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1.
以大平山铜矿、天台山黄铁矿矿为例,阐述了该区的矿区、矿床地质及火山机构特征,并从成矿时间、空间及成因三个方面论述了矿床成矿与古火山机构的关系。 相似文献
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The Sanchazi mafic-ultramafic complex in Mianlue tectonic zone, South Qinling can be subdivided into two blocks, i.e. Sanchazi paleo-magmatic arc and Zhuangkegou paleo-oceanic crust fragment (ophiolite). The Sanchazi paleo-magmatic arc is mainly composed of andesite, basaltic and basalt-andesitic gabbro (or diorite), andesitic dyke, plagiogranite and minor ultramafic rocks, which have typical geochemical features of island arc volcanic rocks, such as high field strength element (e.g. Nb, Ti) depletions and lower Cr, Ni contents. The Light rare earth element (LREE) and K enrichments of these rocks and zircon xenocrystals of 900 Ma from plagiogranite suggest that this magmatic arc was developed on the South active continental margin of the South Qinling micro-continent. The U-Pb age of (300 ± 61)Ma for zircons from plagiogranite indicates that the Mianlue paleo-oceanic crust was probably subducted underneath the South Qinling micro-continent in Carboniferous. This is consistent with the formation time (309Ma) of the Huwan eclogite originating from oceanic subduction in Dabie Mountains, suggesting that the Mianlue paleo-ocean probably extended eastward to the Dabie Mountains in Carboniferous. The high-Mg adakitic rocks in Sanchazi paleo-magmatic arc suggest that the subducted oceanic crust was relatively young (<25Ma) and hot. 相似文献
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Based on the land surface temperature (LST), the land cover classification map,vegetation coverage, and surface evapotranspiration derived from EOS-MODIS satellite data, and by the use of GIS spatial analytic technique and multivariate statistical analysis method, the urban heat island (UHI) spatial distribution of the diurnal and seasonal variabilities and its driving forces are studied in Beijing city and surrounding areas in 2001. The relationships among UHI distribution and landcover categories, topographic factor, vegetation greenness, and surface evapotranspiration are analyzed. The results indicate that: (i) The significant UHI occur in Beijing city areas in the four seasons due to high heat capacity and multi-reflection of compression building, as well as with special topographic features of its three sides surrounded by mountains,especially in the summer. The UHI spatial distribution is corresponding with the urban geometry structure profile. The LST difference is approximately 4-6℃ between Beijing city and suburb areas, comparatively is 8- 10℃ between Beijing city area and outer suburb area in northwestern regions. (ii) The UHI distribution and intensity in daytime are different from nighttime in Beijing city area, the nighttime UHI is obvious. However, in the daytime, the significant UHI mainly appears in the summer, the autumn takes second place, and the UHI in the winter and the spring seem not obvious. The surface evapotranspiration in suburb areas is larger than that in urban areas in the summer, and high latent heat exchange is evident, which leads to LST difference between city area and suburb area. (iii) The reflection of surface landcover categories is sensitive to the UHI, the correlation between vegetation greenness and UHI shows obviously negative.The scatterplot shows that there is the negative correlation between NDVI and LST (R2 = 0.6481).The results demonstrate that the vegetation greenness is an important factor for reducing the UHI,and large-scale construction of greenbelts can considerably reduce the UHI effect. 相似文献
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随着地下空间资源的开发利用,越来越多深基坑呈现出开挖深、规模大、形状不规则等特点,其支护结构设计复杂,施工难度大,具有明显的空间效应。本文以南京地铁某基坑工程为例,分析基坑施工对邻近桥梁的影响。其场区位于长江下游漫滩相二元结构地层分布地段,上部软土层厚度大,下部承压含水层地下水位高、水量丰富,地质条件复杂,该基坑为典型的深大异形基坑,距离某大桥的双曲拱引桥仅为7. 2 m,由于之前桥梁已遭受其他地下工程施工产生的较大变形,所以后续工程对其影响变形控制要求极高。为此,该车站基坑支护结构设计基于地下空间实际功能采用设置分隔墙分区开挖及MJS超深工法墙综合变形控制方案。本文通过有限元数值模拟计算,开展复杂环境下基坑开挖引起的围护结构及桥梁桩基的变形预测分析,计算结果显示,该深大狭长异形基坑开挖对邻近桥梁沉降变形影响显著,通过设置分隔墙分区开挖及MJS工法墙进行变形控制,能够较好地控制基坑的空间效应,减少“长边效应”、“异形效应”等对桥梁沉降变形的影响。通过现场基坑开挖过程实际监测结果,验证这一综合变形控制方案的可行性。该研究成果对于类似复杂地质条件下深大狭长异形基坑的支护及施工设计具有很好的借鉴意义。 相似文献
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大埠矿田位于南岭成矿带东段,是于都-赣县钨多金属矿集区重要组成,区内已发现钨多金属矿床(点)五十余处,矿床类型包括石英脉型、矽卡岩型、云英岩型和细脉浸染型等,各类矿化主要围绕大埠复式花岗岩体产出。然而,大埠矿田岩浆作用具有明显的多期次、多阶段的特点,各期次成岩成矿时代尚缺乏系统研究,各类岩浆岩与矿化关系争议较大。文章在岩体地质和矿床地质调查基础上,通过LA-(MC)-ICP-MS锆石U-Pb定年、锆石微量元素和Hf同位素分析,精确厘定了大埠花岗岩的成岩时代,探讨了多期次岩浆活动对区内成矿作用的贡献。锆石U-Pb定年结果分别为(429.1±4.7)Ma、(430.0±5.8) Ma、(431.8±4.7) Ma和(158.3±4.1) Ma,结合岩体地质填图信息,笔者认为大埠复式花岗岩基由加里东期和燕山期两部分组成。两期花岗岩均属于高钾钙碱性、过铝质S型花岗岩系列,两者均出现Eu负异常,燕山早期Eu负异常更明显。两期岩体锆石的εHf(t)值分别为-6.3~-1.3与-11.4~-7.1,对应二阶段模式年龄为1.49~1.82 Ga与1.66~1.93 Ga,指示其母岩浆为中元古代的地壳部分熔融形成。锆石微量元素特征显示,两期花岗岩均为陆壳源区、具有相近的结晶温度,燕山早期花岗岩相对于加里东期有更高的结晶分异程度,有更高的氟含量,与钨成矿具有更强的相关性。大埠矿田钨多金属成矿时代集中在159~155 Ma,紧随燕山早期花岗质岩浆侵位而形成。基于大埠矿田成岩成矿时代格架研究,结合花岗岩成矿专属性和成矿地质条件分析,构建了区内钨多金属矿勘查模型,指明了大埠矿田细脉浸染型、云英岩型、内带石英脉型钨矿的找矿方向,预测大埠岩体东北部的燕山早期隐伏岩体具有寻找“合龙式”石英大脉型和细脉-云英岩型钨矿的潜力。 相似文献
7.
Zhaochong ZHANG Houmin LI Jianwei LI Xie-Yan SONG Hao HU Lixing LI Fengmei CHAI Tong HOU Deru XU 《中国科学:地球科学(英文版)》2021,(5):691-715
The predominant types of high-grade iron deposits in China include skarn, sedimentary metamorphic(banded ironformation, BIF-type), continental/submarine volcanic-hosted and magmatic Fe-Ti-Voxide deposits. Based on a comprehensive review of current studies on these deposits, this paper suggests that the oxygen concentration in atmosphere played an important role for the formation of BIFs, whereas the tectonic setting and deep magmatic differentiation processes are more important for the other types. Notably, both high temperature and high pressure experiments and melt inclusion studies indicate that during the differentiation, high temperature magmas could develop iron-rich magma via liquid immiscibility but not pure oxide melt("iron ore magma"). Fe-P melt could be generated directly by liquid immiscibility under hydrous and oxidized condition. The formation of high-grade iron deposits is mostly associated with the processes related to multiple stages of superimposition, e.g., desiliconization and iron enrichment, removal of impurity, and remobilization and re-precipitation of iron. According to the temporal evolution, the high-grade iron deposit could be divided into multi-episode superimposition type(temporally discontinuous mineralization) and multi-stage superimposition type(temporally continuous mineralization). The former is represented by the sedimentary metamorphic iron deposit, and the latter includes those related to magmatic-hydrothermal fluids(e.g., skarn,volcanic-hosted and magmatic types). 相似文献
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Acidic species, such as Nitrate, in polar snow and firn layers are “reversibly” deposited, and are sufficiently volatile to undergo significant postdepositional exchange between snow/firn and the atmosphere. Through comparison of the snowpit and snowpack nitrate concentrations from central East Antarctica and the headwater of ürumqi River, we conclude that the nitrate peaks in the uppermost surface snow layers in central Antarctica are not related to an atmospheric signal and must account for post-depositional effects. Such effects, however, are not found in the surface snowpack nitrate profiles from the headwater of ürumqi River. Two reasons may account for the post-depositional difference. At first, nitrate in the polar snow and firn layers appears to be hydrated ion, which can be taken up by the atmosphere, while at the headwater of ürumqi River it seems mainly as mineral ion, which assembles the behavior of aerosol-derived species that are “irreversibly” deposited and do not undergo significant post-depositional exchange with the atmosphere. Secondly, the chemical features of the snow and ice on the Antarctica are mainly determined by wet deposition, to the contrary, dry deposition is more significant at the headwater of lUrumqi River than that on the East Antarctic Plateau. 相似文献
9.
遥感卫星的轨道外推方法 总被引:1,自引:0,他引:1
通过星载GPS接收机直接确定卫星星历是低轨卫星定位的一个重要手段。由于低轨卫星的高机动性和GPS接收机较低的运算速度,导致有时下传星历数据的间隔非常大,要荻取连续的卫星轨道数据需要进一步处理。在分析遥感卫星轨道特点的基础上,提出一种新的简化轨道摄动力模型,利用模型实现了轨道外推,并利用最小方差序列匹配对低轨卫星外推数据进行修正。通过仿真验证,该算法在一定时间范围内可以达到较高的精度。 相似文献
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土地利用/覆被变化研究的实质分析 与进展评述 总被引:57,自引:4,他引:57
作为当前研究的前沿领域,LUCC研究所涉及的研究内容不仅丰富而且繁杂。本文从LUCC研究计划的根本目标出发,指出LUCC所研究的诸多科学问题之间存在着紧密的联系,其实质是因果关系,而且LUCC研究可以简单明了地归纳为三个研究构成环节(LUCC原因、LUCC状况和LUCC结果)和四个核心研究内容(LUCC驱动力与驱动机制、LUCC状况、LUCC效应研究与作用机制、LUCC模型模拟与土地可持续利用),文章针对此四个方面的研究进展进行了综述。此外,作者对LUCC的研究趋势进行了展望,指出:LUCC研究的主要趋势是走向综合,LUCC的环境效应研究与LUCC微观机理与过程的研究是当前LUCC研究的两个热点,而研究尺度的综合和模型构建是LUCC研究的两大难点问题。 相似文献