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1.
浙江临海猫狸岭岩体的成因：年代学、地球化学与Sr-Nd-Hf同位素制约 总被引：2，自引：0，他引：2
猫狸岭岩体位于浙江省临海县仙人桥-猫狸岭一带,其主体岩性为石英二长闪长岩、石英二长岩和细粒花岗岩。LA-ICP-MS 锆石U-Pb定年表明石英二长闪长岩和细粒花岗岩的年龄分别为105.6±1.0Ma和104.8±0.9Ma。主量元素组成上,石英二长闪长岩具准铝质、钙碱性和富钾的特征,MgO、Fe2O3T、CaO等含量较高,Mg#值变化于47.6~50.6;细粒花岗岩同样具富钾和准铝质特征,但偏酸性,MgO、Fe2O3T、CaO等含量相对偏低,Mg#值变化于41.6~47.0。微量和稀土元素组成上,石英二长闪长岩富集Rb、Th、U、Pb,贫Nb、Ta、P、Ti,且Zr、Hf、Sr含量相对较高,铕负异常不显著（Eu/Eu*=0.77~0.95）。细粒花岗岩具有相似的微量元素特征,但P、Ti亏损程度更明显,且明显贫Sr,并具一定程度的铕负异常（Eu/Eu*=0.55~0.78）。石英二长闪长岩和细粒花岗岩具有相似的Sr-Nd同位素组成,ISr分别为0.7088和0.7079~0.7088,εNd（t）值分别为-7.57~-7.56和-8.06~-7.95。同时,二者具有大致相似的锆石Hf同位素组成,εHf（t）值分别为-12.2~-6.6和-9.6~-4.4。综合分析表明,猫狸岭石英二长闪长岩和细粒花岗岩最可能是在区域伸展拉张的构造背景下,由底侵或内侵的幔源岩浆与其诱发的壳源岩浆经混合后,并经过不同程度的分异演化,最后在浅成环境侵位的产物。 相似文献
2.
东昆仑野马泉铁矿相关花岗质岩体年代学、地球化学及Hf同位素特征 总被引：13，自引：4，他引：9
野马泉大型铁多金属矿床位于东昆仑造山带祁漫塔格地区,矿区发育大量与铁多金属成矿关系密切的花岗质岩体。LA-ICP-MS锆石U-Pb定年表明北矿带隐伏二长花岗岩、花岗闪长岩年龄分别为393±2Ma、386±1Ma;南矿带斑状石英二长闪长岩、正长花岗岩年龄为219±1Ma、213±1Ma,分别为早-中泥盆世和晚三叠世岩浆活动的产物。早-中泥盆世花岗闪长岩与二长花岗岩均为高钾钙碱性,A/CNK值（0.92~1.01）<1.1,具中等强度的负Eu异常（δEu为0.60~0.81）,明显亏损P、Nb、Ta、Ti、Sr、Ba等,富集LREE、Rb、Th、U、K等,显示了I型花岗岩的特征。晚三叠世斑状石英二长闪长岩含有少量角闪石,A/CNK值（0.88~0.95）<1,轻稀土富集,具中等负Eu异常（δEu为0.49~0.67）,富集Rb、U、Th、K等大离子亲石元素,亏损P、Nb、Ta、Ti、Sr、Ba等,具有I型花岗岩的特征;正长花岗岩高硅（SiO2=77.20%~78.13%）、富碱（K2O+Na2O=7.91%~8.27%）、贫铝（Al2O3=11.71%~12.18%）、贫钙（CaO=0.90%~1.01%）,富集LREE、Y、Zr、Hf、Th、U、Ga等,强烈亏损Ba、Sr、P、Ti、Eu,具强烈的负Eu异常（δEu为0.08~0.13）,显示弱过铝质A型花岗岩的特征。锆石Hf同位素组成表明,早-中二叠世岩体的εHf（t）为-3.3~6.2,晚三叠世岩体的εHf（t）为-6.3~5.5,显示在成岩过程中有地幔组分的参与。综合研究认为,野马泉矿区早-中泥盆世、晚三叠世岩体分别形成于早古生代构造-岩浆旋回的碰撞-后碰撞阶段和晚古生代-早中生代构造-岩浆旋回的碰撞-后碰撞阶段,可能是由地幔底侵古老陆壳,幔源基性岩浆与壳源花岗质岩浆发生不同程度混合作用而生成,壳幔物质交换为区内大规模铁铜铅锌多金属矿化提供大量成矿物质。 相似文献
3.
提要：分布于湖南衡山的南岳岩体,侵位于新元古代冷家溪群中,为复式岩体。通过锆石U-Pb年龄测定,其锆石LA-ICP-MS U-Pb年龄为（215.5±1.5）Ma,主体形成于晚三叠世;其中部分小岩体形成于早白垩世,锆石LA-ICP-MS U-Pb年龄为（140.6±0.8）Ma。晚三叠世花岗岩由三个岩石单元组成,第一期细中粒斑状角闪石黑云母二长花岗岩、第二期中细粒黑云母二长花岗岩、第三期二云母二长花岗岩;早白垩世花岗岩为二云母二长花岗岩。晚三叠世花岗岩属过铝质高钾钙碱性系列;早白垩世花岗岩属强过铝质高钾钙碱性系列。岩石明显富集大离子亲石元素,亏损高场强元素;∑REE中等（92.88×10-6~296.56×10-6）,Eu均为弱负异常(δEu=0.28~0.87),其中早白垩世花岗岩Eu亏损更大;ISr值较大（0.7093~0.7189）;低εNd（-8.04~-11.38）, 高T2DM（1.63 ~1.90 Ga）。综合研究表明,南岳花岗岩石为壳源含白云母过铝花岗岩类（MPG）,为华南前寒武系基底重熔而成,晚三叠世花岗岩有少量下地壳或地幔物质加入;其形成的构造背景应为碰撞造山作用晚期或结束时期,是陆内碰撞造山作用增温减压体制下的产物。 相似文献
4.
西藏波密花岗岩体的年代学、地球化学特征及其意义 总被引：1，自引：1，他引：0
波密岩体位于西藏东南部,处于班公湖-怒江蛇绿混杂岩带与印度河-雅鲁藏布蛇绿混杂岩带之间,整体呈NW向延伸,面积约29km2。本文对波密花岗岩体进行了系统的岩石学、地球化学及同位素年代学研究。结果显示,波密岩体主要以黑云母石英闪长岩与黑云母花岗闪长岩为主,两个花岗闪长岩的LA-ICP-MS锆石U-Pb年龄分别为113.1±2.3Ma和113.4±2.1Ma。花岗岩类SiO2介于64.11%~66.63%,K2O+Na2O=6.36%~7.54%,全碱含量较高,属于高钾钙碱系列。稀土元素含量为114.9×10-6~182.8×10-6,分配曲线均呈右倾趋势。另外,A/CNK为0.80~0.95,波密岩体有高K,高Si,低P的特点,大离子亲石元素(Rb、K)富集,高场强元素(Nb、Ta、P、Ti)亏损,属于偏铝质I型花岗岩。2件样品37个测点的锆石εHf(t)值不均一,几乎全为负值(-13.72~-0.08),反映岩浆可能源于古老地壳;地壳模式年龄(tDMC)集中于891~2047Ma之间。综合分析波密岩体地球化学及锆石年龄数据,均与中冈底斯及弧背断隆带中早白垩世的岩体特征相似。因此本文推断波密岩体的成因为中冈底斯早白垩世带状岩浆大爆发事件在东部的延续。 相似文献
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云南格咱岛弧普朗斑岩型铜矿年代学、岩石矿物学及地球化学研究 总被引：11，自引：5，他引：6
普朗斑岩型铜矿床位于西南三江构造火成岩带义敦岛弧南端,是晚三叠世甘孜-理塘洋壳向德格-中甸陆块俯冲的产物,是我国近年来印支期新发现的超大型铜多金属矿床。与成矿关系密切的斑岩体的岩石类型主要为石英闪长玢岩和石英二长斑岩,通过系统的锆石U-Pb测年方法获得,含矿石英闪长玢岩的形成年龄为219.6±3.5Ma,石英二长斑岩的形成年龄为212.8±1.9Ma。岩石地球化学特征表明,SiO2含量为61.99%~70.58%,Al2O3含量为10.84%~14.96%,MgO含量为1.5%~3.96%,A/CNK值为0.80~1.08,为准铝质-弱过铝质。岩石轻稀土较富集,轻重稀土分馏明显((La/Yb)N=11.41~16.48),δEu(0.76~0.9)值无明显异常。微量元素表现出具较高的Sr(244×10-6~845×10-6)、Ba(543×10-6~2237×10-6)含量,Y、Yb含量较低(Y=6.83×10-6~17.65×10-6,Yb=0.97×10-6~1.09×10-6)指示岩石类型为造山带钙碱性花岗岩系列,具I型花岗岩的特点。利用黑云母和角闪石地质温压计估算出岩浆的结晶温度为750~800℃,岩体侵位的压力为0.77×108~0.9×108 Pa,相应的岩体侵位深度在2.55~2.97km,氧逸度为10-9~10-12bar,反映了成矿斑岩体形成于高温、高氧逸度的环境,岩浆侵位具浅成-超浅成侵位的特点。结合本区岩石地球化学、矿物学及同位素年代学的研究,推测普朗成矿斑岩体深部仍存在类似的斑岩型Cu(Au)矿化,具有良好的找矿前景。 相似文献
6.
南天山拜城县波孜果尔A型花岗岩类锆石U-Pb定年及其Lu-Hf同位素组成 总被引：3，自引：2，他引：1
新疆拜城县波孜果尔A型花岗岩类岩体位于塔里木地台北缘及邻区的近东西向碱性侵入岩带上,主要岩石类型为霓石钠闪石英碱长正长岩、霓石钠闪碱长花岗岩、黑云母碱长正长岩。全岩SiO2=68.97%~74.14%,Na2O+K2O=9.67%~11.19%,Al2O3=13.72%~15.26%,Fe2O3=0.18%~1.41%,FeO=0.91%~1.51%,CaO=0.35%~0.63%。稀土元素总量较高,ΣREE=298×10-6~1286×10-6,平均706×10-6,轻稀土富集,重稀土亏损,强烈的Eu负异常,呈“右倾海鸥型”的稀土元素配分模式。富Nb、Ta、Zr、Hf等高场强元素,亏损Ba、K、Sr等大离子亲石元素,Zr+Nb+Ce+Y=936×10-6~3684×10-6,平均1813×10-6。为A1型花岗岩。岩体形成于早二叠纪。锆石LA-ICP-MS U-Pb年龄为287.7~291.6Ma,平均289.8Ma,岩体形成后,在279.1~282Ma左右经历了后期热液流体的改造。锆石εHf（t）值为-6.3~9.0,两阶段模式年龄（tDM2）跨越古元古代晚期-新元古代中期,主要集中在中元古代。岩浆平均温度832~839℃,形成于非造山的板内构造环境,且具高温、无水、低氧逸度的成岩特点。该岩体具有壳幔混源的特点。 相似文献
7.
福建紫金山矿田浸铜湖矿床石英正长斑岩锆石U-Pb年代学及其岩石地球化学特征 总被引：3，自引：1，他引：2
浸铜湖斑岩铜（钼）矿床位于福建紫金山矿田的北东侧,本文分析了出露于该矿床的石英正长斑岩的主量元素、稀土和微量元素组成,Nd同位素组成,并对其进行锆石LA-ICP-MS U-Pb定年。研究结果显示,岩石SiO2含量变化于57.59%~71.19%,岩石全碱含量为7.73%~10.01%,里特曼指数σ为 2.21~6.05,铝饱和指数A/CNK为1.24~1.53,为过铝质、高钾钙碱性系列。稀土元素总量为152×10-6~212×10-6,具有弱Eu负异常（Eu/Eu*=0.71~0.97）,（La/Yb）N为16.62~33.49,表现出轻稀土富集,重稀土亏损。微量元素具有亏损Nb、Ta、P、Ti等高场强元素,富集大离子亲石元素的特点,显示弧岩浆作用特点。岩石具有低的εNd（t）值和低的Nd模式年龄,分别为-6.60~-4.37和1.25~1.43Ga,显示壳-幔相互作用特征。对石英正长斑岩两个样品的锆石进行激光探针等离子体质谱（LA-ICP-MS）U-Pb微区测定,结果分别为95.3±0.9Ma和96.7±0.9Ma,为晚白垩世早期岩浆活动产物。结合已有的研究成果,本文认为石英正长斑岩形成于拉张的构造背景之下,由受到俯冲组分改造或影响的岩石圈地幔物质与中、下地壳物质部分熔融形成的花岗质岩浆混合形成。 相似文献
8.
广东园珠顶铜钼矿床花岗斑岩年代学、地球化学特征及锆石Hf同位素 总被引：3，自引：0，他引：3
园珠顶铜钼矿床位于钦杭成矿带南段的大瑶山隆起北缘,为大型斑岩型铜钼矿床。通过LA-ICP-MS锆石U-Pb同位素测年,获得了花岗斑岩的高精度成岩年龄,为（154.3±1.7） Ma （n=12,MSWD=3.1）,为晚侏罗世岩浆活动的产物,与辉钼矿的Re-Os同位素年龄155 Ma相吻合。岩石地球化学分析表明,园珠顶花岗斑岩高硅〔w（SiO2）为68.81%~70.21%〕、富碱〔w（Na2O）+w（K2O）为6.78%~8.01%〕、准铝质-弱过铝质（A/CNK为0.96~1.04）;稀土元素总量中等（ΣREE 为142.15×10-6~170.83×10-6）,富集轻稀土元素（ΣLREE 为135.05×10-6~162.34×10-6）,轻重稀土元素分馏明显〔（La/Yb）N=30.97~32.10〕,弱的Eu负异常（δEu=0.86~0.89）,稀土元素配分模式总体右倾;岩石相对富集Rb、K等大离子亲石元素（LILE）及高场强元素Th、U,亏损Nb、Ta、P、Ti等高场强元素（HFSE）及部分大离子亲石元素Ba、Sr。LA-MC-ICP-MS锆石Hf 的原位分析表明,176Hf/177Hf值变化于0.282 500~0.282 801之间,εHf（t）值介于-6.27~4.19。综合分析表明,园珠顶花岗斑岩为准铝质-弱过铝质的I型花岗岩,具有壳幔混合源成因,锆石εHf（t）值反映了园珠顶花岗斑岩的成岩源区较为复杂,总体具亏损岩浆源区的特征,以幔源物质为主,但在岩浆侵位过程中遭受了古老地壳物质的混染。结合区域构造背景和前人研究成果,认为园珠顶斑岩体及铜钼矿,与钦杭成矿带北段的永平铜矿具有一致的成岩成矿构造背景,形成于板块俯冲环境。 相似文献
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东昆仑香日德地区晚三叠世花岗岩LA-ICP-MS锆石U-Pb定年、岩石成因和构造意义 总被引：10，自引：6，他引：4
东昆仑地区广泛分布了大量花岗岩.已有的研究工作表明,东昆仑地区的花岗岩主要形成于晚二叠世-中三叠世和晚三叠世两个时期.本文提供了香日德地区二长花岗岩和花岗闪长岩的锆石U-Pb定年数据和全岩化学,稀土微量元素及Sr、Nd同位素地球化学研究资料,结合前人对该区不同时期花岗岩的研究成果,对香日德晚三叠世花岗岩的成因及其形成的动力学背景进行了讨论.研究表明东昆仑东段香日德地区的二长花岗岩和花岗闪长岩分别形成于223.2±1.7Ma和220.6±1.5Ma,属晚三叠世花岗岩浆作用的产物.根据该花岗岩的主量元素(特别是A/CNK比值),岩石富集大离子亲石元素(LILE:Rb、Th和K)和轻稀土(LREE),明显亏损高场强元素(HFSE:Nb、Ta、Ti和P),以及岩石具有相对高的Isr值(0.70820~0.71148)和相对低的εNd(t)值为-6.4~-3.6和较古老的模式年龄t2DM(1.5~1.7Ga)等地球化学特征,论证了该花岗岩的成因,指出香日德花岗闪长岩-二长花岗岩的起源和成因与碰撞后的背景下岩石圈的拆沉诱发的古老地壳物质的部分熔融作用有关,晚三叠世花岗岩岩浆作用是对自晚海西期以来幔源玄武质岩浆长期的底侵作用及地壳不断加厚的一种响应.它进一步证明在东昆仑地区,阿尼玛卿古特提斯洋的俯冲作用一直持续到早三叠纪,至晚三叠世才全面转入陆内碰撞造山阶段.晚三叠世花岗岩与晚二叠世-中三叠世花岗岩在暗色包体含量、岩浆混合作用的特征等方面的差异,可以用幔源物质贡献量的差异以及花岗质岩浆作用所经历的MASH过程的不同来解释. 相似文献
10.
福建漳州角美花岗岩与闪长质包体的岩石成因及意义 总被引：3，自引：2，他引：1
本文选择福建沿海漳州地区的角美花岗岩和包体进行了锆石U-Pb年代学和Hf同位素地球化学研究。结果表明,黑云母花岗闪长岩(106.4±1.8Ma)和岩体中的闪长质包体(105.6±1.0Ma 和106.5±1.0Ma)具有相同的锆石U-Pb年龄,为同期岩浆作用的产物,它们都是高钾钙碱性系列偏铝质岩石。花岗闪长岩具有相对较为均一的锆石Hf同位素组成(εHf(t)=2.2~3.7),表明其为新生地壳部分熔融的产物。闪长质包体具有更亏损的锆石Hf组成(εHf(t)=0.9~5.5)。地球化学数据结合野外证据表明岩体形成过程中经历了岩浆混合作用。福建沿海地区96~106Ma岩浆作用的发育处于古太平洋板片俯冲造成的伸展背景。 相似文献
11.
Most sulfide-rich magmatic Ni-Cu-(PGE) deposits form in dynamic magmatic systems by partial melting S-bearing wall rocks with variable degrees of assimilation of miscible silicate and volatile components, and generation of barren to weakly-mineralized immiscible Fe sulfide xenomelts into which Ni-Cu-Co-PGE partition from the magma. Some exceptionally-thick magmatic Cr deposits may form by partial melting oxide-bearing wall rocks with variable degrees of assimilation of the miscible silicate and volatile components, and generation of barren Fe ± Ti oxide xenocrysts into which Cr-Mg-V ± Ti partition from the magma. The products of these processes are variably preserved as skarns, residues, xenoliths, xenocrysts, xenomelts, and xenovolatiles, which play important to critical roles in ore genesis, transport, localization, and/or modification. Incorporation of barren xenoliths/autoliths may induce small amounts of sulfide/chromite to segregate, but incorporation of sulfide xenomelts or oxide xenocrysts with dynamic upgrading of metal tenors (PGE > Cu > Ni > Co and Cr > V > Ti, respectively) is required to make significant ore deposits. Silicate xenomelts are only rarely preserved, but will be variably depleted in chalcophile and ferrous metals. Less dense felsic xenoliths may aid upward sulfide transport by increasing the effective viscosity and decreasing the bulk density of the magma. Denser mafic or metamorphosed xenoliths may also increase the effective viscosity of the magma, but may aid downward sulfide transport by increasing the bulk density of the magma. Sulfide wets olivine, so olivine xenocrysts may act as filter beds to collect advected finely dispersed sulfide droplets, but other silicates and xenoliths may not be wetted by sulfides. Xenovolatiles may retard settling of – or in some cases float – dense sulfide droplets. Reactions of sulfide melts with felsic country rocks may generate Fe-rich skarns that may allow sulfide melts to fractionate to more extreme Cu-Ni-rich compositions. Xenoliths, xenocrysts, xenomelts, and xenovolatiles are more likely to be preserved in cooler basaltic magmas than in hotter komatiitic magmas, and are more likely to be preserved in less dynamic (less turbulent) systems/domain/phases than in more dynamic (more turbulent) systems/domains/phases. Massive to semi-massive Ni-Cu-PGE and Cr mineralization and xenoliths are often localized within footwall embayments, dilations/jogs in dikes, throats of magma conduits, and the horizontal segments of dike-chonolith and dike-sill complexes, which represent fluid dynamic traps for both ascending and descending sulfides/oxides. If skarns, residues, xenoliths, xenocrysts, xenomelts, and/or xenovolatiles are present, they provide important constraints on ore genesis and they are valuable exploration indicators, but they must be included in elemental and isotopic mass balance calculations. 相似文献
12.
Between 1985 and 1991, two new mountain protected areas (MTNPA) covering more than 35,000 km2 and based on participatory management models — the Makalu-Barun National Park and Conservation Area, Nepal, and Qomolangma Nature Preserve, Tibet Autonomous Region — were successfully established through the collaborative efforts of Woodlands Mountain Institute and conservationists in China and Nepal. Characteristics common to both projects include the importance of establishing (1) effective rationales, (2) local support constituencies, (3) a senior advisory group, (4) a task force, (5) linkages between conservation and development, and (6) fund raising mechanisms. The lessons derived from the experiences of Woodlands Mountain Institute are of significant value to others in preserving MTNPA. Increased collaboration and communication between all interested in conservation, however, will remain a critical component for expanding mountain protected area coverage to throughout the world. 相似文献
13.
《Geoforum》2017
This article advances critical geographies of youth through examining the spatiality implicit in the imagined futures of young women in rural India. Geographers and other scholars of youth have begun to pay more attention to the interplay between young people’s past, present, and imagined futures. Within this emerging body of scholarship the role of the family and peer group in influencing young people’s orientations toward the future remain underexamined. Drawing on eleven months of ethnographic fieldwork, my research focuses on a first generation of college-going young women from socioeconomically marginalized backgrounds in India’s westernmost state of Gujarat. I draw on the “possible selves” theoretical construct in order to deploy a flexible conceptual framework that links imagined post-educational trajectories with motivation to act in the present. In tracing the physical movement of these young women as they navigate and complete college, my analysis highlights the ways in which particular kinds of spaces and spatial arrangements facilitate and limit intra- and inter-generational contact, and the extent to which this affects young women’s conceptions of the future. I conclude by considering the wider implications of my research for ongoing debates surrounding youth transitions, relational geographies of age, and education in the Global South. 相似文献
14.
15.
《Chemical Geology》2007,236(1-2):13-26
We examined the coprecipitation behavior of Ti, Mo, Sn and Sb in Ca–Al–Mg fluorides under two different fluoride forming conditions: at < 70 °C in an ultrasonic bath (denoted as the ultrasonic method) and at 245 °C using a Teflon bomb (denoted as the bomb method). In the ultrasonic method, small amounts of Ti, Mo and Sn coprecipitation were observed with 100% Ca and 100% Mg fluorides. No coprecipitation of Ti, Mo, Sn and Sb in Ca–Al–Mg fluorides occurred when the sample was decomposed by the bomb method except for 100% Ca fluoride. Based on our coprecipitation observations, we have developed a simultaneous determination method for B, Ti, Zr, Nb, Mo, Sn, Sb, Hf and Ta by Q-pole type ICP-MS (ICP-QMS) and sector field type ICP-MS (ICP-SFMS). 9–50 mg of samples with Zr–Mo–Sn–Sb–Hf spikes were decomposed by HF using the bomb method and the ultrasonic method with B spike. The sample was then evaporated and re-dissolved into 0.5 mol l− 1 HF, followed by the removal of fluorides by centrifuging. B, Zr, Mo, Sn, Sb and Hf were measured by ID method. Nb and Ta were measured by the ID-internal standardization method, based on Nb/Mo and Ta/Mo ratios using ICP-QMS, for which pseudo-FI was developed and applied. When 100% recovery yields of Zr and Hf are expected, Nb/Zr and Ta/Hf ratios may also be used. Ti was determined by the ID-internal standardization method, based on the Ti/Nb ratio from ICP-SFMS. Only 0.053 ml sample solution was required for measurement of all 9 elements. Dilution factors of ≤ 340 were aspirated without matrix effects. To demonstrate the applicability of our method, 4 carbonaceous chondrites (Ivuna, Orgueil, Cold Bokkeveld and Allende) as well as GSJ and USGS silicate reference materials of basalts, andesites and peridotites were analyzed. Our analytical results are consistent with previous studies, and the mean reproducibility of each element is 1.0–4.6% for basalts and andesites, and 6.7–11% for peridotites except for TiO2. 相似文献
16.
I. Bejarano-Ramirez Jose M. Jurado R. Muñiz-Valencia Á. Alcázar Silvia G. Ceballos-Magaña A. Olivos-Ortiz O. Rangel 《International Journal of Environmental Science and Technology》2017,14(6):1333-1342
The contents of As, Cd, Cu, Cr, Mg, Mn, Ni, Pb and Zn have been determined in sediment and water samples from Valle de las Garzas estuary and Port Manzanillo (Colima, Mexico) using ICP-AES. The concentrations of these elements were used for a comparative study to determine the distribution of heavy metals and to evaluate which elements reflect natural or anthropogenic backgrounds. For this purpose, seven sampling points were selected: Four of them correspond to the lagoon, and three were situated in the port. Statistical analysis of the mineral content was assessed. Initially, data comparison was assessed by statistical tests for each variable. Principal component analysis was then applied considering the influence of all variables at the same time by obtaining the distribution of samples according to their scores in the principal component space. In this way, four studies were carried out: (1) study of sediments collected during the dry season; (2) study of sediments collected during the rainy season; (3) comparative study between sediments from rainy and dry season; and (4) study of water composition collected during rainy season. From the results of the performed analyses, it can be concluded that metals distribution pattern reflected natural and anthropogenic backgrounds (e.g., sediments from the lagoon, situated at the beginning of the rain channel, presented high contents of Zn and Cu, perhaps related to anthropogenic activities or the influence of igneous sediments). 相似文献
17.
Models have become so fashionable that many scientists and engineers cannot imagine working without them. The predominant use of computer codes to execute model calculations has blurred the distinction between code and model. The recent controversy regarding model validation has brought into question what we mean by a ‘model’ and by ‘validation.’ It has become apparent that the usual meaning of validation may be common in engineering practice and seems useful in legal practice but it is contrary to scientific practice and brings into question our understanding of science and how it can best be applied to such problems as hazardous waste characterization, remediation, and aqueous geochemistry in general. This review summarizes arguments against using the phrase model validation and examines efforts to validate models for high-level radioactive waste management and for permitting and monitoring open-pit mines. Part of the controversy comes from a misunderstanding of ‘prediction’ and the need to distinguish logical from temporal prediction. Another problem stems from the difference in the engineering approach contrasted with the scientific approach. The reductionist influence on the way we approach environmental investigations also limits our ability to model the interconnected nature of reality. Guidelines are proposed to improve our perceptions and proper utilization of models. Use of the word ‘validation’ is strongly discouraged when discussing model reliability. 相似文献
18.
The shape of sedimentary particles may carry important information on their history. Current approaches to shape classification
(e.g. the Zingg or the Sneed and Folk system) rely on shape indices derived from the measurement of the three principal axes
of the approximating tri-axial ellipsoid. While these systems have undoubtedly proved to be useful tools, their application
inevitably requires tedious and ambiguous measurements, also classification involves the introduction of arbitrarily chosen
constants. Here we propose an alternative classification system based on the (integer) number of static equilibria. The latter
are points of the surface where the pebble is at rest on a horizontal, frictionless support. As opposed to the Zingg system,
our method relies on counting rather than measuring. We show that equilibria typically exist on two well-separated (micro
and macro) scales. Equilibria can be readily counted by simple hand experiments, i.e. the new classification scheme is practically
applicable. Based on statistical results from two different locations we demonstrate that pebbles are well mixed with respect
to the new classes, i.e. the new classification is reliable and stable in that sense. We also show that the Zingg statistics
can be extracted from the new statistics; however, substantial additional information is also available. From the practical
point of view, E-classification is substantially faster than the Zingg method. 相似文献
19.
Hirokazu Fujimaki 《Contributions to Mineralogy and Petrology》1986,94(1):42-45
Concentration ratios of Hf, Zr, and REE between zircon, apatite, and liquid were determined for three igneous compositions: two andesites and a diorite. The concentration ratios of these elements between zircon and corresponding liquid can approximate the partition coefficient. Although the concentration ratios between apatite and andesite groundmass can be considered as partition coefficients, those for the apatite in the diorite may deviate from the partition coefficients. The HREE partition coefficients between zircon and liquid are very large (100 for Er to 500 for Lu), and the Hf partition coefficient is even larger. The REE partition coefficients between apatite and liquid are convex upward, and large (D=10–100), whereas the Hf and Zr partition coefficients are less than 1. The large differences between partition coefficients of Lu and Hf for zircon-liquid and for apatite-liquid are confirmed. These partition coefficients are useful for petrogenetic models involving zircon and apatite. 相似文献
20.
Pools,riffles, and channelization 总被引：2，自引：0，他引：2
Edward A. Keller 《Environmental Geology》1978,2(2):119-127
The addition of regularly spaced deeps (pools) and shallows (riffles) that provide a variety of flow conditions, areal sorting
of stream-bed material, cover for wildlife, and a positive aesthetic experience, may be desirable in many channel projects.
Such designs will reduce adverse environmental impacts of stream channel modifications.
Analysis of variance for pool-to-pool spacing data suggests that there is no significant difference with respect to channel
width between pools that form in natural streams and those in streams affected by a variety of human uses. Short of channelization,
which changes the channel width, pools and riffles, within limits, are not particularly sensitive to environmental stress.
Experiments in Gum Branch near Charlotte, North Carolina, support the hypothesis that channel form and process evolve in harmony
and that manipulation of cross-channel morphology can influence the development of desired channel processes. Planned manipulation
of its channel form induced Gum Branch to develop as desired. Morphologic stability consisting of incipient point bars, pools,
and riffles was maintained over a period of high magnitude flood events, only to be degraded later by a wave of sediment derived
from upstream construction and stream-bank failures. Thus, environmentally desirable channel morphology in urban streams cannot
remain stable if changes in the sediment load or storm-water runoff exceed the limits of the stream's ability to make internal
adjustments while maintaining morphologic stability. 相似文献