粤北丹霞盆地上白垩统丹霞组锦石岩段顶部泥岩岩石地球化学特征及其地质意义

丹霞山是“中国丹霞”世界自然遗产的典型代表,目前对其成景地层上白垩统丹霞组沉积环境的研究程度不高,尤其对锦石岩段沉积环境还存在较大争议。锦石岩段以厚层—巨厚层状中-粗砂岩为主,发育大型交错层理,夹中薄层—极薄层状泥岩、粉砂质泥岩以及钙质层。本次采集的锦石岩段顶部中层状泥岩样品的黏土矿物成分以伊利石为主,稀土总量较高,ΣREE = 191.19×10^-6～308.73×10^-6,轻、重稀土分异明显,轻稀土富集,δEu = 0.52～0.63,负异常明显,δCe = 0.91～1.27,Ce无异常,古盐度 = 10.74‰～16.21‰、B/Ga = 3.89～5.04、V/（V+Ni）= 0.74,代表了在干旱到半干旱的气候环境下,缺氧条件下的半咸水沉积水体,可能与晚白垩世中期Campanian期东亚中纬度地区的干旱古气候条件相关。短期有淡水注入,可能与其暂时性河道发育有关。La/Yb-ΣREE图解和Hf-La/Th图解研究表明,丹霞组锦石岩段泥岩的母岩物质成分以长英质和基性岩为主,具有岛弧属性。     

阿勒泰萨热阔布金矿的成矿流体：微量元素组成

阿勒泰萨热阔布金矿包裹体的ICP-MS稀土元素研究表明，ΣREE比中国其他造山型金矿的高几倍；轻、重稀土分馏不明显，轻稀土和重稀土内部分异也不明显；无明显的Eu异常（δEu=0.72~1.77），与地幔岩辉石的CO₂流体相似。流体中富集的微量元素有Cu、Zn、Mo、Cd、Se、Pb、W、Bi等，与矿物的共生组合一致，结合硫同位素组成反映了深源特征。     

鄂尔多斯盆地盐56井长7段泥页岩稀土元素地球化学特征分析

鄂尔多斯盆地三叠系延长组长7段发育优质烃源岩,通过对盆地西部盐56井长7段泥页岩系统取样及稀土元素室内测试分析,结果表明：盐56井长71、长72、长73段稀土元素总量较高,均明显高于北美页岩,∑LREE/∑HREE、LaN/YbN比值显示轻重稀土分异明显,REE配分模式为明显的轻稀土富集、重稀土平坦及显著 Eu负异常右倾形态。根据REE配分模式,表明长7段泥页岩物源来自上地壳岩石;根据长7段各小层较高 REE总量及Ceanom均大于-0.1,显示长7段沉积期气候温暖湿润且水体为还原环境,且长73沉积期气候更为湿润,水体还原性更强。     

内蒙古因格井坳陷湖相白云质泥岩地球化学特征及地质意义

本文对内蒙古巴音戈壁盆地因格井坳陷下白垩统音戈壁组上段湖相白云质泥岩进行了地球化学分析,据此探讨了其 对构造背景、源岩属性及古沉积环境重建的意义。研究表明：白云质泥岩具有富Ca,Na,Sr,U,V 元素,贫K,P,Ba, Rb,Sc,Th,Zr 元素的特点;稀土元素总量变化范围大（59.29×10-6~283.80×10-6）,轻、重稀土分异明显,δEu 为中等偏 强的负异常（平均值0.62）,δCe 无异常（平均值1.01）。构造判别图解及δEu 异常特征共同指示白云质泥岩源岩具有大陆岛 弧和主动大陆边缘构造背景。稀土配分模式及源岩属性判别图解指示白云质泥岩源岩以上地壳长英质岩石为主。垂向上巴 音戈壁组上段整体为干旱、厌氧、偏强还原的咸湖环境。古气候、古盐度及氧化还原指标在巴音戈壁组上段中部和下部界 面变化明显。在下部（K1b2-1） 干热环境下出现过相对湿冷的沉积过程,古盐度、氧化还原环境也均与干热-冷湿演化具有 耦合性,即在厌氧的、偏强还原的咸湖沉积环境下存在短暂的氧化环境。     

斯里兰卡普塔拉姆地区ZK593号钻孔沉积物的地球化学特征及意义

根据岩性、主微量元素特征和元素比值分析,斯里兰卡普塔拉姆地区ZK593钻孔的沉积物可分为6段。它们分别沉积于温暖潮湿、水动力较强的浅海-滨海相环境,经历了3次明显的海水进退。各层北美页岩标准化曲线平缓,轻重稀土元素没有明显的分异,Ce轻度亏损,球粒陨石标准化曲线斜率为负,轻稀土元素相对富集,各层Eu亏损明显,Ce轻度亏损,表明沉积物属于受陆源影响的陆棚沉积物。Ce负异常与碳酸盐沉积及气候环境有关。元素相关系数分析表明,Ca和Sr与生物作用关系明显;ΣREE与Al₂O₃和SiO₂等微量元素与陆源碎屑关系密切。δ¹⁸ O 的负向偏移与沉积后地下水的作用有关。     

稀土元素指标δCe－ΣREE对沉积相的指示研究

通过对内蒙古额济纳盆地小狐山剖面沉积物中酸溶组分稀土元素含量及其相关指标、分布模式的分析,讨论了剖面中稀土元素指标δCe－ΣREE与沉积相、沉积环境之间的关系。分析结果表明剖面沉积物酸溶组分中稀土元素丰度均值为7.24μg/g(不包括Y),其中LREE含量占稀土总量的88.67%; 且各层的稀土分布模式均为轻稀土适度富集缓右倾斜型、Eu呈负异常模式,但各相位地层的LREE富集程度与分配模式存在差异。由于小狐山剖面中沉积地层的自身岩性、沉积粒径、矿物结构组成以及气候环境变化等因素均可能会引起REE分异。因此,通过δCe－ΣREE图并结合三次回归曲线,可以很好地将不同沉积相得物质有效的区分开来。小狐山剖面除极少数的几个样品(水下沉积砂)之外,其余的均落在三次多项式回归曲线上部; 而风成砂层则几乎全部落在回归曲线之下; 此外,对于风沙－河流作用下的混合样品也有较好识别,河流过渡相的样品则分布在曲线上或与之相邻近。此研究结果得到了柴达木贝壳堤沉积物的REE数据的验证,运用此方法可以为直观的判别剖面中的不同沉积相,并为定量化划分地层提供依据。     

河南小秦岭金矿稀土元素地球化学特征及地质意义

小秦岭金矿产于新太古界太华群变质岩中,其中的次级拆离断裂为赋矿构造。为了探究矿床的地球化学特征和矿床成因,从矿区主要地质体采集了100件来自太华群地层、文峪岩浆岩和矿石的样品进行测试,其稀土元素的主要特征为：太华岩群的ΣREE值为30.81×10^-6~188.66×10^-6;δEu值为0.62~1.24;花岗岩和脉岩类ΣREE值为58.22×10^-6~365.98×10^-6;δEu为0.90~1.10;矿石的ΣREE值多集中于76.74×10^-6~358.22×10^-6,δEu值多集中于0.74~1.14。结果表明：各地质体稀土总量接近,没有Eu异常或有微弱的正、负铕异常;矿石的稀土元素含量特征与太华群接近,而与文峪等花岗岩相差较远。分析认为,成矿物质主要来源于太华群地层而不是花岗岩。     

珠江三角洲晚第四纪风化层稀土元素地球化学特征*

珠江三角洲地区上更新统与全新统之间广泛发育1层杂色黏土,其成因多认为主要是由上更新统沉积物在末次冰盛期暴露于地表风化而成。对取自珠江三角洲3条钻孔（PRD09、PRD16和PRD17）的岩心样品分析表明,受风化作用的影响,其稀土元素含量和分异特征发生了较明显的变化。杂色黏土层的稀土总量大大低于下伏沉积物,而在邻近风化层的下伏沉积物中稀土元素却表现为明显富集,尤其是重稀土元素的富集。风化作用强度较大的PRD09孔和PRD17孔下伏沉积物中的稀土富集程度高于风化作用强度相对较小的PRD16孔。珠江三角洲在末次冰盛期时普遍发育的酸性介质条件,促进了风化层的稀土元素发生溶解和迁移。在风化过程中,由于轻、重稀土元素具有不同的溶解迁移能力和吸附能力,导致杂色黏土层的REE指标值（LREE/HREE、(La/Gd)_N和(La/Yb)_N）高于下伏沉积物。风化过程对Ce、Eu异常有一定的影响,但不十分明显,杂色黏土层的Ce、Eu异常值仅略低于下伏沉积物。     

宝应钻孔沉积物的微量元素地球化学特征及沉积环境探讨

沉积物微量元素特征对指示沉积盆地演化历史、沉积环境及沉积物的物质来源具有十分重要的示踪作用.宝应沉积物的微量和稀土元素地球化学特征印证了苏北平原物质来源具有多源性,与黄河、长江具有类似的物源,并可能受基底碱性火山岩和黄土高原粉尘物质的影响.钻孔沉积物具有轻稀土适度富集、缓右倾斜型的稀土元素配分模式,呈现Ce正异常的总体特征; 海侵段的稀土含量比陆相沉积段略低.δEu在陆相沉积中为1.16,呈微小的正异常; 在海侵沉积中为0.99,基本不显示异常.稀土元素含量与沉积物粒度之间存在一定相关性:随着粒度由粗变细,稀土元素含量增加; ΣREE的高值段对应粘土含量较高,反之亦然.沉积物REE及Rb/Sr比值的纵向变化反映了海陆交互过渡带古气候环境的波动:ΣREE的高值段与δEu和δCe的低值段代表了冷湿的气候环境; ΣREE和δCe的低值与δEu的高值段反映了暖湿润的环境信息.结合地貌、岩性及微体古生物,综合分析表明苏北平原在第四纪曾遭受了多次海水淹覆, 海-陆交互堆积作用明显,从古海湾逐渐发育堆积最后由河流冲积物覆盖成陆.     

渤海湾盆地石炭二叠系稀土元素特征及其地质意义

采集了渤海湾盆地周缘露头剖面和盆内钻井岩心的泥岩及少量灰岩样品,采用电感耦合等离子质谱技术对样品进行了系统的稀土元素测试分析。测试样品稀土总量平均值为290.39 μg/g ,明显大于北美页岩组合样。各样品δEu为0.42~0.83,平均0.67,中度Eu负异常;大多样品Ce含量正常,δCe为0.51~1.22,平均0.97。稀土元素配分模式总体为轻稀土富集、重稀土亏损型,轻稀土段曲线明显“右倾”,重稀土段则较为“平坦”。灰岩及部分泥岩中Ce的负异常指示了晚石炭世本区陆表海的沉积环境特点,古海水为氧化环境。根据稀土元素的Eu异常及总的元素组合特点,判断渤海湾盆地石炭—二叠系沉积物主要来自盆地北缘的阴山古陆,母岩类型为花岗岩。     

黄河沉积物中稀土元素(REE)组成的粒度效应*

依据Stokes颗粒沉降原理将黄河利津水文站和汊河清八站的表层沉积物分别提取为<2μm,2~4μm,4~8μm,8~16μm,16~32μm和32~63μm的6个粒级,采用ICP-MS法对各个粒级沉积物的15个稀土元素进行测试。结果表明:黄河沉积物两个样品REE含量随粒度增大的变化趋势有细微差别,但总体随粒度大小呈"高—低—高"的不对称马鞍型分布,其中最高REE含量和最低REE含量分别位于<4μm的粘土粒级和4~16μm细粉砂粒级中; 各粒级沉积物经北美页岩标准化后,REE的配分模式一致,呈平缓的右倾型,相对富集轻稀土,明显的Eu正异常和Ce负异常。对各个粒级样品进行X射线衍射分析及体视镜下观测,石英含量随粒级增大而增加, 长石在8~16μm中含量最高,在16~32μm中,碳酸岩含量最高,随着粒级增大,重矿物含量逐渐增加,黄河沉积物REE随粒度的变化特征与粘土矿物对其吸附及流域碎屑沉积物不同粒级的矿物成分密切相关。     

南黄海NT1孔沉积物稀土元素组成与物源判别

为研究黄河、长江以及韩国河流输运的大陆物质对南黄海沉积的贡献,对南黄海中部泥质区NT1孔沉积物做了稀土元素分析和物源判别。研究发现,南黄海NT1孔沉积物物源主要为长江源和黄河源,NT1孔上部0—7．70m沉积物以长江源为主,中部7．70．16．60m和40．00～50．70m沉积物以黄河源为主,其间夹近24m厚的沉积物则以长江源为主,底部50．70～69．76m沉积物以长江源为主。结果表明,长江从晚更新世早期到现代对南黄海中部泥质区沉积起着主要作用,而黄河则在晚更新世晚期的早玉木冰期时已开始对南黄海陆架沉积作用有明显影响。     

北京平原沉积物稀土元素地球化学特征及物源意义

文中总结了北京平原永定河、潮白河流域钻孔沉积物中稀土元素分布特征,两流域沉积物稀土元素总量∑REE、轻重稀土比(LREE/HREE)及轻(La/Sm)N、重(Gd/Yb)N稀土分馏特征差异较为显著。粒度对沉积物稀土分布(总量、轻重稀土比及分馏特征)有一定影响;各流域沉积物均表现为轻稀土相对富集、弱Eu负异常的球粒陨石标准化曲线。细颗粒沉积物稀土分馏特征(La/Yb)N有较好的物源示踪意义。根据沉积物(La/Yb)N值对永定河、潮白河交互沉积区不同深度沉积物进行了物源示踪,不同深度上沉积物来源不同。此外,同一流域上、中、下游沉积物稀土分馏特征不同。常量元素Al2O3/Fe2O3与稀土元素(La/Yb)N划分结果相符,但精度低于稀土元素物源分析。     

Fractionation characteristics of rare earth elements (REEs) linked with secondary Fe,Mn, and Al minerals in soils

Soil secondary minerals are important scavengers of rare earth elements (REEs) in soils and thus affect geochemical behavior and occurrence of REEs. The fractionation of REEs is a common geochemical phenomenon in soils but has received little attention, especially fractionation induced by secondary minerals. In this study, REEs (La to Lu and Y) associated with soil-abundant secondary minerals Fe-, Al-, and Mn-oxides in 196 soil samples were investigated to explore the fractionation and anomalies of REEs related to the minerals. The results show right-inclined chondrite-normalized REE patterns for La–Lu in soils subjected to total soil digestion and partial soil extraction. Light REEs (LREEs) enrichment features were negatively correlated with a Eu anomaly and positively correlated with a Ce anomaly. The fractionation between LREEs and heavy REEs (HREEs) was attributed to the high adsorption affinity of LREEs to secondary minerals and the preferred activation/leaching of HREEs. The substantial fractions of REEs in soils extracted by oxalate and Dithionite-Citrate-Bicarbonate buffer solutions were labile (10 %–30 %), which were similar to the mass fraction of Fe (10 %–20 %). Furthermore, Eu was found to be more mobile than the other REEs in the soils, whereas Ce was less mobile. These results add to our understanding of the distribution and geochemical behavior of REEs in soils, and also help to deduce the conditions of soil formation from REE fractionation.     

Rare Earth Elements in the Bottom Sediments of the East Arctic Seas of Russia as Indicators of Terrigenous Input

The REE distribution was studied in the bottom sediments of the East Arctic shelf of Russia. It is established that sediments of the Laptev and western East Siberian seas are significantly enriched in REEs, the contents of which are much higher than those of other near-continental basins. The main REE sources are runoff of the Lena River, the basin of which comprises ancient crystalline shields and magmatic rocks enriched in LREEs with significant contribution from the coastal erosion of the ice complex from the Laptev Sea and western East Siberian Sea. The terrigenous flux with a specific REE composition is supplied to the Chukchi Sea through the Bering Strait.     

Trace elements and REE fractionation in subsoils developed on sedimentary and volcanic rocks: case study of the Mt. Vulture area,southern Italy

There is an increasing interest in the distribution of rare earth elements (REEs) within soils, primarily as these elements can be used to identify pedogenetic processes and because soils may be future sources for REE extraction, despite much attention should be paid to the protection and preservation of present soils. Here, we evaluate the processes that control the distribution of REEs in subsoil horizons developed over differing lithologies in an area of low anthropogenic contamination, allowing estimates of the importance of source rocks and weathering. Specifically, this study presents new data on the distribution of REEs and other trace elements, including transition and high-field-strength elements, in subsoils developed on both Quaternary silica-undersaturated volcanic rocks and Pliocene siliciclastic sedimentary rocks within the Mt. Vulture area of the southern Apennines in Italy. The subsoils in the Mt. Vulture area formed during moderate weathering (as classified using the chemical index of alteration) and contain an assemblage of secondary minerals that is dominated by trioctahedral illite with minor vermiculite. The REEs, high-field-strength elements, and transition metals have higher abundances in subsoils that developed from volcanic rocks, and pedogenesis caused the Mt. Vulture subsoils to have REE concentrations that are an order of magnitude higher than typical values for the upper continental crust. This result indicates that the distribution of REEs in soils is a valuable tool for mineral exploration. A statistical analysis of inter-elemental relationships indicates that REEs are concentrated in clay-rich fractions that also contain significant amounts of low-solubility elements such as Zr and Th, regardless of the parent rock. This suggests that low-solubility refractory minerals, such as zircon, play a significant role in controlling the distribution of REEs in soils. The values of (La/Yb)_N and (Gd/Yb)_N fractionation indices are dependent on the intensity of pedogenesis; soils in the study area have values that are higher than typical upper continental crust ratios, suggesting that soils, especially those that formed during interaction with near neutral to acidic organic-rich surface waters, may represent an important source of both light REEs and medium REEs (MREEs). In comparison, MREE/heavy REE fractionation in soils that form during moderate weathering may be affected by variations in parent rock lithologies, primarily as MREE-hosting minerals, such as pyroxenes, may control (La/Sm)_N index values. Eu anomalies are thought to be the most effective provenance index for sediments, although the anomalies within the soils studied here are not related to the alteration of primary minerals, including feldspars, to clay phases. In some cases, Eu/Eu* values may have a weak correlation with elements hosted by heavy minerals, such as Zr; this indicates that the influence of mechanical sorting of clastic particles during sedimentary transport on the Eu/Eu* values of siliciclastic sediments needs to be considered carefully.     

中国东部大陆尺度地球化学走廊带碳酸盐岩稀土元素分布特征与影响因素

碳酸盐岩是地球表层岩石圈的重要组成部分,其化学组成可提供沉积环境与海洋水体演化等信息,然而,前人对碳酸盐岩中稀土等元素的分布与变化特征关注不足。本文选择穿越中国东部6个一级大地构造单元的3条地球化学走廊带,系统采集了582件碳酸盐岩地层样品,并准确分析了包括稀土元素(REE)在内的81项指标的含量。结果表明,中国东部地球化学走廊带碳酸盐岩稀土元素(REE＋Y)总量为(0.59～183)×10-6,均值为24.0×10-6,纯净碳酸盐岩(CMC含量≥99％)均值为4.80×10-6。PAAS标准化后其显示具有轻稀土相对于中稀土和重稀土略亏损、δEu轻微正异常、δCe中度负异常等特征。白云岩中稀土含量、LREE/HREE值一般低于石灰岩;砂泥质含量相近时,前中生代各时代碳酸盐岩稀土分布模式相差不大,各构造单元稀土分布特征基本相似;与其他时代相比,中生代及中新元古代碳酸盐岩具有相对较平坦的稀土分布模式。研究表明,碳酸盐岩中稀土分布受碎屑物质影响明显,表现为稀土元素含量与碳酸根负相关,与碎屑物质相关元素(Si、Ti、Rb、Cs、Th、Zr等)、黏土相关元素(Al、Fe、K等)等正相关。成岩过程及白云化过程对较纯净碳酸盐岩中稀土分布特征影响不明显。我国古生代纯净碳酸盐岩分布模式受控于海相环境,其分布模式与现今海水相近;中生代纯净石灰岩受到陆相或海陆交互相的影响,具有较平坦的稀土分布模式。氧化还原条件对δCe的影响较δEu更为明显,δCe值受海相环境控制,极端正异常值(δCe＞1.3)受到还原环境或/和热液影响。若假定海水中REE自中元古代至今无太大变化,各时代稀土元素分配系数均值介于103.55～102.39,分配系数差异是造成碳酸盐岩中轻稀土亏损、Ce负异常及Y正异常的主要原因。微生物(席)可富集稀土等金属元素并改变沉积环境,这可能是造成中新元古界碳酸盐岩较平坦的稀土分布模式的主要原因。     

Rare-earth elements in Luochuan loess section,Shaanxi province

TheΣ REE in loesses of different ages in the Luochuan section shows a narrow range of variation, indicating the homogeneity of loessic materials in chemical composition. The REEs in loess are concentrated mainly in silt-sized detrital minerals. Loesses and paleosols of different ages all are relatively enriched in rare-earth elements of the Ce family, and show similar REE distribution patterns. The fractionation among various REEs in the loess is different from that in morainic, marine and lacustrine sediments, but is similar to that in sand samples from deserts in Northwest China. The ratios of Ce/Ce* and Eu/Eu* reflect that the provenance of loessic materials and their accumulating area are all in an oxidation environment with weakly basic mediums under arid or semi-arid climate.     

REE geochemistry of the recent playa sediments from the Thar Desert, India: An implication to playa sediment provenance

The playas (saline lakes) situated in the Thar Desert, north-west India, provide prominent examples of alkaline brine and varying assemblages of detrital and evaporite mineralogy. The eastern margin of the desert is relatively semi-arid, whereas the central to western region is arid to hyper-arid in nature. Rare earth elements (REEs) systematics in the sediments of nine different playas of the Thar Desert were studied to understand the provenance of the sediments and the intensity of chemical weathering in the region. Based on the REE patterns, fractionation of light REE (LREE) (La/Sm)_N and heavy REE (HREE) (Gd/Yb)_N, and Eu anomaly (Eu/Eu*), the upper continental crust normalised playa sediments are divided into two different groups. The eastern margin playa sediments show homogeneous REE contents, relatively positive Eu anomaly and depleted HREE values, whereas the western arid core playa sediments have highly variable REE contents, relatively negative Eu anomaly and similarly fractioned LREE and HREE patterns. The dissimilarity in the degree of HREE fractionations both in the eastern and western playa sediments is attributed to the differential distribution of minerals, depending upon their resistance to chemical weathering. It is believed that the relatively higher abundance of REE bearing heavy minerals and the presence of higher amounts of evaporites influence the large variation of REE distribution and enriched HREE in the western playa sediments. Apart from the relatively higher abundance of heavy minerals, the presence of rock fragments of variable petrographic character and roundness mirror the lower rock–water interaction in the arid western region. The presence of well-rounded metamorphic rock fragments and minerals, sourced from the eastern margin Aravalli mountains, indicates that the playas of the entire desert get the detrital and dissolved material mainly from the Aravalli mountains. Additionally, the western playas receive sediments from their surrounding Proterozoic and Mesozoic formations. This interpretation is supported by the presence of angular rock fragments of basalt, rhyolite and limestone in the western playas.