两种围栏养殖模式防白斑综合征病毒(WSSV)效果的比较

2003年在乳山养殖场采用两种围栏养殖模式养殖了凡纳滨对虾,并对其防白斑综合征病毒(WSSV)效果进行了比较。结果表明,凡纳滨对虾在养殖过程中WSSV阳性率有下降趋势,浮游动物WSSV阳性率较低,布围隔的防病毒效果好于网围隔。     

Human‐induced hazardous debris flows in Carrara marble basins (Tuscany,Italy)

In Carrara marble basins, the long and intensive quarrying activities (which began in the first century BC ) have produced extensive dump deposits, locally known as ravaneti. Ravaneti are of such large dimensions and diffusion as to make them a widespread landform of the Apuane Alps (Tuscany). In recent years these quarry dump deposits have been affected by frequent debris flows, more than 50 in 1996/97. This phenomenon is the most significant currently active geomorphological process in this landscape. The evolution of quarrying techniques produced a variety of sedimentological compositions of ravaneti. The debris flows analysed involve only the surface layers where debris is mixed with fine material with a lower permeability (active ravaneti) than the coarser underlying debris (older ravaneti). The presence of different permeability layers causes a wetting front to move downwards. Source area observations indicate a soil slip movement in the initial phases of the failure. The transformation of landslides into debris flow occurs by means of both soil contractive failure and an increase of granular temperature. The morphological and sedimentological analyses of depositional lobes resulted in a classification of three types of lobe, based on fabric–morphometry relationships allowing the identification of different flow dynamics: (1) type A lobe (platy form), matrix‐supported and well developed fabric with general tendency of ab clast plane strikes to lie generally parallel to flow direction as a consequence of laminar flow; (2) type B lobe (elongated form), clast‐supported and random fabric as a consequence of both turbulent flow and coarser composition of starting material; (3) type C lobe, intermediate type A–B morphometry, tendency for ab clast plane to lie in a semi‐circle around the main flow direction determined by the presence of secondary flow lines divergent from it in the stopping phase. In Carrara marble basins, the anomalous frequency with which debris flows tend to be triggered by medium‐intensity rainstorms (about 30 mm h⁻¹ rainfall) is due to the recent increases in silt dump produced by modern quarrying techniques. This represents a significant example of debris flows as an environmental problem in major anthromorphized landscapes. Copyright © 2000 John Wiley & Sons, Ltd.     

Crustal structure of the deepwater west Niger Delta passive margin from the interpretation of seismic reflection data

The interpretation of 2D and 3D seismic reflection data complemented with gravity data allows the crustal architecture of the deepwater west Niger Delta passive margin to be defined. The data show that the area is underlain by oceanic crust that is characterised by a thickness of 5–7 km and by internal reflectivity consisting of both dipping and sub-horizontal reflectors. Some of the dipping reflections can be traced up to the top of the basement where they offset it across a series of minor to major thrust faults. Other internal reflections are attributed to extensional shear zones and possibly due to intrusions in the lower crust. The Moho can be correlated as a discrete reflection over >70% of the study area. It is generally smooth, but localised relief of up to 1 km is observed. The southeastern part of the study area is dominated by a zone of SW–NE striking basement thrusts.     

组构对自然休止角影响的试验研究

利用自制的模型试验装置,通过在不同方位沉积散体颗粒生成堆积体,研究不同沉积组构特征对自然休止角的影响,以及通过在母堆积体底部设置漏孔以生成子堆积体,研究堆积体内部结构对自然休止角的影响。研究发现,母堆积体休止角? 和子堆积体休止角? 随着沉积面倾角? 的增大（0° → 90°）呈现先减小后增大的趋势,子堆积体休止角? 则先增大后减小,且最小和最大值的分布区间正好互余,分别为? = 30°～45°和? = 45°～60°。当漏孔位置从左至右靠近母堆坡脚时,? 先增大后减小,? 则单调增大。基于模型的分析和推导,发现当沉积面与潜在滑动面越接近平行,休止角越小,越偏离,休止角则越大,并从细观上合理解释了?、? 和? 在特殊角度区间出现最大或最小值的原因。最后,提出了散粒堆积体的扰动分区模型,并以此为基础阐释了漏孔位置（堆积体内部结构）对休止角? 和? 的影响机制。     

桂东北地区鹰扬关韧性剪切带的厘定及其构造意义

论文通过宏-微观构造、磁组构、热液锆石和石英EBSD组构等,厘定鹰扬关韧性剪切带并讨论其构造意义。鹰扬关韧性剪切带具有宏-微观韧性变形组构,发育糜棱岩、拉伸线理、S-C组构、旋转碎斑系、书斜构造、压力影和石英的动态重结晶等。磁组构和宏-微观构造表明,鹰扬关韧性剪切带呈NNE向延伸超过40 km,宽2.5～8 km。糜棱C面理的极密点产状127°∠50°;磁面理的极密点产状107°∠83°。宏-微观构造研究表明,鹰扬关韧性剪切带具有早期左旋逆冲剪切,晚期右旋正滑剪切的运动学性质。石英EBSD组构表明,鹰扬关韧性剪切带具有晚期中低温变形(400～550℃)叠加于早期中高温变形(550～650℃)的特征。年代学研究表明,鹰扬关韧性剪切带早期左旋逆冲剪切的时代为(441.1±2.3)Ma,晚期右旋正滑剪切的时代应晚于420 Ma,区域构造应力由挤压转为伸展的时限为420 Ma。在磁组构、石英EBSD组构和热液锆石定年的基础上,结合区域地质资料,认为鹰扬关韧性剪切带形成于华夏陆块自SE向扬子陆块造山挤压的构造背景。早期造山挤压,产生压扁型应变和中高温左旋逆冲剪切;晚期造山后伸展,产生拉伸型应变和...     

桂北四堡韧性剪切带的发现及其构造意义

通过野外观察、室内显微构造分析和磁组构测量方法,在桂北四堡地区浅变质地层中厘定出一条NE30°走向,南东倾,倾角约40°的大型左旋斜冲韧性剪切带——四堡韧性剪切带;该韧性剪切带内发育糜棱岩系列、糜棱面理、拉伸线理、A型褶皱、S-C组构、亚颗粒、显微分层及石英条带等宏观和微观构造特征;磁各向异性度测量结果显示四堡韧性剪切带由一宽约4 km的强应变带及边缘弱带组成,全带宽达10 km,长度超30 km;在对韧性剪切带运动学、构造年代学研究的基础上,结合区域地质资料,认为四堡韧性剪切带是华南加里东晚期华夏地块由南东向北西作低角度斜冲到扬子地块的产物。这一发现揭示了扬子地块与华夏地块碰撞拼合的方式,为深化华南构造演化提供了新资料。     

云南省南涧地区下白垩统南新组砾岩层 砾组特征及其物源意义

该文通过对哀牢山构造带西侧云南省南涧地区下白垩统南新组砾岩层的砾性、砾度、砾态和砾向等的详细研究与分 析,结合盆地基岩地层特点和周边构造带的岩性组合特征,发现南新组砾岩总体上具有砾石成分复杂、分选性较差、磨圆程 度中等-较好（次圆状-圆状）、风化程度较低等特征;探讨了砾岩层本身的性质、物质来源,以及砾石沉积时盆地的水动力条 件、气候环境、古地貌特征和构造条件。认为南新组砾岩层为半干旱-干旱古气候条件下的一套冲积扇-辫状河相粗碎屑沉 积,具有快速堆积的特点;砾岩层沉积前砾石遭受了较强的物理化学作用。根据盆地基岩及周边地层岩性特点和砾石扁平面 倾向统计,砾石的主要来源是盆地内部的基底地层及其东缘的哀牢山构造带。     

大洋板块俯冲带地震波各向异性及剪切波分裂的成因机制

大洋板块俯冲带是许多重要地质作用(例如脱水、部分熔融、岩浆和地震活动)发生的场所.对位于俯冲带之上的地震台站所检测到的不同剪切波的数据解析,可以获得源于上覆板块、地幔楔、俯冲板块和板下地幔的地震波各向异性的关键信息.本文系统总结了世界各地大洋俯冲带的剪切波分裂样式,对目前国际上流行的大洋俯冲带的地震波各向异性的主要成因...     

Deformation Structures of the Madao Gneiss in South Qinling: Structural Analysis, Geochronological Constraints, and Tectonic Implications

The tectonic evolution of South Qinling,which is a main part of the Qinling orogenic belt,is still in dispute and deformation history of South Qinling is poorly studied.In this paper,detailed structural,microstructural,quartz c-axis fabric analysis,and geochronology results for the Madao gneiss in South Qinling are presented to characterize the deformation history.Results show that rocks in the northern part(Tiefodian-Laozhanggou) experience general shearing and deform at relative low temperature.The shear sense generally is south to north.In contrast,rocks in the southern part(Laozhanggou-Panjiahe) are weakly sheared with pure shear features and evidence of hightemperature deformation.Based on the analyses,we conclude that there exist two distinct deformation geometries in the Madao gneiss and accordingly we can divide the deformation into two stages.The early stage is represented by regional shortening,while the late stage features northward thrust shearing and evidence shows that it was a progressive process between them.LA-ICP MS U-Pb dating of zircons from pre-deformational migmatite veins yields age of 198.5 ± 2.0 Ma.This result,in combination with the age of post-deformational granite,indicates that the northward thrust shearing of the Madao gneiss occurred in the Late Triassic.In view of these results and other reported data in South Qinling,we propose that deformation in Madao gneiss may result from the initial collision and subsequent northward accretion in Late Triassic.     

青藏高原东缘鲜水河断裂带磁组构特征及构造意义

为了探究鲜水河断裂带的几何学、运动学特征,在野外构造、显微构造分析基础上,研究了鲜水河断裂带296块构造岩定向样品的磁组构特征和热磁特征,结果显示样品的平均磁化率km值总体较小,属微弱磁性到弱磁性;热磁实验及其显微构造表明顺磁性的页硅酸盐(如黑云母)等矿物对糜棱岩类样品磁化率贡献较大;磁化率各向异性度PJ总体较大,表明鲜水河断裂带构造变形强烈;磁化率椭球体形状参数T总体大于0,扁率E总体在1附近分布,说明鲜水河断裂带磁化率椭球体以扁圆形为主,整体上磁面理较磁线理发育,进一步显示出鲜水河断裂带构造变形样式以剪切、压扁为主,伴有拉伸的构造变形,同时也反映出鲜水河断裂带多次变形的综合特征;最小磁化率主轴Kmin方位表明鲜水河断裂带北段和南段分别受近EW向和NE-SW向主压应力控制;同时Kmin方位及其倾伏角特征显示鲜水河断裂带总体以左行走滑剪切为主,北段两侧块体在鲜水河断裂带两次不同的构造活动时期,各自有一定的相对抬升,但抬升幅度均不大;南段则是SW块体相对NE块体抬升,抬升幅度较大;整个断裂带特征显示出鲜水河断裂带在向南发展逐渐转化为挤压构造,这可能与青藏高原物质的向东逃逸受阻以及鲜水河断裂带与龙门山断裂带在此交接的地质背景不无关系.