Tectonothermal history of the basement rocks in the western zone of the North China Craton and its tectonic implications   总被引：47，自引：0，他引：47  

Guochun Zhao  Simon A. Wilde  Peter A. Cawood  Liangzhao Lu 《Tectonophysics》1999,310(1-4):37-53

The basement of the North China Craton can be divided into the eastern, central and western zones, based on lithological, structural, metamorphic and geochronological data. The western zone comprises two different petrotectonic units: Archaean tonalitic–trondhjemitic–granodioritic (TTG) grey gneisses and metamorphic mafic rocks, and Palaeoproterozoic khondalite series. The former is characterized by isobaric cooling (IBC)-type anticlockwise P–T paths in the north-northwestern part of the zone and near-isothermal decompression (ITD)-type clockwise P–T paths in the eastern part, adjacent to the central zone. On the other hand, the tectonothermal evolution of Palaeoproterozoic khondalite series rocks is characterized exclusively by nearly isothermal decompression following the peak of metamorphism and then cooling, defining clockwise P–T paths. The Archaean TTG gneisses and associated mafic rocks with anticlockwise metamorphic P–T paths reflects an origin related to underplating and intrusion of mantle-derived magmas which may be derived from mantle plumes. They represent a late Archaean continental block in the western part of the North China Craton. The Palaeoproterozoic khondalite series rocks represent passive continental margin deposits. They were metamorphosed and deformed in the late Palaeoproterozoic during the amalgamation of the western continental block with another continental block in the east part of the North China Craton. The ITD-type clockwise P–T–t paths of the Palaeoproterozoic khondalite series rocks record the tectonothermal histories of the collision of the western and eastern continental blocks which resulted in the final assembly of the North China Craton at c. 1800 Ma.  相似文献   

Role of coal type and rank on methane sorption characteristics of Bowen Basin, Australia coals   总被引：5，自引：0，他引：5  

Chikatamarla Laxminarayana  Peter J. Crosdale 《International Journal of Coal Geology》1999,40(4):157

The effect of coal composition, particularly the organic fraction, upon gas sorption has been investigated for Bowen Basin and Sydney Basin, Australia coals. Maceral composition influences on gas retention and release were investigated using isorank pairs of hand-picked bright and dull coal in the rank range of high volatile bituminous (0.78% R_{o max}) to anthracite (3.01% R_{o max}). Adsorption isotherm results of dry coals indicated that Langmuir volume (V_L) for bright and dull coal types followed discrete, second-order polynomial trends with increasing rank. Bright coals had a minimum V_L at 1.72% R_{o max} and dull coals had a minimum V_L at 1.17% R_{o max}. At low rank, V_L was greater in bright coal by about 10 cm³/g, but as rank increased, the bright and dull trends converged and crossed at 1.65% R_{o max}. At ranks higher than 1.65% R_{o max}, both bright and dull coals followed similar trends. These competing trends mean that the importance of maceral composition on V_L varies according to rank. In high volatile bituminous coals, increases in vitrinite content are associated with increases in adsorption capacity. At ranks higher than medium to low volatile bituminous, changes in maceral composition may exert relatively little influence on adsorption capacity. The Langmuir pressure (P_L) showed a strong relationship of decreasing P_L with increasing rank, which was not related to coal type. It is suggested that the observed trend is related to a decrease in the heterogeneity of the pore surfaces, and subsequent increased coverage by the adsorbate, as coal rank increases. Desorption rate studies on crushed samples show that dull coals desorb more rapidly than bright coals and that desorption rate is also a function of rank. Coals of lower rank have higher effective diffusivities. Mineral matter was found to have no influence on desorption rate of these finely crushed samples. The evolution of the coal pore structure with changing rank is implicated in diffusion rate differences.  相似文献   

Development of an operational low-flow index for hydrological drought monitoring over Europe   总被引：1，自引：1，他引：0  

Carmelo Cammalleri  Jürgen Vogt  Peter Salamon 《水文科学杂志》2017,62(3):346-358

Near real-time monitoring of hydrological drought requires the implementation of an index capable of capturing the dynamic nature of the phenomenon. Starting from a dataset of modelled daily streamflow data, a low-flow index was developed based on the total water deficit of the discharge values below a certain threshold. In order to account for a range of hydrological regimes, a daily 95th percentile threshold was adopted, which was computed by means of a 31-day moving window. The observed historical total water deficits were statistically fitted by means of the exponential distribution and the corresponding probability values were used as a measure of hydrological drought severity. This approach has the advantage that it directly exploits daily streamflow values, as well as allowing a near real-time update of the index at regular time steps (i.e. 10 days, or dekad). The proposed approach was implemented on discharge data simulated by the LISFLOOD model over Europe during the period 1995–2015; its reliability was tested on four case studies found within the European drought reference database, as well as against the most recent summer drought observed in Central Europe in 2015. These validations, even if only qualitative, highlighted the ability of the index to capture the timing (starting date and duration) of the main historical hydrological drought events, and its good performance in comparison with the commonly used standardized runoff index (SRI). Additionally, the spatial evolution of the most recent event was captured well in a simulated near real-time test case, suggesting the suitability of the index for operational implementation within the European Drought Observatory.  相似文献   

Extreme floods and their relationship with tropical cyclones in Puerto Rico     

José J. Hernández Ayala  David Keellings  Peter R. Waylen  Corene J. Matyas 《水文科学杂志》2017,62(13):2103-2119

An extreme value analysis (EVA) point process approach has been implemented to examine the flood characteristics of Puerto Rico when tropical cyclones (TCs) are present in the discharge series and when they are removed from it. Mean daily discharge values that exceeded the 99th percentile thresholds were used in both the TC and non-TC data series. In nine of the 12 stations the maximum discharge was associated with a TC, with hurricanes Hortense (1996), Georges (1998) and Eloise (1975) responsible for most of the maximum peaks at each site. Percentage changes in the generalized extreme value parameters, which include location (central tendency), scale (variance) and shape (skewness), between the TC and non-TC data exhibited a decrease in the majority of stations. Stations in the eastern interior and central region of the island showed the largest decrease in all parameters, in flood occurrences and in return periods when TCs were removed from the series.  相似文献   

Emerging Technologies and Synergies for Airborne and Space-Based Measurements of Water Vapor Profiles     

Amin R. Nehrir  Christoph Kiemle  Mathew D. Lebsock  Gottfried Kirchengast  Stefan A. Buehler  Ulrich Löhnert  Cong-Liang Liu  Peter C. Hargrave  Maria Barrera-Verdejo  David M. Winker 《Surveys in Geophysics》2017,38(6):1445-1482

A deeper understanding of how clouds will respond to a warming climate is one of the outstanding challenges in climate science. Uncertainties in the response of clouds, and particularly shallow clouds, have been identified as the dominant source of the discrepancy in model estimates of equilibrium climate sensitivity. As the community gains a deeper understanding of the many processes involved, there is a growing appreciation of the critical role played by fluctuations in water vapor and the coupling of water vapor and atmospheric circulations. Reduction of uncertainties in cloud-climate feedbacks and convection initiation as well as improved understanding of processes governing these effects will result from profiling of water vapor in the lower troposphere with improved accuracy and vertical resolution compared to existing airborne and space-based measurements. This paper highlights new technologies and improved measurement approaches for measuring lower tropospheric water vapor and their expected added value to current observations. Those include differential absorption lidar and radar, microwave occultation between low-Earth orbiters, and hyperspectral microwave remote sensing. Each methodology is briefly explained, and measurement capabilities as well as the current technological readiness for aircraft and satellite implementation are specified. Potential synergies between the technologies are discussed, actual examples hereof are given, and future perspectives are explored. Based on technical maturity and the foreseen near-mid-term development path of the various discussed measurement approaches, we find that improved measurements of water vapor throughout the troposphere would greatly benefit from the combination of differential absorption lidar focusing on the lower troposphere with passive remote sensors constraining the upper-tropospheric humidity.  相似文献   

Conditional effects of tides and waves on short‐term marsh sedimentation dynamics          下载免费PDF全文

Zhigang Ma  Tom Ysebaert  Daphne van der Wal  Peter M.J. Herman 《地球表面变化过程与地形》2018,43(10):2243-2255

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A method for uncertainty constraint of catchment discharge and phosphorus load estimates          下载免费PDF全文

Michael J. Hollaway  Keith J. Beven  Clare Mc W. H. Benskin  Adrian L. Collins  Robert Evans  Peter D. Falloon  Kirsty J. Forber  Kevin M. Hiscock  Ron Kahana  Christopher J. A. Macleod  Mary C. Ockenden  Martha L. Villamizar  Catherine Wearing  Paul J. A. Withers  Jian G. Zhou  Nicholas J. Barber  Philip M. Haygarth 《水文研究》2018,32(17):2779-2787

River discharge and nutrient measurements are subject to aleatory and epistemic uncertainties. In this study, we present a novel method for estimating these uncertainties in colocated discharge and phosphorus (P) measurements. The “voting point”‐based method constrains the derived stage‐discharge rating curve both on the fit to available gaugings and to the catchment water balance. This helps reduce the uncertainty beyond the range of available gaugings and during out of bank situations. In the example presented here, for the top 5% of flows, uncertainties are shown to be 139% using a traditional power law fit, compared with 40% when using our updated “voting point” method. Furthermore, the method is extended to in situ and lab analysed nutrient concentration data pairings, with lower uncertainties (81%) shown for high concentrations (top 5%) than when a traditional regression is applied (102%). Overall, for both discharge and nutrient data, the method presented goes some way to accounting for epistemic uncertainties associated with nonstationary physical characteristics of the monitoring site.  相似文献   

Statistical evidence for long-range space-time relationships between large earthquakes     

Peter A. Rogerson 《Journal of Seismology》2018,22(6):1423-1435

Whether large earthquakes are triggered by other large earthquakes at very large distances, and at time scales where the triggered event is delayed by more than several days or weeks, is an open question. Here I provide statistical evidence to show that large earthquakes near the subduction zones of the Pacific plate boundary lessen significantly the average time until the next large earthquake that occurs near the boundaries of the smaller and adjacent Nazca and Cocos plates in the eastern Pacific Ocean. In addition, the existence and importance of this relationship is enriched by the finding that the larger the magnitude of the Pacific plate earthquake, the more likely it becomes that the time until the next earthquake in the distant triggered zone is less than the time since the last earthquake in the triggered zone. There are also specific regions along the western and northern Pacific plates where these relationships appear to be particularly prominent. The findings call into question the notion that the hazard of large earthquakes in distant regions is not raised following other large earthquakes, and they provide statistical evidence for relationships between earthquakes occurring months apart on different plates.  相似文献   

First record of the Australian ascidian Eudistoma elongatum in northern New Zealand     

Peter J. Smith  Mike Page  Sean J. Handley  S. Margaret McVeagh  Merrick Ekins 《新西兰海洋与淡水研究杂志》2013,47(4):347-355

A colonial ascidian was first reported by marine farmers in Houhora Harbour, Northland, New Zealand in early 2005 and subsequently found on oyster racks in Parengarenga Harbour and the Bay of Islands. The Northland ascidian was identified with a combination of morphological characters and DNA cytochrome c oxidase I (COI) sequence data, as Eudistoma elongatum, a species native to Australia, where it is found from northern New South Wales to Northern Queensland, and distinguished from Eudistoma circumvallatum, the only reported species in this genus from New Zealand. Ascidian larvae are weak dispersers and long distance dispersal of E. elongatum is likely to be enhanced by vectors such as oyster barges and/or movement of cultured oysters. In its native range, E. elongatum is restricted to areas with a minimum winter sea temperature of 16°C. Assuming similar biological limitations apply in New Zealand, the spread of E. elongatum might be restricted to northern New Zealand (north of latitude 37°S).  相似文献   

The origins of agriculture in Europe     

Peter Bogucki 《Geoarchaeology》2000,15(4):377-379

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