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1.
本文介绍了全球稀土资源供需历史、现状和对未来的展望。从矿床成因视角切入,将稀土矿床分为内生和外生两大类型,其中内生稀土矿床包括碳酸岩型、碱性岩型、碱性岩型- 碳酸岩型、氧化铁铜金型、热液脉型,外生稀土矿床包括风化壳离子吸附型、沉积岩型、沉积矿产(煤矿、铝土矿和沉积磷矿)伴生型、砂矿和现代海洋底部含稀土的锰结核、结壳和软泥型。归纳总结了主要类型矿床的基本特点和时空分布;认为内生稀土矿床产出于四类构造环境,包括裂谷环境、碰撞后伸展环境、大陆碰撞环境和后俯冲伸展环境;从构造演化入手,探讨了在外生与内生地质过程中稀土元素的迁移和富集规律,建立了涵盖主要矿床类型的构造- 成矿模型。 相似文献
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深基坑排桩—圈梁支护结构协同作用研究 总被引:14,自引:5,他引:14
排桩-圈梁的协同作用对深基坑支护结构的变形和内力有着重要的影响,为此对深基坑排极支护结构进行了弹性地基梁有限元分析,得出一些有意义的结论。 相似文献
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一般剪切带主要由纯剪切和简单剪切共同作用,不同的剪切带及不同的构造位置两者所占有的比例不同。利用运动学涡度(Wk)可以定量地分析两者间的比值大小。本文通过极莫尔圆法和有限应变轴率Rs/石英c轴组构法对冈底斯岩浆带中段谢通门-曲水滑覆型韧性剪切带的运动学涡度进行了计算,两种方法获得了较为一致的结果。通过极莫尔圆法,对剪切带中的9组糜棱岩样品进行了运动学涡度计算,获得了Wk=0.73~0.96,平均值Wk=0.83。运用有限应变轴率Rs/石英c轴组构法对4个样品进行了分析,得到Wk=0.85~0.93,均值为0.88,两种方法获得了较为一致的应变结果。还根据极莫尔圆图解,计算了该韧性剪切带的减薄量S=0.09~0.35,平均减薄量为0.20。研究表明该韧性剪切带为典型的以简单剪切为主伴有部分纯剪切的一般剪切,该剪切带的形成可能与拉萨地体在中新世时从挤压到侧向伸展的转换有关。该剪切带变形特征和运动学涡度的确定深化了对藏南冈底斯地区的构造演化过程的理解,并对青藏高原中南部的地质研究具有推进作用。 相似文献
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Chuanbo Zhou Shiwei Lu Nan Jiang Dingbang Zhang Zhihua Zhang Gaojian Miao 《Geotechnical and Geological Engineering》2016,34(3):847-866
In Daye Iron Mine, the open-pit mining has ended and the underground mining started in 2003. The present pit slopes are as high as 430 m and the slope angle is up to 43°. During the process of open-pit to underground mining, the high-steep pit slopes would be affected by both open-pit mining and underground mining, and its deformation characteristics would become more complex. So in this paper, the trinity method of numerical simulation, model experiment and field test was adopted to analyze the displacement and stress fields systematically. The results show that: (1) Prominent rebound deformation occurs near the slope foot, which is induced by the unloading in open-pit mining. When it is backfilled to 0 m level, the rebound deformation decreases, which indicate that backfilling mass can restrict the deformation and improve the slope stability; (2) Subsidence dominates the slope deformation in open-pit to underground mining and it increases with an increasing elevation of monitoring point; the maximum horizontal displacement occurs in the lower part of the slopes, because the backfilled part is squeezed by both the north slope and the south slope, and it has a lower elastic modulus than the previous orebody; (3) The stress and its variability near the slope foot are much larger than other places, indicating that the slope foot is most affected by stress redistribution and stress concentration may occur here; the stress at other stress monitoring points changes little, indicating that the influence of open-pit to underground mining is local; (4) The effect of underground mining on the deformation of the faults is not prominent; (5) Mining operations in near-ground part affect more on the variation of deformation and stress of pit slopes than that in deeper part. 相似文献
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多主体建模作为研究"人类与自然耦合系统"等复杂适应性系统的重要工具,已经被广泛地应用于水资源管理领域.在调研国内外重要研究的基础上,回顾了多主体建模的基础理论、建模工具和框架,并对多主体建模在城市水资源管理、农业水资源管理和流域水资源综合管理3个方面的研究和应用进行了阶段性总结.针对当前研究的不足和难点,结合我国水资源管理的研究现状,提出以下4个研究重点:①加强主体行为决策规则刻画;②加强模型验证和评估研究;③开展代表性流域多主体建模研究;④推动学科交叉和综合集成研究.多主体建模能够揭示人类活动—水文循环的互馈机制,为水资源及水环境的可持续利用和管理提供政策建议,加强多主体建模在水资源管理领域的研究可为水资源管理提供新的思路,推动我国水资源的可持续发展. 相似文献
8.
Changfeng Liu Zhiguang Zhou Guosheng Wang Chen Wu Hongying Li Shiwei Ma 《地学前缘(英文版)》2021,12(3):101103
The Xingmeng Orogenic Belt evolved through a long-lived orogeny involving multiple episodes of subduction and accretion. However, there is a debate on its tectonic evolution during the Late Paleozoic. Here, we report geochemical, geochronological, and isotopic data from strongly peraluminous granites and gabbro-diorites from the Sunidzuoqi–Xilinhot region. Zircon U–Pb ages suggest that the intrusive rocks were emplaced during the Early Carboniferous (333–322 Ma). The granites exhibit geochemical characteristics similar to S-type granites, with high SiO2 (72.34–76.53 wt.%), Al2O3 (12.45–14.65 wt.%), and A/CNK (1.07–1.16), but depleted Sr, Nb, and Ta contents. They exhibit positive εNd(t) and εHf(t) values (?0.3 to 2.8 and 2.7–5.7, respectively) and young Nd and Hf model ages (TDM2(Nd)=853–1110 Ma and TDM2(Hf)=975–1184 Ma), suggesting that they may be the partial melting products of heterogeneous sources with variable proportions of pelite, psammite, and metabasaltic rocks. The meta-gabbro-diorites from the Maihantaolegai pluton have low SiO2 (47.06–53.49 wt.%) and K2O (0.04–0.99 wt.%) contents, and demonstrate slight light rare earth element (REE) depletion in the chondrite-normalized REE diagrams. They have high zircon εHf(t) values (14.41–17.34) and young Hf model ages (TDM2(Hf)= 230–418 Ma), indicating a more depleted mantle source. The variations of the Sm/Yb and La/Sm ratios can thus be used to assess the melting degree of the mantle source from 5% to 20%, suggesting a quite shallow mantle melting zone. We propose that the petrogenesis and distribution of the strongly peraluminous granites and gabbro-diorites, as well as the tectonic architecture of the region, can be explained by a ridge subduction model. Based on these results, and previous studies, we suggest a southward ridge subduction model for the Sunidzuoqi–Xilinhot region. 相似文献
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The Lancang-Mekong River has attracted much attention from researchers, but the cooperation on water issues in this river basin has been limited, even after the establishment of the Mekong River Commission(MRC). Cooperation on water resources has been determined as one of the key priority areas in the Lancang-Mekong Cooperation Mechanism, but there are no details of targets. In order to establish the priorities of water cooperation under the mechanism, we adopted nine categories to classify the objectives of 87 water cooperation events based on the ‘Lancang-Mekong Water Cooperative Events Database' from 1995 to 2015. Based on the occurrence of cooperative events, cooperative objectives, cooperative scales, and approaches to cooperation, we conducted statistical, correlation, and text analyses. Our analyses indicated the following results: under the impact of economic conditions inside and outside the river basin, full cooperation appeared more difficult than bilateral and multilateral cooperation. Each of the partners adopted different preferences for cooperation targets. Cooperation with more definite objectives was easier to establish than cooperation with broader and more complex objectives. The potential objectives for water cooperation were navigation, hydropower, joint management, data sharing, flood control and water use. Because hydropower development is controversial, and because water cooperation is avoided by most existing regional cooperation mechanisms due to its complexity, we suggest the following priority areas for water cooperation in the Lancang-Mekong River Basin. 1) Navigation and flood control/drought relief are attractive objectives for all the riparian countries across the whole watershed. 2) Data sharing should be a priority for cooperation in the watershed due to its laying the foundation for the equitable and reasonable utilization of transboundary waters. 3) Hydropower is an objective best implemented mainly through bilateral cooperation, and on tributaries. 相似文献