Equilibrium and disequilibrium degassing of a phonolitic melt (Vesuvius AD 79 “white pumice”) simulated by decompression experiments     

Giada Iacono Marziano  Burkhard C. Schmidt  Daniela Dolfi 《Journal of Volcanology and Geothermal Research》2007

Equilibrium and disequilibrium degassing of a volatile phase from a magma of K-phonolitic composition was investigated to assess its behavior upon ascent. Decompression experiments were conducted in Ar-pressurized externally heated pressure vessels at superliquidus temperature (1050 °C), in the pressure range 10–200 MPa using pure water as fluid phase. All experiments were equilibrated at 200 MPa and then decompressed to lower pressures with rates varying from 0.0028 to 4.8 MPa/s. Isobaric saturation experiments were performed at the same temperature and at 900–950 °C to determine the equilibrium water solubility in the pressure range 30–250 MPa. The glasses obtained from decompression experiments were analyzed for their dissolved water content, vesicularity and bubble size distribution. All decompressed samples presented a first event of bubble nucleation at the capsule–melt interface. Homogeneous bubble nucleation in the melt only occurred in fast-decompressed experiments (4.8 and 1.7 MPa/s), for ΔP ≅ 100 MPa. For these decompression rates high water over-saturations were maintained until a rapid exsolution was triggered at ΔP > 150 MPa. For slower rates (0.0028, 0.024, 0.17 MPa/s) the degassing of the melt took place by diffusive growth of the bubbles nucleating at the capsule–melt interface. This process sensibly reduced water over-saturation in the melt, preventing homogeneous nucleation to occur. For decompression rates of 0.024 and 0.17 MPa/s low water over-saturations were attained in the melt, gradually declining toward equilibrium concentrations at low pressures. A near-equilibrium degassing path was observed for a decompression rate of 0.0028 MPa/s. Experimental data combined with natural pumice textures suggest that both homogeneous and heterogeneous bubble nucleations occurred in the phonolitic magma during the AD 79 Vesuvius plinian event. Homogeneous bubble nucleation probably occurred at a depth of ∼ 3 km, in response to a fast decompression of the magma during the ascent.  相似文献   

浅水环境中垂向圆形纯射流的试验研究   总被引：3，自引：0，他引：3       下载免费PDF全文

槐文信  那宇彤  黄纪忠  童汉毅  姜国强 《水科学进展》2002,13(1):26-30

对静止均匀浅水水域中的铅垂圆形单孔射流进行了试验研究,试验是在实验室的自制恒定水流循环系统中进行的。得到了水面的隆起高度与射流出口单位能量和相对水深的函数关系;验证了隆起高度分布具有自相似性,并给出其统一表达式;借助于三维测速仪,得到了射流流速的横断面分布、射流中线流速的衰减规律和流场的流函数等值线。  相似文献   

裂隙概化模型的非饱和渗流试验研究   总被引：4，自引：1，他引：4       下载免费PDF全文

詹美礼  胡云进  速宝玉 《水科学进展》2002,13(2):172-178

借鉴多孔介质非饱和渗流试验的研究成果,研制出一套可同时测定单裂隙毛细压力-饱和度以及非饱和渗透系数-毛细压力关系的试验装置.为检验试验装置的可信度和试验原理的正确性,并初步探讨单裂隙非饱和渗流的机理,特制作了一阶梯开度的裂隙概化模型(本文称之为“S-H”裂隙模型),并在上述试验装置上进行了“S-H”裂隙模型的非饱和渗流试验,初步阐明了单裂隙非饱和渗流的一些基本水力特性,同时试验结果也表明本文试验装置和试验原理合理可靠.  相似文献   

DUT-1合成模型冰的弯曲强度和弹性模量实验分析   总被引：3，自引：0，他引：3       下载免费PDF全文

李志军  王永学  李广伟 《水科学进展》2002,13(3):292-297

依据渤海海冰物理和力学特征值和国内水池实验室能力,以1:10～1:30比尺要求,发展了DUT-1合成模型冰.文中简介该模型冰的理想参数、成分和制备过程.就其弯曲强度和弹性模量进行系统的实验分析.通过500多次弯曲实验,获得该模型冰在不同加载速度下的破坏方式,各向同性证据和弯曲强度为35～65kPa和弹性模量平均53MPa的结果.并且得到弯曲强度和弹性模量在实测湿密度范围内呈递增关系,浸水模型冰性能稳定时间超过4h,弹性模量与弯曲强度之比82%超过2000.  相似文献   

二级结构地震反应的实验研究   总被引：2，自引：0，他引：2  

林均岐 《地震工程与工程振动》2001,21(3):75-78

本文针对结构顶部的附属结构在正弦激励和地震动作用下的反应，设计了多层结构模型并研究了附属结构的多种情况。实验结果表明，附属结构在地震作用下可对主体结构产生不同的影响，根据附属结构的参数的不同可能导致主体结构的反应增大或减小，因此得出结论：在结构设计时对主体结构和附属结构进行整体考虑，能使结构的地震反应控制在最佳的水平。  相似文献   

(斜长石 + 黑云母 + 石英 ) NaCl(NaHCO3) H2O 矿物蚀变与金矿化反应研究 : 450～ 250 ℃和 50 MPa   总被引：1，自引：0，他引：1  

王玉荣  王志祥  张生  胡受奚 《地球化学》2001,30(5):498-503

采用（斜长石＋黑云母＋石英）这三种单矿物组合与1mol/L NaCl或0．5mol/L NaCl 0.5mol/L NaHCO3溶液在450－250℃和50MPa条件下反应7d。实验表明，反应后流体pH值发生了变化，NaCl介质向酸性变化，N aCl NaHCO3介质向中性转化。溶液中K,Ca,Mg,Fe和Au量也随之发生变化。矿物表面发生溶解和离子置换等反应。斜长石表面形成钠长石反应边，黑云母变色，石英重结晶，反应器皿金管中的金被溶解后在金管壁和黑云母表面重结晶，黑云母周边出现红色Fe2O3，在450℃的NaCl介质中，金含量可达1070μg/g，但随温度下降迅速减低，在NaCl NaHCO3介质中，金含量较低，显著，金的活化迁移和富集与Cl,pH,Fe^3 /Fe^2 密切相关，这中金起到示踪作用，显示出金在水／岩反应中的原电池效应。  相似文献   

DUT-1非冻结合成模型冰的弯曲强度   总被引：1，自引：4，他引：1  

李志军  曲月霞  沈照伟  王永学  李广伟 《冰川冻土》2001,23(2):170-175

简介了DUT-1非并结合成模型冰的功能，给出DUT－1模型冰的弯曲强度的测试装置和设备，讨论该模型冰在不同加载速度下的破坏方式和发生峰值弯曲强度的条件，通过悬臂梁上弯和下湾实验结果，说明DUT－1模型冰的各向同性，检验了浸水模型冰性能的稳定性和模型冰湿密度对峰值弯曲强度的效应。  相似文献   

Physical structure features of the crust at southeast region of Tibetan Plateau     

Liu Hongbing  Kong Xiangru  Xiaobing Ma  Wang Qianshen  Yan Yongli  Yan Yafen  Yang Zhiqiang 《中国科学D辑(英文版)》2001,44(1):64-76

Chemical reactions of plagioclase, biotite and their single minerals, as well as a mineral mixture of (plagioclase+biotite+quartz), with KCl and (KCl+KHCO₃) solutions were carried out at 150–400°C and 50–80 MPa. Experiments show that alkaline fluid promotes plagioclase’s changing into potash feldspar, while acid fluid helps plagioclase, potash feldspar and biotite alteration form chlorite and sericite. After chemical reaction the acidity-alkalinity of solutions often changes reversely. It was observed that gold dissolved from the tube wall and recrystallized on the surfaces of biotite and pyrite. Therefore the transportation and enrichment of gold are related to the elementary effect of the fluid-mineral interfaces. Fe³⁺-Fe²⁺, as an oxidition-reduction agent, and volatile components Cl^- and CO₂ play important roles in the reaction process  相似文献   

EXPERIMENTAL GEOCHEMISTRY STUDY ON GOLD IN WATER-ROCK REACTION UNDER THERMAL FLUID SYSTEM AT MESO-LOW TEMPERATURE     

GU Li  DAI Ta-gen 《大地构造与成矿学(英文版)》2001,25(1)

Based on the knowing geochemical characteristics of wall rock in the Mobin gold deposit and composition of fluid inclusion in ore,water-rock experiments were carried out,important achievements are acquired as following: Gold is mainly derived from the ore-bearing wall rock,i,e.,a series of epimetamorphic clastic gritstone,sandy slate,and tuffaceous slate in the Wuqiang Banxi Formation,Wuqiangxi Group.In thermal system with middle-low temperature chlorine gold may be derived form stable complex ions,so it is quite important in gold metallogenic process.Sulphur and chlorine perform as the major negative ions throughout the gold activation and migration movement.The concentration of sulphur and chlorine ions,pH value and temperature are of deciding significance for gold activation,migration and precipitation.  相似文献   

Reporting negative results to stimulate experimental hydrology: discussion of “The role of experimental work in hydrological sciences – insights from a community survey”*     

Tim van Emmerik  Andrea Popp  Anna Solcerova  Hannes Müller  Rolf Hut 《水文科学杂志》2020,65(Z2):1269-1272

ABSTRACT

Experimental work in hydrology is in decline. Based on a community survey, Blume et al. showed that the hydrological community associates experimental work with greater risks. One of the main issues with experimental work is the higher chance of negative results (defined here as when the expected or wanted result was not observed despite careful experimental design, planning and execution), resulting in a longer and more difficult publishing process. Reporting on negative results would avoid putting time and resources into repeating experiments that lead to negative results, and give experimental hydrologists the scientific recognition they deserve. With this commentary, we propose four potential solutions to encourage reporting on negative results, which might contribute to a stimulation of experimental hydrology.  相似文献