面极化和体极化球体上复视极化率的频谱特征及其理论计算的某些结果

用面极化的等效电阻率ρ₀^*=ρ₀+(λω)/aρ₁经验公式λ(ω)=λ₀β/β+iω和组合电阻率ρ₂=ρ¹1-V/1+2V(当ρ₂→0时)公式,代入已有的基本理论公式,分别导出了有关面极化和体极化球体的η_s(ω)公式,使两者通过λ(ω)建立了基本联系。根据推出的公式进行了理论计算,获得了某些有意义的结果。     

频谱激电法在几个金属矿区的应用效果

通过野外实例说明激电谱的视时间常数(τ_s)的稀释作用小,岩矿的时间常数差异大有可能发现为激电强度参数(η_sρ_sm_s或ψ_s)所不能发现的深部矿(或矿化)体的异常.以τ_s参数为主,综合激电谱的其它参数,有可能对浅源激电异常性质进行区分.     

极化水平层上天然场源激电测深的理论研究

采用Dias模型表征介质的激电效应,对三层水平地层中间层为极化层的天然电磁场源激电测深之视电阻率及阻抗相位进行了理论计算.利用中间层充电率m₂≠0和m₂=0时相同频率的视电阻率振幅比和阻抗相位差作为提取激电效应的参数,重点讨论了不同电阻率断面类型对激电测深异常的影响.最后,给出了在一个已知铅锌矿上的试验结果.     

吉林南部辉南-靖宇地区岩石圈地幔氧化-还原状态及研究意义

吉林省南部辉南-靖宇地区第四纪碱性玄武岩中的地幔包体主要为尖晶石相二辉橄榄岩和方辉橄榄岩。二辉橄榄岩和方辉橄榄岩的平衡温度分别为770~1000℃和850~1025℃,对应的氧逸度 (f_O2)值分别为FMQ -0.70至+0.34 (均值为FMQ -0.06) 和FMQ -0.46至+0.05 (均值为FMQ -0.15),它们与深海橄榄岩(abyssal peridotites)以及软流圈地幔的f_O2相似。橄榄岩的f_O2值,连同其全岩化学成分(如Mg^#、Al₂O₃、CaO、Ni、Co和Cr)和矿物化学成分(如橄榄石的Fo、尖晶石的Cr^#和Mg^#,以及辉石的Mg^#)特征,表明辉南-靖宇地区龙岗火山群下面的岩石圈地幔很可能是在晚中生代以来,伴随着华北克拉通和扬子板块的碰撞以及来自东侧太平洋板块和北侧蒙古-额霍次克(Mongolo-Okhotsk)板块分别向西和向南的俯冲叠加,原来的古老岩石圈失衡、塌陷(拆沉？),取而代之的深部软流圈底辟、上涌,又经历了低度部分熔融的产物。     

用激电时间谱视参数评价激电异常的应用效果

在四个已知区利用时谱激电法,反演求取Cole-Cole模型视参数,综合考虑η_s、τ_ss     

电法测定水文地质参数的尝试

1. 含水层导水系数(T)的确定在相同条件下,含水层厚度大,视横向电阻(R_t)大,颗粒粗Rt也大,公式R_t＝P₂·H₂;含水层导水系数(T)也取决于含水层厚度和结构,即T=K·h.可见T与R_t存在着正相关关系.这样求取了T-R_t相关曲线,其导水系数便可求出.解释野外所做的电测深曲线确定出R_t;利用7个已知抽水孔的资料确定含水层导水系数;将计算出的T值与R_t值对比,分别建立Q₃砂卵石层和Q₂泥质卵石层中T-R_t相关曲线(直线).经计算,Q₃层中T－Rt相关系数γ=0.964(Q₂层略),证明相关曲线可靠.依据T=R_t相关关系绘制了“导水系数分布图”,计算出Q₃层的渗透系数(K)值80-120m/d,R_t/T值2.13-2.68,Q₂层的K值40-50m/d,R_t/T 值5-8.2.含水层有效孔隙度(ψ)的求取利用阿尔奇公式ρ=ψ^-mS^-nρ_w求取.野外采用电测深法.先求出11个已知孔含水层电阻率(ρ_s);野外采水样,室内分析,依据16℃时地层水(ρ_w)与矿化度(C)关系图确定各孔ρ_w;取m=1.5,利用上述公式求出各孔ψ值.Q₃层 值0.1769-0.3444,多数0.2-0.25.此值与室内试验得出的值0.25一致,与重力给水度经验值0.23-0.26相近.     

K-H3OFe3(SO4)2(OH)6铁矾的XRD研究

根据X射线衍射(XRD)分析发现: A Fe₃(SO₄)₂(OH)₆(A=K⁺、H₃O⁺)系列铁钒的XRD数据十分相近,难以用XRD区别,需通过能谱(EDS)辅助分析,才能区分此类铁矾。另外,此类铁矾的003和107面网间距d随K⁺含量增大而增大,且呈一元三次方程的关系;而033和220面网间距d随K⁺含量增大而减小,呈一元二次方程的关系。对该现象从铁矾晶体结构方面进行解释:K⁺、H₃O⁺离子位于较大空隙中,且沿着Z轴方向排列,当K⁺、H₃O⁺离子之间相互替换时,会导致该铁矾晶体结构在Z轴方向有较明显的变化。     

拉萨地块中北部晚白垩世(约90Ma)拔拉扎含矿斑岩地球化学特征及其成因

拉萨地块中北部形成于90~88Ma的拔拉扎含矿斑岩具有明显的埃达克质岩特征:高SiO₂(>69%)、Al₂O₃(平均为15.89%)、Sr (平均为354×10^-6),低Y(平均为12.97×10^-6)、Yb(平均为0.95×10^-6)含量,轻重稀土强烈分异((La/Yb)_N平均为19.8);同时它们有着高Mg^#(平均为65)、Cr(平均为107×10^-6)、Ni(平均为13×10^-6)含量。研究区这些具有埃达克质岩特征的含矿斑岩并非源于俯冲洋壳、底侵或加厚下地壳部分熔融的产物,也不是玄武质岩浆结晶分异的产物,而很可能是拆沉下地壳部分熔融的结果。另一方面,南向俯冲的Slainajap洋壳或班公湖-怒江洋壳的断离也可能诱发板片窗上部的壳幔物质发生部分熔融而形成研究区的含矿斑岩。     

利用电测深曲线极大值计算水文地质参数的探讨

利用电测深成果(含水层电阻率或地层因素)估算含水层渗透系数的问题,前人已做了很多工作^[1,2].作者针对安阳市安阳河北水源地电测深资料的解释和水文地质勘察成果,提出采用电测深K型曲线极大值计算水文地质参数的方法,建立了ρ_{s max}～K之间的4种回归分析模型.结果表明,K与ρ_{s max}存在对数相关关系.经计算的成果图件(K、T等值线图)对评价该区水文地质条件,估算单井涌水量及水井位置选择等都具有十分重要的实用价值.     

对下庄矿田沥青铀矿形成机理的认识

本文在分析下庄矿田成矿地质背景的基础上,对该矿田成矿热水溶液中铀的存在形式、铀酰络合物的氧化还原临界电位值和水-铀比电位值进行了计算。计算结果表明,成矿热液中,铀的迁移形式为UO₂(CO₃)₂^2-、UO₂F^3-和UO₂F₄^2-,其Ehcu和Ehw,u值分别为-0.18 ~0.46 V和-0.44~ -0.5 eV。CO₂和F^-, 是铀成矿的主要矿化剂。沥青铀矿是在地壳处于拉张环境,水-铀比电位值小于零的条件下形成的。     

Solubility and complexing of Ni in the system NiO-H2O-HCl

The solubility of bunsenite (NiO) in Cl-bearing fluids in the range of 450°–700°C, 1–2 kbar was determined using the Ag + AgCl acid buffer technique. Based on the results of the experiments, it is concluded that the associated NiCl⁰₂ complex is the dominant Ni species in the fluid over the entire temperature-pressure range investigated. The temperature dependence of the equilibrium constant for the reaction NiO(s) + 2HCl⁰(aq) = NiCl⁰₂(aq) + H₂O is given by logK = ?4.17(±0.55) + 4629(±464)/T(K) at 1 kbar, and logK = ?4.75(±0.91) + 5933(±756)/T(K) at 2 kbar. The calculated difference in standard state Gibbs free energy of formation between NiCl⁰₂ and 2HCl⁰ in kcal is G⁰(NiCl⁰₂) ? 2G⁰(HCl⁰) = ?20.77(±2.22) + 0.03264(±0.0026)T(K), at 1 kbar and G⁰(NiCl⁰₂) ? 2G⁰(HCl⁰) = ?25.01(±1.35) + 0.03264(±0.0016)T(K) at 2 kbar. Comparison of the solubilities of Ni end-member minerals with those of Ca, Mn, Fe, and Mg indicates that nickel minerals generally are the least soluble at a given temperature and pressure. The relatively low solubility of Ni end-member minerals, combined with the relatively low concentration of Ni in most rocks, should result in a quite low mobility of Ni in hydrothermal fluids.     

The stability of transition metal dolomites in carbonate systems: a discussion

The instability of transition metal dolomites [CaR²⁺(CO₃)₂ where R²⁺ is Fe, Co, Ni, Cu, or Zn] and the limited substitution of transition metal cations for Mg in the dolomite structure can be accounted for by the effect of octahedral distortion. For example, trigonal elongation of the Fe octahedron, due to the Jahn-Teller effect, observed in siderite and ankerite, results in elongation of the Ca octahedron which is sensitive to distortion because the radius of Ca²⁺ is close to the upper limit for octahedral coordination. Co, Ni, Cu, Zn octahedra are also thought to be deformed, relative to Mg octahedra, in carbonates.The free energy of formation (ΔG^o_f) of R²⁺CO₃ becomes more positive with increasing octahedral distortion. Estimated ΔG^o_f(dolomite) as well as stabilities and solubility limits of R²⁺ in natural and synthetic dolomites suggest a series in order of decreasing stability: Mg >Mn >Zn >Fe >Co >Ni >Cu.ΔG^o_f(est.) for the terminal Fe-dolomite solid solution [72 mol% CaFe(CO₃)₂] in the system CaCO₃-MgCO₃-FeCO₃ may represent an empirical threshold value for dolomite stability which lies between ΔG^o_f for Mn- and Zn-dolomites. While Zn-dolomite is probably not a stable phase, very extensive solid solution toward CaZn(CO₃)₂ is to be expected in the system CaCO₃-MgCO₃-ZnCO₃. The tendency for transition metal dolomites to contain excess CaCO₃ can also be accounted for in terms of octahedral distortion and AG^o_f.     

A molecular orbital study of bond length and angle variations in framework structures

Molecular orbital calculations on a variety of silicate and aluminosilicate molecules have been used to explore the bonding forces that govern tetrahedral bond length variations, r(TO), in framework silicates and aluminosilicates. Not only do the calculations provide insight into the variety of structural types and the substitution limits of one tetrahedral atom for another, but they also provide an understanding of the interrelationships among r(TO) and linkage factors, bond strength sum, coordination number, and angles within and between tetrahedra. A study of these interrelationships for a theoretical data set shows that r(SiO) and r(AlO) are linearly correlated with (1) p _o, the bond strength sum to a bridging oxygen, (2) f _s(O), the fractional s-character of a bridging oxygen, and (3) f _s (T), the fractional s-character of the T atom. In a multiple linear regression analysis of the data, 92% of the variation of r(SiO) and 99% of the variation of r(AlO) can be explained in terms of a linear dependence on p _o, f _s (O), and f _s (T). Analogous regression analyses completed for observed r(Al, SiO) bond length data from a number of silica polymorphs and ordered aluminosilicates account for more than 75% of the bond length variation. The lower percentage of bond length variation explained is ascribed in part to the random and systematic errors in the experimental data which have a negligible effect on the theoretical data. The modeling of more than 75% of the variation of r(Al, SiO) in the framework silicates using the same model used for silicate and aluminosilicate molecules strengthens the viewpoint that the bonding forces that govern the shapes of such molecules are quite similar to the forces that govern the shapes of chemically similar groups in solids. The different regression coefficients calculated for f _s (T) indicate that SiO and AlO bond length variations in framework structures should not be treated as a single population in estimating the average Al, Si content of a tetrahedral site.     

Frequency dependence of equatorial ionospheric scintillations

Simultaneous observations of amplitude scintillations at 40 MHz, 140 MHz and 360 MHz radiated from ATS-6 satellite at 34° E longitude were made at Ootacamund near the magnetic equator in India. It has been found that the frequency variation of scintillation index (S ₄) isS ₄ ∞f ^?n , withn being about 1·2 only for weak scintillations, i.e., so long as the scintillation index does not exceed 0·6 at the lower frequency. For strong scintillations (S ₄>0·6) where multiple scattering may be present, the exponentn itself is a function of the intensity of scintillation, the scintillation indices at two frequencies are related by:S ₄(f ₁)=S ₄(f ₂) exp [1·3 log(f ₂/f ₁)(1?S ₄(f ₂)] so long asf ₂/f ₁≤3. Thus knowing scintillation index at a given frequency one can estimate the scintillation index at another frequency. This will be of significant importance for communication problems. Evidence is also shown for the reversal of the frequency law in cases of intense scintillations.     

Source parameters and scaling relations for small earthquakes in the Kachchh region of Gujarat,India

The scaling relationships for stress drop and corner frequency with respect to magnitude have been worked out using 159 accelerograms from 34 small earthquakes (M _w 3.3–4.9) in the Kachchh region of Gujarat. The 318 spectra of P and S waves have been analyzed for this purpose. The average ratio of P- to S-wave corner frequency is found to be 1.19 suggestive of higher corner frequency for P wave as compared to that for S wave. The seismic moments estimated from P waves, M ₀(P), range from 1.98 × 10¹⁴ N m to 1.60 × 10¹⁶ N m and those from S waves, M ₀(S), range from 1.02 × 10¹⁴ N m to 3.4 × 10¹⁶ N m with an average ratio, M ₀(P)/M ₀(S), of 1.11. The total seismic energy varies from 1.83 × 10¹⁰ J to 2.84 × 10¹³ J. The estimated stress drop values do not depend on earthquake size significantly and lie in the range 30–120 bars for most of the events. A linear regression analysis between the estimated seismic moment (M ₀) and corner frequency (f _c) gives the scaling relation M ₀ f _c ³  = 7.6 × 10¹⁶ N m/s³. The proposed scaling laws are found to be consistent with similar scaling relations obtained in other seismically active regions of the world. Such an investigation should prove useful in seismic hazard and risk-related studies of the region. The relations developed in this study may be useful for the seismic hazard studies in the region.     

Advances of ferrous and ferric Mössbauer recoilless fractions in minerals and glasses

Mössbauer spectroscopy has been used widely to characterize the ferric (Fe³⁺) and ferrous (Fe²⁺) proportions and coordination of solid materials. To obtain these accurately, the recoilless fraction is indispensible. The recoilless fractions (f) of iron-bearing minerals, including oxides, oxyhydroxides, silicates, carbonates, phosphates and dichalcogenides, and silicate glasses were evaluated from the temperature dependence of their center shifts or absorption area with the Debye model approximation. Generally, the resolved Debye temperature (θ_D) of ferric iron in minerals, except dichalcogenides, through their center shifts ranging from 400 to 550 K, is significantly larger than ferrous iron ranging from 300 to 400 K, which is consistent with the conclusion from previous work. The resolved f (Fe³⁺)_RT with the center shift model (CSM) ranges from 0.825 to 0.925, which is larger than that obtained for f(Fe²⁺)_RT, which ranges from 0.675 to 0.750. Meanwhile, the θ_D and f resolved from temperature-dependence of absorption are generally lower than from center shifts, especially for ferric iron. The significant difference between f(Fe³⁺) and f(Fe²⁺) indicates the necessity of recoilless fraction correction on the Fe³⁺/(Fe³⁺+Fe²⁺) resolved from Mössbauer spectra.     

Uranium(VI) in aqueous solutions at 25°C and a pressure of 1 bar: Insight from experiments and calculations

The behavior of the 0.1 mNaCl + 0.002 mHCl + 1.9 × 10^?5 mUO₂(NO₃)₂ solution was studied at pH from 2.7 to 11.0, 25°C, and 1 bar in an argon atmosphere. The curve of variations in U concentration exhibits two minima at pH = 6.6 ± 0.7 and 10.0 ± 0.5. These minima are related to the precipitation of schoepite and clarkeite, respectively. The experimental data were used to refine the stability constants of U(VI) (hydroxo) complexes. For the polymer species of U(VI) with charges from +2 to ?1, the method of additivity of thermochemical increments was used, and increments of the linear relation were determined for the calculation of the Gibbs free energies of formation (Δ_fG _298.15 ⁰ ) of respective homologue series. The proposed method was applied to calculate the Δ_fG _298.15 ⁰ of formation of U(VI) (hydroxo)complexes containing from one to five uranium atoms.     

The spectra of hard radiation from radio pulsars

The kinetic equation for the distribution function of relativistic electrons is solved taking into account quasi-linear interactions with waves and radiative processes. Mean values of the pitch angles ψ are calculated. If the particles of the primary beam with Lorentz factors γ_b～10⁶ are resonant, then the condition γ_bψ_b?1 is satisfied, the particle distribution is described by the function f _‖(γ) ∝ γ^?4, and the synchrotron radiation spectrum is characterized by the spectral index α=3/2. On the other hand, if a cyclotron resonance is associated with particles of the high-energy tail of the secondary plasma (γ_t～10⁵), then γ_tψ_t?1, and the distribution function has two parts—f _‖(γ) ∝ γ and f _‖(γ) ∝ γ^?2—which correspond to the spectral indices α₁=+1 and α₂=?0.5. This behavior is similar to that observed for the pulsar B0656+14. The predicted frequency of the maximum ν_m=7.5×10¹⁶ Hz coincides with the peak frequency for this pulsar. The model estimate for the total synchrotron luminosity of a typical radio pulsar with hard radiation L _s =3×10³³ erg/s is in agreement with observed values.     

Shear wave attenuation characteristics over the Central India Tectonic Zone and its surroundings

The study area lies between latitude 18–26°N and longitude 73–83°E, and mainly covers the Central India Tectonic Zone (CITZ). The frequency-dependent shear wave quality factor (Q_s) has been estimated over the CITZ and its surroundings using Double Spectral Ratio (DSR) method. We have considered 25 local earthquakes with magnitude (M_L) varies from 3.0 to 4.7 recorded at 11 stations running under national seismic network. The Fast Fourier Transformed (FFT) spectra were computed from the recorded waveform having time-window from onset of S-phase to 1.0 s and for a frequency-band of 0.1–10 Hz. Three different shear wave velocities (i.e., 3.87, 3.39 and 3.96 km/s) were obtained over the study area based on a pair of earthquakes recorded at a pair of stations. The low Q_s values of 51–96 at 1 Hz (i.e., Q_s = 51f^0.49; Q_s = 90f^0.488 and Q_s = 96f^0.53) were found in the area covering the Son–Narmada–Tapti (SONATA) lineament, CITZ, eastern part of the Satpura fold belt, Vindhyan and Gondwana basins, Godavari and Mahanadi grabens, and southern part of Gangetic plain. Intermediate Q_s values of the order of 204–277 (i.e., Q_s = 204f^0.56 and Q_s = 277f^0.55) were noted in the cartonic areas, namely, Bundelkhand, Dharwar-Bhandara and Bastar. While the higher Q_s values of 391–628 at 1 Hz (i.e., Q_s = 391f^0.49, Q_s = 409f^0.48, Q_s = 417f^0.48, Q_s = 500f^0.66, Q_s = 585f^0.65 and Q_s = 628f^0.69) were found in the eastern part of the SONATA, CITZ, and the northeastern part of the Satpura fold belt. The low Q_s values might be attributing to the more heterogeneous SONATA rift system. Low Q_s values further may presumably be associated with lower-level of seismicity and apparently account for higher tectonic stress accumulation over long duration. The long-term accumulated stress is generally released through occasional triggering of moderate magnitude earthquakes in the SONATA zone. Surrounding the SONATA region, the higher Q_s values possibly accounts for a more homogeneous subsurface structure along the SONATA zone.