Characteristics of soil radon transport in different geological formations

Soil radon concentration levels in Deir Abu-Said District, Irbid, Jordan were measured for several depths using CR-39 detectors, in the summer 2004 for six geological formations, namely, Wadi umm ghudran (WG), Wadi esSir “massive” limestone, Amman silicified limestone (ASL), Al-Hisa phosphatic limestone (AHP), Muwaqqar chalky-marl (MCM), and Basalt. Using a model (Yakovleva in Ann Geophys 48(1):195–198, 2005) based on the solution of the diffusion equation in the quasi-homogenous approximation, the characteristics of radon transport were calculated. Radon flux density from the Earth’s surface, the depth Z _eq, at which the equilibrium value of soil radon concentration is reached and the convective radon flux velocity (v) for the different soils are calculated and found to be consistent with similar values presented elsewhere. Calculations indicate that the soil covering WG has a low radon risk while, on the contrary, AHP has a higher radon risk as expected, since AHP has higher content of uranium. The other formations have intermediate values. The results of the present study confirm the statement by Yakovleva (Ann Geophys 48(1):195–198, 2005) that two measurements suffice in order to estimate the characteristics of soil radon transport.     

A robust model for pore-water chemistry of clayrock

The chemistry of pore water is an important property of clayrocks being considered as host rocks for long-term storage of radioactive waste. It may be difficult, if not impossible, to obtain water samples for chemical analysis from such rocks because of their low hydraulic conductivity. This paper presents an approach for calculating the pore-water compositions of clayrocks from laboratory-measured properties of core samples, including their leachable Cl and SO₄ concentrations and analysed exchangeable cations, and from mineral and cation exchange equilibria based on the formation mineralogy. New core sampling and analysis procedures are presented that reduce or quantify side reactions such as sample oxidation (e.g. pyrite) and soluble mineral dissolution (celestite, SrSO₄) that affect measured SO₄ concentrations and exchangeable cation distributions. The model considers phase equilibria only with minerals that are observed in the formation including the principal clay phases. The model has been used to calculate the composition of mobile pore water in the Callovo-Oxfordian clayrock and validated against measurements of water chemistry made in an underground research laboratory in that formation. The model reproduces the measured, in situ pore-water composition without any estimated parameters. All required parameters can be obtained from core sample analysis. We highlight the need to consider only those mineral phases which can be shown to be in equilibrium with contacting pore water. The consequence of this is that some conceptual models available in the literature appear not to be appropriate for modelling clayrocks, particularly those considering high temperature and/or high pressure detrital phases as chemical buffers of pore water. The robustness of our model with respect to uncertainties in the log K values of clay phases is also demonstrated. Large uncertainties in log K values for clay minerals have relatively small effects on modelled pore-water compositions.     

Tabular formations in titanomagnetite

A visually homogeneous intrusive titanium magnetite is shown microscopically to consist of two phases: a) solid solution of magnetite in ulvospinel and b) solid solution of ulvospinel in magnetite; the phase ratio is about 1 : 2. On heating in air two new phases are produced in titanium magnetite, as oriented plates forming the mineral's characteristic reticulate microstructure: ilmenite and hematite. Ilmenite disappears on further heating and the end-phase becomes a solid solution of ilmenite in hematite. It is believed that natural oxidation in depths also yields to ilmenite plates in titanium magnetite, if ulvospinel is present. Oriented platelets of hematite may be similarly produced in TiO₂ -free magnetite and in magnesium ferrite, although MgO retards their development in the latter. -- V. P. Sokoloff.     

On the velocity covariance for steady flows in heterogeneous porous formations and its application to contaminants transport

We consider groundwater steady flow in a heterogeneous porous formation of random and stationary log-conductivity Y = ln K, characterized by the mean 〈Y〉, and the two point correlation function C _Y which in turn has finite, and different horizontal and vertical integral scales I and I _v , respectively. The fluid velocity V, driven by a given head drop applied at the boundary, has constant mean value U ≡ (U, 0, 0). Approximate explicit analytical expressions for transverse velocity covariances are derived. The adopted methodology follows the approach developed by Dagan and Cvetkovic (Spatial moments of kinetically sorbing plume in a heterogeneous aquifers, Water Resour. Res. 29 (1993) 4053) to obtain a similar result for the longitudinal velocity covariance. Indeed, the approximate covariances of transverse velocities are determined by requiring that they have the exact first order variances as well as zero integral scale (G. Dagan, Flow and Transport in Porous Formations (Springer, 1989)) , and provide the exact asymptotic limits of the displacement covariance of the fluid particles obtained by Russo (On the velocity covariance and transport modeling in heterogeneous anisotropic porous formations 1. Saturated flow, Water Resour. Res., 31 (1995) 129). Comparisons with numerical results show that the proposed expressions compare quite well in the early time regime, and for Ut/I >100. Since most of the applications, like assessing the effective mobility of contaminants or quantifying the potential hazards of nuclear repositories, require predictions over higher times the proposed approximate expressions provide acceptable results. The main advantage related to such expressions is that they allow obtaining closed analytical forms of spatial moments pertaining to kinetically sorbing contaminant plumes avoiding the very heavy computational effort which is generally demanded. For illustration purposes, we consider the movement of one contaminant species, and show how our approximate spatial moments compare with the numerical simulations.     

华北聚煤区火山灰蚀变粘土岩夹矸的研究

本文论述了火山灰蚀为粘土岩夹矸的层位和分布，对结构构造作了系统分类及命名，首次在我国粘土岩夹矸中发现了较广泛分布的铵云母，还有伊利石和纳云母。成因矿物标型特征的研究为探索原始物质提供了可信的证据。     

Oolitic iron formations in Northern Australia

Summary Recent exploration in northern Australia has discovered three shallow water oolitic iron formations, one of Permian age, and two of Upper Proterozoic age. The Permian formation resembles the oxidized oolitic chamositic formations of south-eastern England, but contains more detrital quartz and felspar.The two Precambrian iron formations, consist, below the zone of weathering, of oolites of hematite and of a chamosite-like substance, in a siderite cement, together with well-rounded quartz grains, and are interlayered with sandstones with a chamosite-like cement. Within the zone of weathering the siderite and chamosite are more or less completely replaced by quartz, but with preservation in detail of original textures.Published by permission of the Commonwealth Scientific and Industrial Research Organization (CSIRO).     

Iron-manganese formations in the Baikal region

This work is a review of the modern concepts of the accumulation of Fe and Mn in the Baikal bottom sediments and the regularities of formation of iron-manganese (including phosphate-bearing) nodules in the lake. Special attention is given to the probable participation of hydrothermal water in this process and the genesis of ancient nodules deeply buried in the Baikal sediments. The possible relationship between the shore ores and the nodules in the bottom sediments in the adjacent Baikal regions has been first shown.     

Microbial structures in oolitic iron formations

Ferriferous ooids and microoncoids occur in many sedimentary iron formations. These ferriferous-coated grains are found in fine-grained carbonate-rich groundmasses. Iron mineral-encrusted microbiota are observed in both the coated grains and the groundmass. The branching nature and other morphological features of the microorganisms suggest fungal origins for the oolitic iron ores particularly of the Lower Jurassic (Lorraine Minette). The similarity of the microbial structures in coated grains and their groundmasses suggests that both had developed within microbial mats growing under calm environmental conditions. The contribution of stromatolitic marine fungal mats to the fast extraction and immobilization of iron and thus to the genesis of iron ores is demonstrated. Observations on well-preserved freshwater-derived fungal stromatolites of the Tertiary and laboratory experiments with organotrophic fungal mats confirm the findings on the Jurassic and imply a general role of microorganisms in the formation of such deposits.     

Neoproterozoic banded iron formations

Two epochs of the formation of ferruginous quartzites—Archean-Paleoproterozoic (3.2–1.8 Ga) and Neoproterozoic (0.85–0.7 Ga)—are distinguished in the Precambrian. They are incommensurable in scale: the Paleoproterozoic Kursk Group of the Kursk Magnetic Anomaly (KMA) extends over 1500 km, whereas the extension of Neoproterozoic banded iron formations (BIF) beds does not exceed a few tens of kilometers. Their thickness is up to 200 m and not more than 10 m, respectively. The oldest BIFs are located in old platforms, whereas Neoproterozoic BIFs are mainly confined to Phanerozoic orogenic (mobile) zones. Neoproterozoic BIFs universally associate with glacial deposits and their beds include glacial dropstones. In places, they underlie tillites of the Laplandian (Marinoan) glaciation (635 Ma), but they are more often sandwiched between glaciogenic sequences of the Laplandian and preceding Sturtian or Rapitan glaciation (730–750 Ma). Neoproterozoic BIFs are rather diverse in terms of lithology due to variation in the grade of metamorphism from place to place from low grades of the greenschist facies up to the granulite facies. Correspondingly, the ore component is mainly represented by hematite or magnetite. The REE distribution and (Co + Ni + Cu) index suggest an influence of hydrothermal sources of Fe, although it was subordinate to the continental washout. Iron was accumulated in seawater during glaciations, whereas iron mineralization took place at the earliest stages of postglacial transgressions.     

微生物参与前寒武纪条带状铁建造沉积的研究进展

地球演化早期太古代和早元古代大规模的条带状铁建造(BIF)是目前世界上最重要的铁矿资源。已有的稳定同位素组成、分子化石以及岩石磁学性质等证据支持早期微生物广泛参与了BIF的形成。本文评述了微生物参与BIF形成过程中铁搬运和沉淀及其同位素分馏、生物标志物和岩石磁学证据。深入地研究BIF成矿中的微生物矿化贡献,有助于解释BIF形成机制,反演前寒武纪大气—海洋环境演化,以及理解地球早期生命的过程。     

Oxidation gradients in metamorphosed non-carbonatic manganese formations

This paper aims to ascertain the degree of equilibrium attained with respect to oxygen during metamorphism of non-carbonatic manganiferous sediments and the nature of mobility of oxygen in rocks of adjacent beds by measuring the composition of coexisting phases. Through algebraic analysis of the relevant phase equilibria, a difference of ≃17 kcal in in rocks of adjacent beds is obtained. This confirms the immobile nature of oxygen during metamorphism of manganiferous sediments.     

Gold ore provinces and formations

Granitic magmas result from refusion of sedimentary rocks. Metals associated in gold ore formations are mobilized by magmatic and etamorphic activity from volcanic and sedimentary rocks of a geosynclinal series. The comportment of metals during the processes of mobilization, transfer, and deposition is ruled by their atomic structure and electromagnetic properties. Ionic density (d_i) and concentration coefficient (C_s/Cv) of the metals are chosen as coordinates for plotting the associations of metals of different gold ore formations. The degree of complexity of the associations is a consequence of the degree of heterogeneity of the geosynclinal rock series and of the intermittence or telescoping of the ore deposition process. — B.V. Brajnikov.     

深部地质钻探钻遇弱面地层井孔围岩稳定分析

深部地层地质条件复杂,随钻探向纵深发展,钻遇弱面地层导致井孔围岩失稳将严重影响工程进程。本文总结分析具有弱面地层岩石物理力学特性,探讨强度各向异性孔壁围岩稳定模型的适用性;考虑流体向弱面渗透存在渗透各向异性和传热各向异性,发展了具有弱面地层井孔围岩稳定理论。研究发现,某些强度各向异性模型在特定情况下可能失去其适用性;在深部高温环境下忽略弱面地层渗透和热传的各向异性特征可能会导致井孔围岩压力、破坏区域以及坍塌压力产生较大误差。     

Preliminary study of REE iron formations in China

Geological and geochemical characteristics of REE iron formation (REEIF), a term proposed by Prof. Tu Kuang-chih to specify a special type of Precambrian iron formations rich in REE, are discussed in this paper with special reference to its REE contents, REE distribution patterns, the formation mechanism, the relationship between its development and the multi-stage evolution of the continental crust in China, and the implications of REE as an indicator of oxidation state for ancient atmosphere. Major conclusions are outlined as follows:

1. REEIFs are characterized by high REE concentrations against the very low REE levels in normal Precambrian iron formations.
2. REEIFs are formed by marine sedimentary-diagenetic processes in miogeosynclines or transition zones during Proterozoic times To some extent, volcanic activity may play an important role in the deposition of ore-forming materials. In a broader sense, REEIFs belong to Fe-bearing dolomite formations. Most REEIFs in China may be superimposed by late geological processes such as hydrothermal-metasomatism, migmatization and metamorphism. Generally, REEIFs have much in common with stratabound ore deposits in respect to their characteristic features.
3. Similar to Precambrian iron formations, REE are enriched in LREE. But, the degree of LREE enrichment is noticed to increase of total REE content. Most REEIFs are characterized by high ratios of σ Ce/σY, (Mg+Fe)/Ca, Na/K, Nb/Ta, Zr/Hf, Th/U, Ba/Sr, etc.
4. The extensive occurrence of REEIFs indicates higher REE abundance in the continental crust of China, thus lending further support to the multi-stage theory regarding the evolution of chemical elements and the differentiation in the continental crust of China.
5. Preliminary data seem to support the time-dependence of REE distribution patterns and relative Eu contents of REEIFs in China.

     

Numerical simulation of crack propagation in layered formations

In the present study, a boundary element method based on the higher order displacement discontinuity formulation is presented to solve the general problem of hydraulic fracture propagation in layered formations. Displacement collocation technique is employed to model the higher order displacement variation along the crack and the special crack tip element near its ends. The hydraulic fracture propagation and its interaction with the layer interface in non-homogenous rock materials are studied by the proposed semi-analytical (hybridized boundary element-boundary collocation) method. The maximum tangential stress criterion (or σ-criterion) of fracture mechanics considering different elastic constants (Young modulus and Poisson’s ratio) is used to obtain the fracture path. The fracture propagation from stiff to soft and soft to stiff media for cracks having different inclination angles is modeled, and the effects of elastic constants on the hydraulic fracture propagation is studied. The results show that if the hydraulic fracture originates in the stiffer layer, its capability to cross the layer increases and is vice versa for the softer material. The comparison of the results gained from the numerical method with those in the literature show a good performance of the method in the case of propagation of hydraulic fracture in layered formations.     

On stilpnomelane in some Romanian Carpathian crystalline formations

Summary The stilpnomelane minerals in the epimetamorphic series of the Romanian Carpathians are divided into four genetic groups. Some ferrostilpnomelanes from metamorphic iron-, manganese- and sulfide-ores have been studied optically, chemically, by differential thermal analysis, thermogravimetric analysis, X-ray diffraction, and IR absorption spectroscopy. Several conclusions on the chemical constitution and the widespread occurence of ferrostilpnomelane in the metamorphic ores of the Carpathians are given.

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Über Stilpnomelan in einigen kristallinen Formationen in den rumänischen Karpaten

Zusammenfassung Die Stilpnomelanvorkommen aus dem epimetamorphen Kristallin der rumänischen Karpaten werden in vier genetische Gruppen eingeteilt. Einige aus metamorphosierten Eisen-, Mangan- und Sulfiderzen stammende Ferrostilpnomelane wurden optisch, chemisch, mit Differentialthermoanalyse, Thermogravimetrie, Röntgenbeugung und Ultrarot-Absorptionsspektroskopie untersucht. Als Schlußfolgerungen ergeben sich einige allgemeine Hinweise über die Zusammensetzung des Ferrostilpnomelans in den Kristallinerzen der Karpaten.

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Mit 5 Figures