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1.
胶-辽-吉带辽东宽甸地区古元古代二长(正长)花岗质片麻岩的锆石U-Pb年代学、地球化学及成因 总被引：4，自引：1，他引：3
古元古代二长(正长)花岗质片麻岩在胶-辽-吉构造带广泛出露,是构成胶-辽-吉带的最主要物质组成。2件中细粒二长花岗质片麻岩样品及1件正长花岗质片麻岩样品的LA-ICP-MS锆石U-Pb年代学分析表明,它们分别形成于2.17Ga和2.33Ga,代表两期花岗质岩浆事件,并经历了约1.89Ga的变质作用。这些花岗质岩石具高硅(SiO_2=71.68%~76.38%),富铁(Fe_2O_3+FeO=1.61%~4.35%)及全碱(K_2O+Na_2O=7.57%~9.3%),K_2O/Na_2O比值大于1,贫钙(CaO=0.2%~1.6%)、镁(MgO=0.05%~0.24%,Mg#=3.82~13.0)、磷(P_2O_5=0.01%~0.06%)及钛(TiO_2=0.12%~0.4%)的特征;它们具有较高的稀土元素总量(ΣREE=104×10~(-6)~440×10~(-6)),具有轻微的轻重稀土分异,(La/Yb)_N比值在2~11之间,具明显的铕负异常(Eu/Eu*=0.30~1.18,平均值为0.56),具有低Sr(大部分100×10~(-6))、Rb(62.8×10~(-6)~187×10~(-6))、Cr及Ni含量,高的Zr(250×10~(-6))及Yb(2×10~(-6))含量,Zr+Nb+Ce+Y平均值为506×10~(-6),10000×Ga/Al值大于2.7;微量元素原始地幔标准化蛛网模式图显示,富集Rb、U、K、Zr、Hf等元素,亏损Nb、Ta、Sr及Ti等元素;它们属铁质、准铝质至弱过铝质、碱钙-钙碱性系列,全岩锆饱和温度大于800℃,属A2型花岗岩;结合胶-辽-吉带内古元古代花岗质片麻岩的全岩Nd及锆石Hf同位素研究结果,指示这些古元古代A型花岗岩可能形成于高温低压的伸展构造背景下,大陆物质(TTG岩石)的部分熔融。暗示胶-辽-吉带可能经历了古元古代早期多阶段的陆壳伸展拉张,并形成初始洋盆,然后再到洋-陆俯冲、陆(弧)-陆碰撞的演化过程。 相似文献
2.
柴北缘双口山石英正长岩锆石U-Pb定年、地球化学及Sr-Nd同位素特征 总被引：1，自引：0，他引：1
本文报道了柴北缘西段双口山地区石英正长岩锆石U-Pb年代学,全岩地球化学和Sr-Nd同位素等分析结果。石英正长岩岩体具有高硅(SiO_2=59.47%～68.66%)、碱性?过碱性(全碱含量为11.18%～14.04%),贫CaO(0.31%～3.30%)的特征。其里特曼指数σ为4.87～9.55、铝饱和指数(A/CNK)=1.12～1.36,属钾玄岩系列,过铝质范围。稀土元素总量高(ΣREE=231.31×10~(–6)～569.26×10~(–6)),富集轻稀土元素,亏损重稀土元素((La/Yb)_N=24.03～58.33),具弱Eu负异常(Eu/Eu*=0.72～0.95);微量元素亏损Ba、Sr、Ti、P,富集Rb、Th、U、Zr、Y和Ga,具有A型花岗岩特点,根据微量元素组成判别其产出于板内环境。锆石LA-ICP-MS U-Pb定年获得加权平均年龄为243.5±1.6 Ma,属中三叠世。样品的?_(Nd)(t)介于–1.08～–2.15,二阶段模式年龄t_(DM2)=1.10～1.19 Ga,表明其具有多源特征,是受到俯冲组分改造或影响的岩石圈地幔熔体和中新元古代变质基底熔体发生岩浆混合作用的结果,其形成与三叠纪古特提斯洋向北俯冲导致弧壳增厚和发生弧后拉裂有关。 相似文献
3.
伊春东风经营所新元古代花岗质片麻岩U-Pb年代学和地球化学特征 总被引：1，自引：0，他引：1
张广才岭中段东风经营所一带发现新元古代花岗质片麻岩,岩石具有高硅、富碱和低钙、镁及偏铝质-过铝质特点,稀土元素配分模式中轻稀土元素富集且缓向右倾斜,重稀土元素曲线较为平坦,为具有铕亏损的海鸥型,富集高场强元素Th、Zr、Hf,亏损Ba、Sr、P、Ti、Nb、Ta等大离子亲石元素,微量元素特征指示其形成于大陆地壳的部分熔融。锆石LA--ICP MS U--Pb定年结果表明,岩石加权平均年龄为(850.2±2.0)Ma,形成于新元古代。构造环境显示研究区花岗质片麻岩形成于挤压造山环境,为造山期的深熔产物。新元古代花岗质片麻岩的发现,表明研究区之前存在一古老的微陆块。 相似文献
4.
北苏鲁超高压变质带内多成因类型的变花岗质岩石及其地质意义 总被引：1，自引：1，他引：0
变花岗质岩石是北苏鲁超高压变质带出露最广泛的岩石类型。本文通过锆石年代学和全岩地球化学的系统研究,查明该区变花岗质岩石具有成因类型多样性的特点,揭示其构造归属的复杂性,这对于解释扬子板块与华北板块之间的俯冲-碰撞-折返动力学过程具有重要科学意义。锆石U-Pb定年结果表明,区内的变花岗质岩石由新元古代(820～750Ma)花岗质片麻岩和新太古代-古元古代(2700～1870Ma)TTG-花岗质片麻岩共同组成,且二者经历了完全不同的构造演化历史。其中,新元古代花岗质片麻岩经历了晚三叠世(222～213Ma)的变质-深熔事件,而新太古代-古元古代的TTG-花岗质片麻岩则记录了晚古元古代(～1864Ma)的变质事件。全岩地球化学结果表明,新元古代花岗质片麻岩的原岩成分趋近于A型花岗岩,属于过铝质-准铝质的高钾钙碱性系列,主量元素(AlT_2O_3、MgO、FeO、TiO_2、CaO、P_2O_5)与SiO_2显示负相关性,具有轻、重稀土分异和负Eu异常特征,表明其源区有斜长石的残留。富集大离子亲石元素和强烈亏损高场强元素的特点,进一步表明它们可能是中-上地壳物质部分熔融的产物。新太古代-古元古代TTG-花岗质片麻岩的原岩成分主要落入TTG和IS型花岗岩区域,属于低钾-钙碱性系列,主量元素与SiO_2相关性不明显,多数样品的稀土总量比新元古代花岗质片麻岩略低,轻、重稀土分异相对较弱,具有正Eu或无Eu异常,表明其源区无斜长石而可能有角闪石的残留。它们的地球化学属性与新元古代花岗质片麻岩的成因特点存在显著差异。古元古代花岗质片麻岩的原岩可能为与造山有关的I型花岗岩,来自于太古宙基底岩石的重熔与再造。上述综合研究结果显示,北苏鲁超高压变质带内新元古代花岗质片麻岩的原岩具有亲扬子板块的属性,与扬子板块北缘罗迪尼亚超大陆裂解存在密切成因关系。而新太古代-古元古代TTG-花岗质片麻岩与华北板块变质基底、胶-辽-吉古元古构造带具有明显亲缘性。由此可见,在传统北苏鲁超高压变质带内的威海-乳山一带,由具有扬子板块属性和具有华北板块属性的变质基底,沿北东-南西方向共同组成了一条北苏鲁混杂岩带。这一新的研究成果充分表明,华北板块东南缘的新太古代-古元古代的陆壳物质普遍卷入到三叠纪时期扬子板块与华北板块之间的相向(双向)俯冲-折返造山过程中。 相似文献
5.
华北克拉通五台地区2.2～2.1Ga花岗岩的成因与构造背景 总被引：6，自引：6，他引：0
华北克拉通中部造山带内古元古代中期(2.2~2.0Ga)岩浆活动较为广泛,对探讨华北古元古代地质演化过程具有十分重要的意义。本文选择了五台地区古元古代大洼梁、王家会和莲花山花岗岩进行了地球化学、锆石U-Pb年代学和Hf同位素研究。大洼梁似斑状花岗岩SHRIMP锆石U-Pb年龄为2170±17Ma,王家会二长花岗质片麻岩LA-ICPMS锆石U-Pb年龄结果为2101±6Ma,3个莲花山花岗岩的LA-ICPMS锆石U-Pb年龄结果分别为2117±6Ma、2110±4Ma和2143±15Ma。大洼梁花岗岩高SiO_2、富K_2O+Na_2O,低CaO,稀土元素含量较高(Eu除外),Zr、Nb、Ga和Y等高场强元素含量也较高,而Sr含量极低;同时Ga/Al比值和Zr+Nb+Y+Ce总量高,全岩Zr饱和温度高达876～968℃。该花岗岩体具有A型花岗岩的特征。王家会花岗岩和莲花山花岗岩样品也具有高硅、富碱和低镁钙特征,稀土元素具有弱到较强烈的分异,Eu负异常明显。3个花岗岩岩体微量元素都具有较高的Nb和Y值,因此具有后碰撞到板内花岗岩特征。所有花岗岩样品中锆石的εHf(t)值均远低于同期亏损地幔值,同时单阶段和两阶段模式年龄为2.4～2.6Ga和2.45～2.75Ga,明显大于花岗岩的成岩时代。这些花岗岩与五台地区新太古代晚期TTG质片麻岩具有相似的锆石Hf模式年龄。因此,结合岩石学、地球化学和同位素特征,本文倾向于认为古元古代花岗岩为新太古代TTG质片麻岩在伸展条件下部分熔融形成的。综合资料发现,华北克拉通中部带内2.2～2.0Ga岩浆事件不同地区表现有分带性。2.2～2.1Ga岩浆活动代表较早的阶段,其中部分花岗质岩石具有A型花岗岩特征,与同期的基性岩形成双峰式组合,推断其与华北克拉通古元古代中期陆内裂谷有关。 相似文献
6.
青海省阳康地区花岗岩岩石组合为细粒石英闪长岩、黑云母花岗闪长岩。通过对岩石地球化学分析发现,SiO_2含量为54.36%～70.16%,Al_2O_3含量为13.08%～17.01%,K_2O含量为1.57%～3.91%,Na_2O含量为2.37%～3.75%,CaO含量为1.91%～8.09%,里特曼指数σ为1.5～2.61,属偏铝质-过铝质钙碱性花岗岩;稀土总量(∑REE)为121.7×10~(-6)～458×10~(-6),LREE/HREE值为6.81～14.72,表现为轻稀土富集型,δEu值为0.46～1.16,Eu亏损明显,δCe略亏损;富集大离子亲石元素(Rb、Ba、K)和轻稀土元素(La、Ce、Nd),亏损重稀土元素(Yb、Lu)和高场强元素(Nb、Ta),具有明显的Eu和Sr、P、Ti的亏损。在石英闪长岩和花岗闪长岩中分别获得LA-ICP-MS锆石U-Pb年龄分别为(455.5±1.1)Ma和444Ma,形成时代为晚奥陶世。通过构造环境分析,认为阳康地区花岗岩是由挤压向拉伸环境转换的张驰阶段的岩浆侵位,属同造山花岗岩。 相似文献
7.
华北克拉通东部造山带内古元古代中期(2.1～2.2Ga)岩浆记录了造山带早期重要的地壳演化信息,对探讨辽吉造山带古元古代地质演化过程具有十分重要的意义。本文选择了辽东黑沟地区古元古代碱长花岗岩进行岩石学、地球化学、锆石U-Pb年代学和Hf同位素研究。黑沟碱长花岗岩LA-ICP-MS锆石U-Pb测年结果为2186.5±6.5Ma,形成时代为古元古代。岩石为碱性、弱过铝质A型花岗岩,岩石富硅、碱,贫钙、镁、铝,极度富钠贫钾,富集Hf、Zr、Nb、Y等高场强元素,亏损Rb、K、Ba等大离子亲石元素,具有较高的(K_2O+Na_2O)/Al_2O_3、FeO~T/MgO、Ga/Al比值,负的Eu异常,稀土元素配分曲线呈右倾海鸥型配分模式。锆石饱和温度介于857～884℃之间,同时具有非常低Sr高Yb特征,指示岩石形成于低压高温的伸展构造背景。锆石ε_(Hf)(t)值为-0.96～+4.58,二阶段模式年龄t_(DM2)=2476～2821Ma,明显大于花岗岩的成岩时代,结合岩石地球化学特征指示黑沟碱长花岗岩岩浆源于太古宙TTG片麻岩在地壳浅部伸展条件下的部分熔融。综合区域已有的岩石学、地球化学和同位素特征等资料,辽吉地区在古元古代早期可能处于大陆弧后盆地构造环境,黑沟碱长花岗岩是弧后盆地伸展环境下的产物。 相似文献
8.
华北克拉通北缘中段古元古代强过铝质花岗岩地球化学特征及其构造意义 总被引：3，自引：2，他引：3
华北克拉通北缘中段沿集宁-凉城-千里山一线分布着大量的强过铝质花岗岩.与一般强过铝质花岗岩相比,其SiO2含量、Al2O3/TiO2比值(小于100)、Rb/Sr比值和Rb/Ba比值低,但CaO/Na2O比值高(大于0.3).稀土元素复杂,正Eu异常、负Eu异常、Eu异常不明显均发育,大致可以分成2种类型:第一类具有中等程度轻稀土富集、重稀土平缓;第二类轻稀土特征与第一类一致,但其重稀土变化大.稀土元素特征不一致主要是由于其源岩不同.LILE(K、Rb、Ba)相对富集,HSFE(Nb、Ti、P)亏损,这种地球化学特征暗示该区强过铝质花岗岩的源区成分为杂砂岩,熔融温度较高,来源较深,其构造环境与澳大利亚拉克伦造山带一致,属高温型碰撞带,应为华北克拉通西部陆块和东北陆块古元古代碰撞峰期后岩石圈伸展的产物. 相似文献
9.
大兴安岭北段扎兰屯哈多河“花岗质糜棱片麻岩”年代学及地球化学特征研究 总被引：2，自引：0，他引：2
哈多河“花岗质糜棱片麻岩”为一套变质变形的花岗质岩石,其岩石组合为细粒黑云母二长花岗质糜棱片麻岩、细粒黑云母花岗质糜棱片麻岩和细粒石榴二云母花岗质糜棱片麻岩.SiO2含量在66.4％～74.52％之间,K2O+ Na2O介于7.36％～8.84％之间,Al2()3含量在13.43％～15.74％之间,A/CNK =0.974～1.092,属于高钾钙碱性、准铝质到过铝质岩石;具有较高的稀土总量(ΣREE=94.15×10-6～164.30×10-6),稀土元素配分模式表现为轻稀土元素(LREE)富集、重稀土元素(HREE)相对亏损的右倾型曲线,具有弱的负铕异常;富集Rb、Ba、U、K等大离子亲石元素,相对亏损Ta、Nb、P、Ti等元素.锆石U-Pb测年结果表明,哈多河“花岗质糜棱片麻岩”的岩浆侵入期次可分为两期,第一期在320Ma左右,代表性岩石为细粒黑云母花岗质糜棱片麻岩和细粒石榴二云母花岗质糜棱片麻岩;第二期在304Ma左右,代表性岩石为细粒黑云母二长花岗质糜棱片麻岩.综合岩相学、年代学及岩石地球化学特征,哈多河“花岗质糜棱片麻岩”原岩为高钾钙碱性Ⅰ型花岗岩,形成于晚石炭世兴安地块与松嫩地块的后碰撞构造环境下,之后在早二叠世末遭受“后碰撞作用”的影响,发生较强的韧脆性变质变形. 相似文献
10.
内蒙古格勒敖包位于兴蒙造山带内,对该区奥陶纪岩浆岩的研究,有助于进一步认识该造山带早古生代的构造格局及其演化。正长花岗岩和斑状二长花岗岩样品LA-ICP-MS锆石年龄为441.6±3.7～454.9±4.6Ma,形成时代为奥陶纪。经地球化学分析,岩体为高钾钙碱性系列;铝饱和指数显示其为过铝质花岗岩。岩石富集大离子亲石元素(LILEs)Rb、Th、U、K,亏损Ba、Sr;富集高场强元素(HFSEs)La、Ce、Nd、Zr,亏损Nb、P、Ti;稀土元素总量为38.7×10~(-6)～120.23×10~(-6),轻稀土元素较重稀土元素分异明显,分馏程度较高,表现出较弱的负Eu异常。综合区域地质资料,认为格勒敖包奥陶纪岩浆源区为上地壳物质的部分熔融,其形成环境为弧后盆地,在古亚洲洋向北俯冲之后经历了岛弧岩浆作用旋回,为弧后伸张阶段的产物。 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
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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
14.
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
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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
17.
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.
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
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.
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