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。     

西藏类乌齐片麻状黑云二长花岗岩锆石U-Pb定年、地球化学特征及地质意义

利用LA-ICP-MS锆石U-Pb测年技术,对藏东他念他翁山类乌齐地区侵入吉塘岩群恩达岩组片麻状黑云二长花岗岩进行测年,获得岩浆结晶年龄为(235.7±0.68)Ma(中三叠世),为藏东他念他翁山地区印支运动提供地质记录。岩石地球化学分析表明,片麻状黑云二长花岗岩SiO2含量为74.02%~77.47%,(K2O+Na2O)-SiO2图解中落入亚碱性花岗岩区,FeOT/MgO-SiO2图解中落入钙碱性区域,SiO2-FeOT/(FeOT+MgO)图解中落入铁质区。A/CNK指数为1.41,属过铝质高钾钙碱性系列花岗岩。稀土分布模式为轻稀土富集的右倾曲线,Eu具明显负异常(δEu=0.05~0.35)。微量元素表现出Ba,Sr,Zr,Hf亏损,Rb,Th,U相对富集特征。据CaO/Na2O比值、Rb-Sr-Ba含量变化及地球化学特征,该岩体形成于上地壳,源岩为泥质岩石花岗质岩浆。结合地球化学特征及区域地质背景认为,藏东他念他翁山地区侵入恩达岩组片麻状黑云二长花岗岩属S型花岗岩,形成于后碰撞地球动力学环境。     

新疆西天山天山乡南部片麻状花岗闪长岩锆石U-Pb年代学、地球化学特征及构造意义

新疆西天山天山乡地区大面积分布片麻状花岗闪长岩,含较高的Na_2O+K_2O,A/CNK为0.74~0.97,为准铝质、钠质,成因类型为I型花岗岩,稀土元素富集、重稀土亏损的右倾型分布模式,δEu在弱片麻状似斑状花岗闪长岩中呈中等负异常,在强片麻状花岗闪长岩中基本无异常;微量元素总体富集大离子亲石元素,亏损高场强元素,Ba,Rb,K,Nb,Ta,Ti元素呈明显的亏损特征,具岛弧火山岩特征;锆石U-Pb年龄为(321.9±1.2)Ma,为早石炭世晚期。综合野外地质观察、区域地质构造,认为天山乡南部片麻状花岗闪长岩形成于南天山洋闭合时期,岛弧基本消亡逐渐向陆陆碰撞的过渡阶段。     

西藏羌塘南缘青草山北花岗闪长岩锆石U-Pb年代学、地球化学特征及其成矿意义

青草山北花岗闪长岩体位于班公湖-怒江缝合带北侧、羌塘陆块南缘,呈岩脉、岩株状与晚二叠世龙格组碳酸盐岩呈侵入接触。本文对该花岗闪长岩的锆石进行了LA-ICP-MS U-Pb年代学和岩石地球化学研究,其岩浆锆石U-Pb年龄为154.8±1.2Ma(MSWD=1.7),属晚侏罗世,与热那错埃达克质英安岩年龄高度一致,岩石地球化学特征显示,青草山北花岗闪长岩属于准铝质、高钾钙碱性系列,富集轻稀土元素、大离子亲石元素,亏损重稀土元素、高场强元素,具弱Eu负异常,显示出典型岛弧岩浆岩特征;锆石原位微量元素分析表明,锆石总体富集重稀土,相对亏损轻稀土,在锆石Nb/Ta-Y图解中样品点落入金伯利岩区域,而在岩石地球化学构造环境判别图解中,样品点同样指示其可能来源于幔源岩浆。青草山北花岗闪长岩班公湖-怒江洋壳晚侏罗世北向俯冲到一定深度后,俯冲洋壳发生部分熔融,形成的岩浆在上升的过程中与地幔楔发生混染,其中,部分岩浆在侵位的过程中形成中酸性的花岗闪长质岩浆房,部分岩浆则喷出地表,形成热那错组英安岩。     

柴达木盆地西北缘石英闪长岩的形成时代、岩石成因及地质意义

柴达木盆地西北缘石英闪长岩Al2O3含量较高,全碱(Alk)含量较低,Na2OK2O,铝饱和指数A/CNK为0.87~0.91,属钙碱性准铝质岩石系列。球粒陨石标准化的稀土元素配分曲线表现为轻稀土元素富集型,轻、重稀土元素分馏明显,Eu弱负异常;微量元素地球化学特征显示,岩石富集Rb、Th、U等大离子亲石元素,亏损Nb、Ta、P、Ti等高场强元素,Nb/La和Rb/Nb比值较低,具有I型花岗岩的特征。石英闪长岩Ca O/Na2O比值较高(2.32~2.64),结合源岩判别图解综合推断其源于变玄武岩的部分熔融。全岩Zr饱和温度计算结果显示初始岩浆温度768℃;岩石地球化学特征表明岩浆源区压力1.5 Ga,源岩部分熔融的残留相可能为石榴子石+角闪石+金红石。经过锆石阴极发光分析和MC-LA-ICP-MS锆石U-Pb测年,获得206Pb/238Pb加权平均年龄为252±1 Ma,代表了柴达木盆地西北缘石英闪长岩的成岩年龄。结合区域地质演化特征,认为该岩体形成于与板块俯冲有关的火山弧构造环境,是晚二叠世末期宗务隆洋壳向柴北缘欧龙布鲁克地块俯冲,变玄武岩在相对较高的温压条件下发生部分熔融形成的。     

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。     

哀牢山构造带南段马玉花岗闪长岩地球化学特征及其锆石U-Pb年龄

对云南墨江县马玉花岗闪长岩进行了锆石U-Pb年龄和岩石地球化学分析。LA-ICP-MS锆石U-Pb测年显示,马玉花岗闪长岩年龄为263.6±2.4Ma,形成于晚二叠世。岩石地球化学显示,马玉花岗闪长岩SiO_2含量为59.56%～70.50%,全碱(Na_2O+K_2O)含量为5.16%～7.92%,且Na2OK_2O;岩石富集轻稀土元素,负Eu异常明显(δEu=0.84～1.32),相对富集Sc、Hf,相对贫化Sr、Zr、Th、U。构造环境判别图解显示,马玉花岗闪长岩形成于碰撞期后板内构造环境,说明哀牢山构造带的古特提斯支洋或弧后盆地在晚二叠世(263.6±2.4Ma)已经闭合。     

铜陵狮子山地区胡村岩体年代学及地球化学特征

铜陵地区燕山期岩浆热液活动与大规模成矿作用有密切联系。本文开展了锆石年代学和地球化学的研究,以探讨胡村花岗闪长岩体与铜矿床之间的成因联系。结果显示花岗闪长岩体锆石U-Pb年龄为139.6±2.2Ma;主量元素含量为:SiO260.00%~65.26%,Al2O3 15.2%~17.15%,全碱(K2O+Na2O)6.94%~7.85%,落入高钾钙碱性系列;微量元素结果表明,大离子亲石元素相对相邻元素富集,亏损高场强元素;轻重稀土元素分馏明显,轻稀土元素富集,具轻微Eu负异常。这些结果说明胡村花岗闪长岩体的岩石地球化学特征、形成时代、构造环境等都与狮子山矿田内具有代表性的岩体相似,认为花岗闪长岩成岩物质主要来自上地幔,同时还有地壳物质的混入,具有壳幔混合特征。     

华北板块北缘中段早中二叠世的构造属性：来自花岗岩类锆石U-Pb年代学及地球化学的制约

内蒙古温都尔庙南-铁沙盖黑云角闪石英闪长岩和角闪黑云花岗闪长岩位于华北板块北缘中段晚古生代构造岩浆活动带中;锆石LA-ICP-MS U-Pb定年结果显示,其形成时代分别为271.8±2.4Ma,271.4±1.3Ma、268.7±1.3Ma。主量元素SiO₂含量61.42%~71.73%,K₂O含量3.10%~5.11%,K₂O/Na₂O值介于0.93~1.96之间,Mg^#值介于42.54~49.93之间,A/CNK为0.90~1.03;副矿物为锆石、磷灰石和磁铁矿,属亚碱性高钾钙碱性系列、I型花岗岩类;富集轻稀土(LREEs)、大离子亲石元素(LILEs,Cs、Rb、K、Ba、Th和U),亏损重稀土元素(HREEs)及高场强元素(HFSEs,Nb、Ta和Ti),弱Eu负异常(δEu=0.55~0.95),形成于活动大陆边缘弧环境,是上地壳部分熔融的产物。黑云角闪石英闪长岩和角闪黑云花岗闪长岩中发育大量暗色微粒包体(黑云闪长岩),包体可能是岩石圈地幔部分熔融的产物,相对于寄主岩石贫Si、K富Fe、Mg、Ca、Ti、大离子亲石元素(LILEs,Rb、Cs、Sr和U)和高场强元素(HFSEs,Nb、Ta、Zr、Hf)。本文花岗岩类的侵位反映了早中二叠世古亚洲洋俯冲于华北板块北缘之下及岩浆混合作用的岩浆事件。     

东天山石炭纪—二叠纪花岗质侵入岩的地球化学及地质意义

东天山吐哈盆地南缘至喀拉塔格—星星峡地块,晚古生代花岗质侵入岩岩石类型主要有花岗闪长岩、二长花岗岩、石英闪长岩、石英二长闪长岩。岩石地球化学特征表明：Si O2质量分数为57.3%~77.76%,全碱（K2O＋Na2O）质量分数为4.14%~10.49%,Ca O质量分数为0.49%~6.56%,Al2O3质量分数为11.39%~14.76%,铝饱和指数（A/CNK）为0.77~1.04,属于高钾钙碱性系列—钾玄质系列的准铝质花岗岩。稀土总量较高且轻稀土富集,富集Rb、Th、U、K、Pb,而亏损Nb、Ta、Ti、P,无明显负Eu异常。区域构造背景、岩石学和地球化学特征综合分析显示,东天山石炭纪—二叠纪花岗质侵入岩,是后碰撞构造演化阶段岩浆活动的产物,主要由幔源岩浆底侵引起的地壳物质部分熔融所形成的钙碱性花岗闪长质岩浆经高度演化及分异结晶作用而成。     

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.