中国北西部地区地浸砂岩型铀矿床的成矿条件与分布规律

中亚地区发现大量可地浸砂岩型铀矿床引起了我国的重视 ,目前正在积极开展此类型铀矿的找矿工作。我国北西部是寻找类似中亚地区层间氧化带后生地浸砂岩型铀矿床最理想的地区 ,本文在论述了区域大地构造特征、地壳演化与区域铀成矿带形成的基础上 ,着重阐明了区域中新生代盆地地浸砂岩型铀矿床形成的铀源条件、盆地类型与结构及富铀性对形成地浸砂岩型铀矿的影响 ;并以区内已有层间氧化带地浸砂岩型铀矿床为例 (伊犁盆地、二连盆地与测老庙盆地砂岩型铀矿床 ) ,论述了盆地砂岩型铀矿床形成的岩相古地理条件、水文地质与层间氧化带发育条件及对铀成矿的影响 ;并阐述了本区层间氧化带地浸砂岩型铀矿床的分布规律     

地震CT及其地质解释

在金川公司龙首矿东采区1 280中段井下500m深的巷道中应用地震CT技术进行寻找深部隐伏矿体的实验。波速图像表明,研究区内中西部有一高速异常区,推断为花岗岩体和含矿的超基性侵入岩体。区内还有一个横贯测区中央近东西走向的低速断裂带。这些推断结果为后期的钻探和巷道开掘所证明。     

Upper Mississippi embayment shallow seismic velocities measured in situ

Vertical seismic compressional- and shear-wave (P-and S-wave) profiles were collected from three shallow boreholes in sediment of the upper Mississippi embayment. The site of the 60-m hole at Shelby Forest, Tennessee, is on bluffs forming the eastern edge of the Mississippi alluvial plain. The bluffs are composed of Pleistocene loess, Pliocene-Pleistocene alluvial clay and sand deposits, and Tertiary deltaic-marine sediment. The 36-m hole at Marked Tree, Arkansas, and the 27-m hole at Risco, Missouri, are in Holocene Mississippi river floodplain sand, silt, and gravel deposits. At each site, impulsive P- and S-waves were generated by man-made sources at the surface while a three-component geophone was locked downhole at 0.91-m intervals.

Consistent with their very similar geology, the two floodplain locations have nearly identical S-wave velocity (V_S) profiles. The lowest V_S values are about 130 m s⁻¹, and the highest values are about 300 m s⁻¹ at these sites. The shear-wave velocity profile at Shelby Forest is very similar within the Pleistocene loess (12 m thick); in deeper, older material, V_S exceeds 400 m s⁻¹.

At Marked Tree, and at Risco, the compressional-wave velocity (V_P) values above the water table are as low as about 230 m s⁻¹, and rise to about 1.9 km s⁻¹ below the water table. At Shelby Forest, V_P values in the unsaturated loess are as low as 302 m s⁻¹. V_P values below the water table are about 1.8 km s⁻¹. For the two floodplain sites, the V_P/V_S ratio increases rapidly across the water table depth. For the Shelby Forest site, the largest increase in the V_P/V_S ratio occurs at 20-m depth, the boundary between the Pliocene-Pleistocene clay and sand deposits and the Eocene shallow-marine clay and silt deposits.

Until recently, seismic velocity data for the embayment basin came from eartquake studies, crustal-scale seismic refraction and reflection profiles, sonic logs, and from analysis of dispersed earthquake surface waves. Since 1991, seismic data for shallow sediment obtained from reflection, refraction, crosshole and downhole techniques have been obtained for sites at the northern end of the embayment basin. The present borehole data, however, are measured from sites representative of large areas in the Mississippi embayment. Therefore, they fill a gap in information needed for modeling the response of the embayment to destructive seismic shaking.     

华北地台主要花岗岩-绿岩带含金丰度值的研究

近十余年来，在华北地台太古宙花岗岩－绿岩带金矿的研究中，获取了许多有关地层、岩石金丰度值的资料。早期获取的资料因化验分析方法灵敏度不高且样品中常常包含矿化、蚀变和构造破碎的岩石等原因而使其金丰度值偏高。最新的数据采用了高灵敏度化验分析方法且剔除了矿化、蚀变和破碎的岩石样品，计算出的金丰度值均明显低于或接近于地壳金丰度值。结合其它研究成果，提出绿岩带有关金矿矿源是多源的（变质的、岩浆的），甚至是深源的（下地壳或上地幔）认识。     

Electric Field Effects on Animals:Mechanism of Seismic Anomalous Animal Behaviors (SAABs)

Electric field effect on animals has been studied to investigate its relation with seismic anomalous animal behaviors(SAABs)in China.Freshwater eel,crucian carp,catfish,and soft-shelled turtle responded to the threshold electric field of 1-10 V/m,while duck,goose,cat,sheep,pig,dog,and chicken all responded to the ground electric field of about tens of V/m,depending on the species as well as on individuals.Most of the behaviors caused by electric field were similar to those reported as SAABs such as alignment,sudden movement,panic,and convulsion.The intensity of electric field due to a major earthquake would have been over these threshold values.Numerical estimation based on an electromagnetic model of a fault has been made to induce SAABs as electric shocks to pulsed electric fields in electro-physiology.The seismic electric signals(SES)intensity might be estimated from the observation of SAABs.     

水库诱发地震的地震动特征

利用新丰江、美国奥洛维尔和蒙蒂赛洛水库地震极近场地面运动资料，研究了水库诱发地震的地震动峰值加速度衰减。结果表明，水库地震的峰值加速度高，衰减快。利用国内水库地震资料研究了水库地震烈度。水库地震烈度与同级天然地震烈度相比，一般是烈度高，衰减慢。水库地震的地震动反应谱频率高，地震动持续时间短     

甘肃省东南部未来地震危险区的模式识别

在综合分析甘肃省东南部地震地质特征的基础上，利用模式识别方法判定未来地震危险区的可能位置．结果表明，本区易发生地震的地点与全新世断裂强烈活动段相吻合，从而提高了对未来地震危险区判定的可信度     

三维分块倾斜界面的反演及其应用

介绍了利用反射波走时反演介质层速度和包含直立断层的三维界面的计算方法．对各层界面利用多个倾斜或平界面方程来描述．给出了数值计算实例．结果表明，反演解与真模型很接近，说明计算方法是有效的．利用该方法处理了唐山地震区的ＰｍＰ反射波资料，获得了该区域莫霍界面的三维分块形态．唐山附近莫霍界面错断与该区域１９７６年唐山地震及一系列余震的发生有密切的联系．     

1995年度中国大陆及边邻MS≥7.0地震活动与华北地区的试验预报纪实之三

如实记述了１９９５年度中国大陆及边邻ＭＳ≥７．０地震活动的时、空演变与华北（φＮ３０°～φＮ４２°，λＥ１０５°～λＥ１２５°）地震活动等有关的试验预报的实况。对过去的预报办法提出了一些改进意见。     

秦岭造山带南北向构造及有关问题的讨论

秦岭造山带具有复杂和长期演化的历史，本文对秦岭造山带的主造山期，结构特征（包括构造单元划分），构造体制和发展演化等进行了综合和讨论。