排序方式: 共有54条查询结果,搜索用时 31 毫秒
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ZHANG Yuquan XIE Yingwen LI Xianhua QIU Huaning LIANG Huaying LI Jianping ZHAO Zhenhua DENG Wanming CHUNG Sunlin 《中国科学D辑(英文版)》2001,44(1)
The Cenozoic magmatic rocks of shoshonitic series in the easternQinghai-Tibet Plateau include potassic alkaline plutonic rocks, volcanic rocks, lamprophyres and acidic porphyries. Analytical results show that these different lithological rocks are extremely similar in Sr, Nd and Pb isotopic compositions with the range of 0.705 187-0.707 254 for 87Sr/86Sr, 0.512 305-0.512 630 for 143Nd/144Nd, 18.53-18.97 for 206Pb/204Pb, 15.51-15.72 for 207Pb/204Pb and 38.38-39.24 for 208Pb/204Pb. They are isotopically similar to the EMII end-member. This indicates that mantle metasomatism must have taken place in their source region. The formation of these particular rocks is related to crustal thinning and mantle upwelling in a large-scale strike-slip and pull-apart fault zone at about 40 Ma in northern and eastern Qinghai-Tibet Plateau. 相似文献
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Huaning Wang 《Solar physics》1995,157(1-2):213-222
Longitudinal components of highly stressed magnetic fields in the active region NOAA 7640 on 26 December, 1993 have been studied. A physical parameter is suggested for describing the longitudinal components recorded in longitudinal magnetograms obtained before and after a 1N/M1.5 flare. By means of this parameter, quantitative comparisons among the pre-flare magnetograms, the post-flare magnetograms, and filtergrams (in H) have been executed. The main results are as follows: firstly, the areas with high values of the parameter are near the regions with newly emerging magnetic flux. Secondly, the maximum values of the parameter in the areas and the sizes of the areas are evidently decreased after the flare. Finally, the original bright point of the flare is near the areas and the flare kernels cover the areas when the flare is growing. According to these results, we conclude that the variation of the parameter is connected with that of highly stressed magnetic fields in the region and directly related to the flare. 相似文献
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Occurrences of Excess ^40Ar in Hydrothermal Tourmaline: Interpretations from ^40 Ar-^39Ar Dating Results by Stepwise Heating 下载免费PDF全文
QIU Huaning PU Zhiping DAI Tongmo 《《地质学报》英文版》2007,81(3):510-516
The occurrences of excess ^40Ar within a hydrothermal tourmaline is discussed in term of the analysis data of syngenetic muscovite and tourmaline from the Lushui hydrothermal tin-tungsten deposit in western Yunnan, China, using the ^40Ar-^39Ar stepwise heating technique. About 80% excess ^40 Ar was released in the last step when the tourmaline was fused, corresponding to a release of only -3% ^39 Ar (K), which indicates that most excess ^40 Ar was held in the mineral lattice rather than in the channels parallel to the Z-axis. This suggests that the excess ^40 Ar was incorporated during crystallization and not diffused into the tourmaline during the post-crystallization history. 相似文献
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藏东玉龙铜矿带含矿斑岩及成岩系列 总被引:37,自引:4,他引:33
西藏东部新生代玉龙铜矿带含矿斑岩,包括玉龙、扎拉尕、莽总、多霞松多和马拉松多等,均为同期不同阶段侵入地质体构成的复式岩体。岩石类型有石英二长斑岩、二长花岗斑岩、正长花岗斑岩和碱长花岗斑岩。岩石化学成分均富碱(Na2O+k2O〉8%)、高钾和K2O/Na2O比值远大于1等,属于碱性钾质系列,即钾玄岩系列。 相似文献
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In this paper, we consider the mechanical response of granular materials and compare the predictions of a hypoplastic model with that of a recently developed dilatant double shearing model which includes the effects of fabric. We implement the constitutive relations of the dilatant double shearing model and the hypoplastic model in the finite element program ABACUS/Explicit and compare their predictions in the triaxial compression and cyclic shear loading tests. Although the origins and the constitutive relations of the double shearing model and the hypoplastic model are quite different, we find that both models are capable of capturing typical behaviours of granular materials. This is significant because while hypoplasticity is phenomenological in nature, the double shearing model is based on a kinematic hypothesis and microstructural considerations, and can easily be calibrated through standard tests. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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Magnetogram data of 517 bipolar active regions are analyzed to study latitude, magnetic flux, polarity separation dependence of tilt angle of the active regions with well-defined bipolar magnetic configurations. The data were obtained at Huairou Solar Observing Station in Beijing during 1988 to October 2001. By statistical analysis, it is found: (1) The tilt angle () is a function of the latitude (). Our observed result, sin=0.5 sin, is in good agreement with that obtained by Wang and Sheeley (1991). (2) The tilt angle is a function of the magnetic flux. The tilt angle increases (decreases) with flux increasing when the flux is smaller (larger) than 5×1021 Mx. (3) The tilt angle is a function of the magnetic polarity separation. The tilt angle increases (decreases) with the separation increasing when the separation is smaller (larger) than 8×109 cm. (4) The magnetic flux ( in 1020 Mx) is correlated to the magnetic polarity separation (d in Mm), following 20d
1.15. The result is close to the observed result of Wang and Sheeley (1989), 20d
1.3. (5) The tilt fluctuations are independent of the latitude, but depend slightly on the separation, which is similar to the result obtained by Fisher, Fan, and Howard (1995). (6) The distribution function of the ratio of net magnetic flux to total magnetic flux is almost centered around zero net flux. The imbalance of magnetic flux is lower than 10% for 47% of our samples; 31% of active regions are in imbalance of the magnetic flux between 10% and 20%. 相似文献
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Force-free magnetic fields can be computed by making use of a new numerical technique, in which the fields are represented
by a boundary integral equation based on a specific Green's function. Vector magnetic fields observed on the photospheric
surface can be taken as the boundary conditions of this equation. In this numerical computation, the following two points
are emphasized: (1) A new method for data reduction is proposed, for removing uncertainties in boundary data and determining
the parameter in this Green's function, which is important for solving the boundary integral equation. In this method, the
transverse components of the observed boundary field are calibrated with a linear force-free field model without changing
their azimuth. (2) The computed 3-D fields satisfy the divergence-free and force-free conditions with high precision. The
alignment of these field lines is mostly in agreement with structures in Hα and Yohkoh soft X-ray images. Since the boundary data are calibrated with a linear force-free field model, the computed 3-D magnetic
field can be regarded as a quasi-linear force-free field approximation. The reconstruction of 3-D magnetic field in active
region NOAA 7321 was taken as an example to quantitatively exhibit the capability of our new numerical technique. 相似文献
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Solar cycle distribution of great geomagnetic storms 总被引:1,自引:0,他引:1
The distribution properties of great geomagnetic storms (Dst≤−200 nT) and super geomagnetic storms (Dst≤−300 nT) across the
solar cycles (19–23) are investigated. The results show that 73.2% of the great geomagnetic storms took place in the descending
phase of the solar cycles. 72.7% of super geomagnetic storms occurred in the descending phase of the solar cycles. About 83%
of the great geomagnetic storms appeared during the period from the two years before solar cycle peak and the three years
after solar cycle peak time. 90.9% of the super geomagnetic storms appeared between the two years before solar cycle peak
and the three years after solar cycle peak. When a solar cycle is very strong, the phenomenon that great geomagnetic storms
concentrated during the period from the two years before the solar cycle peak time to the three years after the solar cycle
peak time is very prominent. The launch time of space science satellite is suggested according to the distribution properties
of great geomagnetic storms and super geomagnetic storms in solar cycles. 相似文献