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1.
邹家山矿床位于赣杭构造火山岩铀成矿带与大王山-于山花岗岩型铀成矿带的复合叠加部位。矿体产于下白垩统鹅湖岭组上段碎斑熔岩和打鼓顶组上段流纹英安岩中，呈脉状、细脉状，主要受NE向邹家山-石洞断裂带控制。围岩蚀变主要为萤石化、伊利石化、黄铁矿化、绿泥石化、碳酸盐化等。文章通过野外地质调查、地球化学分析、电子探针分析及矿物自动定量分析等方法，对该矿床超常富集铀矿石中Ti的赋存特征展开研究，结果表明，超常富集铀矿石中w（TiO2）和w（U）特征与前人研究的w（TiO2）和w（U）呈非线性正相关的结果不同。超常富集铀矿石中平均w（TiO2）仅是围岩的1.90倍，而平均w（U）却是围岩的565倍，TiO2与U相比富集程度并不高。元素相关性研究发现超常富集铀矿石中w（TiO2）与w（U）呈中度负相关，与易形成络阴离子的F、S、P2O5含量关系不明显，而w（U）与F、S、P2O5含量呈正相关，说明成矿环境中U与Ti物理化学性质差别较大，物质来源可能不同。超常富集铀矿石中Ti主要赋存于钛铀矿中。钛铀矿呈自形-半自形，大小约1~75 μm，大量分布于白云石、铁白云石等边缘。钛铀矿既包裹着早期的沥青铀矿，又被晚期的沥青铀矿包裹。经研究分析认为，铀矿石中Ti主要来源于赋矿围岩中的黑云母蚀变，胶体TiO2矿物对U的强吸附性有利于钛铀矿的形成，并促使U在地球化学障处超常富集。但铀成矿后期，热液中Ti几乎耗尽，钛铀矿不再新增，伴随成矿环境的改变，部分钛铀矿缓慢溶蚀以及被新形成的沥青铀矿交代，引起Ti流失，导致超常富集铀矿石中w（U）与w（TiO2）为中度负相关。 相似文献
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羊场磷矿是近年来在云南评价确认的沉积大型磷矿床,磷矿体赋存于下寒武统梅树村组碳酸盐岩-泥质碎屑岩沉积中部的一套含磷岩系中,呈层状、似层状展布于羊场背斜两翼,其产状与地层产状基本一致,含矿岩性为含磷白云岩、磷质岩、磷块岩、硅质岩建造。通过分析该矿床矿体特征和梅树村组磷块岩的主微量元素组成,研究了羊场磷矿的地球化学特征及其沉积环境。结果表明,羊场磷矿磷块岩具有富钙（w（CaO）=42.07%~45.01%）、磷（w（P2O5）=27.66%~39.25%）和贫硅（w（SiO2）=8.27%~15.40%）的特征;w（P2O5）与w（CaO）呈较好的正相关关系,与w（MgO）呈负相关关系,与w（Al2O3）呈较明显的负相关关系。矿石的w（Th）/w（U）值小于1、Pb （亲硫元素）和Sr富集（Pb平均富集系数16.66,Sr平均富集系数1.17）特征表明,羊场磷矿可能是热水沉积成矿与生物成矿双重作用的结果;微量元素特征值反映,羊场磷矿形成于深海到浅海的变化环境,为海相沉积型磷块岩,沉积时水体呈还原环境。 相似文献
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镁铝麻粒岩泛指一类全岩化学成分富镁、铝的麻粒岩相变质岩,是研究超高温变质作用的峰期变质条件和变质演化历史的重要对象,但目前对它的原岩属性和岩石成因的认识仍十分有限。本文以柴达木地块西缘的花土沟超高温变质地体为例,在野外调查基础上,对镁铝麻粒岩和泥质片麻岩进行了岩相学和全岩地球化学分析,发现镁铝麻粒岩与含浅色体的泥质片麻岩的SiO2、TiO2、P2O5 含量相似,TFe2O3、Al2O3、MnO、CaO、Na2O含量虽有差异但变化范围存在交集。此外,两类岩石具有相似的微量和稀土元素配分曲线,结合两者的矿物组合也存在相似性,提出花土沟镁铝麻粒岩的原岩可能是与泥质片麻岩类似的泥质沉积岩。从低角闪岩相变泥质岩到含浅色体的泥质片麻岩,再到镁铝麻粒岩,其全岩化学成分向着贫铝、钙、钾、钠,富铁、镁的趋势变化。其中,高XMg值（0.51~0.69）是镁铝麻粒岩与其他泥质片麻岩（XMg=0.34~0.43）的最大差别。通过对变泥质岩的相平衡模拟和理论计算,发现部分熔融和熔体丢失能解释大部分的变化趋势,但基本不影响全岩XMg值;只有在进变质升温过程中丢失含石榴子石的熔体才能造成变泥质岩的镁铝麻粒岩化。此外,富石榴子石的泥质残留体相比附近的含浅色体泥质片麻岩,贫硅、钠、钾,富集铝、铁、镁、锰、钙,重稀土元素含量显著高于后者,上述地球化学特征对应石榴子石熔体的加入而后长英质熔体的丢失,支持野外观察到的熔体携带石榴子石迁移的现象。最后,对镁铝麻粒岩只呈透镜体产出的原因做出了推测,即熔体很难带着石榴子石完成长距离迁移,只有被长英质正片麻岩包围的泥质沉积物,其进变质加热阶段形成的熔体才能携带石榴子石完全迁出原岩,促成变泥质岩透镜体的镁铝麻粒岩化,目前仍需更多的相关研究来验证这一推测。在世界其他高温-超高温变质岩区,石榴子石熔体的迁出和泥质岩的镁铝麻粒岩化可能也不同程度有所保留和记录。 相似文献
4.
辽西义县盆地早白垩世义县组陆相湖盆沉积中常发育多个薄层碳酸盐岩沉积层,碳酸盐岩地球化学的研究对揭示湖盆沉积古环境具有重要理论意义。义县组砖城子层英窝山剖面湖相碳酸盐岩分析结果显示,岩石δ13C值为-3.44×10-3~0.27×10-3,均值为-1.21×10-3;δ18O值为-15.73×10-3~-9.93×10-3,均值为-10.88×10-3。盐度Z值变化范围114.78~122.39。碳酸盐岩主量元素分析表明,w（CaO+MgO+LOI）=53.38%~97.04%,均值71.15%;陆源组分w（Al2O3+SiO2+Fe2O3）=2.19%~44.87%,均值为27.77%;x（Mg）/x（Ca）摩尔比介于0.92~1.01。碳酸盐岩微量元素地球化学提供了古湖泊学的古盐度、氧化还原和古气候证据。w（Sr）=110.4×10-6~1360.2×10-6,w（Ga）=0.152×10-6~14.13×10-6,w（Sr）/w（Ba）=0.34~131.49（多数>1）,指示沉积湖泊水体为咸水环境;氧化-还原指标w（V）/w（V+Ni）＝0.51~0.83,w（V）/w（Cr）＝1.59~8.28（多数>2.0）,w（U）/w（Th）=0.39~10.24,且变化范围较大,指示为半封闭—封闭的缺氧还原强分层水体沉积环境;w（Sr）/w（Cu）=54.94~1260.71,均值为213.79,反映炎热干旱气候类型。义县组砖城子层沉积期湖泊为干旱古气候背景下的半咸水—咸水、缺氧还原强分层的半封闭—封闭型。 相似文献
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藏南特提斯喜马拉雅东部的错那洞淡色花岗岩产出有白云母、石榴子石、电气石等特征性矿物,显示具有高度分异岩浆岩的特征。从二云母花岗岩到电气石花岗岩到石榴子石花岗岩,碱性长石均为正长石,斜长石从更长石演变为钠长石,白云母Al2O3、Na2O含量逐渐升高,反映花岗岩逐渐向富Al富Na演化的趋势。二云母花岗岩中黑云母XFe值、AlⅥ逐渐升高,表明二云母花岗岩之间存在结晶分异演化。电气石Xvac值、Al、Mg和Fe含量之间的变化,反映电气石花岗岩到花岗伟晶岩岩浆结晶环境中Na含量的增加,表明花岗伟晶岩结晶分异演化程度高于电气石花岗岩。石榴子石高XFe、XMn值的特征,也是高分异花岗岩的标志。上述矿物学研究结果表明,错那洞二云母花岗岩是由岩浆早期结晶矿物与残余的母岩浆组成的糊状物经过长期结晶形成的,而电气石花岗岩和石榴子石花岗岩由从晶粥体中分离出来的衍生熔体形成。 相似文献
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通过对出露在康古尔韧性剪切带西段的色尔特能超镁铁岩的野外地质调查和岩石学、岩石地球化学方面的分析研究工作,结果显示：色尔特能超镁铁岩发生了强烈蛇纹石化,基本蚀变成蛇纹岩;岩石主量元素具高Mg （w（MgO）=36.15%~37.96%）、高Cr （w（Cr2O3）=0.32%~0.36%）、高Ni （w（NiO）=0.17%~0.21%）、低Si （w（SiO2）=40.50%~41.92%）、贫Al （w（Al2O3）=1.19%~1.77%）、低Fe （w（TFeO）=6.98%~7.87%）特征,Mg#值为94.71~97.73,m/f值为8.03~9.42,属于典型镁质超镁铁岩,推测原岩为斜方辉石橄榄岩;稀土元素总量w（ΣREE）=1.44×10-6~2.92×10-6,配分模式为轻稀土微弱富集近平坦型,w（La）N/w（Yb）N=3.09~5.49,具一定程度的负Eu异常（δEu=0.48~1.09）和负Ce异常（δCe=0.53~0.60）;微量元素富集Ba、U、Ta,亏损Nb、Ti。色尔特能超镁铁岩属变质橄榄岩,是SSZ型蛇绿岩的底部组成单元,由原始地幔经2%~10%部分熔融形成的亏损地幔岩,其形成于俯冲带环境中的洋内弧后盆地。 相似文献
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辽南42号金伯利岩岩管主要由东部42-1号大岩管、西部42-2号小岩管和中部42-3号小小岩管组成。42-1号岩管从地表到40 m标高形态急剧收缩;42-2号岩管为烟筒状,40 m标高至-160 m标高面积比为1∶1.15;42-3岩管在-200 m标高处延深为脉状。42号岩管岩石类型为斑状金伯利岩、斑状富金云母金伯利岩、含或富含围岩角砾金伯利岩和含岩球斑状金伯利岩。岩石化学特征研究表明,岩石中w(SiO2)、w(Al2O3)、w(TiO2)值比山东胜利Ⅰ号金伯利岩和戴里值偏高,w(MgO)、w(Cr2O3)、w(K2O)、w(Na2O)、w(P2O5)值较戴里值偏低,但w(K2O)、w(Na2O)、w(P2O5)值比山东胜利Ⅰ号金伯利岩略高;w(ΣFe2O3+FeO)、w(CaO+H2O)值与山东胜利Ⅰ号金伯利岩及戴里值相当。通过采样分析42-2号岩管金刚石含量高,42-1号岩管金刚石含量低;研究认为受造岩矿物橄榄石和金云母的影响,金刚石含量与橄榄石斑晶含量正相关,与金云母含量呈负相关;伴生矿物铬铁矿、镁铝榴石、碳硅石含量高,则金刚石含量也随之增高,为正相关;而锐钛矿于金刚石含量为负相关。基于研究区的三维建模、推覆构造研究,推测42号岩管不是根部相,其东部可能存在深部金伯利岩体。 相似文献
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栖霞牙山花岗岩体形成于中生代早白垩世（118 Ma）,其岩石类型以花岗岩和花岗闪长岩为主,岩体中发育大量的暗色闪长质微粒包体。通过对牙山花岗岩及其暗色包体地球化学特征研究表明,包体围岩w（SiO2）=65.5%~68.82%,铝饱和度（A/CNK）为0.89~1.03<1.1,为准铝质钙碱性Ⅰ型花岗岩;暗色包体具有较低w（SiO2）值（54.82%~60.89%）、高w（TFe2O3）值（6.11%~8.15%）、高w（MgO）值（3.57%~5.19%）的特征。稀土元素配分模式图显示二者皆为轻稀土富集的右倾型曲线,微量元素蛛网图中二者均表现为富集Ba、K等大离子亲石元素,亏损Ta、Nb、Ti等高场强元素,具有大陆地壳的特征。暗色包体与寄主岩石的Sr同位素初始比值（87Sr/86Sr）i分别为0.709 29~0.709 58和0.709 21~0.709 71,应为同源岩浆的产物。两阶段Nd模式年龄（T2DM）分为2 291 Ma-2 391 Ma和2 208 Ma-2 353 Ma,表明可能是古元古界陆壳物质部分熔融的产物。Pb同位素特征显示牙山岩体的原始岩浆以下地壳为主,w（Nb）/w（Ta）值介于下地壳与原始地幔之间,表明可能受到幔源物质的影响,包体中大量磷灰石呈针状结晶状态,进一步暗示存在岩浆混合作用。综上并结合区域构造背景认为,牙山岩体为早白垩世中晚期起源于火山弧环境的壳源特征花岗岩,形成过程中存在幔源物质的加入,它的形成与太平洋板块的俯冲作用密切相关。 相似文献
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营厂岩体分布于辽北西丰县和隆镇境内，研究结果表明，该岩体主要为似斑状二长花岗岩，锆石206Pb/238U年龄加权平均值为156.1 Ma±1.5 Ma，形成时代为晚侏罗世。营厂岩体w（Na2O）/w（K2O）平均值为1.07，属高钾钙碱性系列；里特曼指数σ平均值为2.15，属钙碱系列；铝饱和指数A/CNK平均值为1.16，A/CN平均值为1.99，属过铝型；Rb、Sr、Ba、Th、Hf含量偏高，Cr、Ni、Co、V、Rb、Zr、Nb等元素含量低，为"S"型花岗岩特征。稀土元素总量平均值为w（ΣREE）＝82.80×10-6，w（LREE）/w（HREE）=15.76，w（La）N/w（Yb）N=24.32，表明其轻稀土相对富集，重稀土相对亏损，稀土配分曲线右倾。δEu=0.80，铕弱负异常，说明成因与板块运动有关，w（Sm）/w（Nd）=0.20，w（Ba）/w（Sr）=1.60，w（K）/w（Rb）=249.15，表明具有壳源性质。营厂岩体具有埃达克岩的特点，其属于受太平洋板块向欧亚板块俯冲作用的影响，在挤压环境下加厚下地壳部分熔融，从而形成活动陆缘型花岗岩。 相似文献
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虎头崖Pb-Zn多金属矿床位于东昆仑西段祁漫塔格岩浆弧带，矿体主要赋存于三叠纪花岗闪长岩和二长花岗岩与围岩的接触带及围岩中，并伴生有Fe、Cu等元素，属典型矽卡岩型矿床。对矽卡岩阶段石榴子石和透辉石、退化蚀变阶段绿帘石、石英硫化物阶段方解石、石英、萤石中流体包裹体的详细岩相学研究结果表明，与成矿有关的流体包裹体类型主要有富液相包裹体、富气相包裹体和含子矿物三相包裹体。激光拉曼光谱分析结果显示，气相、液相成分以H2O为主，含少量HCO3-；固相成分以NaCl为主，并有少量的闪锌矿（ZnS）、磁黄铁矿（Fe1-xS）和硬石膏（CaSO4），成矿流体应为H2O-NaCl体系。包裹体显微测温结果显示，矽卡岩、退化蚀变、石英硫化物阶段均一温度分别为（430~490℃、550~580℃）、340~370℃和190~340℃，盐度w（NaCleq）分别为39%~48%、9%~12%、（0.18%~4%、15%~24%）。H-O同位素研究表明，成矿流体主要为岩浆热液，在成矿晚期则有不同程度的大气降水混入。在石英硫化物阶段，含子矿物包裹体和气相分数变化较大的气液包裹体共生，它们均一温度相近但盐度差别较大，表明成矿流体曾发生过广泛的不混溶（沸腾）作用，而这一过程很可能导致流体中Pb、Zn、Fe、Cu等矿质沉淀富集。 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.
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
17.
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
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