Enrichment characteristics and sources of the critical metal yttrium in Zhijin rare earth-containing phosphorites, Guizhou Province, China

Yttrium(Y)is a critical metallic element that is used widely in modern scientific,technological,and industrial applications.Phosphorites in the Zhijin area of Guizhou Province,China,are famous for Y enrichment,but the enrichment characteristics and sources remain unclear.Previous studies suggested that the sources of rare earth elements(REEs,La-Lu)and Y(REYs,La-Lu+Y)were related to hydrothermal deposition.However,this study presents evidence refuting that hypothesis,with major and trace elemental data collected with quadrupoleinductively coupled plasma-mass spectrometry(Q-ICPMS)analysis.These data show that Y in Zhijin REYscontaining phosphorites has a normal distribution and is particularly enriched relative to other REYs.The Y enrichment degree is different at different∑REY intervals.Specifically,the Y enrichment degree is higher at lower∑REY values and lower at higher∑REY values.The REYs-containing phosphorites show features of primary phosphorites.Both REEs and Y have good correlations with P2 O5 in the phosphorites with low REYs contents(total REYs<535 ppm),whereas at high REYs contents(total REYs>535 ppm),REEs have a good correlation with P2 O5 but Y does not.Inconsistent enrichment processes of REYs are suggestive of complex sources of Y.Thus,seafloor hydrothermal fluids were not the direct source of Y.Normal seawater mixed with terrestrial sources might have contributed to the origin of Y here.This study could lead to improvements in Y mineral resource explorations and the situation involving the global REYs supply crisis.

REE geochemistry of Early Cambrian phosphorites from Gezhongwu Formation at Zhijin, Guizhou Province, China

The Cambrian Gezhongwu Formation in Southwest China is the lowest Cambrian phosphorite unit. The Formation belongs to the Meishucun stage with small shelly fossils. Rare-earth element (REE) data from the Gezhongwu phosphorites of Zhijin documented the depositional conditions. The total REE concentrations are high in the Gezhongwu phosphorites, which are especially rich in yttrium. The PAAS-normalized REE patterns of the Gezhongwu phosphorites are characterized by negative Ce anomalies and slight enrichment of MREE, as being hat-shaped. The hat-shaped patterns suggest that the REE originated from depositional environments rather than from subsequent diagenesis. The negative Ce anomalies indicate that the depositional environments are oxic. The positive Eu anomaly, the high total REE and the hat-shaped REE pattern revealed contributions from the normal marine environment mixed with hydrothermal water to the REE budget of the Gezhongwu phosphorites.

Concerning the Original Viewpoint of Biogeologic Accumulation of the Old Bedded Phosphorites in the Khubsugul and Zavkhan Basins of Mongolia

This paper concerns deals with?biogeologic?accumulation and their peculiarities, lithological unites of the phosphorite-bearing formations of these basins and an evolution of the old biota. Old bedded phosphorites are believed to be connected with specific biogeological events happening in the Neoproterozoic glaciation, which was followed by rapid deglaciation,?Ediacaran bioradiation and the “great” postglacial transgression bearing phosphorites at its initial phase. The Mongolian phosphate basins give evidence of this phenomenon. Khubsugul basin is located in the northern Mongolia. The Neoproterozoic-Cambrian phosphorite-bearing khubsugul group is subdivided into 3 formations as ongolik, kheseen and erkhelnuur which are rich in organic fossils (a group of cyanobacterial mats, archaeocyaths, trilobites) in the ascending order. The Zavkhan basin lies in the western Mongolia. The Ediacaran-lower Cambrian sediments are divided into five formations: Maikhanuul (diamictites), Tsagaanolom (phosphorite-bearing carbonate), Bayangol, Salaanygol and Khairkhan. All the formations contain the paleontological fossils (algae, sponges, cyanobacterial mats, ichnocoenosis, soft-bodied fauna, archaeocyaths, etc.). Bedded phosphorites are the object for comprehensive research of bacterial paleontology. It is shown at example of the Mongolian Khubsugul and Zavkhan sea shelf phosphate basins. The expounded actual material clearly shows that the heterogeneous biologic activity, suitable geologic (transgressive systems tracts) and paleogeographic (glaciations, warm climate, etc.) conditions played an important role in the formation and accumulation of the biogenic bedded phosphorites.

Rare Earth Elements in Egyptian Phosphorites

Egyptian phosphorites from Abu Tartur (Western Desert), El Mahamide mine (Nile Valley) and Rabah mine (Eastern Desert) show variable degrees of relative REE enrichment. Black plateau phosphorites of Abu Tartur are substantially enriched in REE as compared to the Red Sea and Nile Valley phosphorites. P-rich organic matter from the Abu Tartur and Rabah mines recorded negative Ce and positive Eu anomalies. Positive Eu anomaly reveals an anoxic event prior to the phase of Late Cretaceous phosphate formation. Ce is a redox indicator. Mixing of sea water and upwelling during the Late Cretaceous was responsible for the recording of positive Eu and negative Ce anomalies in the Egyptian phosphorites.

Scandium Geochemistry of Phosphorites, Guizhou, Southwest China

Geochemical characteristics of scandium are described with respect to its source, evolution and correlation with REE as observed in Late Sinian and Early Cambrian phosphorites and tuffs in Guizhou. Comparison of chondrite\|normalized REE patterns and some other parameters between the phosphorite and tuff shows that scandium and REE are most likely to have been derived from earlier or contemporaneous marine volcanics or tuffs, with no indication of genetic link to the purple shales, siltstones and dolomites in the area. The conditions under which the Sc bearing phosphorites were formed are discussed in the light of sulfur isotopes and Eh Ph constrains.

Forms of Iron in the Phosphorites of Abu-Tartur Area,Egypt

The Campanian\|Maastrichtian phosphatic deposits in Egypt, called the Duwi Formation, comprise a part of the extensive Middle East to North African phosphogenic province of Late Cretaceous to Paleogene age. The province holds the greatest accumulation of phosphorites in the geological history, possibly in excess of 70 billion metric tons. The phosphate resources in Egypt alone exceed 3 billion metric tons. Two\|third of these three billions occur only in the Abu\|Tartur area.\; Among the phosphorite deposits in Egypt, the phosphorites of the Abu\|Tartur area are characterized by high contents of iron ranging from 3% to 7% with an average of 5%. The detailed mineralogical and geochemical studies on the Abu\|Tartur phosphorites revealed that iron is found in the form of pyrite, ankerite, clay minerals, microinclusions, and iron oxide. Pyrite, which is the major fraction, occurs as filling cement and partial to complete replacement of phosphatic grains and confined to the fresh phosphorites while iron oxide occurs as cryptocrystalline aggregates of red to brown particles and is confined to the weathered outcrops. Exclusive relations between pyrite in the fresh phosphorite samples inside the Abu\|Tartur mine and iron oxide in the equivalent horizon of the weathered exposure indicated that iron oxide was formed by the oxidation of pyrite as a result of weathering. All of these forms harm the quality of ore, manufacturing processes, and the produced phosphoric acid and fertilizers.

贵州织金早寒武世磷块岩中稀土富集机制

稀土元素和钇(REY)是极其重要的战略资源,被誉为“工业维生素”(蒋训雄等,2011),随着科技的进步和应用技术的不断突破,稀土氧化物的价值越来越大,全球市场对稀土(尤其是重稀土)的需求量与日俱增。我国是世界上稀土资源最丰富的国家,白云鄂博稀土矿床和华南离子吸附粘土型矿床提供了世界REY产量的95%以上(Emsbo et al.,2015)。

黔中寒武纪梅树村期磷块岩中小壳动物化石结构和成分:对生物成磷的制约

小壳动物化石微结构及壳体成分的认知对于揭露寒武纪早期小壳动物群的演化具有重要意义,黔中地区早寒武世梅树村期磷块岩中保存了大量的小壳化石,为了获取该时期小壳化石微结构及成分的关键信息,本文利用电子显微镜、扫描电镜对岩石薄片小壳化石个体进行观察、分析,获得了贵州织金熊家场和清镇落夯地区的寒武纪梅树村期磷块岩中小壳动物化石微结构、壳体成分特征。结果显示,织金、清镇地区的磷块岩中小壳化石多样性与其壳体成分表现一致,主要为软舌螺类,其成分为P、Ca、F、O等氟磷灰石组成元素;小壳化石壳体保存有明显的纳米级磷灰石矿化颗粒骨架、多圈层结构、溶蚀多孔隙和管体嵌套的现象。另外,通过电子探针对小壳化石进行原位微区元素面扫描,发现主要元素P、Ca分布在小壳化石及小壳化石碎片中,胶结物几乎不含P元素。综合判断,两个研究区域的寒武纪梅树村期磷块岩小壳动物化石多为异地埋藏保存,且保存过程中,成岩作用等后期磷酸盐化、搬运沉积对小壳化石微结构及其壳体成分产生一定改造影响;基于薄片全玻面扫描推断全岩小壳动物化石(含化石碎片)含量,与磷块岩中磷含量呈正相关关系,认为寒武纪梅树村期小壳动物的繁盛对同期磷块岩的形成具有重要贡献。

贵州织金互层型磷块岩工艺矿物学及浮选试验研究

对贵州织金地区中低品位磷块岩进行工艺矿物学研究,查明了矿石的矿物组成、化学组成、嵌布特征、矿物粒度分布等。结果表明,矿石中主要有用矿物是氟磷灰石,脉石矿物主要是石英,氟磷灰石含量为57.62%,白云石含量为25.34%,还含有少量的石英、黄铁矿、方解石等。氟磷灰石与白云石、石英的嵌布关系紧密,连生关系以三连生以上为主,嵌布关系复杂。利用工艺矿物学参数自动分析系统(BPMA)、X射线衍射(XRD)、X射线荧光光谱仪(XRF)等分析手段并结合相关数据,确定了采用二段式反浮选脱镁工艺流程,可以获得P_(2)O_(5)品位为32.40%、P_(2)O_(5)回收率为85.13%的磷精矿,MgO含量由12.50%降至1.60%,选矿指标较为理想,为该地区磷矿的开发和利用提供了一定的技术依据。

综合测井资料在福泉大湾磷矿富水性特征分析中的应用

水文地质条件是矿山勘探过程中一项极其重要的工作,水文地质工作的好坏决定了后期矿山开采的经济性和安全性,准确地对地层富水性进行划分,则是水文地质勘查中重要的一环。在贵州白岩背斜地区以往的磷矿勘查中,人们通常笼统的将整个灯影组作为含水层,从而使得计算的涌水量远大于实际,给矿山的防水治水带来了极大的浪费。本文通过综合地球物理测井方法对大湾矿区地层的富水性进行研究,并定量的划分出勘查区内地层富水性,从而为水文地质勘查提供准确的物探依据。

华南下寒武统昆阳和织金含磷岩系成磷机制对比研究

早寒武世发生了全球大规模的成磷事件,在华南地区形成了以贵州织金和云南昆阳为代表的大型磷矿床。为探讨两地磷块岩成磷作用的异同及其制约因素,本研究对织金新华和昆阳王家湾含磷岩系开展了矿物学和地球化学分析。结果表明,昆阳地区的胶磷矿和磷灰石矿物粒径大于织金地区的,暗示昆阳地区具有更浅的海水深度、更强的水动力条件;两地含磷岩系的P_(2)O_(5)与Al_(2)O_(3)、SiO_(2)、Zr/Hf及Sr均具有显著-不显著的正相关关系,暗示陆源风化物质的输入提供了早寒武世海洋磷的来源;氧化还原敏感元素(V、Ni、Cr、Mo、U)以及Ce/Ce*在织金含磷岩系中变化范围大于昆阳含磷岩系,指示织金地区海水的氧化还原条件波动更大;两地含磷岩系中的稀土元素均呈现“帽型”配分特征,具有负Ce异常、显著正Y异常、负-弱正Eu异常,表明成磷过程受生物/有机质和铁锰氧化物控制。本研究认为织金新华和昆阳王家湾含磷岩系在成磷机制上可类比性高,岩相古地理和氧化还原条件的差异是导致两地含磷岩系差异的重要原因。

Rare earth element enrichment in sedimentary phosphorites formed during the Precambrian-Cambrian transition,Southwest China

Numerous sedimentary phosphorites in Southwest China were formed around the Precambrian–Cambrian transition(PC–C),including the upper Ediacaran Doushantuo Formation and lower Cambrian Gezhongwu Formation.The Gezhongwu phosphorites in Zhijin exhibit marked rare earth element(REE)enrichment(>1000 ppm),and may represent new REE resources.Although the main characteristics of the Gezhongwu phosphorites have been well constrained,the REE enrichment mechanisms remain unclear.We undertook a comparative study of three typical sedimentary phosphorites with variable REE contents formed at the PC–C transition in central Guizhou Province,Southwest China.These include sections A and B of the Doushantuo phosphorites(560±8 Ma)from the Weng’an area(i.e.,WA-A and WA-B),and the Gezhongwu phosphorites(527±24 Ma)from the Zhijin area(ZJ).The phosphorites were investigated with state-of-the-art macroscale to nanoscale analytical techniques.In contrast to the extraordinary REE enrichment in the ZJ phosphorites(average RREE=1157 ppm),the phosphorites in WA-A(average RREE=234 ppm)and WA-B(average RREE=114 ppm)are REE-poor.Elemental mapping by laser ablation–inductively coupled plasma–mass spectrometry,along with transmission electron microscopy analyses,showed the REEs in the studied phosphorites are hosted in nanoscale francolites.The 87Sr/86Sr and Y/Ho ratios of the francolite grains indicate that greater terrigenous input may have led to more REE enrichment in the WA-A than WA-B phosphorites,but this cannot explain the extraordinary REE enrichment in the ZJ phosphorites.The F/P_(2)O_(5)values of the francolite grains in the ZJ phosphorites(~0.097)are higher than those in the WA-A(~0.084)and WA-B(~0.084)phosphorites,and the grain size of the francolite in the ZJ phosphorites(~89.9 nm)is larger than those in the WA-A(~56.6 nm)and WA-B(~57.4 nm)phosphorites,indicative of more intense reworking of the ZJ than WA phosphorites during early diagenesis.A plot of Nd concentration versus Ce/Ce^(*)reveals that lower sedimentation rates characterized the ZJ phosphorites.Therefore,intense sedimentary reworking during early diagenesis resulted in more REEs being sequestered by the marine phosphates from seawater and pore waters at a lower sedimentation rate,which resulted in the extraordinary REE enrichment in the ZJ phosphorites.Our findings highlight the multiple factors that controlled formation of sedimentary phosphorites around the PC–C transition(especially the intense reworking and redox conditions of the overlying seawater),and provide further insights into REE enrichment in sedimentary phosphorites worldwide.

川西南马边—雷波地区早寒武世磷块岩沉积环境分析

川西南马边—雷波地区是我国重要的磷矿能源资源基地,下寒武统麦地坪组是主要赋矿层位,含磷岩系麦地坪组沿扬子地台西缘呈北东—南西向延伸数百公里(陈天伦等,1990)(1)。研究表明,梅树村期海相沉积型磷块岩的形成与沉积环境密切相关,最有利于磷块岩沉积成矿的特定古地理环境是古陆边缘、古海岛、水下台地(高地)或水下隆起周围的浅水区域(韩豫川等,2012)。

湖北省保康县黄连山磷矿矿床地质特征及成因分析

湖北省保康县黄连山磷矿位于扬子准地台中段的北部、上扬子台坪鄂中褶断区西北的黄陵断穹北西缘,为宜昌磷矿田的一个较为典型的矿床,区内出露地层主要为早古生代的沉积建造,构造要素简单。本文通过黄连山矿区成矿地质背景分析,在研究矿体地质特征和矿石以及围岩特征的基础上,认为黄连山磷矿为大型磷矿,主要发育于白云岩—磷块岩建造和页岩—磷块岩建造,沉积建造特征明显,并且伴生一些含钾页岩,工业矿层产于含磷建造旋回的上部,矿床成因类型为生物化学沉积磷块岩矿床。

宜昌某磷矿石X射线预选试验研究

为合理开发利用宜昌某低品位磷矿资源,进行了X射线预选试验。结果表明:P_(2)O_(5)品位18.74%的磷矿样碎至40~0 mm情况下,采用筛分(筛孔宽10 mm)、40~10 mm粒级X射线预选抛废、预选块精矿和10~0 mm粒级粉矿合并,获得了P_(2)O_(5)品位25.45%、P_(2)O_(5)回收率91.03%的综合精矿,达到磷产品P_(2)O_(5)品位≥25%、P_(2)O_(5)回收率≥80%的研究目标要求;中低品位磷矿石采用筛分—X射线预选工艺处理,不仅环保、高效、生产成本低、资源综合利用率高,而且工艺流程稳定可靠;块废石用于井下充填,可有效解决采空区塌陷问题,消除工业固废的潜在次生灾害。

Separation and Enrichment of Rare Earth Elements in Phosphorite in Xinhua,Zhijin,Guizhou

The phosphorite ores-deposits rich in rare earth elements(REE) in Zhijin, Xinhua, Guizhuo occurs in the early Cambrian Meishucun and at the bottom part of Qiongzhusi stage (the upper layer of phosphorites), belonging to Yangzi stratum section. The living creature scraps was proved existent in dolomitic-phosphorites by experiments, The REE could be extracted to provide the worthy data for the further using. Adopting the HNO3 to extract REE, through the ion exchange method, the REE recovery rate could be reached 85.44%, having certain reference value.

Rare Earth Elements Compositions and Genesis of Xinhua Large-Scale Phosphorite Deposit in Western Guizhou, China

Zhijin County in Western Guizhou is one of the most important production areas of phosphorites in China. In order to investigate genesis of the phosphorites, their REE compositions were analyzed by using inductively coupled plasma emission mass spectrometry (ICP-MS) method. For comparison, phosphorites from the Lower Cambrian black rock series in Southern China, such as Zunyi in Guizhou and Zhangjiajie in Hunan Province, were also analyzed. The analytical data show that: (1) Xinhua phosphorites possess a quite high and greatly varied total rare earth elements (ΣREE), which varying between 164.23×10-6 and 1395.01×10-6 with average of 642.54×10-6, remarkable differentiation between light (LREE) and heavy rare earth elements (HREE), and the ΣLREE/ΣHREE ratios varying between 5.04 and 6.52. The ΣREE and ΣLREE/ΣHREE ratios of the Zunyi and Zhangjiajie phosphorites are 156.69×10-6～637.41×10-6 with average of 431 75×10-6 and 3.17～6.95 with average of 4.37 respectively; (2) All the phosphorites from Xinhua, Zunyi and Zhangjiajie show remarkable negative Ce anomalies. Besides, the Xinhua phosphorites possess lower δCe, which varying between 0.26 and 0.53 with average of 0.35, while δCe of the Zunyi and Zhangjiajie phosphorites are 0.30～0.66 with average of 0.47, suggesting that all of the phosphorites are typical marine sediments deposited mainly in ancient peri-continental seas, and the depositional position of the Xinhua phosphorite might be deeper; (3) Most phosphorites from Xinhua, Zunyi and Zhangjiajie possess unremarkable positive Eu anomaly, and only a few of samples show obvious ones. The δEu varies between 0.98 and 2.4, suggesting that hot (>200 ℃) and strong reductive hydrothermal fluids might have been involved in genesis of the phosphorites; (4) The Xinhua phosphorite is relatively depleted in HREE, and LaN/NdN and δY of most samples are >1 and >1.5 respectively. Besides, there exists no correlation between δY and δCe, suggesting that the phosphorite was subjected to quite strong weathering and leaching processes, and catagenesis do not greatly modify its REE compositions.

Rare Earth Elements in Zhijin Phosphorite and Distribution in Two-Stage Flotation Process

Zhijin phosphorite is one of super large-scale medium-low grade and REE-bearing phosphorite deposit in Southwest of China. Previous investigations had revealed that this deposit contained appreciable amounts of rare earth elements (REE) reaching up to 1300 μg·g-1. In this paper, REE contents and existing state in single collophanite and dolomite mineral were further analyzed by ICP-MS and EPMA-1600 Electric Probe methods. The results indicated that REE content of collophanite was far more than that of dolomite, and increased with an increase of phosphor. There existed independent minerals of REE in single collophanite mineral, such as cerianite and monazite, but the amount of them was extremely little. No independent mineral of yttrium was found in this investigation. Presumedly, REE and yttrium were present in the form of ions in the lattices of collophanite. Based on above investigation, the two-stage reverse flotation technology was carried out to see the distribution of REE in flotation process. It was found that REE was mainly enriched in phosphate concentrate and recovered in the rough stage flotation. REE recovery of concentrate increased with an increase of P2O5 content and P2O5 recovery of concentrate. Under the optimum flotation condition, REE recovery was 79.25% in the rough stage flotation and 9.94% in scavenging flotation.

Origin of Phosphorite Nodules of Lebedinsky Iron Deposit in Kursk Magnetic Anomaly (KMA) of the Russian Platform

Phosphorite has become increasingly important as the raw material for phosphatic fertilizer. Phosphorite nodules are widespread in the Kursk complex deposit (Russian platform). Genesis of these nodules has long been a matter of debate, and this has hampered understanding of the mechanism and controls in the formation of the nodules. In this paper, we report the petrographical, mineralogical, and geochemical data of the Lebedinsky phosphorite nodules. Petrographic study reveals complex phosphatic cement resulting in the replacement of apatite minerals around quartz grains. The main mineral composition consists of quartz, phosphate minerals (apatite, francolite mainly), feldspar, iron hydroxides and carbonate minerals. These results, when combined with available data, are used to address the origin of the phosphorite nodules. The nodules are characterized by the universal presence of biogenic and chemical signatures which is phosphorus crown around crystal grains. The structure of the nodules is massive. Their texture is depicted by basaltic cement and concretion, which consists mainly of apatite and its varieties, with general formula: Ca_10 (PO_4, CO_3) 6(F,OH,Cl). Variation of mineralogy appears dependent on geological setting. Microscopic observations of biogenic fossils in Lebedinsky phosphorite favor a chemical and biogenic origin of phosphorites. Weathering has been suggested to be capable of liberating as much as 20 %-35 % P_2O_5 from sedimentary rocks. Previous investigations demonstrate that weathering of the Proterozoic substratum was the main cause in the formation of Fe, Mo, Mn, Pb, Zn, and P in the Russian platform. We therefore suggest that both weathering and biochemical processes have been positive in the formation of the Lebedinsky phosporite nodules. However, whether continental weathering or oceanic bio-chemical processes are more relevant in the phosphorite accumulation remains undetermined.

Phosphorite generative processes around the Precambrian-Cambrian boundary in South China: An integrated study of Mo and phosphate O isotopic compositions

Large phosphorite deposits in Central Guizhou,China,were formed around the Precambrian/Cambrian boundary(PC/C),including the Ediacaran(Doushantuo stage)and early Cambrian(Gezhongwu stage).Among them,Gezhongwu phosphorite from Zhijin are enriched in rare earth elements(REE)plus yttrium(REY),reaching 3.503 million tons.Although phosphorites have attracted great attention,the specific sources P and REY remained unclear.To determine the P and REY sources and establish a phosphogenic model of PC/C phosphorite,we present an integrated dataset of Mo and phosphate O isotopes for the first time,along with carbonate C and O isotopes,geology,petrology,and geochemistry.In all samples,d18Op,Y/Ho,and Zr/Hf decreased from the Ediacaran to the early Cambrian,indicating increased terrigenous weathering fluxes while decreased upwelling water input.Furthermore,terrigenous weathering delivery significantly elevated marine REY concentrations in the Cambrian in Zhijin.The Ceanom and d98/95Mo suggest that seawater was oxidized in the later Ediacaran and became entirely oxic in the early Cambrian.The positive feedback between oxygen levels in atmosphere and primary productivity caused progressive oxygenation in ocean-atmosphere system and enable phosphorites to be formed by different mechanisms.Results show that the Lower Doushantuo consist of abiotic intraclasts and exhibited“seawaterlike”REY types,indicating abiological and mechanical reworking phosphogenesis.The Upper Doushantuo and Gezhongwu Formation contained mainly microbial debris and abiogenic intraclasts,and exhibit “hat-shaped”REY plots,suggesting microbially mediated phosphogenesis.Based on this data set,we developed a phosphogenic model illustrating formation of these two phosphorite deposits,wherein the Lower Doushantuo phosphorite formed through the reworking of pre-existing phosphatic sediments in anoxic and abiotic ocean,whereas the Upper Doushantuo and Gezhongwu phosphorite formed via microbial metabolisms in oxic and biotic conditions.Our study has implications on the PC/C phosphorite generative processes,as well as paleoenvironmental conditions.