藏南亚东地区片麻状含石榴子石黑云花岗闪长岩LA-ICP-MS锆石U-Pb测年及其地质意义

亚东岩组是高喜马拉雅地区重要的前寒武纪变质地层之一。利用LA-ICP-MS锆石U-Pb测年技术对侵入亚东岩组的片麻状含石榴子石黑云花岗闪长岩进行了测年,获得岩浆结晶年龄为(499.2±3.9)Ma(中寒武世),提供了泛非构造-岩浆事件的记录。岩石地球化学分析表明,黑云花岗闪长岩SiO2含量为68.04%～68.92%,在(K2O+Na2O)-SiO2图解上样品点落入亚碱性系列的花岗闪长岩区,A/CNK指数均大于1.1,在Shand指数图解上落入过铝质系列区。稀土元素配分模式属轻稀土元素富集的右倾曲线,出现弱Eu负异常(δEu=0.62～0.79);微量元素表现出Ba、Nb、Ta、Sr亏损和Rb、Th、U相对富集的特征。通过Rb-(Y+Nb)和Rb-Hf-Ta图解判别,认为亚东地区片麻状含石榴子石黑云花岗闪长岩形成于后碰撞构造阶段。     

西藏米林县片麻状黑云花岗闪长岩地球化学特征、锆石U-Pb定年及Pb-Sr-Nd同位素组成

喜马拉雅是印度与欧亚板块俯冲碰撞作用形成的全球最年轻、规模最大和正在活跃的造山带。利用LA-ICP-MS锆石U-Pb测年技术对位于东喜马拉雅构造结侵入南迦巴瓦岩群的片麻状黑云花岗闪长岩进行了测年,获得岩浆结晶年龄为515.5±2.3 Ma(早寒武世),提供了泛非构造-岩浆事件在东喜马拉雅构造结的记录。岩石地球化学分析表明,SiO2含量为66.47%~72.42%,A/CNK指数为0.98~1.08,平均1.03,在A/NK-A/CNK指数图解中样品大部分落入过铝质区,里特曼指数σ为1.53~3.08,为钙碱性系列,在SiO2-K2O图解上大部分样品投入高钾钙碱性系列区,在Harker图解中所有样品中的TiO2、MgO、FeOT、MnO、K2O随着SiO2含量的变化增加而减少,Na2O随着SiO2含量的增加而增加,均呈较好的线性关系。稀土元素配分模式为轻稀土元素富集的右倾曲线,(La/Yb)N为19.1~63.8,出现弱Eu负异常(δEu=0.24~0.88);微量元素表现出Ba、Nb、Ta、Sr、Zr亏损,而大离子亲石元素Rb、Th和U相对富集的特征。Sr、Nd同位素组成表明,丹娘乡片麻状黑云花岗闪长岩具有负εNd(t)值(-8.67~-10.57)和较老的Nd模式年龄(tDM=1.84~3.42),说明其来源可能是上地壳物质,结合87Sr/86Sr初始比值特征,推断丹娘乡片麻状黑云花岗闪长岩是在高温环境下经部分熔融形成的。通过构造环境判别图及岩石地球化学研究认为丹娘乡准铝质-弱过铝质片麻状黑云花岗闪长岩形成于后碰撞造山环境,结合新得到的513 Ma同位素年龄,认为泛非碰撞造山事件早寒武世在东喜马拉雅构造结一带可能结束,进入后碰撞造山的构造演化阶段。     

江苏东海片麻状碱性花岗岩地质地球化学及其年代学研究—以驼峰、牛山两地为例

本文通过对东海县驼峰和牛山片麻状碱性花岗岩的产状、岩石结构构造、碱性铁镁矿物、元素地球化学和锆石成因及SHRIMP定年等综合研究,得出以下结论:①驼峰和牛山片麻状碱性花岗岩,在造岩矿物和岩石化学成分等方面具有与岩浆成因的钠质碱性花岗岩一致的特点:高硅(SiO2 =74.25％～77.08％)、富碱(Na2O+K2O=7...     

华北克拉通南缘豫西下汤地区2.3 Ga岩浆作用和1.94 Ga变质作用

本文报道了华北克拉通南缘豫西鲁山下汤地区古元古代片麻状花岗岩和黑云角闪斜长片麻岩的全岩地球化学和锆石SHRIMP U-Pb年龄和Hf同位素组成。岩石呈包体形式存在于中元古代花岗岩中。片麻状花岗岩具深熔特征,岩浆锆石年龄为2.30Ga;岩石高SiO2和K2O,低ΣFeO、MgO和CaO,具稀土总量较高(ΣREE=165.8×10-6)、轻重稀土分离较强[(La/Yb)n=37.8]及弱负铕异常(Eu/Eu*=0.76)的稀土模式;εNd(t)(t=2.30Ga)=-0.75;tDM(Nd)=2.66Ga。黑云角闪斜长片麻岩变质原岩为辉长闪长岩,捕获锆石年龄为2.25Ga;岩石低SiO2和MgO,高Al2O3和P2O5,具稀土总量高(ΣREE=373.4×10-6)、轻重稀土分离不强[(La/Yb)n=9.4]及较强负铕异常(Eu/Eu*=0.44)的稀土模式;εNd(t)(t=2.25Ga)=-1.21;tDM(Nd)=2.75Ga。片麻状花岗岩和黑云角闪斜长片麻岩都记录了1.94Ga变质锆石年龄。片麻状花岗岩的岩浆锆石组成域的εHf(t)(t=2.30Ga)=-6.71～0.38,tDM1(Hf)=2627～2910Ma,tDM2(CC)(Hf)=2823～3255Ma。黑云角闪斜长片麻岩的捕获锆石组成域的εHf(t)(t=2.25Ga)=-19.58～-1.73,tDM1(Hf)=2664～3360Ma,tDM2(CC)(Hf)=2968～4011Ma。结合前人资料,得出如下结论:华北克拉通南缘豫陕晋结合部地区存在一规模较大的约2.3Ga地质体分布区;华北克拉通南缘很可能存在规模巨大的>2.7Ga基底;中部造山带与孔兹岩带具有类似的古元古代晚期构造热事件演化历史。     

青海大黑山钨矿黑云二长花岗岩的锆石U-Pb同位素定年及岩石地球化学特征

大黑山钨矿位于祁连山加里东造山带,其形成与宝库河黑云二长花岗岩密切相关。黑云二长花岗岩锆石LA-ICPMS U-Pb测年结果显示其形成年龄为:450.2±2.8Ma,为加里东期岩浆活动的产物。地球化学数据显示,宝库河黑云二长花岗岩富硅(SiO2含量为73.03%～74.18%)、富钾(K2O/Na2O为1.13～1.94,K2O+Na2O含量为7.25%～8.51%)、铝过饱和(A/CNK为1.04～1.12),为过铝质钙碱性-高钾钙碱性花岗岩。P2O5含量低(0.03%～0.08%),且具有随SiO2含量的增长呈现负增长的趋势。稀土含量低,Eu明显负异常,LREE分异强烈,HREE分异不明显。微量元素蛛网图中Th、U、Pb、Zr、Hf呈现明显的正异常,Ba、Sr、Ta、Nb、P、Ti呈现负异常,为I型花岗岩。结合对区域动力地质背景的分析,表明宝库河黑云二长花岗岩形成于活动大陆边缘,由地壳物质熔融并结晶形成。     

2.3 Ga Magmatism and 1.94 Ga Metamorphism in the Xiatang Area,Southern Margin of the North China Craton——Evidence from Whole-rock Geochemistry and Zircon Geochronology and Hf Isotope

本文报道了华北克拉通南缘豫西鲁山下汤地区古元古代片麻状花岗岩和黑云角闪斜长片麻岩的全岩地球化学和锆石SHRIMP U-Pb年龄和Hf同位素组成.岩石呈包体形式存在于中元古代花岗岩中.片麻状花岗岩具深熔特征,岩浆锆石年龄为2.30 Ga;岩石高SiO2和K2O,低∑FeO、MgO和CaO,具稀土总量较高(∑REE=165.8×10-6)、轻重稀土分离较强[(La/Yb)n=37.8]及弱负铕异常(Eu/Eu(*)=0.76)的稀土模式;εNd(t)(t=2.30 Ga)=-0.75; tDM(Nd) =2.66 Ga.黑云角闪斜长片麻岩变质原岩为辉长闪长岩,捕获锆石年龄为2.25 Ga;岩石低SiO2 和MgO,高Al2O3和P2O5,具稀土总量高(∑REE=373.4×10-6)、轻重稀土分离不强[ (La/Yb)n=9.4]及较强负铕异常( Eu/Eu*=0.44)的稀土模式;εNd(t)(t=2.25 Ga)=-1.21;tDM(Nd) =2.75 Ga.片麻状花岗岩和黑云角闪斜长片麻岩都记录了1.94 Ga变质锆石年龄.片麻状花岗岩的岩浆锆石组成域的εHf(t)(t=2.30 Ga)=-6.71～0.38,tDMI(Hf) =2627 ～2910 Ma,tDM2(CC)(Hf)=2823 ～ 3255 Ma.黑云角闪斜长片麻岩的捕获锆石组成域的εHf(t)(t=2.25 Ga)=-19.58～ -1.73,tDM1 (Hf) =2664～3360 Ma,tDM2(CC)(Hf)=2968 ～4011 Ma.结合前人资料,得出如下结论:华北克拉通南缘豫陕晋结合部地区存在—规模较大的约2.3 Ga地质体分布区;华北克拉通南缘很可能存在规模巨大的＞2.7 Ga基底;中部造山带与孔兹岩带具有类似的古元古代晚期构造热事件演化历史.     

张广才岭南部早—中侏罗世花岗质岩浆作用及构造演化

近年来对张广才岭南部中生代花岗岩成因和演化等问题的研究较少,对其进行系统的同位素年代学和岩石地球化学研究有助于加深对张广才岭南部早—中侏罗世构造岩浆演化及地球动力学背景的认识。张广才岭南部早侏罗世花岗岩主要由黑云母石英闪长岩、黑云母花岗闪长岩和黑云母二长花岗岩组成,3件样品的LA- ICP- MS锆石U- Pb年龄为172. 7~182. 4Ma,属于早侏罗世。黑云母石英闪长岩和花岗闪长岩以含有大量暗色微粒包体为特点,具有钙碱性、A/CNK值小于1. 1、Eu具弱负异常(δEu=0. 55~1. 03)等地球化学特征,属于I型花岗岩,具有壳幔混合成因机制;黑云母二长花岗岩为过铝质高钾钙碱性岩石,具有S型花岗岩特征;中侏罗世黑云英云闪长岩富含暗色微粒包体,其A/CNK值小于1. 1(0. 88~0. 93),为钙碱性I型花岗岩;正长花岗岩和碱长花岗岩具有高硅(SiO2=76. 89%~77. 82%)、富碱(K2O+Na2O=6. 36%~8. 5%)、富铁贫镁(FeOT/MgO=6. 2~20. 6)的特征,并且稀土总量高、Eu负异常明显(δEu=0. 01~0. 74)、轻稀土富集、重稀土亏损,属于A2型花岗岩。对张广才岭南部早—中侏罗世花岗岩的研究表明,早侏罗世早期(172. 7~182. 4Ma),由于古太平洋板块的俯冲及后续的岩石圈拆沉效应, 导致地幔上隆及幔源岩浆的板底垫托造成古老地壳和新生地壳的部分熔融,由此形成具壳幔混合成因的花岗岩体;早侏罗世晚期(172. 7Ma),东侧佳木斯板块与张广才岭地块碰撞造山作用形成黑云母二长花岗岩体;中侏罗世早期(168. 1Ma),东侧大洋板块的俯冲作用持续,形成具壳幔混合成因的黑云英云闪长岩;中侏罗世晚期(166Ma),构造环境逐渐由挤压造山向造山后伸展环境转变。     

广州市白云山片麻状花岗岩成因及构造意义

华南板块内部广泛分布的早古生代片麻状花岗岩的形成究竟是与大洋板块俯冲有关,还是与陆内挤压碰撞有关,存在激烈争议.本文对广州市白云山风景名胜区内的片麻状花岗岩进行了LA-ICP-MS锆石U-Pb年代学、全岩主量元素和微量元素、Sr-Nd同位素和锆石Hf-O同位素地球化学研究,结果表明:白云山片麻状花岗岩形成于晚奥陶-早志留世(444±6 Ma).白云山片麻状花岗岩含有原生白云母和黑云母,并且具有高的SiO2,Al2O3和低的MgO含量(SiO2=74.8％～80.4％,Al2O3=9.64％～12.7％,MgO=0.46％～0.61％).白云山片麻状花岗岩的稀土总量相对较低,变化于44～173μg/g之间,具有轻稀土相对富集的右倾分布模式,同时具有中-强的Eu负异常(Eu*=0.27～0.63).白云山片麻状花岗岩富集Rb、Th、U和Pb,亏损Ba、Sr、Nb、Ta、Zr、Hf和Ti.白云山片麻状花岗岩具有富集的全岩Nd和锆石Hf同位素组成(εNd(t)=-12.1～-7.88;εHf(t)=-10.8～-2.63)以及高的锆石O同位素组成(δ18O=8.06‰～11.4‰).岩相学和地球化学特征表明白云山片麻状花岗岩主要起源于地壳变质沉积岩的部分熔融.结合区域地质和白云山片麻状花岗岩的地球化学特征,提出白云山片麻状花岗岩最有可能形成于早古生代陆内挤压造山的构造背景.     

冀东黄柏峪—羊崖山地区太古宙岩浆作用和变质作用——SHRIMP锆石U-Pb定年

报道了冀东黄柏峪—羊崖山地区太古宙变质辉长岩、黑云斜长片麻岩、片麻状二长花岗岩、片麻状富钾花岗岩等不同类型变质岩浆岩(8个样品)的SHRIMP锆石U-Pb定年结果。首次发现3.1Ga二长花岗岩,黑云斜长片麻岩形成时代约为3.0Ga。变质辉长岩的侵入时代很可能为新太古代晚期,存在少量3.2~3.6Ga捕获锆石。几乎所有岩石样品都记录了约2.5Ga的变质锆石年龄。结合前人资料认为,(1)冀东地区新太古代晚期构造热事件十分发育,被认为与地幔软流圈上涌导致的岩浆板底垫托有关;(2)冀东地区中太古代以前的陆壳物质广泛分布,黄柏峪—羊崖山地区很可能存在一古老陆核。     

西藏冈底斯带中段以东得明顶地区晚白垩世花岗岩类锆石U-Pb年代学和地球化学证据

得明顶地区花岗岩位于西藏冈底斯火山岩浆弧中段以东,主要岩石类型有:石英闪长岩、石英二长闪长岩、英云闪长岩、黑云花岗闪长岩、斑状黑云二长花岗岩,岩石具钙碱性特征,w(SiO2)在57.19%～71.78%之间,K2O/Na2O=0.39～0.98,相对富钠,A/CNK=0.80～1.02,Al2O3变化于13.64%～18.74%之间,为准铝质岩石,花岗岩体稀土元素总量ΣREE变化于94.69×10-6～227.28×10-6之间;轻稀土元素富集,负Eu异常由不明显到明显,富K,Rb,Ba,Th等大离子亲石元素和亏损Nb,Y,Yb等高场强元素为特征。岩石学和岩石地球化学研究表明,该时期的花岗岩有由中性向酸性演化的规律,为同源岩浆,具俯冲I型花岗岩的特点,形成于板块俯冲下的岛弧环境。冈底斯岩带中东段雪拉岩体花岗闪长岩锆石的SHRIMPU-Pb年龄为70.4Ma±2.2Ma,表明冈底斯岩浆弧带在白垩世从早到晚岩浆均在剧烈地活动,是新特提斯洋向北俯冲作用的产物。     

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.     

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.     

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     

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.     

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.     

Bellechester,Minnesota, USA,lagoon collapses

Bellechester, Minnesota, is a small community of approximately 155 residents located on the county line between Goodhue and Wabasha counties in southeast Minnesota's karst region. Bellechester is served by a 21-year-old wastewater treatment facility (WWTF) consisting of three waste-stabilization ponds. On 28 April 1992 six sinkholes were discovered to have drained cell 2 of the WWTF resulting in the loss of approximately 8.7×10⁶ 1 of partially treated effluent and about 600 m³ of soil into previously undetected subsurface voids of unknown dimensions. In the week following the collapse, approximately 200 water wells located within a 5-km radius of the WWTF were sampled in an after-the-fact, emergency sampling program. Twelve samples with elevated fecal coliform levels, 18 samples with nitrate-nitrogen greater than the 10 mg/1 standard, and no samples with elevated chlorides were found. However, the elevated levels could not be unambiguously attributed to the WWTF collapse. This is the third WWTF to fail by sinkhole collapse in southeast Minnesota since 1974. All three collapsed lagoons have been located in similar geomorphic and stratigraphic settings. However, at least two lagoons have collapsed in the adjacent area in northeast Iowa, and these lagoons are located at different stratigraphic positions. Twenty-two WWTFs constructed in southeast Minnesota's karst region in the last 25 years have been identified as subject to potential sinkhole collapse. An unknown but significant number of manure storage lagoons, flood control structures, etc., have also been constructed in the karst region and are at risk. Public agencies are beginning to develop plans to deal with the risk associated with existing and future waste lagoons in this environment. The critical hydrogeologic parameters that can be used to prioritize the risk of collapse at existing facilities include: (1) the lithology of the first bedrock beneath each lagoon, (2) the thickness of surficial materials between the lagoon and the bedrock surface, (3) the presence and construction of liners (seepage rate), and (4) the proximity to existing sinkholes.