Paleoenvironment evolution of the East Philippine Sea recorded in the new-type ferromanganese crust since the terminal Late Miocene     

Xu ZhaoKai  Li AnChun  Jiang FuQing  Li TieGang  Meng QingYong  Jin Ning 《中国科学D辑(英文版)》2007,50(8):1179-1188

From systemic research of microstructure, geochemistry, uranium-series and 10Be isotope dating on a new-type deepwater ferromanganese crust from the East Philippine Sea, the paleoenvironment evolu-tion of the target area since the terminal Late Miocene was recovered. The vertical section changes of microstructure and chemical composition are consistent in the studied crust, which indicate three major accretion periods and corresponding paleoenvironment evolution of the crust. The bottom crust zone was formed in the terminal Late Miocene (5.6 Ma) with loose microstructure, high detritus content and high growth rate. Reductions of mineral element content, accretion rate and positive Ce-anomaly degree at 4.6 Ma indicate temporal warming, which went against the crust accretion and finally formed an accretion gap in the terminal Middle Pliocene (2.8―2.7 Ma). The more active Antarctic bottom sea-waters in the Late Pliocene (2.7 Ma) facilitated the fast transfer to the top pure crust zone. Hereafter, with the further apart of volcanic source and the keeping increase of eolian material (1.0 Ma), although surrounding conditions were still favorable, mineral element content still shows an obvious reducing trend. It thereby offers new carrier and data for the unclear paleoceanographic research of the target area since the terminal Late Miocene.  相似文献   

Study of the erosion rates in the upper Maracujá Basin (Quadrilátero Ferrífero/MG,Brazil) by the in situ produced cosmogenic 10Be method     

André Salgado  César Varajão  Fabrice Colin  Régis Braucher  Angélica Varajão  Herminio Nalini Jr 《地球表面变化过程与地形》2007,32(6):905-911

The present work quantifies the erosive processes in the two main substrates (schists–phyllites and granites–gneisses) of the upper Maracujá Basin in the Quadrilátero Ferrífero/MG, Brazil, a region of semi‐humid tropical climate. Two measuring methods of concentration were used: (i) in situ produced ¹⁰Be in quartz veins (surface erosion rates) and (ii) ¹⁰Be in fluvial sediments (basin erosion rates). The results confirm that (i) erosion tends to be more aggressive close to the headwaters than in the lower parts of the basin and (ii) the region is now affected by dissection. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

30—50天低频振荡和准双周振荡对持续异常的影响     

孙永罡  陈久康 《南京气象学院学报》1992,15(3):368-376

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中国黄土¹⁰Be研究进展   总被引：1，自引：0，他引：1  

沈承德  刘东生 《地球科学进展》1995,10(6):590-596

８０年代中期，中国和瑞士科技工作者开始联合进行黄土＾１０Ｂｅ研究。建立了黄土＾１０ＢｅＡＭＳ测量的理想流程，发现了＾１０Ｂｅ在黄土地层良好保存性等重要地球化学行为特征，确认了黄土＾１０Ｂｅ研究具有重要意义。对洛川黄土部面０．４－１３８ｍ段６００多个样品进行了＾１０Ｂｅ测定，建立了２．５Ｍａ以来大陆堆积物同位素记录曲线。  相似文献   

滇黔桂卡林型金矿区水系沉积物和岩石金含量与时空分布     

赵东杰  王学求 《地球学报》2020,41(3):407-419

为研究滇黔桂卡林型金矿区水系沉积物和岩石中金的地球化学时空分布及其与金矿规模的对应关系,系统收集了该区1:20万区域化探全国扫面计划水系沉积物和全国地球化学基准计划岩石金的地球化学数据,绘制了水系沉积物和岩石金的地球化学分布图。滇黔桂卡林型金矿区以水系沉积物金地球化学异常面积大于1000 km^2为准,共圈定5处金的地球化学省,这些金的地球化学省同时也是矿床大规模产出的部位。区内右江盆地水系沉积物金背景值(1.94×10^–9)高于扬子克拉通(1.68×10^9),其内以泥岩、页岩、砂岩、灰岩为代表的容矿岩石金背景值(0.51×10^–9)也高于扬子克拉通(0.39×10^–9)。研究区不同构造单元及沉积相中水系沉积物金背景值受岩石金背景值的制约。金的地球化学省是地壳演化过程中不均匀分布的高金背景岩石、金矿化作用及金矿床次生风化作用相互叠加的结果。该研究有助于有效判断异常成因、识别成矿作用存在,对研究金的区域成矿规律和聚焦找矿靶区具有重要意义。  相似文献   

Direct Observations of Atmospheric Transport and Stratosphere-Troposphere Exchange from High-Precision Carbon Dioxide and Carbon Monoxide Profile Measurements     

You YI  Zhaonan CAI  Yi LIU  Shuangxi FANG  Yuli ZHANG  Dongxu YANG  Yong WANG  Miao LIANG  Maohua WANG 《大气科学进展》2020,37(6):608-616

The balloon-borne Aircore campaign was conducted in Inner Mongolia,China,on June 13 and 14 2018,which detected carbon dioxide(CO_2) and carbon monoxide(CO) profiles from surface to 24 km,showing strong positive and negative correlations between 8 km and 10 km on 13 and 14 June,respectively.Backward trajectories,meteorological analyses,and CO_2 horizontal distributions were combined to interpret this phenomenon.The results indicated that the source region experienced a stratospheric intrusion and exhibited a large horizontal CO_2 gradient;namely,lower CO concentrations corresponded to higher CO_2 concentrations and vice versa.The laminar structure with multiple origins resulted in the highly negative correlation between CO_2 and CO in the upper troposphere on 14 June.The contribution of stratospheric air mass to the upper troposphere and that of tropospheric air mass to the lower stratosphere were 26.7% and24.3%,respectively,based on a mass balance approach.Another interesting phenomenon is that CO_2 and CO concentrations increased substantially at approximately 8 km on 13 June.An analysis based on the backward trajectory implied that the air mass possibly came from anthropogenic sources.The slope of CO_2/CO representing the anthropogenic sources was 87.3 ppm ppm~(-1).In addition,the CO_2 profile showed that there was a large CO_2 gradient of 4 ppm km-1 within the boundary layer on 13 June,and this gradient disappeared on 14 June.  相似文献   

Une dépression piézométrique naturelle en hausse au Sahel (Sud-Ouest du Niger)A rising piezometric depression in the Sahel (southwestern Niger)     

Guillaume Favreau  Christian Leduc  Christelle Marlin  Abdou Guéro 《Comptes Rendus Geoscience》2002,334(6):395-401

In southwest Niger, the Continental Terminal water table displays a natural hollow shape about 10 m in depth over an area of 4000 km². A 10-year survey of this hollow aquifer has shown that current recharge is above $\text{20 }\text{mm}\text{yr}{}^{\mathrm{?1}}$. The water table has risen continuously since the 1950–1960s as a result of land clearance. This shows a disequilibrium in the aquifer balance. The long-term recharge rate is estimated by radioisotopes to be around $\text{1 }\text{mm}\text{yr}{}^{\mathrm{?1}}$. This figure fits with the only possible origin of the piezometric depression, i.e. evapotranspiration losses in its centre. To cite this article: G. Favreau et al., C. R. Geoscience 334 (2002) 395–401.  相似文献   

广南堂上金矿多种金矿化的发现     

杨昌华  刘星  罗荣生 《云南地质》2006,25(3):286-290

在不到10km^2的范围内，集中发现了滇黔桂金三角地区常见的多种矿化类型：微细粒浸染型金矿、不整合面上金矿（大厂层）、基性火山岩金矿、火山碎屑沉积型金矿、石英脉型金矿、现代河流沉积中的砂金，且存在不同的找矿标志。  相似文献   

K-Ar法地质年龄国家一级标准物质ZBH-25黑云母的研制   总被引：3，自引：4，他引：3  

桑海清　王非贺怀宇  王英兰杨列坤　朱日祥 《岩石学报》2006,22(12):3059-3078

ZBH-25黑云母采自北京房山花岗闪长岩体。它的~(40)Ar/~(39)Ar 阶段加热实验结果表明,~(40)Ar~*在矿物晶格中保存均匀稳定,年龄谱平坦,~(39)Ar 析出量高达96%,~(40)K-~(40)Ar~*同位素体系封闭良好,证明该黑云母结晶以后未受过热扰动。坪年龄为133.0±0.3Ma,总气体年龄为132.1±0.6Ma;~(36)Ar/~(40)Ar-~(39)Ar/~(40)Ar 反等时线年龄为133.1±1.3 Ma,~(40)Ar/~(36)Ar 初始值为293.5±1.6,与大气氩丰度比(295.5±0.5)处于同一范围,表明样品不含过剩氩。激光显微探针单颗粒坪年龄为132.8±0.2Ma,年龄谱和 K/Ca 谱线平坦,激光熔样总气体年龄为131.3±0.2Ma(图6)。这几个 Ar-Ar 年龄的一致性,说明样品具有良好的均匀性和稳定性,是理想的 K-Ar 和 Ar-Ar 法年龄标准物质。对均匀性检验数据进行统计学方法检验,在0.05显著性水平下,证明 K 和~(40)Ar~*的 F 分布值小于 F 临界值,说明该样品是均匀的。国内外14个实验室参加了 K 含量的定值分析,15个实验室参加了~(40)Ar~*含量的定值分析,经统计学方法检验,结果显示全部定值数据都服从正态分布并具等精度。在置信概率为0.95时,~(40)Ar~*和 K 含量的相对标准偏差都小于0.5%。两个特性量值定值分析结果的一致值和不确定度分别为:~(40)Ar~*=1.817±0.013×10~(-9)mol/g,K=7.60±0.02%,K-Ar 年龄(标准值)=132.9±1.3Ma(2σ).此标准物质纯度为98.8%,粒度为0.25-0.63mm,总重量为5800g,缩分成最小样品单元共400瓶,每瓶重量为14.5g。可供我国 K-Ar 和 Ar-Ar 法同位素年代学实验室使用120年。  相似文献   

SEDIMENT MOBILIZATION BY SURFACE EROSION IN MIDDLE MOUNTAIN CATCHMENTS OF NEPAL     

Juerg MERZ Gopal NAKARMI Pradeep M. DANGOL Madhav P. DHAKAL Bhawani S. DONGOL Rolf WEINGARTNER 《国际泥沙研究》2006,21(3):180-199

1 INTRODUCTION Soil erosion in the foothills of the Hindu Kush-Himalayas (HKH) is considered to be a hot topic in land degradation research in the region (Scherr and Yadav, 1996). The land degradation research has mainly addressed the issue of topsoil los…  相似文献