几个天然镁铝榴石的穆斯堡尔效应的研究

穆斯堡尔效应是一种无反冲的核γ射线的共振吸收现象,它是1958年由穆斯堡尔(R.L.M(?)ssbauer)发现的。由于穆斯堡尔效应产生的γ射线共振吸收谱线的能量宽度接近原子核能级的自然线宽,以及无反冲γ射线共振吸收(或散射)对γ射线能量变化十分灵敏,因此,可以把共振吸收的原子核当做灵敏的探针,测量固体中有关的原子核与核所在位置上固体的化学环境间的超精细相互作用。近些年来,穆斯堡尔效应已广泛应用于物理学、化学、生物学及矿物学的研究中来,穆斯堡尔谱仪已成为这些学科的重要研究工具之一。     

攀西地区某些花岗岩体中云母的穆斯堡尔效应研究

一、引言穆斯堡尔光谱学做为一种研究矿物的新方法,已经广泛地用在矿物学的研究中(应育浦和李哲,1977)。可以使用铁的穆斯堡尔效应来确定矿物中铁的价态、配位数、阳离子铁的分布,即有序和无序等。迄今已对几乎所有的含铁矿物进行过穆斯堡尔测试和研究。云母是一种重要的层状硅酸盐类矿物,它是花岗岩中的主要造岩矿物之一。近年来云母类矿物的穆斯堡尔效应研究已相当广泛,尤其对黑云母研究较多。本文收集了四川攀西地区某些不同地点,不同花岗岩体中十二个黑云母和二个白云母样品进行了化学分析和穆斯堡尔效应研究,以探讨黑云母、白云母中     

高铁铁橄榄石穆斯堡尔效应的研究

穆斯堡尔效应是一种无反冲核的γ射线共振吸收现象。由于穆斯堡尔效应产生的γ射线共振吸收谱线宽度接近原子核能级的自然线宽,以及无反冲γ射线共振吸收对γ射线能量变化十分灵敏,因此可以用它来测定固体中有关原子核与核所在位置上固体化学环境之间的超精细相互作用。近十年来,穆斯堡尔效应已广泛应用于矿物学的研究,其中,研究最多的是~(57)Fe穆斯堡尔效应,迄今为止,已经对许多重要的造岩矿物进行过测定,穆斯堡尔效应已经日益成为研究矿物的重要方法。     

硅酸盐玻璃中铁的性质研究以及对行星岩浆海氧化还原环境的影响

<正>铁是硅酸盐熔体中最重要的变价元素,对岩浆的物理和化学性质起着重要作用。三价铁和总铁的比例(Fe~(3+)/ΣFe)反映了岩浆过程中的氧化还原状态。Fe3+/ΣFe不仅直接受氧逸度控制,而且还受化学成分、温度和压力的影响。本研究通过实验岩石学的方法探讨硅酸盐熔体中铁的结构变化以及Fe3+/ΣFe与压力之间的关系,进而对早期岩浆海的氧化还原环境进行模拟,从而对早期大气的组成进行制约。Fe3+/ΣFe比值可以通过穆斯堡尔谱以及X-射线吸收近边结构(XANES)进行测量,其中穆斯堡尔     

碱性玄武岩中的某些巨晶单斜辉石──Ⅱ:穆斯堡尔谱──兼论单斜辉石的异常穆斯堡尔谱和铁结构态的测定

本文对辽宁宽甸碱性玄武岩中巨晶单斜辉石进行穆斯堡尔谱研究。应用晶体结构研究结果较合理地解释了单斜辉石的异常穆斯堡尔谱。结合XRD讨论了单斜辉石中Fe结构态的测定以及穆斯堡尔谱的可应用性。巨晶应结晶于相当氧化的环境。     

碱性玄武岩中的某些巨晶单斜辉石Ⅱ：穆斯堡尔谱——兼论单斜辉石的异…

本文对辽宁宽甸碱性玄武岩中巨晶单斜辉石进行穆斯堡尔谱研究，应用晶体结构研究结果较合理地解释了单斜辉石的异常穆斯堡尔谱，结合ＸＲＤ讨论了单斜辉石中Ｆｅ结构态的测定以及穆斯堡尔谱的可应用性，巨晶应结晶于相当氧化的环境。     

寒武纪生物爆发前的死劫难海洋

白垩纪/第三纪界线研究揭示,界线事件留下铱异常和碳同位素异常信息(Alvarez,1980;Hsü et al., 1982)。近来,二叠纪/三叠纪界线粘土中也发现了Ir-δ¹³C双异常(SunYiyin et al.,1984)。     

穆斯堡尔谱学在陨石地质学中的应用

穆斯堡尔效应的应用十分广泛,己应用于物理学、化学、生物和医学,材料科学,环境科学、矿物地质学、考古学以及工业技术等各个研究领域。对于铁来说,已经形成哪里有铁,哪里就有穆斯堡尔谱学的研究局面。1964年Sprenkel—Segel等人使用穆斯堡尔效应首先研究了石陨石,开创了穆斯堡尔谱学在陨石地质学中应用的新局面。陨石是稀有的标本,它对于研究太阳系的形成和演化,生命的起源,空间技术等方面都有重大的科学价值。由于穆斯堡尔谱学具有相当高的能量分辨率,能直接观察和研究超精细结构,因而成为陨石地质学研究中的一种重要的手段。     

布拜图对热液氧化物沉淀条件的指示

<正>无定形Fe-和Mn-羟基氧化物以及硅的沉积体广泛分布于洋中脊(Dekov et al.,2010)、弧后盆地(Hein et al.,2008;Zeng et al.,2012)和海山(Emerson et al.,2002;Edwards et al.,2011)等不同地质背景的海底热液区。热液Fe-羟基氧化物按成因可以分为三类:热液硫化物的氧化产物,直接从热液中沉淀形成的氧化物以及来自热液     

矿物穆斯堡尔谱学研究动态

穆斯堡尔效应(Mbssbauer effect)是一种无反冲的核γ射线的共振吸收现象.自六十年代初发现~(57)Fe的能量为14.4Kev的γ射线无反冲共振吸收后,在物理,化学等部门逐渐得到广泛的应用.由于铁在地壳中分布非常广泛,多数矿物都含有铁,所以六十年代中以后,Fe穆斯堡尔效应应用于矿物研究,十多年来发展很快,到现在,Fe穆斯堡尔效应已成为矿物研究的一种重要工具.新近矿物穆斯堡尔谱学研究有如下几个方面:1.用穆斯堡尔方法测定矿物中阳离子位置分布矿物中阳离子位置分布和有序—无序现象是矿物学研究的重要课题.穆斯堡尔方法,为研究矿物中Fe~(2+)—Mg~(2+)位置分布及有序—无序现象提供一种简便而有效的方法,并将     

西藏南部花岗岩及有关岩石中的电气石

我国西藏南部,特别是高喜马拉雅地区,广泛分布着第三纪电气石花岗岩。这些岩石及其有关的伟晶岩和混合岩中都富含黑色电气石,显示了明显的区域性岩相学标志。本文对由本区和以北冈底斯地区这类岩石中采集的黑色电气石样品,作了某些物理性质、化学成分和穆斯堡尔效应的研究。     

Optical absorption spectra and Fe distribution in the structures of Li-Fe micas

The paper proposes pioneering data on the polarized optical absorption spectra of Li-Fe micas: intermediate members of the siderophyllite-zinnwaldite-polylithionite and annite-protolithionite-zinnwaldite-trilithionite series with variable Fe and Li proportions and Li- and Fe-bearing muscovite (phengite). Based on the analysis of structural data, the complicated structure of the Fe²⁺ → Fe³⁺ charge transfer band in the mica structures is explained, and arguments are presented to justify the ascribing of its shortwave component (CTB-1, ν = 17200-14900 cm^?1) to charge transfer in the pair Fe²⁺(M2) → Fe³⁺(M2) and the longwave component (CTB-2, ν = 14200-13600 cm^?1) to charge transfer in the pair Fe²⁺(M1) Fe³⁺(M2). It is demonstrated that the anomalous shift of the superposition of two-component CTB toward the shortwave region, to 17000 cm^?1, results from a decrease in the length of oxygen edges between adjacent M2M2 and M1M2 tetrahedrons when Li is accommodated in the mica structure. The first data are presented on the spectrum of Fe²⁺ ions in large distorted M3(M1) tetrahedrons (OAC Fe²⁺ II) in hetero-octahedral Li micas (zinnwaldite), and the behavior of the corresponding absorption bands at 11400 and 8000 cm^?1 is determined. It is proved that characteristics of the optical spectra of Fe²⁺ ions can be used as an indicator of the structure of the octahedral layer in the mica structures. Results of the comparative analyses of spectral parameters of the Fe²⁺ → Fe³⁺ charge transfer, crystal field spectra of Fe²⁺ ions, and the crystal-chemical characteristics controlling them in micas of the polylithionite-siderophyllite series are completely consistent with the character of cation ordering in the crystal structures of these micas determined by X-ray diffraction analysis.     

Fe2+–Fe3+ ordered distribution in chromite spinels

Mossbauer measurements have been carried out on three natural chromite minerals from different locations in China over the temperature range 50 to 750 K. The experiments showed these samples to be magnesioferrochromites. The Mossbauer spectra measured could be decomposed into three doublets: two attributed to the tetrahedral T-site Fe²⁺ ions and the third to the octahedral M-site Fe³⁺ ions. Thus for the chromite spinels the results strongly supported the ordered distribution with Fe²⁺ in the T-site and Fe³⁺ in M-site.     

Optical spectroscopy study of natural Fe, Ti-bearing calcic amphiboles

Over thirty samples of natural Ti-bearing amphiboles with Ti- and Fe-contents ranging from 0.111 to 0.729 atom per formula unit (a.p.f.u.) and from 0.479 to 2.045 a.p.f.u., respectively, were studied by means of optical absorption spectroscopy and microprobe analysis. Thirteen samples were also studied by Mössbauer spectroscopy. A strong pleochroic absorption edge, causing the dark brown colours of Ti-bearing amphiboles, is attributed to ligand-metal and metal-metal charge transfer transitions involving both iron and titanium ions (O^2?→ Fe³⁺, Fe²⁺, O^2?→ Ti⁴⁺ and Fe²⁺ + Ti⁴⁺→ Fe³⁺ + Ti³⁺). A broad intense Y-polarized band ～22?000?cm^?1 (ν_1/2?≈?3700?cm^?1) in spectra of two low iron amphiboles with a relatively low Fe³⁺/Fe_total ratio, both from eclogite-like rocks in kimberlite xenoliths, was attributed to electronic Fe²⁺(M3) + Ti⁴⁺(M2)→Fe³⁺(M3)+Ti³⁺(M2) IVCT transitions. The IVCT bands of other possible ion pairs, involving Ti⁴⁺ and Fe²⁺ in M2 and M1, M4 sites, respectively, are presumed to be at higher energies, being obscured by the absorption edge.     

Spectroscopic studies on natural chloritoids

Room temperature and low temperature Mössbauer and optical absorption spectroscopic data on six natural chloritoids characterized by means of electron microprobe and X-ray powder diffraction techniques are presented. Two narrow quadrupole doublets with widths of 0.25–0.29 mm/s assigned to Fe²⁺ in a relatively large octahedral site and Fe³⁺ in a smaller octahedral site, are observed in the Mössbauer spectra. Polarized optical absorption spectra reveal three main absorption bands. A broad absorption band at 16,300 cm^?1, which is strongly polarized in E‖X and E‖Y and shows a linear increase in integral absorption with increasing [Fe²⁺] [Fe³⁺] concentration product, is assigned to a Fe²⁺+Fe³⁺→Fe³⁺+Fe²⁺ charge transfer transition. This band displays also a temperature dependence different from that of single ion d?d transitions. Two absorption bands at 10,900 cm^?1 and 8,000 cm^?1 are, on the basis of compositional dependence and energy, assigned to Fe²⁺ in the large M(1B) octahedra of the brucite-type layer in chloritoid. Combined spectroscopic evidence and structural and chemical considerations support a distribution scheme for ferrous and ferric iron which orders the Fe²⁺ ions in the M(1B) octahedra and the Fe³⁺ ions in the small M(1A) octahedral sites. Both types of octahedra are found in the brucite type layer of chloritoid.     

Identifying characteristics of charge transfer transitions in minerals

Criteria used to identify Fe²⁺-Fe³⁺ and Fe²⁺-Ti⁴⁺ intervalence charge transfer absorption bands in electronic spectra are reviewed and compared to the characteristics of unperturbed Fe²⁺ crystal field bands and those that are intensified by interaction with Fe³⁺. Band energy is the least definitive diagnostic criterion. Changes in band intensity with temperature are also of limited value. Large widths are the most reliable characteristic of charge transfer bands. New optical absorption spectra are presented for euclase, as well as 80 K spectra of rockbridgeite, babingtonite and lazulite. Comparison of optical spectra to magnetic susceptibility measurements for rockbridgeite and babingtonite provides support for recent theories regarding the effect of magnetic coupling on the variation of charge transfer intensity with temperature.     

Mixed valence of iron in minerals with cation clusters

The valence and distribution of iron in vivianite, lazulite, babingtonite, rockbridgeite, acmite, aegirine-augite, hedenbergite, and ilvaite were studied with optical and Mössbauer spectroscopy. Optically activated intervalence charge transfer between Fe²⁺ and Fe³⁺ in neighboring sites through common edges or faces is observed in all these minerals irrespective of the polymerization of the iron-oxygen polyhedra ranging from finite clusters to infinite structural units. However, a distinct decrease occurs in the energy of the corresponding optical absorption band with increasing number of Fe²⁺ and Fe³⁺ ions involved in the charge transfer process. Thermally activated electron delocalization between Fe²⁺ and Fe³⁺ occurs only if Fe²⁺ and Fe³⁺ occupy crystallographically equivalent or geometrically very similar neighboring sites which share common edges to form extended structural units such as the ribbon in ilvaite. If the Fe-O polyhedra form finite clusters of two, three, or four polyhedra (e.g., in vivianite, lazulite, and babingtonite, respectively) no thermally-activated mixed-valence states of iron are observed. In aegirine, extended regions of the M1 chain are statistically occupied by Fe²⁺ and Fe³⁺ giving rise to thermally-activated electron delocalization in addition to the intervalence band in the optical absorption spectrum. The intensity of the optical intervalence absorption has been measured in a number of systems: ? values range from 60 to 210.     

莱河矿的超结构和低温穆斯堡尔谱的对比研究

本文进行了莱河矿3C超结构和4.2K穆斯堡尔谱的对比研究。研究表明。莱河矿的非等效位置M2A+M2C,M2B,M1B,M1A和VB能够分别与Kan等(1985)测定的莱河矿穆斯堡尔谱的吸收双峰A,B,C,D和E对应,不仅解决了超结构位置和吸收双峰之间的对应,而且圆满解释了吸收双峰A:B和C:D的强度比为2:1的关系。另外,还利用莱河矿超结构的资料讨论了莱河矿的反铁磁性内部作用。     

The MgCr2O4–MgFe2O4 solid solution series: effects of octahedrally coordinated Fe3+ on T–O bond lengths

The influence on the spinel structure of Fe³⁺ → Cr substitution was studied in flux-grown synthetic single crystals of the magnesiochromite–magnesioferrite (MgCr₂O₄–MgFe₂O₄) solid solution series. Samples were analysed by single-crystal X-ray diffraction, electron microprobe analyses, optical absorption and Mössbauer spectroscopy. With the exception of iron-poor samples (3–12 mol-% MgFe₂O₄), optical absorption and Mössbauer spectra show that iron occurs almost exclusively as trivalent Fe in the present samples. A very intense and broad absorption band at ca 7,800 cm^?1 dominates the optical absorption spectra of samples with higher Fe-contents. The appearance of this band is related to a distinct structural disorder of Fe³⁺ and a development of magnetic ordering as demonstrated by Mössbauer spectra. Profound composition-related changes are observed in the Mössbauer spectra, which are magnetically unsplit in the range 2–41 mol-% magnesioferrite, but become magnetically split in the range 59–100 mol-% magnesioferrite. Structural parameters a ₀ and M–O increase with magnesioferrite content and inversion degree, while u and T–O decrease. Our study confirms the previously reported (Lavina et al. 2002) influence of Fe³⁺ at the M site on T–O bond lengths in the spinel structure.     

Distinct ruby suite at Sardapur, Orissa: A spectroscopic investigation

Orissa is an important area for gem variety of corundum deposits in India. Spectroscopic studies, such as ESR, OAS on samples from Sardapur, Orissa, were carried out to ascertain the colour cause of corundum. Electron spin resonance (ESR) spectroscopic study was carried out on the samples to detect the presence of paramagnetic ions i.e. Fe²⁺, Fe³⁺, Ti⁴⁺, Cr³⁺ and V³⁺ etc. The variable temperature experiment carried out to observe the effect of heating on peak valence state change in paramagnetic ions. Samples were cut and polished to obtain the optical absorption spectrum (OAS) to detect the colour causing transition ions/defect centres. The samples of gem variety were step heated up to 300°C for colour enhancement studies. EPMA analysis has revealed the low chromium concentration in the rubies. The varying hues of red in the corundum are due to the presence of bivalent and trivalent iron and charge transfer process along with Cr³⁺ absorption in the 550 nm region.