共查询到20条相似文献，搜索用时 31 毫秒
1.
《Applied Geochemistry》2002,17(6):781-792
Samples of tuff from boreholes drilled into fault zones in the Exploratory Studies Facility (ESF) and relatively unfractured rock of the Cross Drift tunnels, at Yucca Mountain, Nevada, have been analysed by U-series methods. This work is part of a project to verify the finding of fast flow-paths through the tuff to ESF level, indicated by the presence of ‘bomb’ 36Cl in pore fluids. Secular radioactive equilibrium in the U decay series, (i.e. when the radioactivity ratios 234U/238U, 230Th /234U and 226Ra/230Th all equal 1.00) might be expected if the tuff samples have not experienced radionuclide loss due to rock-water interaction occurring within the last million years. However, most fractured and unfractured samples were found to have a small deficiency of 234U (weighted mean 234U/238U=0.95±0.01) and a small excess of 230Th (weighted mean 230Th/234U 1.10±0.02). The 226Ra/230Th ratios are close to secular equilibrium (weighted mean=0.94±0.07). These data indicate that 234U has been removed from the rock samples in the last ∼350 ka, probably by pore fluids. Within the precision of the measurement, it would appear that 226Ra has not been mobilized and removed from the tuff, although there may be some localised 226Ra redistribution as suggested by a few ratio values that are significantly different from 1.0. Because both fractured and unfractured tuffs show approximately the same deficiency of 234U, this indicates that pore fluids are moving equally through fractured and unfractured rock. More importantly, fractured rock appears not to be a dominant pathway for groundwater flow (otherwise the ratio would be more strongly affected and the Th and Ra isotopic ratios would likely also show disequilibrium). Application of a simple mass-balance model suggests that surface infiltration rate is over an order of magnitude greater than the rate indicated by other infiltration models and that residence time of pore fluids at ESF level is about 400 a. Processes of U sorption, precipitation and re-solution are believed to be occurring and would account for these anomalous results but have not been included in the model. Despite the difficulties, the U-series data suggest that fractured rock, specifically the Sundance and Drill Hole Wash faults, are not preferred flow paths for groundwater flowing through the Topopah Spring tuff and, by implication, rapid-flow, within 50 a, from the surface to the level of the ESF is improbable. 相似文献
2.
在数字出版时代,网络首发能显著提升我国科技期刊质量和学术影响力。本研究以《地球学报》为例,统计其从2018年第3期至2022年第3期共318篇文章的投稿日期、改回日期、网络首发日期、刊发日期、被引频次、首次被引日期、印刷版下载量、网络首发版下载量等。对其出版周期、质量控制、出版方式、被引和下载量、主要期刊评价指标等进行分析。分析表明,网络首发能大幅缩短论文出版周期,吸引优秀稿源;避免了论文的政治性差错,学术和出版质量都得到了显著提升;增强出版助力学术期刊的知识生产与传播;网络首发出版流程和增强出版能有效避免学术不端行为;提高了论文的被引频次和下载量。网络首发对推动我国科技期刊的高质量发展,提升其质量和学术具有积极作用。 相似文献
3.
This paper presents a probabilistic formulation of unsaturated flow through rough multi-segmented fractures, with emphasis
on Dripping Initiation Time (DIT), and attempts to explain the fast flow paths detected at the Yucca Mountain (YM) Exploratory
Studies Facility (ESF). Three scenarios of parameters were used to test the validity of the model with these fast flow paths.
The scenarios differed in the DITs and the corresponding parameter configurations were also tested for three different stratigraphic
horizon depths. Each depth represented a different location where fast flow has been detected at YM. The first depth corresponds
to the Bow Ridge Fault; the second represents a network of steep fractures and cooling joints with large variability in dip;
and the third location, probably connected to the Diabolous Ridge Fault, has a flow path that is low dipping. Monte Carlo
simulations for each configuration and depth produced probabilistic results from nine scenarios for DITs, which are quite
consistent with field observations. 相似文献
4.
5.
论述了现有的地下实验室的分类,对普通地下实验室与特定场址地下实验室的主要特征进行了对比分析,论述了各国地下实验室的研究概况,对特定场址地下实验室的概念进行了讨论。鉴于在现行的地下实验室分类中,对特定场址地下实验室的定义似乎界定过宽,因为有些该类型的地下实验室,缺乏明确的历史定位,最终没有起到特定场址地下实验室应起的作用。笔者建议,只有建在经本国政府批准的最终处置库场址上的地下实验室,才可称作为特定场址地下实验室,如美国的WIPP和ESF以及芬兰的ONKALO。因为只有这类地下实验室,才能真正起到论证处置库场址适宜性和高放废物处置方案可行性的作用。 相似文献
6.
The standard dual-component and two-member linear mixing model is often used to quantify water mixing of different sources. However, it is no longer applicable whenever actual mixture concentrations are not exactly known because of dilution. For example, low-water-content (low-porosity) rock samples are leached for pore-water chemical compositions, which therefore are diluted in the leachates. A multicomponent, two-member mixing model of dilution has been developed to quantify mixing of water sources and multiple chemical components experiencing dilution in leaching. This extended mixing model was used to quantify fracture-matrix interaction in construction-water migration tests along the Exploratory Studies Facility (ESF) tunnel at Yucca Mountain, Nevada, USA. The model effectively recovers the spatial distribution of water and chemical compositions released from the construction water, and provides invaluable data on the matrix fracture interaction. The methodology and formulations described here are applicable to many sorts of mixing-dilution problems, including dilution in petroleum reservoirs, hydrospheres, chemical constituents in rocks and minerals, monitoring of drilling fluids, and leaching, as well as to environmental science studies. 相似文献
7.
The origin of secondary calcite-silica minerals in primary and secondary porosity of the host Miocene tuffs at Yucca Mountain has been hotly debated during the last decade. Proponents of a high-level nuclear waste repository beneath Yucca Mountain have interpreted the secondary minerals to have formed from cool, descending meteoric fluids in the vadose zone; critics, citing the presence of two-phase fluid inclusions, argued that the minerals could only have formed in the phreatic zone from ascending hydrothermal fluids. Understanding the origin, temperature, and timing of these minerals is critical in characterizing geologically recent fluid flux at the site, and has significant implications to whether waste should be stored at Yucca Mountain.Petrographic and paragenetic studies of 155 samples collected from the Exploratory Studies Facility (ESF) and repository block cross drift (ECRB) tunnels indicate that heterogeneously distributed calcite with lesser chalcedony, quartz, opal, and fluorite comprise the oldest secondary minerals. These are typically overgrown by intermediate-aged calcite, often exhibiting distinctive bladed habits. The youngest event recorded across the site is the deposition of Mg-enriched (up to ∼1 wt%) and depleted, growth-zoned calcite intergrown with U-enriched opal. The cyclical variation in Mg enrichment and depletion is probably related to climate changes that have occurred during the last few million years. The distribution of secondary minerals is consistent with precipitation in the vadose zone.Fluid inclusion petrography of sections from the 155 samples determined that 96% of the fluid inclusion assemblages (FIAs) contained liquid-only inclusions that formed at ambient temperatures (<35°C). However, 50% of the samples (n = 78) contained relatively rare FIA that contain both liquid-only and liquid plus vapor inclusions (herein termed two-phase FIAs) that formed at temperatures above 35°C. Virtually all of these two-phase FIAs occur in paragenetically old calcite; rare two-phase inclusion assemblages were also observed in early fluorite and quartz, and early-intermediate calcite. Homogenization temperatures (≡ trapping temperatures) across Yucca Mountain are generally 45 to 60°C, but higher temperatures reaching 83°C were recorded in calcite from the north portal and ramp of the ESF. Cooler temperatures of ∼35 to 45°C were recorded in the intensely fractured zone. Multiple populations of two-phase FIAs from lithophysal cavities in the ESF and ECRB cross drift indicate early fluid cooling with time from temperatures >45°C in early calcite, to <35 to 45°C in paragenetically younger calcite. Freezing point depressions range from −0.2 to −1.6°C, indicating trapping of a low salinity fluid. The majority of intermediate calcite and all outermost Mg-enriched calcite contains rare all-liquid inclusions and formed from ambient temperature (<35°C) fluids.Carbon and oxygen isotope data reveal a consistent trend of decreasing δ13C (from 9.5 to −8.5‰) and increasing δ18O (from 5.2 to 22.1‰) values from paragenetically early calcite to Mg-enriched growth-zoned calcite. Depleted δD values (−131 to −90‰) of inclusion fluids from intermediate and the youngest Mg-enriched calcite indicate derivation from surface meteoric fluids. Recalculation of δ18OH2O values of −12 to −10‰ is consistent with derivation from paleometeoric fluids.Results of integrated U-Pb dating (opal and chalcedony) and fluid inclusion microthermometry indicate that two-phase FIAs that trapped fluids of >50°C are older than 6.29 ± 0.30 Ma. Two-phase FIAs in paragenetically later calcite, which formed from fluids of 35 to 45°C, are older than 5.32 ± 0.02 Ma. There is no evidence for trapping of fluids with elevated temperatures during the past 5.32 my. The youngest Mg-enriched calcite intergrown with opal began to precipitate between about 1.9 to 2.9 Ma and has continued to precipitate within the past half million years. The presence of liquid-only inclusions and the consistent occurrence of Mg-enriched calcite and opal as the youngest event indicate a minor, but chemically distinct, ambient temperature (<35°C) fluid flux during the past 2 to 3 my. 相似文献
8.
9.
10.
《探矿工程》杂志创刊于1957年10月。60年来,曾两度停刊、复刊,几次变更刊名,几易主办单位,在历届编委会和编辑部的努力和坚守下,在广大读者、作者的支持和陪伴下,顽强地走过了风雨兼程的60年。她在书写自己60年辉煌历史的同时,也完成了一部记录中国探矿工程技术发展历史的巨著。当前她正面临着来自学科调整、评价体系、新兴媒体等的冲击以及经济方面的压力。展望未来,将继续坚持注重实用性、理论与实践相结合、学习国外先进经验的办刊宗旨,继续做探矿工程（岩土钻掘工程）技术发展的忠实记录者。 相似文献
11.
经自主申报、专家评审,中国地质学会获得中国科学技术协会“2021 年全国学会期刊出版工作优秀单位”称号。 相似文献
12.
Qiu Junling Wang Xiuling He Siyue Liu Houquan Lai Jinxing Wang Lixin 《Natural Hazards》2018,91(3):1425-1425
Natural Hazards - Due to an oversight, four references were cited incorrectly in the reference list of the original publication as well as in the text of the publication. The first names were used... 相似文献
13.
The Sustainable Livelihoods (SLs) is a significant subject and concept within the sustainable development research and it also has the potential to deal with the fundamental challenge in terms of inequalities between inter-generation and intra-generation, now and in the future. This paper adopted bibliometrics to conduct the quantitative analysis of the development, hot topics, and collaboration network in terms of SLs researches. Moreover, the analyzed parameters included publication output, distribution of publications by authors and organizations, subject classification of publication, etc. Some 809 papers were analyzed on various aspects of publication, and the results show that publication output has increased promptly over the past two decades; however, the cooperation network among different organizations and authors on the topic of SLs has not been closely linked. The hot topics of SLs involve three categories, which are ①theoretical research in terms of sustainable livelihoods; ②the research on livelihood strategy (problem-orientated); ③the research of ecological vulnerability. It is important for Chinese scholars to continue the future SLs researches in accordance with the strategy of target poverty alleviation and rural revitalization. Additionally, it is also vital to broaden the theoretical horizons by transitioning from the research on agricultural economy to the exploration of relationship of SLs-ecological environment, SLs-biodiversity, SLs-climate change and adaptation, SLs-human capital development, etc.; to strengthen the academic cooperation and exchanges; to innovate research approach; to improve both quantity and quality of research output for the purpose of providing long-term and scientific decision for the decision makers. 相似文献
14.
运用文献计量学方法,对《地球科学与环境学报》（以下简称《学报》）2004—2010年载文的第一作者学历、职称和服务单位、论文资助项目来源、研究领域、出版时滞、被引频次、下载次数、影响因子等论文信息指标进行了统计分析。结果表明《学报》呈现以下特征：高学历作者比例稳步提升;副高职称和中级职称作者是《学报》作者的骨干力量;作者来源呈多元化发展,主办单位论文呈下降趋势;大多数论文有各类基金项目资助;基础地质及矿产地质是《学报》载文的主要内容;出版时滞需要进一步优化;被引频次计量指标反映《学报》呈现良好的发展态势。 相似文献
15.
滑坡的临滑预警预报研究一直以来都是热点也是难点。速度倒数模型是目前广泛使用的临滑预报模型,选择恰当的拟合曲线起始点将提高预报模型的精度。利用经济学上非常成熟的平滑异同平均线指标（MACD）快速寻找速度倒数模型拟合曲线的起始点,也就是滑坡临滑加速变形阶段开始加速（Onset of Acceleration,OOA）点,并以云南省会泽县的区布嘎滑坡为例,使用该指标对滑坡体进行临滑预报,并对该模型准确性进行了评估。结果表明:当变形速度的MACD值在?1~1的区间时,代表滑坡变形速度虽然有所增加,但变形趋势并未整体改变;当MACD值超过?1~1的区间,代表滑坡变形趋势整体发生改变,可将此阶段短期平均线上穿长期平均线的点（同时也是MACD值由负转正的点）,作为滑坡OOA点。利用MACD指标能够快速有效的寻找拟合曲线起始点,利用指数平滑函数（ESF）处理的监测数据,拟合曲线的确定系数最高,误差率最低,误差率低于2%,模型预测结果随着数据的更新,将不断逼近真实结果,具有较高的准确率。 相似文献
16.
为实现分布式海量影像分发服务,提出了基于J2EE的分布式海量影像数据分发服务架构,并重点探讨海量影像数据的索引、影像分发服务的多级缓存、基于服务集群的分发服务等关键技术,最后利用VC++6.0、EVC++4.0、Jbuilder2005等开发工具实现了海量影像动态分发服务系统,分别在局域网和海事卫星网络两种网络条件下进行了实验与分析。 相似文献
17.
《地学前缘》2006,13(4):118-118
Earth Science Frontiers is a bi-monthly publication in Chinese with English abstracts for most papers; a few articles are published entirely in English. It is a medium for the publication of original and forefront research and high quality reviews covering recent advances in all fields of Earth Sciences. Each issue is devoted to a single topic and edited by an authority in that field. 相似文献
18.
The network technology has provided impetus and channels for the development of sci-tech periodicals and promoted the transformation of the publication mode of Journal of Palaeogeography(Chinese Edition). Through the independent website construction,providing readers with diversified access to articles,diversified communication methods,personalized accurate article push,joining the OSID open science program,etc.,a three-dimensional publication mode adapted to the development of periodicals has been gradually formed. 相似文献
19.
20.
《地学前缘》2006,13(5):407-407
Earth Science Frontiers is a bi-monthly publication in Chinese with English abstracts for most papers; a few articles are published entirely in English. It is a medium for the publication of original and forefront research and high quality reviews covering recent advances in all fields of Earth Sciences. Each issue is devoted to a single topic and edited by an authority in that field. 相似文献