内蒙古白乃庙地区外接触变质带内──阳起石～钙质斜长石带     

吴玉琨  吴琼 《内蒙古地质》1997,(2)

白乃庙地区绿色片岩主要为阳起石＋钙质斜长石组合，形成不同矿物组合和亚带。白乃庙地区花岗质侵入岩体侵入到岛弧蛇绿岩中形成外接触变质带内—阳起石～钙质斜长石带。该带的确立为建立阳起石～钙质斜长石角门岩相及分布其中的接触变质型铜钼矿床提供依据。  相似文献   

西昆仑库地蛇绿岩的地质特征及其形成环境     

王元龙  李向东  毕华  王中刚  朱笑青  黄智龙 《吉林大学学报(地球科学版)》1997,(3)

根据新藏公路沿线实际观察资料和前人的最新成果，总结了新疆西昆仑库地蛇绿岩的构造特征、层序及岩石学特征；对库地蛇绿岩形成时代、原始构造环境等有争议的关键性问题进行了分析和探讨，得出了有关库地蛇绿岩的如下新结论：①形成时代为中元古代—晚元古代，同位素年龄值为大于１６６１．９～６９８．３６Ｍａ；②形成于缓慢扩张的条件下，且没有经历过俯冲消减作用；③岩浆来源为弱亏损的、非单一的上地幔源，并受到了陆壳物质的混染；④原始构造环境为弧后盆地—岛弧—弧间盆地，属过渡性构造环境  相似文献   

Surface-wave propagation across the Mexican Volcanic Belt and the origin of the long-period seismic-wave amplification in the Valley of Mexico   总被引：1，自引：0，他引：1  

N. M. Shapiro  M. Campillo  A. Paul  S. K. Singh  D. Jongmans  F. J. Sánchez-Sesma 《Geophysical Journal International》1997,128(1):151-166

A network of nine broad-band seismographs was operated from March to May 1994 to study the propagation of seismic waves across the Mexican Volcanic Belt (MVB) in the region of the Valley of Mexico. Analysis of the data from the network reveals an amplification of seismic waves in a wide period band al the stations situated in the southern part of the MVB.
The group velocities of the fundamental mode of the Rayleigh wave in the period range 2–13 s are found to be lower in the southern part of the MVB than in its northern part and in the region south of the MVB. The inversion of dispersion curves shows that the difference in group velocities is due to the presence of a superficial low-velocity layer (with an average S -wave velocity of 1.7 km s^-1 and an average thickness of 2 km) beneath the southern part of the MVB. This low-velocity zone is associated with the region of active volcanism.
Numerical simulations show that this superficial low-velocity layer causes a regional amplification of 8–10 s period signals, which is of the same order as the amplification measured from the data. This layer also increases the signal duration significantly because of the dispersion of the surface waves. These results confirm the hypothesis of Singh et al. (1995), who suggested that the regional amplification observed in the Valley of Mexico is due to the anomalously low shear-wave velocity of the shallow volcanic rocks in the southern MVB  相似文献   

Geomorphic studies of landslides in the Tully Valley, New York: implications for public policy and planning     

Donald L. Pair  William M. Kappel   《Geomorphology》2002,47(2-4)

On April 27, 1993, a large landslide in the Tully Valley, Onondaga County, NY, destroyed three houses and resulted in the evacuation of four others; it also triggered a loss of potable drinking water for about 15 homes north of the slide area and affected a total of 20 ha of land. In the 7 years following this slide, several studies have been conducted by federal and state environmental agencies and by local universities. The goal of these investigations has been to determine what caused this slide, document the history of past landslides in the region, and establish whether future slides are likely to occur. This paper reports on the results of these investigations and examines their effect on the Tully Valley community.  相似文献   

Le métamorphisme Tardi-Crétacé à Éocène des zones internes de la chaı̂ne Indo-Birmane (Myanmar occidental) : implications géodynamiquesLate Cretaceous to Eocene metamorphism of the internal zone of the Indo-Burma range (western Myanmar): geodynamic implications     

Anne Socquet  Bruno Goffé  Manuel Pubellier  Claude Rangin 《Comptes Rendus Geoscience》2002,334(8):573-580

Metamorphic study on Triassic schists in the internal zone of the Indo-Burma range, essentially based on chlorite–mica equilibrium in metapelites, allows a P–T path to be quantified. During the prograde metamorphism, the geothermic gradient evolves from that of a ‘normal’ crust (30 °C km^?1) to that of a thickened crust (18 °C km^?1). The peak conditions are around 8 kbar and 450 °C. This thickening (25–30 km) is probably made in a wedge set up between the Late Cretaceous and the Eocene, in front of the obduction. The obtained cold retrograde path requires a mechanism allowing thermal re-equilibration, implying slow exhumation. It occurred along a shear zone that put into contact the micaschists of the core with the Triassic schists of the roof. To cite this article: A. Socquet et al., C. R. Geoscience 334 (2002) 573–580.  相似文献   

里下河地区汛期（6—7）旱涝特征分析   总被引：1，自引：0，他引：1  

秦铭荣  刘方 《气象科学》1996,16(3):285-290

本文应用气象、水文资料，结合里下河地区历年灾情实况，分析了具有特殊地形的里下河地区旱涝规律和成因，得出了综合旱涝指标，最后对比分析了大涝年１９５４年、特大涝年１９９１年大旱年１９７８年，１９９４年的气象、水文特征，为防灾减灾提供了科学依据。  相似文献   

甘孜－理塘结合带甘孜地区混杂岩类型及成因分析   总被引：1，自引：0，他引：1  

江元生 《四川地质学报》1996,(3)

对甘孜－理塘结合带甘孜地区的沉积混杂、火山混杂、构造混杂岩作了系统分析研究。重点论述了甘孜地区三条构造混杂岩带的物质组成、变形特征和形成机制。结合带是由大小不等，形态各异的岩块（片）拼贴、堆叠而成的构造混杂岩带。较合理地解释了结合带内，大洋拉斑玄武岩、洋岛玄武岩、大陆碱性玄武岩共存的地质特征。提出了一种新的构造岩石单位——构造混杂岩。并对甘孜地区蛇绿岩的成因作了探讨。  相似文献   

雅鲁藏布江开合带蛇绿岩地层   总被引：11，自引：0，他引：11  

朱占祥  滕云 《地层学杂志》1996,20(4):299-304

对西藏地层清理发现，沿雅鲁藏布江构造带分布的蛇绿岩，为具有类同正常沉积和沉积火山岩一样的有层、有序、有沉积构造及时代新老关系的蛇绿岩地层，它是特提斯洋开裂形成期的产物，赋予地层学的涵义，命名为雅鲁藏布江蛇绿岩群，从下至上建立变质橄榄岩组、堆积杂岩组、辉绿岩床（墙）组、枕状熔岩组及放射虫硅质岩、浊积岩组。它们构成完整的五套结构地层组合，生成时代为侏罗纪－白垩纪。新近区调成果表明，沿雅鲁藏布江构造带尚有中三叠世－晚三叠世时期蛇绿岩地层存在的可能性。雅鲁藏布江侏罗纪－白垩纪地层区划，其北与冈底斯－念青唐古拉地层区的界线，应划在日喀则群北界；其南应是雅鲁藏布江蛇绿岩群以南为界，南界同时是板块碰撞闭合边界或构造区划边界。  相似文献   

长江产业带能源资源合理开发与能源供需解决途径^*     

刘毅 《地理研究》1996,15(2):12-20

本文从长江产业带持续发展建设的要求出发,针对能源生产、消费和供需平衡存在的主要矛盾与问题,提出并论证了产业带未来能源资源的合理开发方向及规模、缓解能源运输矛盾的途径和上中下游能源开发方向与重点。  相似文献   

中国西天山不同海拔雪岭云杉树轮宽度年表特征及其气候响应特征     

李淑娟  喻树龙 《沙漠与绿洲气象(新疆气象)》2017,11(1):50-57

利用西天山伊犁河谷新源林场卡勒克玛林区5个采样点(KL1～KL5)的雪岭云杉树轮样芯,建立宽度年表,并分析树木年轮标准化年表与气候的相关性,以及这种相关性随海拔梯度的变化情况。结果表明：(1)样本对总体的代表性都很好,KL3的各项指标在5个标准化年表中最高,包含的气候信息最多、受到气候的影响最明显;(2)除KL5与新源站当年4月的降水正相关不显著外,其余标准化年表均与新源上年及当年4月降水显著正相关,且较高海拔的KL1～KL3与当年4月降水的相关性较上年4月更密切,较低海拔的KL4～KL5则相反;(3)各标准化年表与新源站上年4月～上年10月以及当年9月的平均温度和平均最高温度为负相关,而与上年12月的温度要素均为正相关;（4）各采样点树木径向生长受气候的“滞后性”影响明显,林缘上部的采样点（KL1、KL2）树木径向生长受到温度的制约作用较降水更明显,林缘中下部（KL3～KL5）则相反。  相似文献