黔西北地区铅锌矿床成矿流体起源与运移方向初探

黔西北地区已发现中-小型矿床(点)100余处,它们的分布严格受到区域性构造的控制,是研究大规模成矿流体运移途径的理想场所。本文在系统收集前人资料的基础上,对黔西北地区铅锌矿床成矿流体的起源与运移方向进行了深入的探讨。天桥硫化物的(87Sr/86Sr)200 Ma为0.7118~0.7130(均值0.7123,n=7),筲箕湾闪锌矿的(87Sr/86Sr)200 Ma为0.7113~0.7129(均值0.7120,n=5),青山闪锌矿及其包裹体的(87Sr/86Sr)200 Ma为0.7099~0.7126(均值0.7111,n=8),杉树林闪锌矿的(87Sr/86Sr)200 Ma为0.7107~0.7115(均值0.7113,n=7),银厂坡热液方解石和矿石全岩的(87Sr/86Sr)200 Ma为0.7108~0.7255(均值0.7152,n=8)。可见,受NE向构造控制的银厂坡矿床最富放射性成因Sr,而受NW向构造控制的矿床其Sr同位素组成从NW的天桥向SE的杉树林呈现逐渐降低的趋势。经与地幔、峨眉山玄武岩、赋矿地层沉积岩和基底岩石的Sr同位素组成特征对比,发现黔西北地区铅锌矿床的成矿流体来源或流经了富放射性成因Sr的基底岩石。综合以往地质、地球化学资料,本文认为黔西北地区铅锌矿床成矿流体的运移方向至少可分为3组,即起源或流经基底岩石的富金属成矿流体沿NE或近EW向构造运移,起源或流经赋矿地层沉积岩的富金属成矿流体沿NW向构造向SE向运移,而起源于赋矿地层沉积岩的富硫成矿流体则沿NW向构造向NW方向运移。多组流体大规模运移过程中在有利的构造空间发生流体混合,形成矿(化)体,应加强构造流体复(耦)合部位的成矿和找矿相关研究工作。     

四川天宝山铅锌矿成矿物质来源与成矿机制：来自流体包裹体及同位素地球化学制约

天宝山铅锌矿床位于扬子地台西缘,为川滇黔铅锌矿集区具有代表性大型铅锌矿床,其金属储量(Pb+Zn)可达2.6Mt,铅锌品位10%～15%。本文在系统的分析流体包裹体和C、H、O、S、Pb、Sr同位素研究的基础上,确定其成矿物质来源、成矿流体性质及来源,并探讨其成矿机制。H-O同位素及流体包裹体研究表明,成矿流体具有中低温(均一温度峰值为140～200℃)及中低盐度(盐度峰值为6%～12% NaCleqv)的特征。灯影组白云岩与海相沉积碳酸盐岩的C、O同位素组成较为相似,热液方解石与含矿白云岩O同位素组成均稍低于灯影组白云岩,表明成矿流体中的CO_2可能来源于海相碳酸盐岩的溶解。矿区硫化物δ~(34)S值介于1.1‰～7.5‰之间,表明S主要来源于灯影组中硫酸盐热化学还原作用和岩浆硫的混合。矿石硫化物的Pb同位素比值在Pb演化图解上主要落入上地壳与造山带之间,表明Pb具有壳源特征,成矿物质来源主要来自于盖层沉积岩和基底地层。闪锌矿的~(87)Sr/~(86) Sr值(0.71099～0.71856)及热液方解石~(87)Sr/~(86) Sr值(0.71014～0.71169)均高于灯影组白云岩~(87)Sr/~(86) Sr值(0.70773～0.71026),表明成矿流体流经了具有高~(87)Sr/~(86) Sr值的基底地层,并与其发生水岩反应及同位素交换。     

四川甘洛铅锌矿集区闪锌矿Rb-Sr等时线年龄及其地质意义

四川甘洛铅锌矿集区位于扬子地块西南缘的川滇黔铅锌成矿带北段,是四川主要的铅锌产地,具有重要经济价值。为研究该矿集区铅锌成矿时代、成矿大地构造背景和成矿机制,以支撑区域找矿勘查,在区内选择赤普和尔呷地吉两个典型铅锌矿床开展闪锌矿Rb-Sr同位素体系研究,获得Rb-Sr等时线年龄246 ± 17 Ma（MSWD= 2.3）,表明区内铅锌矿化作用发生于早三叠世,与古特提斯洋闭合时限吻合;闪锌矿(87Sr/86Sr)i值变化于0.71061~0.71393,高于幔源87Sr/86Sr值0.70355及峨眉山玄武岩87Sr /86Sr值0.704979~0.706938,低于基底岩石87Sr /86Sr值0.7243~0.7288,暗示成矿物质主要来源于地壳。综合前人研究,认为在古特提斯洋闭合背景下,强烈造山运动诱发盆地卤水深循环并萃取基底地层中的成矿物质,在峨眉山玄武岩岩浆活动的热动力条件下,含矿流体沿马拉哈断裂进一步迁移沉淀形成了赤普和尔呷地吉铅锌矿床。马拉哈深大断裂及造山作用派生的层间或断层破碎带、碳酸盐岩地层是甘洛地区主要的控矿要素。     

扬子陆块北缘冰洞山铅锌矿床闪锌矿Rb-Sr定年及其地质意义

为探讨冰洞山铅锌矿床成矿物质来源,采用全溶方法和流体包裹体淋滤法对主成矿期闪锌矿进行Rb、Sr同位素分析,获得等时线年龄为507.7~507.8Ma,初始锶同位素组成87Sr/86Sr为0.709193~0.709220。该等时线年龄代表了该矿床的主成矿阶段年龄,说明矿床形成的地质时代为早奥陶世,成矿作用发生于加里东中期。成矿作用时代与闪锌矿初始锶同位素比值特征反映成矿物质或成矿流体由基底岩石和震旦系碳酸盐岩地层共同提供。结合矿床地质特征与区内铅锌矿成矿地质背景,认为加里东期构造运动对扬子地台北缘的铅锌矿床的形成起着重要作用,冰洞山铅锌矿床可能是在加里东期伸展环境中,成矿热液伴随穹窿构造活动,在一定的物理化学条件下沉淀结晶而形成。     

四川天宝山矿床闪锌矿Rb-Sr年代学、稳定同位素及地质意义

四川天宝山铅锌矿床是赋存于震旦系灯影组白云岩中的大型铅锌矿床,一直以来缺乏精确的成矿年龄数据,致使其成矿构造环境存在争议.获取了闪锌矿Rb-Sr年龄,联合H-O、C-O同位素数据,以确定其成矿年代、成矿物质来源及成矿构造环境.闪锌矿Rb-Sr年龄为348.5±7.2 Ma(MSWD=1.10),表明矿床形成于早石炭世.热液矿物δD_H2O、δ18O值分别为-19.3‰~-58.1‰、-1.4‰~0.6‰,沿海水与地层有机质反应线分布,并有向雨水线漂移的趋势,说明成矿流体中水是海水与地层有机质反应并加入雨水的混合体.热液方解石δ13C、δ18O值明显分为两群,分别为-1.7‰~-1.6‰、12.9‰~15.2‰和-6.5‰~-4.9‰、19.3‰~20.2‰,暗示成矿流体中C、O可能来源于赋矿围岩溶解作用和有机质脱羧基作用.闪锌矿(87Sr/86Sr)_i值为0.710 42 ±0.000 13,高于赋矿围岩Sr同位素值而明显低于基底Sr同位素值,指示成矿物质主要来源于赋矿围岩与基底.结果表明川滇黔地区存在两期铅锌成矿作用,分别形成于晚泥盆世-早石炭世与古特提斯洋张开有关的伸展构造环境和晚三叠世-早侏罗世与古特提斯洋闭合有关的收缩构造环境.      

内蒙古兴和县曹四夭超大型斑岩钼铅锌金成矿系统年代学及其地质意义

曹四夭斑岩钼矿床位于内蒙古兴和县,是华北克拉通北缘最大的钼矿床。该矿床中部发育斑岩型钼矿体,外围和上部产出热液脉型铅锌金矿体。文章选取1件与斑岩钼矿化共生的绢云母样品进行了40Ar-39Ar定年,获得40Ar-39Ar坪年龄为(144.4±1.2)Ma,相应的39Ar/36Ar-40Ar/39Ar等时线年龄为(146.4±2.2)Ma(MSWD=0.31),将等时线年龄认作绢云母的Ar封闭年龄,表明曹四夭斑岩钼矿化发生在约146 Ma前。选取14件脉型铅锌矿石中的闪锌矿、黄铁矿和磁黄铁矿样品开展了Rb-Sr定年,获得4件闪锌矿的Rb-Sr等时线年龄为(145.1±3.0)Ma(MSWD=0.63);5件黄铁矿的Rb-Sr等时线年龄为(145.2±1.3)Ma(MSWD=0.53);4件闪锌矿、5件黄铁矿和1件磁黄铁矿的Rb-Sr等时线年龄为(145.3±1.0)Ma(MSWD=0.43)。硫化物Rb-Sr定年结果表明曹四夭矿床脉型铅锌矿化形成于约145 Ma前。本次绢云母40Ar-39Ar和硫化物Rb-Sr定年结果表明,曹四夭矿床斑岩型钼矿化和脉型铅锌金矿化为同期产物,两者均形成于晚侏罗世末期,属于同一个斑岩成矿系统。曹四夭矿床硫化物的w(Rb)和w(Sr)分别为0.1867×10~(-6)~1.305×10~(-6)和0.3175×10~(-6)~6.935×10~(-6),Sr同位素初始比值(87Sr/86Sr)i介于0.709 919~0.711 951之间,平均值0.710 952,结合前人获得的辉钼矿Re含量,认为曹四夭矿床的成矿物质主要来源于地壳。     

江苏栖霞山铅锌多金属矿床深部碳-氧-锶同位素地球化学特征及其指示意义

以栖霞山铅锌多金属矿床深部找矿钻孔岩心为对象,开展碳-氧-锶同位素地球化学研究。结果表明,栖霞山矿床矿石样品δ13CV-PDB同位素值为-5.1‰～1.9‰,且由浅部至深部,矿石样品的δ13C、δ18O值处于增大的趋势,指示成矿流体中的碳起源于碳酸盐岩、源自地幔和岩浆的深源碳。对锶同位素的研究显示,栖霞山矿石~(87)Sr/~(86)Sr值为0.704816～0.71405,部分大于矿体围岩黄龙组灰岩的~(87)Sr/~(86)Sr值(0.708329～0.709685),部分小于矿体围岩黄龙组灰岩的~(87)Sr/~(86)Sr值,并与不同来源的Sr同位素对比,揭示栖霞山矿石中Sr兼具基底地层Sr和幔源Sr的混合来源特征,且在围岩蚀变过程中~(87)Sr/~(86)Sr的变化应主要由成矿流体引起。结合本区成矿地质特征认为,栖霞山矿床成矿流体可能来自花岗岩的期后热液,在热动力作用下,流经元古宇基底地层,形成具有混合物质来源的成矿流体,成矿作用过程主要为成矿流体与围岩碳酸盐岩发生水-岩反应所致。     

云南禄劝噜鲁铅锌矿床铷-锶同位素年代学与硫、铅同位素地球化学特征

云南禄劝噜鲁铅锌矿床地处扬子地块西南缘,矿体赋存于下寒武统梅树村组下段,呈脉状、似层状产出。矿石矿物主要有方铅矿、闪锌矿、黄铁矿等;脉石矿物主要有重晶石、石英、方解石。噜鲁铅锌矿床硫化物成矿时的~(87)Sr/~(86)Sr值为0.7112~0.7115,暗示成矿物质可能来自于基底地层;Rb-Sr等时线年龄为202.8±1.4Ma,成矿年龄为印支晚期—燕山早期。硫化物硫同位素组成δ~(34)S变化范围为6.33‰~9.75‰,暗示成矿流体中的硫主要是海相硫酸盐热化学还原的产物;铅同位素~(206)Pb/~(204)Pb、~(207)Pb/~(204)Pb、~(208)Pb/~(204)Pb变化范围分别为18.259~18.342、15.608~15.639、38.46~38.821,位于上地壳和造山带铅演化线之间,落入基底岩石(昆阳群)及不同时代碳酸盐岩铅同位素组成范围内,表明成矿物质具有壳源特征,主要由基底岩石提供。综合各类地质-地球化学信息认为,噜鲁铅锌矿床成矿流体中不同组分来源不同,但主要来自于基底地层,成矿机制是在印支运动强驱动力的作用下,促使含矿基底地层成矿元素活化-迁移混合-空间就位,形成工业矿床。     

扬子地台西缘大梁子铅锌矿床成因:流体包裹体及同位素地球化学约束

扬子地台西缘大梁子铅锌矿床是川滇黔铅锌矿集区具代表性的大型矿床之一,矿体主要赋存于震旦系灯影组白云岩中,矿石矿物主要为闪锌矿和方铅矿,脉石矿物主要为白云石、石英和方解石。大梁子铅锌矿床可划分闪锌矿-黄铁矿-炭质、闪锌矿-方铅矿和方铅矿-黄铜矿-碳酸盐三个成矿阶段。H-O同位素及流体包裹体研究表明,成矿流体为中–低温(均一温度在117.5～320.3℃)及中-低盐度(盐度范围为5.11%～18.96%NaCl_(eqv))的盆地卤水,有机质参与成矿。灯影组白云岩与海相沉积碳酸盐岩具有相似的C、O同位素组成,而热液方解石C、O同位素组成均稍低于灯影组白云岩,可能是海相碳酸盐岩溶解与有机质共同作用的结果。矿区硫化物δ~(34)S值为9.8‰～20.8‰,结合成矿温度,S主要形成于灯影组海相硫酸盐的热化学还原作用。矿石硫化物的Pb同位素比值在Pb演化图解上主要落在上地壳与造山带之间,表明Pb具有壳源特征,成矿物质可能主要来源于围岩,部分来自于基底地层。热液方解石及闪锌矿的(~(87)Sr/~(86)Sr)i比值均高于围岩,表明成矿流体可能流经了具有高(~(87)Sr/~(86)Sr)i比值的基底地层,并与其发生水岩反应及同位素交换。综上,大梁子铅锌矿床成矿流体具有盆地卤水特征,盆地卤水在运移过程中萃取了基底及围岩中的Pb、Zn等成矿物质,成矿流体运移至矿区"黑破带"时,在有机质作用下发生TSR作用,形成还原S,导致Pb、Zn等金属沉淀成矿。     

江西众埠街大型铅锌矿床Rb-Sr同位素年龄及成矿流体特征

江西众埠街矿床位于钦杭成矿带东段,是近年来取得重大找矿突破的大型铅锌多金属矿床。为研究众埠街矿床成矿作用,对成矿阶段的石英、方解石开展流体包裹体和氢-氧同位素研究,采用闪锌矿Rb-Sr定年方法测定众埠街大型铅锌多金属矿床的成矿时代,通过闪锌矿Sr同位素初始比(⁸⁷Sr/⁸⁶Sr)_i判断成矿物质来源。测得闪锌矿Rb-Sr等时线年龄为359±7 Ma,表明铅锌成矿期为早石炭世。闪锌矿Sr同位素初始(⁸⁷Sr/⁸⁶Sr)_i值介于0.6937～0.7163之间,平均值为0.709,表明成矿物质来源于壳幔混合。流体包裹体显微测温结果显示,均一温度范围为154～310℃,盐度范围为0.70%～5.70%NaCl_eqv。石英氢-氧同位素结果显示,δD_V-SMOW值变化范围为-75.4‰～-58.1‰,δ¹⁸O_H2O值为1.0‰～8.1‰。综合研究表明,成矿流体主...     

Wavelength-dispersive X-ray fluorescence spectrometric determination of Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in komatiites

Komatiites are mantle-derived ultramafic volcanic rocks. Komatiites have been discovered in several States of India, notably in Karnataka. Studies on the distribution of trace-elements in the komatiites of India are very few. This paper proposes a simple, accurate, precise, rapid, and non-destructive wavelength-dispersive x-ray fluorescence (WDXRF) spectrometric technique for determining Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in komatiites, and discusses the accuracy, precision, limits of detection, x-ray spectral-line interferences, inter-element effects, speed, advantages, and limitations of the technique. The accuracy of the technique is excellent (within 3%) for Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Zr, Nb, Ba, Pb, and Th and very good (within 4%) for Y. The precision is also excellent (within 3%) for Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th. The limits of detection are: 1 ppm for Sc and V; 2 ppm for Cr, Co, and Ni; 3 ppm for Cu, Zn, Rb, and Sr; 4 ppm for Y and Zr; 6 ppm for Nb; 10 ppm for Ba; 13 ppm for Pb; and 14 ppm for Th. The time taken for determining Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in a batch of 24 samples of komatiites, for a replication of four analyses per sample, by one operator, using a manual WDXRF spectrometer, is only 60 hours.     

高压微波消解法测定醋酸纤维过滤器采集的微尘粒子中的砷镉钴铬铜铁锰镍铅钒锌

最新的流行病学研究表明,空气中较高浓度的悬浮细颗粒可能对人类的健康有不利的影响。根据该项研究显示,由于心脏病、慢性呼吸问题和肺功能指标恶化而导致死亡率的升高与细尘粒子有关。这些研究结果已经促使欧盟于1999年4月出台了限制空气中二氧化硫、二氧化氮、氧化氮、铅和颗粒物含量的法案(1999/30/EC),对各项指标包括对可吸入PM10颗粒的浓度提出了新的限制性指标。PM10颗粒是指可以通过预分级器分离采集的气体动力学直径小于10μm的细颗粒。目前研究的兴趣重点逐步偏向PM2.5这些更细微颗粒物,PM2.5这种颗粒物对健康有明显的不利影响。在欧盟指令2008/50/EC中,对PM10和PM2.5都提     

Isotopic systematics of He,Ar, S,Cu, Ni,Re, Os,Pb, U,Sm, Nd,Rb, Sr,Lu, and Hf in the rocks and ores of the Norilsk deposits

This paper reports the first results of a study of 11 isotope systems (³He/⁴He, ⁴⁰Ar/³⁶Ar, ³⁴S/³²S, ⁶⁵Cu/⁶³Cu, ⁶²Ni/⁶⁰Ni, ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, ^206–208Pb/²⁰⁴Pb, Hf–Nd, U–Pb, and Re–Os) in the rocks and ores of the Cu–Ni–PGE deposits of the Norilsk ore district. Almost all the results were obtained at the Center of Isotopic Research of the Karpinskii All-Russia Research Institute of Geology. The use of a number of independent genetic isotopic signatures and comprehensive isotopic knowledge provided a methodic basis for the interpretation of approximately 5000 isotopic analyses of various elements. The presence of materials from two sources, crust and mantle, was detected in the composition of the rocks and ores. The contribution of the crustal source is especially significant in the paleofluids (gas–liquid microinclusions) of the ore-forming medium. Crustal solutions were probably a transport medium during ore formation. Air argon is dominant in the ores, which indicates a connection between the paleofluids and the atmosphere. This suggests intense groundwater circulation during the crystallization of ore minerals. The age of the rocks and ores of the Norilsk deposits was determined. The stage of orebody formation is restricted to a narrow age interval of 250 ± 10 Ma. An isotopic criterion was proposed for the ore-bearing potential of mafic intrusions in the Norilsk–Taimyr region. It includes several interrelated isotopic ratios of various elements: He, Ar, S, and others.     

硅酸盐中铁、锰、钛、钙、钾、磷、硅、铝、镁、钠、锶、铷、钡的X-射线荧光光谱定量测定

本文介绍样品经四硼酸锂熔融制成玻璃小饼。采用Lachance模式和理论a系数来校正元素间的效应,由3080E型X-射线荧光谱仪和DF-350B数据处理系统完成硅酸盐中十三个项目的测定。     

硅酸盐类样品中硅、铁、铝、钛、锰、钙、镁、钾、钠和磷的x射线荧光光谱测定

本文拟定了一种以熔融法制备样片,用X射线荧光光谱测定硅酸盐类样品中Si、Fe、Al、Tj、Mn、Ca、Mg、K、Na、P等元素的分析方法。在对不同靶材X光管和分光晶体实验对比的基础上,选择了最佳的测量条件。该法具有快速、准确,测量范围广,检测限低,价格便宜等优点。经过近百个各种类型标样或管理样品的分析对比表明,本法不仅适用于硅酸盐类岩石样品的分析,还适用于铁矿、铝土矿、碳酸盐类岩矿样品以及水泥、耐火材料等样品的分析。     

Viscous, cohesive, non-Newtonian, depositing, radial slurry flow

Mining induced subsidence can significantly affect mining costs where major surface facilities and natural environment need to be protected. Overburden grout injection is a technology used to control coal mine subsidence by injecting the mine waste material extracted from the coal back into the inter-burden rock during longwall mining. The flowing slurry is here categorised as a nonlinear viscous cohesive (Bingham plastic) fluid. During longwall mining the grout slurry is pumped into the separated beds of the rock mass through a central vertical borehole, which is drilled deep into the inter-burden rock strata above the coal seam. However, a blockage can occur in the injection system when the slurry velocity falls below a certain critical threshold velocity, indicating a material phase change from cohesive-viscous to cohesive-frictional. In situ field injection tests through boreholes have been simulated at a smaller scale at the CSIRO laboratory in Brisbane by pumping the slurry through a radial disk (gap = 4 mm) from its centre. Laboratory experiments indicate a general, nonlinear, cohesive, viscous, frictional model for shear behaviour of the slurry, in which the material shear parameters are functions of the disk radial distance. Complete dimensional and dimensionless analytical solutions have been developed based on an approach related to Bingham–Herschel–Bulkley fluid mechanics. The derived formulae include relations for minimum pump pressure, local pressure and pressure gradient, wall shear stress, volume rate, velocity and velocity gradient. The theoretical results match the experimental measurements. The experiments covered slurries with maximum particle sizes of 0.5 to 2 mm with about 50% being larger than 100 µm. The viscosities at the various solids concentrations were measured with a standard torsion viscometer. This study differs from the previous research in several distinct aspects, namely, consideration of the variable shear parameters rather than fixed values, inclusion of total nonlinear behaviour, and implementation of a friction function to mimic behaviour of the deposited and consolidating stiff slurry, which can cause a significant pressure rise as a result of the increased shear resistance.     

Mountains,nations, parks,and conservation

Between 1985 and 1991, two new mountain protected areas (MTNPA) covering more than 35,000 km² and based on participatory management models — the Makalu-Barun National Park and Conservation Area, Nepal, and Qomolangma Nature Preserve, Tibet Autonomous Region — were successfully established through the collaborative efforts of Woodlands Mountain Institute and conservationists in China and Nepal. Characteristics common to both projects include the importance of establishing (1) effective rationales, (2) local support constituencies, (3) a senior advisory group, (4) a task force, (5) linkages between conservation and development, and (6) fund raising mechanisms. The lessons derived from the experiences of Woodlands Mountain Institute are of significant value to others in preserving MTNPA. Increased collaboration and communication between all interested in conservation, however, will remain a critical component for expanding mountain protected area coverage to throughout the world.     

Regional distribution of Al,B, Ba,Ca, K,La, Mg,Mn, Na,P, Rb,Si, Sr,Th, U and Y in terrestrial moss within a 188,000 km2 area of the central Barents region: influence of geology,seaspray and human activity

Five hundred and ninety-eight samples of terrestrial moss (Hylocomium splendens and Pleurozium schreberi) collected from a 188,000 km² area of the central Barents region (NE Norway, N Finland, NW Russia) were analysed by ICP-AES and ICP-MS. Analytical results for Al, B, Ba, Ca, K, La, Mg, Mn, Na, P, Rb, Si, Sr, Th, U and Y concentrations are reported here. Graphical methods of data analysis, such as geochemical maps, cumulative frequency diagrams, boxplots and scatterplots, are used to interpret the origin of the patterns for these elements. None of the elements reported here are emitted in significant amounts from the smelting industry on the Kola Peninsula. Despite the conventional view that moss chemistry reflects atmospheric element input, the nature of the underlying mineral substrate (regolith or bedrock) is found to have a considerable influence on moss composition for several elements. This influence of the chemistry of the mineral substrate can take place in a variety of ways. (1) It can be completely natural, reflecting the ability of higher plants to take up elements from deep soil horizons and shed them with litterfall onto the surface. (2) It can result from naturally increased soil dust input where vegetation is scarce due to harsh climatic conditions for instance. Alternatively, substrate influence can be enhanced by human activity, such as open-cast mining, creation of ‘technogenic deserts’, or handling, transport and storage of ore and ore products, all of which magnify the natural elemental flux from bedrock to ground vegetation. Seaspray is another natural process affecting moss composition in the area (Mg, Na), and this is most visible in the Norwegian part of the study area. Presence or absence of some plant species, e.g., lichens, seems to influence moss chemistry. This is shown by the low concentrations of B or K in moss on the Finnish and Norwegian side of the (fenced) border with Russia, contrasting with high concentrations on the other side (intensive reindeer husbandry west of the border has selectively depleted the lichen population).     

NEW SET OF LOW CONCENTRATION STANDARDS FOR LA, CE, SM, YB, LU, Y, SC, V, NB AND TA IN SILICATES

We have developed a set of four synthetic standards for the rare earth and high field strength elements designed for use in the determination of those elements in silicates. The base material is a glass nominally at the eutectic of the MgO-Al₂O₃-SiO₂ ternary system. The nominal doping level was 2 wt% of the elements as oxides. To avoid problems associated with peak interference, the elements were doped in four separate glasses.