Factors Controlling Precipitation of Barite and Witherite and Genesis of the Ankang–Xunyang Barium Deposits, Shaanxi, China     

WU Shenghu  LIU Jiajun  ZHAI Degao 《《地质学报》英文版》2015,89(3):836-851

The barium deposits in Ankang and Xunyang counties,Shaanxi Province,China,occur in the northernmost part of the world-class barium metallogenic belt in south Qinling.The deposits are hosted by the Lower Silurian carbonaceous siliceous rocks,with a unique combination of barite and witherite.The homogenization temperatures of fluid inclusions in the barite are mainly concentrated between 135 and 155 ℃,whereas those from the witherite have two peaks of 165-175 ℃,and 215-225℃,respectively.Laser Raman analysis of fluid inclusions indicates that the vapor phase of fluid inclusions in barite is dominated by H_2O,although some contains N_2,H_2S,and CH_4.The compositions of the vapor and liquid phases of fluid inclusions in witherite can be divided into two end-members,one dominated by H_2O without other volatiles,and the other containing CH_4,C_2H_6,C_3H_8,C_2H_4,and C_6H_6 in addition to H_2O.CO_2,H_2S,and some CH_4 are interpreted as products of chemical reactions during mineralization.Organic gases(CH_4,C_2H_6,C_3H_8,C_2H_4,and C_6H_6) in the fluids were critical in the formation of barium sulfate versus carbonate.The δ~(34)S values of barite range from 38.26‰ to54.23‰(CDT),the δ~(34)S values of sulfides coexisting with barium minerals vary from 22.44‰ to25.11‰(CDT),and those in the wall rock from 11.60‰ to 19.06‰(CDT).We propose that the SO_4~(2-)generally experienced bacterial sulfate reduction in seawater before mineralization,and some SO_4~(2-)also experienced thermochemical sulfate reduction in hydrothermal system during mineralization.The δ~(13)C values of witherite range from-27.30‰ to-11.80‰(PDB),suggesting that carbon was sourced from organic substances(like CH_4,C_2H_4,and C_2H_6).The formation of witherite was possibly associated with thermochemical sulfate reduction,which caused the consumption of the organic gases and SO_4~(2-) in the hydrothermal solutions,consequently inhibiting barite formation.The important conditions for forming witherite include high fluid temperatures,high Ba~(2+) concentrations,CO_2 in the fluids,low HS~- concentrations,and the subsequent rapid diffusion of H_2S during thermochemical sulfate reduction of the fluids.  相似文献   

区县级多源异构空间数据共享平台研究及应用     

余应刚  葛爱霞 《测绘与空间地理信息》2012,35(11):53-55,59

针对区县级空间数据凌乱、共享程度低、应用效率不高等现状,充分考虑区县级政府部门对多源异构地理空间数据资源共建共享的需求,基于Web Service和ArcGIS Server技术,构建了包含数据管理、运维管理、共享交换、公共服务等四大子系统为核心的多源异构空间数据共享服务平台框架,并在佛山市顺德区成功应用,实现了区县级多源异构空间数据的集成与共享。  相似文献   

Spectra of poorly resolved ocean data     

Hans?van HarenEmail author 《Ocean Dynamics》2004,54(1):49-53

Standard temperature and pressure sensors on Aanderaa RCM8 current meters have a resolution of 0.024 °C and 0.6 bar, each equal to 1 digital number (value) over a range of 1024. It is shown that an 11-month deep-ocean temperature record using only four values can contain useful spectral information on internal wave motions. This is partially due to the modulation of high-frequency data by non-zero low-frequency (subinertial) variations. This result follows from the comparison of this record with artificial three- and four-value data constructed from temperature records observed in stronger stratified waters nearby. These artificial records show main features of the internal wave band similar to those observed in the original data spectra. Peaks at tidal harmonic frequencies and enhancements at sum-tidal-inertial interaction frequencies are preserved in the artificial data, but overall noise level (and thus the continuum spectral slope) is enhanced with respect to the properly resolved records (using 15 and 100 values). As a demonstration of the stable accuracy of the temperature sensors, the poorly resolved records provided an estimate of mean stratification to within 5% of the estimate using Seabird CTD data.Responsible Editor: Hans Burchard  相似文献   

从台湾“9·21”大地震看平潭房屋建设的弊端     

黄爱贤 《福建地震》1999,(4)

本文分析了平潭房屋建设在抗震性能方面存在的主要问题。  相似文献   

山区县域可持续发展定量研究   总被引：10，自引：3，他引：7  

冯玉广 《山地学报》2000,18(4):329-335

在充分认识山区县域特征的基础上,依据可持续发展思想,建立了评价山区县域可持续发展的指标体系和定量评价模型。将其应用于交口县,获得了较满意的效果。  相似文献   

Black–White and Hispanic–White Segregation in U.S. Counties     

James P. Allen  Eugene Turner 《The Professional geographer》2013,65(4):503-520

Residential segregation in metropolitan areas has been the subject of much research, but this article analyzes patterns of white–black and white–Hispanic segregation in counties across the United States. Our purpose was to understand county variations in this one dimension of inequality. Conceiving of segregation as relative inequality of access to neighborhood resources, we measured segregation in 2000 by the index of dissimilarity (D) calculated by blocks, mapped the index values, and correlated them with census variables. Three filters enabled us to eliminate counties with characteristics that could have corrupted the analyses, leaving us with more than 1,000 counties in each analysis. Both minority groups were less segregated from whites in the West and South and in metropolitan counties. Lower segregation was strongly associated with higher minority socioeconomic status and higher percentages of minorities living in housing built in the 1990s, and Hispanic–white segregation was lower where more Hispanics were U.S.-born or English proficient. The racial threat hypothesis was supported only weakly and inconsistently. Mapping made it possible to identify regional and local patterns of high and low segregation as well as the lower segregation of suburban counties in some large metropolitan areas.  相似文献   

不同地形特征下云南沿边村寨农户生计资产研究     

王丹丹  甘淑  张超  孙冠华 《云南地理环境研究》2013,(6):41-47

依据英国国际发展署(DFID)提出的可持续生计分析框架为指导,选取与农户生计资产密切相关的评价因子,建立农户生计资本评价指标体系,对云南省25个沿边县域中具有不同地形特征的64个村寨生计资本进行了测算、对比和分析。研究发现,研究区生计资本总体水平偏低,不同地形特征下村寨间生计资本差异性较大,生计资本不平衡,针对不同的生计脆弱性,提出如下讨论:(1)人力资本上,着重加强和巩固教育和培训力度;(2)金融资本、社会资本上,加大农业现代化水平的投资力度,加大加强农业合作组织的建设;(3)物质资本上,建议增加对农业基础设施和信息媒体的建设;(4)在自然资本的脆弱性上,要在可持续性利用的基础上,大力发展循环经济。  相似文献   

"数字衡阳"市县一体化大数据与地理信息公共服务云平台建设的技术创新     

张淑玲 《测绘通报》2019,(9):112-114

“数字衡阳”市县一体化大数据与地理信息公共服务云平台建设项目，实现了市县地理信息一体化管理、共享和协同服务，制定了完整的市县一体化标准体系，创新了基础地理信息数据生产和管理机制，创建了基于标准体系的“一键成图”技术。大幅提升了地理信息共享应用的效益，降低了县级地理信息应用技术门槛，为全国其他地区数字城市建设提供了可借鉴、推广的经验。今后将进一步实现数据成果在各行各业的快速应用，产生更好的经济效益和社会效益。  相似文献   

河北省县域产业结构的空间差异及演化分析     

朱苏加  吴建民  张慧峰 《地理与地理信息科学》2014,30(6)

利用HHI指数、空间基尼系数和产业结构差异系数探讨河北省县域三次产业空间差异的变化,发现县域各次产业的绝对数量在空间上集中度很高,少数几个县域集中了相当部分的产业产值,空间差异性大;在考虑到县域经济总量的分析中,发现各次产业相对量又呈现较大的分散趋向,得出河北省县域三次产业绝对集中相对分散的结论。同时,研究发现县域产业结构的差异性较小,多年变化不大,调整产业结构将会促进县域经济的发展。  相似文献   

云南安宁禄脿小村锰铁矿矿床成因及找矿标志     

杨定炳  李迅  庄荣寿  周丽英 《云南地质》2010,29(3):364-366,350

昆阳群美党组军哨段中亚段第二层砂质板岩为铁锰矿源层,严格受地层层位控制,具有后期改造特征,属沉积—改造—层控矿床。  相似文献