首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到17条相似文献,搜索用时 11 毫秒
1.
介绍一种优化地下水污染监测网的软件--MAROS   总被引:1,自引:0,他引:1  
MAROS是首个基于Windows平台利用MicrosoftAccess和MicrosoftExcel开发出来的用于地下水污染监测网优化设计的决策支持系统软件。该软件通过统计分析监测区域有关数据在时空上的相关分析结果,来确定监测网在时间上的取样频率和空间上的分布密度,从而保证以最省的监测费用获得地下水污染物随时间和空间变化的最全面信息。本文简单地介绍了MAROS的设计原理和模块组成,并对该软件的优缺点进行了评述。  相似文献   

2.
在全球变暖的背景下,我国多数大江大河源区存在冰川退缩、雪线上升以及多年冻土和季节冻土明显退化等现象,并由此造成河源区产流量减少以及生态环境恶化等诸多问题,这在内陆河山区流域体现的较为明显,但目前分布式水文模型中很少涉及冻土水热耦合问题。文章以黑河干流山区流域为例,构建了一个内陆河高寒山区流域分布式水热耦合模型(DWHC)。模型基于土壤水热连续性方程将流域产流、入渗和蒸散发过程融合起来,在植被截留、入渗、产流和蒸散发计算方面也有所改进和创新,部分模块具有多个可选择方案。模型设计了与中尺度大气模式MM5的嵌套接口,也可以用地面气象资料驱动。模型在1 km×1 km网格基础上,以日为时间步长,将流域土壤分为18类,土壤剖面分为3~5层不等,流域植被概化为9类。模型只需要土壤初始含水量、初始地温和常规气象资料,以及土壤和植被物理参数,就能够连续演算各层土壤的温度、液态含水量、固态含水量、感热传导、潜热变化、水势梯度、导水率以及水分入渗和毛细上升量等水文循环要素。主要介绍了模型的基本原理和构建思路,有关模型的地面资料驱动结果和与MM5嵌套结果部分,参见后续文章(Ⅱ)、(Ⅲ)。  相似文献   

3.
This paper illustrates that sample size cannot be reduced below a theoretical limit and still achieve the highest precision obtainable on modern mass spectrometers. Reproducibility at the few ppm level is achievable and is related essentially to ion counting statistics. The number of atoms necessary to carry out such measurements is related directly to the sensitivity of the instrumentation. As most of the elements of interest are not major constituents of natural silicates, a lower limit to the size of the starting sample is assessed. Even for a number of elements for which very high ion per atom yields are attained by TIMS, minimum sample mass is an important limiting factor for precious or rare samples and may reduce the scientific output of experiments or place a major constraint on the sampling strategy itself. For rare meteorites or individual Martian samples expected to be returned in amounts at the gramme scale for rocks or at the microgramme scale for dust, the high sensitivity of TIMS is a requirement. Nevertheless, a compromise has to be found between sample consumption and the minimal desirable precision for a useful isotopic measurement.  相似文献   

4.
玉龙斑岩铜(钼)矿床是亚洲最大的斑岩型铜矿床,包含多种矿化类型,成矿作用复杂。作为典型的斑岩型矿床,岩浆熔融体的性质在玉龙铜矿床的形成过程中起到了至关重要的作用。本文将分别从岩浆熔融体的物理和化学性质出发,解释玉龙矿床为何能成为玉龙成矿带中唯一一个超大型矿床的原因。在熔体演化方面,笔者主要通过对熔体密度、粘度的计算获得有关数据,以了解熔体运移、含矿流体分离的过程,以解释玉龙铜矿床为何能形成如此规模的矿床。  相似文献   

5.
The Vidigueira–Moura fault (VMF) is a 65 km long, E–W trending, N dipping reverse left-lateral late Variscan structure located in SE Portugal (W Iberia), which has been reactivated during the Cenozoic with reverse right-lateral slip. It is intersected by, and interferes with the NE–SW trending Alentejo–Plasencia fault. East of this intersection, for a length of 40 km the VMF borders an intracratonic tectonic basin on its northern side, thrusting Paleozoic schists, meta-volcanics and granites, on the north, over Cenozoic continental sediments preserved in the basin, on the south. West of the faults intersection, evidence of Cenozoic reactivation is scarce. In the eastern sector, Plio-Quaternary VMF reactivation is indicated by geomorphologic, stratigraphic, and structural data, showing reverse movement with a right-lateral strike-slip component, in response to a NW–SE trending compressive stress. An average vertical displacement rate of 0.06 to 0.08 mm/yr since late Pliocene (roughly the last 2.5 Ma) is estimated. The Alqueva fault (AF) is a subparallel, northward dipping, 7.5 km long anastomosing fault zone that affects Palaeozoic basement rocks, and is located 2.5 km north and on the hanging block of the VMF. The AF is also a reverse left-lateral late Variscan structure, which has been reactivated during the Tertiary with reverse right-lateral slip; however, Plio-Quaternary reactivation was normal left-lateral, as shown by abundant kinematical criteria (slickensides) and geomorphic evidence. It shows an average displacement rate of 0.02 mm/yr for the vertical component of movement in the approximately last 2.5 Ma. It is proposed that the normal displacements on the AF result from tangential longitudinal strain on the upthrown block of the VMF above a convex ramp of this main reverse structure. According to this model of faults interaction, the AF is interpreted to work as a bending-moment fault sited above the VMF thrust ramp. Consequently, it is expected that the displacements on the AF increase towards the topographic surface with the increase in the imposed extension, declining downwards until they vanish above or at the VMF ramp. In order to constrain the proposed scheme, numerical modeling was performed, aiming at the reproduction of the present topography across the faults using different geodynamic models and fault geometries and displacements.  相似文献   

6.
刘志飞 《沉积学报》2002,20(2):354-358
PC99是基于Windows 95 / 98/ 2 0 0 0版本操作系统的VisualBasic语言程序,以简单和友好界面图形显示、统计分析和比较古水流数据文件。这种软件支持的古水流数据显示方式包括玫瑰花图和环形图两种,玫瑰花图的花瓣宽度和半径比例尺的可调节性可以辅以解释古水流分布样式,环形图可以同时装载、显示和比较 10个单组或合成古水流数据文件。本文以青藏高原北部可可西里盆地新生代沉积的古水流数据为例,分析古水流方向的时空分布特征,表明PC99是图形显示和解释古水流数据的一种高效软件工具。  相似文献   

7.
An isotopic study was systemically carried out on the granitic complex, diorite-porphyrite, ores and ore minerals of the 103 Ma Xiaoxinancha gold-rich copper deposit in Jilin province to determine the geodynamic model of diagenesis and metallogenesis. Results show that the initial Nd and Sr isotopic compositions of the granitic complex are in the range of 0.70425–0.70505 for (87Sr/86Sr)i , 0.51243–0.51264 for INd, and –1.31 to +2.64 for εNd(t); those of the diorite-porphyrite are in the range from 0.70438–0.70448 for (87Sr/86Sr)i, 0.51259–0.51261 for INd, and +1.56 to +2.09 for εNd(t). For ores and sulfides, the (87Sr/86Sr)i , INd, and εNd(t) values are in the range from 0.70440–0.70805, 0.51259–0.51279 and +1.72 to +5.56, respectively. The Pb isotopic ratios of the granitic complex range from 18.2992–18.6636 for 206Pb/204Pb, from 15.5343–15.5660 for 207Pb/204Pb, and from 38.1640–38.5657 for 208Pb/204Pb. For diorite-porphyrite, the isotopic ratios of 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb are 18.3919, 15.5794 and 38.3566, respectively, whereas those of the ores and ore sulfides vary from 18.2275–18.3770 for 206Pb/204Pb, from 15.5555–15.5934 for 207Pb/204Pb and from 38.1318–38.3131 for 208Pb/204Pb. The results indicate that the mineralization was correlated to the formation and evolution of the granitic complex and the diorite-porphyrite. Combining with the reported data in petrologic characteristics, elemental geochemistry and chronology, conclusions can be drawn that the geodynamic settings of diagenesis and metallogenesis of this deposit were consistent with the subduction of the Izanagi oceanic plate during the Early Cretaceous. The diorite-porphyrite was formed by the emplacement of the adakitic magma triggered by partial melting of the enriched mantle, which originated from the derivative continental lithospheric mantle metasomatized by dehydration fluids from the subducting oceanic crust. The granitic complex was produced by fractional crystallization of the mixture between the adakitic magma and the high-K calc-alkaline acidic magma, which were generated by the remelting of the lower crust in the course of intraplate upwelling of the adakitic magma. The ore-bearing fluid reservoir convened in a late stage of the evolution of the mixed magma chamber.  相似文献   

8.
The first definitive fossil of the peculiar monotypic rove beetle subfamily Megalopsidiinae is described as a new species Megalopinus extinctus sp. n. It represents a stem lineage valuable for the study of the early diversification of Staphylinidae, where sister group relationships of Megalopsidiinae currently remain a big controversy. This discovery corroborates the Mesozoic origin of this subfamily implied by its presumably basal phylogenetic position within Staphylinidae and hitherto available fossil record for the family. Well preserved peculiar mouthparts of M. extinctus specialized similarly with recent Megalopinus suggest the same mode of feeding in Megalopsidiinae for nearly a hundred million years.  相似文献   

9.
On June 19, 1996, an extremely heavy rainstorm hit a restricted area in the Apuan Alps (northwestern Tuscany, Italy). Its max intensity concentrated over an area of about 150 km2 astride the Apuan chain, where 474 mm was recorded in about 12 h (21% of the mean annual precipitation, with an intensity up to 158 mm/h). The storm caused floods and hundreds of landslides and debris flows, which produced huge damage (hundreds of millions of Euros), partially destroyed villages and killed 14 people. This paper reports the results obtained from a detailed field survey and aerial view interpretation. In the most severely involved area, 647 main landslides were investigated, mapped and related to the geologic, geomorphic and vegetational factors of the source areas. This was in order to define the influence of these factors and contribute to an evaluation of the landslide hazard in the study area. An assessment was also made of the total area and volume of material mobilised by landsliding. The study area, about 46 km2 wide, includes three typically mountainous basins, characterised by narrow, deep cut valleys and steep slopes, where many rock types outcrop. Most of the landslides were shallow and linear, referable to complex, earth and debris translational slide, which quickly developed into flow (soil slip–debris flow). Usually, they involved colluvium and started in hollows underlain by metamorphic rock (metasandstone and phyllite), often dipping downslope. Therefore, bedrock lithology and impermeability appeared to be important factors in the localisation of the landslide phenomena. The investigation of the geomorphic and land use features in the source areas also frequently highlighted a rectilinear profile of the slope, a high slope gradient (31–45°) and dense chestnut wood cover. In the area, about 985,000 m2 (2.1% of 46 km2) was affected by landsliding and about 700,000 m2 of this area was covered by chestnut forest. The landslides removed about 7000 trees. The volume of mobilised material was about 1,360,000 m3; about 220,000 m3 remained on the slopes, while the rest poured into the streams. In addition, about 945,000 m3 was mobilised by the torrential erosion in the riverbeds.  相似文献   

10.
In the central Iranian Esfahan-Sirjan and Qom basins sedimentation of the Oligo-/Miocene Qom Formation took place on extensive mixed carbonate–siliciclastic ramps. During this time, both basins were positioned at the Eurasian margin of the Tethyan Seaway, which connected the western and eastern regions of the Tethys Ocean at least until the late Burdigalian. During the so-called Terminal Tethyan Event the Tethyan Seaway was then closed due to the collision of the African/Arabian and Iranian/Eurasian plates. Facies analysis of the sedimentary record of both basins indicates paleoenvironments ranging from terrestrial to open marine settings, including mangrove, restricted inner shelf lagoon, seagrass meadow, reefal, and deeper offshore environments. Recognition of eight depositional sequences and elaboration of an integrated biostratigraphic framework (calcareous nannoplankton, planktic and larger benthic foraminifers, gastropods, and pectinids) allow us to construct a basin-spanning stratigraphy. The assignment of the recognized sea-level lowstands to the Ru 3 to Bur 3 lowstands of the global sea-level curve enables a comparison with time-equivalent sections from the Zagros Basin, which was part of the African/Arabian Plate on the opposing southern margin of the Tethyan Seaway. The so calibrated sections display restrictions of the Tethyan Seaway and interruption of the south Iranian gateways between the Qom Basin and the Proto-Indopacific in relation to ongoing plate collision during the early Burdigalian.  相似文献   

11.
Lower Cretaceous successions that crop out in the eastern part of the Getic Carbonate Platform (Southern Carpathians, Romania) preserve records of the Valanginian events in different settings of the platform. The integrated sedimentological, biostratigraphical, geochemical and mineralogical analysis of the upper Berriasian–Valanginian successions reveal successive stages in the evolution of the carbonate platform: (a) pre-drowning stage of the shallow-shelf and slope settings of the platform; (b) subaerial exposure and karstification; and (c) incipient flooding and drowning of the carbonate platform. Following the subaerial exposure, starting in the middle early Valanginian, the eastern part of the Getic Carbonate Platform experienced a drowning phase documented by iron oxyhydroxides, phosphate and glaucony mineralized discontinuity surface and glaucony-rich sediments disposed on the discontinuity surface. Recognition of the diachronous intra-Valanginian discontinuity surface within the studied successions is based on clear evidences (facies contrast, depositional and diagenetic features, biostratigraphic and taphonomic data, and geometrical relations). The negative–positive carbon isotope excursion is correlated with the global perturbations of the carbon cycle related to the Valanginian “Weissert” episode, and it is documented for the first time in the shallowest parts of the Getic Carbonate Platform. Tectonic activity and eustatic sea-level fluctuations were most probably the main factors that led to fault-block tilting, local emersion and subsequent drowning of the eastern part of the Getic Carbonate Platform during the Early Cretaceous. We infer that the eastern part of the Getic Carbonate Platform was affected by late Berriasian–early Hauterivian extensional tectonics that could be related to the Neo-Cimmerian movements with effects generally recognized in the northern peri-Tethyan areas.  相似文献   

12.
Plutonic and gneissic rocks of the Sila Massif in the uppermost portion of the Neto drainage basin (Calabria, Southern Italy) weather and erode under a humid Mediterranean climate. During the development of weathering profiles, a combination of chemical weathering and granular disintegration processes occurred. Chemical weathering involves a loss of both plagioclase (mainly during grus generation) and K-feldspar (mainly during soil formation). This loss is attributed to transformation of plagioclase to clay minerals and to leaching and dissolution of K-feldspar. Sand composition is quartzofeldspathic and nearly homogeneous along the main channel of the Neto River, even where the river cuts across a blanket of sedimentary cover. Thus, fluvial transport does not alter sand composition within the Neto drainage basin. Petrographic indices are effective in (1) discriminating between contributions from similar (granite and gneiss) source rocks (Qm/F); (2) relating the provenance of plutoniclastic and gneissiclastic sand found in the headwaters to grus horizons (Qm/F; Q/Rg); and (3) distinguishing between upstream first-cycle and downstream multicycle sand (Q/Rg). This last distinction is further emphasized by considering both aphanitic and phaneritic varieties of rock fragments (RgRmRs diagram). Chemical weathering is the main sand producer within the regolithic environment in northern Calabria. In addition, rapid erosion resulting from steep slopes removes weathered products, and rapid and short transport leads to minimal sediment maturation. In general, the F/Q index is climate and relief dependent; thus, it should be used in conjunction with palaeoclimatic and palaeophysiographic evidence for provenance interpretations of ancient quartzofeldspathic sandstones.  相似文献   

13.
14.
Detailed structural analysis of the Sierra de Lújar in the western Alpujarras region (Betic Cordilleras, S Spain), a very representative area of the terrain known as the Alborán Domain, has revealed the existence of a very large N-vergent recumbent syncline which involves the whole mountain massif and neighbouring areas. The Lújar syncline and, probably, the associated recumbent anticline which crops out southeast of Sierra de Lújar show a great variation in the orientation of the hinge line. Although having a curved shape, the hinge line is contained in a plane whose attitude coincides with the main attitude of the axial-plane crenulation foliation (Sc), suggesting that it is a sheath fold.The strongly deformed overturned limb of the syncline is cut by two low-angle normal faults displacing towards the north. Similarity in the kinematics between the faults and the fold, and the association between the faults and the high-strain zone in the overturned limb of the fold, suggest that they are related. Regional constraints on the age of the crenulation cleavage and the low-angle normal faults indicate that they formed during the early Miocene late-orogenic extensional event in the Alborán Domain.We propose an alternate explanation for the structure of the Alpujarras region in which the Lújar syncline forms part of a recumbent syncline–anticline pair that extends along much of the Alpujarride outcrop in the southern Betic Cordillera. In several places, the fold is disrupted by low-angle normal faults, and it is overlain by an upper Alpujárride extensional sheet mainly composed of medium- to high-grade metamorphic rocks. We suggest that all these structures arose from the extensional deformation under decreasing temperature conditions of a previously thickened and metamorphosed orogenic crust.  相似文献   

15.
This study is the summary analysis of bulk XRF geochemistry (233 samples from three sections) of the Oka and Zaborie groups of the type Serpukhovian succession in the Moscow Basin. The siliciclastic wedges in the limestone‐dominated Oka Group are two to three times enriched in Fe, Ti, and Zr compared to Clarke values. Bulk iron strongly correlates with magnetic susceptibility. Iron tends to form ferruginized horizons (original siderites) in finer grained siliciclastic beds associated with coal seams. These beds also tend to be enriched in Cu, Ni, Pb, Zn, and other trace metals (metal enrichment horizons or MEHs). MEHs formed in ponded conditions of coastal low‐pH marshlands vegetated by mangrove‐like lycopsid bushes. Well‐drained environments of palaeokarst formation and alkaline everglades (Akulshino palustrine event) on the other hand did not accumulate Fe and trace metals. The thin shale seam (found close to the Viséan–Serpukhovian boundary in Polotnyanyi Zavod) has unusually high Rb and Sr values, which may contain volcanigenic material useful for absolute dating. The Gurovo Formation (Steshevian Substage of the Serpukhovian) is less enriched in Fe and Ti. In the Gurovo Formation, the transition from the lower montmorillonitic shale (Glazechnya Member) to the upper palygorskitic shale (Dashkovka Member) is expressed by a five‐fold increase in background MgO values, which indicates progressive shoaling and climatic aridization. Phosphorus remains close to 0% in the Oka Group and tends to increase in the Zaborie Group, in agreement with a dramatic increase of conodont numbers and other signatures of a lower Serpukhovian marine transgression. The lower half of the Glazechnya Member exhibits fluctuating enrichment in Fe, Cu, Ni, Pb, Zn, V, Cr, and Co. These fluctuations are mostly inverse to fluctuations of Mn. This pattern has been interpreted as a signature of seafloor oxygen deficiency, where Mn‐rich samples record oxygen‐poor environments (redox barrier level with the sediment surface) and Mn‐poor samples enriched in Fe and trace metals record transitions to anoxic setting. This interval is interpreted as the Lower Serpukhovian highstand. Enrichment in Fe, Ti, and Zr of Oka siliciclastic units of Polotnyanyi Zavod indicates provenance from the ore‐rich Voronezh Land, south of the Moscow Basin. The westerly flux regarded as a possible provenance in previous palaeogeographic reconstructions is discarded for the studied sections. The Gurovo Shale is also linked to the Voronezh province, although Fe, Ti, and Zr concentrations are lower than in the Oka shales. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

16.
The Great Lisbon earthquake of 1755 with an estimated magnitude of 8.5–9.0 is the most destructive earthquake in European history, yet the source region remains enigmatic. Recent geophysical data provide compelling evidence for an active east dipping subduction zone beneath the nearby Gibraltar Arc. Marine seismic data in the Gulf of Cadiz image active thrust faults in an accretionary wedge, above an east dipping decollement and an eastward dipping basement. Tomographic and other data support subduction and rollback of a narrow slab of oceanic lithosphere beneath the westward advancing Gibraltar block.Although, no instrumentally recorded seismicity has been documented for the subduction interface, we propose the hypothesis that this shallow east dipping fault plane is locked and capable of generating great earthquakes (like the Nankai or Cascadia seismogenic zones). We further propose this east dipping fault plane to be a candidate source for the Great Lisbon earthquake of 1755. In this paper we use all available geophysical data on the deep structure of the Gulf of Cadiz–Gibraltar region for the purpose of constraining the 3-D geometry of this potentially seismogenic fault plane. To this end, we use new depth processed seismic data, have interpreted all available published and unpublished time sections, examine the distribution of hypocenters and perform 2-D gravity modeling. Finally, a finite-element model of the forearc thermal structure is constructed to determine the temperature distribution along the fault interface and thus the thermally predicted updip and downdip limits of the seismogenic zone.  相似文献   

17.
The upper Viséan–Serpukhovian strata in the type region for the Serpukhovian Stage is an epeiric‐sea succession ca. 90 m in thickness. The predominantly Viséan Oka Group (comprising the Aleksin, Mikhailov, and Venev formations) is dominated by photozoan packstones with fluvial siliciclastic wedges developed from the west. The Lower Serpukhovian Zaborie Group is composed of the Tarusa and Gurovo formations. The latter is a new name for the shale‐dominated unit of Steshevian Substage age in the studied area. The Zaborie Group is composed of limestones and marls in its lower (Tarusa and basal Gurovo) part and black smectitic to grey palygorskitic shales in the main part of the Gurovo Formation. The Gurovo Formation is capped by a thin limestone with oncoids and a palygorskitic–calcretic palaeosol. The Upper Serpukhovian is composed of a thin (3–12 m) Protva Limestone heavily karstified during a mid‐Carboniferous lowstand. The succession shows a number of unusual sedimentary features, such as a lack of high‐energy facies, shallow‐subtidal marine sediments penetrated by Stigmaria, the inferred atidal to microtidal regime, and palustrine beds composed of saponitic marls. The succession contains many subaerial disconformities characterized by profiles ranging from undercoal solution horizons to palaeokarsts. Incised fluvial channels are reported at two stratigraphic levels to the west of the study area. The deepest incisions developed from the Kholm Disconformity (top of the Mikhailov Formation). This disconformity also exhibits the deepest palaeokarst profile and represents the major hiatus in the Oka–Zaborie succession. The new sea‐level curve presented herein shows two major cycles separated by the Kholm Unconformity at the Mikhailov/Venev boundary. The Lower Serpukhovian transgression moved the base‐level away from falling below the seafloor so that the section becomes conformable above the Forino Disconformity (lower Tarusa). The maximum deepening is interpreted to occur in the lower dark‐shale part of the Gurovo Formation. The base of the Serpukhovian Stage is defined by FADs of the conodont Lochriea ziegleri and the foraminifer Janischewskina delicata in the middle of the sequence VN2. The Aleksinian–Mikhailovian interval is provisionally correlated with the Asbian (Lower–Middle Warnantian) in Western Europe. Based on FODs of Janischewskina typica and first representatives of Climacammina, the Venevian is correlated with the Brigantian in Western Europe. The Tarusian–Protvian interval contains diverse fusulinid and conodont assemblages, but few forms suitable for international correlation. FADs of the zonal conodont species Adetognathus unicornis and Gnathodus bollandensis at several metres above the Protvian base suggest correlation of the entire Zaborie Group and may be the basal Protvian to the Pendleian. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号