螺旋CT机滑环结构探讨与维修

本文主要根据CT基本原理和结构,重点说明螺旋CT机滑环类型、结构及工作原理,介绍经过实际使用的螺旋CT机滑环性能与应用效果,说明优点和不足之处,在CT滑环维修方面,从实际工作出发,说明维修方法、步骤及注意事项,为今后设计、生产、使用和维修提供有用的帮助。     

郯城-庐江断裂基本特征及其控盆作用

郯城-庐江断裂是中国东部一条规模巨大的断裂构造带, 贯穿中国东部大陆, 向南延伸入南海, 向北抵达俄罗斯境内。郯城-庐江断裂成生于早白垩世晚期, 是一条巨型压扭性断裂带。研究认为, 郯城-庐江断裂不存在巨大平移, 它形成于早白垩世晚期, 并控制K₂-E断陷盆地带及其相伴的断隆带的发生、发展; 郯城-庐江断裂是一条活动性断裂构造带, 研究它的基本特征及其控盆作用, 有助于认识中国东部乃至东亚地区晚中生代以来的大地构造属性。      

汶川地震对现代河流形态的影响与水文效应

2008年5月12日14时28分,我国四川发生里氏8.0级大地震,发震构造为龙门山断裂带.形成了NE向映秀-北川断裂地表破裂带,彭县-灌县断裂破裂带以及NW向的小鱼洞破裂带,表现为逆冲-走滑性质.目前,有关地表破裂、次生地质灾害及堰塞湖等开展了大量的调查工作,而地震对河流形态的影响还缺少较为系统的分析.在野外地震地貌考察的基础上,根据河流走向与断层位置关系,并结合地表破裂特征,总结了汶川地震对现代河流形态影响的几种地貌类型:顺向陡坎跌水,河道错动,断寨湖(塘),河流改道等,并对其演化趋势进行了讨论.分析了汶川地震的河流水文效应:地震增加了河流泥沙含量,改变了河流水质,同时,也使得河流与地下水系统之间的联系更为紧密.     

坚硬“打滑”地层孕镶金刚石钻头设计与选用

坚硬“打滑”地层钻进一直是钻进工作的一项难题,深入分析了钻进碎岩机理,确定影响钻进速度的因素,进而提出钻头设计应考虑的因素,并通过野外试验验证了所提观点。     

Tancheng－Lujiang Fault System： Its Characters and Control on Oil－Gas Distribution in Eastern China

Ｔａｎｃｈｅｎｇ－ＬｕｊｉａｎｇＦａｕｌｔＳｙｓｔｅｍ：ＩｔｓＣｈａｒａｃｔｅｒｓａｎｄＣｏｎｔｒｏｌｏｎＯｉｌ－ＧａｓＤｉｓｔｒｉｂｕｔｉｏｎｉｎＥａｓｔｅｒｎＣｈｉｎａＣｈｅｎＱｕａｎｍａｏ；ＬｉａｎｇＸｉａｏｄｏｎｇ；ＺｈａｎｇＧｕａｎｇｙａ；...     

下平板滑移对后台阶流的影响

采用混合有限分析解法对后台阶流在下平板滑移作用下的流动状况进行了数值模拟,并在与典型后台阶流进行比较的基础上分析了下平板滑移对流动结构所产生的影响。计算结果表明,这种情况下的后台阶流动涡漩结构更为复杂,流动区域内生成三个漩涡,两个小漩涡位于下部漩涡区,其长度主要随着下平板滑移速度的增大而减小;一个大漩涡位于上部漩涡区,其长度随着下平板滑移速度和雷诺数的增大而增大,但雷诺数的影响更为显著。     

Early Cretaceous sinistral shearing and associated folding in the South Kitakami Belt, northeast Japan

Abstract   Early Cretaceous structural development of the southern part of the South Kitakami Belt, northeast Japan, is discussed through precise structural mapping and the measurement of semiquantitative strain. The mapping and measurement revealed that wide north- to northeast-trending sinistral shear zones occupied by the 'slate' with higher strain than the surrounding rocks run from the axial part to the western limb of major synclines, with the wavelength of 5–10 km. The major synclines with a U-shaped rock distribution opening to the south are interpreted to be drag folds along the sinistral shear zones. These structures were modified by a second stage of Early Cretaceous sinistral shearing characterized by localized high-temperature mylonite zones along the rim of some of the 120 Ma granitoids that cut the major folds and baked the 'slate' in the older shear zones mentioned above. The rocks of the South Kitakami Belt, which had undergone two stages of shearing, were rapidly exhumed before the deposition of the Late Aptian–Albian Miyako Group. Finally, a restoration model is presented of the Early Cretaceous sinistral displacement and deformation in the study area.     

Arcs and backarc basins in the Early Paleozoic lapetus Ocean

Abstract Understanding the evolution and destruction of past oceans not only leads to a better understanding of earth history, but permits comparison with extant ocean basins and tectonic processes. This paper reviews the history of the Early Paleozoic circum-Atlantic oceans by analogy with the Pacific Ocean and Mesozoic Tethys. Rifting and continental separation from 620 to 570 Ma led to the development of passive margins along parts of the northern margin of Gondwana (the western coast of South America); eastern Laurentia (eastern North America, NW Scotland and East Greenland), and western Baltica (western Scandinavia). Meagre paleomagnetic data suggest that western South America and eastern North America could have been joined together to form facing margins after breakup. Although western Baltica is an apparently obvious candidate for the margin facing NW Scotland and East Greenland, the paleomagnetic uncertainties are so large that other fragments could have been positioned there instead. The Iapetus Ocean off northeastern Gondwana was probably a relatively wide Pacific-type ocean with, during the late Precambrian to early Ordovician, the northern margin of Gondwana as a site of continentward-dipping subduction zone(s). The 650-500 Ma arc-related igneous activity here and the associated deformation gave rise to the Cadomian, ‘Grampian’, Penobscotian, and Famantinian igneous and orogenic events. By 490-470 Ma, marginal basins had formed along the eastern Laurentian margin as far as NE Scotland, along parts of the northern margin of Gondwana, and off western Baltica, but none are known from the East Greenland margin. These basins closed and parts were emplaced as ophiolites shortly after their formation by processes that, at least in some cases, closely resemble the emplacement of the late Cretaceous Semail ophiolite of Oman. This orogenic phase seems to have involved collision and attempted subduction of the continental margin of Laurentia, Gondwana and Baltica. In Baltica it gave rise to some eclogite facies metamorphism. Marginal basin development may have been preceded by arc formation as early as ca 510 Ma. A double arc system evolved outboard from the eastern Laurentian and western Baltica margins, analogous to some of the arc systems in the present-day western Pacific. At 480-470 Ma, there was a second phase of breakup of Gondwana, affecting the active Gondwanan margin. Eastern and Western Avalonia, the Carolina Slate Belt, Piedmont, and other North American exotic continental blocks rifted away from Gondwana. Farther east, Armorica, Aquitainia, Iberia and several European exotic continental blocks also rifted away, though it is unlikely that they all rifted at the same time. Between 460-430 Ma, peaking at ca 450 Ma, orogenic events involved continuing arc-continent collision(s). From 435-400 Ma the remaining parts of the Eastern Iapetus Ocean were destroyed and the collision of Baltica with Laurentia caused the 430-400 Ma Scandian orogeny, followed by suturing of these continents during the Siluro-Devonian Acadian orogeny or Late Caledonian orogeny to 380 Ma, leaving a smaller but new ocean south of the fragments that had collided with the Laurentian margin farther south. The Ligerian orogeny 390-370 Ma collision of Gondwana-derived Aquitaine-Cantabrian blocks with Eastern Avalonia-Baltica and removed the part of the Iapetus south of Baltica. Prior to any orogenic events, the Eastern Iapetus Ocean between Baltica and Laurentia may have resembled the present-day central Atlantic Ocean between Africa and North America. The ocean appears to have closed asymmetrically, with arcs forming first outboard of the western margin of Baltica while the East Greenland margin was unaffected. The Western Iapetus Ocean between Laurentia and Gondwana also closed asymmetrically with a dual arc system developing off Laurentia and an arc system forming off the northern margin of Gondwana. Like the Pacific Ocean today, the Eastern Iapetus Ocean had a longer and more complex history than the Western Iapetus Ocean: it was already in existence at 560 Ma, probably developed over at least 400 million years, by mid-Cambrian time was many thousands of kilometres wide at maximum extent, and was associated with a < 30 million year phase of marginal basin formation. In contrast, the Western Iapetus Ocean appears to have been much narrower, shorter lived (probably < 100 million years), and associated with the rifting to form two opposing passive carbonate margins, analogous to the Mesozoic Tethys or the present-day Mediterranean.     

小江断裂带巧家段晚第四纪走滑速率研究

鲜水河-小江左旋走滑断裂系是调节青藏高原东南部物质向东南挤出的大型边界断裂。云南巧家断裂作为小江断裂带北段,其晚第四纪走滑速率是认识川滇地块东部边界应变调节方式的关键。本文利用无人机航摄和地面激光扫描技术,获取了该断裂段穿过金沙江河谷区红路和蒙姑两处的高分辨率地形数据,恢复出断层错动T2和T3两期阶地陡坎上缘的左旋位错量分别为120±5～128±1 m和193±1～202±1 m。根据T3中次生碳酸盐的AMS-¹⁴C法测年结果,结合已有的类似阶地年龄数据,并经气候曲线校正后认为,区域上T2和T3被废弃应分别发生在冰后期和末次盛冰期末期,时间为8.5～11.2 ka BP和18.6～21.4 ka BP。据此估算,小江断裂带巧家段的晚第四纪平均走滑速率为10～13 mm/a。进一步统计分析小江断裂带的晚第四纪走滑速率,发现巧家至宜良以北的段落,总体保持着10～15 mm/a的高走滑速率。但从宜良向南,断裂走滑速率出现了分段递减的特征,至建水以南快速减小到中-北段的近十分之一。小江断裂带中-北段的高走滑速率以及向南的分段式递减现象,反映在宜良以北,小江断裂带的走滑剪切...