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311.
北祁连山元古宙末-寒武纪主动大陆裂谷火山作用 总被引:13,自引:2,他引:13
北祁连山元古宙末-寒武纪大陆裂谷火山岩系为双峰式火山岩套,主要由基性与酸性火山岩组成。基性火山岩有磁性玄武岩与拉斑玄武岩两个岩浆系列,且富集LREE与LIL,其岩浆源区为与洋岛玄武岩源相似的富集地幔柱源。软流圈地幔柱上涌导致岩石圈地慢部分熔融,其熔体与地幔柱衍生熔浆混合,形成本区具有中等钕,锶同位素比值特点的基性岩浆。基性岩浆上侵至陆壳,引起下部陆壳深熔,产生长英质岩浆。地幔柱上隆促使大陆扩张,及至形成北祁连山元古宙末-寒武纪大陆裂谷。 相似文献
312.
新疆东昆仑白干湖钨地球化学块体的确立及意义 总被引:7,自引:0,他引:7
新疆东昆仑是我国西部地质工作程度较低地区之一,白干湖钨地球化学块体的确定及白干湖钨锡矿床的发现成为该区矿产勘查中突破性的进展.文章概述了白干湖钨地球化学块体的地质、矿产及地球化学特征.对该块体与成矿的关系进行了探讨,认为钨地球化学块体为白干湖钨锡矿床的形成提供了丰富的成矿物质,钨的成矿与岩浆的演化有着密切的成因关系.指出白干湖钨锡矿床有望成为超大型矿床,新疆东昆仑地区有望成为我国一个新的钨矿远景区和新的钨矿产区. 相似文献
313.
以南岭山地不同海拔高度的冠层树种为研究对象,通过无人机遥感手段获取冠幅、冠周长和冠面积(CA)等树冠性状,探讨其与基径(BD)、胸径(DBH)、2米径(D2)和4米径(D4)等树干性状间的关联性,并构建了冠面积与树干性状间的回归方程。结果表明:南岭山地树冠性状与树干性状的典型变量显著相关(R=0.89,P<0.01),并且这种相关性随海拔的升高(600 m到1 600 m)总体呈“M”型变化。其中,冠面积与树干性状间的相关性最高,可作为单一自变量反演树干性状,具体方程为:DBH=0.35CA+14.88 (R2=0.67),BD=0.41CA+17.89 (R2=0.82),D2=0.33CA+14.14 (R2=0.84),D4=0.35CA+11.3 (R2=0.86)。文章构建的冠面积与树干性状间的回归方程,可作为南岭山地森林生物量遥感反演的基础,也可用于指导南岭森林生态系统的长期监测。 相似文献
314.
315.
The mechanism of Au dispersion in sediments of mountainous desert environments has been studied in two different areas of the Chilean Andes. The San Pedro de Cachiyuyo placer (ca. 1800 m a.s.l.) consists of alluvial fans and ephemeral stream sediments deposited in a stable piedmont. The primary Au source is Cu–Au-bearing hydrothermal tourmaline breccia. The relief of this area is low (1850 m) and the average annual rainfall is ca. 20 mm. The La Coipa area (ca. 4000 m a.s.l.) is characterized by a rugged relief. The annual average rainfall is ca. 100 mm. The sedimentary deposits are less sorted than in San Pedro de Cachiyuyo and consist of ephemeral stream alluvium and slope deposits formed in a periglacial environment. The primary Au sources are two volcanic-hosted epithermal precious metal deposits. At San Pedro de Cachiyuyo, the halo is less than 1 km in length and the highest Au concentration are observed at the break in slope between the hillside and the piedmont. In the La Coipa area, Au was only detected by chemical analysis in the 125–63 μm and <63 μm fraction; however, the dispersion halo extends for over 10 km from the source. In both cases the geochemical signal of gold was strongest in the fraction <63 μm. 相似文献
316.
1990~1991年新疆地质矿产局沿西天山木扎尔特河和独库公路进行了专题综合地质研究,建立了新的地层系统和地层分区。10年来,国家305项目和石油勘查部门陆续开展了大量地层研究,先后发表数十篇科研论文和专著,在生物地层、岩石地层、层序地层、年代地层、磁性地层和构造地层等方面取得了重要进展,为西天山今后进一步深入开展地质矿产勘查提供了基础资料。这里着重介绍了生物地层、岩石地层、层序地层研究现状,并指 相似文献
317.
Zhang Hongfei Zhang Benren Zhong Zengqiu Gao Shan Hu Shenghong Faculty of Earth Sciences China University of Geosciences Wuhan 《中国地质大学学报(英文版)》2000,11(4)
INTRODUCTIONTheQinling Tongbai DabieorogenicbeltisacollisionalorogenicbeltbetweentheSino KoreanandYangtzecratons.Ultrahighpressure (UHP)andhighpressure (HP)metamor phicrockssuchascoesite bearingeclogitesarewidelydistribut edintheeasternendoftheorogenicbelt … 相似文献
318.
桐柏蔡家凹岩片内寒武纪高肌虫的发现及其地质意义 总被引:5,自引:0,他引:5
本文描述了河南桐柏西北部蔡家凹大理岩岩丰富的高肌虫化石Tongbaiella xinjiensis gen.et sp.nov.、Xianzheella henanensis sp.nov.和Mononotella cf.chuanshanensis Huo etShu及小壳化石Conotheca sp.共有4属4种。据此确定含化石地层为寒武系,属浅海沉积环境。该生物群的发现为解决桐柏大别造山带与 相似文献
319.
Livestock behaviour in the Pyrenees includes free grazing and a long resting period that provokes the accumulation of dung and urine in some places,so-called camping areas. The aims of this study were (i) to analyze any change in floral composition,and in nutritional and chemical contents of plants in a livestock camping area; and (ii) to relate the floral composition with soil chemical properties. In a linear transect,five sampling zones were established,from the centre of the camping area to the surrounding Nardus stricta-dominant pasture. The above ground plant biomass and the topsoil were sampled in each zone with 6 replicates per zone. Plant species were classified and weighed to calculate above ground biomass,nutritional and chemical contents,and Shannon diversity and evenness indices. Additionally,soils were sampled in two periods,at the beginning and at the end of grazing period. Soil available nutrients (nitrate,ammonium,phosphorus,potassium,calcium and magnesium),total nitrogen,organic carbon and pH were measured.
Plant chemical contents (protein,lignin and others) were significantly related to the proportions of grasses,legumes and other plants; so,the protein content is positively correlated with legumes plant biomass while lignin content is negatively correlated with grasses. Both plant and soil nutrients increased linearly towards the centre of the camping area. However,the relationship among plant species richness,diversity and evenness relative to its position along the studied transect was bell-shaped. From the outskirts to the centre of the camping area,plants with low nutrient demand were progressively replaced by those with medium and high nutrients demand and by pioneers.
Nardus stricta-dominant pasture has low plant diversity and plant nutrient content as well as a poor soil nutrient availability. The presence of the camping area introduced patches with more soil nutrients and new species in the large spatial scale. However at a small spatial scale,the strong soil nutrien 相似文献
Plant chemical contents (protein,lignin and others) were significantly related to the proportions of grasses,legumes and other plants; so,the protein content is positively correlated with legumes plant biomass while lignin content is negatively correlated with grasses. Both plant and soil nutrients increased linearly towards the centre of the camping area. However,the relationship among plant species richness,diversity and evenness relative to its position along the studied transect was bell-shaped. From the outskirts to the centre of the camping area,plants with low nutrient demand were progressively replaced by those with medium and high nutrients demand and by pioneers.
Nardus stricta-dominant pasture has low plant diversity and plant nutrient content as well as a poor soil nutrient availability. The presence of the camping area introduced patches with more soil nutrients and new species in the large spatial scale. However at a small spatial scale,the strong soil nutrien 相似文献
320.
秦岭大巴山地形对陕南强降水的影响研究 总被引:8,自引:3,他引:8
通过对地形敏感性试验的数值分析,认为大巴山使秦岭山脊、汉江河谷降水减小;使秦岭东南坡和渭河河谷下游强降水增加,大巴山本身降水增加幅度最大;大巴山峡口地形将大量暖湿气流向北输送,在秦岭南侧和东侧的迎风坡上产生强降水,而峡口两侧由于地形阻挡气流通过,使其下游地区降水减少。秦岭使大巴山和汉江河谷、陕北降水增加,使山脉本身降水减少,秦岭山脉对降水的影响主要是通过地形产生的垂直次级环流实现的;秦岭的地形高度变化与山脊降水量具有反相关关系,与山谷降水量关系不明显。 相似文献