共查询到18条相似文献，搜索用时 187 毫秒
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采用半导体脉冲激光光源和时间分辨探测技术, 对Ab -An -Di相图同结线附近处于玄武岩成分区的2个硅酸盐样品进行了升温过程的Raman光谱研究.研究了该成分区域中玻璃-晶体-熔体高温下的相转变、升温过程及其熔体的特征光谱的变化特点.发现高温熔体结构与低温玻璃结构存在明显区别, 晶体对熔体结构有继承性.同时观察到了Ab12 An3 6Di52在熔态时的分相作用, 可能反映了该组分液态不混溶的发生.通过对高频区的解谱, 初步探索了体系中各结构单元的种类及含量与温度的关系. 相似文献
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硅酸盐熔体中的（ＳｉＯ４）四面体借助于共同氧连接形成结构基团，使产生这种基团的作用称为聚合作用，聚合作用程度的差异是硅酸盐熔体结构多样性的主要原因，聚合作用随温度降低而增强。熔体结构在局部与其相应的晶体结构很相似，但在整体上，不象晶体那样，其原子在三维空间内连续有规则的排列且只含一种结构简单，而是多种结构单元可以共同存在于同一熔体中，且其位置和排列方式随原子不规则的热运动而不断地改变，在一定的温度 相似文献
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阿尔泰伟晶岩中流体熔融包裹体成分的研究 总被引：9，自引：1，他引：9
对阿尔泰可可托海、柯鲁木特和库威伟晶岩锂辉石及绿柱石中单个流体熔融包裹体各相成分，借助激光拉曼探针进行分析，鉴定出固体相为不同硅酸盐子晶矿物，定量给出了流体相成分。根据子晶矿物和流体相成分估算了整个流体熔融包裹体的成分，并据此进一步讨论了熔体中流体的溶解度问题。流体熔融包裹体成分研究表明熔体中流体已达饱和或过饱和，流体相与熔体相发生分离，相应残余伟晶岩浆体系进入晶体＋熔体＋流体三相共存的岩浆－热液 相似文献
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硅酸盐熔体结构与岩浆液态不混溶作用 总被引：4，自引：0，他引：4
本文简述了硅酸盐熔体结构和岩浆液态不混溶作用的基本特征，计算了玄武岩中基质和液态不混溶共轭熔体对的ＮＢＯ／Ｔ值，发现三者具有不同的熔体结构，据此总结出硅酸盐熔体结构与岩浆液态不混溶作用之间的内在联系。同时利用硅酸盐熔体结构解释了组分对岩浆液态不溶混作用的影响。 相似文献
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吉伯特铁矿是新疆阿勒泰地区产于泥盆纪海相火山岩中的小型矿床。本文对吉伯特铁矿床的包裹体开展了研究,识别了熔体包裹体、熔体-流体包裹体以及富晶体的流体包裹体,并对其进行了初步的显微测温、激光拉曼光谱和电子探针等研究。熔体包裹体中含有富Si玻璃质、贫Si富Fe熔体、石英、萤石、方解石、磁铁矿等多种成分,它们分别组成不同的包裹体组合。熔体包裹体、熔体-流体包裹体和流体包裹体的存在表明它们被捕获时是一种熔体与流体共存的不混溶状态,这充分说明了吉伯特铁矿床的形成与岩浆熔体、岩浆-热液过渡性流体有直接的成因联系。吉伯特铁矿床中Fe的矿化是一个熔体相逐渐减少,流体相逐渐增加的连续演化过程,它受岩浆作用、岩浆-热液过渡性流体以及矽卡岩作用的共同制约。 相似文献
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李迪恩 《矿物岩石地球化学通报》1997,(2)
硅酸盐玻璃和熔体中硅和铝的配位与局部结构：Ｋ边Ｘ射线吸收光谱研究＊李迪恩（中山大学地质系，广州５１０２７５）关键词硅酸盐玻璃和熔体硅和铝的配位Ｘ射线吸光谱高压下硅酸盐矿物和玻璃中的硅可以形成八面体配位［１］，但在通常的低压硅酸盐玻璃中，硅和铝为四面体... 相似文献
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水在硅酸盐熔体中的溶解度及研究意义 总被引：2，自引：0，他引：2
水是岩浆中主要的挥发份 ,而且其溶解作用强烈影响着熔体的物理和化学性质 ,因此对水在硅酸盐熔体中溶解度及溶解机制的研究是非常重要的。近年来研究表明 ,水在硅酸盐熔体中溶解度与压力、温度及熔体组分密切相关。具体而言 ,压力升高可使水的溶解度增大 ,而温度对溶解度的影响则与熔体组成有关。对于AbOrQ体系 ,在压力低于 4 0 0MPa时 ,溶解度与温度呈反相关 ;而在压力高于 50 0MPa时 ,则呈现出正相关。但是 ,温度对溶解度的影响要明显弱于压力的影响。至于水的溶解度与熔体组分的关系 ,通过对碱金属组分的研究表明水的溶解度按K ,Na ,Li的次序而增加。此外 ,根据碱金属组分对水在硅酸盐熔体中溶解度的影响对水的溶解机制进行了论述 ,这与Sykes等通过分子轨道计算和拉曼、红外光谱研究得出的水在铝硅酸盐熔体中的溶解机理是一致的。 相似文献
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熔体阴离子结构团缔合过程中声子熵的研究何安明李秉新石焕文（西安地质学院，西安７１００５４）关键词熔体阴离子结构团缔合声子熵近年来，中外学者已经开始重视对岩浆熔体的物理过程和机制（如利用喇曼光谱直接测定硅酸盐熔浆的结构等）的研究工作，并取得了重要进展。... 相似文献
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以合成花岗岩、水、不同浓度的盐酸溶液、氢氟酸溶液作为反应初始物,在850℃,100 MPa,接近于NNO的条件下开展了金在不同花岗质熔体中溶解度的实验研究,实验固液相产物中的金含量使用石墨炉原子吸收法测定。实验结果显示,金在花岗质熔体中的溶解度变化范围为1.87～156.62μg/g,流体相中金的溶解度为0.31～6.92μg/g;金在熔体相中的溶解度较其在共存液相中的高。花岗质熔体相中金的溶解度明显受熔体化学组成的影响,过碱性富钠花岗质熔体中金的溶解度明显高些;金在花岗质熔体中的溶解度随着熔体中Na2O/K2O摩尔比增大而增大;在氟氯共存岩浆体系中,氟含量变化对金在熔体相中的溶解度影响不明显,而液相中氯含量增大有利于提高金在流体相中的含量。 相似文献
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Mathieu Roskosz Bjorn O. Mysen George D. Cody 《Geochimica et cosmochimica acta》2006,70(11):2902-2918
Solubility and speciation of nitrogen in silicate melts have been investigated between 1400 and 1700 °C and at pressures ranging from 10 to 30 kbar for six different binary alkali and alkaline-earth silicate liquids and a Ca-Mg-alumino silicate. Experiments were performed in a piston-cylinder apparatus. The nitrogen source is silver azide, which breaks down to Ag and molecular N2 below 300 °C. At high pressure and temperature, the nitrogen content may be as high as 0.7 wt% depending on the melt composition, pressure, and temperature. It increases with T, P and the polymerization state of the liquid. Characterization by Raman spectroscopy and 15N solid state MAS NMR indicates that nitrogen is not only physically dissolved as N2 within the melt structure like noble gases, but a fraction of nitrogen interacts strongly with the silicate network. The most likely nitrogen-bearing species that can account for Raman and NMR results is nitrosyl group. Solubility data follow an apparent Henry’s law behavior and are in good agreement with previous studies when the nitrosyl content is low. On the other hand, a significant departure from a Henry’s law behavior is observed for highly depolymerized melts, which contain more nitrosyl than polymerized melts. Possible solubility mechanisms are also discussed. Finally, a multi-variant empirical relation is given to predict the relative content of nitrosyl and molecular nitrogen as a function of P, T, and melt composition and structure. This complex speciation of nitrogen in melts under high pressure may have significant implication concerning crystal-melt partitioning of nitrogen as well as for potential elemental and isotopic fractionation of nitrogen in the deep Earth. 相似文献
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The speciation of water in silicate melts 总被引：1，自引：0，他引：1
Edward Stolper 《Geochimica et cosmochimica acta》1982,46(12):2609-2620
Previous models of water solubility in silicate melts generally assume essentially complete reaction of water molecules to hydroxyl groups. In this paper a new model is proposed that is based on the hypothesis that the observed concentrations of molecular water and hydroxyl groups in hydrous silicate glasses reflect those of the melts from which they were quenched. The new model relates the proportions of molecular water and hydroxyl groups in melts via the following reaction describing the homogeneous equilibrium between melt species: H2Omolecular (melt) + oxygen (melt) = 2OH (melt). An equilibrium constant has been formulated for this reaction and species are assumed to mix ideally. Given an equilibrium constant for this reaction of 0.1–0.3, the proposed model can account for variations in the concentrations of molecular water and hydroxyl groups in melts as functions of the total dissolved water content that are similar to those observed in glasses. The solubility of molecular water in melt is described by the following reaction: H2O (vapor) = H2Omolecular (melt).These reactions describing the homogeneous and heterogeneous equilibria of hydrous silicate melts can account for the following observations: the linearity between fH2O and the square of the mole fraction of dissolved water at low total water contents and deviations from linearity at high total water contents; the difference between the partial molar volume of water in melts at low total water contents and at high total water contents; the similarity between water contents of vapor-saturated melts of significantly different compositions at high pressures versus the dependence on melt composition of water solubility in silicate melts at low pressures; and the variations of viscosity, electrical conductivity, the diffusivity of “water,” the diffusivity of cesium, and phase relationships with the total dissolved water contents of melts.This model is thus consistent with available observations on hydrous melt systems and available data on the species concentrations of hydrous glasses and is easily tested, since measurements of the concentrations of molecular water and hydroxyl groups in silicate glasses quenched from melts equilibrated over a range of conditions and total dissolved water contents are readily obtainable. 相似文献
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Solubility mechanisms of water in depolymerized silicate melts quenched from high temperature (1000°-1300°C) at high pressure (0.8-2.0 GPa) have been examined in peralkaline melts in the system Na2O-SiO2-H2O with Raman and NMR spectroscopy. The Na/Si ratio of the melts ranged from 0.25 to 1. Water contents were varied from ∼3 mol% and ∼40 mol% (based on O = 1). Solution of water results in melt depolymerization where the rate of depolymerization with water content, ∂(NBO/Si)/∂XH2O, decreases with increasing total water content. At low water contents, the influence of H2O on the melt structure resembles that of adding alkali oxide. In water-rich melts, alkali oxides are more efficient melt depolymerizers than water. In highly polymerized melts, Si-OH bonds are formed by water reacting with bridging oxygen in Q4-species to form Q3 and Q2 species. In less polymerized melts, Si-OH bonds are formed when bridging oxygen in Q3-species react with water to form Q2-species. In addition, the presence of Na-OH complexes is inferred. Their importance appears to increase with Na/Si. This apparent increase in importance of Na-OH complexes with increasing Na/Si (which causes increasing degree of depolymerization of the anhydrous silicate melt) suggests that water is a less efficient depolymerizer of silicate melts, the more depolymerized the melt. This conclusion is consistent with recently published 1H and 29Si MAS NMR and 1H-29Si cross polarization NMR data. 相似文献
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Jindrich Kynicky Martin P.Smith Wenlei Song Anton R.Chakhmouradian Cheng Xu Antonin Kopriva Michaela Vasinova Galiova Martin Brtnicky 《地学前缘(英文版)》2019,10(2):527-537
The Lugiin Gol nepheline syenite intrusion, Mongolia, hosts a range of carbonatite dikes mineralized in rare-earth elements(REE). Both carbonatites and nepheline syenite-fluorite-calcite veinlets are host to a previously unreported macroscale texture involving pseudo-graphic intergrowths of fluorite and calcite. The inclusions within calcite occur as either pure fluorite, with associated REE minerals within the surrounding calcite, or as mixed calcite-fluorite inclusions, with associated zirconosilicate minerals. Consideration of the nature of the texture, and the proportions of fluorite and calcite present(～29 and 71 mol%,respectively), indicates that these textures most likely formed either through the immiscible separation of carbonate and fluoride melts, or from cotectic crystallization of a carbonatefluoride melt. Laser ablation ICP-MS analyses show the pure fluorite inclusions to be depleted in REE relative to the calcite. A model is proposed, in which a carbonate-fluoride melt phase enriched in Zr and the REE, separated from a phonolitic melt, and then either unmixed or underwent cotectic crystallization to generate an REE-rich carbonate melt and an REE-poor fluoride phase. The separation of the fluoride phase(either solid or melt) may have contributed to the enrichment of the carbonate melt in REE, and ultimately its saturation with REE minerals. Previous data have suggested that carbonate melts separated from silicate melts are relatively depleted in the REE, and thus melt immiscibility cannot result in the formation of REE-enriched carbonatites. The observations presented here provide a mechanism by which this could occur, as under either model the textures imply initial separation of a mixed carbonate-fluoride melt from a silicate magma. The separation of an REEenriched carbonate-fluoride melt from phonolitic magma is a hitherto unrecognized mechanism for REE-enrichment in carbonatites, and may play an important role in the formation of shallow magmatic REE deposits. 相似文献
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《Applied Geochemistry》1996,11(3):481-487
Geological studies demonstrate that liquid immiscibility in felsic magma closely associates with the ore forming process. In order to obtain experimental evidence demonstrating the relationship between the ore forming process and liquid immiscibility in felsic magma, we carried out a series of experiments at high temperature and atmospheric pressure. The experimental results show that the granite ∼ KBF4∼Na2MoO4 system is a homogeneous melt at high temperature. With decrease in temperature, however, the melt decomposes into two immiscible melts: silicate melt and ore-forming melt. The ore-forming melt exists as globules in the silicate phase. Molybdenm, Ca, Na, Mg, P, Mn, F, B, and OH are concentrated in these globules. The ore forming melt is characterized with very low SiO2 and Al2O3 concentrations but the concentration of MoO3 and CaO is very high. In contrast, the silicate melts are significantly enriched in SiO2 and Al2O3, and depleted in MoO3 and CaO. In the silicate melt the concentrations of network modifying elements (e.g. Mo, Ca, Na, P, Mg) and volatiles (F, OH) are very low. The differences between the two immiscible melts exist not only in chemical composition but also in structure. The ore-forming melt structurally consists of [MoO4], [MoOF4], [B(OH)4], and OH, while the silicate melt is [Si04]. Because of the difference in composition and structure the two immiscible melts possess different physical properties. Compared to silicate melt, the ore-forming melt has a lower density and viscosity, which permits the globules to behave as bubbles in granite magma and to move and concentrate in the upper part of magma chamber. This process is probably responsible for the concentration of ore-forming elements in the upper part of granite bodies and their immediate aureoles. The present experimental results suggest that liquation in felsic magma can be the first step in the ore-forming process during granitoid evolution. 相似文献
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Richard F. Wendlandt Wendy J. Harrison 《Contributions to Mineralogy and Petrology》1979,69(4):409-419
Melting relations at 5 and 20 kbar on the composition join sanidine-potassium carbonate are dominated by a two-liquid region that covers over 60% of the join at 1,300 ° C. At this temperature, the silicate melt contains approximately 19 wt% carbonate component at 5 kbar and 32 wt% carbonate component at 20 kbar. The conjugate carbonate melt contains less than 5 wt% silicate component, and it varies less as a function of temperature than does the silicate melt.Partition coefficients for Ce, Sm, and Tm between the immiscible carbonate and silicate melts at 1,200 ° and 1,300 ° C at 5 and 20 kbar are in favor of the carbonate melt by a factor of 2–3 for light REE and 5–8 for heavy REE. The effect of pressure on partitioning cannot be evaluated independently because of complementary changes in melt compositions.Minimum REE partition coefficients for CO2 vapor/carbonate melt and CO2 vapor/silicate melt can be calculated from the carbonate melt/silicate melt partition coefficients, the known proportions of melt, and maximum estimates of the proportion of CO2 vapor. The vapor phase is enriched in light REE relative to both melts at 20 kbar and enriched in all REE, especially the light elements, at 5 kbar. The enrichment of REE in CO2 vapor relative to both melts is 3–4 orders of magnitude in excess of that in water vapor (Mysen, 1979) at 5 kbar and is approximately the same as that in water vapor at 20 kbar.Mantle metasomatism by a CO2-rich vapor enriched in light REE, occurring as a precursor to magma genesis, may explain the enhanced REE contents and light REE enrichment of carbonatites, alkali-rich silicate melts, and kimberlites. Light REE enrichment in fenites and the granular suite of nodules from kimberlites attests to the mobility of REE in CO2-rich fluids under both mantle and crustal conditions. 相似文献
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富F熔体-溶液体系流体地球化学及其成矿效应--研究现状及存在问题 总被引：5，自引：0，他引：5
高度演化花岗岩类多为富F的熔体溶液体系 ,具有鲜明的、不同于其他体系的地球化学行为。富F岩浆固相线和液相线的降低和岩浆寿命的延长 ,使残余熔体与热水热液的性状差异减小 ,模糊了岩浆与热液之间的界线。最近对于富F、B和P伟晶岩中熔融包裹体的研究获得了新的进展。在约 70 0～ 5 0 0℃的温度和 1 0 0 0× 1 0 5Pa的压力下 ,在伟晶岩石英中发现两种不同类型的熔体包裹体 ,一种是富硅酸盐、贫水的熔体包裹体 ,另一种是贫硅酸盐、富水的熔体包裹体。两种熔体在硅酸盐 (+F +B +P) 水体系的溶离线边界上同时被圈闭。这表明 ,在地壳浅部侵位的侵入体 ,当温度≥ 70 0℃时 ,水在富F、B和P的熔体中可以无限混溶 ;而一旦温度降低 ,就会分离为两种共存的熔体并伴随强烈的元素分异作用。在溶离线的富水一侧形成与正常硅酸盐熔体有很大不同的高度富挥发份的熔体 ,这种致密、高粘度、高扩散性以及高活动性的超富水 (hyper aqueousmelt)熔体 ,可以与水溶液流体相类比。这为岩浆热液过渡性流体的假说提供了新的有利的证据。此外 ,在这种具有超富水和熔体特征的过渡性流体中 ,微迹元素可能具有特殊的地球化学行为 ,如在许多晚期花岗岩包括淡色花岗岩和伟晶岩中稀土元素配分模式所显示的四分组效应等。富F熔体溶液体? 相似文献