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1.
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
2.
岩浆作用的物理过程研究进展 总被引：8，自引：0，他引：8
概略地介绍了８０年代以来硅酸盐熔体及硅酸盐晶－液悬浮体的密度、粘度、熔体结构、流全动力学等方面的研究动向,及其对岩浆作用、岩浆运移、岩浆侵位机制的动力学约束条件,硅酸盐熔体的结构是制约熔粘度的主导因素,化学成分对熔体匠控制是通过改变熔体结构而实现的,粘度在一定程度上决定着岩浆的迁移、侵痊和喷发方式。密度和浮力是岩浆上升侵位的重要约束,地壳是岩交涉升的一个密度过滤器岩浆最终由于浮和的消失而停止上升。 相似文献
3.
近年来研究表明岩浆的物理及化学性质与其熔体结构密切相关，因此熔体结构的研究对于理解岩浆的性质及岩动力学等与岩浆作用相关的地质问题是非常重要的。本文概括介绍了熔体结构的研究进展，着重讨论了熔体中熔体组分、温度及压力对熔体结构的影响。此外，并对硅酸盐熔体结构的研究意义进行了论述。 相似文献
4.
通过高温熔融，对同结线附近一系列硅酸盐熔体进行淬冷或不同速度冷却，实验获得的样品经过显微拉曼光谱分析，对比研究了AbxAnxDiy系列熔体在不同结线附近熔体结构跨相区变化情况，以及析出晶体对相应熔体结构的继承特点，熔体结构单元相对含量，在相界线两侧有某种程度的突变，熔体结构的变化对熔体的粘度，密度影响不同，拉曼光谱检测显示，硅酸盐玻璃的结构对降温速度变化不敏感，晶体对其相应熔体结构的部分继承作用，可能意味着晶体生长单元与熔体结构单元密切相关。 相似文献
5.
通过研究硅酸盐熔体的氧平均体积,并与硅酸盐玻璃相对比,提出硅酸盐熔体的体积可分为两部分,即硅-氧骨架部分和阳离子部分,根据氧平均体积变化规律,得出硅-氧骨架部分的体积基本不随温度变化,硅酸盐熔体的体积膨胀主要是由于“氧化物”部分的局部膨胀所致,进一步提出O~(2-)半径基本不变,而主要是阳离子半径变化,并讨论了膨胀的机制。 相似文献
6.
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
7.
《矿物岩石地球化学通报》2017,(1)
水是地球岩浆中的一种主要挥发分。水的存在导致岩石的熔融温度降低,其根本原因在于水易溶于硅酸盐熔体。本文总结了在地球岩石圈温压条件下,水在硅酸盐熔体中的赋存形式、溶解度与水对熔体物理性质的影响。熔体中溶解的水以H_2O分子和OH形式存在。水在熔体中的溶解度随压力的升高而增大。当温压条件位于含水硅酸盐体系的临界曲线之上时,甚至可能形成成分介于硅酸盐熔体和富水流体之间的超临界流体。水使熔体的密度和黏度降低,更易于脱离源区向上运移。水使元素扩散加快,有利于晶体和气泡的生长。水导致熔体的电导率升高,使部分熔融造成的电导率异常更加显著。水对硅酸盐熔体迁移性质的影响以及水的溶解行为都与水的种型分异反应密切相关。在研究与熔融有关的地质过程时必须充分考虑水的作用。 相似文献
8.
天然湿岩浆熔体结构的计算 总被引：2，自引：0，他引：2
本文在前人有关合成和天然硅酸盐干岩浆体系熔体结构的研究基础上,综合了H_2O、CO_2、F和S在岩浆中结构作用的最新研究成果,提出了一个天然湿岩浆熔体结构的计算方案。将该法应用于火成岩的实际研究中,有助于更深入地理解岩浆作用的物理化学问题。 相似文献
9.
《地球化学》2017,(4)
岩庄陨石是受强烈冲击的H群普通球粒陨石,含有厘米级宽度的熔脉和熔块。冲击熔体中微量元素的分布,对了解在高温低压下从熔体分离结晶物相的元素再分配具有重要价值。本文以岩庄陨石中的全岩熔体、硅酸盐熔体和FeNi+FeS共结团粒中的FeNi金属三种物相为研究对象,利用激光剥蚀等离子体质谱技术,分别对其进行微量元素分析。结果表明:(1)该陨石冲击熔融后,Fe、Co和Ni等亲铁元素主要富集在全岩熔体内的FeNi金属相中,而Cr、V、Ti和Mn等则主要进入从硅酸盐熔体中晶出的微晶辉石晶格内,以置换M1位上的Al~(3+)。(2)Cu、Ga和Pb等亲铜元素也大部分都富集在FeNi金属相中,而挥发性较强的Zn,在陨石熔融时虽有少量丢失,但主要进入硅酸盐熔体相内,赋存在微晶橄榄石和辉石晶格之中以置换Fe~(2+)。(3)Sc、Zr、Nb和Ta等亲石元素,基本上都赋存在硅酸盐熔体相中,但Nb和Ta的分异程度低,而FeNi金属相的Nb/Ta比值比硅酸盐熔体要偏低一倍多,说明高温高压下陨石熔融时,Nb比Ta更为活泼。(4)硅酸盐熔体和全岩熔体的稀土元素分布均具有明显的奇偶效应,总体呈现轻稀土富集,重稀土亏损的特点,而FeNi金属则呈现轻稀土相对亏损的特点,且其稀土总量比硅酸盐熔体低近三倍,说明稀土元素特别是轻稀土元素主要赋存在硅酸盐熔体中。铂族元素在陨石局部熔融后转移到共结团粒的FeNi金属之中。 相似文献
10.
水作为深熔熔体中最常见的一种挥发分,是影响熔体的物理和化学性质的主要因素.由于现有的测试技术以及熔体包裹体自身的局限性,很难定量确定熔体包裹体中水的含量和种型,导致对俯冲带熔体产生机制和演化过程的认识也极为有限.共聚焦显微激光拉曼光谱仪具有高的空间分辨率、快速、无损分析、样品制备简单等优点,且可分析暴露于表面或包裹于内部的样品,因此对探测微小熔体包裹体具有极大的优势.该方法的原理是基于拉曼谱峰高度/强度与其对应基团含量具有良好的线性关系,以人工合成硅酸盐玻璃为标准样品,用于硅酸盐熔体包裹体中水的含量和种型的定量限定.作为新发展起来的技术和方法,越来越多地引起地质学家的关注,但是目前大量的研究还集中于该分析方法自身的推演和校正,对天然样品的研究还相对缺乏.目前有限的研究表明,该方法可被广泛应用于岩浆岩和高级变质岩体系中,不仅可定量限定岩浆岩基质或斑晶中硅酸盐熔体包裹体水含量,有效示踪岩浆侵入或喷发过程中岩浆的流变学行为;而且可定量限定俯冲带内经历过部分熔融的高级变质岩中代表初始熔体的多晶矿物包裹体中水的含量和种型,示踪俯冲带熔体组成和演化,进而为研究深俯冲地壳分异、板片-地幔楔界面的熔体交代作用等重要问题提供新的制约. 相似文献
11.
Russell O. Colson 《Contributions to Mineralogy and Petrology》2010,159(5):703-717
Reduction potentials (E
0) and diffusion rates (D) for divalent nickel in a variety of silicate melts and as a function of temperature have been measured in situ using voltammetric
methods. These measurements provide an indirect window into structural changes in melts at temperatures above the liquidus.
Slope of the reduction potential versus temperature (related to entropy) and slope of the diffusion rate versus 1/T (related to diffusional activation energy) remain roughly constant or change only gradually above the liquidus, with the
exception of a sharp break in slope typically observed about 60–160°C above the liquidus. This sharp break is consistent with
a structural transition in the melt rather than with a gradual change in melt structure. A correlation between the transition
temperature and the liquidus temperature, combined with the qualitative effect of prior crystallization, suggests that the
transition may be related to the melt “preparing” for crystallization roughly 100°C above the liquidus. These observations
may have implications for understanding melt activities, partitioning between melt and crystalline phases, and liquid immiscibility. 相似文献
12.
Molecular dynamics simulations are carried out to systematically address the effects of composition and pressure on melts along the MgO-SiO2 join and elucidate the role of structural modifier content on silicate melt properties. The MgO-SiO2 system shows non-ideal mixing with a negative excess volume of mixing at low pressures, but the mixing becomes closer to ideal at higher pressures. At atmospheric pressure, the viscosities and diffusivities vary by more than 3 orders of magnitude as the composition is varied along this join, with the low SiO2 melts characterized by lower viscosities and higher diffusivities; these results are in quantitative agreement with experimental results for the dependence of viscosity and diffusivity on structural modifier content in a wide range of silicate systems. The transport properties of melts in this system converge at higher pressures; at pressures greater than ∼15 GPa the viscosity and diffusivities vary by less than an order of magnitude across the entire range of compositions. The relevance of equations that relate the viscosity and diffusivity is also addressed. 相似文献
13.
《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
14.
The knowledge from the compression behavior of densified SiO2 glass suggests that SiO2 melt may behave as a single phase having a densified network structure (intermediate-range order) at the pressure condition of the Earth’s deep upper mantle, including the transition zone. A simple and easy-to-use equation of state of silicate melts which is applicable to a wide range of chemical composition at the pressure condition of the deep upper mantle is proposed based on the assumption that SiO2 component is in its densified state (or phase). The equation of state proposed in this study is consistent with all the available density data of silicate melts with an SiO2 content of about 35–55 mol% measured with large-volume presses at pressures between 8 and 22 GPa. The equations of state in previous studies differ considerably from each other. The main reason for the discrepancies seems to be that the compression behavior of multiple states (or phases) of silicate melts has been described in most cases with a single equation of state. It is necessary to consider that silicate melts are in their densified states (or phases) in the deep upper mantle. 相似文献
15.
The paper discusses the formation conditions of the Ary-Bulak ongonite massif (eastern Transbaikalia). Studies of melt and fluid inclusions have shown that, along with crystalline phases and a silicate melt, ongonitic magma contained aqueous–saline fluids of different types, fluoride melts compositionally similar to fluorite, sellaite, cryolite, chiolite, and more complex aluminum fluorides as well as silicate melts with abnormal Cs and As contents. An ongonite melt crystallized with the participation of P–Q fluids as vapor solutions, presumably NaF-containing and slightly admixed with chlorides. We studied the properties and composition of brine inclusions from Ca- and F-rich rocks on the margin of the massif. Depending on the thermophysical properties of the host rocks and ongonite melt, the duration of its crystallization has been estimated for a magma chamber of the size and shape of the Ary-Bulak massif. Magma chamber cooling has been modeled, and the density, viscosity, and Rayleigh number of the ongonite melt have been estimated from the composition of silicate glasses in melt inclusions. These data strongly suggest intense convection in the residual magma chamber lasting for centuries. We have calculated possible fluid overpressure during the crystallization and degassing of the ongonite melt in a closed magma chamber.Calcium- and fluorine-rich aphyric and porphyritic rocks on the southwestern margin of the massif might have formed by the following mechanism. Local decompression in the magma chamber quenched an oxygen-containing calcium fluoride melt accumulated at the crystallization front, and then these rocks altered during the interaction with fluids. When penetrating the marginal zone, a P–Q magmatic fluid which coexisted with the melt in the residual chamber cooled and changed its composition and properties. This caused the fluid to boil and segregate into immiscible phases: a vapor solution and a brine extremely rich in Cl, F, K, Cs, Mn, Fe, and Al. The fluoride and silicate liquids were immiscible; the silicate melts had abnormal Cs and As contents; changes in the composition and properties of the magmatic fluids caused them to boil and produce brines. All this is evidence for complex fluid–magma interaction and heterogeneous ongonitic magma during the crystallization of the Ary-Bulak rocks. These processes were favored by the low viscosity and high mobility of the F- and water-rich ongonite melt, intense melt convection in the residual chamber, and rising fluid pressure during its degassing. 相似文献
16.
为探讨长英质岩浆作用过程中金属成矿元素的地球化学行为及其成矿意义，我们进行了常压下花岗岩－ＫＢＦ３－Ｎａ２ＭｏＯ４－ＷＯ３体系的实验研究。结果表明，高温（１２５０℃）条件下呈均一状态的花岗岩－ＫＢＦ４－ＮａＭｏＯ４－ＷＯ３体系，当温度降低时发生液态不混溶，从中分离出含矿熔体的小液滴，体系中的Ｍｏ（Ｗ）几乎全部富集在这种小液滴中。含矿熔体中极富含Ｃａ、Ｍｇ和Ｐ，而贫Ｓｉ、Ａｌ和Ｋ，Ｈ２Ｏ和Ｆ富集在含矿熔体中。此实验结果表明：长英质岩浆中液态不混溶作用的发生可以使成矿元素Ｗ和Ｍｏ富集到与硅酸盐熔体不混溶的独立的非硅酸盐熔体中。这种熔体在适当的地质条件下继续演化可形成类似镁铁质岩浆演化过程中常出现的岩浆熔离型矿床。本实验结果可能为斑岩矿床的形成机理提供一种新的解释。 相似文献
17.
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
18.
Mineral/melt partitioning of trace elements during hydrous peridotite partial melting 总被引：6，自引：4，他引：2
This experimental study examines the mineral/melt partitioning of incompatible trace elements among high-Ca clinopyroxene, garnet, and hydrous silicate melt at upper mantle pressure and temperature conditions. Experiments were performed at pressures of 1.2 and 1.6 GPa and temperatures of 1,185 to 1,370 °C. Experimentally produced silicate melts contain up to 6.3 wt% dissolved H 2O, and are saturated with an upper mantle peridotite mineral assemblage of olivine+orthopyroxene+clinopyroxene+spinel or garnet. Clinopyroxene/melt and garnet/melt partition coefficients were measured for Li, B, K, Sr, Y, Zr, Nb, and select rare earth elements by secondary ion mass spectrometry. A comparison of our experimental results for trivalent cations (REEs and Y) with the results from calculations carried out using the Wood-Blundy partitioning model indicates that H 2O dissolved in the silicate melt has a discernible effect on trace element partitioning. Experiments carried out at 1.2 GPa, 1,315 °C and 1.6 GPa, 1,370 °C produced clinopyroxene containing 15.0 and 13.9 wt% CaO, respectively, coexisting with silicate melts containing ~1–2 wt% H 2O. Partition coefficients measured in these experiments are consistent with the Wood-Blundy model. However, partition coefficients determined in an experiment carried out at 1.2 GPa and 1,185 °C, which produced clinopyroxene containing 19.3 wt% CaO coexisting with a high-H 2O (6.26±0.10 wt%) silicate melt, are significantly smaller than predicted by the Wood-Blundy model. Accounting for the depolymerized structure of the H 2O-rich melt eliminates the mismatch between experimental result and model prediction. Therefore, the increased Ca 2+ content of clinopyroxene at low-temperature, hydrous conditions does not enhance compatibility to the extent indicated by results from anhydrous experiments, and models used to predict mineral/melt partition coefficients during hydrous peridotite partial melting in the sub-arc mantle must take into account the effects of H 2O on the structure of silicate melts. 相似文献
19.
.Dr H. Taniguchi 《Mineralogy and Petrology》1993,49(1-2):13-25
Summary Density and viscosity measurements of three melts of volcanic rock composition (basalt and andesite) at low temperatures were carried out to understand the role of free volume in the viscous behavior of a magma and to estimate the flow unit in the melts. The data combined with literature data suggest the following conclusion: free-volume theory is not applicable to these silicate melts; the relation between viscosity and the inverse of free volume does not yield a straight line in a wide temperature range from the glass-transion temperature to 1550°C. However, two depolymerized melts, diopside and Oki-Dozen alkali basalt (OAB), yield almost linear relationships. Thus, the free-volume theory should hold to a fairly good approximation for these two melts. Based on this approximation, the radius of flow unit for diopside melt was calculated to be about 4.7 Å, and that for Oki-Dozen alkali basalt to be about 4.2 Å. The three-dimensional silicate anions which may correspond to the flow unit are Si14O35
14– and Si16O40
16– for diopside melt, and Si10O25
10– and Si12O30
12– for OAB melt. The temperature effect on the initial slope of the viscosity-pressure relation has also been examined in the frame of free-volume theory. It was concluded that the relative increase of the initial slope of the relation with increasing temperature might be caused by the increase of free volume.With 6 Figures 相似文献
20.
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