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91.
92.
By combining the carbon cycle model with the records of carbonate and organic (kerogen) carbon isotope, this paper presents
the calculation of the fraction of organic carbon burial (f
org) of beds 23–40 at the global boundary stratotype section and point (GSSP) of the Permian-Triassic boundary at Meishan, Zhejiang
Province. The resulting calculation produces two episodes of f
org maxima observed to occur at beds 23–24 and 27–29, which respectively corresponds to the two episodic anoxic events indicated
by the flourish of green sulfur bacteria. Two episodic f
org minima occurred at beds 25–26 and 32–34, generally coincident with the flourish of cyanobacteria (bed 26 and upper part of
beds 29 to 34) as shown by the high value of 2-melthyhopnoanes. It appears that the f
org is related to the redox conditions, with greater f
org values observed under the reductive condition. The relationship between f
org and the total organic carbon (TOC) content was complex. The f
org value was low at some beds with a high TOC content (such as bed 26), while high observed at some beds with a low TOC content
(e.g. bed 27). This association infers the important contribution of primary productivity to the TOC content. The original
organic burial could be thus calculated through the configuration of the function of the primary productivity and f
org, which can be used to correct the residual TOC measured today. This investigation indicates that compiling the organic-inorganic
carbon isotopes with the carbon cycle model favors to understand the fraction of organic carbon burial, providing information
for the reconstruction of the coupling among biota, environments and organic burial.
Journal of China University of Geosciences, 2007, 32(6): 767–773 [译自: 地球科学—中国地质大学学报] 相似文献
93.
玉龙铜(钼)矿带的成因机制和动力学背景一直存在争议。本文选择目前研究程度较低的多霞松多岩体, 对该岩体含矿斑岩开展岩相学、年代学、岩石地球化学及锆石Hf同位素分析。研究表明, 多霞松多岩体主要由二长花岗斑岩和碱长花岗斑岩组成, 其中, 二长花岗斑岩的主要造岩矿物为钾长石、斜长石和石英, 碱长花岗斑岩的主要造岩矿物为钾长石和石英。两种岩石属于高钾钙碱性-钾玄质侵入岩, 具有富碱高钾的特征; 亏损Nb、Ti等高场强元素, 富集Rb、Th、U等大离子亲石元素和Pb; 稀土元素含量较高(ΣREE=145.04×10-6~290.91×10-6), 富集轻稀土(LREE/HREE=6~37)。铕表现为从二长花岗斑岩的弱负异常(Eu/Eu*=0.66~0.84)到碱长花岗斑岩的中等负异常(Eu/Eu*=0.35~0.39)。锆石U-Pb定年显示, 二长花岗斑岩的成岩年龄为38.3±0.6 Ma, 碱长花岗斑岩的成岩年龄为37.8±1.0 Ma, 两者形成时代基本一致, 均属于喜马拉雅期, 表明在多霞松多地区始新世存在一期重要的岩浆热液Cu-Mo成矿事件。多霞松多含矿斑岩的锆石εHf(t)范围在+1.3~+2.6之间。结合元素和同位素地球化学特征, 指示多霞松多含矿斑岩可能来源于亏损地幔分异的新生玄武质下地壳, 受控于印度板块与欧亚板块碰撞诱发的金沙江走滑断裂系统。
相似文献94.
An accurate prediction of the thermal conductivity of reservoir rocks in the subsurface is extremely important for a quantitative analysis of basin thermal history and hydrocarbon maturation. A model for calculating the thermal conductivity of reservoir rocks as a function of mineral composition, porosity, fluid type, and temperature has been developed based on fabric theory and experimental data. The study indicates that thermal conductivities of reservoir rocks are dependent on the volume fraction of components (minerals, porosity, and fluids), the temperature, and the fraction of series elements (FSE) which represents the way that the mineral components aggregate. The sensitivity test of the fabric model shows that quartz is the most sensitive mineral for the thermal conductivity of clastic rocks. The study results indicate that the FSE value is very critical. Different lithologies have different optimum FSE values because of different textures and sedimentary structures. The optimum FSE values are defined as those which result in the least error in the model computation of the thermal conductivity of the rocks. These values are 0.444 for water-saturated clay rocks, 0.498 for water-saturated sandstones, and 0.337 for water-saturated carbonates. Compared with the geometric mean model, the fabric model yields better results for the thermal conductivity, largely because the model parameters can be adjusted to satisfy different lithologies and to minimize the mean errors. The fabric model provides a good approach for estimating paleothermal conductivity in complex rock systems based on the mineral composition and pore fluid saturation of the rocks. 相似文献
95.
托里活断层、达尔布特活断层、独山子—安集海活断层及霍尔果斯—卡子湾活断层是塔城地区主要的全新世活断层,均有过多次古地震活动。自1977年以来,4级以上地震活动的空区在裕民县西北。据活断层古地震活动复现期及地震活动围空特点分析,今后10年北天山或塔城西北可能有发生6级左右地震的危险。 相似文献
96.
在归纳1954年山丹71/4级地震已有地震史料的基础上,根据新获得的朱允明(2006)《山丹地震考察笔记》的详细考察资料,按照《新中国地震烈度表》重新评定了本次地震中各考察点的地震烈度,重新绘制了该地震的等震线图。其中,极震区Ⅸ—Ⅹ度区长轴方向为北西向,呈扁椭圆形,长轴直径约40km;Ⅷ度区南西侧为山丹盆地,第四纪沉积较厚,地震烈度衰减缓慢,因此,Ⅷ度区等震线向南明显突出。1954年山丹71/4级地震极震区位于龙首山北缘断裂西段,大致与该断裂的包代河-黑头山段相吻合,综合分析认为,该段断裂是本次地震的主发震断层,而破喇嘛顶西缘断裂和毛湖洞断裂是重要的参与断裂。 相似文献
97.
98.
The turbulence field of airflow in the lee of a dune has significant impacts on dune dynamics and related processes. We used particle image velocimetry in a wind tunnel simulation to obtain detailed velocity measurements in the lee of two‐dimensional transverse dune models, then used the results to analyse their turbulence fields. The dune models used in this study had a single lee angle of 30°, and a total of six stoss angles: 3°, 5°, 10°, 15°, 20° and 25°. We used vorticity, turbulence intensity, Reynolds stress and turbulent kinetic energy to characterize the turbulence fields. These parameters were functions of stoss angle, wind velocity, distance from the dune crest and height above the ground surface. The stoss angles could generally be divided into two groups based on the profiles of mean velocity, turbulence and Reynolds stress. Stoss angles of 3° and 5° usually had similar profiles, and angles of 15°, 20° and 25° formed a second group with similar profiles. The profiles for the stoss angle of 10° were usually transitional and were intermediate between the two groups. Vorticity, Reynolds stress and turbulent kinetic energy increased monotonically with increasing free‐stream wind velocity, but their variations with respect to the stoss angle were complex. The stoss angles of 15° and 20° had the maximum values of these three parameters, thus these angles may have special significance in dune development given the characteristics of the mean velocity fields and turbulence fields they produce within the lee airflow. It is the streamwise velocity component and its turbulence that determine the surface shear stress. Copyright © 2008 John Wiley and Sons, Ltd. 相似文献
99.
Introduction Greeting the coming of the 21st century, Professor HU Yu-xian and other Chinese scholars briefed the trend of earthquake engineering in China and aboard (HU, 1999; HU, ZHOU, 1999). The experiences and lessons learning from the destructive earthquakes in China and abroad in re-cent years, the damage action of the large velocity impulse in ground motion in near field in seis-mic design, numerous earthquake examples show that there are many weaknesses in aspects of earthquake p… 相似文献
100.
Study of the Earth’s free core nutation by tidal gravity data recorded with international superconducting gravimeters 总被引:2,自引:0,他引:2
By stacking high-precision tidal gravity observations obtained with superconducting gravimeters at six stations in China,
Japan, Belgium, France, Germany and Finland, the local systematical discrepancies in the parameter fitting, caused by atmospheric,
oceanic tidal loading and the other local environmental perturbations, are eliminated effectively. As a result, the resonance
parameters of the Earth’s free core nutation are accurately determined. In this study, the eigenperiod of free core nutation
is given as 429.0 sidereal days, which is in agreement with those published in the previous studies. It is about 30 sidereal
days less than those calculated in theoretical models (about 460 sidereal days), which confirms the real ellipticity of the
fluid core of the Earth to be about 5% larger than the one expected in assumption of hydrostatic equilibrium. The quality
factor (Q value) of free core nutation is given as about 9543, which, compared with those determined before based on the body
tide observations, is much larger, but more close to those obtained using the VLBI observations. The complex resonance strength
is also determined as (−6.10×10−4, −0.01 ×10−4)°/h, which can principally describe the deformation characteristics of an anelastic mantle. 相似文献