鼎湖山亚热带森林土壤有机质^14C年龄初步研究   总被引：3，自引：0，他引：3  

邢长平  沈承德  孙彦敏  姜漫涛  易惟熙 《地球化学》1998,27(5):493-499

对鼎湖山亚热带森林土壤有机质（SOM）放射性碳进行了核爆效应校正。各层位年龄值与土壤深度呈线性递减,成壤过程是连续的,也是全新世时期的产物。五棵松剖面和坑口剖面成壤速率分别为0．0233cm／a和00488cm／a。成壤速率的差异可以用微地形和植被等主要因素的不同来解释。红壤有机物由活跃和稳定两种组分组成,其分解速率分别为0.25—0．57a-1和1．51×10－3—18×10-3a-1,平均滞留时间分别为1．8—4.0a和556-667a。  相似文献   

镜质体反射率在重建盆地古地温中的应用──中国东部、西部中、新生代沉积盆地古地温特征   总被引：6，自引：0，他引：6  

邹华耀  吴智勇 《沉积学报》1998,(1)

在总结前人关于镜质体反射率重建盆地古地温方法的基础上,讨论了各方法的理论基础、应用效果及其局限性。选择理论上与实际应用效果较好的EasyR0方法,重建了东部苏北盆地、辽河盆地和西部柴达木盆地、三塘湖盆地典型探井的古地温演化模式。结果表明我国东部中、新代大陆架谷型盆地,具有比酉部中、新生代前陆型盆地更高的古地温梯度。中生代末至第三纪早期,东部盆地的古地温梯度大于4．0℃／100m,而西部盆地的在3．0～2．5℃／100m。我国中、新生代沉积盆地古地温普遍具有从高到低的演化趋势,而柴达木盆地则相反,古地温梯度自早第三纪的2．5℃／100m升高到现今的3．0℃／100m。这几个盆地古地温的成功恢复,证实EasyR0方法对热演化各异的不同类型盆地古地温恢复具有广泛的适应性,而且,准确性高。过去常用的TTI－R0方法过高地计算了有机质的成熟度,使重建的古地温偏低。  相似文献   

1∶5万化探扫面在桂西北地区的找矿效果及意义     

彭志永 《南方国土资源》1998,(1)

概述１∶５万化探扫面在桂西北地区的工作方法及找矿效果,通过实例来说明开展１∶５万化探扫面的重要意义。经过对１∶５万化探扫面的投资和其产生的效益进行详细比较,得出１∶５万化探扫面这种找矿手段投资少、效益高的结论,建议广泛开展。  相似文献   

Geochemistry of Jinman Copper Vein Deposit West Yunnan province,China—Ⅱ.Fluid Inclusion and Stable Isotope Geochemical Characteristics   总被引：1，自引：0，他引：1  

Ji Hongbing  Li Chaoyang 《中国地球化学学报》1998,17(1):81-90

The Jinman deposit is a Ag-bearing copper vein deposit located at the north margin of the Lanping-Simao back-arc basin in West Yunnan. Systematic studies of fluid inclusions and stable isotopes are presented in this paper. The filling-replacement stage and the boiling-exhalative precipitation stage of mineralization took place atT ₁ = 140–280°3 andT ₂ = 94–204°C under pressure of (600 – 1200) x 10⁵ Pa. The salinity of ore-forming solutions ranges from 5 wt% –20.8 wt% (NaCl). Sulphide δ³⁴S(CDT) values are in the range of -9.6%.– +11.03%. with a range of 22. 66%. showing an apparent “pagoda”-shaped distribution in histogram. Meanwhile, the δ³⁴S values of the various sulphides are consistent with the characters of isotope equilibrium fractionation, i.e., δ³⁴ S_Py>δ³⁴S_Cp>δ³⁴S_Bn. The TS/TOC ratios of the ores are widely variable between 0.16 and 5.54 with no correlation of any kind can be established. According to the model of Ohmoto, the oxidation-reduction ratios of sulfur species in ore-forming solutions at the two mineralization stages were calculated to be R′₁ = 2.16 x 10^-17 and R′₂ = 1.55 x 10⁴. δ¹³Coo₂(PDB) values obtained from fluid inclusions in calcite and quartz are between -8.12%.-3.18%., averaging -5.26%., which are comparable with the isotopic composition of mantle-derived CO₂. Inclusions in quartz yield δ¹³CCH₄ (PEB) between -32. 11%. and -22.04%. (averaging -26.69%.), similar to that of methane in modern geothermal gases. For the ore-forming solutions, δ¹⁸ OH₂O (SMOW) values are between -10.57%. and +9.77%. and δDH₂O (SMOW) are between -51%. and -135%. Considering the effect of isotope exchange during water-rock reactions, most of the data are plotted along or close to the line defined by the reaction of meteoric water with clastic rocks, while a small part of the points fall near the reaction line of magmatic water with clastic rocks. In δ¹³C vs. δ18O diagram, the ore-forming solutions are plotted for the most part into the mixing area between the meteoric fluid and the deep-seated fluid and partially on the mixing line of P = 1. This project was founded by the “Eighth Five-Year Plan Period” State Key Program (85–901) and the Open Lab. of Ore Deposit Geochemistry, Chinese Academy of Sciences.  相似文献   

水泥土搅拌桩复合地基的优化设计     

连长江  张孝华 《上海国土资源》1998,(4):33-37

运用双层地基模型的线弹性有限元程序对不同类型水泥土搅拌桩复合地基的沉降进行计算,分析了水泥土搅拌桩的桩长、置换率、桩身刚度对地基沉降的影响,同此确定了搅拌桩的有效桩长、最优置换率、最优桩身刚度。  相似文献   

X-ray spectroscopy of the broad-line radio galaxy 3C 111     

C. S. Reynolds  K. Iwasawa  C. S. Crawford  & A. C. Fabian 《Monthly notices of the Royal Astronomical Society》1998,299(2):410-416

We present an ASCA observation of the broad-line radio galaxy 3C 111. The X-ray spectrum is well described by a model consisting of a photoelectrically absorbed power-law form. The inferred absorbing column density is significantly greater than expected on the basis of 21-cm measurements of Galactic H  I . Whilst this may be the result of intrinsic absorption from a circumnuclear torus or highly warped accretion disc, inhomogeneities and molecular gas within the foreground giant molecular cloud may also be responsible for some of this excess absorption. We also claim a marginal detection of a broad iron Kα line which is well explained as being a fluorescent line originating from the central regions of a radiatively efficient accretion disc. This line appears weak in comparison to those found in (radio-quiet) Seyfert nuclei. We briefly discuss the implications of this fact.  相似文献   

Constraints on a soft X-ray excess in the quasar 3C 279     

A. J. Lawson  & I. M. MHardy 《Monthly notices of the Royal Astronomical Society》1998,300(4):1023-1026

We present the results of a three-week daily monitoring campaign of the quasar 3C 279 by the X-ray satellites RXTE ROSAT . A cross-correlation provides no evidence for any time lag between the very similar soft and hard X-ray light curves, and the source shows no significant spectral variability over the observing period. There is no evidence to support the presence of a soft excess, with a 99 per cent upper limit on any such component of 25 per cent of the total observed luminosity in the 0.1–2 keV band (<3 × 10³⁸ W). This fraction (but not the luminosity) is significantly lower than that of the soft excess observed in 3C 273.  相似文献   

Estimation of codaQ using the maximum likelihood method     

Motoaki Takahara  Kiyoshi Yomogida 《Pure and Applied Geophysics》1992,139(2):255-268

A seismic coda wave from local earthquakes is an indication of heterogeneity in the crust and upper mantle, and codaQ (Q _c ) is the parameter defining the temporal decay of the coda wave. ButQ _c estimates obtained with the conventional least-square method are not based on any solid statistical background, assuming the Gaussian distributiona priori. In this study, we propose a statistically reliable estimation method of estimatingQ _c using the maximum likelihood method, and show its validity and usefulness with the data from the 1986 Joint Seismological Research in the western Nagano Prefecture. We found first that theQ _c estimation with the maximum likelihood method is statistically valid and its reliability can be checked with the -square test. Next,Q _c around Ohtaki village, within the studied area, is estimated using the maximum likelihood method. The averageQ _c value at low frequencies (up to 2 Hz) is one of the lowest in the world, which is in harmony with the geological setting of the site condition directly above an active fault.  相似文献   

On the reliability of different methods of seismic hazard assessment in Greece     

B. C. Papazachos  Ch. A. Papaioannov  D. J. Papastamatiou  B. N. Margaris  N. P. Theodulidis 《Natural Hazards》1990,3(2):141-151

Historical and present century instrumental data have been used to determine seismic hazard in 35 sites of Greece by the application of Cornell's method (Cornell, 1968) and the mean value method. The macroseismic intensity has been considered as a measure of seismic hazard. Comparison of the results of the two methods showed that, in general, the mean value method gives higher values, particularly for low probabilities of exceedance. In addition, for some sites, the differences of the expected intensities resulting from the two methods, indicate that finer tuning of the seismogenic souce model is required, or suggest time dependence. Although each one of these methods has its own merits, the method based on seismic zonation (Cornell's method) has several advantages and must be preferred when an accurate zonation is possible by the use of macroseismic and instrumental seismic data, together with geological and geomorphological information. However, reliable estimates of seismic hazard at a particular site require work on a microzoning scale, incorporating historical, archaeological, and recent geological data.Paper presented at the 21st General Assembly of the European Seismological Commission held in Sofia, 1988.  相似文献   

Evaluation of All-Sky Assimilation of FY-3C/MWHS-2 on Mei-yuPrecipitation Forecasts over the Yangtze-Huaihe River Basin     

Yu LI  Keyi CHEN  Zhipeng XIAN 《大气科学进展》2021,38(8):1397-1414

正1School of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu 610025, China2International Center for Climate and Environment Sciences, Institute of Atmospheric Physics,Chinese Academy of Sciences, Beijing 100029, China3University of Chinese Academy of Sciences, Beijing 100049, China  相似文献