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51.
Abstract We carried out hydrothermal experiments in the system dolomite‐quartz‐H2O to track the temporal change in reaction rates of simultaneous reactions during the development of reaction zones. Two types of configurations for the starting materials were prepared: dolomite single crystals + quartz powder + water and quartz single crystals + dolomite powder + water, both sealed separately in gold capsules. Runs at 0.1GPa and 600°C with cold seal pressure vessels gave the following results. (i) In short duration (45–71 h) runs metastable layer sequences involving wollastonite and talc occur in the reaction zone, whereas they disappear in longer duration (168–336 h) runs. (ii) The layer sequence of the reaction zones in short duration runs differs from place to place on the dolomite crystal even in the same run. (iii) The diversity of layer sequences in the short duration runs merges into a unique layer sequence in the longer duration runs. (iv) The reaction zone develops locally on the dolomite crystal, but no reaction zone was observed on the quartz crystal in any of the runs. The lines of evidence (i)–(iii) show that the system evolves from an initial transient‐ to a steady‐state and that the kinetic effect is important in the development of reaction zones. A steady diffusion model for the unique layer sequence Qtz/Di/Fo + Cal/Dol + Cal/Dol shows that the Dol + Cal layer cannot be formed by diffusion‐controlled process and that the stability of the layer sequence Qtz/Di/Fo + Cal/Dol depends not only on L‐ratios (a = /LCaOCaO and b = /LMgOMgO) but also on the relative rate P = (−2ξ1 − ξ2)/(–ξ1 − 2ξ2) of competing reactions: Dol + 2Qtz = Di + 2CO2 (ξ1) and 2Dol + Qtz = Fo + 2Cal + 2CO2 (ξ2). For smaller P the stability field will shift to higher values of a and b. The steady diffusion model also shows that the apparent‐non‐reactivity on the quartz surface can be attributed to void formation in a large volume fraction in the diopside layer. 相似文献
52.
Abstract A detailed field and petrological study of rocks from nappes cut by the Valle dell'Orco (Italian Western Alps), in particular the Sesia–Lanzo composite unit, has revealed geological and metamorphic histories which started in pre-alpine times and lasted up to the alpine subduction-collisional processes. During these processes the nappes sustained an early high P–low T stage and a later low P greenschist facies stage, but followed partly distinctive P–T–time trajectories. This paper discusses the kinematic evolution and the thermal history of the alpine belt from the early subduction/underthrust to the later exhumation stage. The metamorphic crystallization is often governed by incomplete and/or local equilibrium, and the pervasive syn-metamorphic deformation and the composition of the syn-metamorphic fluid phase (if present) have exerted an effective local control on reaction kinetics. 相似文献
53.
A. J. ZINGG 《Journal of Metamorphic Geology》1995,13(3):431-443
Abstract End-member, continuous and degenerate reactions are derived for the multisystem with the six components Na2O, CaO, (Mg/Fe)O, Al2O3, SiO2, H2O among the phases plagioclasess, garnetss, amphiboless, cpx, opx, olivine, spinel, quartz and an aqueous fluid. The chemography of this system is degenerate due to the co-linearity 2Opx = Ol + Qtz. This co-linearity has its implications both on reaction space and phase equilibria. From a total of 28 reaction systems, reaction space is derived for nine subsystems (phases in parentheses are absent): Case A1: (Cpx,Ol) (Cpx,Opx) and (Cpx,Qtz), Case A2: (Spl,Ol) (Spl,Opx) and (Spl,Qtz), Case B: (Ol,Opx) (Ol,Qtz) and (Opx,Qtz). In the absence of either cpx or spl (case A), three reactions form an invariant point, either [Cpx] or [Spl], where the co-linear phases olivine, opx and quartz coexist on the transformation line 2Opx = Ol + Qtz. Changing mineral compositions force invariant points to move along the line with the different reaction curves changing their relative position according to Schreinemakers’rules. Zero contours, i.e. the location where (a) phase(s) disappear(s) in reaction space correspond to singular points in phase diagrams. Two types are distinguished; singular points of indispensable and of substitutable phases. In the first case the phase disappears from the entire bundle while in the second it disappears from a single reaction. In the specific case where the substitutable phases are also the co-linear ones, two of the three co-linear phases disappear simultaneously. Two of the three reaction curves coincide. In the system including Cpx and Spl (Case B) three reactions, (Ol,Opx) (Ol,Qtz) and (Opx,Qtz), oppose three invariant points, [Ol], [Opx] and [Qtz]. Invariant points no longer move along the line 2Opx = Ol + Qtz. The coincidence of the zero contours of all three co-linear phases in reaction space-the result of the chemographic degeneracy-causes the respective singular points to coincide in the phase diagrams. This is the location where curves must be rearranged in a bundle to conform Schreinemakers’rules. The reaction Grs1Prp2= 2 Ol + An is fourth order degenerate and part of all nine subsystems (cases A and B). It can be used to relate the different phase diagrams to one another. 相似文献
54.
Diana Rodriguez Ana Rodriguez Amparo Soto Alfonso Aranda Yolanda Diaz-de-Mera Alberto Notario 《Journal of Atmospheric Chemistry》2008,59(3):187-197
The reactions of three structurally similar unsaturated alcohols, 2-buten-1-ol (crotyl alcohol), 2-methyl-2-propen-1-ol (MPO221)
and 3-methyl-2-buten-1-ol (MBO321) with Cl atoms, have been investigated for the first time, using a 400 l Teflon reaction
chamber coupled with gas chromatograph-coupled with flame-ionization detection (GC-FID). The experiments were performed at
atmospheric pressure and at temperatures between 255 and 298 K, in air or nitrogen as the bath gas. The obtained kinetic data
were used to derive the Arrhenius expressions , , (in units of cm3 molecule−1 s−1). Finally, atmospheric lifetimes of those unsaturated alcohols with respect to OH, NO3, O3 and Cl have been calculated. 相似文献
55.
纳米镍/铁去除氯代烃影响因素的探讨 总被引:10,自引:0,他引:10
氯代烃是地下水中最常检出的有机污染物之一,传统的处理方法去除率很低。近年来随着铁还原技术的发展,纳米铁和纳米双金属也成为一个活跃的研究领域。利用批实验的研究方法以四氯乙烯(PCE)和四氯化碳(CT)为目标污染物,研究纳米镍/铁在去除PCE过程中的影响因素。实验结果表明,在碱性条件下,纳米Ni/Fe对PCE脱氯速率比在酸性和中性条件下脱氯速率更快;纳米Ni/Fe对初始浓度为6·51mg/L的PCE溶液脱氯速率是对初始浓度为20·56mg/L的PCE溶液脱氯速率的1·8倍;对于氯代程度相同的CT和PCE,对CT的脱氯速率明显快于对PCE。 相似文献
56.
57.
WU Daqing DIAO Guiyi YUAN Peng PENG Jinlian 《《地质学报》英文版》2006,80(2):192-199
The adsorption of pentachlorophenol (PCP) onto quartz, kaolinite, illite, montmorillonite and iron oxides has been investigated by batch equilibrium techniques. The pH-dependent isotherms are curves with peak values, the position of which is at about pH = 5-6 depending on the mineral species. Based on distribution of both speciation of surface hydroxyls on minerals and PCP in solution a surface reaction model involving surface complexation and surface electrostatic attraction is presented to fit the pH-dependent isotherms, and both reaction constants are calculated. The results show that on quartz and phyllosilicate minerals the predominant adsorption reaction is surface complexation, meanwhile both of surface electrostatic attraction and surface complexation are involved on the iron oxide minerals. The reaction constants of surface electrostatic adsorption are usually one to three orders in magnitude, larger than that of surface complexation. The concentration-dependent isotherms can be well fitted by Langmnir equation with the correlation coefficient R〉0.93 for kaolinite and iron oxides. The maximum adsorption is found in the order: hematite 〉 lepidocrocite 〉 goethite 〉 kaolinite 〉 quartz 〉 montmorillonite ≈ illite, which can be interpreted by consideration of both reaction mechanism and surface hydroxyl density. The significant adsorption of PCP onto mineral surfaces suggests that clay and iron oxide minerals will play an important role as HIOCs are adsorbed in laterite or latertoid soil, which is widespread in South China. 相似文献
58.
钾长石分解反应热力学与过程评价 总被引:2,自引:2,他引:2
综述了添加各种助剂分解钾长石的研究进展。对不同体系中钾长石分解反应的G ibbs自由能和能耗计算,综合考虑一次性资源、能源消耗量和烧结过程的环境相容性、产品方案等因素,结果表明:只有以石灰石、碳酸钠为配料的工艺路线具有实际工业应用价值;而唯有以碳酸钠为配料时,钾长石原料烧结过程才具有一次性资源消耗量最少、能耗最低、温室气体CO2排放量最小、且可生产高附加值产品、实现完全清洁生产等优点。因此,选择以碳酸钠为配料分解钾长石的技术路线,具有良好的工业化应用前景。 相似文献
59.
60.
湿斜压大气中暴雨中尺度系统发展的一种可能机制 总被引:1,自引:0,他引:1
根据暴雨中尺度系统发生时的大气运动特征,在绝热、无摩擦条件下,从湿斜压原始方程出发,考虑大气运动的涡度及散度演化不仅受动力场的制约,而且还受到热力场的约束,采用不同于传统研究涡度及散度方程的分析方法,导出了新形式的涡度及散度方程。在此基础上,分析了湿斜压大气中对流层中低层气流旋转与辐合持续增长的动力特征,初步揭示了湿斜压大气中暴雨中尺度系统发展的动力机制。 相似文献