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1.
海底热液沉积物稀土元素组成及其意义   总被引:25,自引:0,他引:25  
总结了海底热液及其沉积物的稀土元素组成特征和控制因素。热水沉积物作为热液与海水混合的产物,其稀土元素组成及配分模式随海水混入的比例增加而发生一系列变化,反映了二端元流体不同混合程度的地球化学特征。Eu异常、Ce异常以及w(Y)/w(Ho)比值是用来示踪古流体形成的物理化学环境及流体组成的重要参数。  相似文献   

2.
云南澜沧老厂银多金属矿床是“三江”成矿带南段著名的代表性矿床之一。本文系统研究了矿床中黄铁矿(石)的稀土和微量元素地球化学特征。结果表明:老厂矿床黄铁矿(石)稀土元素总量较低,黄铁矿石EREE平均为5.54×10^6,其单矿物EREE平均仅为0.25×10^6;各类样品稀土配分模式均为明显右倾的轻稀土富集模式,轻稀土分异较强、而重稀土元素分异较弱;黄铁矿石、矿物δEu正异常、δCe负异常和轻稀土富集的配分模式与现代海底热液稀土的十分相似,是成矿流体海底喷流沉积的体现,此外黄铁矿石、矿物还发育弱的δEu负异常,可能是后期岩浆成矿热液叠加改造的结果。矿床黄铁矿单矿物除相对富集少量高场强元素外,其它元素均有不同程度的亏损,其Hf/Sm、Th/La、Nb/La值普遍〈1,表明矿床成矿流体可能是以富cl的成矿热液为主;黄铁矿co、Ni含量较低且变化较大,Co/Ni比值显示矿床经历了不同的成矿阶段,利用Y/Ho比值示踪成矿流体表明,黄铁矿Y/Ho比值与海水及海底热液基本一致,为矿床经历海底火山喷流沉积成矿作用提供了新的佐证。  相似文献   

3.
方解石是湘黔汞矿带的主要脉石矿物。湘黔汞矿带各矿床方解石的稀土配分模式均为轻稀土富集的右倾型,中段的大硐啦、茶田方解石和围岩的稀土配分模式比较相似,只是稀土总量有差别;南段的万山方解石和围岩的稀土配分模式则不一致,围岩的稀土总量反而要高于方解石。南段的万山方解石稀土具有弱的负Eu、负Ce异常;而中段的大硐喇、茶田方解石具有负Eu、正Ce异常。其中,作为示踪流体过程重要参数的Y/Ho比值在湘黔汞矿带南段与中段的方解石中也有着较大的差别。方解石的C、O同位素特征揭示南段万山汞矿的形成与古油藏的有机质有关,而中段大硐喇、茶田汞矿的形成则与有机质无关。这都说明了南段与中段无论是成矿物理化学环境还是成矿热液流体的性质等都存在着较大差别。  相似文献   

4.
鄂尔多斯盆地马家沟组白云岩稀土元素地球化学特征   总被引:3,自引:0,他引:3  
稀土元素具良好的地球化学过程示踪性,且受成岩流体影响小,在分析白云岩化流体性质和白云岩化成岩环境方面具有独特效果。采用中子活化法对鄂尔多斯盆地马家沟组白云岩稀土元素地球化学特征进行研究。结果表明:泥微晶白云岩REE质量分数为(2.907~140.09)×10-6,平均为46.917×10-6,低于泥晶灰岩中的含量,δEu平均为0.634,δCe平均为0.942,配分模式与泥晶灰岩相似,显示该类白云岩形成于低温氧化环境,白云岩化流体为海水或海源流体,可能为准同生白云岩化;晶粒白云岩REE质量分数为(3.392~18.435)×10-6,平均为8.788×10-6,远小于海相泥晶灰岩,δEu平均为0.724,δCe平均为0.78,配分模式与泥晶灰岩相似,且与泥微晶白云岩趋于一致,说明其形成于相对高温还原环境,白云岩化流体为海源流体,可能为埋藏白云岩化;溶蚀残余白云岩REE含量高,配分模式与泥晶灰岩不同且不具Eu正异常,指示岩溶流体可能为大气淡水。  相似文献   

5.
本文采用四极等离子质谱仪(ICP-MS)方法测定了可可塔勒铅锌矿矿物流体包裹体的稀土元素含量。研究表明,成矿流体稀土元素配分模式均为轻稀土富集,Eu具有明显正异常。矿石硫化物流体包裹体稀土特征具有3种稀土配分模式,即平滑右倾型、平坦型、倒“V”字型,矿体下盘围岩的稀土总量明显高于上盘围岩的稀土总量,具有明显的Eu的负异常,成矿流体具有多来源、成矿具有多阶段叠加特点,具有双淋滤模式特征。  相似文献   

6.
黔西南晴隆锑矿区萤石的稀土元素地球化学特征   总被引:9,自引:1,他引:9  
对与辉锑矿共生萤石的稀土元素地球化学特征研究表明,所有萤石均具有Ce负异常,其稀土配分模式存在3种类型:Eu弱亏损型、Eu正常型、Eu富集型。从成矿早期至晚期,萤石的稀土配分从Eu弱亏损型向富集型演化,稀土总量逐渐降低,并由中稀土富集向轻稀土富集演化。成矿流体可能主要属于盆地流体,具有十分低的稀土总量,在成矿作用过程中,成矿流体由早期的还原条件转化为晚期的氮化条件,由中稀土富集向轻稀土富集演化。  相似文献   

7.
对努日矿床白钨矿中稀土元素、微量元素的地球化学特征研究表明:白钨矿亏损V、Cs、Hf、Ta等元素,并具有异常低的Rb/Sr、Zr/Hf、Nb/Ta的比值,以及Hf/Sm、Nb/La、Th/La值也都远远小于1,指示原始富钨成矿流体来源于深部壳源岩浆结晶分异,并总体以富CL热液为主;采自不同位置的白钨矿样品其稀土元素组成基本一致,其球粒陨石配分曲线表现为明显轻稀土富集的右倾模式,具有明显的Ce正异常(δCe=1.066~1.107)和弱Eu负异常(δEu=0.768~0.910),表明白钨矿与流体之间稀土元素发生了不太明显的分异;白钨矿与夕卡岩化有密切关系的黑云母花岗岩的REE球粒陨石标准化配分曲线均为明显的右倾模式,ΣREE、δCe、δEu值基本一致,暗示岩体对努日白钨矿成矿物质的贡献。努日矿床初始热液流体为一中高温、中低盐度的流体,其沿着构造裂隙运移过程中,与比马组地层发生接触交代反应,体系中CO2和Ca含量的增加,流体的初始平衡体系被破坏,最终导致大量Ca2+与WO42-结合形成了巨量的白钨矿。  相似文献   

8.
陕西省略阳县杨家坝多金属矿区成矿作用地球化学示踪   总被引:3,自引:1,他引:2  
本文以陕西省略阳县杨家坝多金属矿区为例,通过对该矿区岩(矿)石和各类脉体的岩相学、稀土和微量元素及流体包裹体地球化学示踪发现,多金属中重晶石的形成及硅化、碳酸盐化、滑石化、纤闪石化、绢云母化和绿泥石化和透闪石岩的含氟浅闪石及隐晶硅质玻璃和微晶硅质,这表明与成矿蚀变有关的热液流体是一种不同于一般地壳流体的富硅、钛、铁、碱质和挥发份,并具备熔体性质的成矿流体。各类样品的稀土元素配分模式明显富集LREE,在Ce、Eu、Yb异常的组合上也各具特征。LREE富集是地幔流体作用的显著特征之一;矿石和脉体的负Ce、正Eu和负Yb异常以及流体包裹体中H2O-C6H6成分,是高温还原地幔流体的重要标志;正Ce和负Eu异常的出现,以及Ce、Eu、Yb异常的减弱和消失则是壳幔混染叠加改造的显示。综合研究表明:矿区成矿过程可能统一受制于秦岭地区碰撞造山背景下具高温还原性质的地幔流体作用,且由此引发壳幔强烈混染的叠加改造作用在成矿过程中发挥了重要作用。  相似文献   

9.
用ICP-MS对冲绳海槽Jade热液活动区中6个块状硫化物样品进行了稀土元素分析。除一个样品表现出极微弱的正Eu异常外(δEu=1.09),其他样品均表现出负Eu异常(δEu=0.58-0.71)和LREE相对富集((La/Yb)N=1.29-47.87)的球粒陨石标准化配分模式。块状硫化物样品之间稀土元素组成的变化是由于热液流体-岩石的相互作用以及海水和热液流体不同程度混合的结果,与深海沉积物,火山岩和海水稀土元素配分模式对比,表明块状硫休物的REE部分来自沉积物和火山岩,海水的混合作用对块状硫化物的REE配分模式具有一定的影响。海底热液硫化物稀土元素组成的变化可以一定程度的反映在出热液流体的演化特征。  相似文献   

10.
陈成业  王钦贤  陈多福 《沉积学报》2022,40(6):1691-1701
菱铁矿很好地记录了过去地质流体的信息,能够用于示踪生物地球化学反应相关的成岩作用带。台湾国姓地区中新世海相泥页岩中发育自生的菱铁矿结核,其成因尚未厘清。野外观察发现菱铁矿以不连续透镜体平行散布于泥页岩中,主要由自生碳酸盐菱铁矿(78.63%)等矿物组成。菱铁矿的稀土元素配分模式为轻稀土亏损、中稀土富集,无Ce异常,指示菱铁矿形成于弱氧化的沉积环境,弱氧化的环境促进了菱铁矿在次氧化带的沉淀。菱铁矿的δ13CVPDB和δ18OVPDB值分别为-3.69‰~+0.08‰和-1.09‰~+0.25‰,指示菱铁矿形成于次氧化带,碳源很可能是海水和有机质降解混合产生。研究表明自生菱铁矿能够被用于识别沉积物中的生物地球化学过程和指示成岩作用带。  相似文献   

11.
罗山金矿床是胶东玲珑金矿田最大的金矿床之一,同时发育蚀变岩型矿化和石英脉型矿化。本研究在系统的野外和镜下工作基础上,利用电感耦合等离子体质谱(ICP-MS)技术分析了载金黄铁矿的微量和稀土元素,对比了蚀变岩型和石英脉型矿石载金黄铁矿稀土和微量元素特征,探讨了成矿流体的性质与来源。黄铁矿稀土总含量较低,多呈较明显的“右倾”式稀土配分模式,总体表现出负Eu异常,基本无Ce异常;Hf/Sm、Th/La、Nb/La值均<1,推断成矿流体为富Cl的还原性流体。Co/Ni比值范围在0.08~3.77,平均值为1.09;Co/Ni值以及Co、Ni、Bi、Cu和Zn含量均与变质热液型金矿平均含量相近;Y/Ho比值范围总体在21~32之间,与中国东部大陆地壳Y/Ho比值(20~35)基本重合;结合个别样品的弱正Eu异常以及前人的研究成果,推断成矿流体与变质热液类似,主要来源于古太平洋板块俯冲板片脱水和脱碳作用,且可能有长英质岩浆流体和地壳流体的混入。蚀变岩型和石英脉型矿石内的载金黄铁矿的稀土、微量元素组成没有明显区别,Y/Ho、Nb/Ta和Zr/Hf比值变化范围均很小,表明两类矿石的载金黄铁矿为同一期热液活动作用的产物。  相似文献   

12.
详细报道了冀东、五台和吕梁地区条带状铁矿全岩样品的稀土元素分析结果。结果表明,研究区BIF具有非常相似的特征:稀土总量均较低;经页岩标准化的稀土元素配分模式均呈现轻稀土亏损、重稀土富集的特征;Y/Ho比值较高;具有明显的Eu、Y、La的正异常,且这些特征表明研究区BIF的稀土元素来源于火山热液和海水的混合溶液。虽然BIF均显示Eu正异常,但不同类型、不同沉积年龄BIF的铕异常程度不同:与吕梁地区Superior型铁矿相比,冀东和五台地区的Algoma型铁矿显示了更大的Eu正异常;并且自中太古代—新太古代—古元古代,BIF的铕正异常逐渐减小,这可能反映了随着BIF沉积年龄的减小,进入到该地区海水中的高温热液流体逐渐减少;同时,研究区BIF缺乏明显的Ce负异常,可能暗示在BIF沉积时海水的氧化还原状态为缺氧环境。  相似文献   

13.
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.  相似文献   

14.
霍什布拉克铅锌矿床是新疆西南天山地区晚古生代碳酸盐岩容矿的重要矿床。本文采用高精度电感耦合等离子质谱(ICP-MS)对主要矿石矿物(黄铁矿、方铅矿、闪锌矿)和热液脉石矿物方解石进行了微量元素地球化学研究。研究表明,黄铁矿、方铅矿、闪锌矿、方解石具有较为相似的稀土元素特征,Eu正异常明显,弱负或弱正Ce异常指示成矿流体最初由相对氧化的条件演化为还原条件。与霍什布拉克岩体、容矿围岩的稀土元素组成进行对比后发现,硫化物及热液方解石稀土元素配分曲线部分与重结晶泥晶灰岩重合,结合前人同位素地球化学研究,认为容矿坦盖塔尔组碳酸盐岩为成矿提供了必要的成矿物质及成矿流体组分。Ga/In值显示闪锌矿为低温成矿;硫化物明显富集LREE,Hf/Sm、Nb/La和Th/La值小于1,显示铅锌成矿过程中成矿流体主体以富Cl为特征;Y/Ho、Zr/Hf和Nb/Ta值变化范围相对较小,表明成矿期流体性质相对较为稳定,基本未混入外来流体。  相似文献   

15.
辽冀地区条带状铁建造地球化学特征:Ⅱ.稀土元素特征   总被引:2,自引:2,他引:0  
辽冀地区(鞍山-本溪地区和冀东地区)位于华北克拉通北东部,是我国早前寒武纪条带状铁建造(BIFs)最重要的分布区,主要为新太古代Algoma型。本文系统对比了辽冀地区28个铁矿床200件铁矿石样品的稀土元素特征。结果表明:(1)所有样品的稀土元素特征比较相似:稀土元素总量较低,Y/Ho比值较高;经太古宙后平均澳大利亚页岩(PAAS)标准化后呈现重稀土相对富集、轻稀土相对亏损的配分模式,La异常不明显,强烈的Eu正异常和明显的Y正异常,暗示研究区铁矿石成矿物质主要来源于海底高温热液和海水的混合溶液;与冀东地区BIFs相比,鞍本地区Eu异常更为明显,说明鞍本地区BIFs显示更多的热液特征;(2)铁矿石的Ce/Ce*变化范围为0.77~1.09,缺乏明显的Ce负异常,说明其沉积于还原的海水环境;(3)辽冀地区BIFs的稀土元素总量、Eu异常、Y异常和Y/Ho比值变化范围均比较大,可能与BIFs沉积过程中碎屑物质的加入有关;与鞍本地区相比,冀东地区BIFs的Eu正异常、Y正异常程度均小于鞍本地区,热液和海水特征均不明显,Y/Ho比值更接近球粒陨石(26~28),可能暗示冀东地区有更多的碎屑物质的加入。  相似文献   

16.
Rare earth element (REE) geochemistry on monomineral has been widely used in various fields of geosciences to reveal the origin of ore-forming materials and fluid. Quartz are ubiquitous mineral in the Shihu gold deposit that is situated in central shear zone of mesocenozoic Fuping metamorphic core complex in the middle-northern part of Taihang Mountains. Gold-bearing quartz veins are their most important industrial orebodies. Rare earth element abundances in quartz from the Shihu gold mine, as determined by laser ablation-indutively coupled plasma-mass spectrometry (LA-ICP-MS) analysis, are shown to be sensitive to identify barren quartz and mineralized quartz. Amounts of REE concentrations in barren quartz and mineralized quartz are 97 × 10−9 and 85 × 10−9, respectively. The average (La/Yb)N and (La/Sm)N ratios for the barren quartz are 0.25 and 0.13, and the ratios for mineralized quartz are 0.28 and 0.19, respectively. There is a pronounced positive correlation between (La/Yb)N and (La/Sm)N ratios. There is no obvious correlation between REE characteristics and sampling sites. The mineralized quartz show the most pronounced negative Ce anomalies, whereas weak negative Ce anomalies are typical of barren quartz vein. A negative Eu anomaly becomes more significant in mineralized quartz than barren quartz. δCe have a broadly positive correlation with δEu. Y/Ho ratio of barren quartz and mineralized quartz are ranging from 2.14–28.75, and from 1.28–9.92, respectively. The REE characteristics of quartz indicate that the ore-forming fluids of the gold deposit were derived from the deep fluid and its formation was dually controlled by Precambrian metamorphic basement and Mesozoic granitoids. The results significantly enhance the usefulness of quartz in tracing the sources of ore-forming fluid to discuss the genesis of the gold deposit, and as an indicator mineral in mineral exploration in Taihang mountain region.  相似文献   

17.
川北元坝气田二叠系长兴组49个碳酸盐岩样品的稀土元素(REE)和钇(Y)含量的测试结果表明:稀土元素总量(ΣREE)普遍较低(平均1.50×10-6),说明岩石样品几乎无陆源碎屑的混入,且未受到深部热液的影响。页岩标准化后的白云岩REE特征表现为轻稀土(LREE)亏损、正La异常、负Ce异常(0.49~1.08,平均0.75)、普遍的正Eu异常(0.89~46.00,平均4.68)及较高的Y/Ho值(28.82~63.47,平均43.04),总体表现出与海水的REE配分特征类似,表明白云化流体为还原性的海源流体,白云岩形成环境为埋藏环境。元坝气田长兴组构造平缓,白云岩横向上连续分布,碳酸盐岩δ18O(-7.07‰~-2.92‰,平均-4.95‰)相对较重,岩心与岩石薄片未观察到角砾状或条带状的热液白云岩典型构造,均说明元坝气田长兴组未受到深部热液流体的影响,白云岩较高的正Eu异常与深部热液流体无关;电子扫描显微镜下观察到大量的热化学硫酸盐还原反应(TSR)的产物单质硫和富硫沥青,表明元坝气田长兴组基质白云岩形成之后的TSR作用导致了地层水极度还原的环境,从而造成了白云岩较高程度的正Eu异常,反过来说明了TSR作用对白云岩储集层具有一定的改造作用。  相似文献   

18.
Rock samples representing various igneous and metamorphic rocks of southern Obudu Plateau were analyzed for rare-earth element ( REE ) behavior by ICP-MS. Results of the analyses indicate a range of REE abundances and distinctive patterns from highly fraetionated patterns with negative Eu anomalies in granitic rocks to relatively low abundances and less REE fractionated flat patterns with little Eu anomaly in some paragneisses, schists, enderbites and dolerites to unfractionated patterns with positive Eu anomalies in some paragneisses and charnockites. Over all, there are low to high ∑ REE contents with negative to positive Eu anomalies. The ratios of different parameters, especially La/Yb and Ce/Yb, show behaviors consistent with crustal to mantle derivation. The heterogeneity of REE abundances and REE patterns reflects mantle to crustal petrogenetic variations of different rock suites on the Plateau. The LREE content is higher than the HREE content in the highly differentiated rocks, as evidenced by their La/Yb,Ce/Yb and La/Sm ratios, which are normally higher in residual products than in primary melts. The dominantly intermediate nature of the source rock of the orthogneisses is suggested by the generally low ∑ REE. The granites enriched in LREE and depleted in HREE and some of the charnockites with negative Eu anomalies were probably formed by partial melting and crystallization.  相似文献   

19.
The iron isotope, trace and major element compositions of Eoarchean supracrustal rocks from southern West Greenland (Isua Supracrustal Belt, the islands of Akilia and Innersuartuut) were analyzed in order to identify protoliths and characterize the imprints of metamorphism and metasomatism. Banded iron formations (BIFs) from the Isua Supracrustal Belt (ISB) have trace element characteristics that are consistent with seawater derivation, including high Y/Ho ratios, positive Eu/Eu anomalies, positive La/La anomalies, and concave upward REE patterns. These rocks also have heavy Fe isotopic compositions relative to surrounding igneous rocks (∼+0.4‰/amu). The most likely interpretation is that this signature was inherited from partial oxidation in a marine setting of Fe emanating from a source similar to modern mid-ocean ridge hydrothermal vents (∼−0.15‰/amu).Banded quartz-rich rocks from the island of Akilia with high Fe/Ti ratios share many similarities with bona fide BIFs from Isua (heavy Fe isotopic compositions up to +0.4‰/amu, elevated Y/Ho ratios compared to igneous rocks, sometimes positive Eu/Eu anomalies) suggesting a chemical sedimentary origin.Iron-poor metacarbonates from the southwestern part of the ISB have light Fe isotopic compositions (∼−0.4‰/amu). This is consistent with derivation of these rocks by fluid flow through surrounding ultramafic rocks and deposition as metasomatic carbonates. Iron-rich metacarbonates from the northwest and northeast parts of the ISB have Fe isotopic compositions (from +0.1 to +0.4‰/amu) and trace element patterns (high Y/Ho ratios, positive Eu/Eu and La/La anomalies, and concave upward REE) similar to associated BIFs. The most likely interpretation is that these iron-rich metacarbonates were derived from mobilization of Fe in BIFs by metasomatic fluids.  相似文献   

20.
辽宁弓长岭铁矿床磁铁矿稀土元素特征及其地质意义   总被引:4,自引:0,他引:4  
辽宁弓长岭铁矿床是我国著名的沉积变质型铁矿床,其二矿区的磁铁富矿达大型规模,属国内之最.为探讨弓长岭铁矿床铁矿的物质来源、形成环境和富矿成因,本文以二矿区六个铁矿体的贫铁矿石和富铁矿石中磁铁矿单矿物为研究对象,利用电感耦合等离子体质谱进行了系统的稀土元素测试.结果表明,所有样品中磁铁矿的稀土元素总量(∑REEs)和Y具有非常一致的特征:稀土元素总量较低,Y/Ho比值较高;经太古界后平均澳大利亚页岩( PAAS)标准化呈现重稀土相对富集、轻稀土相对亏损的分馏模式,大部分呈现La正异常,所有样品都有明显的Eu和Y正异常,这些特征表明研究区的磁铁矿成矿物质主要来源于海底高温热液和海水;虽然磁铁矿的Ce/Ce*为0.69~ 0.97,但大多数样品缺乏真正意义的Ce负异常,这暗示其沉积于还原的海水环境;富铁矿石磁铁矿的稀土元素总量和Eu含量明显高于贫铁矿石的磁铁矿,而且含富矿的上含铁带Eu异常明显较高,表明富铁矿石磁铁矿具有更明显的热液特征,是在贫铁矿石的基础上受热液活动形成的.  相似文献   

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