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111.
A. V. Maslov V. N. Podkovyrov Yu. L. Ronkin M. T. Krupenin E. Z. Gareev V. M. Gorozhanin 《Stratigraphy and Geological Correlation》2006,14(2):126-149
In the mid-1980s, it was concluded based on geochemical study that Th, Sc, La concentrations and ratios Th/Sc, La/Sc and Eu/Eu* did not wary significantly in the post-Archean time. It was impossible to judge about compositional variations of upper crust during the Riphean and Vendian, because data of that time characterized a limited number of samples from the post-Archean basins of Australia, New Zealand, and Antarctic. Considered in this work are variations of Eu/Eu*, LREE/HREE, Th/Sc, and La/Sc ratios in Upper Precambrian fine-grained siliciclastic rock of the Southern Urals western flank (Bashkirian meganticlinorium) and Uchur-Maya region (Uchur-Maya plate and Yudoma-Maya belt). As is established, only the Eu anomaly in the studied siliciclastic rocks is practically identical to this parameter of the average post-Archean shale. Three other parameters plot on the Riphean-Vendian variation curves with positive and negative excursions of diverse magnitude, which do not coincide always in time. It is assumed that these excursions likely mark stages of local geodynamic activity, destruction of pre-Riphean cratons, and progressing recycling of sedimentary material during the Riphean. 相似文献
112.
This paper examines the debate surrounding a recent decision made by the Ghanaian government to permit gold exploration – and potentially, mining – in 'protected' forest reserves. In 2001, four mining companies were awarded mineral exploration concessions in forested regions of the country, and have since put forward applications to mine for gold. Notwithstanding the sharp divide in opinion on the issue, the continued uncertainty surrounding the implications of the proposed activities makes further research on the ground imperative in the short term. Work aiming to elicit indigenous perspectives on the projects, as well as research that facilitates dialogue between and/or among stakeholder parties, should be prioritized. 相似文献
113.
114.
This article discusses the involvement of older women and men in voluntary work in rural communities in the Netherlands. Gender,
ageing and civil society form the core concepts in the article. Politicians and policy makers in the Netherlands are worried
about the perceived decline of civil society and about the consequences of this decline for specific categories of older women
in terms of well-being and social exclusion. The paper presents the results of two surveys of involvement of older women and
men in civic organisations, voluntary work and local actions. The surveys indicate high levels of involvement of both women
and men. No gender differences are found in activity level. However, the data demonstrate the gendered nature of civil society.
Women are more engaged in informal voluntary work and informal local actions, while men are more active in formal organisations
and functions. This gender segmentation is not absolute, however. Many older women and men transgress the traditional feminine–masculine
boundaries. The surveys highlight the involvement of women and men in rural communities, but indicate lower activity levels
in urban areas. 相似文献
115.
Dissolved trace elements in river water: spatial distribution and the influencing factor, a study for the Pearl River Delta Economic Zone, China 总被引:1,自引:0,他引:1
T. P. Ouyang Z. Y. Zhu Y. Q. Kuang N. S. Huang J. J. Tan G. Z. Guo L. S. Gu B. Sun 《Environmental Geology》2006,49(5):733-742
Twenty-nine water samples were collected from different river channels of the Pearl River Delta Economic Zone, China. An inductively
coupled plasma-mass spectromonitor (ICP-MS) was used to measure concentrations of the trace elements in these samples. The
results suggest that the average concentrations of rare earth elements in river water show an increasing trend from the West
River, the North River, the rivers of the Pearl River Delta, and the Shenzhen River to the East River. Relatively high concentrations
of heavy metals appear in the East River, the rivers of the Pearl River Delta and the Shenzhen River, while the West River
and the North River have relatively low heavy metal concentrations. Trace element concentrations in samples collected near
urban or industrial areas are much higher than those of samples collected from distant areas, away from urban and industrial
areas. After natural conditions, human activities have significant influence on the trace element concentrations in river
water. This trace element concentration’s spatial distribution in the river water from the Pearl River Delta Economic Zone
is actually an integrated effect of natural conditions and human activity. 相似文献
116.
库车坳陷侏罗系煤成气动力学模拟研究 总被引:1,自引:0,他引:1
应用黄金管—高压釜封闭体系热模拟实验与GC、GC-IRMS分析技术,结合KINETICS专用软件,对库车坳陷侏罗系煤成气进行了动力学模拟研究。库车坳陷侏罗系煤具有高的产气性,在高演化阶段主要产甲烷气;侏罗系煤热解气甲烷碳同位素为-36‰~-25‰,乙烷碳同位素为-28‰~-16‰;甲烷、C2-C5气态烃的生成活化能分别为(47~64k)calm/ol、(55~72k)calm/ol,频率因子各为5.265×1013s-1、5.388×1018s-1。在此基础上,进一步探讨了克拉2气田天然气的成因。研究认为,克拉2气田天然气属阶段捕获的煤成气,主要聚集了5~1Ma时期的天然气,其成熟度Ro分布范围为1.3%~2.5%。 相似文献
117.
邢台矿区山字型构造的发现及其地质意义 总被引:1,自引:0,他引:1
邢台山字型构造位于河北省邯邢煤田内,其前弧向ES突出,脊柱呈ES-WN走向。分别分析了山字型构造脊柱及其东、西翼反射弧构造形迹特征,对研究区找矿具有重要意义。 相似文献
118.
A. M. Larin E. B. Sal’nikova A. B. Kotov L. B. Makar’ev S. Z. Yakovleva V. P. Kovach 《Stratigraphy and Geological Correlation》2006,14(5):463-474
Early Proterozoic granitoids are of a limited occurrence in the Baikal fold area being confined here exclusively to an arcuate belt delineating the outer contour of Baikalides, where rocks of the Early Precambrian basement are exposed. Geochronological and geochemical study of the Kevakta granite massif and Nichatka complex showed that their origin was related with different stages of geological evolution of the Baikal fold area that progressed in diverse geodynamic environments. The Nichatka complex of syncollision granites was emplaced 1908 ± 5 Ma ago, when the Aldan-Olekma microplate collided with the Nechera terrane. Granites of the Kevakta massif (1846 ± 8 Ma) belong to the South Siberian postcollision magmatic belt that developed since ~1.9 Ga during successive accretion of microplates, continental blocks and island arcs to the Siberian craton. In age and other characteristics, these granites sharply differ from granitoids of the Chuya complex they have been formerly attributed to. Accordingly, it is suggested to divide the former association of granitoids into the Chuya complex proper of diorite-granodiorite association ~2.02 Ga old (Neymark et al., 1998) with geochemical characteristics of island-arc granitoids and the Chuya-Kodar complex of postcollision S-type granitoids 1.85 Ga old. The Early Proterozoic evolution of the Baikal fold area and junction zone with Aldan shield lasted about 170 m.y. that is comparable with development periods of analogous structures in other regions of the world. 相似文献
119.
L.J. Hou M. Liu J.J. Lu S.Y. Xu D.N. Ou Y. Yang D.G. Zheng 《Environmental Geology》2006,49(7):937-945
The influences of exposure to the atmosphere on ammonium cycle in the intertidal surface sediments were in situ studied with
a geochemical approach at a typical station in the Yangtze Estuary during three tidal cycles in September 2003. During an
about 8-h emersion period of each diurnal tide, six high-resolution vertical profiles of adsorbed and dissolved ammonium were
measured. It was observed that both adsorbed and dissolved ammonium generally had an increasing trend in sediment cores during
the exposure. The rate of ammonium regeneration in sediments was estimated using the accumulation amount of ammonium including
adsorbed and soluble fractions during the daytime emersion. The calculation result showed that there was relatively high ammonification
rate (˜500 nmol N cm−3 day−1), which reflected that organic nitrogen in sediments was quickly decomposed with a residence time of ˜52.7 days. Due to the
dramatic temperature difference observed in sediment profiles, free convection was considered an important mechanism of regulating
the efflux of produced ammonium into overlying waters. The total estimated amount of regenerated ammonium was ˜1.35×105 t N year−1 in the intertidal flat of the Yangtze Estuary, which occupied 7.6% of the total inorganic nitrogen annually transported to
the estuarine ecosystem. 相似文献
120.