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1.
中河花岗斑岩体位于河南省崤山东部,该岩体是最近发现的中河大型银铅锌矿床的成矿母岩。选取2件花岗斑岩样品进行LA-ICP-MS锆石U-Pb定年,获得2件样品的~(206)Pb/~(238)U年龄加权平均值分别为(129±0.7)Ma(MSWD=0.78)和(131±1.5)Ma(MSWD=1.70),表明中河岩体形成于早白垩世。岩石地球化学特征显示,中河岩体具有高的w(SiO_2)和w(K_2O)、低的w(Na_2O),其A/CNK比值为1.03~1.63,Mg#值介于25~50,总体上属于过铝质-强过铝质的高钾钙碱性系列。岩石具有低的w(Yb),中等-弱的铕负异常,稀土元素配分曲线为轻稀土元素富集型,轻稀土元素分馏相对强烈,但重稀土元素分馏不明显。中河岩体有相对低的w(Sr)和w(Y),且富集大离子亲石元素Rb、Ba、U、K和轻稀土元素,亏损高场强元素Nb、Ta、P、Zr、Hf、Ti和重稀土元素。中河岩体锆石εHf(t)值为-34.4~-23.2,平均为-26.9,Hf同位素二阶段模式年龄介于2485~3182 Ma,平均为2714 Ma。岩石地球化学特征及Hf同位素组成表明中河岩体的岩浆源区主要为新太古代地壳物质,并有少量的中太古代地壳物质,中-新太古代增生的具有弧岩浆特征的地壳物质部分熔融形成了早白垩世的中河岩体。 相似文献
2.
以赣西地区蒙山岩体为研究对象,通过对该岩体地球化学、锆石U-Pb年龄及Hf同位素的研究,探讨其岩浆物质来源及构造背景。该岩体经历了印支期、燕山期岩浆侵入活动,形成六种岩石类型,LA-ICP-MS锆石U-Pb年龄分别为224.0±2.10 Ma(n=19,MSWD=1.9)、223.0±2.20 Ma(n=21,MSWD=2.6)、222.0±2.80 Ma(n=21,MSWD=2.7)、220.0±1.90 Ma(n=16,MSWD=1.5)、217.0±3.70 Ma(n=8,MSWD=1.8)、142.0±0.98 Ma(n=21,MSWD=1.4),表明岩体经历了印支期、燕山期两期岩浆活动。印支期花岗质岩石地球化学具高硅富钾、准铝-过铝质特征;微量元素富集高场强元素Zr、Hf、Th、U和稀土元素La、Ce、Sm、Nd、Y,明显亏损Rb、Ba、Sr、Ti、P;稀土元素分馏程度不高,δEu介于0.03~0.15,具强Eu负异常,Ce异常不明显,稀土配分曲线呈“V”型;为同源岩浆演化的特点。CaO/Na_(2) O比值<0.3、Rb/Sr>5,岩石二阶段模式年龄T DM2主体介于868~1465 Ma,为中-新元古代,εHf(t)对应的T DM2值显示,岩体物源起源于成熟地壳,后期有大量新生地壳物质的加入,表明岩石来源于含水矿物(如白云母、绿帘石/黝帘石)的脱水反应导致成熟度高地壳物质的熔融而形成。在花岗岩构造环境判别图上,投于碰撞大地构造背景上的花岗岩和造山后花岗岩类(POG)区域,锆石U-Pb年龄表明成岩时段滞后于印支运动高峰期(258~243 Ma),为受印支运动造成华南地壳加厚滞后,地壳进入伸展阶段,减压熔融形成的花岗质岩浆。 相似文献
3.
华北陆块南缘外方山店房金矿区内出露后沟、水漉塘和店房钾长花岗斑岩体(脉),其与隐爆角砾岩筒及金矿化有密切的空间关系。为查明钾长花岗斑岩体的侵位时代、岩石成因和源区性质,本次开展了锆石U-Pb定年、锆石Hf同位素及岩石地球化学分析等研究。结果表明岩体具有高硅、高钾、富铝、低镁的特征,属钾玄岩系列Ⅰ型花岗岩,轻重稀土元素分馏明显,具有弱的Eu负异常,岩石富集Rb、K、Ba等,亏损Nb、Ta、Sr、P、Ti等元素。锆石具有核—边结构,其中锆石边SHRIMP U-Pb年龄142.6±2.1Ma(MSWD=1.4),_(εHf)(t)=-23.0~-13.8,两阶段模式年龄主要集中于2075~2652 Ma;锆石核LA-ICPMS U-Pb年龄可分为两组,即2169~2336Ma和1732~1881Ma,Hf同位素组成可分为两组,_(εHf)(t)分别集中于-13.1~-4.8和-4.5~3.7,模式年龄主要集中于2376~2805Ma。表明钾长花岗斑岩体形成于142.6±2.1Ma的早白垩世早期,岩浆可能由2169~2336Ma的古老下地壳新太古代太华群部分熔融而成,并有地幔组分参与,岩浆在上升或定位过程中捕获了1732~1881Ma熊耳群火山岩的锆石。结合区域构造背景认为,该岩体是早白垩世古太平洋板块向欧亚大陆俯冲致使华北陆块岩石圈减薄伸展而引起的岩浆活动的产物。 相似文献
4.
安徽茂林岩体为中国东部中生代皖南构造-岩浆带中的一个浅层侵入岩体,是檀树岭钼矿和湛岭钼矿的成矿母岩。该岩体的主要岩性为花岗闪长岩、花岗斑岩、斑状花岗闪长岩、二长花岗岩等。对茂林花岗闪长岩体进行LA-ICP-MS锆石UPb测年,结果显示锆石Th/U值为0.38~0.66,为典型的岩浆成因锆石。花岗闪长岩~(206)Pb/~(238)U年龄加权平均值为140.8±0.8Ma(n=19,MSWD=2.3),结合锆石自形、岩浆环带发育等特点,该年龄为茂林花岗闪长岩的成岩年龄,显示岩体形成于早白垩世。锆石Hf同位素分析结果显示,茂林花岗闪长岩锆石振荡岩浆环带具负εHf(t)值(-9.7~-6.2),揭示花岗闪长岩主要形成于下地壳的熔融。 相似文献
5.
在野外地质调查工作的基础上,对日土县—拉梅拉山口一带的日松花岗岩体开展了详细的岩相学、岩石地球化学、锆石U-Pb测年和Hf同位素分析。岩石地球化学数据表明,日松花岗岩体属钙碱性岩类型,绝大多数样品含透辉石标准分子。富集Rb、Pb、Th等而亏损K、Ba等大离子亲石元素,高场强元素Nb、Ta、Ti等明显亏损。稀土元素呈现出右倾缓倾斜型的特征,且存在较为明显的负Eu异常。与前人研究确定岩体的时代为晚白垩世—始新世不同,本文认为岩体的侵位时代主要为白垩纪,可分为早白垩世、晚白垩世两期。获得二长花岗岩样品(D1045-2)的LA-ICP MS锆石U-Pb年龄为108.4±2.1Ma(MSWD=2.4,n=18),结合锆石稀土元素特征、岩浆振荡环带特征(CL图像)及锆石Th/U比值,上述年龄可以代表岩体的形成年龄(早白垩世)。锆石Hf同位素特征显示,二长花岗岩样品(D1045-2)的εHf(t)为正值,介于1.49~3.86间(平均值为2.50);而石英闪长岩样品(D1045)的εHf(t)多数为负值,介于-2.09至0.15之间(平均值为-0.69)。Hf同位素地壳模式年龄分别在763.0~884.5Ma(D1045-2)、959.1~1073.5Ma(D1045)之间。两件样品的εHf(t)和Hf同位素地壳模式年龄均具有较小的变化范围,暗示岩体的岩浆物质来源应该具有较为均一的锆石Hf同位素组成。日松地区早白垩世花岗岩体的锆石U-Pb年龄和Hf同位素特征,基本反映了北冈底斯早白垩世的岩浆活动时间和源区等特征,其成因可能与班公湖-怒江特提斯洋岩石圈向南俯冲过程中幔源物质参与岩浆形成演化有关。本文研究成果,为研究班公湖-怒江结合带构造演化提供了新的资料证据。 相似文献
6.
紫金山矿田位于华南褶皱系东部,闽西南凹陷西南部,是我国大型-超大型浅成低温热液铜金矿床,区内发现多个与岩浆活动密切相关的金、银、铜等金属矿床.对紫金山矿田东南矿段与成矿密切相关的细粒黑云母花岗岩开展了详细野外地质调查、岩相学和锆石稀土元素、U-Pb年代学和Hf同位素研究.LA-ICP-MS法获得细粒黑云母花岗岩中岩浆结晶锆石206Pb/238U-207Pb/235U谐和年龄为109.5±1.9 Ma（MSWD=0.74,N=16）,206Pb/238U加权平均年龄为107.44±0.94 Ma（MSWD=1.06,N=16）,二者在误差范围内结果一致,结合锆石稀土元素和岩浆振荡环带特征及Th/U比值,上述年龄结果可代表岩石的结晶年龄,表明细粒黑云母花岗岩侵位于燕山期早白垩世.细粒黑云母花岗岩锆石Hf同位素初始比值εHf（t）均为负,介于-4.99~-1.06（平均值为-2.99）;两阶段Hf模式年龄（tDM2）介于1 233.7~1 485.4 Ma（平均值为1 362.4 Ma）.样品的εHf（t）、Hf同位素地壳模式年龄分布范围变化较小,暗示岩体的岩浆来源具有较为均一的锆石Hf同位素组成.紫金山矿田东南矿段早白垩世花岗岩体的锆石U-Pb年龄和Hf同位素特征,反映了闽西南早白垩世的岩浆成矿活动时间和源区特征,其成因与中国东南部岩石圈伸展减薄和壳源物质参与岩浆形成演化密切相关. 相似文献
7.
大别山千鹅冲钼矿区花岗岩的SHRIMP锆石U-Pb年龄、Hf同位素组成及微量元素特征 总被引：2，自引：1，他引：1
千鹅冲斑岩型钼矿床位于东秦岭-大别钼矿带东部的大别山地区。矿体主要赋存于千鹅冲隐伏花岗岩体上部(外接触带)的南湾组片岩中,少量产于花岗岩体内。矿体下部的隐伏岩体中主要见有二长花岗岩和花岗斑岩。SHRIMP锆石UPb定年表明,二长花岗岩和花岗斑岩的侵位年龄分别为130±2Ma(MSWD=1.4)和129±2Ma(MSWD=1.9),二者年龄一致,说明隐伏岩体形成于早白垩世。锆石Hf同位素分析结果表明,千鹅冲钼矿中二长花岗岩和花岗斑岩的εHf(t)值分别变化于-24.5～-2.7和-19.8～-11.2之间,变化范围较大,说明它们主要来源于古老地壳的部分熔融,也有年轻组分的参与。两阶段模式年龄(t DM2)和古元古代的继承锆石指示这些花岗岩的原岩中含有古元古代-太古代的基底岩石。二长花岗岩和花岗斑岩中的锆石的Ce4+/Ce3+比值平均值分别为287.4和55.9,说明形成二长花岗岩的岩浆具有更高的氧逸度,但钼成矿与形成较晚的花岗斑岩具有更紧密的成因联系。千鹅冲钼矿形成于大别造山带早白垩世的伸展构造体制下,造山带下地壳拆沉作用造成的软流圈上涌和壳幔相互作用可能为钼矿的形成提供了成矿物质。 相似文献
8.
马其岗石英二长斑岩体出露于桂东南博白-梧州断裂带南东侧,对其开展了锆石U-Pb年代学、地球化学、Sr-Nd-Hf同位素及成因研究。结果表明,岩体LA-ICP-MS锆石U-Pb年龄为90.2±1.5Ma(MSWD=1.7)。岩体富碱(ALK=7.38%~8.14%)、富钾(K_2O=4.41%~4.78%),稀土元素特征为轻稀土元素富集型,微量元素特征为富集大离子亲石元素(Rb、Th、U、K、Pb、LREE),亏损高场强元素(Nb、Ta、P、Ti、HREE),符合钾玄岩系列的岩石特点。岩体有较高的Mg~#值(42.82~50.35),较低的Sr含量(268.00×10~(-6))~304.00×10~(-6)),以及较高的锆石饱和温度(860~883℃),同时Nb/Ta(平均值为11.24)、Zr/Hf(平均值为38.20),Th/La值(平均值为0.17)明显不同于大陆地壳特征,表明岩浆主要来自下部地壳或地幔,在上升侵位过程中受到地壳大规模混染程度较小,具有EMⅡ富集地幔端元的Sr-Nd同位素特征。二阶段Nd模式年龄(t_(DM2))变化于1.33~1.36Ga之间,二阶段Hf模式年龄(t_(DM2))主体为1.20~1.50Ga,两者模式年龄较一致,显示马其岗岩体可能是中元古代中期镁铁质岩石部分熔融的产物。石英二长斑岩形成于板内伸展环境,整个华南在90Ma左右存在一次大规模的伸展事件,其动力学机制与古太平洋板块低角度俯冲有关。 相似文献
9.
内蒙古卓资县大苏计斑岩钼矿化与区内花岗质杂岩(石英斑岩、正长花岗斑岩和花岗斑岩)有密切的成因联系。LA-ICP-MS锆石U-Pb定年获得石英斑岩、正长花岗斑岩和花岗斑岩的结晶年龄分别为(234±3)Ma、(225±4)Ma和(220±4)Ma。杂岩体富硅(w(SiO_2)=70.37%~78.84%)、富碱(w(Na_2O+K_2O)=4.52%~8.77%),均属高钾钙碱性系列,普遍具有低的w(Na_2O)(0.15%~2.69%)和高的铝指数(ASI介于1.13~3.35)。稀土元素总量介于48.2×10~(-6)~527.0×10~(-6),石英斑岩稀土元素含量(48.2×10~(-6)~83.1×10~(-6))最低,正长花岗斑岩稀土元素含量(272.1×10~(-6)~527.0×10~(-6))最高,花岗斑岩稀土元素含量为162.5×10~(-6)~236.8×10~(-6);杂岩体δEu介于0.15~0.93之间,(La/Yb)N介于3.0~65.5,自正长花岗斑岩、花岗斑岩到石英斑岩,其Eu负异常逐渐増大,而(La/Yb)N逐渐减小。岩体普遍富集Rb、Th、U、K、Nd、Zr、Hf等,强烈亏损Sr、P、Ti等。正长花岗斑岩具有中等Ba、Ta、Nb亏损。石英斑岩和花岗斑岩均属于高分异花岗岩,而正长花岗斑岩属于I型花岗岩。主量、稀土和微量元素特征表明,杂岩体具有后碰撞或后造山花岗岩特征,形成于后碰撞或后造山环境。杂岩体锆石的Hf同位素显示,3种岩石的εHf(t)值介于-21.1~-8.1,二阶段模式年龄tDM2介于1775~2587 Ma。石英斑岩来自于古元古代地壳物质的部分熔融;正长花岗斑岩来自于古元古代晚期地壳物质的部分熔融;花岗斑岩也主要来自于古元古代地壳物质的部分熔融,但有少量新太古代地壳物质参与。 相似文献
10.
伊朗乌尔米耶-达克塔尔弧岩浆带(Urumieh-Dokhtar magmatic arc,UDMA)是特提斯域最重要的斑岩铜矿省,发育大量中新世大型超-大型斑岩铜矿床;同时,该带也发育大量同时代无矿岩体,但控制岩体成矿潜力的关键因素尚不清楚.为此,选择该带中段、成矿及无矿岩体同时发育的大理矿区,针对成矿及无矿岩体开展了系统的锆石岩相学、年代学、微量元素地球化学及Hf同位素地球化学对比.结果显示,无矿闪长岩(锆石U-Pb年龄:17.4±0.3 Ma)比成矿石英闪长斑岩(锆石U-Pb年龄:15.6±0.1 Ma)形成略早,但近乎同期;闪长岩εHf(t)值变化介于+2^+4,石英闪长斑岩εHf(t)值变化介于+2^+5,两者具有类似的Hf同位素组成;闪长岩中锆石常含老的继承核(172~920 Ma),石英闪长斑岩则不发育继承锆石;闪长岩及石英闪长斑岩中的中新世锆石具有类似的稀土配分模式,且Eu负异常不明显,而闪长岩中的锆石继承核则显示出明显的Eu负异常,配分模式与中新世锆石不同.基于上述结果,我们提出大理矿区的两套中新世岩体具有相同的岩浆源区,但经历了不同的地壳演化过程,成矿的石英闪长斑岩浆形成后,与古老地壳没有明显交互,而无矿的闪长岩浆,在上升过程中与地壳物质、特别是古老还原性物质发生了交互,交互过程中岩浆氧逸度降低,是该套岩浆不成矿的主要原因.进而我们提出UDMA带中段斑岩成矿与否不仅与前人所认为的受岩浆源区控制,也与岩浆演化过程密不可分. 相似文献
11.
S. Viswanathan K. Surya Prakash Rao B. Mahabaleswar 《Journal of the Geological Society of India》2013,82(6):621-627
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. 相似文献
12.
奥地利安东帕有限公司 《岩矿测试》2009,28(3):306-306
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 相似文献
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E. M. Prasolov S. A. Sergeev B. V. Belyatsky E. S. Bogomolov K. A. Gruzdov I. N. Kapitonov R. Sh. Krymsky V. O. Khalenev 《Geochemistry International》2018,56(1):46-64
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. 相似文献
15.
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. 相似文献
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岩石密度和超高压岩石折返速率 总被引：1，自引：3，他引：1
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。 相似文献
18.
Alexander E. C. Broberg J. S. Kehren A. R. Graziani M. M. Turri W. L. 《Environmental Geology》1993,22(4):353-361
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. 相似文献
19.
Mercury,arsenic, antimony,and selenium contents of sediment from the Kuskokwim River,Bethel, Alaska,USA 总被引：1，自引：0，他引：1
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. 相似文献
20.
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. 相似文献