安徽铜陵矿集区海底喷流沉积体系的流体包裹体微量元素对比

铜陵矿集区与铜-金(多金属)矿床有关的热液活动主要有两大体系。即与海西期海底喷流沉积有关的热液体系和与矽卡岩矿化有关的燕山期岩浆热液体系。查明这两类热液体系的流体包裹体特征对区域找矿和矿床成因研究都有实际意义。在包裹体岩相学研究基础上，应用ICP-MS技术和热爆提取方法，研究了新桥、冬瓜山、峙门口、铜官山、朝山等矿床具代表性的热液石英中流体包裹体的微量元素、稀土元素特征。结果表明，两类热液体系在流体包裹体特征上有较大的区别，在流体的微量元素和稀土元素特征方面也很不相同。海底喷流沉积体系的热液石英中流体包裹体与岩浆热液体系的相比。稀土总量较高，LREE／HREE比值较大，δEu不明显。且Mo／(W Sn)比值较高，反映流体中成矿物质的深源特征；Ga／T1、Rb／Cs大。Zr／Hf低，也不同于岩浆热液体系。     

大井锡多金属成矿地质特征及找矿方向探讨

内蒙古林西大井锡多金属矿是我国北方最大的锡多金属矿床，通过对其地质背景、成矿地质条件、富集规律、控矿因素的认识和分析，建立大井式的综合找矿标志，对指导矿区及其外围找矿，扩大矿产资源、发展地方经济，具有重要的意义。     

Paleozoic serpentinite-enclosed chromitites from Tehuitzingo (Acatlán Complex, southern Mexico): a petrological and mineralogical study

The serpentinites and associated chromitite bodies in Tehuitzingo (Acatlán Complex, southern Mexico) are in close relationship with eclogitic rocks enclosed within a metasedimentary sequence, suggesting that the serpentinites, chromitites and eclogitic rocks underwent a common metamorphic history.Primary chromites from the chromitite bodies at Tehuitzingo are of refractory-grade (Al-rich) and have a chemical composition similar to that expected to be found in an ophiolitic environment. The chromite grains in chromitites and serpentinites are systematically altered to ‘ferritchromite’. The alteration trend is usually characterized by a decrease in the Al, Mg and Cr contents coupled by an increase in Fe³⁺ and Fe²⁺.The Tehutizingo chromitites have low Platinum Group Elements (PGE) contents, ranging from 102 to 303 ppb. The chondrite-normalized PGE patterns are characterized by an enrichment in the Ir-subgroup elements (IPGE=Os, Ir, Ru) relative to the Pd-subgroup elements (PPGE=Rh, Pt, Pd). In addition, all chromitite samples display a negative slope from Ru to Pd [(Os+Ir+Ru)/(Pt+Pd)=4.78−14.13]. These patterns, coupled with absolute PGE abundances, are typical of ophiolitic chromitites elsewhere. Moreover, all the analyzed samples exhibit chondrite-normalized PGE patterns similar to those found for non-metamorphosed ophiolitic chromitites. Thus, the PGE distribution patterns found in the Tehuitzingo chromitites have not been significantly affected by any subsequent Paleozoic high-pressure (eclogite facies) metamorphic event.The chondrite-normalized PGE patterns of the enclosing serpentinites also indicate that the PGE distribution in the residual mantle peridotites exposed in Tehuitzingo was unaffected by high-pressure metamorphism, or subsequent hydrothermal alteration since the serpentinites show a similar pattern to that of partially serpentinized peridotites present in mantle sequences of non-metamorphosed ophiolites.Our main conclusion is that the chromitites and serpentinites from Tehuizingo experienced no significant redistribution (or concentration) of PGE during the serpentinization process or the high-pressure metamorphic path, or during subsequent alteration processes. If any PGE mobilization occurred, it was restricted to individual chromitite bodies without changing the bulk-rock PGE composition.Our data suggest that the Tehuitzingo serpentinites and associated chromitites are a fragment of oceanic lithosphere formed in an arc/back-arc environment, and represent an ophiolitic mantle sequence from a supra-subduction zone, the chemical composition of which remained essentially unchanged during the alteration and metamorphic events that affected the Acatlán Complex.     

Indicator Simulation Accounting for Multiple-Point Statistics

Geostatistical simulation aims at reproducing the variability of the real underlying phenomena. When nonlinear features or large-range connectivity is present, the traditional variogram-based simulation approaches do not provide good reproduction of those features. Connectivity of high and low values is often critical for grades in a mineral deposit. Multiple-point statistics can help to characterize these features. The use of multiple-point statistics in geostatistical simulation was proposed more than 10 years ago, on the basis of the use of training images to extract the statistics. This paper proposes the use of multiple-point statistics extracted from actual data. A method is developed to simulate continuous variables. The indicator kriging probabilities used in sequential indicator simulation are modified by probabilities extracted from multiple-point configurations. The correction is done under the assumption of conditional independence. The practical implementation of the method is illustrated with data from a porphyry copper mine.     

Mudstones of the Tanqua Basin, South Africa: an analysis of lateral and stratigraphic variations within mudstones, and a comparison of mudstones within and between turbidite fans

Permian deep‐water mudstones in the Tanqua Basin, South Africa, have been studied using geochemical and spectral gamma ray techniques. The mudstones occur as thick sequences between sand‐rich submarine fans, but also occur as thinner mud‐rich units within each fan. The interfan mudstones are interpreted to have accumulated during transgression and the consequent period of relatively high sea‐level, while the submarine fans and their intrafan mudstones were deposited during regression and relatively low sea‐level. Geochemical analyses revealed systematic differences between interfan and intrafan mudstones because the two types of mudstones have slightly different source lithologies. Differences between the two types of mudstone suggest that changes in relative sea‐level played a role in controlling exposure of sediment source areas. There are geochemical signals that display systematic stratigraphic trends within both interfan and intrafan mudstones. These are best explained by gradual denudation, exposure and weathering of different lithologies within a single sediment source area. Both interfan and intrafan mudstones have uniform geochemical signals along the flow direction except for the relative amount of uranium. It is most likely that the basinward increase in uranium in the mudstones is the result of reduced clastic dilution of uranium‐bearing pelagic fallout.     

Accurate U-Pb Age and Trace Element Determinations of Zircon by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry

Various zircons of Proterozoic to Oligocene ages (1060-31 Ma) were analysed by laser ablation-inductively coupled plasma-mass spectrometry. Calibration was performed using Harvard reference zircon 91500 or Australian National University reference zircon TEMORA 1 as external calibrant. The results agree with those obtained by SIMS within 2s error. Twenty-four trace and rare earth elements (P, Ti, Cr, Y, Nb, fourteen REE, Hf, Ta, Pb, Th and U) were analysed on four fragments of zircon 91500. NIST SRM 610 was used as the reference material and ²⁹Si was used as internal calibrant. Based on determinations of four fragments, this zircon shows significant intra-and inter-fragment variations in the range from 10% to 85% on a scale of 120 μm, with the variation of REE concentrations up to 38.7%, although the chondrite-normalised REE distributions are very similar. In contrast, the determined age values for zircon 91500 agree with TIMS data and are homogeneous within 8.7 Ma (2 s ). A two-stage ablation strategy was developed for optimising U-Pb age determinations with satisfactory trace element and REE results. The first cycle of ablation was used to collect data for age determination only, which was followed by continuous ablation on the same spot to determine REE and trace element concentrations. Based on this procedure, it was possible to measure zircon ages as low as 30.37 0.39 Ma (MSWD = 1.4; 2 s ). Other examples for older zircons are also given.     

Nuclear Waste Disposal Simulations: Couplex Test Cases

We give some results obtained for the Couplex test cases proposed by the ANDRA. In this paper our aim is twofold. Firstly, to compute the release of nuclides out of the repository by concentrating on the 3D near field (Couplex 2). The simulation of the transport phenomena takes into account the dissolution of the glass containers and congruent emissions of the radio-nuclides including filiation chains and some simplified chemistry. Secondly, it is to use the near field computations in order to simulate the nuclide migrations in a 2D far field (Couplex 3). Coupling in between the two simulations takes into consideration the periodicity of the disposal modules and the geometry of the repository described in Couplex 1. The mixed finite element and discontinuous Galerkin methods are used to solve the convection–diffusion equations. In order to handle the nonlinear precipitation/dissolution term, we developed a new iterative technique that combines Picard and Newton–Raphson methods.     

From in-situ coal to fly ash: a study of coal mines and power plants from Indiana

This paper presents data on the properties of coal and fly ash from two coal mines and two power plants that burn single-source coal from two mines in Indiana. One mine is in the low-sulfur (<1%) Danville Coal Member of the Dugger Formation (Pennsylvanian) and the other mines the high-sulfur (>5%) Springfield Coal Member of the Petersburg Formation (Pennsylvanian). Both seams have comparable ash contents (11%). Coals sampled at the mines (both raw and washed fractions) were analyzed for proximate/ultimate/sulfur forms/heating value, major oxides, trace elements and petrographic composition. The properties of fly ash from these coals reflect the properties of the feed coal, as well as local combustion and post-combustion conditions. Sulfur and spinel content, and As, Pb and Zn concentrations of the fly ash are the parameters that most closely reflect the properties of the source coal.     

Indicator mineralogy of kimberlite boulders from eskers in the Kirkland Lake and Lake Timiskaming areas, Ontario, Canada

Sixteen kimberlite boulders were collected from three sites on the Munro and Misema River Eskers in the Kirkland Lake kimberlite field and one site on the Sharp Lake esker in the Lake Timiskaming kimberlite field. The boulders were processed for heavy-mineral concentrates from which grains of Mg-ilmenite, chromite, garnet, clinopyroxene and olivine were picked, counted and analyzed by electron microprobe. Based on relative abundances and composition of these mineral phases, the boulders could be assigned to six mineralogically different groups, five for the Kirkland Lake area and one for the Lake Timiskaming area. Their indicator mineral composition and abundances are compared to existing data for known kimberlites in both the Kirkland Lake and Lake Timiskaming areas. Six boulders from the Munro Esker form a compositionally homogeneous group (I) in which the Mg-ilmenite population is very similar to that of the A1 kimberlite, located 7–12 km N (up-ice), directly adjacent to the Munro esker in the Kirkland Lake kimberlite field. U–Pb perovskite ages of three of the group I boulders overlap with that of the A1 kimberlite. Three other boulders recovered from the same localities in the Munro Esker also show some broad similarities in Mg-ilmenite composition and age to the A1 kimberlite. However, they are sufficiently different in mineral abundances and composition from each other and from the A1 kimberlite to assign them to different groups (II–IV). Their sources could be different phases of the same kimberlite or—more likely—three different, hitherto unknown kimberlites up-ice of the sample localities along the Munro Esker in the Kirkland Lake kimberlite field. A single boulder from the Misema River esker, Kirkland Lake, has mineral compositions that do not match any of the known kimberlites from the Kirkland Lake field. This suggests another unknown kimberlite exists in the area up-ice of the Larder Lake pit along the Misema River esker. Six boulders from the Sharp Lake esker, within the Lake Timiskaming field, form a homogeneous group with distinct mineral compositions unmatched by any of the known kimberlites in the Lake Timiskaming field. U–Pb perovskite age determinations on two of these boulders support this notion. These boulders are likely derived from an unknown kimberlite source up-ice from the Seed kimberlite, 4 km NW of the Sharp Lake pit, since indicator minerals with identical compositions to those of the Sharp Lake boulders have been found in till samples collected down-ice from Seed. Based on abundance and composition of indicator minerals, most importantly Mg-ilmenite, and supported by U–Pb age dating of perovskite, we conclude that the sources of 10 of the 16 boulders must be several hitherto unknown kimberlite bodies in the Kirkland Lake and Lake Timiskaming kimberlite fields.     

Reduction of ground vibration by means of barriers or soil improvement along a railway track

Trains running in built-up areas are a source to ground-borne noise. A careful design of the track may be one way of minimizing the vibrations in the surroundings. For example, open or infilled trenches may be constructed along the track, or the soil underneath the track may be improved. In this work, the influence of the track design and properties on the level of ground vibration due to a vehicle moving with subsonic speed is examined. A coupled finite element-boundary element model of the track and subsoil is employed, adopting a formulation in the moving frame of reference following the vehicle. The computations are carried out in the frequency domain for various combinations of the vehicle speed and the excitation frequency. The analyses indicate that open trenches are more efficient than infilled trenches or soil stiffening–even at low frequencies. However, the direction of the load is of paramount importance. For example, the response outside a shallow open trench may change dramatically when horizontal load is applied instead of vertical load.