热液矿床矿物微形貌与晶体生长环境研究

应用高分辨率扫描隧道显微镜(STM)和场效应扫描电镜(FEG SEM),对取自山西义兴寨金矿等4处热液矿床的黄铁矿、方铅矿、赤铁矿等矿物的表面生长微形貌进行了观察研究,并与实验合成的黄铁矿、方铅矿等矿物的微形貌特征进行对比。发现了自然矿物结晶三维成核成因的黄铁矿微球状晶,在合成和自然矿物的晶面观察到漏斗状晶和胞状结构等生长形貌。合成黄铁矿表面发育平整光滑的生长台阶,反映静态无扰动、接近平衡的晶体生长环境;而大量产于热液矿床的黄铁矿、方铅矿等晶体普遍发育胞状或拉长的胞状结构表面,并总体呈台阶状排列的表面结构,证明自然成矿热液体系的高过饱和度和流动生长环境。研究表明,热液成矿过程中矿物结晶作用有从成核、台阶状晶体生长、到形成“平衡”多面体生长的一个演化过程;形成于复杂条件的矿物晶体表面微观结构,包含丰富的成矿环境信息。     

Glacial activity and paraglacial landsliding in the Devensian Lateglacial: evidence from Craig Cerrig-gleisiad and Fan Dringarth,Fforest Fawr (Brecon Beacons), South Wales

The tongue-shaped mass of debris and associated ridges on the cirque floor below Craig Cerrig-gleisiad, Brecon Beacons National Park is important and controversial because it has been attributed to more than one glacier advance during the Late Devensian. A new origin is proposed involving landslide development from the collapse of part of the western headwall followed by a single phase of glacier development in the Loch Lomond Stadial (Younger Dryas), which reworked the landslide sediments. Evidence for this landslide, which provides useful criteria for differentiating moraines formed by small glaciers from landslides, lies in tension cracks, backward-tilted blocks and bedrock joints dipping out of the western headwall, together with lateral levées, upstanding termini and angular clasts with only occasional, indistinct striae on the tongue-shaped mass, which is interpreted as a flowslide. Glacier reworking of debris in the upper part of the Cwm Cerrig-gleisiad landslide is indicated by subparallel ridges rising to 20 m above the cirque floor containing abraded clasts (16-32% striated). This interpretation is supported by a comparison with the morphological and sedimentary characteristics of a neighbouring landslide at Fan Dringarth, where no glacier developed in the Loch Lomond Stadial. The existence of paraglacial landsliding has significant palaeoenvironmental implications leading to: (1) erroneously large estimates of equilibrium line depression ($Δ$ELA) in the Loch Lomond Stadial; (2) consequent underestimates of summer palaeotemperatures and/or overestimates of the contribution of wind-drifted snow to glacier accumulation; and (3) larger moraines than usual and overestimation of the efficacy of glacial erosion because of antecedent processes.     

Evolution of a periglacial landscape in the Late Devensian: environments and palaeobotany of the Mepal area,Cambridgeshire, England

The landscape evolution of the Mepal area from Late Devensian Block Fen Terrace times to the beginning of the Flandrian, a period of ca. 8000 radiocarbon years, is reconstructed. Stratigraphy is based on borehole transects and single boreholes, centred on a depression between the Block Fen Terrace and the Isle of Ely. Within the depression is a Devensian late‐glacial sequence, with the Windermere Interstadial represented by radiocarbon‐dated organic sediments. Pollen and plant macroscopic remains of the late‐glacial sediments are analysed. Plant communities with Betula developed in the interstadial. Before and after the interstadial there is much reworked pollen in the inorganic sediments, derived from local pre‐Devensian Pleistocene sediments, including temperate Ipswichian Stage sediments, and from mass‐wasting of the local Jurassic bedrock. Periods of such mass‐movement occur before and after the deposition of the late‐glacial lake sediments. Deposition of aeolian sediment occurs later than the main period of mass movement, but before the Windermere Interstadial. The relationship of the aeolian sediments in time and space to permafrost, indicated by local contraction polygons and cracks, is discussed. Solifluction diverted the flow of the River Great Ouse from a northeast direction in Block Fen Terrace times to a southwest direction as a channel developed to the west of the Chatteris–March ‘island’. This led to a drainage divide in Flandrian times. Copyright © 2002 John Wiley & Sons, Ltd.     

Determining the origin of soft‐sediment deformation structures: a case study from Upper Carboniferous delta deposits in south‐west Wales,UK

Determining the cause of sediment mobilization is a major problem; possible triggers include earthquakes, sediment loading and wave action. A detailed sedimentological and palaeoenvironmental analysis of soft‐sediment deformation in Upper Carboniferous deltaic deposits in SW Wales, UK, shows that two styles of deformation occur. Type A (syndepositional convolute stratification) affects most sandstone beds and was generated by rapid sedimentation. Type B (localized sand‐in‐sand pseudonodules) incorporates beds that already contained Type A deformation, and developed when the substrate was liquefied by disturbance due to movement on a near‐surface gravity slide. Neither type of deformation was triggered by seismic events.     

Terrestrial and freshwater carbonates in Hoxnian interglacial deposits, UK: micromorphology, stable isotopic composition and palaeoenvironmental significance

MIS 11 is often considered to be the best climatic analogue for the Holocene. Many studies have suggested, however, that it is a period of extreme climate warmth comparable in temperatures to the Middle and Late Pliocene. In Britain deposits of the Hoxnian interglacial are correlated to MIS 11 and multi-proxy techniques can be used to reconstruct the climate of this interglacial. Soil, groundwater and freshwater carbonates are common in Hoxnian deposits and the stable isotopic composition of these precipitates can be used to increase our understanding of MIS 11 environments in Britain. Carbonates from Marks Tey, Clacton, Swanscombe, Elveden and West Stow are studied, the stratigraphic context of which indicates that their formation is broadly synchronous (in the mid-Hoxnian, pollen zones Ho II to Ho III). The carbon isotopic composition of groundwater and pedogenic carbonates is typically depleted with respect to δ¹³C (ca −9 to −8‰ VPDB) reflecting uptake of plant respired CO₂ during water migration/recharge. The carbon isotopic composition of lacustrine carbonate is more enriched with respect to δ¹³C (ca 0-1‰VPDB) reflecting the equilibration of lake waters with atmospheric CO₂. The δ¹⁸O of groundwater and pedogenic carbonates is slightly more enriched than modern soil carbonates but not as enriched as soil carbonates formed under interglacials that were warmer than the Holocene (i.e. the Cromerian). The stable isotopic composition of Hoxnian carbonates does not, therefore, indicate that this interglacial was characterised by uniquely warm climates in the context of other Middle Pleistocene interglacials and the Holocene. This is contrary to many marine and littoral records from around the world but consistent with environmental records from Britain and Europe.     

The sedimentology,stratigraphy and 14C dating of a turf‐banked solifluction lobe: evidence for Holocene slope instability at Okstindan,northern Norway

The stratigraphy of a trench excavated through a solifluction lobe lying at an altitude of 860 m a.s.l. on the eastern flank of the Okstindan mountains is described. Sedimentological evidence suggests that the movement was probably dominated by a flow process, with silty sands episodically bursting‐out through a thinly vegetated lobe front in the spring and early summer thaw phases, when pore‐water pressures were likely to be increased. A continuous buried soil extends for some 14 m. Fourteen new radiocarbon age estimates from thin‐slice samples of this buried soil and organic fractions derived from laboratory pre‐treatment procedures are discussed. These data indicate that the solifluction probably commenced in the mid‐Holocene and continued throughout the Neoglacial. The slope instability may be correlated tentatively with the record of glacial variations, shifts in tree lines and archaeological evidence, supporting a link with regional climatic deterioration. Copyright © 1999 John Wiley & Sons, Ltd.     

Alluvial fan and wetland interactions: evidence of seasonal slope wetlands from the Silurian of south central Wales,UK

Distal environs of the Ludlow‐age Trichrug Formation from south central Wales (UK) detail deposition on the outer fringe of an ephemeral debris flow‐dominated alluvial fan. Debrites and subordinate sheetflood deposits are interbedded with sporadic thin sandstone‐dominated heterolithic units deposited in shallow, ephemeral ponds in the axial valley. The latter slope wetland system fringed the permeable alluvial fan deposits, being maintained by streamflow, precipitation and ground water recharge. A prolonged high water table is indicated by low chroma intervals interpreted as the result of gleying. A variety of redoximorphic indicators, including colour mottling and ferricrete concretions, are evidence of iron mobilization and concentration associated with a seasonally fluctuating water table. The slope wetlands were colonized periodically by Skolithos‐generating organisms, most likely to have been arthropods. The widespread occurrence of redoximorphic indicators and ferricrete contrasts markedly with calcrete Vertisols in penecontemporaneous continental deposits (Lower Old Red Sandstone) of the region. It is likely that the alluvial fan‐toe area was the site of a wetland depression, which maintained a high, though fluctuating, water table. In contrast the alluvial channel reaches of the surrounding drainage network were significantly better drained, with floodplains prone to wetting and drying and Vertisol palaeopedogenesis.     

Early Devensian sediments and palaeovenvironmental evidence from the excavations at the Royal Oak Portal Paddington,West London,UK

This paper discusses the results of the investigation of Pleistocene sediments at the Royal Oak Portal (ROP) site on the new Crossrail scheme near Paddington Station, London. The site was sampled and recorded in May 2011 by archaeologists from Oxford Archaeology commissioned by Crossrail Ltd. The investigation revealed a sedimentary sequence associated with cool climate waterlain deposition towards the edge of the River Westbourne floodplain. During excavation an assemblage of around 100 identifiable large mammal bones was recovered, dating to the Late Pleistocene. The major concentration of bones, from bison and reindeer, was located and excavated from a shallow sequence of sediments. Analysis of the bones indicates that they represent a natural death assemblage, scavenged and subsequently disarticulated, transported by water, exposed and further dispersed and broken by trampling. The site is of regional and national importance because the assemblage derives from a well-constrained geological context, with associated dating evidence suggesting accumulation during the later parts of Marine Isotope Stage (MIS) 5 and continuing within MIS 4. The site is also of significance because it is one of a growing number of recently discovered sites away from the main fluvial archive for the British Middle and Upper Pleistocene. These sites have the potential to add significantly to our understanding of parts of the Pleistocene record that remain difficult to document through the investigation of the more active systems associated with major rivers such as the Thames, Severn or Trent.     

北方泥炭沼泽中酚类物质释放的热敏感性研究:以英国威尔士地区雨养和矿养泥炭沼泽为例

利用高精度多梯度热培养系统,对英国威尔士地区两类典型的北方泥炭沼泽中酚类物质和溶解有机碳释放的热敏感性进行了为期1年的调查研究.研究结果表明,雨养泥炭沼泽(Bog)酚类物质释放的热敏感性Q10(总酚)月变化为0.92～1.57,而矿养泥炭沼泽(Fen)的月变化范围为0.93～1.30.酚类释放的热敏感性与土壤温度大致呈正相关关系.此外,土壤温度与溶解有机碳释放的热敏感性Q10(DOC)也呈正相关关系.总体上,雨养泥炭沼泽的热敏感性比矿养泥炭沼泽略高.除温度外,水文条件和植被等多种环境因子对酚类物质和溶解有机碳释放的热敏感性也有较大影响.研究结果还表明酚碳热敏感性比值Q10o(总酚)/Q10(DOC)相对稳定,土壤温度的变化对其影响有限.     

Comparison of tropical,carbonate and temperate,siliciclastic tidally dominated sedimentary deposits: Examples from the Australian continental shelf

Surficial deposits of the tidally influenced Australian shelf seas exhibit a variation in fades related to energy gradient. These deposits comprise a high energy gravelly facies, a mobile sand sheet facies and a low energy muddy sand facies. Such a facies distribution conforms generally with the existing model of continental shelf tidal sedimentation, derived for the west European tidal seas. However, the carbonate rich and mainly warm water deposits of the Australian shelf differ from the mainly quartzose and temperate cold‐water deposits of the European type case in terms of: (i) the role of seagrasses in trapping fine‐grained sediment; and (ii) the relative importance of the production of carbonate mud by mechanical erosion of carbonate grains. Seagrasses in Spencer Gulf, Gulf of St Vincent and Torres Strait are located in regions of strong tidal currents, associated with bedforms and gravel lag deposits. Thus, in the case of tropical carbonate shelves, seagrass deposits containing fine‐grained and poorly sorted sediments are located in close proximity to high energy gravel and mobile sand facies. In contrast, the European model (for temperate, siliciclastic shelves) places facies in a regional gradient with a wide separation (in the order of 50–100 km).

Of the locations reviewed, the Gulf of St Vincent, Bass Strait, southern Great Barrier Reef, Torres Strait and Gulf of Carpentaria exhibit zones of carbonate mud accumulation. The production and winnowing of carbonate mud from the mobile sand facies is a factor that must be taken into account in the assessment of a sediment budget for this facies, and which is of relatively greater importance for carbonate shelves. Insufficient data are presently available from the macrotidal North West Shelf to test the applicability of the model to this region.     

西昆仑帕米尔式铁矿床膏铁建造成因探讨——以老并铁矿为例

产于塔什库尔干陆块下古生界含铁岩系的西昆仑帕米尔式铁矿床具有独特的膏铁建造特征。老并矿区具有明显的6个沉积铁矿化层,由下往上构成"粗碎屑岩-中基性火山岩夹层-磁铁矿层-含铁膏岩层-细碎屑岩"退积正粒序组合的沉积层,与火山活动关系密切,成矿物质主要来源于火山物质。在海底火山喷发过程中,深部火山岩浆与海水硫酸盐矿物发生混染作用,含铁热水溶液与膏岩层作用。随着温度、压力、pH值等环境条件的转变,先后结晶出硬石膏、磁铁矿、黄铁矿并沉积形成不同矿物组合的膏铁建造。     

Flow transformations in slumps: a case study from the Waitemata Basin,New Zealand

The process by which slumps transform into other flow types is an understudied phenomenon; generally, sedimentologists have assumed that this is how many debris flows and turbidity currents form, yet there is a paucity of information relating to the specific processes involved. This paper aims to redress this imbalance and investigates the processes of slump flow transformation using a well‐exposed example, where the precursor slump and flows to which it was transforming have been preserved in the outcrop. A detailed field investigation of the Lower Miocene, Little Manly Slump, located within the Waitemata Basin, New Zealand, reveals a complex bi‐partite deposit, comprised of a lower slump‐debrite unit and an upper turbidite unit, separated from one another by an impersistent contact. Reconstruction of slump evolution, from preserved strain indicators, shows that slump motion was unsteady and non‐uniform, and that the slump arrested rapidly. Flow transformation is directly linked to slump evolution and progressed through the multiple processes of body transformation, fluidization transformation and surface transformation. The resultant flow comprised a very dense lower unit with slump and debris flow phases overlain by a turbidity current. This study shows that flow transformation did not result in en masse transformation to a debris flow by a single process, but rather it was characterized by partial transformation of the slump to generate a three‐phase flow. Density is thought to be the key parameter in controlling flow transformation efficiency, which appears to have varied rapidly as a function of slump unsteadiness and non‐uniformity.     

The internationalisation of banking,technological change and spatial patterns: a case study in South Wales

This paper analyses the growth of international banking in the post-war era and theorises on this phenonemon. It also traces the growth of banking in the U.K. before reviewing recent technological change within the industry. Spatial patterns of banking activities in the U.K. are reviewed with reference to the aforementioned trends, focussing on a case study of a major relocation of a bank to South Wales and comparing this with other international studies.     

The role of slump scars in slope channel initiation: A case study from the Miocene Jatiluhur Formation in the Bogor Trough,West Java

This paper investigates slope channel initiation by seabed irregularities that were initially formed by slump scars in the lower to middle Jatiluhur Formation, part of the middle- to late Miocene successions in the Bogor Trough, West Java. This Miocene succession is up to 1000 m thick in the study area, and is interpreted as a prograding slope–shelf system that formed during a period of falling- and lowstand stages in relative sea level. The lower part of the formation is a siltstone-dominated siliciclastic succession, containing slump deposits, slump-scar-fill deposits, and minor channel-fill deposits, which formed in slope and shelf-margin environments. In contrast, the middle part, which gradationally overlies the lower part, is characterized by shallow-marine carbonates.The slump-scars-fill deposits have an overall lenticular geometry, and are 140–480 m wide and 0.4–1.6 m thick. Some have distinct erosional bases, which cut into the underlying siltstones, in association with medium- to coarse-grained sandstones with lateral-accretion surfaces and tractional structures common in channel-fill deposits. The incident link of slump-scar-fill deposits and channel-fill deposits in the prograding slope–shelf succession of the lower to middle Jatiluhur Formation suggests that some slump scars formed incipient seabed irregularities that may have played an important role in the development of slope channels. The present study provides one example of the various potential mechanisms that can result in channel formation in a slope setting.     

河谷斜坡带泥灰质岩石区地貌对岩溶的控制机理--以三峡地区为例

研究泥灰质岩石区地貌对岩溶的控制机理是弄清岩溶过程的出发点.三峡河谷斜坡带泥灰质岩石区地貌对岩溶具有明显的控制作用.纵向上在陡坡地带和地形由陡变缓的转折部位岩溶作用强烈,纵比降小的山梁部位岩溶作用较弱;横向上冲沟部位岩溶作用最强,坡肩部位岩溶作用较弱,山梁部位岩溶作用又增强.哪里的岩溶通道发育、水流汇集量大,哪里的岩溶就强烈.在三峡移民迁建中,应注意不同的地貌部位具有不同的地基变形破坏型式.     

Lateglacial and Holocene climate and soil erosion in southeastern France: A case study from Etang du Pourra,Provence

A synthesis of pollen evidence from Etang du Pourra, a small pond in Rhodanian Provence, France, complemented by new sedimentological, mineralogical and palynological data allow a reassessment of the Lateglacial-Holocene vegetation and climatic history of the area. The Etang du Pourra succession is shown to consist of two parts; the lower part dates from the Lateglacial and the upper reveals the Holocene pollen-stratigraphic succession typical of the region. In the Lateglacial, a humid and cooler phase is recorded before the Younger Dryas conditions progressively set in. In the Holocene succession, the consequences of human modifications on the environment are clearly visible in changes in mineralogy and pollen stratigraphy.     

HPHT reservoir evolution: a case study from Jade and Judy fields, Central Graben, UK North Sea

3D basin modelling of a study area in Quadrant 30, UK North Sea was performed in order to elucidate the burial, thermal, pressure and hydrocarbon generation, migration and accumulation history in the Jurassic and Triassic high pressure–high temperature sequences. Calibration data, including reservoir temperatures, pressures, petroleum compositional data, vitrinite reflectance profiles and published fluid inclusion data were used to constrain model predictions. The comparison of different pressure generating processes indicated that only when gas generation is taken into account as a pressure generating mechanism, both the predicted present day as well as palaeo-pressure evolution matches the available calibration data. Compositional modelling of hydrocarbon generation, migration and accumulation also reproduced present and palaeo bulk fluid properties such as the reservoir fluid gas to oil ratios. The reconstruction of the filling histories of both reservoirs indicates that both were first charged around 100 Ma ago and contained initially a two-phase system in which gas dominated volumetrically. Upon burial reservoir fluid composition evolved to higher GORs and became undersaturated as a function of increasing pore pressure up to the present day situation. Our results indicate that gas compositions must be taken into account when calculating the volumetric effect of gas generation on overpressure.     

Internal architecture of mass‐transport deposits in basinal carbonates: A case study from southern Italy

Submarine mass‐transport deposits represent important stratigraphic heterogeneities within slope and basinal sedimentary successions. A poor understanding of how their distribution and internal architecture affect the fluid flow migration pathway may lead to unexpected compartmentalization issues in reservoir analysis. Studies of modern carbonate mass‐transport deposits mainly focus on large seismic‐scale slope failures; however, the near‐platform basinal depositional environment often hosts mass‐transport deposits of various dimensions. The small‐scale and meso‐scale (metres to several tens of metres) carbonate mass‐transport deposits play a considerable role in distribution of sediment and therefore have an impact on the heterogeneity of the succession. In order to further constrain the geometry and internal architecture of mass‐transport deposits developed in near‐slope basinal carbonates, a structural and sedimentological analysis of sub‐seismic‐scale mass‐transport deposits has been undertaken on the eastern margin of the Apulian carbonate platform in the Gargano Promontory, south‐east Italy. These mass‐transport deposits, that locally comprise a large proportion (50 to 60%) of the base of slope to basinal sediments of the Cretaceous Maiolica Formation, typically display a vertically bipartite character, including debrites and slump deposits of varying volume ratios. A range of brittle and ductile deformation styles developed within distinct bed packages, together with the presence of both chert clasts, folded chert layers and spherical chert nodules, suggest that sediments were at different stages of lithification prior to downslope movement associated with mass‐transport deposits. This study helps elucidate the emplacement processes, frequency and character of subseismic‐scale mass‐transport deposits within the basinal carbonate environment, and thereby reduces the uncertainties in the characterization of subsurface carbonate geofluid reservoirs.     

Simultaneous thin section and phytolith observations of finely stratified deposits from Neolithic Çatalhöyük,Turkey: implications for paleoeconomy and Early Holocene paleoenvironment

Simultaneous thin section and phytolith observations of finely stratified anthropogenic deposits from the Neolithic settlement of Çatalhöyük, Turkey, dated between 7400 and 6000 BC provide evidence for both the depositional context and phytolith assemblage of these deposits. Although extracted phytoliths provide a general picture of vegetation that supports existing evidence of a local wet marshland environment, comparisons with observations of phytoliths in situ indicate a diverse range of microcontexts, as well as depositional and post‐depositional processes that influence phytolith size. This has implications for studies that use conjoined phytolith size as a proxy for water availability and early agricultural practices. Observations indicate a significant background noise of phytoliths and micro‐charcoal in the deposits, linked to the frequent use of fire, which has implications for interpreting assemblages where phytolith counts are low, such as from floors of buildings. This study confirms the usefulness of phytoliths in providing information on human plant use and environment where the taphonomy of the deposits is clear, and provides new evidence for wet farming of at least some of the wheat found at the site. It also suggests there needs to be greater consideration of phytolith taphonomy, which can be provided to an extent by combining phytolith analysis with thin section micromorphology. Copyright © 2011 John Wiley & Sons, Ltd.     

Interaction between groundwater, the hyporheic zone and a Chalk stream: a case study from the River Lambourn, UK

Understanding the processes controlling groundwater/surface-water interaction is essential for effective resource management and for protecting sensitive ecosystems. Through intensive monitoring of Chalk groundwater, shallow gravel groundwater and surface water in the River Lambourn, UK, using a combination of hydrochemical and hydrophysical techniques, a complex pattern of interactions has been elucidated. The river is broadly in hydraulic contact with the streambed sediments and adjacent gravels and sands, but these deposits are mainly hydraulically separate from the underlying Chalk at the site. The hydraulic relationship between the river and underlying alluvium is variable, involving components of groundwater flow both parallel and transverse to the river and with both effluent and influent behaviour seen. While the gravel aquifer is significant in controlling groundwater/surface-water interaction, its importance as a route for flow down the catchment is likely to be modest compared with river discharge. The hydrological complexity revealed in a geological setting typical of lowland UK Chalk streams has implications both for investigation methods and for management such as in the setting of environmental objectives in the European Water Framework Directive.