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31.
Yuan-Bao Wu Shan Gao Hong-Fei Zhang Sai-Hong Yang Wen-Fang Jiao Yong-Sheng Liu Hong-Lin Yuan 《Contributions to Mineralogy and Petrology》2008,155(1):123-133
The Hong’an area (western Dabie Mountains) is the westernmost terrane in the Qinling-Dabie-Sulu orogen that preserves UHP
eclogites. The ages of the UHP metamorphism have not been well constrained, and thus hinder our understanding of the tectonic
evolution of this area. LA-ICPMS U–Pb age, trace element and Hf isotope compositions of zircons of a granitic gneiss and an
eclogite from the Xinxian UHP unit in the Hong’an area were analyzed to constrain the age of the UHP metamorphism. Most zircons
are unzoned or show sector zoning. They have low trace element concentrations, without significant negative Eu anomalies.
These metamorphic zircons can be further subdivided into two groups according to their U–Pb ages, and trace element and Lu–Hf
isotope compositions. One group with an average age of 239 ± 2 Ma show relatively high and variable HREE contents (527 ≥ LuN ≥ 14) and 176Lu/177Hf ratios (0.00008–0.000931), indicating their growth prior to a great deal of garnet growth in the late stage of continental
subduction. The other group yields an average age of 227 ± 2 Ma, and shows consistent low HREE contents and 176Lu/177Hf ratios, suggesting their growth with concurrent garnet crystallization and/or recrystallization. These two groups of age
are taken as recording the time of prograde HP to UHP and retrograde UHP–HP stages, respectively. A few cores have high Th/U
ratios, high trace element contents, and a clear negative Eu anomaly. These features support a magmatic origin of these zircon
cores. The upper intercept ages of 771 ± 86 and 752 ± 70 Ma for the granitic gneiss and eclogite, respectively, indicate that
their protoliths probably formed as a bimodal suite in rifting zones in the northern margin of the Yangtze Block. Young Hf
model ages (T
DM1) of magmatic cores indicate juvenile (mantle-derived) materials were involved in their protolith formation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
32.
33.
This paper explores the links between a strategic policy, urban consolidation, and house prices by examining the changes in
the mix of housing and in house price for the period 1991–2004. We contend that urban consolidation could be seen as a source
of additional supply, (which might be expected to be felt in lower prices and so contribute to a local policy objective) but
also as a stimulus to demand (by developers who could bid up the price of lots where it was understood more housing could
be built). Analyses were carried out at the metropolitan and sub-regional scales using correlation tests. The research finds
very weak statistical connections, and concludes that this policy has not been associated with price changes. 相似文献
34.
加强技术创新服务地质调查——庆祝探矿工艺研究所成立30周年 总被引:1,自引:1,他引:0
为加强地质探矿技术力量,改变地质装备落后现状,经国务院批准,1978年8月8日成立了探矿工艺研究所。30年来,经过新老两代工艺所人的艰苦奋斗、刻苦钻研、勇于创新,在科研攻关、成果转化、基地建设和管理等方面都取得了可喜的成绩,为国家的地质科学事业做出了贡献,目前已成为一个“以勘查技术为基础,以承担地质调查任务和科研项目、提供勘查与监测技术方法和技术服务为手段,以服务国家经济建设、社会发展和地质工作为目标,以探矿工艺技术和地质灾害监测防治技术研发为主业”的地质调查科研机构。回顾了工艺所艰苦创业、改革进取的发展历程,对科技体制改革、专业结构调整、人事分配制度改革、地质调查和科研工作进行了总结,展示了丰硕的科研成果和强劲的科技实力;指出了工艺所在“十一五”期间地质调查和科研工作的重点领域和优先发展方向。 相似文献
35.
在煤田地质钻探生产中,由于地质因素、钻进方法、操作不当等综合因素,出现钻孔偏斜严重超限或发生复杂的孔内事故无法处理时,采用传统的纠斜方法和造斜手段来处理,不但费工费时,事故处理和纠偏的效果不佳,而且会给后继施工带来更大的安全隐患。利用螺杆定向钻进技术快速纠斜和绕过复杂的事故孔段,顺利完成施工任务,达到设计目的,收到了很好的效果。 相似文献
36.
中国东北依兰地区块状蓝片岩的地球化学特征 总被引:8,自引:0,他引:8
黑龙江省依兰地区分布的黑龙江杂岩被认为足具有缝合带性质的构造混杂岩,其中所含变基性火山熔岩中含有的变质矿物不具有定向组构特征,因此称之为块状蓝片岩.特征变质矿物--蓝闪石的大量出现表明其经历过高压低温变质作用.常量地球化学分析表明,其SiO2含量均在53%以下,TiO2含量超过2%,Na2O K2O的含量为2.77%~6.41%,Na2O的含量普遍大于K2O的含量,Na2O K2O-SiO2变异图显示其具有碱性玄武岩特征;痕量元素地球化学分析显示其轻重稀土元素分异明显,稀土元素配分曲线表现为轻稀土元素富集、重稀土元素亏损的右倾型.球粒陨石标准化图解中,不具有Eu的负异常;Nbx2-Zr/4-Y、Ti/100-Zr-Sr/2与Ba-Th-Nb-La图解的综合分析表明,块状蓝片岩具有碱性洋岛玄武岩(OIB)的特征,它们应是佳木斯地块与松嫩地块之间古洋壳俯冲过程的残留,这为探讨佳木斯陆块与松嫩陆块之间古老洋盆俯冲消减过程提供了重要依据. 相似文献
37.
38.
39.
G. R. Huguenin A. E. Lilley W. H. McDonough M. D. Papagiannis 《Planetary and Space Science》1964,12(12):1157-1167
Radio noise observations at frequencies of 0·700 Mc and 2·200 Mc were made at altitudes between 3000 and 11,000 km from a Blue Scout Jr. high-altitude rocket probe on 30 July 1963. A steady background flux of (7·5−3+6) × 10−19 W m−2)(c/s)−1 at 0·700 Mc and (1·8+1.0−0.5 × 10−19 W m−2 (c/s)−1 at 2·200 Mc was observed. Assuming a galactic origin of the observed fluxes at both frequencies, the averaged sky brightnesses are b(0·700 Mc) = (6−3+5) × 10−20 W m−2 (c/s)−1 sr−1b(2·200 Mc) = (1.4+1.0−0.5 × 10−20 W m−2 (c/s)−1 sr−1 The observed brightness at 2·200 Mc is in reasonable agreement with the results of other observers. The apparent brightness at 0·700 Mc is, however, greater than was expected from previous observations. An alternative source of the 0·700 Mc flux in the terrestrial exosphere, as well as characteristics of several noise bursts observed during the flight, is briefly discussed. 相似文献
40.
With an appropriate system of higher order approximations the Faraday-effect is calculated for instantaneous ionospheric models the data of which are derived from the results of vertical soundings. Only one parameter which corresponds to the thickness of the outer ionosphere is left open; it is determined by global comparison with simultaneous Faraday-observations of satellite emissions. The thickness parameter shows various forms of variation with latitude; an increase towards north is the rule for quiet daytime conditions. Comparison with local methods shows considerable differences due to the indetermination of the absolute number of rotations. 相似文献