Pyrite oxidation related to pyritic minesite spoils and its controls: A review

Pyrite oxidation is considered to be a main contribution to the acidification of minesite spoils and the generation of the Acid Mine Drainage (AMD) which has become the greatest threat to the ecological environment. In this paper, pyrite oxidation and its controls are reviewed with respect to the latest literature. Conceptual model and empirical rate law model with reference to indoor experiments are classified and presented to describe pyrite oxidation in heterogeneous minesite spoil piles. The influences of Thiobacillus (T) ferrooxidans on pyrite oxidation are simply summarized. In order to prevent the generation of the AMD, three approaches including the addition of alkali to minesite spoil, use of dry covers, and coating on the minesite spoil surface, are discussed.     

斑岩型铜矿床成矿斑岩岩浆氧化状态研究方法综述

近年来,成矿斑岩岩浆的氧化状态对斑岩铜矿床成矿潜力和成矿规模的控制作用受到了矿床学家的广泛关注。文章总结了斑岩型铜矿床成矿斑岩岩浆氧化状态的主要研究方法及各自的适用条件:(1)钛铁氧化物(钛铁矿-磁铁矿)固熔体的组成,适用于含共生岩浆成因钛铁矿-磁铁矿的斑岩体;(2)岩石中的Fe~(3+)/Fe~(2+)含量比值,适用于新鲜的熔融包裹体或未发生热液蚀变和地表风化作用的新鲜岩石;(3)黑云母中的Fe~(3+)、Fe~(2+)和Mg含量,适用于黑云母与磁铁矿和钾长石共生的岩体;(4)角闪石主量元素含量,适用于温度为550～1120℃、压力1200 MPa、氧逸度(f(O2))为-1≤ΔNNO≤+5的钙碱性喷出岩或浅成侵入岩;(5)锆石Ce~(4+)/Ce~(3+)比值;(6)锆石EuN/EuN*比值,斑岩铜矿成矿斑岩为中酸性岩体,其中锆石普遍发育,因此被广泛用于确定岩浆氧化状态。文章还通过收集中国冈底斯成矿带、金沙江-红河成矿带、中甸岛弧成矿带、环太平洋成矿域和中亚成矿域主要斑岩铜矿床成矿斑岩岩浆氧逸度资料,讨论岩浆演化状态对斑岩型铜矿床成矿作用和成矿规模的控制作用,发现同一成矿带内含矿斑岩的氧化状态明显高于不含矿斑岩,且含矿斑岩的氧化状态与斑岩铜矿床的成矿规模具有正相关性。     

Extrusive carbonatites: A brief review

49 known extrusive carbonatite occurrences are listed with brief details of their tectonic setting, structure, lithologies, associated silicate rocks, chemistry and presence or absence of included mantle materials. Half the occurrences appear to be related to tephra cones, tuff rings, diatremes and maars and the rest occur within strato-volcanoes. Pyroclastic carbonatitic rocks are present at all the localities, with carbonatite lava flows occurring at only 14 of them. The pyroclastic rocks, which include fallout tephra and deposits from pyroclastic surges and flows and products of phreatomagmatic eruptions, vary from rocks composed principally of carbonate to varieties with as little as 20% igneous carbonate. The most abundant silicate rocks associated with extrusive carbonatites are melilite-bearing rocks, nephelinite and/or ijolite, and phonolite and/or nepheline syenite; seven occurrences have no associated silicate rocks. 16 occurrences, most of them associated with small extrusive centres, contain mantle xenoliths or megacrysts, details of which are tabulated, with spinel lherzolite the most abundant rock type, but amphibole, phlogopite and garnet are also recorded. The lack of such materials in intrusive carbonatites may reflect their less energetic environment of emplacement. It is proposed that carbonatites are essentially of two types: (a) those rising energetically and rapidly from the mantle, which form small explosion craters, ash or tuff cones, or diatremes, have only low-volume associated silicate rocks, and entrain mantle debris, and (b) those which occur in strato-volcanoes, are associated with large volumes of silicate rocks and follow a more complex genesis, probably involving ponding and differentiation (separation from carbonate-bearing silicate magma) at higher levels in the mantle and/or crust. Most of the classic intrusive carbonatite complexes probably fall into the second category.     

The changing atmosphere: A review

Concern over the effects of human activities on this planet and on it's ecosystems is widespread. Changes wrought within the atmosphere are of particular concern because they have pervasive social, environmental, and economic effects; some potentially serious and very long-term. The problems they pose and the need for remedial measures creates both scientific and policy challenges. This paper bridges the two domains, outlining how the atmosphere is being changed, some of the possible consequences thereof, and actions being taken to address the issue.Emissions to the atmosphere are attacking the stratospheric ozone shield, causing acidification, spreading toxic substances and increasing the greenhouse effect. Of these concerns, the global issue of greenhouse warming will have the greatest overall impact and it the most difficult to address. While some countries have taken important preventative and mitigating measures, action on the greenhouse threat generally has been restrained because of related uncertainties, possible economic upsets and the enormity of the problem. The paper ends by noting recent international initiatives toward development of needed public policies and the roles of the scientist in addressing the issue.     

Nanogeology in China: A review

Nanogeology is a subject that is a combination of geology and nanoscale science, and it has been a frontier field in recent years. It is also a new subject with the features of intersectionality and multidisciplinary. Digging deeper into geological problems and nanoscale phenomena helps better revealing the more essential mechanisms and processes in geological science, which is also an evitable path in the development of geology. In this paper, we elaborate the concept, feature and main subdisciplines, and summarize three stages of nanogeology development from preliminary research in the 1990s to subject formation in China. After summarizing the researchers’ achievements in this field, we illustrate some primary research progresses of nanogeology in China as eight subdisciplines. On the basis of the above content, we propose the development prospect of nanogeology in China. There are many geologic problems with scientific values and economic benefits, such as research of geologic fundamental problems, resource exploration and development, mechanism study and prediction of geological activities (disasters), mechanism research and management of environmental pollution and others. Nanogeology has a great potential in China to solve all of these problems. As a result, the theories and methods of nanogeology will become enriching and advanced. It offers important theoretical basis and technological methods to deal with major issues concerning the national economy and the people’s livelihoods, such as the prediction of geological activities, as well as resource distribution and its exploration and utilization.     

Surface fronts in estuaries: A review

Recent advances in the understanding of the physics of estuarine fronts (small-scale regions of significant changes in hydrographic variables) are reviewed. These fronts may be classified in three groups—tidal mixing fronts, plume fronts, and shear fronts—on the basis of the mechanism dominating the local rate of change in the horizontal density gradient. These classes are not independent, however, since it appears that both tidal mixing fronts and shear fronts can produce buoyancy-driven flow structures that propagate away from the generation region as plume fronts. Field observations of typical examples of each class are presented and laboratory experiments and theoretical models which isolate the important physical processes are summarized. Some important unresolved questions are identified and suggestions for further research are offered.     

Selenium in volcanic environments: A review

Selenium is a chemical element with major environmental implications, due to the extremely narrow range between essential and toxic concentrations. Volcanoes emit significant amounts of Se, which has an enormous impact on the Se cycle and potentially human and animal health. This paper presents a broad overview of the current state of knowledge of major aspects of volcanic derived Se, focussing on the processes in soils and aquifers.     

Quaternary buried paleosols: A critical review

A review of work on buried paleosols in the disciplines of pedology, Quaternary geology, and archaeology is presented under the headings of (1) the problems of identification, (2) techniques of study, (3) buried paleosols and Quaternary stratigraphy, (4) archaeological stratigraphy and dating, (5) layered soils, and (6) past environment from buried paleosols. It is suggested that future pedological research of interest to Quaternary studies should concentrate on clarifying what is a soil as opposed to a weathered sediment, what processes and features are peculiar to pedogenesis as opposed to diagenesis, and what are the relationships between soil-site conditions and soil characteristics.     

Isotopes in pyrogenic carbon: A review

Pyrogenic carbon (PC; also known as biochar, charcoal, black carbon and soot) derived from natural and anthropogenic burning plays a major, but poorly quantified, role in the global carbon cycle. Isotopes provide a fundamental fingerprint of the source of PC and a powerful tracer of interactions between PC and the environment. Radiocarbon and stable carbon isotope techniques have been widely applied to studies of PC in aerosols, soils, sediments and archaeological sequences, with the use of other isotopes currently less developed. This paper reviews the current state of knowledge regarding (i) techniques for isolating PC for isotope analysis and (ii) processes controlling the carbon (¹³C and ¹⁴C), nitrogen, oxygen, hydrogen and sulfur isotope composition of PC during formation and after deposition. It also reviews the current and potential future applications of isotope based studies to better understand the role of PC in the modern environment and to the development of records of past environmental change.     

Frost sorted patterned ground: A review

Sorted circles, polygons, and stripes are reported from Alaska, Greenland, Baffin Island, Antarctica, and New Hampshire. From these studies and key references, all cases are found to have: (1) a mixed parent material, commonly till, composed of a wide range of clast sizes unsorted below frost table, (2) gutter depressions containing the largest stones and carrying summer drainage, and (3) tabular stones on edge in the gutters showing expansion-squeezing from the sides. The size of the unit cells, gutter to gutter, is a function of mean maximum clast size: smallest chips making forms 10 cm diameter across and largest forms 20 m across. The slope determines the shape: polygons, and nets form on slopes up to 2 or 4° depending upon amount of water and fines. Ellipses form on 3 to 6° slopes, and stripes form on 4 to 11° slopes. Clearly shape is an effect of solifluction. Lastly, time involves seasons of sporadic sorting until there is a stable end form with lichen-covered stone gutters and tundra-covered soil centers. The up-and-out mechanism, described by Corté, is the best known for the primary sorting. Larger sorted forms (2–20 m in diameter) are reported almost exclusively where nearly continuous permafrost exists. They form where the mean annual temperature is below ? 4°C. Former permafrost is indicated where lichen and turf are dense and not overturned and where measured motion is nil. Small forms (under 1 m in diameter) are generated in a year or two where there is only deep annual freezing (0.1–2 m), but no permafrost.     

Emerald deposits and occurrences: A review

Emerald, the green gem variety of beryl, is the third most valuable gemstone (after diamond and ruby). Although it is difficult to obtain accurate statistics, Colombia supplies most (an estimated 60%, worth more than $500,000,000 per year) of the world's emeralds. However there is speculation that the emerald mines in Colombia are becoming depleted. Brazil currently accounts for approximately 10% of world emerald production. Emeralds have also been mined in Afghanistan, Australia, Austria, Bulgaria, China, India, Madagascar, Namibia, Nigeria, Pakistan, South Africa, Spain, Tanzania, the United States, and Zimbabwe.Because it is difficult to obtain accurate analyses of beryllium, most published analyses of beryl are renormalized on the basis of 18 oxygen and 3 Be atoms per formula unit. The color of emerald is due to trace amounts of chromium and/or vanadium replacing aluminum at the Y site; in most cases the Cr content is much greater than that of V. To achieve charge balance, the substitution of divalent cations at the Y site is coupled with the substitution of a monovalent cation for a vacancy at a channel site.Beryl is relatively rare because there is very little Be in the upper continental crust. Unusual geologic and geochemical conditions are required for Be and Cr and/or V to meet. In the classic model, Be-bearing pegmatites interact with Cr-bearing ultramafic or mafic rocks. However in the Colombian deposits there is no evidence of magmatic activity and it has been demonstrated that circulation processes within the host black shales were sufficient to form emerald. In addition, researchers are recognizing that regional metamorphism and tectonometamorphic processes such as shear zone formation may play a significant role in certain emerald deposits.A number of genetic classification schemes have been proposed for emerald deposits. Most are ambiguous when it comes to understanding the mechanisms and conditions that lead to the formation of an emerald deposit. Studies of individual emerald deposits show that in most cases a combination of mechanisms (magmatic, hydrothermal, and metamorphic) were needed to bring Be into contact with the chromophores. This suggests the need for a more flexible classification scheme based on mode of formation. Stable isotopes can be used to estimate the contribution of each mechanism in the formation of a particular deposit. Such estimates could perhaps be more precisely defined using trace element data, which should reflect the mode of formation.Emerald may be identified in the field by color, hardness, and form. It will tend to show up in stream sediment samples but because its specific gravity is relatively low, it will not concentrate in the heavy mineral fraction. In Colombia, structural geology, the sodium content of stream sediment samples, and the lithium, sodium, and lead contents of soil samples have all been used to find emerald occurrences. Exploration for gem beryl could result in the discovery of new occurrences of non-gem beryl or other Be minerals that could become new sources of Be and Be oxide.Future efforts should go towards creating a comprehensive data base of emerald compositions (including trace elements), determination of the role of metamorphism in the formation of some emerald deposits, improved classification schemes, and more effective exploration guidelines.     

BIF-hosted iron mineral system: A review

The BIF-hosted iron ore system represents the world's largest and highest grade iron ore districts and deposits. BIF, the precursor to low- and high-grade BIF hosted iron ore, consists of Archean and Paleoproterozoic Algoma-type BIF (e.g., Serra Norte iron ore district in the Carajás Mineral Province), Proterozoic Lake Superior-type BIF (e.g., deposits in the Hamersley Province and craton), and Neoproterozoic Rapitan-type BIF (e.g., the Urucum iron ore district).The BIF-hosted iron ore system is structurally controlled, mostly via km-scale normal and strike-slips fault systems, which allow large volumes of ascending and descending hydrothermal fluids to circulate during Archean or Proterozoic deformation or early extensional events. Structures are also (passively) accessed via downward flowing supergene fluids during Cenozoic times.At the depositional site the transformation of BIF to low- and high-grade iron ore is controlled by: (1) structural permeability, (2) hypogene alteration caused by ascending deep fluids (largely magmatic or basinal brines), and descending ancient meteoric water, and (3) supergene enrichment via weathering processes. Hematite- and magnetite-based iron ores include a combination of microplaty hematite–martite, microplaty hematite with little or no goethite, martite–goethite, granoblastic hematite, specular hematite and magnetite, magnetite–martite, magnetite-specular hematite and magnetite–amphibole, respectively. Goethite ores with variable amounts of hematite and magnetite are mainly encountered in the weathering zone.In most large deposits, three major hypogene and one supergene ore stages are observed: (1) silica leaching and formation of magnetite and locally carbonate, (2) oxidation of magnetite to hematite (martitisation), further dissolution of quartz and formation of carbonate, (3) further martitisation, replacement of Fe silicates by hematite, new microplaty hematite and specular hematite formation and dissolution of carbonates, and (4) replacement of magnetite and any remaining carbonate by goethite and magnetite and formation of fibrous quartz and clay minerals.Hypogene alteration of BIF and surrounding country rocks is characterised by: (1) changes in the oxide mineralogy and textures, (2) development of distinct vertical and lateral distal, intermediate and proximal alteration zones defined by distinct oxide–silicate–carbonate assemblages, and (3) mass negative reactions such as de-silicification and de-carbonatisation, which significantly increase the porosity of high-grade iron ore, or lead to volume reduction by textural collapse or layer-compaction. Supergene alteration, up to depths of 200 m, is characterised by leaching of hypogene silica and carbonates, and dissolution precipitation of the iron oxyhydroxides.Carbonates in ore stages 2 and 3 are sourced from external fluids with respect to BIF. In the case of basin-related deposits, carbon is interpreted to be derived from deposits underlying carbonate sequences, whereas in the case of greenstone belt deposits carbonate is interpreted to be of magmatic origin. There is only limited mass balance analyses conducted, but those provide evidence for variable mobilization of Fe and depletion of SiO₂. In the high-grade ore zone a volume reduction of up to 25% is observed.Mass balance calculations for proximal alteration zones in mafic wall rocks relative to least altered examples at Beebyn display enrichment in LOI, F, MgO, Ni, Fe₂O_3total, C, Zn, Cr and P₂O₅ and depletions of CaO, S, K₂O, Rb, Ba, Sr and Na₂O. The Y/Ho and Sm/Yb ratios of mineralised BIF at Windarling and Koolyanobbing reflect distinct carbonate generations derived from substantial fluid–rock reactions between hydrothermal fluids and igneous country rocks, and a chemical carbonate-inheritance preserved in supergene goethite.Hypogene and supergene fluids are paramount for the formation of high-grade BIF-hosted iron ore because of the enormous amount of: (1) warm (100–200 °C) silica-undersaturated alkaline fluids necessary to dissolve quartz in BIF, (2) oxidized fluids that cause the oxidation of magnetite to hematite, (3) weakly acid (with moderate CO₂ content) to alkaline fluids that are necessary to form widespread metasomatic carbonate, (4) carbonate-undersaturated fluids that dissolve the diagenetic and metasomatic carbonates, and (5) oxidized fluids to form hematite species in the hypogene- and supergene-enriched zone and hydroxides in the supergene zone.Four discrete end-member models for Archean and Proterozoic hypogene and supergene-only BIF hosted iron ore are proposed: (1) granite–greenstone belt hosted, strike-slip fault zone controlled Carajás-type model, sourced by early magmatic (± metamorphic) fluids and ancient “warm” meteoric water; (2) sedimentary basin, normal fault zone controlled Hamersley-type model, sourced by early basinal (± evaporitic) brines and ancient “warm” meteoric water. A variation of the latter is the metamorphosed basin model, where BIF (ore) is significantly metamorphosed and deformed during distinct orogenic events (e.g., deposits in the Quadrilátero Ferrífero and Simandou Range). It is during the orogenic event that the upgrade of BIF to medium- and high-grade hypogene iron took place; (3) sedimentary basin hosted, early graben structure controlled Urucum-type model, where glaciomarine BIF and subsequent diagenesis to very low-grade metamorphism is responsible for variable gangue leaching and hematite mineralisation. All of these hypogene iron ore models do not preclude a stage of supergene modification, including iron hydroxide mineralisation, phosphorous, and additional gangue leaching during substantial weathering in ancient or Recent times; and (4) supergene enriched BIF Capanema-type model, which comprises goethitic iron ore deposits with no evidence for deep hypogene roots. A variation of this model is ancient supergene iron ores of the Sishen-type, where blocks of BIF slumped into underlying karstic carbonate units and subsequently experienced Fe upgrade during deep lateritic weathering.     

Isotopes in pyrogenic carbon: A review

Pyrogenic carbon (PC; also known as biochar, charcoal, black carbon and soot) derived from natural and anthropogenic burning plays a major, but poorly quantified, role in the global carbon cycle. Isotopes provide a fundamental fingerprint of the source of PC and a powerful tracer of interactions between PC and the environment. Radiocarbon and stable carbon isotope techniques have been widely applied to studies of PC in aerosols, soils, sediments and archaeological sequences, with the use of other isotopes currently less developed. This paper reviews the current state of knowledge regarding (i) techniques for isolating PC for isotope analysis and (ii) processes controlling the carbon (¹³C and ¹⁴C), nitrogen, oxygen, hydrogen and sulfur isotope composition of PC during formation and after deposition. It also reviews the current and potential future applications of isotope based studies to better understand the role of PC in the modern environment and to the development of records of past environmental change.     

滩坝沉积研究进展综述

滩坝是发育于滨岸带非常重要的一种沉积相类型和油气储集体,是滩和坝的总称。国外关于滩坝的研究,多集中于对现代沉积与野外露头的考察,侧重于成因机理的解释;中国的沉积学家、石油地质学家则偏重于陆相湖盆滩坝的沉积特征与油气地质意义的研究。作者从滩坝的成因出发,对滩坝的分类、沉积模式、控制因素、古地理及油气意义进行了总结梳理,提出滩坝是“风(风浪)-源(物源)-盆(盆地演化)”系统内综合作用下的产物,表现在:波浪是滩坝形成的动力;物源是滩坝形成的物质基础;盆地层序-构造演化过程中古地貌与古水深决定了滩坝的发育位置与范围。研究滩坝发育的控制因素,有利于为其在垂向上和平面上的分布预测提供有力的支持,具有重要的油气勘探意义。滩坝砂体记录了其形成时的古地理条件。特别地,通过对滩坝砂体沉积特征的解剖,可以一定程度上定量反映其形成时的古风浪条件,进而可以恢复古大气流场,这对古气候的恢复起到了重要的补充作用。     

Diagenesis in carbonate sediments: A review

Reading the old textbooks of more than twenty-five years ago reveals the enormous progress made in our understanding since those days. Advances have been made along several related paths, particularly through the study of texture and structure with the microscope, the examination of Recent marine sediments and the application of the principles of solution chemistry. As a result we can now relate many diagenetic products with distinctive textures or structures to one of, say, four main types of aqueous solution. Sea water yields characteristic growths of aragonite and Mg-calcite whose fossilized calcitic remains we can yet recognise in the ancient. Fresh water gives rise to other individual calcite textures whose imprint also we can distinguish in the old rocks. Solution extruded at depth from compacting clays produce even other calcite textures which we are now beginning to understand. Certain mixtures of sea water with fresh water provide not only beach rocks with aragonite and Mg-calcite cements but dolomites through the Dorag process. Clearly influential in the control of marine precipitation we find organic compounds such as the humic acids.Superimposed on these products are the results of pressure solution. Clues to the action of processes in the distant past remain in the form of traces of magnesium, strontium or uranium and of relic isotopic ratios of oxygen and carbon, indicators of the composition of long vanished solutions. We think more clearly that before about rates of processes, duration of exposure to diagenetic environments, the balance between relatively closed and open chemical systems, the movements and mixing of ground waters and their chemical changes. In these and other ways carbonate diagenesis has come of age.

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Zusammenfassung Liest man alte Lehrbücher, die vor mehr als 25 Jahren erschienen sind, so erkennt man, welcher Fortschritt auf dem Gebiet der Karbonatdiagenese seither zu verzeichnen ist. Diese Fortschritte sind auf verschiedenen benachbarten Wegen erreicht worden, speziell durch Gefügeuntersuchungen mit dem Mikroskop, durch das Studium rezenter mariner Sedimente und durch die Anwendung der Prinzipien der Elementreaktionen in Lösungen. Als Ergebnis können wir heute viele diagenetische Stadien mit bestimmten Gefügemerkmalen und in erster Annäherung mit 4 Lösungsmilieus in Verbindung bringen. Meereswasser bewirkt typisches Wachstum von Aragonit und Hoch-Mg-Calcit, die wir in den fossilen calcitischen Gefügen wiedererkennen können. Süßwasser bewirkt auf der anderen Seite ein typisches Calcitwachstum, das wir ebenfalls in alten Gesteinen wiederfinden können. Lösungen, die aus kompaktierenden tonhaltigen Sedimenten aufsteigen, erzeugen calcitische Zementationsgefüge, die wir heute zu verstehen gelernt haben. Eine Mischung von Meereswasser und Süßwasser ist nicht nur für die beach-rock Zementation mit Aragonit und Hoch-Mg-Calcit verantwortlich, sie bewirkt auch Dolomitisierung nach dem Dorag-Modell.Organische Komponenten wie etwa Huminsäuren haben einen deutlichen Einfluß auf die Diageneseprozesse unter marinen Bedingungen. Den Diageneseprodukten werden schließlich die Einwirkungen der Drucklösung überlagert. Als Schlüssel zum Ablauf der Diagenese vergangener Zeiten verbleiben Spurenelemente wie Magnesium, Strontium und Uran sowie das reliktische Isotopenverhältnis von Sauerstoff und Kohlenstoff erhalten; sie markieren die Zusammensetzung längst vergangener Lösungen. Wir können heute besser die Anteile verschiedener Diageneseprozesse, die Dauer der Wirkung bestimmter Prozesse, den Ausgleich zwischen geschlossenen und offenen chemischen Systemen, die Bewegungen und Mischungen sowie chemischen Veränderungen des Grundwassers abschätzen.

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Résumé Parmi les vieux manuels agés de vingt-cinq ans ou davantage, on est frappé d'un coup d'il du progrès réalisé, surtout par l'étude des textures et des structures au microscope, par l'examen des sédiments marins actuels et par l'application de la chimie aqeuse. Conséquement on peut aujourd'hui lier les produits diagénétiques avec quatre solutions principaux. L'eau de mer donne les accroissements typiques en aragonite et en calcite-hautement magnésienne, reconnaisables aux calcaires anciens. L'eau douce fait surgir des textures individuelles en calcite. Aux profondeurs plus grands, les solutions exprimées des argiles y peuvent encore provoquer d'autres textures en calcite. L'eau de mer et l'eau douce, melées ensembles, y donnent naissance aux beach-rocks et aux dolomies. Franchement influents, aux précipitations marines, sont les composés organiques. Tout peut Être subi de la pression-solution. Données de la diagenèse ancienne restent telles que les traces du magnésium, du strontium et de l'uranium et des niveaux en ¹⁸O et ¹³C, témoins des compositions des solutions depuis longtemps disparues. On pense plus clairement qu'autrefois des taux des processus, des durées d'exposition aux milieux diagénétiques, du bilan entre les systèmes relativement fermés ou ouverts, des mouvements et des mélanges des eaux sousterraines et de leures changements chimiques. Dans telles mesures, l'étude de la diagenèse carbonatée a atteint sa majorité.

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Peritidal carbonate facies models: A review

Existing facies models for peritidal carbonates are limited in number and do not reflect the wide spectrum of possible types. The major depositional processes in peritidal carbonate environments are reviewed in order to stress the complex nature of the systems. The tidal channel model is critically discussed and it is suggested that channel deposits may be of minor importance in typical shoaling-up sequences. The possible causes of multiple asymmetrical sequences are reviewed.     

锌稳定同位素地球化学综述

锌是生物生命必需的微量元素和与人类活动息息相关的金属元素。随着样品纯化技术的提高和新一代质谱仪的开发应用,锌同位素体系已成为近年发展起来的金属(非传统)稳定同位素地球化学的一个热点领域,得到国内外学者的广泛研究。对最新的锌稳定同位素研究结果进行了系统总结,分别从分析方法、分馏理论、储库同位素组成以及应用等方面进行了论述。锌同位素已被广泛应用到天体化学、海洋、大气以及地球深部等诸多地球科学研究领域,大大提高人们对全球锌及其他重金属元素生物地球化学循环的认识。锌同位素在宇宙化学、环境地球化学、古气候环境重建以及健康及生物医学领域将具有非常大的应用前景。     

Tectonic slides: A review and reappraisal

Tectonic slides are faults that have been described and discussed in the Caledonides for over fifty years but which, possibly because of misunderstanding, have failed to find acceptance in structural schemes elsewhere. A review of the literature suggests, nevertheless, that they are a distinct class of fault common in certain terrains. Unlike the usual ‘brittle’ faults, slides occur in metamorphic conditions as an integral part of the more widespread fabric producing regional deformation that characterises metamorphic—orogenic belts. Because of their formation in such ‘ductile’ environments, slides are broadly concordant structures which are rarely associated with cataclasis. Since they also often lie along lithological contacts, they may be very difficult to detect at outcrop — despite the large displacements that may have taken place. Slides however may be recognised by (a) tectonic schist, and (b) their typical occurrence in planar zones of intensified regional deformation. They are often associated with major folds: either occurring in individual fold limbs or else cutting across the axial planes of fold pairs or groups of folds. Alternatively they may be unrelated to folds and may occur at simple lithological junctions or else separate rocks of widely different orogenic history, i.e. at tectonic fronts. Strain studies suggest that lithological contacts are important in initiating slides because of the different response of contrasting rock types to high strains.