山西太岳山种子植物区系特征     

柴宝峰  李毳 《山地学报》1997,(3)

调查的基础L，统计了太岳山种子植物有97科、316属、575种（含变种），分析了该区系的主要特征，即植物区系地理成分复杂，温带成分占优势；植物资源种类丰富，区系起源古老；植物区系具明显的过渡性；植被类型复杂，具明显的垂直分布．对该区野生经济植物进行了分类统计，为植物资源合理利用与生物多样性保护提供了基础资料穹科学依据．  相似文献   

南天山北缘麻粒岩残迹与辉石相韧性变形研究   总被引：9，自引：4，他引：9       下载免费PDF全文

舒良树  王赐银 《地质科学》1996,31(4):375-383

对新疆北部南天山北缘蛇绿混杂岩带中麻粒岩的岩石学、矿物学、岩石化学、矿物化学、稀土元素地球化学特征及辉石相韧性变形构造的研究表明,榆树沟麻粒岩的共生矿物组合为透辉石-次透辉石-紫苏辉石-石榴石-斜长石,属基性岩类暗色麻粒岩,以低硅高钙为特征,稀土总量低,轻稀土与铕弱亏损,反映高温高压熔融环境和岩浆分异差的特点。麻粒岩及超镁铁岩中的辉石经历了强烈的韧性剪切变形作用,不对称辉石残斑系、动态重结晶辉石亚颗粒集合体、辉石变形双晶纹、鱼尾构造、核幔构造等显微韧变构造广泛发育。宏观和微观运动学分析揭示了一期从南向北的推覆构造。麻粒岩的形成与早古生代大陆地壳拉伸作用有关,辉石相韧性变形则与早古生代末南天山边缘海的挤压关闭和推覆逆冲有关。  相似文献   

南天山蛇绿混杂岩和中天山南缘糜棱岩的⁴⁰Ar/³⁹Ar年龄及其大地构造意义   总被引：8，自引：0，他引：8       下载免费PDF全文

蔡东升  卢华复  贾东  吴世敏  陈楚铭 《地质科学》1996,(4):384

 ⁴⁰Ar/³⁹Ar同位素年龄测定,获得南天山蛇绿混杂岩基质黑云母石英片岩单矿物黑云母的两个坪年龄分别为(370.0±4.8)Ma和(259.0±3.3)Ma;中天山南缘长英质糜棱岩单矿物黑云母的坪年龄为(250.5±7.9)Ma,二云母花岗岩单矿物白云母的坪年龄为(348.9±0.3)Ma。结合南天山古生代沉积特征和塔里木及伊犁-哈萨克斯坦板块古地磁数据的综合分析,提出南天山晚泥盆世至石炭纪早期完成向伊犁-哈萨克斯坦板块的B型俯冲,中-晚二叠世进行陆内A型俯冲造山的板块碰撞演化模式。  相似文献   

黔南绿色花岗石资源及开发利用前景     

李毅 《矿产与地质》1996,(3)

黔南地区花岗石资源丰富。绿色花岗石矿体由辉长辉绿岩（内部岩相）、辉绿岩（过渡岩相）和辉绿玢岩（边缘岩相）以及钠长石脉岩组成，以过渡岩相辉绿岩体为石材主要开采对象。矿体厚度大，分布广，成荒率高，石材花色品种好，具有很大开发前景  相似文献   

Current controlled sediment deposition from the shelf to the deep ocean: the cenozoic evolution of circulation through the SW pacific gateway     

R. M. Carter  L. Carter  I. N. McCave 《International Journal of Earth Sciences》1996,85(3):438-451

 The circulation of cold, deep water is one of the controlling factors of the Earth's climate. Forty percent of this water enters the world ocean through the Southwest Pacific as a deep western boundary current (DWBC) flowing northwards at bathyal to abyssal depths, east of the New Zealand microcontinent. South of latitude 50°S, the DWBC is intimately linked with the Antarctic circumpolar current (ACC), which is the prominent force for the shallow-water circulation. The Pacific DWBC is presently the largest single contributor of deep ocean water, and deciphering its evolution is of fundamental importance to understanding ocean and climate history, and global ocean hydrography. The evolution of the DWBC system, and of related circum-Antarctic currents, has taken place since 30–25 Ma when plate movements created the first oceanic gaps south of Australia and South America. The stratigraphic record preserved in sediment drifts of the Southwest Pacific, in eastern New Zealand, is the best available for deciphering the Neogene history of Southern Ocean water masses, and of the circulation of the ACC, DWBC and their precursor systems. Major current activity commenced on the New Zealand margin in the late Eocene or early Oligocene (Hoiho Drift; early ACC) and was widespread by the mid-late Oligocene (Marshall Paraconformity and Weka Pass Limestone drift; ACC). During the Neogene the eastern South Island continental shelf built seawards by accretion at its outer edge of large Miocene current drifts up to tens of kilometres long and hundreds of metres thick (Canterbury drifts). Also commencing in the mid-Cenozoic, but in depths >2000 m, the DWBC emplaced large deep-water sediment drifts. Rates of drift deposition accelerated considerably in the late Neogene, when climatic change (and particularly glacial sea-level falls) caused the delivery of large volumes of turbiditic sediment into the path of the DWBC via the Bounty and Hikurangi channels. Received: 9 August 1995 / Accepted: 15 January 1996  相似文献   

华南西部晚二叠世碳同位素地层学研究   总被引：1，自引：1，他引：1  

邵龙义  张鹏飞 《地层学杂志》1997,21(4):312-320

对黔桂地区７条晚二叠世碳酸盐岩型煤系剖面进行了碳酸盐岩碳氧同位素测定，发现晚二叠世吴家坪阶与长兴阶碳酸盐岩的δ１３Ｃ值有明显差异，前者δ１３Ｃ多大于３．０‰，后者多小于３．０‰，进一步对晚二叠世δ１３Ｃ的变化原因的分析表明，δ１３Ｃ的变化可能与晚古生代末期聚煤作用的减弱密切相关，后者造成自然界碳库中的１２Ｃ的富集，从而使得海水以及在其中沉淀出的碳酸盐岩中的δ１３Ｃ值降低。此外，植物光合作用从大气中吸收ＣＯ２的量也随陆地植被减少而减少，结果造成大气中的ＣＯ２的大量富集，从而进一步产生温室效应，制约生物界的发展。联系到这一阶段生物界的衰亡灭绝，可以认为温室效应是晚二叠世生物逐渐衰亡及晚二叠世末群体灭绝的主要原因之一。  相似文献   

安徽省大别山南部宿松杂岩变质作用研究   总被引：7，自引：13，他引：7  

魏春景  单振刚 《岩石学报》1997,13(3):356-368

宿松杂岩的变质作用可分为３个阶段：早期、主期和晚期阶段。主期阶段的矿物组合在云母片岩中为石榴石＋多硅白云母＋石英＋磁铁矿±钠云母±绿帘石／黝帘石；在白云母钠长（二长）片岩和片麻岩中为石榴石＋多硅白云母＋钠长石＋石英＋绿帘石／黝帘石±冻蓝闪石；在石榴石钠长角闪岩中为石榴石＋冻蓝闪石＋钠长石＋黝帘石＋石英±钠云母±金红石／磁铁矿。根据多种地质温压计和变质反应可以推测主期变质条件为：Ｔ＝５２０℃～５８０℃，Ｐ＝１．２～１．４ＧＰａ，地热梯度为１２℃／ｋｍ，相当于高压过渡型。晚期阶段变质条件为：Ｔ＝４６０℃～４８０℃，Ｐ＝０．６～０．７ＧＰａ，为中压绿帘角闪岩相。宿松杂岩的变质条件介于其南部的蓝闪绿片岩相和北部的榴辉岩相之间，三者是扬子板块向华北板块之下俯冲到不同深度的产物。  相似文献   

Geohydrological models and earthquake effects at Yucca Mountain, Nevada     

J. B. Davies  Charles B. Archambeau 《Environmental Geology》1997,32(1):23-35

 Yucca Mountain, the proposed site for the high-level nuclear waste repository, is located just south of where the present water table begins a sharp rise in elevation. This large hydraulic gradient is a regional feature that extends for over 100 km. Yucca Mountain and its vicinity are underlain by faulted and fractured tuffs with hydraulic conductivities controlled by flow through the fractures. Close to and parallel with the region of large hydraulic gradient, and surrounding the core of the Timber Mountain Caldera, there is a 10- to 20-km-wide zone containing few faults and thus, most likely, few open fractures. Consequently, this zone should have a relatively low hydraulic conductivity, and this inference is supported by the available conductivity measurements in wells near the large hydraulic gradient. Also, slug injection tests indicate significantly higher pressures for fracture opening in wells located near the large hydraulic gradient compared to the opening pressures in wells further to the south, hence implying that lower extensional stresses prevail to the north with consequently fewer open fractures there. Analytical and numerical modeling shows that such a boundary between media of high and low conductivity can produce the observed, large hydraulic gradient, with the high conductivity medium having a lower elevation than the water table. Further, as fractures can close due to tectonic activity, the conductivity of the Yucca Mountain tuffs can be reduced to a value near that for the hydraulic barrier due to strain release by a moderate earthquake. Under these conditions, simulations show that the elevation of the steady-state water table could rise between 150 and 250 m at the repository site. This elevation rise is due to the projected shift in the location of the large hydraulic gradient to the south in response to a moderate earthquake, near magnitude 6, along one of the major normal faults adjacent to Yucca Mountain. As the proposed repository would only be 200–400 m above the present water table, this predicted rise in the water table indicates a potential hazard involving water intrusion. Received: 7 June 1996 / Accepted: 19 November 1996  相似文献   

疏勒河断裂中段新构造应力场的遥感分析   总被引：1，自引：0，他引：1  

刘林清  余运祥 《华东地质学院学报》1997,20(4):336-342

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GRADIENT DISTRIBUTION OF ACID RAIN IN THE SCENIC RESORT OF THE BAIYUN MOUNTAIN IN GUANGZHOU     

黄健  李福娇  江奕光  李琼 《热带气象学报(英文版)》2004,10(1):95-105

1 INTRODUCTION Sitting in the central part of the Pearl River Delta, Guangzhou is one of the cities in China that are most polluted by acid rain. Broad attention has been brought to the problem. Since the early 1980s, a series of observation and studies h…  相似文献