Rare earth elements (REE) of dissolved and suspended loads in the Xijiang River, South China

The Xijiang River is the main channel of the Zhujiang (Pearl River), the second largest river in China in terms of water discharge, and flows through one of the largest carbonate provinces in the world. The rare earth element (REE) concentrations of the dissolved load and the suspended particulate matter (SPM) load were measured in the Xijiang River system during the high-flow season. The low dissolved REE concentration in the Xijiang River is attributed to the interaction of high pH and low DOC concentration. The PAAS-normalized REE patterns for the dissolved load show some common features: negative Ce anomaly, progressively heavy REE (HREE) enrichment relative to light REE (LREE). Similar to the world’s major rivers the absolute concentration of the dissolved REE in the Xijiang River are mainly pH controlled. The degree of REE partitioning between the dissolved load and SPM load is also strongly pH dependent. The negative Ce anomaly is progressively developed with increasing pH, being consistent with the oxidation of Ce (III) to Ce (IV) in the alkaline river waters, and the lack of Ce anomalies in several DOC-rich waters is presumably due to both Ce (III) and Ce (IV) being strongly bound by organic matter. The PAAS-normalized REE patterns for the dissolved load and the SPM load in rivers draining the carbonate rock area exhibit middle REE (MREE) enrichment and a distinct maximum at Eu, indicating the preferential dissolution of phosphatic minerals during weathering of host lithologies. Compared to the Xijiang River waters, the MREE enrichment with a maximum at Eu disappeared and light REE were more depleted in the South China Sea (SCS) waters, suggesting that the REE sourced from the Xijiang River must be further fractionated and modified on entering the SCS. The river fluxes of individual dissolved REE introduced by the Xijiang River into the SCS vary from 0.04 to 4.36 × 10⁴ mol a⁻¹.     

黔中小流域水体悬浮物与沉积物微量元素地球化学特征及物源指示

系统探讨了黔中小流域水体悬浮物和沉积物中微量及稀土元素地球化学特征。结果表明,元素含量在河流与湖泊、悬浮物与沉积物之间均存在明显差异。稀土元素北美页岩标准化分布模式大致为轻稀土相对富集的平坦模式,δEu为0.82～1.25,δCe为0.79～1.25,整体变化不大,均表现为弱异常。麦翁河稀土总量与分布模式均发生异常,主要受上游盘龙煤矿影响。悬浮物的∑REE与pH呈反相关关系,而沉积物的∑REE却与pH表现出正相关关系,表明悬浮物与沉积物中稀土元素行为的控制因素不同。元素相关分析、因子分析及微量元素图解均表明悬浮物与沉积物中的元素具有同源性,主要来源于流域岩石化学风化和土壤物理侵蚀的产物,而某些金属元素Zn、Co、Cu、Cr、Ni则来源于周边工矿企业、农业生产等人为排放。本研究丰富和发展了喀斯特地区水体元素地球化学,揭示了小流域化学风化与物理侵蚀过程中的元素特征和物质输送状况,并为该流域的生态环境现状、治理及管理提供了科学依据和基础资料。     

赣南小流域水体中稀土元素的地球化学特征

本文以赣南小流域水体为研究对象,利用VG Axiom高分辨多接受双聚焦等离子体质谱仪测定了水体中溶解态稀土元素(DREE)的含量,分析了水体中DREE的分布分异机制,并探讨了稀土元素(REE)产生分异的原因.结果表明,赣南所有的采样区水体中Ce都表现为负异常,说明其在风化壳中少活化.受自然风化作用控制为主的水体相对于页岩除Ce亏损、Eu富集外产生的分异很小,其中Eu的正异常源于Eu富集矿物的优先溶解;蒸发盐矿影响下的水体相对于自然作用为主的水体DREE没有发生明显分异;受稀土矿影响的水体中重稀土元素(HREE)富集、Eu负异常的分布模式继承了稀土矿区风化壳的特征;赣州市下游干流水体中中稀土元素(MREE)富集、Eu负异常的分布模式主要是人为影响的结果.     

河流稀土元素地球化学研究进展

河流系统中,稀土元素(REE)受区域地质背景、风化作用、溶液化学以及水与颗粒物相互作用等因素的影响发生分异。河流悬浮物显示轻稀土(LREE)适度富集;河水显示重稀土(HREE)富集,或在HREE富集的基础上又有适度的中稀土(MREE)富集;与其它微量元素相比,REE在河水与颗粒物之间有较小的分配系数(K≈10-6);河流沉积物多显示平坦的REE配分模式。     

Rare earth geochemistry in the dissolved, suspended and sedimentary loads in karstic rivers, Southwest China

The watershed in the central Guizhou Province (Guizhou Province is called simply Qian) (CQW) is a karstic area. Rare earth elements (REEs) of dissolved loads, suspended particulate material (SPM) and sediments of riverbed are first synthetically reported to investigate REE geochemistry in the three phases in karstic watershed during the high-flow season. Results show that the low dissolved REE concentrations in the CQW are attributed to these rivers draining carbonate rocks. The dissolved REE have significant negative Eu anomaly and coexistence of middle and light REE (MREE??PAAS-normalized La _N /Sm _N and Gd _N /Yb _N ; LREE??PAAS-normalized La _N /Yb _N )-enrichment, which are due to the dissolution of impure Triassic carbonates. REE concentrations in most of SPM exceed that of sediments in the CQW and the average continental crust (UCC). The SPM and the sediments show some common features: positive Eu, Ce anomalies, and MREE enrichment. The controls on the patterns seem to be from weathering profiles: the oxidation state, the REE-bearing secondary minerals (cerianite, potassium feldspar and plagioclase), which are also supported by the evidence of Y/Ho fractionations in the three phases.     

Dissolved rare earth elements in river waters draining karst terrains in Guizhou Province,China

Winter seasonal concentrations of dissolved rare earth elements (REE) of two major river systems (the Wujiang River system and the Yuanjiang River system) in karst-dominated regions in winter were measured by using a method involving solvent extraction and back-extraction and subsequent ICP-MS measurements. The dissolved REE concentrations in the rivers and their tributaries are lower than those in most of the large rivers in the world. High pH and high cation (i.e., Na⁺ + Ca²⁺) concentrations of the rivers are the most important factors controlling the concentrations of dissolved REE in the river water. The dissolved load (<0.22 μm) REE distribution patterns of high-pH river waters are very different from those of low-pH river waters. The shale (PAAS)-normalized REE patterns for the dissolved loads are characterized by light REE-enrichment and heavy REE-enrichment. Water in the upper reaches of the Wujiang River generally shows light REE-enriched patterns, while that in the middle and lower reaches generally shows heavy REE-enriched patterns. The Yuanjiang River is heavy REE enriched with respect to the light REE in the same samples. Water of the Wuyanghe River draining dolomite-dominated terrains has the highest heavy REE-enrichment. Most river water samples show the shale-normalized REE patterns with negative Ce and Eu anomalies, especially water from Wuyanghe River. Y/Ho ratios show that the water/particle interaction might have played an important role in fractionation between HREE and LREE.     

长江与黄河沉积物REE地球化学及示踪作用

长江与黄河沉积物的稀土元素（ＲＥＥ）组成特征不同。长江沉积物ＲＥＥ含量较高,元素含量变化也大于黄河样品;球粒陨石标准化模式表明长江沉积物的（Ｌａ／Ｌｕ）Ｎ、（Ｌａ／Ｙｂ）Ｎ、（Ｇｄ／Ｙｂ）Ｎ的值也相应地比黄河沉积物中的高１０％左右,分布曲线均呈明显的石倾状,轻重稀土分馏明显,相对富集ＬＲＥＥ。且长江样品比黄河样品更富集ＬＲＥＥ,但Ｅｕ亏损不及黄河样品;两者的北美页岩标准化曲线均呈平坦稍右倾状,具有     

Distribution and fractionation of rare earth elements and Yttrium in suspended and bottom sediments of the Kali estuary,western India

Concentrations of rare earth elements (REE) and yttrium (Y), and major metals (Al, Fe and Mn) were measured in suspended particulate matter (SPM) and bottom sediments of the Kali estuary, western India, for their distribution and fractionation. The contents of SPM and metals in it were more uniform along the longitudinal transect during the monsoon. During the post- and pre-monsoons, low SPM in the upper/middle estuary coincided with high Fe and Mn and total REE (∑REE). But in the lower estuary SPM and its ∑REE content increased seaward, while Fe and Mn decreased. The Y/Ho ratios decreased seaward during the monsoon but increased during the post-monsoon. Sm/Nd ratios were more uniform along the transect during monsoon but decreased marginally seaward in other seasons. The Post-Archean Average Australian Shale (PAAS)-normalized REE patterns exhibited middle REE and heavy REE enrichment with positive Ce (\({\text{Ce}}/{\text{Ce}}^{*}\)), Eu (\({\text{Eu}}/{\text{Eu}}^{*}\)) and Y anomalies. The \({\text{Ce}}/{\text{Ce}}^{*}\) increased but \({\text{Eu}}/{\text{Eu}}^{*}\) decreased marginally seaward. The fine-grained sediments showed higher ∑REE and lower Y/Ho ratios than in coarse-grained sediments. The PAAS-normalized REE patterns of sediment were similar to that of SPM. The results revealed two processes, colloidal flocculation and coagulation of metals in the low-salinity zone and an estuarine turbidity maximum in the high salinity zone. Rare earths and yttrium (REY) in SPM and sediments primarily reflected the source rock composition than that of chemical weathering. Apart from physico-chemical processes, the mineralogy and grain size of sediments controlled the distribution and fractionation of REY in the estuary.     

Geochemistry of red residua underlying dolomites in karst terrains of Yunnan-Guizhou Plateau: II. The mobility of rare earth elements during weathering

The aim of this study is to characterize the evolution of the rare earth elements (REE) in the Pingba red residua on karst terrain of Yunnan-Guizhou Plateau. The in-situ weathering and the two-stage development of the profile had been inferred from REE criterions. The REE were significantly fractionated, and Ce was less mobilized and separated from the other REEs at the highly enriched top of the profile. This is consistent with the increase of oxidation degree in the regolith. And it is also suggested that the wet/dry climate change during chemical weathering caused Ce alternative change between enrichment and invariance in the upper regolith. Chondrite-normalized REE distribution patterns for samples from dolomites and the lower regolith are characteristic of MREE enrichment and remarkable negative Ce-anomalies patterns (similar to the convex-up REE patterns). The following processes are interpreted for the patterns in this study: (1) the accumulation of MRRE-rich minerals in dolomite dissolution, (2) water–rock interaction in the weathering front, and (3) more leaching MREE from the upper part of the profile. The latter two explanations are considered as the dominant process for the formation of the REE patterns. Samples from the soil horizon exhibit typical REE distribution patterns of the upper crust, i.e., La_N/Yb_N=10 and Eu/Eu*=0.65. All data indicate that the leaching process is very important for pedogenesis in this region. The experiments demonstrating that abnormal enrichment of REE at the upper regolith–bedrock interface is caused by a combination of volume change, accumulation of REE-bearing minerals, leaching of REE from the upper regolith, and water–rock interaction during rock–soil alteration processes. Our results support the conclusion that the weathering profile represents a large, continental elemental storage reservoir, whereas REE enrichment occurs under favorable conditions in terms of stable tectonics, low erosion and rapid weathering over sufficiently long time.     

中国东部主要河流稀土元素地球化学特征

在2007年底至2008年初的枯水期间,系统采集了中国东部流域面积和径流量较大的33条河流沉积物、悬浮颗粒物和水样,采用等离子质谱法、X荧光光谱法等方法测定了14种稀土元素含量以及常量组分和水体pH值等理化指标。研究发现中国河流稀土元素浓度总体高于世界均值,且南方河流沉积物、悬浮物稀土元素含量高于北方河流,南方河流悬浮物态中稀土、重稀土呈现一定程度的相对富集,与我国上地壳稀土丰度和稀土矿产种类的南北分异相吻合。展示了以中国东部泥质岩稀土元素丰度标准化后的稀土配分模式及Ce、Eu异常特征,发现河流沉积物的中、重稀土元素相对富集,悬浮物轻稀土相对富集,溶解相重稀土富集的特征;北方河流溶解相稀土元素浓度明显大于南方河流,且除小清河外,溶解相Eu不同于沉积物与悬浮物而呈强烈的正异常,主要与河水理化性质影响下的稀土分异有关。研究发现小清河等少数河流沉积物中稀土元素为异常高值,经Al标准化处理、计算拟合剩余值后,认为小清河等河流稀土元素已受人为污染的影响。     

鄱阳湖流域赣江北支水体和沉积物中稀土元素的含量和分异特征

稀土的开发和广泛应用使得人们倍加关注其在环境中的分布及其环境地球化学行为。赣江作为鄱阳湖流域五大入湖河之一,发源于稀土资源富集的赣南地区,而其下游水体及周边地下水中稀土元素的含量和分异特征目前尚不完全清楚。以赣江北支水体及沉积物为研究对象,开展了稀土元素地球化学研究。结果表明,赣江北支水体中稀土元素总量在地表水中为230~1 146 ng/L(均值458.85 ng/L),地下水中为284~1 498 ng/L(均值634.94 ng/L),沉积物中稀土元素总量为177.9~270.7 mg/kg(均值226.99 mg/kg)。PHREEQC模拟计算表明,水体中的稀土元素主要以碳酸根络合物(REEC0₃⁺)的形式存在。地表水和地下水总体上均表现为重稀土元素相较于轻、中稀土元素富集,沉积物未表现出明显的富集特性;水体具有Ce、Eu负异常特点,而沉积物表现为Ce正异常和Eu负异常,指示氧化还原环境和水岩相互作用对稀土元素在水-沉积物系统中迁移转化的影响。地下水中稀土元素的含量沿流向具有上升趋势,而水体中重稀土元素的富集程度不断减弱,同时碳酸根络合物(REEC0₃⁺)的占比不断降低,反映水体中稀土元素的含量受到pH、胶体吸附、络合作用以及地下水-地表水相互作用的影响。水体中重稀土元素的富集受到碳酸根络合反应的影响,Ce、Eu负异常与Ce氧化沉淀和母岩特性相关。Gd异常值表明,研究区中下游水体中的Gd元素受到人为输入的影响。     

喀斯特河流溶解态稀土元素组成变化及其控制因素

以化学萃取- 反萃取分离法为手段,结合等离子质谱分析仪测量了喀斯特地区乌江、沅江两大水系的枯水期河流的溶解态稀土元素含量。该两河流的化学组成代表了流经碳酸盐岩地层的河水的化学组成。与世界其它地区低pH的河水不同,喀斯特地区河水溶解态稀土元素含量较低,页岩标准化配分模式并不平坦,轻、重稀土元素分异因河流的不同而不同,乌江水系上游轻稀土元素( LREE)相对重稀土元素( HREE)富集,中下游HREE相对于LREE富集,沅江水系河水HREE相对于LREE富集,页岩标准化配分模式具明显的Ce、Eu负异常。乌江、沅江及其支流有高的溶解盐,含有较高的溶质浓度,河水水化学(高碱度、高离子含量、高pH值)和水/粒相互作用控制了喀斯特河水中溶解态稀土元素的含量和轻、重稀土元素的分异。      

碳酸盐(岩)的稀土元素特征及其古环境指示意义

稀土元素主要通过交代碳酸盐矿物的Ca^{2+0进入碳酸盐格架,所以沉积碳酸盐(岩}的稀土元素特征能够很好的指示沉积流体来源和古环境。常用的稀土元素指标包括稀土元素总量(ΣREE)、稀土元素配分型式、以及La、Ce、Eu、Gd和Y等元素的异常指数。碳酸盐(岩)的稀土元素含量可能受到硅酸盐矿物、Fe-Mn氧化物/氢氧化物和磷酸盐等非碳酸盐组分以及成岩蚀变作用的影响。因此,在分析过程中,我们只有排除这些影响因素,才能用碳酸盐(岩)的稀土元素指标来探讨流体来源和古环境。这要求我们采集新鲜剖面上的样品,并用适当浓度的弱酸进行分步溶样,提取适当的组分,避免样品中的非碳酸盐组分干扰原始沉积组分的稀土元素特征。不同的沉积水体和沉积相下形成的碳酸盐(岩)具有不同的稀土元素特征:从太古宙到全新世的海相碳酸盐(岩)记录了LREE亏损、La正异常和高Y/Ho值的稀土元素特征;海底孔隙水的稀土元素特征则受氧化-还原条件、离子络合形式、孔隙流体来源的制约;热液流体具有LREE富集、Eu正异常的稀土元素特征;河水和湖泊有相对平坦的稀土元素特征。因此,碳酸盐(岩)的稀土元素特征具有重要的古环境指示意义。     

滇东南中三叠统法郎组含锰岩系稀土元素和铀、钍元素的特征及意义

对滇东南中三叠统法郎组含锰岩系进行了系统采样,用ICP-MS法分析了17件锰矿样品和两件含锰灰岩样品中的稀土元素组成。研究表明,所有样品REE配分模式皆为富LREE型,锰矿样品表现较弱的Ce（δCe值0.79～1.29）异常和Eu（δEu值0.84～1.20）异常;而含锰灰岩则显示出强烈的负Ce异常和较弱的负Eu异常。并通过logTh-logU图解分析,得出滇东南中三叠统法郎组含锰岩系普遍经受了多期次的热液的作用。     

Rare earth element and strontium isotope geochemistry in Dujiali Lake,central Qinghai-Tibet Plateau,China: Implications for the origin of hydromagnesite deposits

Rare earth element (REE) and strontium isotope data (⁸⁷Sr/⁸⁶Sr) are presented for hydromagnesite and surface waters that were collected from Dujiali Lake in central Qinghai-Tibet Plateau (QTP), China. The goal of this study is to constrain the solute sources of hydromagnesite deposits in Dujiali Lake. All lake waters from the area exhibit a slight LREE enrichment (average [La/Sm]_PAAS = 1.36), clear Eu anomalies (average [Eu/Eu*]_PAAS = 1.31), and nearly no Ce anomalies. The recharge waters show a flat pattern (average [La/Sm]_PAAS = 1.007), clear Eu anomalies (average [Eu/Eu*] _PAAS = 1.83), and nearly no Ce anomalies (average [Ce/Ce*]_PAAS = 1.016). The REE+Y data of the surface waters indicate the dissolution of ultramafic rock at depth and change in the hydrogeochemical characteristics through fluid-rock interaction. These data also indicate a significant contribution of paleo-groundwater to the formation of hydromagnesite, which most likely acquired REE and Sr signatures from the interaction with ultramafic rocks. The ⁸⁷Sr/⁸⁶Sr data provide additional insight into the geochemical evolution of waters of the Dujiali Lake indicating that the source of Sr in the hydromagnesite does not directly derive from surface water and may have been influenced by both Mg-rich hydrothermal fluids and meteoric water. Additionally, speciation modeling predicts that carbonate complexes are the most abundant dissolved REE species in surface water. This study provides new insights into the origins of hydromagnesite deposits in Dujiali Lake, and contributes to the understanding of hydromagnesite formation in similar modern and ancient environments on Earth.     

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 PAASnormalized 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 hatshaped REE pattern revealed contributions from the normal marine environment mixed with hydrothermal water to the REE budget of the Gezhongwu phosphorites.     

苏鲁皖新生代玄武岩中巨晶组合的稀土元素特征

我国东部苏鲁皖地区新生代碱性玄武岩中,除了含有大量地幔橄榄岩类捕虏体以外,尚含有一定数量的石榴石、普通辉石和歪长石巨晶。这些巨晶是在地幔不同深度上从玄武岩中晶出的。巨晶组合的分离结晶作用对熔体稀土元素含量有很大影响。赋存巨晶的碱性玄武岩所具有的LREE富集、HREE亏损的稀土元素分配型式是由地幔橄榄岩类部分熔融程度、石榴石巨晶和普通辉石巨晶的早期高压熔离和玄武岩的结晶分异作用等综合因素造成的。     

云南会泽金红铅锌矿区赋矿地层及断裂构造岩稀土元素组成特征

在研究区域地质背景基础上,分析了金红铅锌矿区赋矿地层及控矿断裂构造岩的稀土元素组成特征.按其特征和配分模式得知：赋矿白云岩属于LREE富集-HREE平坦型,轻重稀土分馏程度都较高,Eu异常差异明显,Ce异常差异较大,（La/Yb）_N、（La/Sm）_N和（Gd/Yb）_N值具有一定的差异;断裂构造岩属于LREE富集-HREE平坦型,轻重稀土分馏程度都较高,Eu异常差异微弱,Ce异常差异明显,（La/Yb）_N、（La/Sm）_N和（Gd/Yb）_N值比较相似.以上特征可作为成矿预测的微观标志.     

滇东地区碳酸盐岩上覆风化层的元素地球化学特征及其成因讨论

碳酸盐岩风化形成的红土保存着喀斯特发展演化历史证据,同时也是喀斯特地区土壤研究的重要对象。文章选取云 南石林地区的两处典型碳酸盐岩剖面为研究对象,对主量元素,微量元素及稀土元素在风化层的迁移特征及分布规律进行 研究,为探究风化层的成因提供依据。结果显示：（1） 以Ti为参比元素的剖面迁移特征表明,两剖面的主量元素在成土过 程中有相似的迁移规律,多数表现为淋失;微量元素略有差异,富集淋失程度不一。（2） UCC 标准化蜘蛛图显示,相对于 基岩,风化层中的Ca和Sr均出现亏损;与UCC相比,Fe、Ti等元素轻微富集,Mg、Ca、Na、K、P等元素显示了强烈的亏 损特征。（3） 基岩与风化层的REE分布模式相似,但风化层的稀土相对富集,轻稀土元素间的分异较大而重稀土元素间的 分异较小,且SJC剖面的轻、重稀土元素比值大于QST剖面;稀土元素球粒陨石标准化后,SJC剖面的Eu为负异常,剖面 上部和下部出现Ce负异常;QST剖面Ce负异常,Eu明显负异常。（4） 元素含量变化和元素对Al-Ti、Al-Fe及Zr-Hf相关性 说明剖面上覆红土是下伏基岩风化的结果。研究结果显示,两个剖面的元素地球化学特征与基岩存在很好的继承性,风化 层是基岩原位风化的产物。     

滇东南丘北县大铁铝土矿稀土元素特征研究

本文以丘北大铁铝土矿含铝岩系为研究对象, 通过ICP-MS分析测试, 研究了含铝岩系与下伏灰岩、玄武岩的稀土元素特征。研究结果表明, 丘北大铁铝土矿含铝岩系稀土配分模式曲线为向右倾斜的曲线, 与下伏马平组、黄龙组灰岩的稀土配分曲线相似, 而与峨眉山组玄武岩的稀土配分曲线相差较大; 灰岩具有较明显的Ce负异常和Eu负异常, 部分铝土矿和铁铝质岩具明显的Ce正异常和较明显的Eu负异常, 而多数铝土矿、铁铝质岩和铝质粘土岩则无明显的Ce、Eu异常。含铝岩系的稀土元素特征, 反映出其成矿物质来源于下伏灰岩而非玄武岩, 同时也反映出铝土矿的成矿物质来源于风化壳, 成矿物质搬运距离较近, 与海水的水合作用不甚明显。