The State of Arts: Sources,Microbial Processes and Ecological Effects of Iron in the Marine Environment     

Shibo Feng  Yuelu Jiang  Zhonghua Cai  Yanhua Zeng  Jin Zhou 《地球科学进展》2019,34(5):513-522

Iron is the fourth most abundant element in the earth's crust, and it often appears as a trace element in the ocean. Iron has a variable valence and diverse functions, and is an important force to regulate marine primary productivity and drive the geochemical cycle in the ocean. Previous studies have shown that iron plays an important role in maintaining primary productivity, coupling matter cycles, and regulating the transformation of biogenic factors. In recent years, with the development of microbial ecology, iron research has enter more in-depth levels, including microbial-driven iron oxidation-reduction behavior, metabolic processes, and interactions with other major elements(C/N/P). This paper attempts to review the latest progress of iron, focusing on the published literatures of the past fifteen years. Firstly, we explained the sources and occurrence states of iron in the ocean (such as dissolved, colloidal, granular and organic state); Secondly, we reviewed the types and process mechanisms of microbial-mediated iron redoxbehavior (for example nitrate oxidation, and biological reduction, etc.); Finally, we summarized the coupling relationship between iron and C/N/P cycle. Additionally, the ecological roles of iron in specific ecological event (for instance algal bloom) has also been described. Furthermore, the "chemical-biological-physical" theoretical framework for marine iron research is also discussed. The purpose of this paper is to provide more information for marine microecological research and their effects on iron cycle under changing environment, such as global change.  相似文献   

Biological Processes Responsible for Travertine Deposition: A Review and Future Prospect     

Zhijun Wang  Jianjun Yin  Junbing Pu  Daoxian Yuan 《地球科学进展》2019,34(6):606-617

The investigation of biological processes responsible for travertine deposition allows us to better understand the travertine petrographic and geochemical signatures as proxies of climatic and environmental change. This paper reviewed the organisms associated with travertines, the biotic micro-fabrics formed within travertines, the biological processes associated with travertine precipitation and their controls on travertine geochemical properties. Prospects of the future research on biological processes responsible for travertine precipitation were provided. Bacteria, algae and mosses are the most important organisms that involve in the precipitation of travertines. The growth of these organisms leads to the formation of a range of various porosity, crystal fabrics and lamination within travertines. Three main biological processes responsible for travertine deposition can be classified, including \mathrm{①} a process of aquatic plant growth generating a turbulent condition and consequent CO₂ evasion, \mathrm{②} a metabolic (mainly photosynthetic) process mediating carbonate precipitation and \mathrm{③} a ‘surface-control’ process influencing nucleation and crystal growth. These processes play an important role in the migration and transformation of elements in travertine-depositing system and thus determine the properties of water chemistry and geochemistry of carbonate deposits. Travertine deposits have great potential to be valuable records for the geobiological study. Further investigation is required to simultaneously track biotic and abiotic interactions in modern travertine-depositing environments and quantify the contribution of these two processes and apply the results to accurately interpret travertine records.  相似文献   

COMPUTATIONAL SIMULATION OF RIVER SEDIMENTATION AND MORPHOLOGY - A REVIEW OF THE STATE OF THE ART     

SamS.Y.WANG WeimingWU 《国际泥沙研究》2005,20(1):7-29

In this paper, the state-of-the-art computational simulation technologies for river sedimentation and morphology are comprehensively reviewed. Emphasis is on computational modelling, which includes mathematical modelling equations and closures, numerical solution methods, verification and validation, model integration, and applications. Several important areas of future research are recommended.  相似文献   

高原降雨天气过程中总体输送系数的变化特征   总被引：5，自引：2，他引：3  

李国平  陶红专 《高原气象》2005,24(4):577-584

以中日亚洲季风机制合作研究计划设在西藏的4个自动气象站（AWS）获得的近6年（1995年7月-1999年6月）观测连续、时次密集的近地层大气梯度观测资料为基础,选取了高原中、东部夏季雨季的一些典型降雨过程,应用廓线-通量法计算了这些站降雨过程中每隔20min一次的总体输送系数,分析了其随层结稳定度、地表粗糙度以及在降雨天气过程中的变化特征。结果表明：总体输送系数的变化与近地层大气层结稳定度、地表粗糙度具有确定的、密切的关系;总体输送系数对降雨天气过程有明显的响应,但在与降雨过程的雨量峰值、降雨时段的对应上,各站的规律性略有不同。  相似文献   

湖北枣阳大阜山镁铁/超镁铁杂岩体与金红石矿床成因   总被引：3，自引：0，他引：3       下载免费PDF全文

洪吉安  马斌  黄琦 《地质科学》2009,44(1):231-244

湖北省北部枣阳市境内的大阜山镁铁/超镁铁杂岩体主要由未变质的纯橄岩和橄长岩组成,伴生变质的石榴石角闪石岩、石榴石钠黝帘石角闪石岩和角闪石钠黝帘石岩.杂岩体的围岩为大理岩.该岩体中的金红石矿床产于变质的石榴石角闪石岩或蚀变的石榴石角闪石岩中.橄长岩中锆石SHRIMP U-Pb同位素定年结果表明镁铁/超镁铁质岩体的成岩年龄约为600Ma.变质的岩石和未变质的岩石几乎具有完全相同的地球化学特征,表明前者的原岩应为橄长岩,整个岩体是一个分异的镁铁/超镁铁侵入体.金红石赋存于角闪石解理中等岩相特征表明矿床的含矿岩石就是石榴石角闪石岩,不是由石榴石辉石岩退变质形成的;且其中的石榴石为钙铁榴石,不是富镁、富铝的与高压/超高压作用有关的石榴石.金红石矿床的形成和岩体的局部变质应该与由北向南的近水平推覆构造有关,动力变质作用提供的热和流体,结合推覆过程中的变形作用,导致围岩大理岩和镁铁质岩体发生交代作用,形成石榴石角闪石岩和金红石矿床.  相似文献   

湘东北地区连云山花岗岩的成因及地球动力学暗示   总被引：6，自引：2，他引：4  

许德如  王力  李鹏春  陈广浩  贺转利  符巩固  吴俊 《岩石学报》2009,25(5):1056-1078

江南古陆是华南地区一个重要的花岗岩和金及金多金属矿床集中区。位于该区中段的连云山晚中生代花岗岩具有高的SiO₂ (69.41%~75.14%)和Al₂O₃ (13.61%~17.46%)、相对偏低的铁镁质 (0.92%~3.14%)以及变化范围较大的Na₂O (2.04%~3.83%)、K₂O (1.94%~4.94%)和CaO (0.82%~3.24%)等氧化物含量;在微量元素和稀土元素组成上,Y (5.2×10^-6~18.0×10^-6)和Yb (大多数在0.29×10^-6~0.70×10^-6)丰度普遍偏低、而Sr/Y (多数在55与82之间)和(La/Yb)_N (大多数在31与111之间)比值较高,且普遍表现LREE强烈富集的REE配分特征。结合Sr (⁸⁷Sr/⁸⁶Sr_i=0.71008~0.73852)-Nd (ε_Nd(t)=-9.95~-12.37)-Pb (²⁰⁶Pb/²⁰⁴Pb _i=17.972~19.959)同位素组成,以及野外地质和岩相学特征,连云山岩体为典型的强过铝质花岗岩,并显示埃达克质岩地球化学亲和性,是玄武质岩浆底侵作用下由加厚的下地壳部分熔融产生的岩浆经同化混染和分异结晶而形成,其源岩可能主要为变杂砂岩、长英质片麻岩和变英云闪长岩。结合区域构造演化,我们推测晚中生代连云山花岗岩是三叠纪时期华北板块和扬子板块碰撞导致地壳加厚及随后的太平洋板块向华南大陆俯冲导致华南大陆伸展、减薄的联合作用构造背景下,主要由古元古代连云山群(?)物质部分融熔而产生。连云山花岗岩的成因及地球动力学背景的研究将有助于深刻揭示湘东北地区金和金多金属矿产形成的地球动力学机制。  相似文献   

地壳深部岩浆岩岩基体与大型、超大型金属矿床的形成及找矿效应   总被引：6，自引：1，他引：5  

滕吉文  姚敬金  江昌洲  闫雅芬  杨辉  张永谦  阮小敏 《岩石学报》2009,25(5):1009-1038

基于部分大型、超大型金属矿床和多金属矿集区的地球物理研究发现:地壳内部物质在热动作用下,深部物质和能量强烈的在交换,当深部热液沿通道（破碎带、软弱岩层或断裂系）上涌时,在深部适宜的岩层部位聚积,并形成大型或较大型的酸性、中酸性或基性的岩基体（镁铁质、超镁铁质）。这些类型的岩浆岩以其携带的热能驱动着深部物质重新分异和调整,并在这一动力作用过程中与围岩进行交代、蚀变,并促使其不断变质。在这样的深部介质和构造环境下矿物元素得以在大型或较大型岩基体附近与周边介质耦合,逐使矿物元素不断聚积,并形成大型、超大型金属矿床和多金属矿集区。  相似文献   

Topographic expression of active faults in the foothills of the Northern Apennines     

Vincenzo Picotti  Alessio Ponza  Frank J. Pazzaglia 《Tectonophysics》2009,474(1-2):285

Active faults that rupture the earth's surface leave an imprint on the topography that is recognized using a combination of geomorphic and geologic metrics including triangular facets, the shape of mountain fronts, the drainage network, and incised river valleys with inset terraces. We document the presence of a network of active, high-angle extensional faults, collectively embedded in the actively shortening mountain front of the Northern Apennines, that possess unique geomorphic expressions. We measure the strain rate for these structures and find that they have a constant throw-to-length ratio. We demonstrate the necessary and sufficient conditions for triangular facet development in the footwalls of these faults and argue that rock-type exerts the strongest control. The slip rates of these faults range from 0.1 to 0.3 mm/yr, which is similar to the average rate of river incision and mountain front unroofing determined by corollary studies. The faults are a near-surface manifestation of deeper crustal processes that are actively uplifting rocks and growing topography at a rate commensurate with surface processes that are eroding the mountain front to base level.  相似文献   

Thermo-hydro-mechanical simulation of ATLAS in situ large scale test in Boom Clay     

Bertrand François  Lyesse LalouiClément Laurent 《Computers and Geotechnics》2009

Following the need for understanding and quantifying the effect of temperature on the response of a candidate host formation for radioactive waste disposal, finite element modelling of an in situ thermal experiment has been carried out. Based on a thermo-hydro-mechanical (THM) finite element approach including a consistent thermo-plastic constitutive model, it has been possible to reproduce the THM response of a clay formation submitted to in situ thermal loading. The simulated large-scale experiment, called ATLAS was designed in the underground research facility (HADES-URF) in Mol, Belgium. After an extensive literature analysis on the thermal, hydraulic and mechanical characteristics of Boom Clay, laboratory tests were simulated to calibrate model parameters. The results of the finite element modelling of the ATLAS experiment were compared with in situ measurements and revealed the necessity to account for flow diffusion in all three directions through a 2D axisymmetric analysis. Finally, those results were interpreted in the light of elasto-thermoplasticity, which emphasizes the significant role of thermo-plastic processes in the global THM response of the clay formation.  相似文献   

雷暴电过程对动力发展的影响研究   总被引：9，自引：1，他引：8  

孙安平  张义军  言穆弘 《高原气象》2004,23(1):26-32

利用三维时变积云动力—电过程耦合模式对雷暴中的电过程对动力发展的影响进行了模拟计算。结果表明,随着雷暴云体发展,云内形成三极性电荷结构。电场力对雷暴发展的直接作用与动力场相比很小,电涡度10-6·s-1比动力涡度小两个量级。但电场力影响了雷暴中的微物理过程,特别是水成物粒子的降落速度,并通过对三相水成物之间转换过程的调制,改变了三相水成物的时空结构,使云中水汽总量增加41%,释放潜热增加19.4%,从而改变了流场结构,电涡度达到10-4·s-1量级,和动力涡度相当。模拟结果指出,雷暴内电过程在云体成熟阶段对雷暴发展有较大影响。  相似文献