甘新蒙北山地区成矿带划分和基本特征对比

在对甘新蒙北山地区成矿地质背景和成矿在时空上的联系性等综合研究分析基础上,运用新理论、新认识,以板块构造单元划分为基础,将本区划分为3个Ⅲ级成矿带、11个Ⅳ级成矿带,并对Ⅲ级成矿带特征进行了阐述,以期为矿产勘查和地质大调查工作部署提供新的思路和依据。进一步就主要矿床(点)、构造单元、矿种、赋矿建造、控矿因素、成矿类型、成矿时代等方面进行了对比,认为各Ⅳ级成矿带在区域上具有相对稳定的展布范围,具有相同的构造环境和成矿条件、类似的矿种和成矿时代,存在一定的相似性、可比性,并且各成矿带具有一定的潜在找矿价值。     

On cross-correlating weak lensing surveys

The present generation of weak lensing surveys will be superseded by surveys run from space with much better sky coverage and high level of signal-to-noise ratio, such as the Supernova/Acceleration Probe ( SNAP ). However, removal of any systematics or noise will remain a major cause of concern for any weak lensing survey. One of the best ways of spotting any undetected source of systematic noise is to compare surveys that probe the same part of the sky. In this paper we study various measures that are useful in cross-correlating weak lensing surveys with diverse survey strategies. Using two different statistics – the shear components and the aperture mass – we construct a class of estimators which encode such cross-correlations. These techniques will also be useful in studies where the entire source population from a specific survey can be divided into various redshift bins to study cross-correlations among them. We perform a detailed study of the angular size dependence and redshift dependence of these observables and of their sensitivity to the background cosmology. We find that one-point and two-point statistics provide complementary tools which allow one to constrain cosmological parameters and to obtain a simple estimate of the noise of the survey.     

山区公路软基病害研究

随着高等级公路建设规模的扩大，山区公路所面临的路基病害特别是软土路基病害问题也逐渐增多。结合对陕南勉(县)一宁(强)高速公路工程实例分析，对山区软土成因及其特性进行了初步分析，认为山区软土属以坡洪积、湖积和冲积为主的软土，也有少量是由坡残积物堆积而形成。山区软土的特殊性表现在成分的复杂性、分布的不均匀性、隐蔽性和物理力学性质的特殊性。根据其特性以及中国山区公路软基普遍存在的病害问题，总结了山区公路软基的主要病害类型为剪切拉裂破坏、浸水沉陷破坏、剥蚀坍塌破坏、推挤滑动破坏。还提出了相应的软基处理方法及建议。     

Coma Morphology of Three Non-periodic Comets

The coma morphology and short-term evolution was investigated of three non-periodic comets in retrograde orbits, C/2001 Q4 (NEAT), C/2002 T7 (LINEAR), and C/2003 K4 (LINEAR). All three comets display distinct coma features, which were very different from one comet to the next and remained rather constant in shape during the observational period. A single, broad feature perpendicular to the sun-tail direction dominated the coma of C/2003 K4 in all used filters (B,V,R,I), whereas the coma of Comet C/2002 T7 exhibited different features in blue and red filters. C/2001 Q4 showed rather complex coma morphology with clear short-term variability in coma brightness. Therefore, these non-periodic comets neither show a featureless coma nor any similarities of the features detected. The overall distribution of coma material was investigated from the shape of radial coma profiles averaged around the comet nucleus. For C/2001 Q4 and C/2002 T7, the slopes fitted to the linear part of these profiles are flatter in the blue than in the red, which can be explained by the presence of coma gas. For C/2003 K4 no such difference is indicated in the May observations (r = 2.3 AU), while in July (r = 1.7 AU) the profiles in the B-filter are flatter than in V, R, and I, hence gas contamination was relevant at least in the B filter. The R and I filter images were used to determine approximate Afρ values of each comet as a function of time.     

Investigating the mechanisms leading to the deglaciation of past continental northern hemisphere ice sheets with the CLIMBER–GREMLINS coupled model

A coupling procedure between a climate model of intermediate complexity (CLIMBER-2.3) and a 3-dimensional thermo-mechanical ice-sheet model (GREMLINS) has been elaborated. The resulting coupled model describes the evolution of atmosphere, ocean, biosphere, cryosphere and their mutual interactions. It is used to perform several simulations of the Last Deglaciation period to identify the physical mechanisms at the origin of the deglaciation process. Our baseline experiment, forced by insolation and atmospheric CO₂, produces almost complete deglaciation of past northern hemisphere continental ice sheets, although ice remains over the Cordilleran region at the end of the simulation and also in Alaska and Eastern Siberia. Results clearly demonstrate that, in this study, the melting of the North American ice sheet is critically dependent on the deglaciation of Fennoscandia through processes involving switches of the thermohaline circulation from a glacial mode to a modern one and associated warming of the northern hemisphere. A set of sensitivity experiments has been carried out to test the relative importance of both forcing factors and internal processes in the deglaciation mechanism. It appears that the deglaciation is primarily driven by insolation. However, the atmospheric CO₂ modulates the timing of the melting of the Fennoscandian ice sheet, and results relative to Laurentide illustrate the existence of threshold CO₂ values, that can be translated in terms of critical temperature, below which the deglaciation is impeded. Finally, we show that the beginning of the deglaciation process of the Laurentide ice sheet may be influenced by the time at which the shift of the thermohaline circulation from one mode to the other occurs.     

中国大陆科学钻探先导孔零偏VSP资料解释

用六级三分量检波器在中国大陆科学钻探先导孔中实施了零偏VSP测量.数据处理结果表明,中国大陆科学钻探孔区超高压变质岩石的地震波速度主要介于4500～7000m/s之间,显著高于一般的沉积岩地区,而且随深度变化不明显.声波测井速度系统地稍低于VSP层速度,可能是由于井壁处岩石的完整性受到破坏而造成的.地震波速度与岩石密度和岩性存在明确的对应关系,榴辉岩的密度和地震波速度均显著高于片麻岩类岩石;由榴辉岩退变生成的斜长角闪岩类岩石,其密度和地震波速度均呈现出较大的变化,主要与其退变质程度有关;超基性岩中的裂隙系统导致其密度和地震波速度大幅度下降.由于榴辉岩与其他岩石类型之间存在较大的波阻抗差异,因此用零偏VSP资料标定该区地震波的地质层位是有效的.关于地震波反射的原因,通过综合研究地震波(包括反射纵波、上行转换横波、井筒波)的特征、岩石速度和密度分布以及井径变化,认为主要是岩性分界面、韧性剪切带和断裂(带),但还有一些因素尚待进一步研究.     

The 550-au Mission: a critical discussion

We have studied the science rationale, goals and requirements for a mission aimed at using the gravitational lensing from the Sun as a way of achieving high angular resolution and high signal amplification. We find that such a mission concept is compromised by several practical problems. Most severe are the effects due to the plasma in the solar atmosphere which cause refraction and scattering of the propagating rays. These effects either limit the frequencies that can be observed to those above ∼1 THz, or they move the optical point outwards beyond the vacuum value of ≥550 au. (Thus for observing frequency of 300 GHz the optical point is moved outwards to ∼ 680 au.) Density fluctuations in the inner solar atmosphere will further cause random pathlength differences for different rays. The corrections for the radiation from the Sun itself will also be a major challenge at any wavelength used, but could be mitigated with coronographic techniques. Given reasonable constraints on the spacecraft (particularly in terms of size and propulsion), source selection as well as severe navigational constraints further add to the difficulties for a potential mission. Nevertheless, unbiased surveys of small-scale structure on the sky at short wavelengths might be the most promising application of such a mission.     

柴达木盆地东北缘古元古代变质镁铁—超镁铁质岩的地质特征及成因探讨

1:5万区域地质调查工作中,在柴达木陆块北缘首次发现古元古代变质镁铁—超镁铁质岩,获得成岩年龄为1952±15Ma,其岩石化学、地球化学特征反映出岩浆来源于亏损地幔,反映出该地区克拉通在古元古代(19亿年)发生了一次强烈的裂解(洋)事件,对于研究柴达木盆地北缘元古代结晶基底地质构造演化及进一步探讨柴达木盆地的起源及构造演化过程提供了重要地质线索。     

青海省沙柳河南区有色金属矿成矿物质来源及矿床成矿模式探讨

本文简述了沙柳河南区有色金属矿床的基本特征。通过对成矿热液及成矿物质的来源与性质的研究,认为该矿床的成因类型为火山沉积—接触交代改造叠加型,进而探讨了该矿床的成矿模式。