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Yu Chongwen 《中国地质大学学报(英文版)》1995,(1)
Dissolution Precipitation Wave Structure ofHydrothermal Ore Zoning¥YuChongwen(FacultyofEarthSciences,ChinaUniversityofGeoscie... 相似文献
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Maria Fernanda Gazulla Antonio Barba María Pilar Gómez Monica Orduña 《Geostandards and Geoanalytical Research》2006,30(3):237-243
The present study was undertaken to establish and validate a methodology for determining the chemical composition of chromite ores, as no detailed information could be found in the literature. Chromite ores from South Africa, Kazajistan and Mongolia were analysed. X-ray fluorescence (XRF) spectrometry was used for chemical characterisation. Sample preparation in the form of fused beads was optimised in terms of sample:flux ratio, type of flux, type of release agent, fusion temperature and time. Calibration and validation samples were prepared from mixtures of reference materials. The proposed methodology was then used in an interlaboratory test for preparing a new chromite-rich reference material.
L'analyse présentée id a été entreprise afin d'établir et de valider une méthodologie pour déterminer la composition chimique de minerals de chromite, car aucune information détaillée là dessus ne pouvait etre trouvée dans la littérature. Des minerals de chromite d'Afrique du Sud, du Kazakhstan et de Mongolie ont été analysés par spectrométrie de Fluorescence de Rayons X (XRF) afin d'être caractérisés chimiquement. La préparation des échantillons afin d'obtenir des perles fondues a été optimisée en termes du rapport "échantillon/fondant", type de fondant, d'agent mouillant, température et durée de fusion. La calibration et la validation ont été faites à partir de mixtures de matériau de référence. La méthodologie proposée a été ensuite appliquée à un test d'inter-comparaison en vue de préparer un nouveau matériau de référence riche en chromite . 相似文献
L'analyse présentée id a été entreprise afin d'établir et de valider une méthodologie pour déterminer la composition chimique de minerals de chromite, car aucune information détaillée là dessus ne pouvait etre trouvée dans la littérature. Des minerals de chromite d'Afrique du Sud, du Kazakhstan et de Mongolie ont été analysés par spectrométrie de Fluorescence de Rayons X (XRF) afin d'être caractérisés chimiquement. La préparation des échantillons afin d'obtenir des perles fondues a été optimisée en termes du rapport "échantillon/fondant", type de fondant, d'agent mouillant, température et durée de fusion. La calibration et la validation ont été faites à partir de mixtures de matériau de référence. La méthodologie proposée a été ensuite appliquée à un test d'inter-comparaison en vue de préparer un nouveau matériau de référence riche en chromite . 相似文献
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为探讨内蒙古贺根山蛇绿岩形成时的物化条件和大地构造环境,选取崇根山蛇绿岩块中未蚀变副矿物铬铁矿进行矿物学和矿物地球化学分析。结果表明:铬铁矿成分均一,不发育环带结构;铬铁矿中的Cr2O3质量分数为38.86%~39.12%,Al2O3质量分数为26.56%~26.92%,TFeO质量分数为17.37%~17.50%,Cr#为49.34~49.58,Mg#为68.82~69.73,Yfe为6.62~6.97,Fe2+#为30.27~31.18,为富镁铝铬铁矿,其寄主岩石为蛇绿岩;铬铁矿结晶平均温度为1 396.88℃,平均压力为3.35 GPa,推断其形成深度约为103.72 km;相对于FMQ(fayalite magnetite quartz)缓冲剂的地幔氧逸度为FMQ+1.41~FMQ+1.45 lg单位(平均值为FMQ+1.43 lg单位);地幔熔融程度为20.93%~20.95%(平均值为20.94%)。推测崇根山铬铁矿原岩橄榄岩单元源区为石榴石二辉橄榄岩,形成于亏损地幔。崇根山蛇绿岩为消减带型蛇绿岩,可能产自俯冲带环境中的洋内弧后盆地环境。 相似文献
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Major minerals (sulfates, sulfides, quartz) are distributed in different parts of submarine hydrothermal ore deposits. For instance, the abundance of barite increases stratigraphically upwards in the massive orebodies of the Kuroko deposits (black and yellow ores), while quartz is abundant in the lower parts (siliceous ore). The different distribution of barite and quartz in the Kuroko deposits can not be accounted for by thermochemical equilibrium calculations based on the precipitation due to mixing of ascending hydrothermal solutions with ambient cold seawater. In the present study, a coupled fluid flow‐precipitation kinetics model was used to calculate the amounts of quartz, barite, and anhydrite precipitated from a hydrothermal solution mixed with seawater, assuming reasonable values for temperature, precipitation rate, fluid flow velocity, mineral surface area/fluid mass ratio (A/M), and initial concentrations of hydrothermal solution and seawater before mixing occurred. The results indicate that barite precipitates more efficiently than quartz from discharging fluids with relatively higher flow velocity, lower temperatures and under the condition of lower A/M ratios on the seafloor (black ore), whereas quartz precipitates more effectively from solutions with lower flow velocity, higher temperatures and higher A/M ratios beneath the seafloor (siliceous ore) and in the orebody (barite ore, ferruginous chert ore). Anhydrite precipitates in shallow sub‐seafloor environments with lower precipitation rates and higher A/M ratios than barite and higher precipitation rates and lower A/M ratios than quartz. These results explain the observed occurrences of barite, anhydrite, and quartz in the Kuroko deposits. Namely, barite is abundant in black ore and barite ore which formed above the seafloor, anhydrite formed in high‐permeability tuff breccias, and quartz formed in low permeability dacite intrusive bodies in the sub‐seafloor environment. 相似文献
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库地蛇绿岩属于西昆仑早古生代蛇绿岩带,主要由变质橄榄岩、堆晶橄榄岩、基性火山岩和石英岩等组成.库地蛇绿岩体具有较好的岩相分带,其中纯橄岩相与辉橄岩相中产出豆荚状铬铁矿.与其他岩相对比,铬铁矿具有最高的Cr2O3含量、最大的Mg#值和最小的Fe#值,表明铬铁矿形成于富Mg的环境,且经历了更高程度的部分熔融.利用铬铁矿(铬尖晶石)矿物的化学成分,得出铬尖晶石的结晶温度为1366~1404℃,平均1379℃;压力为2.98~3.03GPa,平均3.00GPa;地幔部分熔融程度F为17.33%~18.84%,平均18.28%.结合已有的研究成果,推测库地蛇绿岩的基底橄榄岩单元源区为石榴石二辉橄榄岩,形成于亏损的软流圈地幔,对应的大地构造位置为消减带之上岛弧环境. 相似文献
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正The Kuda ophiolite belongs to the early Paleozoic ophiolite belt in Western Kunlun Mountains and is composed of metamorphic peridotites,cumulate peridotites,mafic volcanic rocks and quartzites(Li et al., 相似文献
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As well as world class Fe and REE resources the Bayan Obo mineral deposits also hosts significant niobium resources(estimated as 2.2 Mt Nb with an average grade of 0.13 wt% Nb).Niobium in this study is primarily hosted in aeschynite-(Ce) and(Nd),but with subsidiary amounts of pyrochlore,fergusonite-(Ce),fersmite and columbite.Here we report on the paragenetic and textural setting of aeschynite,pyrochlore and fergusonite in the main ore bodies and in a carbonatite dyke.Niobium in a carbonatite sample is hosted in a phase tentatively(due to significant Ca,Mn and Ti contents) identified as fergusonite-(Ce).Aeschynite occurs overgrowing foliation in banded ores,in fractures and vugs in aegirine-rich rocks and in calcite veins.The composition in all settings is similar,but some examples in banded ores develop significant zonation in Y,Th and the REE,inferred to relate to buffering of halogen acid species to low levels by dissolution and fluoritisation of calcite,and the preferential precipitation of LREE from solution due to lower mineral solubility products compared to the HREE.Although lower in total concentration the ratios of REE in pyrochlore are similar to those of aeschynite and suggest the same metal source.The crystallisation of pyrochlore probably relates to growth in paragenetic settings where carbonates had already been eliminated and hence the buffering of F-species activities in the hydrothermal fluid was reduced.Both aeschynite and pyrochlore show evidence of alteration.Primary alteration of aeschynite resulted in leaching of A-site cations(Ca,REE,Th) and Nb,addition of Fe,and ultimately replacement by Ba-Ti phases(baotite and bafertisite).Secondary,metamictisation enhanced,possibly supergene alteration of pyrochlore resulted in hydration,leaching of A-site cations leading to the development of lattice vacancies and increases in Si.The presence of hydrothermal Nb resources at Bayan Obo suggests there may be potential for further Nb discoveries in the area,whilst the trends in element mobility during alteration have significant implications for the utility of A-B oxides as components of materials for immobilisation of radionuclides. 相似文献
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在三层结构热液硫化物矿体模型的基础上, 分别构建了具有不同地形环境的海底热液硫化物矿体模型, 利用数值模拟方法, 模拟了具有倾斜海底面和起伏地形特征的硫化物矿体模型内部温度场和流场分布, 并据此探讨了地形环境在大型海底热液硫化物矿体形成过程中的控制作用.模拟结果表明: (1) 倾斜的洋壳层顶面对于矿体内温度场和流场分布的影响程度有限; (2) 矿体地形起伏是控制矿体内流体运移和热场分布的重要因素; (3) 在热液流体喷出区附近硫化物的堆积速度较快, 易于形成矿体的高地形区; 但随着地形的不断升高, 矿体内部的温度场和流场的分布模式会逐渐发生改变, 导致该区域热液喷口逐渐消亡或者改道. 相似文献
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《International Geology Review》2012,54(3):224-231
The process of hydrothermally concentrating trace metals into ores is endothermic. The necessary energy is supplied as heat either directly from the mantle or by igneous bodies. For epithermal ores, heat from intrusives causes advective circulation of hydrothermal fluids, which leach ore components from various source rocks. If minerals that precipitate from the circulating fluid are to reach ore concentrations, then the plutonic heat source must provide energy at a rate sufficient for adequate mass transport, roughly 1014 kJ/a, and must continue for about 106 a. To power a continuing hydrothermal circulation cell to form an ore deposit, such plutons should be intruded within an area less than about 50 km in diameter and with a frequency at least as often as every 25 ka. The rarity of mineral districts results principally from the enormous heat requirements of the processes that generate major mineralization. Consequently, in mineral exploration, an initial objective ideally is to find evidence of extraordinarily persistent heat and fluid flow. 相似文献
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GUO Guolin YANG Jingsui PAUL T. Robinson XIONG Fahui XU Xiangzhen LIU Xiaodong LIJinyang LIU Zhao 《《地质学报》英文版》2015,89(Z2):16-17
<正>1 Introduction Platinum-group elements(PGE)are mainly concentrated in some specific minerals known as PGMs,which commonly occur in podiform chromites of ophiolites.In-situ PGM assemblages in chromites can provide valuable information on the physico-chemical nature of the parental melt(s)from which chromitite 相似文献
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Well ordered tridymites containing atmost 0.016% Na (0.004% Na) were prepared at 1400° C from Na2WO4-(K2WO4-) fluxes using high purity amorphous silica as starting material. No further reduction of these Na-contents was attainable by soxhlet extraction. These tridymites were treated hydrothermally at temperatures between 815 and 950° C and 200 bars H2O. The products obtained were investigated optically as well as by powder X-ray methods and were analyzed for Na-contents: the hydrothermal treatment resulted either in recrystallization of tridymite or transformation into quartz mostly depending on Na-contents. Na-contents below about 0.015% tend to favour recrystallization of tridymite within the quartz field (<870° C), Na-contents above about 0.03% tend to favour formation of quartz within the tridymite field (>870° C). This may be due to influences of Na-traces either on the kinetics or on the equilibrium temperature of tridymite-quartz transformation. 相似文献
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Magmatic augites reacted with high temperature aqueous solutions to form secondary calcic pyroxenes during the subsolidus cooling of the Skaergaard intrusion. Secondary, hydrothermal clinopyroxenes replace wall rock igneous augites at the margins of veins filled with calcic amphibole. These veins are up to several millimeters wide and tens of meters in length. Hydrothermal clinopyroxenes are a ubiquitous and characteristic phase in the earliest veins throughout the Layered Series of the intrusion, and occur rarely in late veins that, in some places, crosscut the early veins. Associated secondary phases in early veins include amphiboles ranging in composition from actinolite to hornblende, together with biotite, Fe-Ti oxides and calcic plagioclase. Hydrothermal clinopyroxenes in late veins may be associated with actinolite, hornblende, biotite, magnetite and albite.Hydrothermal clinopyroxenes are depleted in Fe, Mg and minor elements, and enriched in Ca and Si relative to igneous augites in the Layered Series gabbros. Secondary vein pyroxenes are similar in composition to calcic pyroxenes from amphibolite facies metamorphic rocks. Clinopyroxene solvus thermometry suggests minimum temperatures of equilibration of between 500° and 750° C. These temperatures, combined with numerical transport models of the intrusion, suggest that vein clinopyroxenes could have formed during 20,000 to 60,000 year time intervals associated with a maximum in the fluid flux through fractures in the Layered Series. 相似文献
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Taking the Jinchang gold-copper field in Yinan County, Shandong Province, China, as an example, the authors have proposed that the migration and concentration of ore-forming substances carried in the hydrothermal solutions might be mainly controlled by the structural deformation taking place during the mineralization epoch. It has been found that the ore-forming elements are generally concentrated in the places with strong structural deformation and that different types of ore bodies occur in different parts of deformational structures, In addition, the authors have conducted a quantitative evaluation of the structural control over the emplacement of ores through petromechanical experiments, measurement of physico-mechanical parameters of the rocks, inversion of the stress field and simulation of distribution of migration potential of the ore-forming solutions with the theory of infiltration mechanics. 相似文献
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位于华北克拉通中部太行山北段的浮图峪矿田由七个中小型矽卡岩型铜铁矿床和木吉村大型斑岩铜(钼)矿组成。石榴子石是浮图峪矿田矽卡岩型矿床的主要矿物,与矿化关系密切,是展开浮图峪矿田成因研究的一个重要切入点。本文对其中四个典型矽卡岩型矿床中与矿化密切相关的石榴子石进行野外地质调研、岩相学特征研究,运用电子探针分析石榴子石环带的化学成分。研究结果表明,石榴子石成分属钙铁-钙铝榴石系列;从晶体核部到边缘,钙铁榴石与钙铝榴石呈韵律式变化,总体上钙铁榴石组分的质量分数(78.1%~86.2%)大于钙铝榴石(12.91%~16.61%)。根据石榴子石的环带结构及其成分特征,认为石榴子石是在弱酸、较低温度和相对氧化的环境中生成的,指示成岩成矿流体温度、pH、氧逸度和盐度均在不断地发生变化,说明石榴子石不是在一个完全封闭的平衡条件形成的,暗示流体的多期多阶段性,这是矽卡岩型矿床富集金属的前提条件和重要因素。 相似文献