On the relationship between 100-hPa South Asia High and Mei-yu in Jiangsu province

By analyzing the change of an index for the characteristics of South Asia High and variations of upper-air troughs in 2002–2005,we studied the impact of South Asia high on the beginning and ending of the Mei-yu(i.e.sustained rain corresponding to the ripening season of plum)in Jiangsu province.Statistic verification is conducted on the relationships between the index and the Mei-yu season in 1991–2005 to examine the impacts of the SAH characteristics index on a rain intensity index of Mei-yu and regional distribution of a characteristics index for different annual patterns of Mei-yu.Historical composite is performed of the 100-hPa circulation field for these patterns using the 100-hPa geopotential height of Northern Hemisphere from 2002 to 2005 and 45-year NCEP reanalysis to study the difference in the circulation for different patterns of Mei-yu.Diagnostic and statistic conclusions,which share much in common,have been obtained as follows.(1)The characteristics preceding to and the advancement/retreat of SAH and the movement of westerly troughs are the factors that influence the onset time of the Mei-yu season;after the Mei-yu onset,the progression/withdrawal of SAH and how farther east it extends are determining how long the Mei-yu lasts and when it ends.(2)During the Mei-yu,the general 100-hPa circulation situation and average characteristics of the SAH are well corresponding to the characteristics of the season and annual patterns of Mei-yu.In addition,the averages of the SAH ridgeline and east-extending index for June,July and the Mei-yu season have some implications to the forecast of the index of Mei-yu intensity.These conclusions can be served as powerful means in determining the starting/ending dates, duration and annual pattern of the Mei-yu season.     

轮古东走滑断裂破碎带结构及与油气关系

利用最新处理完成的轮古东300 km2叠前深度偏移地震资料,多手段识别出轮古东气田发育3期4组断裂。断裂控制了裂缝走向与裂缝发育密度,裂缝主要为高角度(45°~75°)构造窄裂缝,沿裂缝存在溶蚀,走向主要为NESW。纵向上,一间房组裂缝发育密度最大(14条/100 m),其次为鹰山组(6条/100 m)和良里塔格组(4条/100 m);平面上,裂缝主要分布在主干断裂周边1 km范围内,随着距断裂距离增大,裂缝发育强度(裂缝线密度)呈指数降低。在此基础上,综合考虑主干断裂及伴生裂缝发育特征,将轮古东断裂破碎带平面上划分为"羽状破碎带、转换破碎带、斜列破碎带、复合破碎带"4种结构,羽状破碎带分布面积最广,是油气最富集的区域,是目前高效井的集中分布区,围绕羽状破碎带的钻探为走滑断裂控储控藏研究和寻找新的油气富集区域提供了新思路。     

Regional Tectonic Transformation in East Kunlun Orogenic Belt in Early Paleozoic: Constraints from the Geochronology and Geochemistry of Helegangnaren Alkali-feldspar Granite

The Helegangnaren feldspar granite exposed in the eastern part of East Kunlun, is characterized by high concentrations of SiO2 and alkaline, low abundances of Fe, Mg and Ca, metaluminous-weak peraluminous. Trace elements analysis shows that the granite is depleted extremely in Ba, Sr and Eu, and rich in some large-ion lithophile elements and high field strength elements. Besides, the granite has high Ga contents, the values of 104(Ga/Al) vary from 2.50 to 2.77, which is mainly greater than the lower limit of A-type granites (2.6), and is higher than the I- and S-type granites’ average (2.1 and 2.28, respectively). Rare earth element (REE) is characterized by relatively high fractionations of light REE (LREE) and heavy REE (HREE) (LREE/HREE=9.3–13.60, (La/Yb)N=10.92–18.02), pronounced negative Eu anomalies (δEu=0.08–0.13), and exhibits right-dipping gull pattern. Major elements, rare elements and trace elements features show the granite is ascribed to A-type granite and A2 subtype in tectonic genetic type. They are plotted into post-collision or within-plate area in a variety of tectonic discriminations. Geological and geochemical data comprehensively suggest that the granite is formed in a post-collision extensive tectonic setting. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U-Pb dating yields a weighted mean age of 425?Ma, belonging to Middle Silurian, which is similar to the age of the post-collision geological events in the region. The differences of magmatic rocks in formation age, rocks assemblage and rocks series systematically indicate that the regional tectonic stress regime in the East Kunlun orogenic belt experienced a major transformation from compress to extension in Middle Silurianin, and the Helegangnaren feldspar granite intruded in the early stage of tectonic transformation.     

中国花岗岩型铀矿区域地球化学指示元素特征及异常模式

我国铀矿床主要划分为四大类型,包括花岗岩型铀矿床、火山岩型铀矿床、砂岩型铀矿床和碳硅泥岩型铀矿床。花岗岩型铀矿约占我国已探明铀矿总资源储量的三分之一以上,是我国重要的铀矿化类型。地球化学勘探方法对花岗岩型铀矿床勘查具有良好的效果。根据全国铀矿资源潜力评价项目研究成果,在大量研究中国花岗岩型铀矿化水系沉积物地球化学异常特征基础上,总结了一套对花岗岩型铀矿化勘查稳定的、行之有效的指示元素及其组合,确定了花岗岩型铀矿化地球化学异常模式,并以实例说明典型花岗岩型铀矿化异常模式。水柰沉积物地球化学异常是进行铀矿产预测评价的有效手段,对铀矿资源的潜力评价发挥了重要作用。     

CO2 processes in an alpine grassland ecosystem on the Tibetan Plateau

In this paper, the CO2 concentrations profile from 1.5 m depth in soil to 32 m height in atmosphere were measured from July 2000 to July 2001 in an alpine grassland ecosystem located in the permafrost area on the Tibetan Plateau, which revealed that CO2 concentrations varied greatly during this study period. Mean concentrations during the whole experiment in the atmosphere were absolutely lower than the CO2 concentrations in soil, which resulted in CO2 emissions from the alpine steppe soil to the atmosphere. The highest CO2 concentration was found at a depth of 1.5 m in soil while the lowest CO2 concentration occurred in the atmosphere. Mean CO2 concentrations in soil generally increased with depth. This was the compositive influence of the increasing soil moistures and decreasing soil pH, which induced the increasing biological activities with depth. Temporally, the CO2 concentrations at different layers in air remained a more steady state because of the atmospheric turbulent milking. During the seasonal variations, CO2 concentrations at surface soil interface showed symmetrical patterns, with the lowest accumulation of CO2 occurring in the late winter and the highest CO2 concentration in the growing seasons.     

秦祁接合带造山缝合带磁组构特征及其构造意义

结合构造及磁化率各向异性研究详细解剖了秦祁接合带唐藏—关子镇—武山和新阳—元龙造山缝合带的应变及岩组特征.41个采点168个构造岩样品的平均磁化率全部较低,磁化率椭球形态分析表明其以平面和压扁应变为主,磁化率各向异性度普遍较高,属强变形岩石组构类型,结合野外观察认为其与变形强度明显正相关.此外,磁化率各向异性参数T、P′可能受岩石类型一定程度的影响.磁化率椭球主轴方位与变形密切相关,提供了丰富的岩组信息.两构造带具有类似的岩组特征,磁面理大致分为呈共轭形态的两组,暗示高应变剪切带在平面上可能以网格状形态出露;高倾伏角磁面理与占优势的低倾伏角、近水平磁线理表明了构造带明显的走滑特征,部分高角度磁线理可能与构造带的挤压和（或）转换挤压相关;磁组方法不能简单用于判别复杂强变形带的运动指向,糜棱面理的复杂变化及K_min与构造带夹角过高使其判别结果意义不明,而野外及显微构造观察都表明了构造带的右行走滑特征.上述结果表明,沿缝合带大规模的右行转换挤压形成了秦祁接合带反“S”型的平面构造形态,暗示在南北板块拼合过程中,西秦岭诸中、小块体一定程度的向西挤逸.     

山西岩溶水强径流带的成因类型及其水文地质特征

根据成因特征,将山西岩溶水强径流带分为五种类型: 接触带型、河谷型、构造带型、向斜谷地型和复合型。通过野外调查及对大量实测资料的分析研究,揭示出山西岩溶水强径流带的主要发育与分布特征: 岩溶水强径流带呈网状分布;发育深度50～300m;地下水面呈槽谷型,水力坡度一般在0. 6‰～2. 8‰之间。岩溶强径流带水量丰富,单井出水量大于1000m3 /d,是建立岩溶水水源地的理想场所。      

川东三叠系飞仙关组碳酸盐岩的阴极发光特征与成岩作用

四川盆地东部三叠系飞仙关组是近年来我国发现的重要天然气储层, 高孔隙度、高渗透率的碳酸盐储层都分布于白云岩地层中, 因而碳酸盐的成岩作用, 尤其是白云岩化作用和白云岩的成因为石油地质学家和沉积学家高度关注.对四川盆地东部罗家寨构造三叠系飞仙关组42个碳酸盐岩样品进行了阴极发光分析, 结合与之有关的Mn、Fe、Mg元素分析和岩石学研究, 讨论了包括白云岩化作用在内的碳酸盐岩成岩过程中可能的成岩流体性质及来源.四川盆地东部三叠系飞仙关组碳酸盐岩普遍具有很弱的阴极发光性, 这与其很低的Mn、Fe含量有关, 说明沉积期后非海相流体对飞仙关组碳酸盐岩的影响非常有限, 海源流体在成岩过程中发挥了主导作用; 不同石灰岩类型和不同白云岩类型仍然具有不同的阴极发光性, 成岩组分含量越高的碳酸盐岩, 或者说与沉积期后流体(主要是孔隙流体) 关系越密切的碳酸盐岩的阴极发光强度越低, 说明随着埋藏成岩作用的进行, 四川盆地东部三叠系碳酸盐岩孔隙流体受海源流体的影响是逐渐增强的; 阴极发光分析结果表明, 作为四川盆地东部主要储集岩的结晶白云岩形成机制与埋藏过程中的深循环流体有关, 这种深循环流体没有或很少穿越铝硅酸盐地层, 但穿越了三叠系内部的某些海相地层, 这些海相地层可能是广泛存在于四川盆地三叠系的蒸发盐地层, 由蒸发盐成岩过程提供的海源流体参与了结晶白云岩的白云岩化作用.      

溪洛渡水电站某危岩体稳定性及加固措施研究

在现场调查分析的基础上,提出了溪洛渡水电站某危岩体的两种可能失稳模式（剪切坠落或拉裂倾倒失稳）,进而建立了相应的稳定性计算极限平衡力学模型,而且对危岩体的变形和破坏特征进行了数值模拟分析,分析结果表明,危岩体抗拉裂倾倒稳定性较差,剪切坠落失稳的稳定性系数较高。在稳定性分析的基础上,计算出危岩体倾倒失稳时,安全系数为1.5时的锚固力,进而提出了危岩体加固方案：充填凹岩腔+填充裂隙+预应力锚索＋锚杆联合加固,数值模拟表明此加固方案效果良好。