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1.
西藏墨竹工卡地区甲玛铜多金属矿床矽卡岩矿物学特征及其地质意义 总被引：4，自引：0，他引：4
为研究西藏甲玛铜多金属矿床中矽卡岩的矿物学特征,进一步确定矿床成因类型,利用电子探针测试和镜下鉴定手段对矽卡岩矿物中的石榴子石、辉石、硅灰石等矿物成分进行了分析。测试结果表明,矽卡岩中石榴子石以钙铁榴石-钙铝榴石为主,辉石以透辉石为主,甲玛矿床矽卡岩属于交代矽卡岩中典型的钙矽卡岩。结合前人对矿区矽卡岩、围岩和花岗岩类的岩石地球化学、矿床成矿年代学等的研究,进一步证实甲玛铜多金属矿床系矿区花岗岩类岩浆交代大理岩形成的典型矽卡岩型矿床。 相似文献
2.
万龙山锌锡矿床是都龙锡矿田的一个重要矿区。通过矽卡岩岩石化学研究,认为矿区矽卡岩属于钙矽卡岩,在w(SiO_2)—w(CaO)图解中,矿区矽卡岩与花岗岩、大理岩投点区呈线性展布,表明三者之间具有成因联系。对矿区主要的矽卡岩矿物石榴子石、辉石、角闪石、绿帘石和绿泥石进行了电子探针成分分析:石榴子石属于钙铝榴石-钙铁榴石系列,端元组分以钙铝榴石为主(体积分数51.02%～82.63%),钙铁榴石体积分数为12.45%～47.74%;辉石为透辉石-钙铁辉石系列,端元组分以钙铁辉石为主,明显缺乏透辉石;角闪石属于Mg-Fe-Mn-Li组,主要为镁角闪石;绿帘石中Fe的含量较;绿泥石主要为铁镁绿泥石,部分为铁斜绿泥石、密绿泥石或铁绿泥石,显示富镁铁质的特点。依据矽卡岩矿物的组分特征对矿区矽卡岩的成因、成矿条件及矿床成因等进行了讨论,认为矿区矽卡岩及金属矿化主要与晚白垩世老君山花岗岩具有成因关系,锡锌多金属矿床属于岩浆热液渗透交代型矿床。 相似文献
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滇西红牛矽卡岩型铜矿床石榴子石特征 总被引：13，自引：7，他引：6
红牛矽卡岩型铜矿床是义敦岛弧南段格咱火山-岩浆弧新探明的铜矿床之一,目前探明铜金属资源量已达大型规模。与由侵入岩和大理岩直接接触形成的典型矽卡岩矿床不同,红牛铜矿床是隐伏岩体远程矽卡岩化的产物,其矽卡岩矿体与地层产状基本一致,通常相间排列,且距离岩体较远,大理岩中可见粗粒石榴子石和硅灰石,矽卡岩中常见大理岩捕掳体。根据矽卡岩矿物组合可将该矿床矽卡岩类型划分为石榴子石矽卡岩、石榴子石透辉石(或透辉石石榴子石)矽卡岩、透辉石矽卡岩、符山石-石榴子石矽卡岩、硅灰石-石榴子石矽卡岩、绿帘石-石榴子石矽卡岩、阳起石-绿帘石矽卡岩、硅灰石矽卡岩和绿帘石矽卡岩,其中以石榴子石矽卡岩、透辉石矽卡岩和硅灰石矽卡岩为主。石榴子石是最重要的矽卡岩矿物,分布广泛、颜色变化大,且石榴子石矽卡岩中黄铜矿、黄铁矿、磁黄铁矿化最好。本文通过对0ZK10、3ZK11和7ZK16钻孔岩芯的地质编录,查明石榴子石在红牛铜矿床的空间分布和矿化特征,采集该矿区新鲜的石榴子石矽卡岩、矽卡岩化大理岩和角岩磨制成光薄片,开展详细的显微镜下鉴定工作,观察石榴子石的颜色、粒度、结构、光性等岩相学特征,并通过电子探针分析其化学成分。红牛铜矿床石榴子石集中产出于矽卡岩中,少量产出于矽卡岩化大理岩和角岩中,具有明显的两期。早期石榴子石分布广泛,多呈褐色-红褐色,非均质性,异常干涉色,粒径一般在0.2~4mm之间,半自形-自形中细粒结构,韵律环带发育。SiO2含量变化范围为35.18%~37.69%、CaO为33.34%~36.35%、Al2O3为3.64%~13.69%、FeO为11.90%~24.18%、MgO为0.00%~0.08%,FeO和Al2O3含量变化呈负相关,SiO2和CaO含量变化整体呈正相关。石榴子石端员组分总体以钙铁榴石(36.88%~82.36%)为主,其次为钙铝榴石(16.59%~60.75%),还有少量的镁铝榴石、铁铝榴石和锰铝榴石,属于钙铁榴石-钙铝榴石系列(And37-82Gro17-61Spe+Pyr+Alm0.33-3.71)。晚期石榴子石呈浅褐色-浅红色,多发育于矽卡岩化角岩和大理岩中,少量发育于矽卡岩中,半自形-他形粒状结构,均质性,全消光,常具有溶蚀结构。SiO2含量变化范围为35.06%~36.27%、CaO为33.07%~33.77%、Al2O3为0.04%~1.05%、FeO为27.38%~28.18%、MgO为0.00%~0.04%,属于钙铁榴石(94.42%~98.46%)。早期石榴子石韵律环带发育,其主量元素含量变化显示出一定的规律性,由核部向边缘,SiO2和CaO基本保持不变,FeO含量增加,Al2O3含量减少,钙铁榴石含量增加,钙铝榴石含量减少,反映在石榴子石形成早期,成岩环境为低氧逸度、酸性还原环境;形成过程中氧逸度增加,成矿溶液由酸性向弱碱性演化。黄铜矿、磁黄铁矿、辉钼矿等金属硫化物多呈他形充填于石榴子石颗粒之间,或在石榴子石的裂隙中形成细脉,或沿石榴子石生长环带面交代,表明石榴子石形成于矽卡岩早期、早于铜矿化,并为金属硫化物的沉淀富集提供了空间。 相似文献
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广东省天堂铜铅锌多金属矿床矽卡岩矿物学特征及其地质意义 总被引：2，自引：0，他引：2
天堂矿床是粤西地区以泥盆系上统天子岭组灰岩为围岩的大型矽卡岩型铜铅锌多金属矿床,矿体呈似层状、层状、透镜状、不规则状等产出在矽卡岩和矽卡岩化大理岩中,矿区发育石榴子石、透辉石、绿帘石、硅灰石、绿泥石等蚀变矿物,金属矿物主要包括黄铜矿、黄铁矿、方铅矿和闪锌矿等。本文以主要矽卡岩矿物为研究对象,利用电子探针技术对其矿物学特征进行研究。电子探针分析结果表明:天堂铜铅锌多金属矿床矽卡岩属于交代矽卡岩中典型的钙矽卡岩。石榴子石以钙铝榴石-钙铁榴石系列为主,从早到晚具有从钙铝榴石为主到钙铁榴石为主的演化趋势,说明成矿流体由酸性向碱性演化。辉石以透辉石为主,石榴子石和辉石的矿物组分分别为Adr4.60~96.47Grs2.10~94.28(Prp+Sps)0.41~3.88和Di88.51~95.09Hd3.31~9.76Jo0.28~3.98,其较大的成分变化特征反映出矽卡岩不是在一个完全封闭的平衡条件下形成的。帘石主要为绿帘石,含有少量的黝帘石。矿物成分分析表明辉石的Mn/Fe比值和矿化金属元素存在一定的联系。通过矽卡岩矿物学特征分析,进一步证实天堂铜铅锌多金属矿床是花岗岩类岩浆交代灰岩而形成的典型矽卡岩型矿床。 相似文献
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滇西北铜厂沟矽卡岩-斑岩型Mo-Cu矿床是扬子地块西缘新发现的大型钼铜矿床。矽卡岩在铜厂沟矿区广泛发育，是矿区最主要的赋矿岩石。笔者以铜厂沟矽卡岩中石榴子石(Grt)为研究对象，利用电子探针和LA-ICP-MS原位技术开展成分和年代学测试分析。根据矿物镜下特征，将矿区石榴子石分为早期(Grt Ⅰ)和晚期(Grt Ⅱ)两个世代。Grt Ⅰ为浅黄色-黄白色、无环带石榴子石，Grt Ⅱ为褐色-红褐色、具有明显环带的石榴子石。两期石榴子石的SiO2(34.41%～38.45%)、 CaO(32.7%～35.25%)、 Al2O3(6.64%～12.57%)和FeO(12.03%～22.63%)含量指示，二者均属于钙铁榴石-钙铝榴石系列(And34-64Gro34-58)。Grt Ⅰ和Grt Ⅱ均呈轻稀土和重稀土亏损、中稀土富集的“驼峰型”配分模式。相比于Grt Ⅰ,Grt Ⅱ具有更低的U含量和变化范围更大的Eu异常，分别指示晚期矽卡岩矿化流体氧逸度较高和pH变化较大。Grt Ⅱ中显著的... 相似文献
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丁家山铅锌矿床位于梅仙矿田东南部，矿区内普遍发育石榴子石、辉石、绿帘石等脉石矿物，为探讨该矿床成因，对该矿床脉石矿物进行了电子探针、激光剥蚀电感耦合等离子质谱仪(LA-ICP-MS)原位U-Pb定年和微量元素分析。结果表明，石榴子石主要为钙铁-钙铝榴石固溶体系列，含有少量的锰铝榴石和铁铝榴石；辉石为透辉石-钙铁辉石-钙锰辉石固溶体系列；绿帘石族矿物属于绿帘石范畴。石榴子石的206Pb/238U下交点年龄为143.7 Ma,与成矿花岗岩年龄接近。依据石榴子石原位微量元素特征差异及Eu异常将石榴子石分为钙铁榴石(I型)和钙铁-钙铝榴石(II型)两类。钙铁榴石整体呈现轻稀土富集，重稀土亏损的稀土配分模式，I-1型钙铁榴石Eu具有明显的负异常，I-2型钙铁榴石Eu具有明显的正异常；钙铁-钙铝榴石整体呈现重稀土富集，轻稀土亏损的稀土配分模式，II-1型钙铁-钙铝榴石Eu具有明显的负异常，II-2型钙铁-钙铝榴石Eu具有明显的正异常。上述特征表明，石榴子石核部环境为弱氧化-弱还原，边部为氧化环境。综合地质学、矿物学、地质年代学数据以及地球化学特征，本文认... 相似文献
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西藏知不拉铜多金属床是冈底斯成矿带东段典型的矽卡岩矿床,石榴子石是矿区最主要的矽卡岩矿物,其颗粒间的空隙是金属矿物的主要赋存部位。本文通过详细的钻孔编录,结合岩矿鉴定及电子探针分析,划分出两种不同类型的石榴子环带,并在垂向上具有明显的分带:产于顶板凝灰岩中的石榴子石以钙铁榴石为主,环带中心颜色深,向外逐渐变浅,由纯钙铁榴石过渡到钙铝榴石;而位于底板大理岩附近石榴子石多以钙铝榴石为主,从环带核部向外颜色变深,化学组成由钙铝榴石向钙铁榴石变化,其它化学成分变化不大。反映该区上下两套不同性质围岩在石榴子石形成过程中所起的作用不同,其中上部凝灰岩主要提供了Fe,底部大理岩则是Ca的来源,热液流体贡献Si、Al及部分Fe,并随着环境和物质成分改变导致环带外侧具有不同于核部的变化趋势。这很好地解释了石榴子石矽卡岩在空间上具有上部为钙铁榴石、向下逐渐过渡到钙铝榴石的空间分带。石榴子石特征及分带显示了其属热液接触交代成因,这为矿床类型的确定提供了依据,也为在该区域内寻找类似矿床指明了方向。 相似文献
8.
《矿物学报》2013,(3)
本文对荷花坪锡多金属矿,锡田锡钨多金属矿以及新田岭钨矿矽卡岩中的石榴子石样品分别进行了主量元素、微量元素及红外光谱测定。结果表明,3种矽卡岩中的石榴子石多数属于(铁铝榴石+镁铝榴石+锰铝榴石)<15%的钙铁-钙铝榴石系列。新田岭钨矿的石榴子石中钙铁榴石端员含量明显高于其他两个锡矿。此外,在荷花坪、新田岭矿区发现了与后期铅锌矿化有关的锰质石榴子石。在单矿物尺度上,荷花坪矿区石榴子石核部富集钙铝榴石,边部富集钙铁榴石,而锡田矿区石榴子石与之相反;新田岭矿区石榴子石具有相对均匀的核部而边部发育细密的振荡环带。在稀土配分模式上,荷花坪矿区石榴子石重稀土富集,轻稀土亏损,δEu负异常较弱;锡田矿区石榴子石稀土总量最高,轻重稀土无明显分异,δEu负异常较弱;新田岭矿区石榴子石轻重稀土分异极强,重稀土富集,轻稀土严重亏损,δEu具显著的正异常。3种石榴子石的红外漫反射光谱均显示有10种吸收峰,其中低频区的5种与石榴子石成分中的钙铁榴石含量直接相关,因而造成新田岭矿区石榴子石的吸收峰与另两矿区石榴子石相比显著向低频波段移动。通过对华南3类含钨锡矽卡岩中的石榴子石的研究,确认了石榴子石的形成与矽卡岩形成中热液体系的环境变化密切相关。微量元素分析与红外光谱技术作为近年来矽卡岩型石榴子石研究的热点,能够提供传统研究中所不能涉及的微观信息。 相似文献
9.
哈萨克斯坦萨亚克大型铜矿田中, 矽卡岩型矿床的矿体赋存于石炭系灰岩与花岗岩类的接触带上, 矿体及其周围发育大量矽卡岩。矽卡岩矿物主要由石榴子石、辉石、绿帘石、绿泥石等组成, 矿石矿物主要发育黄铜矿、斑铜矿、黄铁矿、磁黄铁矿、辉钴矿等。萨亚克矽卡岩型矿床成矿作用分为5个阶段: 透辉石-石榴子石矽卡岩阶段、石榴子石矽卡岩阶段、绿帘石-磁铁矿阶段、石英-硫化物阶段和碳酸盐阶段。电子探针分析结果表明, 矿区矽卡岩属典型的钙质矽卡岩。 其中石榴子石发育3种类型, 均属钙铝-钙铁榴石固溶体系列, 自早期透辉石-石榴子石矽卡岩阶段至晚期石榴子石矽卡岩阶段, 由钙铁榴石向钙铝-钙铁榴石转变, 并且钙铁-钙铝榴石与矿化关系最为密切。其中具环带结构的石榴子石中钙铁与钙铝含量随环带呈韵律性变化, 表明生长过程中成分具震荡性变化, 形成于不完全封闭的平衡条件, 指示流体的多期次多阶段性; 辉石以透辉石为主; 绿帘石属绿帘石族中绿帘石范畴; 磁铁矿TFeO含量高, 与其他氧化物成分呈负相关关系。石英硫化物阶段早期发育黄铜矿-黄铁矿-磁黄铁矿-白铁矿、黄铜矿-辉钴矿矿物组合; 晚期为主要矿化阶段, 发育大量致密块状黄铜矿。黄铜矿显示贫硫富铜、铁特征; 黄铁矿为亏硫型; 磁黄铁矿属贫钴富镍型。矽卡岩矿物共生组合及石榴子石成分演化等矿物学特征显示, 成矿过程中随着温度及氧逸度的降低, 成矿热液由弱碱性向酸性演化, 伴随热液在接触带的中和作用, 以黄铜矿为主的金属硫化物富集沉淀。 相似文献
10.
西藏浦桑果铅锌多金属矿床矽卡岩矿物学特征及其地质意义 总被引：1，自引：0，他引：1
西藏浦桑果铅锌多金属矿床位于南冈底斯成矿带火山岩浆弧内,矿区矽卡岩型铅锌矿体主要呈似层状和透镜状近东西向赋存于白垩系塔克那组第4岩性段矽卡岩化大理岩中,矽卡岩矿物较发育。为进一步查明矽卡岩矿物种属及矽卡岩类型,剖析矽卡岩的形成环境及其与成矿的关系,在对矽卡岩矿物系统的显微镜下鉴定基础上,利用电子探针对矿区内主要矽卡岩矿物化学成分进行了系统分析。结果表明,石榴子石主要为非连续的钙铁榴石钙铝榴石类质同像系列(And47.39~98.17Gro0.59~50.22Ura+Pyr+Spe0~3.53),且早期主要形成钙铁榴石,部分钙铁榴石含锰质较高;单斜辉石主要为钙铁辉石-锰钙辉石-透辉石类质同像系列(Hd37.91~74.16Jo0.91~61.66Di0.43~46.07);似辉石主要为硅灰石,端员组分为Wo99.09~99.26En0.50~0.56Fs0.13~0.24;角闪石主要为镁角闪石,具钙质角闪石属性;绿帘石贫铁、镁而富铝、钙;绿泥石属于密绿泥石类。矿床矽卡岩矿物组合特征表明,浦桑果矿床矽卡岩兼具钙质矽卡岩和锰质矽卡岩的特征。早期矽卡岩形成于高温、偏碱性、强氧化的开放体系中,成矿流体具有较高氧逸度。锰质矽卡岩矿物特征及独立银矿物的存在综合表明矿区具有银矿找矿潜力,为下步找矿工作提供了思路和方向。 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.
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