The Role of T_(50) in the Classification of Gamma-ray Bursts

The role of T50 in classifying gamma-ray bursts (GRBs) is investigated. We take T50=0.7s as the line of division and find that some bursts belonging to the class of long bursts defined by T90≥2s now become short bursts (sample 1), while some belonging to the class of short bursts defined by T90 < 2 s now become long bursts (sample 2). We study how these sources are affected by the two methods of classification and find the change of classes of sample 1 is due to some peculiar properties of the light curves. Based on their characters, most of the bursts of sample 1 should be taken as short bursts.     

波前相位差法探测器的设计

波前相位差法是利用焦面像和离焦面像通过一个相位多样性算法来拟合相位或对目标复原,这就要求采集两个图像,一个是焦面像,另一个是离焦面像。本文的设计是根据晶体的偏振原理分像,并将焦面像和离焦像同时采集到同一个CCD(Charge Coupled Device)上,这种方法保证了两个图像的同步、实时,而且光学系统简单。文中具体给出了一种新型波前相位差法探测器的设计方案、像差分析,并且模拟了波前相位差法探测器对模拟结果的影响。     

滇西北衙金多金属矿床流体包裹体研究

北衙金多金属矿是与滇西新生代富碱斑岩有关的典型代表之一。通过对矿区石英脉、富碱斑岩中的石英斑晶以及方解石脉中流体包裹体的类型、特征、温度、盐度、成矿压力以及流体包裹体中气液相成分分析和包裹体的激光拉曼探针分析,探讨了流体性质、来源。研究表明,该区存在高温高盐度流体、中高温高盐度流体、中低温低盐度流体3种流体。流体总体属于NaCl-H2O体系,均一温度范围在132～550℃(个别大于550℃),盐度范围在1.9%～61.1%(NaCleq)。高盐度流体不是由热水溶液的不混溶作用或沸腾作用形成的,而是由中酸性岩浆在深部岩浆房中通过结晶分异作用形成,和/或在浅成条件下于岩浆结晶的最后阶段从浅部岩浆中直接出溶形成的。红泥塘、南大坪两矿段石英斑晶中金属子矿物特别是黄铜矿的发现,暗示早期来自岩浆的热液流体金属含量较高,形成于大气降水与岩浆热液混合之前。上述特征表明北衙地区富碱斑岩具有巨大成矿潜力。     

Devonian alkaline magmatism in South Qinling,China: evidence from the Taohekou Formation,Northern Daba Mountain

The Langao area in South Qinling consists of a poorly dated sequence of volcano-sedimentary units (Taohekou Formation). This study focuses on volcanic edifice of Taohekou Formation. Detailed field mapping, section facies analysis, geochemistry, and Ar–Ar geochronology is presented here to develop a more accurate understanding of the tectonic evolution of the Qinling Orogen. Detailed field mapping and section facies analysis reveals the presence of a seamount volcanic edifice in western Xiaozhen area. Ar–Ar dating of alkaline basalts in the sequence indicates an Early Devonian magmatic age. Whole rock geochemistry of these alkaline basalts indicates that both potassic and sodic basalts were erupted respectively in the eastern and western areas. Both types of samples are typically characterized by high concentrations of TiO₂, Nb, Ta, and Zr. Ocean-island basalt (OIB)-like rare earth element distribution patterns, trace element spider diagrams, and similar Sr and Nd isotopic compositions (i.e. relatively low Sr and moderate Nd isotopic ratios) likely indicate that the samples were comagmatic but have experienced varying degrees of fractional crystallization. In addition, the samples appear to have all originated from the asthenospheric mantle and undergone mantle metasomatism, ultimately resulting in an OIB-type provenance. Most importantly, in combination with its regional tectonic evolution, the Taohekou Formation is constrained to a seamount environment. This formation does not represent a plume but, rather, an extensional fracture zone related to subduction. Thus, this geologic interpretation generates pivotal evidence for accurately investigating the properties and temporal constraints of the Mianlue oceanic basin.     

腾冲热海地区NW向断裂活动性的地球化学证据

腾冲热海是中国最著名的火山地热区 ,近期区内水热流体活动异常强烈。研究区内几乎所有 95℃以上的沸泉、喷沸泉以及 1993年以来发生的 2 0余次水热爆炸点均沿NW向断裂分布 ,显示该断裂目前处于强烈活动之中。钍、氡射气测量结果确定了NW向断裂的存在和具体位置。研究认为 ,NW向断裂的形成和异常活动可能与火山区壳内岩浆活动有关     

米仓山地区早寒武世仙女洞组古地理和沉积物源分析

关于米仓山早寒武世地层的物源区母岩,长期以来持有的观点认为主要来自东北汉南古陆和(或)西北摩天岭古陆(碧口地块)。然而,仙女洞组的岩相古地理等确定的物源方向并不支持。灰色泥岩和灰色灰岩,发育水平层理,沉积环境为泻湖;灰色厚层鲕粒灰岩等(发育板状交错层理和鲕状交错层理)、沉积环境为鲕粒滩;灰色中-厚层角砾状灰岩和砾屑灰岩等,发育滑塌构造,沉积环境为碳酸盐斜坡。区域古地理指示,沿福庆-正源-大两-杨坝-桥亭一线向北东方向,沉积水体逐渐变深,古地理由泻湖、鲕粒滩逐渐过渡为碳酸盐斜坡。交错层理恢复的古潮流指示,潮流主要为西北和西南方向。重矿物组成和电子探针分析结果表明,以花岗岩和变砂岩、泥岩为主。综合分析表明,仙女洞组的物源主要来自西北碧口地块和西南康滇古陆的花岗岩、变质砂岩和变质泥岩,且经历再旋回过程。     

那西郭勒沉积变质型铁-石墨矿床成矿特征及找矿方法组合

那西郭勒铁-石墨矿床位于伯喀里克-香日德印支期金、铅、锌(铜、稀有、稀土)成矿带(Ⅲ12)的西端。铁、石墨矿体主要赋存于金水口岩群地层中的条带状磁铁石英岩、石英片岩、斜长角闪片岩、斜长角闪岩和大理岩中。矿体产出受地层岩性控制,成矿经历了热水喷流沉积期、变质作用期和构造-岩浆变形-改造期三个阶段,矿区地磁异常明显,并具带状分布特征,同时分布有规模较大的激电异常,槽探揭露和钻探验证表明,激电异常与石墨矿带具有一定的对应性,铁、石墨矿体表现为明显的低阻高极化特征。在矿床发现及勘查过程中,磁法测量、激电测量发挥了重要作用。通过归纳总结得出东昆仑地区沉积变质型铁-石墨矿床有效的勘查方法组合为:①通过成矿地质背景及找矿模型的研究,确定找矿远景区;②开展1∶50 000高精度磁测圈定磁异常并划分成矿有利地段;③进行1∶10 000地面高精度磁测和激电剖面测量工作,进一步缩小靶区;④进一步开展1∶2 000磁电剖面测量,详细了解异常特征,进行磁异常的2.5D反演解释;⑤利用钻探进行验证,确定矿体或矿床。该方法组合经济有效并能够提高找矿成功率。     

三江并流带丹霞地貌景观地质成景作用

本分析对比了三江并流带黎明、罗古箐、石宝山三个丹霞地貌发育地区的景观特征,从地质学与岩石学的角度分析典型丹霞地貌景观的成景地质条件,探讨景观的地质成景作用,总结景观的成景过程。研究认为,三江并流带丹霞地貌具有自身独特的特征,岩性和构造差异是不同丹霞地貌景观差异形成的根本原因;峰林景观差异因岩层厚度、节理发育程度、交错层理不同而不同;丹霞峰林或赤壁上的“变色瀑布”是裂面或层面之间岩层水渗出沿壁下淌的结果;龟裂纹景观形成严格受岩性和节理构造控制,其发育经过了成景初期、成景中期、成景晚期三个阶段。     

Analysis on the Regional Features of Coda Attenuation Before and After the 1992 Qina (M_S= 5.4, 5.1) Earthquakes in WYEPSA

Using the theoretical model of coda scattering from local earthquakes, we have studied the features of time-space variations of the attenuation rate β of coda amplitude and coda Qc-1 values before and after the Qina earthquakes (MS5.4 and MS5.1) in Dec. 1992 in West Yunnan Earthquake Prediction Study Area (WYEPSA). The study results show that the attenuation rate of coda amplitude has remarkable regional inhomogeneity in the near-field (△ <50 km) around the main shock: β = 0.0076 s-1 and Qc-1 = 0.0056 during the main shock while (3 = 0.0209 s-1 and Qc-1 = 0.0153 during the aftershock. The Qc-1 value shows an approximate 3-foid variation before and after the main shock. We have also obtained the regional averages of β = 0.0235 s-1 and Qc-1 = 0.0153, which show that the coda attenuation in surrounding areas (△ > 50 km) far away from the epicenter of the main shock did not change much before and after the main shock. The evolution of Qc-1 values of the main seismic sequence with time has passed throug