陕西商丹陈家庄铀矿区花岗岩体和伟晶岩脉的U-Pb年龄、地球化学特征与铀成矿作用

陕西陈家庄铀矿床是我国北秦岭商州—丹凤伟晶岩型铀矿集区中一个重要的矿床,铀矿体均产于加里东期花岗岩体周边花岗伟晶岩脉与围岩(秦岭群变质杂岩)的接触部位。本文对矿区花岗岩体、花岗伟晶岩脉开展了详细的岩石学、岩石地球化学、锆石U-Pb年代学研究,进而对其成因、成岩构造环境和铀矿化机理进行了探讨。LA-ICP-MS锆石U-Pb年代学研究表明,黄龙庙黑云母花岗岩体,陈家庄二长花岗岩体和非矿、贫矿、富矿花岗伟晶岩脉的成岩年龄分别为(446±3) Ma、(419±2) Ma、(417±3) Ma、(414±4) Ma和(416±3) Ma。地球化学分析显示：黄龙庙黑云母花岗岩体具有Ⅰ型花岗岩、埃达克质岩特征,源自加厚下地壳的部分熔融,形成于块体碰撞构造环境;陈家庄二长花岗岩体也具有I型花岗岩特征,但源区深度略浅,形成于碰撞后的减压环境。花岗伟晶岩脉与陈家庄二长花岗岩体近于同时形成,且具有亲缘性。铀矿物及富铀黑云母均产于花岗伟晶岩脉中。对比研究揭示,非矿、贫矿、富矿花岗伟晶岩脉地球化学特征和铀赋存状况的差异由同化混染作用程度高低所致。在花岗伟晶岩脉与秦岭群变质杂岩的接触部位,同化混染作用较弱的部位形成的二云母花岗伟晶岩脉仅具有弱的铀富集,同化混染作用较强的部位所形成的富石英、黑云母花岗伟晶岩脉则高度富集铀且构成铀矿体。综合研究表明,花岗伟晶岩脉成岩期后的同化混染作用是铀富集成矿的主导因素。     

锡多金属矿床类型,成矿系列及成矿模式

在研究锡多金属矿床的主要控矿因素、成矿物质来源、主岩特征,地质环境、矿石建造和成矿作用特点后,将其矿床划分为岩控型、双控型和层控型3大类15个亚类;并对近年来找矿勘探工作中有突破性进展的花岗岩型、重熔斑岩型和同熔斑岩型矿床进行了详细地论述.在研究成矿物质来源、成矿作用问有机联系、矿床成因和矿床问规律分布的关系后,将锡多金属矿床划分为深源同熔岩浆、浅源重熔岩浆、双控、层控4个成矿系列,阐述了各成矿系列的综合特征;并分别建立了其成矿模式.     

辽宁杨木杆硼矿床地质地球化学特征

杨木杆硼矿位于辽宁省宽甸县,产出于古元古代南辽河群下部里尔峪岩组中,为一中型硼镁石型硼矿。矿体走向ＳＥ,倾向ＮＥ,倾角７０°～８０°,直接赋矿岩石为蛇纹岩、蛇纹石化大理岩,矿体顶板出现有热水沉积的电英岩。硼矿石主要由纤维硼镁石、板状硼镁石及蛇纹石、白云石等组成。常见的变余沉积及变质、交代等组构。硼矿石品位Ｂ２Ｏ３随ＭｇＯ含量增长先是稳步增长,然后在Ｂ２Ｏ３含量大于７％时,ＭｇＯ含量稳定在４５％～４８％范围内。矿石中富含Ｃｓ、Ｎｄ、Ｔａ、Ｓｎ、Ｃｄ等微量元素及Ｆ、ＣＨ４等挥发分,稀土总量从５．７３×１０－６～７０．９８×１０－６,具Ｅｕ负异常。δ１３Ｃ在－２．６‰～－１０．４‰,δ１１Ｂ在９．６‰～１１．１‰。杨木杆硼矿为受变质的与深源火山活动有关的热水沉积矿床,同时存在的蒸发气候条件提高了硼富集成矿的效率。     

从华北陆块南缘大洋扩张到北秦岭造山带板块俯冲的转换时限

本文以北秦岭造山带华北陆块南缘被动陆缘火山裂谷(大洋?)盆地、早古生代岛弧-弧后盆地和晚古生代岛弧-蛇绿杂岩等构造相带为研究重点,综合利用同位素年代学、古生物年代学、岩石学、岩石地球化学和同位素地球化学等实测数据,系统研究和探讨了北秦岭造山带被动陆缘大洋扩张向俯冲增生造山转换的时限.研究显示:华北陆块南缘由晚新元古代大洋扩张作用转化为板块俯冲作用的转换时限为早奥陶世,约472Ma左右.北秦岭造山带在古生代期间至少存在两期板块俯冲增生造山作用,时代上向南变新,空间上向南向洋内迁移.两次俯冲增生造山作用分别构筑了北秦岭造山带早古生代岛弧-弧后盆地和晚古生代岛弧-俯冲杂岩两条构造相带.     

香花岭锡多金属矿田成矿地质条件及矿床成因探讨

在研究香花岭锡多金属矿田内地质构造、赋矿地层及含锡花岗岩发育特征及其控矿作用后、认为赋矿地层具有成矿物质初始富集特征:花岗岩属于具高难度、适度富碱、贫钙镁铁.富合面矿元素和挥发组分、高度分异演化的陆壳重熔花岗岩、成矿性良好.总结了区内主要类型的锡多金属矿床基本地质特征,重点阐述了本区新发现的斑岩锡矿床地质特征.根据矿化富集与地层和花岗岩体的时空关系,锡石矿物地球化学特征,矿床稀土地球化学特征,矿物包裹体成分统计分析等最新研究成果,提出了锡多金属矿床的地层—花岗岩的“双控”成因.     

Characterisation of rock aggregate breakage properties using realistic texture‐based modelling

Realistic texture‐based modelling methods, that is microstructural modelling and micromechanical modelling, are developed to simulate the rock aggregate breakage properties on the basis of the rock actual microstructure obtained using microscopic observations and image analysis. The breakage properties of three types of rocks, that is Avja, LEP and Vandle taken from three quarries in Sweden, in single aggregate breakage tests and in inter‐aggregate breakage tests are then modelled using the proposed methods. The microstructural modelling directly integrates the microscopic observation, image analysis and numerical simulation together and provides a valuable tool to investigate the mechanical properties of rock aggregates on the basis of their microstructure properties. The micromechanical modelling takes the most important microstructure properties of rock aggregates into consideration and can model the major mechanical properties. Throughout this study, it is concluded that in general, the microstructure properties of rock aggregate work together to affect their mechanical properties, and it is difficult to correlate a single microstructure property with the mechanical properties of rock aggregates. In particular, for the three types of rock Avja, LEP and Vandle in this study, crack size distribution, grain size and grain perimeter (i.e. grain shape and spatial arrangement) show good correlations with the mechanical properties. The crack length and the grain size negatively affect the mechanical properties of Avja, LEP and Vandle, but the perimeter positively influences the mechanical properties. Besides, the modelled rock aggregate breakage properties in both single aggregate and inter‐aggregate tests reveal that the aggregate microstructure, aggregate shape and loading conditions influence the breakage process of rock aggregate in service. For the rock aggregate with the same microstructure, the quadratic shape and good packing dramatically improve its mechanical properties. During services, the aggregate is easiest to be fragmented under point‐to‐point loading condition, and then in the sequence of multiple‐point, point‐to‐plane and plane‐to‐plane loading conditions. Copyright © 2011 John Wiley & Sons, Ltd.     

设有圈梁与构造柱的砌体结构预应力筋抗震加固试验研究

通过对设有圈梁与构造柱的砌体结构采用体外预应力筋加固和未加固模型进行双向拟动力试验,对墙体裂缝开展、结构耗能、结构损伤等指标进行对比分析,探讨体外预应力筋加固对砌体结构抗震能力的影响.试验结果表明:体外预应力筋产生的约束力对限制裂缝开展、防止圈梁与预制楼板的脱空效果明显砌体结构在体外预应力筋加固后的总滞回耗能大于未加固...     

鄱阳湖流域降水变化及其与太阳黑子的关系

基于鄱阳湖流域1961―2000年的降水栅格数据和太阳黑子相对数数据,采用滑动平均、一元线性回归、Mann-Kendall检验等方法对鄱阳湖流域1961―2000年降水特征进行了分析;采用小波分析方法探讨鄱阳湖流域降水变化规律与太阳黑子的可能联系。结果表明:1961―2000年鄱阳湖流域降水量呈增加趋势,并在1996年发生突变。通过小波分析发现鄱阳湖流域降水主周期为10 a,与太阳黑子活动周期相同,且两者的小波方差系数达到0.86。在1996年发生突变之前,降水量在太阳黑子活动的上升期比下降期小,鄱阳湖流域降水周期变化与太阳黑子活动有一定联系。     

皖南花山石窟群开凿年代地衣测年及成因

据在花山石窟地区古代桥梁、桥垛、牌坊、墓碑、古民居、古房基和石窟洞壁洞口量测出的96个黄绿地图衣最人内切圆直径，测定出花山石窟主要开采年代为距今515～370年即明代中晚期(公元1477～1632年间)，石窟岩性与周边地区古建筑岩性的比较以及史料记载和石窟中遗留的古代瓷器残片年代均能证明这一点。鉴于石窟地衣量测工作主要在石窟洞口进行，由此推测石窟深处开采时代可能延续至清代。     

A case study on key techniques for long-distance sea-crossing shield tunneling

Abstract

The Zhanjiang Bay Sea-crossing Tunnel is the first phase of an ambitious plan of the Golden Triangle Economic Zone in southwestern China and passes underneath the deepest artificial shipping channel with the highest level in Asia. The tunnel is a world-record extralong and small-diameter corridor constructed using an uninterrupted single-end shield tunneling method in subsea soft ground under ultrahigh hydraulic pressure for water conveyance. This case study first highlights the engineering challenges of constructing the sea-crossing shield tunnel in subsea soft ground under ultrahigh hydraulic pressure. A series of key techniques are then investigated and some innovations are proposed to address the engineering challenges in the following four key aspects of the sea-crossing shield tunneling process: (a) optimal design of segmental linings; (b) adaptive reformation of the shield machine; (c) structural construction of deep vertical shafts; and (d) supporting techniques of long-distance advancing. On the basis of the field monitoring and numerical analyses, it is concluded that the implemented key techniques ensure the successful management and control of the engineering challenges in terms of optimizing the segmental lining, selecting the shield machine and constructing the vertical working shaft during the sea-crossing shield tunneling process with limited geological investigation data available under submarine conditions.