Steady-diffusion modelling of a reaction zone between a metamorphosed basic dyke and a marble from Hirao-dai, Fukuoka, Japan

A reaction zone between a metamorphosed basic dyke and marble at Hirao-dai, north Kyushu, Japan, consists of well-organized sequential zones of diopside, garnet and wollastonite; textures are characteristic of diffusion-controlled structures. The reaction zone formed during contact metamorphism associated with intrusion of a Cretaceous granodiorite at ∼300 MPa and 700 °C. The metamorphosed basic dyke consists of diopside, biotite and plagioclase ( X _Ab = 0.4–0.8), whereas the marble is almost pure calcite. The initial boundary between the dyke and the marble is probably located within the current diopside zone, as calcite occurs as remnants among diopside grains in areas close to the boundary with the garnet zone. This observation provides a criterion to judge the stability of the zonal sequence in our modelling. The formation of the reaction zone is attributed to a single-stage steady-state process with five overstepping reactions. CaO, MgO, FeO, SiO₂ and AlO_3/2 are the reaction-controlling components that are necessary to describe the growth of the reaction zone. An isochemical steady-diffusion model cannot reproduce the measured phase ratios of product minerals; this indicates open-system behaviour of the reaction zone. The choice of closure components is an essential task in the treatment of open-system modelling, together with determination of phase ratios (Ashworth & Birdi model) or estimation of boundary fluxes (Johnson & Carlson model). Of all the possible combinations of closure components, closure conditions for CaO and MgO provide the best results for both models. The stability of the zonal sequence is limited at relatively large values of L _SiSi/ L _CaCa. Similar results from the two models confirm their consistency under the same closure conditions.     

Interpreting prograde-growth histories of Al2SiO5 triple-point rocks using oxygen-isotope thermometry: an example from the Truchas Mountains, USA

Oxygen‐isotope compositions of kyanite, andalusite, prismatic sillimanite and fibrolite from the Proterozoic terrane in the Truchas Mountains, New Mexico differ from one another, suggesting that these minerals did not grow in equilibrium at the Al₂SiO₅ (AS) polymorph‐invariant point as previously suggested. Instead, oxygen‐isotope temperature estimates indicate that growth of kyanite, andalusite and prismatic sillimanite occurred at c. 575, 615 and 640 °C respectively. Temperature estimates reported in this paper are interpreted as those of growth for the different AS polymorphs, which are not necessarily the same as peak metamorphic temperatures for this terrane. Two distinct temperature estimates of c. 580 °C and c. 700 °C are calculated for most fibrolite samples, with two samples yielding clear evidence of quartz‐fibrolite oxygen‐isotope disequilibrium. These data indicate that locally, and potentially regionally, oxygen‐isotope disequilibrium between quartz and fibrolite may have resulted from rapid fibrolite nucleation. Pressures of mineral growth that were extrapolated from oxygen‐isotope thermometry results and calculated using petrological constraints suggest that kyanite and one generation of fibrolite grew during M1 at 5 kbar, and that andalusite, prismatic sillimanite and a second generation of fibrolite grew during M2 at 3.5 kbar. M1 and M2 therefore represent two distinct metamorphic events that occurred at different crustal levels. The ability of the AS polymorphs to retain δ¹⁸O values of crystallization make these minerals ideal to model prograde‐growth histories of mineral assemblages in metamorphic terranes and to understand more clearly the pressure–temperature histories of multiple metamorphic events.     

Reaction progress related to indentation structures at glaucophane/glaucophane contacts in an impure marble from Syros, Greece

Microstructures of brittle mineral grains embedded in a ductile matrix provide information on the influence of stress concentration on reaction progress during metamorphism. Under non-hydrostatic conditions, contrasts of mechanical properties between minerals possibly cause stress concentrations at specific grain boundaries, which may result in a localization of subsequent reactions. In an impure marble from Syros, Greece, glaucophane grains occurring in a calcite matrix commonly impinge on other glaucophane grains to form concavo-convex boundary contacts. The geometrical relationship between grain boundary and growth zoning within glaucophane grains indicates that indentation and dissolution occurred preferentially at the glaucophane/glaucophane contacts in response to compression normal to the foliation. In contrast, idioblastic surfaces of glaucophane were preserved at glaucophane/calcite boundaries, indicating that stress concentrated at glaucophane/glaucophane contacts. The retrograde minerals (winchite, albite and biotite) that were formed by consuming glaucophane are observed not only at the extensive site, but also at the 'compressive' site where indentation occurred. The precipitation of retrograde minerals at the extensive sites was accompanied by glaucophane dissolution at the indentation stage. In contrast, the formation of retrograde minerals at the 'compressive' site indicates that retrograde replacement preferentially proceeded at the indented sites even after stress relaxation. Such a localization of the replacement suggests that the formation of damaged zones around glaucophane/glaucophane contacts induced by stress concentration would have provided the preferential sites for glaucophane breakdown at the later stage.     

基于RS和GIS的富平县城镇空间扩张演变规律及其驱动力分析

本文依据2003—2015年间6个时相的影像数据,对富平县城市扩张进行了研究。基于遥感动态监测的城市范围提取方法,确定了各时相的城市范围。然后结合城市扩展速率、扩展强度、分形维数和紧凑度这四个空间特征指数,对城市扩张的数量特征、形态变化和空间特征进行了分析。应用空间分析方法研究了富平县城市的扩张分布和扩张方向,讨论了城市扩张的时空特征,并且分析了其扩张的驱动力。     

Origin of Pyroxenite-Peridotite Veined Mantle by Refertilization Reactions: Evidence from the Ronda Peridotite (Southern Spain)

The Ronda orogenic peridotite (southern Spain) contains a varietyof pyroxene-rich rocks ranging from high-pressure garnet granulitesand pyroxenites to low-pressure plagioclase–spinel websterites.The ‘asthenospherized’ part of the Ronda peridotitecontains abundant layered websterites (‘group C’pyroxenites), without significant deformation, that occur asswarms of layers showing gradual modal transitions towards theirhost peridotites. Previous studies have suggested that theselayered pyroxenites formed by the replacement of refractoryspinel peridotites. Here, we present a major- and trace-element,and numerical modelling study of a layered outcrop of groupC pyroxenite near the locality of Tolox aimed at constrainingthe origin of these pyroxenites after host peridotites by pervasivepyroxene-producing, refertilization melt–rock reactions.Mg-number [= Mg/(Mg + Fe) cationic ratio] numerical modellingshows that decreasing Mg-number with increasing pyroxene proportion,characteristic of Ronda group C pyroxenites, can be accountedfor by a melt-consuming reaction resulting in the formationof mildly evolved, relatively low Mg-number melts (0·65)provided that the melt fraction during reaction and the time-integratedmelt/rock ratio are high enough (>0·1 and > 1,respectively) to balance Mg–Fe buffering by peridotiteminerals. This implies strong melt focusing caused by melt channellingin high-porosity domains resulting from compaction processesin a partial melted lithospheric domain below a solidus isothermrepresented by the Ronda peridotite recrystallization front.The chondrite-normalized rare earth element (REE) patterns ofgroup C whole-rocks and clinopyroxenes are convex-upward. Numericalmodeling of REE variations in clinopyroxene produced by a pyroxene-forming,melt-consuming reaction results in curved trajectories in the(Ce/Nd)_N vs (Sm/Yb)_N diagram (where N indicates chondrite normalized).Based on (Ce/Nd)_N values, two transient, enriched domains betweenthe light REE (LREE)-depleted composition of the initial peridotiteand that of the infiltrated melt may be distinguished in thereaction column: (1) a lower domain characterized by convex-upwardREE patterns similar to those observed in Ronda group C pyroxenite–peridotite;(2) an upper domain characterized by melts with strongly LREE-enrichedcompositions. The latter are probably volatile-rich, small-volumemelt fractions residual after the refertilization reactionsthat generated group C pyroxenites, which migrated throughoutthe massif—including the unmelted lithospheric spinel-tectonitedomain. The Ronda mantle domains affected by pyroxenite- anddunite- or harzburgite-forming reactions (the ‘layeredgranular’ subdomain and ‘plagioclase-tectonite’domain) are on average more fertile than the residual, ‘coarsegranular’ subdomain at the recrystallization front. Thisindicates that refertilization traces the moving boundariesof receding cooling of a thinned and partially melted subcontinentallithosphere. This refertilization process may be widespreadduring transient thinning and melting of depleted subcontinentallithospheric mantle above upwelling asthenospheric mantle. KEY WORDS: subcontinental mantle; refertilization; pyroxenite; peridotite; websterite; melt–rock reaction; plagioclase; trace elements     

中国城市空气质量时空演化特征及社会经济驱动力

城市空气污染是中国在快速城镇化和经济发展过程中亟待解决的难题。利用2013年和2014年全国城市空气质量数据,综合ArcGIS空间分析和统计分析,从年度、季节、月份、小时4个时间尺度比较归纳了全国城市空气质量的时空间演化特征,并采用空间计量模型,从全国和区域两个空间尺度,量化分析了城市空气质量变化的社会经济驱动力。结果表明：① 全国城市空气质量全年达标天数比例增加,但空气污染程度加重,高污染区域恶化态势明显;② 城市空气质量与生产生活活动表现出一定的时间耦合性,基本呈现“日出趋差、日落趋优”的态势;③ 全国城市空气污染表现出“东重西轻、北重南轻”的空间格局,区域一体化态势明显;④ 区域城市空气污染的总体程度和分布结构具有明显的分异特征,区域空气污染形成和演化路径可基本归纳为：“重点城市污染加重—重点城市污染扩散—区域整体污染加重—重点城市引领治污—区域污染联防联控—区域整体污染减轻”;⑤ 从全国层面看,能源消耗、工业化和技术进步是推动城市空气质量恶化的重要因素,经济发展对城市空气质量改善具有显著的推动作用。⑥ 受各地区资源环境基础和社会经济发展阶段影响,各类社会经济因素对城市空气质量改善的驱动方向和驱动强度差异明显。在结论的基础上,讨论了中国经济发展和环境变化关系的区域分异以及发展理念。     

Efficient detection of pathogen virus in sand dabs, Paralichthys olivaceus using loop-mediated isothermal amplification (LAMP)

Viral hemorrhagic septicemia virus (VHSV) and marine birnavirus (MABV) are the causative pathogens for some of the most explosive epidemics of emerging viral diseases in many Asian countries, leading to huge economic losses in aquaculture. Rapid molecular detection for surveillance or diagnosis has been a critical component in reducing the prevalence of pathogen infection. The loop-mediated isothermal amplification (LAMP) of DNA is currently one of the most commonly used molecular diagnostic tools, as it is simple, quick, and easy to amplify target DNA under isothermal conditions. In the present study, a novel and highly specific LAMP assay for the sensitive and rapid detection of VHSV and MABV infection in fish was developed. Using a set of synthesized primers matching a specific region of the genome, the efficiency and specificity of the LAMP assay were optimized in terms of the reaction temperature and DNA polymerase concentration, as they are the main determinants of the sensitivity and specificity of the LAMP assay. In particular, we demonstrated that our assay could be applied to efficient detection of VHSV and MABV infection in the wild fish, Paralichthys olivaceus. Our results demonstrate the simplicity and convenience of this method for the detection of viral infection in aquatic organisms.     

南公珠错地幔橄榄岩:雅鲁藏布江缝合带西段一个典型的大洋地幔橄榄岩

西藏阿里地区的南公珠错蛇绿岩产在公珠错的南侧,空间上属于雅鲁藏布江缝合带西段之南亚带蛇绿岩。该蛇绿岩主要由地幔橄榄岩和辉长岩等基性岩类组成。地幔橄榄岩中约80%为方辉橄榄岩,20%为二辉橄榄岩,纯橄岩较少。南公珠错地幔橄榄岩矿物化学特征表现为橄榄石具有较低的Fo(89.3~91.4)值、辉石具有较高的Al_2O_3含量(1.89%~6.06%)、尖晶石具有较低的Cr~#(12.7~28.3)值。与原始地幔相比南公珠错地幔橄榄岩的全岩地球化学特征具有较高的MgO含量和较低的Al_2O_3、CaO和TiO_2等易熔元素含量;方辉橄榄岩和二辉橄榄岩的稀土元素总含量分别介于0.66×10-6~1.10×10-6和0.90×10~(-6)~3.78×10~(-6)之间,明显低于原始地幔值,其稀土元素配分模式为轻稀土元素轻微富集型;在原始地幔标准化微量元素蜘蛛图中,南公珠错地幔橄榄岩显示出强烈的U正异常、Nd轻微正异常和强不相容元素Zr的负异常;方辉橄榄岩和二辉橄榄岩的铂族元素总量分别介于15.26×10~(-9)~25.23×10~(-9)和18.74×10~(-9)~26.86×10~(-9)之间,二者含量的变化较小,南公珠错地幔橄榄岩PGEs球粒陨石标准化图解显示其为接近于原始地幔的"平坦型"。南公珠错地幔橄榄岩的矿物化学和全岩地球化学特征与深海橄榄岩相似,指示它们可能形成于大洋扩张脊环境。定量模拟估算表明,南公珠错地幔橄榄岩可能来源于地幔中的尖晶石相二辉橄榄岩源区,系经历了至多16%部分熔融的残余。LREE的微富集和较高的Pd/Ir、Rh/Ir比值指示它们还经历了岩石-熔体反应作用。初步结论认为南公珠错地幔橄榄岩形成于大洋脊环境,为尖晶石相二辉橄榄岩地幔源区较低程度部分熔融的残余,但经历了后期岩石-熔体反应作用。     

Smog Chamber Study on the Ozone Formation Potential of Acetaldehyde

Acetaldehyde is one of the important VOC species of O3 precursors in the atmospheric environment. The influences of relative humidity (RH) and initial VOC/NOx ratio (RCN) on the formation of O3 are studied in smog chamber experiments, and the MCM v3.3.1 mechanism of acetaldehyde is modified based on the experimental results. In low-RH conditions (RH= 11.6％±1.1％), the O3 concentration at 6 h increases first and then decreases with the increase of RCN, and the RCN at the inflection point of O3 concentrations is 3.2. In high-RH experiments (RH = 78.8％±1.0％), variation of the O3 concentration at 6 h with RCN is similar to that in low-RH experiments, but the RCN at the inflection point is 2.8. RH has no significant effect on the O3 concentrations under low RCN (< 3), whereas it has a negative effect under high RCN (> 3). Compared with the experimental results, original MCM v3.3.1 greatly underestimates the O3 concentrations. Addition of both the photolysis process of peroxyacetyl nitrate and the photolysis process of HNO3 on the reactor surface into the original MCM can reduce the difference between the simulated O3 concentrations and the experimental results at 6 h from 24％-35％ and 17％-49％ to 6％-26％ and 10％-42％ under low- and high-RH conditions, respectively. The maximum incremental reactivity (MIR) of acetaldehyde simulated with the modified MCM is 4.0 ppb ppb-1 without considering the effect of other VOCs.     

Study of diclofenac removal by the application of combined zero-valent iron and calcium peroxide nanoparticles in groundwater

Diclofenac(DCF) is one of the most frequently detected pharmaceuticals in groundwater, posing a great threat to the environment and human health due to its toxicity. To mitigate the DCF contamination,experiments on DCF degradation by the combined process of zero-valent iron nanoparticles(nZVI) and nano calcium peroxide(nCaO_2) were performed. A batch experiment was conducted to examine the influence of the adding dosages of both nZVI and nCaO_2 nanoparticles and pH value on the DCF removal.In the meantime, the continuous-flow experiment was done to explore the sustainability of the DCF degradation by jointly adding nZVI/nCaO_2 nanoparticles in the reaction system. The results show that the nZVI/nCaO_2 can effectively remove the DCF in the batch test with only 0.05 g/L nZVI and 0.2 g/L nCaO_2 added, resulting in a removal rate of greater than 90% in a 2-hour reaction with an initial pH of 5. The degradation rate of DCF was positively correlated with the dosage of nCaO_2, and negatively correlated with both nZVI dosage and the initial pH value. The order of significance of the three factors is identified as pH value nZVI dosage nCaO_2 dosage. In the continuous-flow reaction system, the DCF removal rates remained above 75% within 150 minutes at the pH of 5, with the applied dosages of 0.5 g/L for nZVI and 1.0 g/L for nCaO_2. These results provide a theoretical basis for the nZVI/nCaO_2 application to remove DCF in groundwater.