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1.
高温地热区土壤微渗漏的温室气体释放通量研究: 以藏南羊八井地热田为例 总被引：1，自引：1，他引：0
土壤微渗漏是地球深部的构造-岩浆活动向大气圈释放温室气体的重要形式之一。近年来,国外许多地热区已经开展了土壤微渗漏温室气体释放通量的定量研究,然而,目前我国尚无该方面的系统研究报道。本文阐述了利用密闭气室法测量地热区土壤微渗漏温室气体释放通量的方法和原理,并将其应用于青藏高原的羊八井地热田。根据研究区的地热活动强度,将羊八井地热田划分为土壤微渗漏释放较弱的A区和土壤微渗漏释放较强的B区。计算结果表明,A区和B区的CO2气体释放通量分别为6.7g·m-2·day-1和98.5g·m-2·day-1。两区释放通量的差异主要受控于断裂的发育程度,即A区位于裂谷的中部,断裂发育程度较差,B区靠近念青唐古拉正断层,断裂发育程度较高,为温室气体的逸出提供了良好的运移通道。羊八井地热田土壤微渗漏CO2气体的释放总量约为8.6×104t·a-1,接近于意大利Vulcano火山区的土壤微渗漏温室气体释放规模(1×105t·a-1)。研究区的气体同位素组分测试结果显示,He同位素值介于0.107RA~0.648RA(RA为大气3He/4He比值),δ13C值介于-11.33‰~-6.79‰(vs.PDB),表明羊八井地热田的温室气体可能主要来源于大陆俯冲环境下的加厚陆壳,其温室气体释放通量的规模主要受控于地壳的岩浆活动以及南北向裂谷拉张作用。羊八井地热田所在的拉萨地块是青藏高原温室气体释放活动最强烈的区域之一,以往的研究表明,青藏高原出露大量新生代火山、地热区,开展火山、地热区温室气体释放通量的研究将有助于深入理解地质因素向当今大气圈释放温室气体的规模等与深部碳循环相关的科学问题。 相似文献
2.
腾冲火山区的现代幔源氦释放:构造和岩浆活动意义 总被引：6，自引：3，他引：3
深地震测深(DSS)和大地电磁测深(MT)都表明腾冲火山区现今仍存在壳内岩浆囊,但对其数量和空间分布还存在分歧并缺乏全貌性认识。MT探测认为腾冲火山区是一个软流圈上涌和岩石圈减薄区,但对这一减薄区的空间范围还缺乏充分的约束。通过对腾冲火山区及外围大范围温泉逸出气体的分析测试,我们共获得了75个温泉逸出气体的氦同位素3He/4He比值数据(部分为前人资料)。利用氦同位素示踪原理,我们研究了腾冲火山区幔源氦释放强度空间分布和时间变化特征,结果发现:腾冲火山区的幔源挥发份释放呈1带3区分布。以3He/4He≥1 Ra,幔源氦比例≥15%为界,腾冲火山区的幔源挥发份释放异常区呈整片分布,为一南北走向的条带,南北长100km,东西宽50km。在整片异常区的内部,腾冲火山区的幔源挥发份释放又有强度不同的3个区域:① 中部腾冲县城-热海一带,3He/4He比值达到5.5 Ra以上,幔源氦比例达到70%以上,释放强度最强。② 北部曲石一带,3He/4He比值达4.5 Ra以上,幔源氦比例达到50%以上,释放强度次之。③ 南部五合-蒲川-新华一带,3He/4He比值达2Ra以上,幔源氦比例达到25%以上,释放强度最弱;腾冲火山区幔源挥发份释放强度在不断升高,其中第3个释放区的3He/4He比值(Ra)升高速率比前两者明显要大。我们认为:腾冲火山区现今幔源挥发份释放强度的空间分布图象就是该地区软流圈上涌和岩石圈减薄区空间尺度和上涌强度的最直接反映,上涌区(减薄区)的大小大致为南北长100km,东西宽50km;腾冲火山区现今存在3个壳内岩浆囊。第1个岩浆囊位于腾冲县城-热海一带,第2个岩浆囊位于马站-曲石一带,第3个岩浆囊位于五合-龙江-团田-蒲川-新华一带;腾冲火山区3个岩浆囊都在不断受到幔源岩浆的持续补充;第1个岩浆囊集幔源挥发份释放、相对地热梯度、地壳形变和地震活动等异常于一身,活动性最强,是未来腾冲火山最可能喷发的地点,需重点监视。第2个岩浆囊的幔源挥发份释放强度也引人注目,需加强监测。第3个岩浆囊规模大,埋深较浅,幔源挥发份释放增加较快,需引起注意。 相似文献
3.
腾冲新生代火山区温泉CO2气体排放通量研究 总被引：6，自引：6，他引：0
近期研究表明,不仅火山喷发期会向当时的大气圈输送大量的温室气体,火山间歇期同样会释放大量的温室气体。在火山活动间歇期,火山区主要以喷气孔、温(热)泉以及土壤微渗漏等形式向大气圈释放温室气体。腾冲是我国重要的新生代火山区,同时也是重要的水热活动区,那里出露大量的温泉,然而目前未见腾冲火山区温泉气体排放通量的研究报道。本文利用数字皂膜通量仪测量了腾冲新生代火山区温泉中CO2的排放通量。研究结果表明,腾冲新生代火山区温泉向当今大气圈输送的CO2通量达3.58×103 t·a-1,相当于意大利锡耶纳Bassoleto地热区温泉中CO2的排放规模。腾冲火山区温泉的CO2释放通量主要受深部岩浆囊、断裂分布、地下水循环、围岩成分等多方面因素的影响。本文根据温泉中CO2的排放特征,将腾冲温泉分为南北两区,南区温泉CO2通量远高于北区的温泉,热海地热区的通量为腾冲CO2通量的最大值。在北温泉区,CO2通量主要受控于断裂的分布;而在南温泉区,除受到断裂控制外,热海地热区底部的岩浆囊及其与围岩的相互作用成为CO2气体的重要物质来源,同时高温的岩浆囊为温泉及CO2的形成提供了重要热源。 相似文献
4.
印度-亚洲大陆俯冲带是地球深部碳循环的重要场所,在全球气候变化研究中占有至关重要的地位。谷露-亚东裂谷是青藏高原南部规模最大、延伸最长的近NS向拉张性裂谷,裂谷内出露新生代火山岩和多处大规模地热区,正在向大气圈释放巨量的温室气体。利用密闭气室法测量并计算得出的谷露和羊应火山-地热区的土壤微渗漏CO_2的平均释放通量分别为436.8g·m~(-2)·day~(-1)和99.0g·m~(-2)·day~(-1),接近具有潜在喷发危险的美国黄石公园火山-地热区(410g·m~(-2)·day~(-1))和加利福尼亚州Mammoth Mountain火山区(107.9g·m~(-2)·day~(-1))的CO_2平均释放通量,表明谷露-亚东裂谷的深部地热流体活动异常强烈。此外,在野外考察的基础上,通过实验室测试和理论计算估算了谷露-亚东裂谷每年以土壤微渗漏的形式向当今大气圈释放的CO_2总量约为1.76×107t,与西特提斯俯冲带前缘的意大利Apennine火山区CO_2的释放总量(1.32×10~7t·a~(-1))属于同一个数量级。因此,印度-亚洲大陆俯冲带是全球地质碳脱气的重要场所。气体地球化学特征显示,谷露-亚东裂谷内火山-地热气体的He同位素比值(0.10~0.29RA,RA为大气3He/4He比值)和δ~(13)CCO_2值(-7.20‰~-0.78‰)在空间分布上表现为,从南至北呈逐渐递增的变化特征,显示裂谷内火山-地热区气体在南北方向上可能具有不同的动力学成因机制。具体来讲,δ~(13)CCO_2值自南向北递增的趋势,可能与裂谷南北方向地层岩性存在差异有关;裂谷内火山-地热气体的He同位素比值高于0.1RA,揭示"重要的地幔组分",同时裂谷内地幔来源的流体组分从南向北逐渐递增的趋势表明,印度大陆岩石圈的向北俯冲作用是导致谷露-亚东裂谷内剧烈的水热活动和大规模温室气体释放最终的动力来源和成因机制。 相似文献
5.
长白山火山区温泉温室气体排放通量研究 总被引：4，自引：3，他引：1
温泉是深部岩浆活动在地表的直接表现,并且向大气圈排放大量的温室气体.然而,国内尚无火山区温泉排放的温室气体通量研究报道.我国长白山火山区水热活动强烈,主要有湖滨温泉带、聚龙温泉群、锦江温泉以及火山口外围的十八道沟温泉.本文利用数字皂膜流量计测量温泉气体排放通量,并结合前人对长白山火山区温泉气体成分的研究成果,估算了研究区温泉所排放的温室气体通量.结果表明,长白山火山区温泉排放的CO2通量为6.9×104t·a-1,CH4排放通量为428.44t·a-1,与意大利Pantelleria Island火山区温泉排放的温室气体通量规模相当.本文的测试结果表明:数字皂膜流量计在火山区温室气体排放通量估算研究中的应用是可行的. 相似文献
6.
中国大陆新生代典型火山区温室气体释放的规模及其成因 总被引：5，自引：5，他引：0
火山活动能够将地球深部的碳输送到大气圈,是地质碳排放和深部碳循环的重要形式.火山作用不仅在喷发期能够释放大量温室气体,而且在休眠期也能释放巨量的温室气体.在全球变暖的背景下,定量化地研究火山活动对大气圈温室气体含量增加的贡献具有至关重要的意义.本文利用密闭气室法等该领域国际先进的测试技术,测量并计算了长白山、腾冲、五大连池及青藏高原南部的羊八井等典型火山区的温室气体释放规模.结果显示,我国大陆新生代典型火山区向大气圈输送的温室气体总通量约为8.13×106t·a-1,接近107t·a-1级别,相当于全球火山活动导致的温室气体(主要为CO2)释放总量的6%左右.太平洋构造域火山区的温室气体在释放通量与总量方面均低于特提斯构造域,并且太平洋构造域火山气体的地壳混染程度较低,显示出大洋俯冲带与大陆俯冲带火山区温室气体释放的成因差异. 相似文献
7.
不同构造域的火山释放CO_2气体的方式、机制和规模具有明显的差异。在全球变暖的大背景下,定量化研究不同类型火山区CO_2气体的释放通量、模拟及计算火山气体的来源演化,对于估算地质源温室气体释放对大气圈温室气体增加的贡献,以及理解地球的深部碳循环过程具有重要意义。近年来,全球火山区CO_2气体释放研究取得了显著进展,尤其在定量研究火山区CO_2气体释放通量的方法、气体源区与地球动力学背景的判定以及不同构造背景的火山区CO_2气体释放特征等领域取得了重大成果。本文综述了不同构造域火山区CO_2气体释放研究的最新成果,详细介绍了我国新生代典型火山地热区的CO_2气体释放研究进展。 相似文献
8.
火山温室气体释放通量与观测的研究进展 总被引：2，自引：0，他引：2
《矿物岩石地球化学通报》2015,(4)
火山活动是地球深部碳循环的重要环节,火山区不仅在火山喷发期能够释放温室气体,而且在休眠期也能向大气圈中释放大量的温室气体。在当前全球温室气体减排的背景下,定量化地研究火山区对大气圈温室气体含量增加的贡献,对于识别自然因素和人类因素碳排放的相对规模、为国际碳排放谈判积累基础数据等均具有至关重要的科学价值和现实意义。本文对火山区温室气体的排放方式与特征、温室气体释放通量与成因的研究方法进行了简要概括,并综述了中国新生代典型火山区温室气体释放通量与成因的研究成果。结合国外温室气体排放研究现状,指出深入研究活火山(包括休眠火山)区的温室气体释放通量与成因对于估算火山来源温室气体的释放规模、建立火山未来喷发预测-预警体系、深入理解岩浆脱气过程与机制等问题均具有至关重要的现实意义和科学价值。 相似文献
9.
10.
板片俯冲过程将地表碳带入地球内部,火山作用将深部碳输送至地球外部圈层,两者构成了地球深部碳循环的主要方式,进而影响了地史时期的气候变化。我国东北新生代火山活动被认为是太平洋板片深俯冲作用的产物,板片俯冲导致岩浆源区强烈的碳酸盐组分交代作用,进而使东北亚上地幔成为一个新生代时期的巨型深部碳库,它的活动和释放将会对全球的气候与环境变化造成重要影响。然而,有关该深部碳库向当今大气圈输送CO_2气体的规模及其演化过程尚不清楚,从而影响了进一步定量评估该碳库在全球变化研究中的地位和作用。针对上述科学问题,本文对我国东北长白山、五大连池和阿尔山火山释放CO_2气体的规模与成因进行了研究。结果表明,东北新生代火山区的土壤CO_2释放通量介于9.6～41.2g·m~(-2)·d~(-1)之间,每年向当今大气圈释放CO_2气体约为2.1Mt(其中,长白山火山区为0.94Mt,五大连池火山区为1.2Mt)。气体地球化学研究证实,长白山与五大连池火山气体均起源于太平洋板片深俯冲环境;但是,与长白山相比,五大连池火山气体具有较高比例壳源组分贡献。阿尔山火山气体的成分与长白山和五大连池火山区存在着明显的差异,它们以N_2为主( 95%),并且其δ~(15)N_(N_2)值高于空气值(1.3‰～1.9‰),~3He/~4He比值较低(0.14～0.18R_A),δ~(13)C_(CO_2)较轻(-13.7‰～-6.2‰),表明壳源富氮有机沉积物的贡献占比较大的比例。上述特征进一步表明,阿尔山火山气体在上升经过地下水时可能滞留了较长时间,混染了大量的陆壳组分,其源区并未受到太平洋板片俯冲物质的显著影响。 相似文献
11.
Aierken Sidike Keyoumu Niyazi Heng-Jiang Zhu K. Atobe N. Yamashita 《Physics and Chemistry of Minerals》2009,36(3):119-126
The photoluminescence (PL) spectra, excitation spectra, and PL decay curves of natural, heat-treated, and γ-ray-irradiated
thenardites from Ai-Ding Salt Lake, Xinjiang, China, were studied. The natural thenardite under 300 nm excitation showed milk-white
luminescence, and the PL spectrum consisted of an extremely broad band with a peak located at approximately 509 nm, spreading
over a wide range of UV and visible wavelengths. The excitation spectra, obtained by monitoring the luminescence at 530 nm,
consisted of a broad band with a peak located at approximately 235 nm and a flat band spreading over a wide range of UV and
visible wavelengths. The PL decay curve of natural thenardite consisted of a fast-decay component with a lifetime of less
than 0.1 μs and a slow-decay component with a half-decay time of approximately 0.4 s. The heat treatment of thenardite at
900°C for 20 min reduced the luminescence efficiency to 1/100. The γ-ray irradiation of thenardite reduced the luminescence
efficiency to approximately half. 相似文献
12.
Deformation-induced polymorphic transformation: experimental deformation of kyanite, andalusite, and sillimanite 总被引：1，自引：0，他引：1
Eric T. Goergen Donna L. Whitney Mark E. Zimmerman Takehiko Hiraga 《Tectonophysics》2008,454(1-4):23-35
Torsion experiments were performed on the Al2SiO5 polymorphs in the sillimanite stability field to determine basic rheological characteristics and the effect of deformation on polymorphic transformation. The experiments resulted in extensive transformation of andalusite and kyanite to sillimanite. No transformation occurred during the hot-press (no deformation) stage of sample preparation, which was carried out at similar P–T conditions and duration as the torsion experiments. Experiments were conducted on fine-grained (< 15 µm) aggregates of natural andalusite, kyanite and sillimanite at 1250 °C, 300 MPa, and a constant shear strain rate of 2 × 10− 4/s to a maximum shear strain of 400%. Electron back-scattered diffraction (EBSD) analysis of the experiments revealed development of lattice-preferred orientations, with alignment of sillimanite and andalusite [001] slightly oblique to the shear plane. The kyanite experiment could not be analyzed using EBSD because of near complete transformation to sillimanite. Very little strain ( 30%) is required to produce widespread transformation in kyanite and andalusite. Polymorphic transformation in andalusite and kyanite experiments occurred primarily along 500 µm wide shear bands oriented slightly oblique and antithetic to the shear plane and dominated by sub-µm (100–150 nm) fibrolitic sillimanite. Shear bands are observed across the entire strain field preserved in the torsion samples. Scanning transmission electron microscope imaging shows evidence for transformation away from shear bands; e.g. fibrolitic rims on relict andalusite or kyanite. Relict grains typically have an asymmetry that is consistent with shear direction. These experimental results show that sillimanite is by far the weakest of the polymorphs, but no distinction can yet be made on the relative strengths of kyanite and andalusite. These observations also suggest that attaining high bulk strain energy in strong materials such as the Al2SiO5 polymorphs is not necessary for triggering transformation. Strain energy is concentrated along grain boundaries, and transformation occurs by a dynamic recrystallization type process. These experiments also illustrate the importance of grain-size sensitive creep at high strains in a system with simultaneous reaction and deformation. 相似文献
13.
电感耦合等离子体发射光谱法同时测定钒钛磁铁矿中钒钛钴镍 总被引：1，自引：0，他引：1
钒钛磁铁矿样品经过氧化钠熔融,盐酸提取,溶液分取稀释后用电感耦合等离子体发射光谱法同时测定其中的V2O5、TiO2、Co、Ni。实验确定过氧化钠的用量为1.5 g,盐酸的用量为10 mL,选择干扰元素较少和背景干扰较小的V、Ti、Co、Ni分析谱线分别为292.4 nm、334.9 nm、230.7 nm、231.6 nm,在稀释因子为10(总稀释因子5000)的条件下进行分析,方法检出限为0.05～0.17μg/g。用国家一级钒钛磁铁矿标准物质GBW 07225(原矿)、钒钛磁铁矿标准物质GBW 07226a(精矿)、钒钛磁铁矿标准物质GBW 07227(尾矿)验证方法精密度和准确度,方法精密度(RSD,n=12)为0.41%～1.91%;除含量较低的Ni和Co外,相对误差(RE,n=4)均小于5%。通过安装氩气加湿器有效地解决了盐分较大带来的影响,在标准系列中加入等量空白溶液,保持基体与试样一致,消除了基体效应。方法分解样品彻底完全,分析流程简单,易于掌握,一次熔样可以同时测定多种元素,可适用于大批量样品分析。 相似文献
14.
EH pH diagrams have been calculated using the PHREEQC programme in order to establish the predominance fields of Mn, Fe, Co, Ni, Cu and As in bottom waters from the Angola Basin. Predominance fields are presented separately for both aquatic species and solid mineral phases in order to simplify interpretation of the data. The diagrams show significant differences from standard EH pH diagrams for these elements calculated for freshwater at 25 °C and 1 bar which assume an element concentration of 10-6 M. In particular, our diagrams show that Mn2+ and NiCO
3
0
are the predominant aquatic species for Mn and Ni in bottom seawater and FeOOH, Fe2O3, Fe3O4, CoFe2O4, CuFe2O4, CuFeO2, and Ba3 (AsO4)2 the predominant solid phases for Fe, Co, Cu and As, respectively. Mn and Ni are therefore undersaturated and Fe, Co, Cu and As supersaturated in bottom seawater from the Angola Basin. Neither rhodochrosite (MnCO3) nor siderite (FeCO3) can form in this marine environment in equilibrium with seawater. A mixed Mn-Ca carbonate is therefore formed within the pore waters of reducing sediments. The high Ni/Cu ratios in cobalt-rich manganese crusts formed adjacent to the oxygen minimum zone may be explained by the change from Cu2+ to CuCl
3
2-
as the dominant aquatic species of Cu in seawater at an EH of +0.48 V. 相似文献
15.
Maurizio Bucca Martin Dietzel Jianwu Tang Albrecht Leis Stephan Jürgen Khler 《Chemical Geology》2009,266(3-4):152-165
Otavite, witherite, calcite, strontianite, hydrozincite and hydrocerussite nucleation was induced by CO2 diffusion through a polyethylene membrane into a metal bearing solution. Nucleation and ongoing precipitation was followed at 25 ± 1 °C by the chemical evolution of the solution and the consumption of sodium hydroxide (pH-stat conditions). X-ray diffraction patterns as well as FT-infrared and Raman spectra confirmed the formation of well crystallized solids, except for less crystalline hydrozincite. In several experiments simonkolleite and laurionite precipitated concurrently with hydrozincite and hydrocerussite. The carbonate end-member minerals, smithsonite and cerussite, however were not formed. Carbonate minerals crystallized as spherical aggregates of thin layered otavite, spherical orientated witherite needles, rhombohedral calcite, pseudo-hexagonal strontianite laths, fibrous lumps of hydrozincite and planar hexagonal hydrocerussite crystals. Crystal and aggregate sizes range between 1 and 100 μm. Nucleation occurred at well defined reaction times and distinct critical supersaturation indices (SIcrit). The time for nucleation at constant pH decreased as the initial metal concentration increased for a given solid. The SIcrit values decreased in the order of hydrocerussite (3.2), otavite (2.5), strontianite (1.6), witherite (0.9) and calcite (0.7). 相似文献
16.
F. Masoudi B. Mehrabi M. Rezai Aghdam B. W. D. Yardley 《Journal of the Geological Society of India》2009,73(3):407-418
In the Sanandaj-Sirjan zone of metamorphic belt of Iran, the area south of Hamadan city comprises of metamorphic rocks, granitic
batholith with pegmatites and quartz veins. Alvand batholith is emplaced into metasediments of early Mesozoic age. Fluid inclusions
have been studied using microthermometry to evaluate the source of fluids from which quartz veins and pegmatites formed to
investigate the possible relation between host rocks of pegmatites and the fluid inclusion types. Host minerals of fluid inclusions
in pegmatites are quartz, andalusite and tourmaline. Fluid inclusions can be classified into four types. Type 1 inclusions
are high salinity aqueous fluids (NaCleq >12 wt%). Type 2 inclusions are low to moderate salinity (NaCleq <12 wt%) aqueous fluids. Type 3 and 4 inclusions are carbonic and mixed CO2-H2O fluid inclusions. The distribution of fluid inclusions indicate that type 1 and type 2 inclusions are present in the pegmatites
and quartz veins respectively in the Alvand batholith. This would imply that aqueous magmatic fluids with no detectable CO2 were present during the crystallization of these pegmatites and quartz veins. Types 3 and 4 inclusions are common in quartz
veins and pegmatites in metamorphic rocks and are more abundant in the hornfelses. The distribution of the different types
of fluid inclusions suggests that CO2 fluids generated during metamorphism and metamorphic fluids might also contribute to the formation of quartz veins and pegmatites
in metamorphic terrains. 相似文献
17.
高锰酸盐指数(CODMn)、硝酸根(NO-3)、铵根(NH+4)是判断水体是否受到三氮污染的重要指标。对于测定这三个指标的水样保存方式和时间,地质行业标准和国内外主要国家标准间存在明显差异。地质行业标准规定地下水样品原水室温保存,CODMn和NH+4在3天内测定;NO-3在20天内测定;国家标准和美国标准推荐样品硫酸酸化,避光或冷藏保存,在2~7天内完成CODMn和NO-3和1~7天内完成NH+4测试。为了分析各类标准在样品保存要求上的差异对检测结果的影响,确保检测数据能真实地反映水体污染状况,找寻简便的保存方式,本文在广州地区采集地下水,按照地质行业标准与国家标准进行处理和保存,并在不同时间段对三个指标进行测试。分析验证结果表明:地质行业标准与国家和美国标准关于水样的保存方法均非常可靠。地质行业标准主要针对静态地下水,保存方法相对宽松;国家标准和美国标准适用范围除了地下水,还包括动态的地表水和废水,采样对象成分更为复杂,更不稳定,更容易受外界影响发生变化,故保存条件高于地质标准。在广州地区,采用原水室温避光保存水样,CODMn、NH+4保存时间可为5天,NO-3保存时间可为30天;采用酸化水室温保存水样,CODMn、NO-3和NH+4保存时间可长达30天。这两种方式均比地质行业标准和国家标准推荐的有效时间长,且原水和酸化水室温保存方式相对于冷藏保存方式更为方便。本文提出,如果采集的水样能方便、快速送达实验室,可采用原水保存;如果不能在短时间内送达实验室检测,可采用硫酸酸化保存。 相似文献
18.
Giancarlo Della Ventura Fabio Bellatreccia Paolo Rossi 《Physics and Chemistry of Minerals》2007,34(10):727-731
We report here a single-crystal polarized-light study of stoppaniite, ideally (Fe,Al,Mg)4(Be6Si12O36)(H2O)2(Na,□), from Capranica (Viterbo). Polarized-light FTIR spectra were collected on an oriented (hk0) section, doubly polished
to 15 μm. The spectrum shows two main bands at 3,660 and 3,595 cm−1; the former is strongly polarized for E ⊥c, while the latter is polarized for E //c. A sharp and very intense band at 1,620 cm−1, plus minor features at 4,000 and 3,228 cm−1 are also polarized for E //c. On the basis of literature data and considering the pleochroic behavior of the absorptions, the 3,660 cm−1 band is assigned to the ν3 stretching mode and the 1,620 cm−1 (associated with an overtone 2*ν2 at 3,230 cm−1) band to the ν2 bending mode of “type II” water molecules within the structural channels of the studied beryl. The sharp band at 3,595 cm−1 is not associated with a corresponding ν2 bending mode; thus it is assigned to the stretching vibration of O–H groups in the sample. The minor 4,000 cm−1 feature can be assigned to the combination of the O–H bond parallel to c with a low-frequency metal-oxygen mode such as the Na–O stretching mode. The present results suggest that the interpretation
of the FTIR spectrum of Na-rich beryl needs to be carefully reconsidered. 相似文献
19.
Baghdadite from Fuka, Okayama Prefecture, Japan shows a bright yellow fluorescence under UV (Hg 253.7 nm) excitation. The photoluminescence (PL) spectrum at 300 K consists of one large band near 580 nm and two small UV bands at 318 and 397 nm. The optical excitation spectrum of the bright yellow fluorescence consists of two bands near 220 and 250 nm. The temperature dependence of the PL intensity exhibits linear thermal quenching. To reveal the origin of the bright yellow fluorescence from baghdadite, powder Ca3(Zr,Ti)Si2O9 crystals are synthesized. Synthetic Ca3(Zr,Ti)Si2O9 shows luminescence spectra similar to those of baghdadite, and the intensity of the yellow fluorescence is markedly increased by titanium addition. The origin of the bright yellow fluorescence from baghdadite is ascribed to the existence of titanium. 相似文献
20.
The high-pressure behavior of a vanadinite (Pb10(VO4)6Cl2, a = b = 10.3254(5), c = 7.3450(4) Å, space group P63/m), a natural microporous mineral, has been investigated using in-situ HP-synchrotron X-ray powder diffraction up to 7.67 GPa with a diamond anvil cell under hydrostatic conditions. No phase transition has been observed within the pressure range investigated. Axial and volume isothermal Equations of State (EoS) of vanadinite were determined. Fitting the P–V data with a third-order Birch-Murnaghan (BM) EoS, using the data weighted by the uncertainties in P and V, we obtained: V 0 = 681(1) Å3, K 0 = 41(5) GPa, and K′ = 12.5(2.5). The evolution of the lattice constants with P shows a strong anisotropic compression pattern. The axial bulk moduli were calculated with a third-order “linearized” BM-EoS. The EoS parameters are: a 0 = 10.3302(2) Å, K 0(a) = 35(2) GPa and K′(a) = 10(1) for the a-axis; c 0 = 7.3520(3) Å, K 0(c) = 98(4) GPa, and K′(c) = 9(2) for the c-axis (K 0(a):K 0(c) = 1:2.80). Axial and volume Eulerian-finite strain (fe) at different normalized stress (Fe) were calculated. The weighted linear regression through the data points yields the following intercept values: Fe a (0) = 35(2) GPa for the a-axis, Fe c (0) = 98(4) GPa for the c-axis and Fe V (0) = 45(2) GPa for the unit-cell volume. The slope of the regression lines gives rise to K′ values of 10(1) for the a-axis, 9(2) for the c-axis and 11(1) for the unit cell-volume. A comparison between the HP-elastic response of vanadinite and the iso-structural apatite is carried out. The possible reasons of the elastic anisotropy are discussed. 相似文献