencing the phase and size of iron oxide particles during synthesis. To verify the robustness of the random forest models, prediction and experimental results were compared based on 24 randomly generated methods in additive and non-additive systems not included in the datasets. The predictions of product phase and particle size from the models agreed well with the experimental results. Furthermore, a searching and ranking algorithm was developed to recommend potential synthesis parameters for obtaining iron oxide products with the desired phase and particle size from previous studies in the dataset. This study lays the foundation for a closed-loop approach in materials synthesis and preparation, beginning with suggesting potential reaction parameters from the dataset and predicting potential outcomes, followed by conducting experiments and analyses, and ultimately enriching the dataset.

The complex deformation styles of large intraplate strike-slip fault systems in the multi-stage superimposed basin are hot topics worldwide. This article proposes structural models and evolution processes for such strike-slip fault systems in the Tarim Basin based on high-resolution 3D seismic data and deep wells. Our analyses reveal that strike-slip fault in the Tarim Basin formed with different structural styles in five tectonic layers from the Sinian to the Permian that accompanies the Sinian rift systems and uplift, the Lower–Middle Cambrian reversed faults and salt tectonics, the Ordovician fault-karst systems, the Silurian to the Carboniferous en-echelon transtensional faults, and the Permian volcanic structures. Influenced by the multi-tectonic layers and complex evolution history, the strike-slip faults performed as multi-layer flower structures and various fault types. The evolution history of paleo-uplifts also influenced the distribution characteristics of strike-slip faults, such as X, diamond, and V shapes in the Tabei uplift and T shapes in the Tazhong uplift. The strike-slip faults formed in late Cambrian stage were associated with unconformities, inverted structures, and growth strata in deep layers. The different tectonic evolution models of the Tabei and the Tazhong uplift were built, which shows pre-existing structures, the lithological combinations from the rift basin to the marine basin, and the change of regional tectonic stress from the Cambrian to Permian are controlling factors of the strike-slip fault systems. These models provide a new interpretation method for intraplate strike-slip fault systems worldwide.

The structural geometric and kinematic analysis of the Shunbei No. 5 fault zone (fault SB5) in the Tarim Basin was conducted based on the fault interpretation on the three-dimensional (3D) seismic sections and coherence slices of several seismic reflecting surfaces in the study area. The fault SB5 evolution model was recovered using the fault pattern analyses and palaeostress reconstruction, which required factors like the width of the damage zone, maximum throw of the main fault, vertical separation, and the shear crack angle along the fault zone. The results show that: (1) Four tectonic layers in the vertical direction are identified according to the difference of structure style, divided by the top and bottom of the Cambrian salt rocks, and the top surface of the Ordovician carbonate. (2) Strike-slip faults in the study area are the middle segment of the large strike-slip fault zone composed of major faults and overlap zones; 11 stepovers in the study area can be classified into three types according to their geometric characteristics. Strain concentration appears on the overlap zone under the continuous shear stress field and shows high activity. Fault SB5 has undergone three major evolutionary stages: the transpressional stage in the Middle Ordovician, the dextral shearing stage in the Early Silurian, and the final evolutionary sinistral process in the Late Devonian.

The organic-rich shale of the Lower Cambrian Shuijingtuo Formation in the Yangtze area is considered a high-quality source rock in South China. Geochemical proxies are used to reveal the formation and preservation conditions of the Shuijingtuo shale in Yichang in the middle Yangtze area. Geochemical proxies for paleoredox (U/Th, V/Cr, Ni/Co, and U-EF versus Mo-EF), paleoproductivity (Ba/Al, Cu/Al, and Ni/Al), and terrigenous influx (Al and Ti) have been employed to interpret the mechanism of organic matter (OM) accumulation. The total organic carbon (TOC) contents of the Shuijingtuo shale is between 0.19 wt% and 4.77 wt% (with an average of 1.38 wt%). The shale can be divided into two intervals based on TOC content, the lower interval with high TOC (TOC >2 wt%) and the upper interval with low TOC (TOC <2 wt%). The results of the geochemical proxies show that the lower interval shale was formed in an anoxic setting with fair paleoproductivity and relatively low terrigenous influx. The upper interval shale was deposited mainly under oxic conditions, with gradually enhanced oxidation, decreased productivity, and relatively high terrigenous influx compared to the lower interval shale. The water mass inferred by the Mo/TOC ratios was a restricted environment with episodic upwelling in the lower interval. The TOC contents display a positive correlation with both the paleoredox and paleoproductivity proxies, indicating that anoxic/dysoxic and high productivity favored OM accumulation. The Co x Mn versus Cd/Mo relationship also suggests that the OM accumulation is chiefly determined by preservation in a restricted environment. These data indicate that the redox condition acts as the dominant factor for OM accumulation. A depositional model is proposed that emphasizes the importance of preservation for OM accumulation of this shale.

Although it is well known that phosphate retention in soils and sediments is strongly influenced by binding to secondary iron oxides, there have been relatively few studies examining its adsorption/desorption behavior on multicomponent particles of realistic natural complexity. In this study, natural Mn-rich limonite (LM), was used to prepare naturally complex Fe- and Mn-oxide composite materials to examine phosphate adsorption/desorption. To clarify the role of the Mn-oxides, results for the LM sample were compared to those for an acid treated version (LAT), in which the acid-extractable Mn-oxide fraction has been selectively eliminated while leaving the Fe-oxide fraction intact. The saturated adsorption capacity on LAT was almost double that on LM, suggesting that phosphate adsorption to the iron oxides is strongly occluded by the Mn-oxide fraction. This result is reinforced by the comparing the pH dependence and fits to adsorption isotherms, and by desorption experiments and STEM-EDS mapping showing that phosphate loading on Mn-oxides was limited. Hence, although the collective results confirm that phosphate uptake and strong binding is selectively controlled by the Fe-oxide fraction, our study reveals that the Mn-oxide fraction strongly interferes with this process. Therefore, phosphate uptake behavior on metal oxides cannot be predicted solely on the basis of the Fe-oxide fraction present, but instead must take into account the deleterious impacts of other intimately associated phases. For co-diagenetic Fe/Mn-oxide composites in particular, Mn-oxides appear to severely limit phosphate uptake on the Fe-oxide fraction, either by hindering access to binding sites on the Fe-oxide or by lowering their affinity for P.

Despite the biogeochemical importance of phosphate fate and transport in aquatic environments, little is known about how competition with other common aqueous oxyanions affects its retention by mineral surfaces. Here, we examined the competitive uptake of phosphate and silicate on goethite over a wide pH range, using batch measurements supported by DFT calculations. The results show selective adsorption of phosphate at pH < 4 and silicate at pH > 10 with little to no competitive effect. However, between 4 < pH < 10, the total phosphate and silicate loading was found to be almost equal to that of silicate loading from single-component solution, revealing a proportionate competition for surface site types and a competitive effect controlling their mutual retention. DFT-calculated adsorption energies and charge density redistributions for various surface complexes on different charged (101) and (210) facets are consistent with the trends observed in batch measurements, suggesting that the observed behavior reflects the primary controlling influence of goethite surface chemistry at the molecular scale. An important implication is that at the circumneutral pH in most environmental systems, where iron oxyhydroxides comprise much of the reactive interfacial area, unbound phosphate concentrations may be strongly controlled by dissolved silicate concentration, and vice versa.

Taking the shale of Shuijingtuo Formation of Lower Cambrian in Yichang area as the research object, the shale reservoir characteristics are comprehensively evaluated and classified by fitting regression and formula calculation method in this study, using laboratory testing and geophysical logging data. The results show that the interpretation data of ECS (elemental capture spectroscopy) logging has a high correlation with the measured minerals data, which can be a good method to evaluate the minerals component of the shale. The calculated content of brittle minerals at the lower part of Shuijingtuo Formation is the relatively highest, generally more than 40%, which is the most favorable segment for fracturing. The correlation coefficient between the interpretation data of CMR (combinable nuclear magnetic resonance) logging and the result of laboratory porosity test is 0.97, which can effectively and accurately evaluate the reservoir porosity. The evaluation results show that the porosity of the lower member of Shuijingtuo Formation is generally greater than 3%, while that of the upper member is generally less than 3%. The lower segment is with the relative optimal physical conditions. There is a good correlation between the acoustic logging data and the gas bearing content testing results. A gas bearing content evaluation model is established. The results show that the gas bearing content of the lower 20 m shale is generally more than 2%, indicating that the lower part is a shale gas enrichment segment. Mechanical parameters such as Young modulus, Poisson ratio and brittleness index of shale reservoir are evaluated by using the logging data of P-wave time difference and S-wave time difference. The continuous 15 m shale at the lower part is with the relatively optimal low Poisson ratio, high Young modulus and high brittleness index, developing the optimum brittle condition. Based on the evaluation and classification of above parameters, the shale is divided into three types. The Type I is the optimal, mainly located at the bottom. Its thickness is 8.5 m in total. The Type II mainly develops at the middle part. The Type III is the worst, mainly at the upper part.

泥盆系佘田桥组泥岩是南方页岩气勘探重点层位之一.为揭示湘中坳陷邵阳凹陷佘田桥组泥岩岩相特征及其发育控制因素,基于系统岩心描述、矿物组分和地球化学采样及测试,对邵阳凹陷佘田桥组泥岩岩相类型、沉积环境特征及其对岩相发育的控制进行了研究,探讨沉积环境演化对岩相类型发育的控制作用.结果表明,佘田桥组泥岩依据矿物组分含量主要识别出硅质泥岩、混合质泥岩、硅质岩、钙质泥岩4种岩相类型,进一步垂向上可划分为5个岩相组合段.岩相组合段Ⅰ和Ⅲ相对富硅质,而组合段Ⅱ、Ⅳ和Ⅴ钙质含量相对较高.沉积环境分析表明佘田桥组泥岩形成于大陆边缘背景;主要处于相对干热气候条件,其中在早期和中期发育相对温湿气候,中期时相对最为温暖潮湿;海平面先上升后下降;中段泥岩中具有过量硅富集特征,主要为生物成因,而受热液作用影响较小;陆源碎屑输入相对较为稳定,在中期时相对最低.沉积环境演化和岩相发育之间的响应关系表明,岩相的发育主要受到古气候、陆源碎屑供给、海平面变化和生物作用等的综合控制,泥岩硅质组分主要来自陆源碎屑输入,生物作用富硅造成了中段硅质富集,而后期当气候向干热转化时,钙质组分增加,泥岩岩相向富钙方向演化.

Based on the sedimentological and geochemical analysis of total organic carbon (TOC) and major and trace elements in the marine Upper Ordovician-Lower Silurian Wufeng-Longmaxi Formations in Yichang, Central Yangtze area, paleoredox conditions (indicated by U/Th, V/Cr, Ni/Co, TOC-TS-Fe diagram, and Mo-U covariations), paleoproductivity (indicated by Ba-bio, Ba/Al, P/Ti, Ni/Al, Cu/Al, and Zn/Al), terrestrial detrital influx (indicated by Ti and Al), paleoclimate (indicated by chemical index of alteration and Rb/Sr), and upwelling (indicated by Co x Mn) are revealed within the framework of sea-level changes. The influences of these factors on organic matter enrichment are also discussed. The results identify four third-order sequence boundaries in the Wufeng-Longmaxi Formations; each sequence can be divided into one transgressive systems tract (TST) and one regressive systems tract (RST) according to sea-level changes. The high-TOC interval mainly developed in TST1 (average 3.44%) and TST2 (average 3.68%). The analysis of geochemical indicators shows that during the TST1 depositional stage, the climate was dry and cold, the bottom water was in a stable anoxic condition accompanied by rising sea level, and the seawater had moderate-high paleoproductivity. In the RST1 stage, extensive sea-level fall occurred, and the water was anoxic, with decreased productivity and weakened organic matter accumulation. In the TST2 stage, the sea level rise rapidly, extensive anoxicity and high productivity of the water produced the most ideal environment for organic matter enrichment and the highest TOC. In the RST2 stage, sea level slowly fell, the water column gradually became a stable oxidized environment, productivity was low, the terrestrial detrital influx increased and tended to stabilize, and the climate gradually changed to warm and humid conditions, forming relatively organic-poor shale. The upwelling mainly developed during the period of TST1 to TST2, and ceased in the RST2. The correlation analysis between TOC and the above indicators and the Co x Mn versus Cd/Mo diagram show that TOC is chiefly controlled by paleoredox, paleoproductivity, climatic conditions, and terrestrial detrital influx, indicating that preservation conditions are the crucial factor. Sea-level change played a key role in preservation conditions. In the transgression stages, sea-level rise led to the enhancement of reducing water, which controlled the organic matter enrichment in shale.

A reliable and effective model for reservoir physical property prediction is a key to reservoir characterization and management. At present, using well logging data to estimate reservoir physical parameters is an important means for reservoir evaluation. Based on the characteristics of large quantity and complexity of estimating process, we have attempted to design a nonlinear back propagation neural network model optimized by genetic algorithm (BPNNGA) for reservoir porosity prediction. This model is with the advantages of self-learning and self-adaption of back propagation neural network (BPNN), structural parameters optimizing and global searching optimal solution of genetic algorithm (GA). The model is applied to the Chang 8 oil group tight sandstone of Yanchang Formation in southwestern Ordos Basin. According to the correlations between well logging data and measured core porosity data, 5 well logging curves (gamma ray, deep induction, density, acoustic, and compensated neutron) are selected as the input neurons while the measured core porosity is selected as the output neurons. The number of hidden layer neurons is defined as 20 by the method of multiple calibrating optimizations. Modeling results demonstrate that the average relative error of the model output is 10.77%, indicating the excellent predicting effect of the model. The predicting results of the model are compared with the predicting results of conventional multivariate stepwise regression algorithm, and BPNN model. The average relative errors of the above models are 12.83%, 12.9%, and 13.47%, respectively. Results show that the predicting results of the BPNNGA model are more accurate than that of the other two, and BPNNGA is a more applicable method to estimate the reservoir porosity parameters in the study area.

The formation and preservation conditions of the organic matter (OM) in the Upper Devonian Shetianqiao Formation were investigated to assess the mechanism of the OM enrichment in the shale in the Shaoyang sag. The total organic carbon (TOC) contents of the shale range from 0.2% to 4.4%. The shale can be divided into three intervals. The terrestrial input during Interval 2, as indicated by the Al2O3 and Ti proxies, was relatively small. The chemical alteration index (CIA) shows that the Shetianqiao Formation mainly formed in a warm and humid climate, however, climate cooling occurred in Interval 2. Intervals 1 and 3 were mainly deposited in a restricted environment, whereas Interval 2 experienced upwelling. The climate cooling may have been the driver for the upwelling. The UEF, MOEF, and Mo-U covariation diagrams indicate that Interval 2 was mainly deposited under reducing conditions, whereas Intervals 1 and 3 were chiefly formed in an oxidizing environment. The Cu/Al ratios and excess Si (Si-xs) suggest that Interval 2 was formed in significantly higher marine productivity than Intervals 1 and 3. The plot of Co (ppm) x Mn (%) versus Cd/Mo, the logarithmic relationship between Co (ppm) x Mn (%) and TOC, and the good correlations between TOC and the productivity proxies suggest that productivity was the primary factor for the OM enrichment. We constructed a depositional model that emphasizes the control of productivity driven by upwelling on the OM enrichment.

In the last several years, the massive success of the Fuling shale gas field in south‐western China has shown great potential in finding giant shale gas fields in the Upper Yangtze area, and it has also attracted the increasing attention from geologists to find more shale gas reservoirs around the world. However, there is still a great dispute as to whether the neighbouring Lower Yangtze area is a next potential shale gas block in China. In this study, we evaluate preliminarily the shale gas potentials of five important sets of marine shales based on systematic analyses for the sedimentary environment, thickness, total organic carbon (TOC), thermal maturity, and other organic geochemistry parameters of both geological records from outcrops and wells in the Lower Yangtze area. The first two sets of marine shales occur in the Lower Cambrian and the Ordovician, and they all are of over–high organic maturity due to strong effects from regional tectonic movements and thus have poor potential. Although the Lower Silurian shales are widely distributed in the Lower Yangtze region, a terrigenous delta, a low amount of organic matter (TOC < 1.2%), and late tectonic activity together created unfavourable conditions for the generation and accumulation of the Lower Silurian shale gas. The Permian black shales occur in the Middle and Upper Permian. Several proxies, such as the appropriate maturity (vitrinite reflectance Ro of approximately 2.0%), abundant organic matter (TOC of approximately 4 wt%), good total hydrocarbon potential (S1 + S2), and high level of hydrocarbon conversion have resulted in good conditions for shale gas generation. However, the relative thinness (only 30 m), severe tectonic modification, and regional cap rock are not favourable for shale gas preservation. The Lower Yangtze area therefore is not an excellent block for shale gas exploration compared to its neighbouring Upper Yangtze area. However, in some areas with less structural deformation, the possibility of finding shale gas reservoirs cannot be ruled out, especially for the Permian shales, which had a greater opportunity to generate and accumulate shale gas than the other marine shales. In addition, for new shale gas exploration breakthroughs in the future, structural studies are essential in offering better understanding of the preservation conditions in the Lower Yangtze area.

基于钻井岩心资料,对贵州岑巩区块下寒武统变马冲组黑色页岩取心段进行系统采样、主微量元素测试及沉积地球化学分析.研究结果表明:1)古盐度判别指标Sr/Ba及Rb/K分布显示,下寒武统变马冲组黑色页岩沉积时期属局限海背景 下的半(微)咸水—淡水相沉积,变马冲组一段—三段古盐度垂向变化不大;Sr丰度与碳酸盐矿物含量之间具明显的响应关系;2)古氧相指标V/Cr、Ni/Co、U/Th比值及δU值分布表明变马冲组黑色页岩沉积为氧化为主、间或贫氧的环境,V/(V+Ni)比值判别偏于还原环境;3)古气候判别参数"C"、Sr/Cu及SiO2/Al2O3比值表明该套页岩沉积期主体属温湿气候,利于有机质形成;4)古水深及离岸远近判别参数Rb/Zr、Sr/Ba比值分布显示水体较浅、离岸较近的沉积特征,结合物源及沉积构造背景 指征参数分析,变马冲组黑色页岩属大陆边缘离岸较近、水体较浅的陆源碎屑沉积.此研究认识揭示了岑巩区块下寒武统沉积环境的演化,进而为该套黑色页岩的有机质富集机理及页岩气选区评价提供一定的地质依据.

鸟眼构造是碳酸盐岩地层中一种特殊的构造,指示潮上-潮间带沉积环境.安徽巢湖地区三叠系东马鞍山组底部普遍发育一层鸟眼构造,但对其矿物学、地球化学特征及成因还缺乏基本的认识.通过光学显微镜、粉晶X-射线衍射(XRD)、拉曼光谱分析及LA-ICP-MS原位微区元素含量测定等方法,对东马鞍山组鸟眼构造的矿物学及元素地球化学特征进行探究.结果 表明:鸟眼内部矿物组合以方解石为主,石英及黏土矿物含量较低,方解石晶粒较大且由核部到边部晶粒逐渐变小,富集Sr、REE等离子半径较大的元素;基质矿物组合以白云石为主,石英及黏土矿物含量多于鸟眼核部,有机质含量较高,主要富集Fe、Cu、Ti等离子半径较小或不易迁移的元素.这些综合信息反映了巢湖东鞍山组鸟眼构造是由成岩阶段基质白云岩化析出Ca,在沉积有机质分解聚集形成的气泡孔洞中重新沉淀形成方解石而成.

Colloform pyrite (CPy) is widely distributed in the Tongling mineralization cluster of the Middle–Lower Yangtze River Mineralization Belt (MLYRMB), China. There have many debates as to whether such CPy is associated with Late Mesozoic igneous or Carboniferous sedimentation. CPy from the Xinqiao deposit, a representative of the stratabound sulfide deposits in the MLYRMB, was studied by powder X‐ray diffraction (XRD), field‐emission scanning electron microscopy (SEM), and high‐resolution transmission electron microscopy (TEM). The results show that CPy mainly comprises pyrite, pyrrhotite, quartz, and illite. Pyrite in CPy shows cubic, globule, and xenomorphic morphologies. No octahedral or pyritohedron was observed. Most of the quartz crystals display xenomorphic morphology, where pyrite mold are popular on the surface. Organic matter (OM), which is usually bound to illite, is an important component in CPy. Morphological investigations which exhibit detrital features of quartz and clay minerals indicate that they were derived from continental weathering. Specially, some hexagonal pyrrhotite nanoparticles which show mackinawite morphology are coexisted with OM. The results indicate that the transformation process of sulfides possibly is mackinawite (the precursor) —hexagonal pyrrhotite—pyrite. Thus, compositional and micro‐textural characteristics of CPy in Xinqiao deposit suggest it to be a sedimentary origin rather than a hydrothermal origin which is associated with Yanshanian magmatism. Moreover, the coexistence of CPy and stratabound sulfide orebodies in the MLYRMB suggests a causal link between the two. It is considered that CPy might have served as a Cu mineralization geochemical barrier for the Cu‐bearing ore‐forming fluids, which originated from the Mesozoic magma in the MLYRMB.

Copper-gold-iron polymetallic deposits are widely distributed in the Tongling uplift area, however, many small-scale iron deposits are also existed in this area, such as Yeshan iron deposit, one of the typical iron deposits. This deposit is characterized by the strata-bound orebodies and mostly hosted in the Carboniferous Huanglong Formation. The iron ore mineral in this deposit is dominant by specularite/hematite. In order to further investigate the forming mechanism of the iron deposit and its relationship with the sedimentary environment, detailed field and microscope observations had been focused on various locations and occurrence of hematite ores in this paper, and three types of hematite were identified ( Hem 1, Hem 2, Hem 3). In-situ LA-ICP-MS analyses of hematite showed that Hem 1 had high Si, Al, Ti contents and relative high contents of V, Cr, Co, Ni, Cu, Zn, Sr, Ba, Sn, Pb, as well as low Co/Ni ratio ( < 1 ). SEM observations showed quartz ( acid-insoluble components of Hem 1) was 2 similar to 600 mu m in size, microstructures and micromorphologies, such as aeolian fracture, holes and long striped V-shaped impressions were existed on the surface, at the same time, some quartz had nanometer silica globules adhered, indicating these quartz had a detrital origin in the intertidal environment. Above analysis also manifested that sedimentary iron formation consisted of hematite was existed in the Huanglong Formation and recrystallized. Hem 2 and Hem 3 had low Ti content, variable contents of Si, Al, Mn in major elements. According to the chemical components and plots of elements, both Hem 2 and Hem 3 were from mixed origins of which two groups can be divided : ( 1 ) the sedimentary-hydrothermal overprinted origin ( Hem 2(SH)/ Hem 3(SH) ) , this group was featured by high W and low Mn, Si contents with Co/Ni ratio <1.5; (2) the hydrothermal origin ( Hem 2(H) , Hem 3(H) ) , this one had low W, high Mn, Si contents with Co/Ni ratio > 1. 5. Hence, Hem 2(SH) showed great differences to its associated magnetite in trace elements, on the contrary, Hem 2(H) had similar contents of trace elements to the associated magnetite. Hem 2(SH) / ( Hem 3(SH) ) showed depleted in trace elements ( except W) compared to Hem 2(H), ( Hem 3(H) ) , and variations of trace elements in Hem 2(SH), Hem 3(SH) , Hem 2(H) or Hem 3(H) reflected the inheritance of elements in the hydrothermal overprinted process and the evolution process of hydrothermal components and its impacts to the precursor, but Hem 1 was not the precursor of Hem 2(SH), Hem 3(SH) according to the plots of elements. The above results indicated Yeshan iron deposit might belong to a sedimentary-hydrothermal overprinted deposit, the sedimentary iron formation in the Huanglong Formation was dominant by siderite, and provided most of the metallogenic material for this deposit, then it was overprinted by the hydrothermal fluid derived from Yanshanian magmatism. Poly-genetic hematite not only provides important evidences for the concentration process of Yeshan iron deposit, but also provides important enlightenments for the relation between hydrothermal overprinted iron deposits and syngenetic sedimentary environment of Huanglong Formation in the Tongling area.

Tongguanshan ore field is the representative of the five major ore fields in Tongling mineralization cluster, and its metallogenesis remains a topic of debate. The stratabound sulfide orebodies dominate the main copper-bearing sulfide orebodies in Tongguanshan ore field. The colloform pyrite is common in this type of stratabound sulfide orebody, and its formation and genesis are still controversial which on the contrary limits identification of the stratabound sulfide orebody. In this paper, the mineral composition, morphology and micro-structure of colloform pyrite ores in Tongguanshan deposit and Tianmashan deposit were systematically studied through field emission scanning electron microscopy (FE-SEM) , optical microscopy, powder X-ray diffraction (XRD) and micro-area laser Raman spectroscopy. The results show that colloform pyrite ores display colloform, ooliticand concentric structure, and the concentric structure was cut by chalcopyrite and hematite, siderite veins. The concentric structure is mainly composed of marcasite + organic matter and colloform pyrite. The grain sizes of colloform pyrite range from several nanometers to hundreds of nanometers and the granular pyrites are dominated by euhedral-subhedral cubic shape with minor irregular microcrystals. The colloform pyrite crystals at the edge of veins have large particle size, and have much high degree of crystallinity or recrystallization. Dolomite and illite in ores show small particle size and often coexist with colloform pyrite, showing typical sedimentary characteristics. The coexisting quartz has high degree of roundness, secondary enlargement texture and colloform pyrite mold impression on its surface, which shows that it is elastic origin. These systemic information indicate that colloform pyrite in Tongguanshan ore field was direct precipitation from the sub-closed marine basin environment instead of magmatic hydrothermal system, and may deposit through biogeochemistry processes. Colloform pyrite with high porosity, high chemical activity and high content of organic matter content maybe act as ore-forming metal element precipitant for copper (gold) -bearing hydrothermal fluid being derived from Yanshanian magma and limits formation of stratabound occurences of stratabound sulfide orebodies in the ore field and Tongling mineralization cluster.