内蒙古北山交叉沟地区变质火山岩Sm-Nd同位素研究

交叉沟变质杂岩套主要由斜长角闪岩、片麻岩、长英片岩、绿片岩和条带状混合岩组成 ,为中国西北北山造山带红石山—黑鹰山地体的重要组成部分。长期以来 ,由于缺少可信的同位素年代学数据 ,该套变质岩的形成时代、成岩环境和物质来源尚不清楚。笔者等首次对交叉沟变质杂岩套代表性变质岩进行了 Sm- Nd同位素研究 ,其中斜长角闪岩 Sm- Nd同位素等时线年龄为 12 6 4± 11Ma、其 1 43Nd/ 1 44 Nd初始值为 0 .5 11375± 13,εNd(t)为 7.2 4± 0 .0 2 (2 σ)。与斜长角闪岩样品相比 ,各类片麻岩的 εNd(12 6 4 Ma)值明显偏低 ,变化范围为 1.18～ - 5 .17。依据上述Sm- Nd同位素数据 ,并且结合野外地质证据和岩相学特征 ,认为交叉沟地区斜长角闪岩的原岩为基性火成岩 ,属于幔源基性岩浆活动的产物 ,成岩时代为中元古代 ,而片麻岩的原岩则多为中酸性火成岩 ,其形成过程与古元古代或太古宙古陆壳岩层的再造作用有关。     

内蒙古锡林格勒杂岩的地球化学研究:从Rodinia聚合到古亚洲洋闭合后碰撞造山的历史记录

内蒙古东部出露的锡林格勒杂岩主要由中元古代原岩为火成岩的黑云母片麻岩和斜长角闪岩透镜体组成。片麻岩显示轻稀土元素富集的中等分异特征 ,具明显的Eu负异常 ,其不相容元素特征与平均地壳类似但相对亏损Ba和Sr。斜长角闪岩构成一条Sm -Nd等时线 ,其年龄值为12 0 2± 6 5Ma ,εNd(1.2 0Ga)值为 6 .8。角闪岩的亏损地幔模式年龄 (tDM,1.2 6～ 1.32Ga)与其Sm -Nd同位素等时线年龄接近。角闪岩的Rb -Sr同位素等时线年龄为 393± 14Ma ,其87Sr/ 86 Sr初始比值为 0 .70 379± 0 .0 0 0 0 7,此Rb -Sr等时线年龄与本区出露的篮片岩Ar-Ar年龄 (～ 383Ma)一致 ,记录了中亚造山带东南部洋壳俯冲结束后由大陆碰撞造山引起的变质作用事件。黑云母片麻岩的Rb -Sr同位素等时线年龄为 2 79.5± 6 .4Ma ,87Sr/ 86 Sr初始比值为 0 .70 85 1± 0 .0 0 0 10 ,此Rb -Sr等时线年龄与本区广泛分布的早二叠世火山岩的Rb -Sr等时线年龄 (～ 2 77± 15Ma)一致 ,因此可能是由大规模岩浆活动诱发的变质作用的记录。锡林格勒杂岩因此不仅记录了Rodinia超大陆聚合的地质事件 ,并且通过对比研究本地区蛇绿岩和晚古生代岩浆岩的演化历史 ,可以恢复从Ro dinia超大陆聚合 (～ 1.2 0Ga)到古亚洲洋关闭 (～ 4 30Ma)、大陆碰撞造山 (～ 39     

西天山阿吾拉勒埃达克质岩石成因：Nd和Sr同位素组成的限制

西天山阿吾拉勒二叠纪钠质英安岩和钠长斑岩具有与埃达克岩一致的高Sr,低Y、Yb和Eu正异常等独特岩石地球化学特征。系统的Nd和Sr同位素组成研究表明，其（^143Nd/^144Nd)i为0．512384－0．512470，εNd(t)为正值（＋1．57－＋3．26）；（^87Sr/^86Sr)i为0．0751－0．7054，与本区同时代幔源玄武岩的Nd和Sr同位素组成特征相似，但与俯冲洋壳部分熔融成因埃达克岩的Nd和Sr同位素组成有显著区别。结合这些埃达克质岩石形成二叠纪后碰撞阶段构造背景，认为本区埃达克质岩浆最有可能由新底侵的玄武质下地壳在角闪岩相向榴辉岩相过渡或榴辉岩相的条件下部分熔融形成，是西天山晚古生代后碰撞阶段地幔玄武岩浆底侵作用和地壳垂向增生的重要岩石标志。     

木其滩岩组形成时代、地球化学特征——对北秦岭构造演化的制约

出露于北秦岭造山带中的木其滩岩组主要由斜长角闪岩组成,其原岩为玄武岩-亚碱性玄武岩。对木其滩岩组斜长角闪岩中的锆石进行LA-ICP-MS U-Pb年代学分析,获得同位素年龄762.5±4.6Ma,为成岩年龄。地球化学上,这些斜长角闪岩显示低钛 (TiO₂=0.57%~2.16%),低K₂O/Na₂O比值(0.06~0.55)和中等-高 Mg^#(45.3~68.7)特征,为低钛拉斑玄武岩。在球粒陨石标准化图解中,表现出轻重稀土分异,无Eu异常的特征,类似于E-MORB。这些斜长角闪岩以Rb、Ba、Th和La富集,低(⁸⁷Sr/⁸⁶Sr)_i 比 (0.7038~0.7040) 和高的ε_Nd(t)值(+4.1~+6.9)为特征,表明其来源于地幔,成分上相似于FOZO。(Th/Nb)_N, Nb/La 和 Ba/La的比值特征表明它们经历了不同程度的地壳混染。所有这些特征,结合区域地质资料阐明木其滩岩组斜长角闪岩代表的是大约762.5±4.6Ma商丹洋盆初始裂解时的洋壳残片。     

新疆中天山巴仑台地区晚石炭世＋εNd辉长岩体的岩石学和同位素地球化学研究

新疆巴仑台附近出露的辉长岩(骆驼沟岩体)是中天山地区出露最大的晚石炭世基性侵入体,该岩体分带明显,由边部的细粒辉长玢岩(冷凝边)逐渐过渡到内部的中粗粒辉长玢岩.中粗粒辉长玢岩的εNd值(+5.10～+5.74)和初始87Sr/86Sr比值(0.7055～0.7058)变化很局限,但边缘相细粒辉长玢岩的εNd值(+4.25～+7.28)变化较大而初始87 Sr/86 Sr值(0.7058～0.7059)变化较小.三个细粒辉长玢岩全岩样品构成一条Rb-Sr等时线,等时线年龄321±10Ma(MSWD=1.5,初始87 Sr/86 Sr值0.705725±0.000084),这与位于该地区以西大面积出露的粗面安山岩的锆石SHRIMP年龄(313Ma)接近.与晚石炭世粗面安山岩类似,骆驼沟辉长岩富集La、Sr和Ba.高的+εNd值表明形成骆驼沟辉长岩的岩浆具有亏损地幔的性质,但明显偏高的初始87Sr/86Sr比值说明骆驼沟辉长岩不是亏损地幔直接部分熔融的产物,而可能是亏损地幔来源的岩浆与富La、Ba、Sr的长英质岩浆混合(或者与相应火山岩同化混染)的结果.     

大别核部杂岩中斜长角闪岩的地球化学特征及其地质意义

大别核部杂岩单元中斜长角闪岩的地球化学特征对于认识大别核部杂岩单元的特征及归属有着十分重要的意义。本文对大别核部杂岩单元中斜长角闪岩的岩石地球化学特征及Sm-Nd 同位素特征进行了较系统研究。斜长角闪岩的 Nd亏损地幔模式年龄(t_(DM))有3个不连续年龄段,它们分别为2.50～2.92Ga(平均2.71Ga);1.79～2.47Ga(平均2.14Ga);1.07～1.57Ga(平均1.38Ga)。模式年龄为中元古代、古元古代的斜长角闪岩的等时线年龄分别为1444±180Ma、2220±210Ma,其模式年龄与等时线年龄在误差范围内一致。表明至少模式年龄为元古宙的斜长角门岩的t_(DM)可代表其原岩的近似形成年龄,从而证明大别核部杂岩单元中存在着古元古代、中元古代两期自亏损地幔分异的基性火山岩变质形成的斜长角闪岩。而模式年龄为新太古代的斜长角闪岩,其模式年龄能否代表其形成年龄还需要进一步研究。各期斜长角闪岩在地球化学特征上的差异表现得不明显。通过对其原岩性质研究表明:原岩主要为拉斑玄武岩,少数为钙碱性玄武岩。大别核部杂岩中斜长角闪岩原岩ε_(Nd)(t)反映出大别核部杂岩地区上地幔自古元古代到中元古代一直沿着亏损地幔 Nd 同位素的演化线演化发展,这种性质及演化趋势与扬子北缘及南秦岭早期上地幔 Nd 同位素性质及演化趋势十分     

内蒙古白乃庙铜矿床的成矿时代—来自SHRIMP锆石U-Pb和辉钼矿Re-Os年龄的新证据

摘要：内蒙古白乃庙铜矿床位于兴蒙造山系满都拉-霍林郭勒弧盆系白乃庙早古生代岛弧内,该矿床包括南、北两个矿带,南矿带矿体产于白乃庙组绿片岩中,北矿带矿体产于花岗闪长斑岩内,对于该矿床及白乃庙组的形成时代争议较大。本文采用锆石SHRIMP U-Pb同位素定年获得了白乃庙组第三岩性段绿泥斜长片岩的形成年龄为439.8±6.7Ma,花岗闪长斑岩的形成年龄为433.9±2.2Ma、451.8±3.0Ma,采用辉钼矿Re-Os同位素分析获得辉钼矿的形成年龄为433.9±3.1Ma。结合前人成果,提出白乃庙组地层和花岗闪长斑岩的成岩时代与白乃庙铜矿的成矿时代均为晚奥陶-早志留世,它们同属加里东期构造-岩浆作用的产物。 关键词：绿泥斜长片岩;花岗闪长斑岩;锆石SHRIMP U-Pb年龄;辉钼矿Re-Os同位素年龄;白乃庙铜矿     

山西铝土矿Rb-Sr同位素定年

采用Rb Sr全岩与粘土矿物等时线年龄方法测得山西五台剖面 (RS0 1) ,临县剖面 (RS0 2 )和孝义剖面 (RS0 3)的 3个含矿粘土岩的Rb Sr同位素年龄分别为 :316 .9± 1.2Ma ,87Sr/86Sr为 0 .710 5 4± 14 ;315 .5± 1.3Ma ,87Sr/86Sr为 0 .710 86±18;317.3± 1.1Ma ,87Sr/86Sr为 0 .710 5 0± 14。它们代表了铝土矿和含矿系列成矿的同位素年龄 ,相当于晚石炭世早期     

攀西地区二叠纪赋存铌钽矿的正长岩脉的成因探讨

攀西地区广泛发育正长岩脉,其中有些岩脉富含铌钽等稀有金属元素。这些岩脉多侵入于二叠纪辉长岩体中,并与该区玄武岩及长英质岩体共生。锆石U-Pb年代学表明这些正长岩脉与长英质岩体及辉长岩体形成时代相一致(258~256Ma),但是否有成因联系并不清楚。本文对攀西地区炉库和白草两个Nb-Ta矿区中的富矿正长岩脉、贫矿正长岩脉及相关正长岩体在进行了详细的岩石学、矿物学及主微量地球化学的基础上,又开展了全岩Sr-Nd同位素研究。研究表明,岩石的εNd(t)非常均一(富矿正长岩脉εNd(t)=-0.2~+0.2,贫矿正长岩脉εNd(t)=-0.3~+0.7,正长岩体εNd(t)=-0.3~+0.4);两矿区岩石初始86Sr/87Sr值同位素则表现出宽泛的范围,正长岩体和贫矿正长岩脉的(86Sr/87Sr)i分别变化于0.7032~0.7090和0.7044~0.7064,富矿正长岩脉的(86Sr/87Sr)i变化于0.7049~0.7091,较大的初始86Sr/87Sr比值可能由于岩石遭受一定程度的蚀变所致。本文两矿区的富矿正长岩脉及贫矿正长岩脉和正长岩体的Sr-Nd同位素特征,与攀西地区红格镁铁质/超镁铁质层状侵入体的一致(εNd(t)=-2.7~+1.0,(86Sr/87Sr)i=0.7058~0.7064),表明其与峨眉山玄武岩及镁铁质侵入体来自于相同的地幔源区。结合作者及其他研究者对本区正长岩脉和相关正长岩体的主微量地球化学研究,我们认为本区炉库和白草矿区的富矿正长岩脉及相关正长岩体可能是峨眉山地幔柱岩浆活动造成的底侵在下地壳底部的辉长质岩石低程度(5%~10%)部分熔融形成的产物,且较少受到地壳物质混染。     

青海省共和盆地周缘晚古生代镁铁质火山岩Sr-Nd-Pb同位素地球化学及其地质意义

青海省共和盆地周缘晚古生代镁铁质火山岩分属阿尼玛卿蛇绿混杂带,宗务隆构造带和苦海-赛什塘带。阿尼玛卿带正常洋中脊玄武岩(N-MORB)样品具有较高的~(87)Sr/~(86)Sr(t)比值(0.7066～0.7084)、高的ε_(Nd)(t)(12.2～12.8)和较低的~(206)Pb/~(204)Pb初始值(17.72～17.79)。这些同位素特征类似于秦岭勉略蛇绿岩带的N-MORB以及印度洋低~(206)Pb/~(204)Pb高~(143)Nd/~(144)Nd N-MORB。该带中的洋岛玄武岩(OIB)的~(87)Sr/~(86)Sr比值为0.7036～0.7044,ε_(Nd)(t)=4.4～4.8,~(206)Pb/~(204)Pb=17.45～17.62。其Sr和Nd同位素比值可与印度洋代表热点构造的洋岛玄武岩对比,但~(206)Pb/~(204)Pb低于印度洋的热点构造玄武岩,因此,具有类似印度洋低~(143)Nd/~(144)Nd比值MORB同位素特征。宗务隆构造带的N-MORB的Sr同位素比值在0.7041～0.7058,ε_(Nd)(t)=6.1～8.4,~(206)Pb/~(204)Pb=17.51～17.90,划归高~(143)Nd/~(144)Nd比值的N-MORB。苦海大陆裂谷玄武岩显示了高的~(87)Sr/~(86)Sr同位素比值(0.7115和0.7104)和低的ε_(Nd)(t)值(-1.7和-2.5),其~(206)Pb/~(204)Pb(17.64和17.46)与上述大洋玄武质岩石无显著区别。上述各岩类的同位素特征反映了它们生成的构造环境和陆壳组分混染的程度。阿尼玛卿带的N-MORB代表了典型的来自亏损地幔源区的洋中脊产物。与勉略带同类岩石可能来自同一源区。OIB可能属于热点构造成因的洋岛产物并与MORB一起构成了阿尼玛卿洋洋壳。宗务隆带MORB同样代表了主要源自相对亏损地幔的洋脊产物并指示宗务隆带曾开裂成洋。苦海大陆裂谷玄武岩极高的Sr和低的Nd同位素比值是陆壳物质组分的强烈印记,这与该类火山岩发育在前寒武纪基底之上不无关系。结合本区大洋玄武岩普遍低的Nb/U和Ce/Pb比值,推测它们可能源自EMII与DMM物质的交代混合。按照习惯的想法,明显的Dupal异常(△~(208)Pb/~(204)Pb值=46～103和△~(207)Pb/~(204)Pb值=4～18;大多样品~(87)Sr/~(86)Sr>0.704)指示这些岩石在空间上代表了来自南半球印度洋位置的古洋壳残余。但是,北半球愈来愈多的Dupal异常的发现有可能指示它们是类似现今东南亚多洋岛构造历经"汇聚式(focused)俯冲"的产物。此外,宗务隆带MORB的Dupal异常指示本区古特提斯域的北界较先前所定还要北推200km。     

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.     

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。     

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.     

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.     

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。     

岩石密度和超高压岩石折返速率

在常温常压条件下对中国大陆科学钻CCSD主孔100-3000米岩心样品进行了密度测量,建立了密度连续剖面,并界定了不同超高压岩石的密度值。通过对比高温高压物性实验资料,岩石密度随着退变程度增强而降低,榴辉岩密度变化序列为3.52g/cm3→3.49g/cm3→3.07g/cm3→2.93g/cm3。超高压长英质岩石密度变化序列为3.00g/cm→2.80g/cm3→2.65g/cm3。上述实验资料是讨论不同折返阶段岩石所受浮力的基础,为研究折返速率大小提供了基本参数。本文通过折返板块运动平衡时,上浮力与粘滞力平衡这一关系式,定量研究了大陆俯冲板块的折返速率,认为密度差产生上浮力从而引起折返,温度对板块折返速率的影响最为显著;密度差大小、折返角度、折返板块大小对折返速率也有直接的影响。定量模拟分析表明,在温度高于850℃时,板块的折返速率可以超过100mm/a;当温度降至700℃时,折返速率则低于1.5mm/a。作者认为在折返早期,温度较高,板块快速折返至60-70km榴辉岩相深度;随着传导散热,温度降低,板块以较慢的速率折返至中下地壳。折返速率的估算表明,浮力是板块折返第一阶段(从>100km深部折返至<40km的中下地壳)的主要驱动力。     

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.     

Mercury,arsenic, antimony,and selenium contents of sediment from the Kuskokwim River,Bethel, Alaska,USA

The Kuskokwim River at Bethel, Alaska, drains a major mercury-antimony metallogenic province in its upper reaches and tributaries. Bethel (population 4000) is situated on the Kuskokwim floodplain and also draws its water supply from wells located in river-deposited sediment. A boring through overbank and floodplain sediment has provided material to establish a baseline datum for sediment-hosted heavy metals. Mercury (total), arsenic, antimony, and selenium contents were determined; aluminum was also determined and used as normalizing factor. The contents of the heavy metals were relatively constant with depth and do not reflect any potential enrichment from upstream contaminant sources.     

滇东南花岗岩与锡、银、铜、铅、锌多金属矿床的成因关系

滇东南锡、银、铅、锌多金属矿床主要分布在个旧、白牛厂、都龙3个矿区,而滇东南较大的3个花岗岩体又分别出露在3个矿区或附近.花岗岩体均形成于燕山晚期,岩石化学、矿物成分相似,富含锡、银、铅、锌、钨、铜等成矿元素.矿床主金属元素组合与岩体之间的距离由远而近出现由锡、钨、(铍、铌、钽)→锡、钨、(铁)、铜、铟→锡、铅、锌、银、铟、(锑)有规律的变化.花岗岩浆是成矿物质来源和成矿热源.岩浆侵入初期使上覆地层隆起产生背斜(凹陷部位成向斜);同时使地层产生一系列裂隙、压性断层或层间断裂;岩浆侵入晚期,这些断层再次活动,表现为张性,岩浆产生的含矿热液沿由其活动所造成的断裂迁移、充填、交代、沉淀而形成矿床.