Fully coupled elastoplastic hydro-mechanical analysis of unsaturated porous media using a meshfree method

This paper presents the first application of an advanced meshfree method, ie, the edge-based smoothed point interpolation method (ESPIM), in simulation of the coupled hydro-mechanical behaviour of unsaturated porous media. In the proposed technique, the problem domain is spatially discretised using a triangular background mesh, and the polynomial point interpolation method combined with a simple node selection scheme is adopted for creating nodal shape functions. Smoothing domains are formed on top of the background mesh, and a constant smoothed strain, created by applying the smoothing operation over the smoothing domains, is assigned to each smoothing domain. The deformation and flow models are developed based on the equilibrium equation of the mixture, and linear momentum and mass balance equations of the fluid phases, respectively. The effective stress approach is followed to account for the coupling between the flow and deformation models. Further coupling among the phases is captured through a hysteretic soil water retention model that evolves with changes in void ratio. An advanced elastoplastic constitutive model within the context of the bounding surface plasticity theory is employed for predicting the nonlinear behaviour of soil skeleton. Time discretisation is performed by adopting a three-point discretisation method with growing time steps to avoid temporal instabilities. A modified Newton-Raphson framework is designed for dealing with nonlinearities of the discretised system of equations. The performance of the numerical model is examined through a number of numerical examples. The state-of-the-art computational scheme developed is useful for simulation of geotechnical engineering problems involving unsaturated soils.     

Fast genetic mapping in barley: case studies of cuticle mutants using RNA-sequencing

Barley(Hordeum vulgare L.) is one of the earliest domesticated crop species and ranked as the fourth largest cereal production worldwide. Forward genetic studies in barley have greatly advanced plant genetics during the last century; however, most genes are identified by the conventional mapping method. Array genotyping and exome-capture sequencing have also been successfully used to target the causal mutation in barley populations, but these techniques are not widely adopted because of associated costs and partly due to the huge genome size of barley. This review summarizes three mapping cases of barley cuticle mutants in our laboratory with the help of RNA-sequencing. The causal mutations have been successfully identified for two of them and the target genes are located in the pericentromeric regions. Detailed information on the mapping-by-sequencing, mapping-and-sequencing, and RNA-sequencing assisted linkage mapping are presented and some limitations and challenges on the mapping assisted by RNA sequencing are also discussed. The alternative and elegant methods presented in this review may greatly accelerate forward genetics of barley mapping, especially for laboratories without large funding.     

Raman microspectrometry, FT-IR and inclusion characteristics of gem garnets from Tanzania and Madagascar

Chemical composition, Raman microspectrometry, and Fourier transform infrared (FT-1R) and SEM-CL (Cathodluminescence) analyses are carried out for Tanzania and Madagascar garnets for locality identification. Inclusion study was sustained after electron probe microanalysis (EPMA). Needle-like illmenites, apatites and zircons were the most common solid inclusions in Tanzania garnets. Madagascar garnets revealed rutile needles and apatites were also observed, but differences in size, shape and distribution patterns were noticed compared to Tanzania garnets. Tanzania garnets exhibited all types of observable fluid inclusions such as ““ fingerprint““ pattern, called Type Ⅰ-A, liquid-only (L) single phase fluid inclusion, called Type Ⅰ-B and Type Ⅱ-A ( L S), Type Ⅱ-B ( L V) and Type Ⅲ-A (L Sylvite even if all examined garnets from three localities retained ““fingerprint““ features, so called, partially healed fractures, in common. Chemical composition, Raman microspectrometry and Fourier transform infrared (FT-IR) analysis taken turned out to be useful methods for the purpose of this study. Using consequences of SEM-CL and inclusion study, accordingly, the locality identification of gem-quality garnets is capable of being available in further application for other kinds of gemstones.     

The Expansion of the Distance Between Two Arbitrary Gravitating Points as Applied to Specific Models of Celestial Bodies

For the complete system of biharmonic functions a suitable representation in spheroidal coordinates is found. It is used for expanding the distance between two arbitrary gravitating points and its inverse quantity in appropriate series. Such expansions can be of interest and useful in a number of problems of celestial mechanics and stellar dynamics.     

Application of stress release models to historical earthquakes from North China

Univariate and multivariate stress release models are fitted to historical earthquake data from North China. It is shown that a better fit is obtained by treating separately the Eastern part of the region, including the North China Plain and Bohai Sea, and the Western part of the region, including the Ordos Plateau and its Eastern boundary. Further improvement is obtained by fitting the large events (M7.6) and smaller events in the Western region by different stress release models. The comparisons are made by computing the likelihoods of the fitted models and discounting the number of parameters used by Akaike's AIC criterion. The models are used to develop long-term risk scenarios for the East and West regions.     

Fluid and source magma evolution of the Questa porphyry Mo deposit,New Mexico,USA

Combined fluid inclusion microthermometry and microanalysis by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) are used to constrain the hydrothermal processes forming a typical Climax-type porphyry Mo deposit. Molybdenum mineralisation at Questa occurred in two superimposed hydrothermal stages, a magmatic-hydrothermal breccia and later stockwork veining. In both stages, texturally earliest fluids were single-phase, of low salinity (~7 wt.% NaCl_equiv.) and intermediate-density. Upon decompression to ~300 bar, they boiled off a vapour phase, leaving behind a residual brine (up to 45 wt.% NaCl_equiv) at temperatures of ~420°C. The highest average Mo concentrations in this hot brine were ~500 μg/g, exceeding the Mo content of the intermediate-density input fluid by about an order of magnitude and reflecting pre-concentration of Mo by fluid phase separation prior to MoS₂ deposition from the brine. Molybdenum concentrations in brine inclusions, then, decrease down to 5 μg/g, recording Mo precipitation in response to cooling of the saline liquid to ~360°C. Molybdenite precipitation from a dense, residual and probably sulphide-depleted brine is proposed to explain the tabular shape of the ore body and the absence of Cu-Fe sulphides in contrast to the more common Cu-Mo deposits related to porphyry stocks. Cesium and Rb concentrations in the single-phase fluids of the breccia range from 2 to 8 and from 40 to 65 μg/g, respectively. In the stockwork veins, Cs and Rb concentrations are significantly higher (45–90 and 110–230 μg/g, respectively). Because Cs and Rb are incompatible and hydrothermally non-reactive elements, the systematic increase in their concentration requires two distinct pulses of fluid exsolution from a progressively more fractionated magma. By contrast, major element and ore metal concentrations of these two fluid pulses remain essentially constant. Mass balance calculations using fluid chemical data from LA-ICPMS suggest that at least 25 km³ of melt and 7 Gt of deep input fluid were necessary to provide the amount of Mo contained in the stockwork vein stage alone. While the absolute amounts of fluid and melt are uncertain, the well-constrained element ratios in the fluids together with empirical fluid/melt partition coefficients derived from the inclusion analyses suggest a high water content of the source melt of ~10%. In line with other circumstantial evidence, these results suggest that initial fluid exsolution may have occurred at a confining pressure exceeding 5 kbar. The source of the molybdenum-mineralising fluids probably was a particularly large magma chamber that crystallised and fractionated in the lower crust or at mid-crustal level, well below the shallow intrusions immediately underlying Questa and other porphyry molybdenum deposits. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The sandstone-hosted stratiform copper mineralization at Mwitapile and its relation to the mineralization at Lufukwe, Lufilian foreland, Democratic Republic of Congo

The Lufilian foreland is a triangular-shaped area located in the SE of the Democratic Republic of Congo and to the NE of the Lufilian arc, which hosts the well-known Central African Copperbelt. The Lufilian foreland recently became an interesting area with several vein-type (e.g., Dikulushi) and stratiform (e.g., Lufukwe and Mwitapile) copper occurrences. The Lufilian foreland stratiform Cu mineralization is, to date, observed in sandstone rock units belonging to the Nguba and Kundelungu Groups (Katanga Supergroup).The Mwitapile sandstone-hosted stratiform Cu prospect is located in the north eastern part of the Lufilian foreland. The host rock for the Cu mineralization is the Sonta Sandstone of the Ngule Subgroup (Kundelungu Group). A combined remote sensing, petrographic and fluid inclusion microthermometric analysis was performed at Mwitapile and compared with similar analysis previously carried out at Lufukwe to present a metallogenic model for the Mwitapile- and Lufukwe-type stratiform copper deposits. Interpretation of ETM+ satellite images for the Mwitapile prospect and the surrounding areas indicate the absence of NE–SW or ENE–WSW faults, similar to those observed controlling the mineralization at Lufukwe. Faults with these orientations are, however, present to the NW, W, SW and E of the Mwitapile prospect. At Mwitapile, the Sonta Sandstone host rock is intensely compacted, arkosic to calcareous with high silica cementation (first generation of authigenic quartz overgrowths). In the Sonta Sandstone, feldspar and calcite are present in disseminated, banded and nodular forms. Intense dissolution of these minerals caused the presence of disseminated rectangular, pipe-like and nodular dissolution cavities. Sulfide mineralization is mainly concentrated in these cavities. The hypogene sulfide minerals consist of two generations of pyrite, chalcopyrite, bornite and chalcocite, separated by a second generation of authigenic quartz overgrowth. The hypogene sulfide minerals are replaced by supergene digenite and covellite. Fluid inclusion microthermometry on the first authigenic quartz phase indicates silica precipitation from an H₂O–NaCl–CaCl₂ fluid with a minimum temperature between 111 and 182 °C and a salinity between 22.0 and 25.5 wt.% CaCl₂ equiv. Microthermometry on the second authigenic quartz overgrowths and in secondary trails related to the mineralization indicate that the mineralizing fluid is characterized by variable temperatures (Th = 120 to 280 °C) and salinities (2.4 to 19.8 wt.% NaCl equiv.) and by a general trend of increasing temperatures with increasing salinities.Comparison between Mwitapile and Lufukwe indicates that the stratiform Cu mineralization in the two deposits is controlled by similar sedimentary, diagenetic and structural factors and likely formed from a similar mineralizing fluid. A post-orogenic timing is proposed for the mineralization in both deposits. The main mineralization controlling factors are grain size, clay and pyrobitumen content, the amount and degree of feldspar and/or calcite dissolution and the presence of NE–SW to ENE–WSW faults. The data support a post-orogenic fluid-mixing model for the Mwitapile- and Lufukwe-type sandstone-hosted stratiform Cu deposits, in which the mineralization is related to the mixing between a Cu-rich hydrothermal fluid, with a temperature up to 280 °C and a maximum salinity of 19.8 wt.% NaCl equiv., with a colder low salinity reducing fluid present in the sandstone host rock. The mineralizing fluid likely migrated upwards to the sandstone source rocks along NE–SW to ENE–WSW orientated faults. At Lufukwe, the highest copper grades at surface outcrops and boreholes were found along and near to these faults. At Mwitapile, where such faults are 2 to 3 km away, the Cu grades are much lower than at Lufukwe. Copper precipitation was possibly promoted by reduction from pre-existing hydrocarbons and non-copper sulfides and by the decrease in fluid salinity and temperature during mixing. Based on this research, new Cu prospects were proposed at Lufukwe and Mwitapile and a set of recommendations for further Cu exploration in the Lufilian foreland is presented.     

流体包裹体成分测定的低温相变和显微拉曼光谱分析技术研究进展

论述了包裹体低温分析技术的原理以及进展。传统的流体包裹体低温分析技术是以显微冷冻测温测定无机盐体系为主,目前已发展到应用低温原位拉曼光谱技术对包裹体中的阳离子和阴离子进行定量-半定量分析。油气包裹体原位低温分析技术也取得了较大的突破,对不同成分油气包裹体低温下的相变过程取得了一定的认识,据此对油气包裹体进行分类,推测其主要成分,为油气包裹体计算提供基础参数。     

湖北徐家山锑矿床流体包裹体特征及其意义

文章利用激光拉曼光谱和显微测温学方法,对湖北徐家山锑矿床成矿期的石英、重晶石和方解石中的流体包裹体进行了研究。研究表明,这些矿物中的流体包裹体主要有纯液体包裹体和液体包裹体(气相 液相)2类,其液体包裹体的气相成分为H2O±CO2±N2;石英、重晶石和方解石的均一温度分别为134~258℃、154~259℃和145~230℃,主要集中于150~200℃;流体的盐度w(NaCleq)和密度分别集中于3%~6%和0.90~0.96g/cm3。流体包裹体资料揭示出该矿床为典型的中低温热液锑矿床,其成矿流体为中低温、低盐度、中等密度热液。结合H、O、Sr、Pb同位素等研究结果,进一步推断该成矿热液主要是经深部循环演化的大气降水。     

豫西前河构造蚀变岩型金矿成矿过程中的流体-岩石反应

前河金矿区位于华北地台南缘,赋存在中元古界熊耳群安山岩和英安岩中,矿体受断裂破碎带控制。含矿热液在迁移过程中与围岩发生了广泛的流体-岩石反应而引起热液蚀变。本区石英中有4种类型的流体包裹体,均一温度范围为145～331℃,其中含CO2包裹体的完全均一温度主要分布在中-高温区。成矿流体的密度和压力变化范围分别是0.68～0.94g/cm3和(367.01～896.55)×105Pa。金大量沉淀成矿时的流体特征为:温度213～260℃、密度0.80～0.89g/cm3和压力(502.86～710.57)×105Pa。流体相为SO42->Na >Cl->K 型,CO2/H2O比值及N2、H2S、Ar、C2H6等挥发分的含量明显增高,f(CO2)、f(H2S)、f(CH4)和Eh值增大;f(O2)、f(H2O)和pH值减小。在青磐岩化安山岩的基础上发生的流体-岩石反应是造成本矿床金沉淀成矿的最主要原因。