A preliminary study on mineralogical and chemical compositions of some chondrites falling in China     

Daode Wang  Ziyuan Ouyang  Wei Hou 《中国地球化学学报》1982,1(2):186-199

Samples are available from 37 stony meteorites falling in China. Twenty-two chondrites are examined in terms of chemical and mineral compositions, cosmogenic nuclides, formation and exposure ages, impact effect and chondrule textures. On the basis of chemical-petrologic features these chondrites are classified asE ₄ (Qingzhen),H ₅ (Jilin, Changde, Shuangyang, Anlong, Xinyi and Yangjang),L ₆ (Renqiu, Junan, Heze, Rugao and Nei Monggol) andLL ₆ (Dongtai). E ₄ is characterized by high iron and sulfur, with the former occurring mainly as Fe^o and FeS. FromH ₅ throughH ₆ toLL ₆, iron and nickel decrease gradually while FeO and the ratio of Fe silicate to total iron increase gradually. indicating a general increase in the orderE-H-L-LL in the degree of oxidation at the time of formation. E ₄ consists mainly of enstatite and, to much less extent, free SiO₂ but olivine is hardly to be found. The olivine proportions amount to 29.07, 41.98 and 51.36 percent inH ₅,L ₆ andLL ₆ respectively, with Fa increasing from 17 to 27 percent. Recrystallization has been noticed to different degrees inH ₄,H ₅,L ₆ andLL ₆ chondrites. The extent to which the original structure disappears and the boundaries of chondrules become indistinct decreases from type 6 through type 5 to type 4, reflecting different degrees of thermal metamorphism. Major minerals in the meteorites all exhibit signs of low to medium shock metamorphism. Specific activity, depth effect and orbit effect are also measured on some chondrites that have fallen in recent years and some new information has been obtained with respect to the orbit and source region for meteorite parent bodies in space. This results show that the environment of formation ofE group may be nearer to Mars than that ofO group. Each chemical group of chondrites has its own evolutionary history, and chondritets of different chemical groups may have originated from parent bodies of different compositions. Or owing to the differentiation caused by thermal melamorphism, various kinds of meteorites may be derived from a common parent body. From this argument it is suggested that five stages may be recognized during the formation process of chondrites.  相似文献   

An equal area conversion model for rasterization of vector polygons     

ZHOU ChengHu  OU Yang  YANG Liao  QIN Biao 《中国科学D辑(英文版)》2007,50(Z1):169-175

Vector-raster conversion is one of the classic research topics in the field of Geographical Information Systems (GIS). The algorithms commonly used in GIS are devoted to maintaining the vector polygons' shape characteristics, but neglect the gain and loss of a polygon's area, which is another important attribute. This paper proposes an equal-area conversion model based on an area compensation optimization principle. According to the topological relationship among polygons and boundary grids, a neighborhood compensation principle was adopted to assign the attributes of boundary grids and a global optimization algorithm was developed to minimize area distortion in the whole data set. Two experiments were designed and the results indicated that this algorithm not only guaranteed the area error is as small as possible, but also has the advantage as being adaptive to polygon shape and spatial structure.  相似文献   

南秦岭凤凰山地区元古代构造基底特征   总被引：5，自引：0，他引：5  

齐文  王向利  王炜红  王北颖  白定邦  张彪 《陕西地质》2002,20(2):9-19

依据在原划武当岩群中获得的 1 6 86± 4 5Ma (锆石U -Pb)同位素测年资料 ,结合岩石学、岩石地球化学及区域地层对比 ,从中解体出姚坪岩组。通过岩石学、岩石地球化学、构造特征、变质变形特征研究及形成环境探讨认为 :南秦岭凤凰山元古代武当岩群 (包括姚坪岩组、杨坪岩组 )变质火山岩系为古—中元古代时期多岛洋构造环境过渡基底建造 ;耀岭河岩组浅变质火山岩为本区Rodina事件的产物。该成果对南秦岭构造基底的组成、发展、演化研究具有重要意义。  相似文献   

小兴安岭黑大公路沿线多年冻土分布及退化状态   总被引：3，自引：8，他引：3  

王彪  盛煜  刘建平 《冰川冻土》2001,23(3):302-306

黑大公路沿线多年土主要分布于黑河－北安段，属小兴安岭岛状多年冻土区，该区存在的多年冻土是晚全新世寒冷时期的产物，现处于欧亚多年冰土南界边缘，多年冻土发育在低洼、地表积水、塔头草生长茂密、草炭和泥炭发育的沼泽化湿地当中，沼泽湿地独特的热交换特性决定了其中发育的多年冻土处于退化的最晚阶段，冻土的退化在自然条件下可能依赖于由于至上的地下热流。多年冻土的地温剖面表现为零梯度曲且冰土温度接近于0℃，由此决定了多年冻土对人为活动干扰的敏感性。  相似文献   

珠江三角洲工业地域分工研究   总被引：13，自引：2，他引：13  

欧阳南江 《地理学报》1996,51(1):44-50

本文从专业化部门的数量和发展水平以及专业化部门地区分布和组合两方面揭示珠江三角洲工业地域分工的基本特点。指出新形势下虽然不少县市存在专业化部门多而不精，工业结构趋同的问题，但珠江三角洲地域分工格局已开始形成。文章还讨论了形成工业地域分工特点的原因并提出了完善地域分工的措施。  相似文献   

弱受迫作用下大气对流运动进入混沌的条件及分岔途径     

吴勇  欧阳首承 《气象学报》1992,50(3):373-377

Guckenheimer和Holmes针对弱受迫系统或如下的小参数受迫方程组  相似文献   

冷迳流的稳定性及其解析解的分析     

欧阳首承  朱克云  肖天贵 《大气科学》1992,16(4):502-507

本文利用相法讨论了y方向无限伸延的冷迳流方程.首先发现其非线性项作用由于z方向上的补偿作用而消失,即其相空间的方程是四阶线性常微分方程.利用Hurwitz方法分析其稳定时,证明了唯有中性大气符合冷迳流的稳定性条件.其解析解的趋势表明与观测结果类似.  相似文献   

海洋平均重力异常计算与精度估计     

黄谟涛  管铮  欧阳永忠 《武汉大学学报(信息科学版)》1995,(4)

提出了一种简便实用的重力异常推值方法──方位距离加权中数法，给出了直接使用重力异常变化梯度作为衡量平均重力异常计算精度的尺度，并运用ＯＳＵ９１Ａ模型成功地建立起重力异常变化梯度与平均重力异常计算精度的相关关系，通过此关系可对海洋平均重力异常计算精度作出比较可靠的估计。  相似文献   

中低纬过渡地区潜热影响下中尺度扰动的对称发展          下载免费PDF全文

吴勇  欧阳首承 《大气科学》1995,19(5):631-635

本文引入第二科里奥利参数讨论了中低纬过渡地区含非绝热(潜热)作用的对称扰动波包发展问题。结果表明:这一地区扰动波包的发展不仅包含了中高纬度波包发展条件［1］，而且与潜热和基本风场梯度经向切变及波包传播的非垂直性有关。过渡地区基本风场的作用是通过第一和第二科里奥利参数完成的。  相似文献   

庐山-彭山地区伸展构造演化及其对矿产形成的制约   总被引：3，自引：0，他引：3       下载免费PDF全文

罗庆坤  项新葵 《地质科学》1995,30(2):117-129

庐山-彭山地区原是一个经受印支早期伸展机制下所形成的变质核。它在后期又经受了挤压和伸展的多期构造叠加,致成今日面貌。印支早期所形成的伸展拉覆断层为庐、彭及其相关地区的燕山期矿液活动提供了良好的导矿和储矿空间,对矿产的形成与分布起着重要制约。  相似文献