Migration of Some Elements and Radionuclides across aGranite-Granite Contact Zone: A Natural Analoguefor Safe Disposal of High-Level Radwastes

Abstract Elements and natural radionuclides in the contact zone of two granites with different ages would migrate from one to the other because of the difference in their chemical contents and later water-rock interactions. This migration could serve as an analogue for the near-field process of radwastes in a high-level radwaste deep geological disposal repository.

Petrology of an Arc-Oceanic Crust Contact Zone in the Laohushan Back-arc Basin, the Eastern Section of the North Qilian Mountains, NW China

A contact zone sandwiched between an arc and an oceanic crust was discoveredin the Laohushan area in the present study. It consists of a series of north-dipping imbricatedthrust sheets and is exposed on the surface as a narrow arcuate belt, which extends for about 30 kmin an E-W direction and measures about 1-3 km wide. Lithologically, it can be divided into foursubzones. Subzone 1 consists of meta-andesite and metasandstone; subzone 2, psammitic schists;subzone 3, psammitic and pelitic schists, quartz diorite and hornfelses; and subzone 4, metagabbro,epidote amphibolite and pelitic schists. The metamorphism has the following grading sequence: lowgreenschist facies in subzone 1 - > high greenschist facies in subzone 2 - > low amphibolite fadesin subzone 3 - > epidote amphibolite facies in subzone 4. Petrographic and geochemical evidenceshows that rocks in subzones 1, 2 and 3 are arc rocks, whereas those of subzone 4 are oceaniccrustal rocks. The metamorphic mineral assemblages and especially mineral chemistry of the bluishgreen amphibole from the pelitic schists and epidote amphibolite of subzone 4 suggest that the rocksof the contact zone were metamorphosed at a pressure of up to 0.69 GPa. It is thought that theLate-Mid Ordovician oceanic lithosphere of a back-arc basin was underthrust northerly beneath an arcto a depth of 20-23 km, where the basaltic rocks and gabbro were converted to epidote amphiboliteand metagabbro respectively. Then, the root rocks of the arc and these metamorphosed oceanic rockswere brought up to shallower depths by thrust faults to form a contact zone between the arc and theoceanic crust in the Laohushan area.

IMPROVED COHESIVE ZONE MODEL AND ITS APPLICATION IN INTERFACE CONTACT ANALYSIS

An improved interface cohesive zone model is developed for the simulation of interface contact, under mixed-mode loading. A new debonding initiation criterion and propagation of debonding law, taking into account the pressure stress influence on contact shear strength, is proposed. The model is implemented in a finite-element program using subroutine VUINTER of ABAQUS Explicit. An edge-notch four-point bending process and laminated vibration damping steel sheet punch forming test are simulated with the improved model in ABAQUS Explicit. The numerical predictions agree satisfactorily with the corresponding experimental results.

A wide hybrid zone mediated by precipitation contributed to confused geographical structure of Scutiger boulengeri

Confused geographical structure of a population and mitonuclear discordance are shaped by a combination of rapid changes in population demographics and shifts in ecology.In this study,we generated a time-calibrated phylogeny of Scutiger boulengeri,an endemic Xizang alpine toad occurring in mountain streams on the Qinghai-Xizang(Tibet)Plateau(QTP).Based on three mitochondrial DNA(mt DNA)genes,eight clades were assigned to three deeply divergent lineages.Analysis of nuclear DNA(nu DNA)genes revealed three distinct clusters without geographic structure,indicating significantly high rates of gene flow.Coalescent theory framework analysis(approximate Bayesian computation model DIYABC and Migrate-N)suggested that divergence of the main intraspecific clusters was the result of hybridization after secondary contact in the Holocene around 0.59 million years ago(Ma).The ratio of mt DNA FST(fixation index)to nu DNA FST was 2.3,thus failing to show male-biased dispersal.Geographic cline analysis showed that a wide hybrid zone was initially established in southwestern China,without significant reproductive isolation but with strong introgression in S.boulengeri,suggesting high hybrid fitness.Furthermore,mt DNA genes exhibited isolation by distance(IBD)while nu DNA genes exhibited significant isolation by environment(IBE).Results suggested that mitonuclear discordance may have initially been caused by geographic isolation,followed by precipitation-mediated hybridization,producing a wide hybrid zone and geographic structure confusion of nu DNA genes in S.boulengeri.This study indicated that complicated historical processes may have led to specific genetic patterns,with a specific climate factor facilitating gene flow in the system.

Formation process of liquid in interface of Ti/Cu contact reaction couple

By using the Ti/Cu contact reaction couples, the dissolution behavior of Ti and Cu in the eutectic reaction process was investigated under different conditions. The results show that the formation of eutectic liquid phase has a directional property, i.e. the eutectic liquid phase forms first at the Cu side and then spreads along the depth direction of Cu. The width of the eutectic liquid zone when Ti is placed on Cu is wider than that when Ti is placed under Cu. The shape of the upside liquid zone is wave-like. This phenomenon indicates that the formation process and spreading behavior in the upside are different from those in the underside, and there exists void effect in the Cu side of underside liquid zone, this will result in the delaying phenomenon of the contact reaction between Ti and Cu, and distinctly different shapes of the both liquid zones. The formation process of Ti/Cu eutectic liquid zone is similar to that of the traditional solid-state diffusion layer, and the relationship between the width of liquid zone and holding time obeys a square root law.

Factors Controlling the Extent of Contact Metamorphic Aureoles as Deduced by Field Evidence in the Western Alps

The shallow Biella and Traversella late-orogenic plutons are intruded in the Sesia Lanzo Zone(SLZ) the innermost structural element of the Western Alpine arc,a continental unit that records a pervasive metamorphic imprint related to the Alpine subduction. The country rocks consist of metapelites with minor metagranitoids,meta-aplites,metabasites and marbles. The pre-intrusive pervasive metamorphic imprint developed under eclogite facies conditions. The ductile syn-metamorphic deformation

Contact dynamics of elasto-plastic thin beams simulated via absolute nodal coordinate formulation

Under the frame of multibody dynamics, the contact dynamics of elasto-plastic spatial thin beams is numerically studied by using the spatial thin beam elements of absolute nodal coordinate formulation（ANCF）. The internal force of the elasto-plastic spatial thin beam element is derived under the assumption that the plastic strain of the beam element depends only on its longitudinal deformation.A new body-fixed local coordinate system is introduced into the spatial thin beam element of ANCF for efficient contact detection in the contact dynamics simulation. The linear isotropic hardening constitutive law is used to describe the elasto-plastic deformation of beam material, and the classical return mapping algorithm is adopted to evaluate the plastic strains. A multi-zone contact approach of thin beams previously proposed by the authors is also introduced to detect the multiple contact zones of beams accurately, and the penalty method is used to compute the normal contact force of thin beams in contact. Four numerical examples are given to demonstrate the applicability and effectiveness of the proposed elasto-plastic spatial thin beam element of ANCF for flexible multibody system dynamics.

考虑土石坝坝基接触带性能演化的渗流稳定分析

为分析土石坝在渗流及变形长期作用下坝基接触带性能及变化规律,基于水力耦合的分析方法,以某水库工程不同时期得到的坝基和坝基接触带渗透系数,建立土石坝坝基接触带渗透性能与力学参数演化模型,把握坝体及坝基材料物理力学特性、渗透特性的演化规律,对水库长期处于正常蓄水位情况下的渗流场及应力场进行分析。研究表明,由于水流的长期渗流作用,导致坝基接触带中的土壤流失,渗透系数增大,进而导致通过坝坡面、两岸山体的渗漏量增大。考虑水力耦合对坝体变形稳定的影响,研究发现,在水库运行期间,坝基接触带的强度是不断降低的,接触带的屈服区增加,变形量不断增大,安全系数随运行时间的增加不断降低。

地铁受电弓动态包络线分析及应用

[目的]地铁供电系统中,接触网的安全运行高度依赖于合理的受电弓动态包络线设计。然而,当前行业内尚未就受电弓动态包络线的确定方法和参数达成统一标准,因此,深入研究受电弓在不同速度等级下的参数确定问题显得尤为重要。[方法]分析了现有规范中关于动态包络线的定义,并指出了这些定义在地铁领域应用时存在的不明确性。通过对欧洲和德国标准中受电弓摆动量的数学模型进行深入分析,并结合地铁接触网设计的实际参数,提出了一种估算地铁受电弓在不同运行条件下最大横向摆动量的方法。[结果及结论]我国地铁受电弓动态包络线标准的缺失对接触网的设计安全性、施工及检修等环节均产生了重要影响。鉴于此,期望在“十四五”期间,通过行业协会、车辆制造商、设计单位和施工单位等多方面的协同努力,结合标准地铁列车的开发工作,能够制定出统一且准确的受电弓动态包络线标准,以推动轨道交通行业的高质量发展。

基于接触区域自适应调整的圆弧头立铣刀后刀面磨削轨迹精确计算方法

为保证圆弧头立铣刀后刀面的加工精度,提出一种基于接触区域自适应调整的圆弧头立铣刀后刀面磨削轨迹精确计算方法。通过圆弧头立铣刀结构特征分解构建了后刀面的数学模型;通过计算砂轮和后刀面之间的磨削接触区域,自适应修正砂轮姿态,避免磨削干涉,实现了后刀面几何参数控制的准确性和一致性,并保证了曲面的光滑连接。最后,在VC++平台算法模块开发的基础上,通过加工仿真和磨削试验验证了该算法的有效性。

4~5 K铟片填充下无氧铜材料接触热阻实验研究

在陆续开展的深空探测任务中,高精度光学探测设备需要长期稳定的深低温工作环境。传热界面由于传热介质的热阻而存在一定的传热温差,为确保设备的工作环境,避免探测效率下降、精度下降和噪声干扰增加等严重后果,对无氧铜和不锈钢两种深低温温区常用的固体导热材料的界面接触热阻进行了实验测试。在真空、4~5.2 K、压力为3 077 N、铟片为填充物的条件下,测量了粗糙度为Ra=3.2的不锈钢-无氧铜接触热阻。结果表明:无氧铜界面间接触热阻在10^(-5)~10^(-4) m^(2)·K/W量级,且随温度的升高和粗糙度的减小而减小;无氧铜和不锈钢间的接触热阻在10^(-2) m^(2)·K/W量级。

湘东明月峰地区金管冲铀矿床沥青铀矿电子探针U Th Pb化学定年及其地质意义

金管冲铀矿床位于湘东明月峰地区,属花岗岩外接触带型铀矿床,主要铀矿化类型为沥青铀矿方解石和沥青铀矿微晶石英萤石。为厘定金管冲地区的铀成矿时代与成矿期次,开展了详细的野外地质调查、岩相学、电子探针化学分析以及U Th Pb化学定年研究。结果表明,两类沥青铀矿的UO_(2)含量高、PbO与SiO_(2)含量低,且w(CaO)与w(UO_(2)+PbO)、w(SiO_(2)+CaO+FeO)与w(PbO)以及沥青铀矿年龄均无明显相关性,表明沥青铀矿形成时较为稳定,受后期改造作用影响弱。金管冲铀矿床中沥青铀矿方解石型铀矿化加权平均年龄为(90.7±3.2)Ma(MSWD=1.9,n=17),沥青铀矿微晶石英萤石型铀矿化加权平均年龄为(70.1±2.4)Ma(MSWD=2.1,n=20),显示该矿床在晚白垩世至少经历了两阶段的铀成矿作用。综合前人已有数据,认为金管冲铀矿床铀成矿作用与华南岩石圈拉张减薄事件较为吻合,可能是古太平洋板块俯冲后的产物。

电磁调控轧辊的热力胀形行为及高效控制方法

为研究辊形电磁调控技术(roll profile electromagnetic control technology,RPECT)的热力胀形行为,采用有限元方法分析了不同电流密度及频率下综合辊凸度、热力贡献辊凸度以及力凸度占比等随接触区热量的变化规律,探究了接触区热量与热力胀形能力的映射关系及其成立条件.结果表明,在接触区热量的中低取值范围内,同一接触区热量所对应的热力调控能力不会受磁参数影响,故提出将接触区热量作为输入参数与调控能力之间桥梁的RPECT高效控制策略.该策略通过提升磁参数来快速达到接触区的目标温升效果,进而获取目标调控能力.以20μm的辊缝凸度需求为例,经原始与高效控制策略间的对比发现,新策略的调控时间可有效地缩短至原调控时间的19.57%.

水利工程异常地质体地球物理探测分析与应用

水利工程建设中常见对工程危害较大的破碎带、蚀变带、岩性接触带、岩溶等异常地质体,查明异常地质体的空间分布尤为重要。本文通过分析其地球物理参数特征,提出了采用基于电性参数、弹性参数差异为基础的高密度电法、瞬变电磁法、孔内声波测试等地球物理方法进行探测的工作思路,并在白龙江引水工程、广西长塘水库工程中加以应用,查明了各异常地质体的分布范围及地球物理参数特征,取得了良好效果,为工程建设发挥了重要作用。

下庄矿田花岗岩外接触带型铀矿化特征及找矿标志

外接触带型铀矿床是花岗岩型铀矿床的一种重要类型,文章通过研究下庄矿田东部地区外接触带的地质、物探特征并结合区内铀矿勘查成果,归纳总结了下庄矿田花岗岩外接触带型铀矿化特征及控矿因素,提出下庄矿田花岗岩外接触带型铀矿化严格受“岩性界面、构造、热液蚀变”三位一体控制,而花岗岩体与寒武纪地层的接触界面、强烈的构造运动、叠加发育的多种热液蚀变以及放射性异常点带是主要的找矿标志,同时文章研究认为竹园头地区具有与新桥东、坪田矿床相似的成矿地质条件和铀矿化特征,并在找矿标志集中部位通过钻探揭露获取了很好的工业铀矿化,表明竹园头地区是进一步铀矿勘查的重点区域。

高水平应力矿岩接触带巷道稳定性分析

井下巷道在通过矿岩接触带时,由于接触带两侧岩性差异会在巷道两端和接触带上产生不同的变形和破坏。以杜达铅锌矿100 m中段矿岩接触带巷道为研究对象,采用Flac3D软件数值模拟和现场巷道收敛变形监测的方法,分析矿岩接触带巷道在未支护情况下的应力分布和变形情况,得出杜达铅锌矿在高水平应力下矿岩接触带巷道的变形和破坏规律。研究结果表明:高水平应力下矿岩接触带巷道形成后的破坏以剪切破坏为主,巷道变形和破坏在顶底板表现较为明显。矿岩接触带上剪切应力集中,使得接触带两侧矿(岩)体的变形存在明显的不对称非协调分布。岩体侧的变形破坏比矿体侧更为明显,且巷道两帮变形小于顶底板变形。研究结果可为类似条件下矿岩接触带巷道的支护提供理论依据。

新疆托克逊县彩花沟钨铜硫铁矿地质特征及成因分析

彩花沟矿区域上属塔里木板块与准噶尔板块缝合带南侧,钨铜矿体赋存于泥盆系下统阿尔彼什麦布拉克组下亚组第二岩性段(D_(1)a^(a-2))与华力西晚期二云二长花岗岩外接触带及其外侧150米范围内的似层状矽卡岩中,矿体受火山喷流沉积层状-似层状矽卡岩的控制,受岩体侵位接触交代矽卡岩化的迭加,为沉积改造型钨铜硫铁矿;属火山喷发沉积-区域变质改造-接触交代变质叠加形成钨铜硫铁矿床。

宁都县上横铀矿地质特征及控矿因素分析

上横铀矿位于江西省宁都县,是近年来江西省核地质工作少数取得突破的地区之一。该矿床所处的桃山铀矿田中,大多矿床为产于复式岩体内部的碎裂蚀变岩型,但上横铀矿产于岩体外接触带的区域断裂中,为花岗岩外带型,成矿规律与控矿因素的认识略有欠缺。本文利用野外专项地质测量、槽探、钻探揭露等手段,初步查明铀成矿条件和控矿因素,为今后该类型铀找矿提供新思路。研究认为,在成矿、容矿和保矿过程中,桃山复式岩体、南华系地层、红盆、上横断裂、脆性构造岩以及韧性构造岩等因素在不同程度上起到作用。

三维实景模型在水库高边坡稳定性初步分析中的应用

三维实景模型以地质三维模型、倾斜模型为基础,建立开挖后实景地质模型、效果模型。本文以恒山水库大坝右岸高边坡稳定性分析为例,结合现场地质测绘、调查以及无人机仿地飞行等方法对高边坡展开勘测工作,初步查明高边坡主要地层分布、断层和裂隙发育情况、危岩体分布等,对边坡整体及局部稳定进行初步评价。通过该方法的运用,大大缩短了外业测绘周期,降低了安全风险,增强了工作的针对性、目的性,提高了正向设计质量,简化了各模型基础工作,以期对类似工程具有一定参考意义。

粤北下庄矿田坪田花岗岩外接触带型铀矿找矿潜力预测

粤北下庄铀矿田坪田花岗岩外接触带型铀矿床,矿体主要赋存于粤北贵东岩体的外接触带变质砂岩中,受北北东向构造、热液活动、岩性及接触带共同控制。运用流体包裹体测温测试分析方法,对该地区铀矿体成矿期均一温度和流体盐度进行测试,测试结果:含铀包裹体均一温度范围为150.0℃~252.0℃,流体盐度为0.411~4.857 wt%NaCl eqv,属于中低温、低盐度活动范围。坪田地区热液活动具有多期次性、含矿构造发育、围岩蚀变强烈及低温、低盐度的含矿流体特征,是铀成矿有利的地质条件,也是下庄铀矿田开展花岗岩外带型铀矿找矿潜力较大的重要地区之一。