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11.
Johann Steiner 《Australian Journal of Earth Sciences》2013,60(1):99-131
Present‐day galactic data permit the construction of a galactic model in which the galactic gravitational field is described by a gravitational function rather than the Newtonian gravitational “constant” G. The concept of this empirical gravitational function, which is based on galactic orbital velocity data, envisages G as a function of time and space. In this model the interaction of this gravitational function, which has rotational symmetry in the galactic plane, and the slightly elliptical galactic orbit of the solar system results in a systematic variation of G. This interaction specifies a simple galactic time‐scale which can be conveniently compared with events of the geological time‐scale. For reasons of galactic evolution and modifying effects due to suspected changes of mass distributions in the universe with the passage of time, which are classed here under the Dirac‐Jordan Effect, such a comparison is initially restricted to the past 1#fr1/4> cosmic years, or 350 million years. The problems in extending such a comparison to 8 cosmic years are discussed, and such an extension seems promising, but it is hampered by the paucity of geological and geophysical data from the lower Palaeozoic and the Precambrian and the present uncertainties in regard to galactic evolution. “Worldwide” statistical maxima and minima of the following geological criteria disclose an episodic correlation with the variation of G and the rates of change of G during the past 350 million years, as specified by this galactic model. It is possible to interpret this correlation in terms of accepted geological principles and concepts in most cases. The following geological phenomena are considered in this comparison of the galactic and geological time‐scales for the past 350 million years.
Period boundaries of the stratigraphic system 相似文献
12.
钦杭成矿带南段的庞西垌-金山银金矿田位于粤东与桂西交界处,包括庞西垌、金山、中苏、竹根坡、高村等银金矿床及一系列银金矿点,是20世纪80年代规划的十大银矿基地之一。庞西垌地区经历了多期的构造-岩浆活动,韧性剪切带和断裂构造尤其发育。印支期以来,可识别出3期主要构造:第一期为右行韧性剪切,前人利用糜棱岩中白云母测得时代为221 Ma;第二期为左行韧脆性剪切,北东向的庞西垌-金山断裂带反映最为突出,切过燕山晚期花岗岩;第三期为脆性走滑。银金矿体及矿石结构、构造主要受第二期左行韧脆性剪切带控制。应用里德尔剪切体系对控矿构造的分布特征分析显示,银金矿脉主要赋存于里德尔体系的D、R和T裂隙中;D裂隙是最重要的赋矿构造,热液蚀变岩型和石英脉型矿体呈透镜状左行斜列于主断裂面中,沿走向往南西侧伏;R和T裂隙主要发育梳状含金石英脉。R裂隙呈密集剪破裂产出,与主断裂面夹角15°~35°;T裂隙呈雁列状等距分布,与主断裂面夹角约为45°。这些矿脉就位体系,可以为该区进一步找矿作参考。 相似文献
13.
里德尔剪切的组合型式与走滑盆地组合型式的相似性 总被引：1，自引：0，他引：1
走滑断裂体系中经常发育里德尔剪切的断裂组合,世界上不同构造背景下与走滑断裂相关的盆地(走滑盆地)也很多见。因此里德尔剪切是地质构造研究中的重要方面。我们从三个方面对里德尔剪切的节理构造组合及盆地组合进行了对比:(1)里德尔剪切构造组合与比例尺无关。里德尔剪切带的(转换)拉张区与沉积盆地的分布区是相似的;(2)断裂的最大位移区与断陷盆地的沉积中心是一致的,断陷盆地长轴平行于断裂走向;(3)物理模拟试验及数学模拟试验都证实了走滑盆地的演化。基于上述认识,我们通过厘米级岩芯标本的观察,结合已发表的盆地资料,提出了6类与里德尔剪切有关的构造组合及断陷盆地组合。(1)雁列状构造及盆地组合:许多盆地发育雁列状构造。同时,与里德尔剪切相关的雁列状盆地的宽度与主剪切断裂的剪切位移呈正相关。(2)帚状或马尾状构造及盆地组合:二者在形态上相似,所以归为一类。成因上,马尾状构造及盆地主要发育在走滑断裂的拉张端部,而帚状构造或盆地反映走滑断裂的旋扭作用,可以在走滑断裂影响区域的任何部位。(3)串珠状构造及盆地组合:该类型的盆地主要是指释压盆地的组合,拉分盆地也可以形成串珠状盆地。(4)S状或Z状构造或盆地组合:左行走滑形成Z状构造或盆地,而右行走划形成S状构造或盆地。(5)多字型构造及盆地组合:是拉分盆地的典型组合,可以过渡到串珠状盆地。(6)复杂的网状构造及盆地组合:通常是由于分布型简单剪切的作用结果。以上盆地组合类型包括大型盆地内次级单元(次级盆地或更次级盆地)的组合,但不包括多成因、多期活动的构造及盆地。 相似文献
14.
Implications of Coulomb plasticity for the velocity dependence of experimental faults 总被引：2，自引：0，他引：2
Simulated fault gouges often deform more stably than initially bare surfaces of the same composition. It is important to understand why the sliding stability is enhanced because the presence of gouge on natural faults may have the same effect as seen in experiments, and thus explain the absence of earthquakes at shallow depths. Gouge stabilization in experiments has been attributed to positive contributions to velocity dependence within gouge layers from either dilation (Marone
et al., 1990) or grain fracture (Biegel
et al., 1989). In this study we test the hypothesis that some aspects of gouge and initially bare surface velocity dependence are identical by measuring the time-dependent constitutive parameterb. An important result follows however from stress analysis: if both sample configurations are frictional in the Mohr-Coulomb sense, each configuration is required to deform on planes of distinctly different orientation. The measured strength and velocity dependence will reflect this geometric difference. Our observed values ofb for simulated granite and quartz gouge are two to two and a half times smaller thanb for initially bare surfaces. This difference is completely accounted for if gouge is represented as a cohesionless-Coulomb plastic material. The analysis demonstrates the following points: 1) gouge deformation is fully consistent with Coulomb plasticity, 2) observed gouge velocity dependence is a function of observed strength and 3) the constitutive parameterb is the same for both bare surfaces and gouge. Furthermore, the results suggest that there is no time-dependent strengthening associated with stabilizing effects in gouge. These observations provide a framework for understanding how slip on initially bare surfaces and gouge deformation are related. 相似文献
15.
Collin Nkono Olivier Fmnias Daniel Demaiffe 《Journal of Volcanology and Geothermal Research》2009,187(1-2):13-25
This study is a part of a wider investigation to evaluate how much can be learnt by using low-cost methods such as systematic moderate-resolution remote sensing to map and quantify geological structures at the regional scale on very large volcanic provinces only partly studied in the field. Volcanic-centre and cinder-cone distribution, faults and structural lineaments are mapped combining Shuttle Radar Topography Mission (SRTM), Digital Elevation Models (DEMs) and Landsat satellite images. As an example of the method, we present the interpretation of structural data and morphological features of three contrasted areas from the Cameroon Volcanic Line (Tombel graben, Upper Benue valley, and Ngaoundéré area) for which local field studies are available for comparison. At a local scale, this remote-sensing method of mapping displays good to excellent correlations with previously published data and, by itself, it allows one to constrain the structural setting of each area. Numerical treatment of vent and cinder-cone localisation can be related to tension fractures (T direction), whereas numerical treatment of the lineaments constrains the associated fault system to a single transtensional (strike-slip + extension) Riedel type fracture network. The first results on the Cameroon Volcanic Line are promising and could be used at a larger scale on numerous volcanic provinces for which field data are not yet available. 相似文献
16.
青海玉树Ms7.1级地震同震地表破裂构造 总被引：1，自引：1，他引：0
分析了青海玉树Ms7.1级地震中形成的同震地表破裂分布与构造特征。本次地震造成的地表破裂长达46km,地震造成240cm的最大相对水平走滑错动量,最大垂直错动量60cm。地表破裂所经之处可看到原有断层新近活动的明显迹线。依次分析了按空间尺度划分的4个层次破裂的走向变化、同级破裂排列、破裂末端变化等构造特征。Ⅰ级破裂作为本次地震产生的整个破裂带,总体走向119°,由3段自然分开、左阶斜列的Ⅱ级破裂组成。3段Ⅱ级破裂自NW向SE依次为隆宝镇段、结古镇段和禅古寺段,破裂性质总体以左旋走滑为主,各段略有不同。各Ⅱ级破裂带内部,分别由若干Ⅲ级破裂段落组成,总体呈现右阶斜列排列模式。Ⅲ级破裂本身由一系列简单的Ⅳ级破裂雁列或羽列右阶斜列构成。不同层次的地表破裂具有简单剪切构造带的变形特征,共识别出R、R’、Y、T和P五组基本破裂面。其初始破裂面展布特征可以用库伦破裂准则来解释,其中岩土体材料的内摩擦角大致为26~44°。各级破裂端部出现分叉、转向及逐渐消失等变形特征。 相似文献
17.
模拟断层泥的摩擦实验对地震的成核及断层带变形组构的研究具有重要意义。文中对辉长岩摩擦实验中的断层泥变形组构及形成机理进行了研究 ,以期从实验室角度来理解地壳深部断层活动的性质和特点。断层泥剪切组构中的边界剪切带 ,R1,Y剪切面比较发育 ,T裂隙次之 ;R2 ,P ,X剪切面不发育。R1面与边界面的夹角较小 ,平均在 1 1°左右 ,为单剪变形过程中达到破裂极限状态时形成的 1组库仑破裂面。分析表明R1面密度随正应力的增加而明显增高。而在相同的正应力下 ,随温度的增高 ,R1面的密度也有增加的趋势。当温度高于 5 0 0℃时 ,断层带内的斜长石出现塑性变形特征 ,R1剪切面与矿物的压性面理组成典型的S -C组构 相似文献
18.
马来西亚沙捞越Punda走滑构造及其动力学成因 总被引：1，自引：2，他引：1
沙捞越Punda走滑构造为一典型的右旋走滑构造形式，是沿近东西向F断裂(PDZ)发育特征的负花状构造或郁金香构造，并构成走滑伸展双重构造。Luconia陆块与巽他克拉通的碰撞及卢帕断裂的走滑是Punda走滑构造形成的动力学成因。同时，利用Riedel单剪模式和走滑次级构造逐级配套模式可以合理地解释Punda走滑断裂的构造形式。 相似文献
19.
喀拉玉尔滚构造带包括喀拉玉尔滚走滑断裂、北喀背斜、中喀背斜、南喀背斜及其次生构造。其中,北喀背斜、中喀背斜为塔北地区重要的背斜圈闭,同时也是塔里木油田的重点勘探对象。利用15m空间分辨率的ETM＋影像（多光谱和全色波段融合）及0．61m空间分辨率的QuickBird影像构成的多空间分辨率遥感影像集,结合少量野外地质资料,成功地提取了北喀、中喀背斜上的25条次生小断裂,其后又运用里德尔单剪理论对新发现的小断裂性质进行了解释,最后利用ETM＋影像确定了喀拉玉尔滚右旋走滑断裂的走向和位置,提出了对喀拉玉尔滚构造带的4点认识。 相似文献