Rationales behind irrationality of decision making in groundwater quality management

This issue paper presents how certain policies regarding management of groundwater quality lead to unexpected and undesirable results, despite being backed by seemingly reasonable assumptions. This happened in part because the so-called reasonable decisions were not based on an integrative and quantitative methodology. The policies surveyed here are: (1) implementation of a program for aquifer restoration to pristine conditions followed, after failure, by leaving it to natural attenuation; (2) the "Forget About The Aquifer" (FATA) approach, while ignoring possible damage that contaminated groundwater can inflict on the other environmental systems; (3) groundwater recharge in municipal areas while neglecting the presence of contaminants in the unsaturated zone and conditions exerted by upper impervious surfaces; (4) the Soil Aquifer Treatment (SAT) practice considering aquifers to be "filters of infinite capacity"; and (5) focusing on well contamination vs. aquifer contamination to conveniently defer grappling with the problem of the aquifer as a whole. Possible reasons for the failure of these seemingly rational policies are: (1) the characteristic times of processes associated with groundwater that are usually orders of magnitude greater than the residence times of decision makers in their managerial position; (2) proliferation of improperly trained "groundwater experts" or policymakers with sectoral agendas alongside legitimate differences of opinion among groundwater scientists; (3) the neglect of the cyclic nature of natural phenomena; and (4) ignoring future long-term costs because of immediate costs.     

Geochemistry and Petrogenesis of Late Ediacaran Rare-metalAlbite Granites of the Arabian-Nubian Shield

The Abu Dabbab albite granite(ADAG), in the central Eastern Desert of Egypt, hosts the most significant rare metal ore deposit in the northern part of the Neoproterozoic Arabian-Nubian Shield. Here, we report detailed field,petrographic, mineralogical and geochemical investigation of the ADAG, an isolated stock-like granitic body with sharp intrusive contacts against metamorphic country rocks, probably emplaced at about 600 Ma. The fine-grained porphyritic upper unit is a preserved remnant of the shallowly-emplaced apex of the magma chamber, whereas the medium-grained lower unit crystallized at deeper levels under subvolcanic conditions. The peraluminous leucocratic ADAG shares common geochemical characteristics with post-collisional intraplate A-type magmas. In addition to the conspicuous enrichment in Na2 O, the ADAG is remarkable for its anomalous concentrations of Ta, Nb, Li, Hf, Ga, Sn, Zn and heavy rare-earth elements. Nb-Ta minerals in the ADAG are mixed with Fe-Mn oxides, forming black patches that increase in abundance toward of the base of the intrusion. Columbite-tantalite, cassiterite and wolframite are the most important ore minerals.Pronounced negative Eu anomalies(Eu/Eu* = 0.10–0.24) reflect extreme magmatic fractionation and perhaps the effects of late fluid-rock interaction. The ADAG was most likely generated by partial melting of the juvenile middle crust of the ANS as the geotherm was elevated by erosional uplift following lithospheric delamination and it was emplaced at the intersection of lineations of structural weakness. Although formation of the ADAG and its primary enrichment in rare metals are essentially due to magmatic processes, late-stage metasomatism caused limited redistribution of rare metals. Fluid-driven subsolidus modification was limited to the apex of the magma chamber and drove development of greisen, amazonite, and quartz veins along fracture systems.     

Application of soft computing techniques for shallow foundation reliability in geotechnical engineering

This research focuses on the application of three soft computing techniques including Minimax Probability Machine Regression(MPMR),Particle Swarm Optimization based Artificial Neural Network(ANN-PSO)and Particle Swarm Optimization based Adaptive Network Fuzzy Inference System(ANFIS-PSO)to study the shallow foundation reliability based on settlement criteria.Soil is a heterogeneous medium and the involvement of its attributes for geotechnical behaviour in soil-foundation system makes the prediction of settlement of shallow a complex engineering problem.This study explores the feasibility of soft computing techniques against the deterministic approach.The settlement of shallow foundation depends on the parametersγ(unit weight),e0(void ratio)and CC(compression index).These soil parameters are taken as input variables while the settlement of shallow foundation as output.To assess the performance of models,different performance indices i.e.RMSE,VAF,R^2,Bias Factor,MAPE,LMI,U(95),RSR,NS,RPD,etc.were used.From the analysis of results,it was found that MPMR model outperformed PSO-ANFIS and PSO-ANN.Therefore,MPMR can be used as a reliable soft computing technique for non-linear problems for settlement of shallow foundations on soils.     

Identification of Milankovitch Cycles and Calculation of Net Primary Productivity of Paleo-peatlands using Geophysical Logs of Coal Seams

Individual coal seams formed in paleo-peatlands represent sustained periods of terrestrial carbon accumulation and a key environmental indicator attributed to this record is the rate of carbon accumulation. Determining the rate of carbon accumulation requires a measure of time contained within the coal. This study aimed to determine this rate via the identification of Milankovitch orbital cycles in the coals. The geophysical log is an ideal paleoclimate proxy and has been widely used in the study of sedimentary records using spectral analysis. Spectral analyses of geophysical log from thick coal seams can be used to identify the Milankovitch cycles and to calculate the period of the coal deposition. By considering the carbon loss during coalification, the long-term average carbon accumulation rate and net primary productivity (NPP) of paleo-peatlands in coal seams can be obtained. This review paper presents the procedures of analysis, assessment of results and interpretation of geophysical logs in determining the NPP of paleo-peatlands.     

深海碎屑岩层序地层学50年(1970—2020)重要进展

层序地层学是当前地球科学研究颇为关注的领域,被广泛应用于沉积盆地分析和油气勘探.碎屑岩层序地层学理论方法源于海相盆地,是在被动大陆边缘油气勘探实践的基础上凝练而来的,至今已经历了约50年的发展历程.本文梳理了深海碎屑岩层序过去50年发展历程中的重要进展(包括1970—2000年的经典海相碎屑岩层序地层学、2000—20...     

Improved prediction of clay soil expansion using machine learning algorithms and meta-heuristic dichotomous ensemble classifiers

Soil swelling-related disaster is considered as one of the most devastating geo-hazards in modern history.Hence,proper determination of a soil’s ability to expand is very vital for achieving a secure and safe ground for infrastructures.Accordingly,this study has provided a novel and intelligent approach that enables an improved estimation of swelling by using kernelised machines(Bayesian linear regression(BLR)&bayes point machine(BPM)support vector machine(SVM)and deep-support vector machine(D-SVM));(multiple linear regressor(REG),logistic regressor(LR)and artificial neural network(ANN)),tree-based algorithms such as decision forest(RDF)&boosted trees(BDT).Also,and for the first time,meta-heuristic classifiers incorporating the techniques of voting(VE)and stacking(SE)were utilised.Different independent scenarios of explanatory features’combination that influence soil behaviour in swelling were investigated.Preliminary results indicated BLR as possessing the highest amount of deviation from the predictor variable(the actual swell-strain).REG and BLR performed slightly better than ANN while the meta-heuristic learners(VE and SE)produced the best overall performance(greatest R2 value of 0.94 and RMSE of 0.06%exhibited by VE).CEC,plasticity index and moisture content were the features considered to have the highest level of importance.Kernelized binary classifiers(SVM,D-SVM and BPM)gave better accuracy(average accuracy and recall rate of 0.93 and 0.60)compared to ANN,LR and RDF.Sensitivity-driven diagnostic test indicated that the meta-heuristic models’best performance occurred when ML training was conducted using k-fold validation technique.Finally,it is recommended that the concepts developed herein be deployed during the preliminary phases of a geotechnical or geological site characterisation by using the best performing meta-heuristic models via their background coding resource.     

象牙海岸Issia地区铌钽砂矿的研究(英文)

在西非的象牙海岸Issia地区分布着许多铌钽矿床,包括原生矿和砂矿。原生矿产在分带很好的伟晶岩中。这个地区发育着许多花岗岩和花岗伟晶岩。伟晶岩可分为:(1)分异不好的伟晶岩,无矿化;(2)含Be伟晶岩,分带较好,见绿柱石;(3)含Be-Nb-Ta的伟晶岩,分带很好,是矿体;(4)Be-Nb-Ta-Li伟晶岩,分带很好,是矿体。除了10多个原生矿外,还有许多砂矿。砂矿有两种类型:一种近原生矿的坡积砂矿,另一种是经河流冲刷搬运后的冲积砂矿。我们选择了Etienne-Meguhe砂矿作为近原生矿的坡积砂矿的代表,Bemadi矿作为河流冲积型的砂矿的代表,对这两种类型的砂矿的风化、搬运、沉积机理进行了比较研究。研究发现不同的搬运距离和搬运模式对铌钽砂矿的主要矿物——铌钽铁矿的化学性质没有什么影响,而其物理形态则发生了变化。坡积型砂矿的铌钽铁矿常与石英、长石等矿物连生,其颗粒大小与原生的Nb-Ta伟晶岩中的铌钽铁矿一致;经河流冲积而形成的砂矿中,铌钽铁矿颗粒变小、轮廓变得圆滑,几乎无连生矿物,但矿体集中,常在河流的冲积扇中分布,易开采。     

地壳的拆离作用与华北克拉通破坏:晚中生代伸展构造约束

伸展条件下的地壳拆离作用是岩石圈减薄的重要浅部构造响应。晚中生代时期的伸展构造(包括拆离断层、变质核杂岩构造和断陷盆地)在华北、华南、东北和东蒙古及贝加尔地区普遍发育,它们切过上部地壳(断陷盆地)、中、上地壳(拆离断层)或中部地壳(变质核杂岩)。地壳拆离作用具有运动学极性(NWW或SEE)、几何学宏观(区域)对称与微观(局部)不对称性、遍布全区但不均匀性,以及形成时间的跨越性(140~60Ma)等特点,并使得地壳和岩石圈发生显著的减薄。本文研究揭示出现今岩石圈厚度变化与晚中生代伸展构造的发育程度和分布之间并没有必然的联系。其变化的基本规律是,除新生代裂陷发育区岩石圈厚度明显较小且厚度有迅速变化外,从华北向贝加尔地区总体的变化趋势是逐渐加厚,也即东亚地区岩石圈具有楔形形态。晚中生代时期的地壳(或地幔)拆离作用伴随着广泛的岩石圈减薄作用,区域岩石圈同时遭受到一定程度的减薄和破坏,华北克拉通在这一时期的破坏仅仅是区域岩石圈减薄在华北的具体体现。     

郯庐断裂带张八岭隆起北段的左旋走滑挤压变形及其40Ar/39Ar定年

郯庐断裂带张八岭隆起北段,自西向东分别出露北北东向的韧性滑脱变形带、脆-韧性过渡带和脆性的前陆褶断带。韧性滑脱变形带内的张八岭群片岩,广泛发生了低绿片相背景下的糜棱岩化。其中呈现为平缓的糜棱面理和近南北向的矿物拉伸线理。显微构造及石英C轴组构分析显示,该韧性滑脱带一致为上盘向南的运动。该带以东依次变为上盘向南南东→南东的逆冲活动,总体上为左旋走滑挤压变形带。张八岭群所在的韧性变形带为深部陡立走滑构造与浅部脆性构造之间的滑脱变形带,其间的差异走滑变形,造成了该滑脱层在总体向北运动中出现上盘向南的剪切变形。对6处张八岭群片岩中15个不同粒级白云母的40Ar/39Ar定年指示,变形发生在(236.2±0.5)~(238.0±0.4)Ma的中三叠世晚期。这表明郯庐断裂带的左行平移发生在华北与华南板块碰撞的深俯冲阶段,起源于陆内转换断层。     

岩浆成矿体系的热演化和剥露史的数字模拟

通过对岩浆冷却过程的数字模拟研究,揭示出岩浆在冷却成矿过程中的温度分布和变化规律及影响因素．在此基础上,进一步应用高精度的温龄计组合来限定岩浆成矿体系的热演化和剥露历史,精确地计算出岩浆的初始侵位时间和深度、矿物结晶时间、冷却速率、冷却和暴露地表时间,以及剥露和剥蚀速率等重要参数,并将模拟结果应用于斑岩铜矿床的成矿研究中．研究表明,将精确的年龄测试手段与计算机模拟技术相结合,可为定量研究岩浆矿床的热演化和剥露史、深入了解矿床的成因机制提供一种有效方法．