Geochemistry, Geochronology and Lu-Hf Isotopes of Peraluminous Granitic Porphyry from the Walegen Au Deposit, West Qinling Terrane     

GUO Xianqing  YAN Zhen  Jonathan C. AITCHISON  FU Changlei  WANG Zongqi 《《地质学报》英文版》2017,91(6):2024-2040

Walegen Au deposit is closely correlated with granitic intrusions of Triassic age, which are composed of granite and quartz porphyries. Both granite porphyry and quartz porphyry consist of quartz, feldspar and muscovite as primary minerals. Weakly peraluminous granite porphyry(A/CNK=1.10–1.15) is enriched in LREE, depleted in HREE with Nb-Ta-Ti anomalies, and displays subduction-related geochemistry. Quartz porphyry is strongly peraluminous(A/CNK=1.64–2.81) with highly evolved components, characterized by lower TiO_2, REE contents, Mg~#, K/Rb, Nb/Ta, Zr/Hf ratios and higher Rb/Sr ratios than the granite porphyry. REE patterns of quartz porphyry exhibit lanthanide tetrad effect, resulting from mineral fractionation or participation of fluids with enriched F and Cl. LAICP-MS zircon U-Pb dating indicates quartz porphyry formed at 233±3 Ma. The ages of relict zircons from Triassic magmatic rocks match well with the detrital zircons from regional area. In addition, ε_(Hf)(t) values of Triassic magmatic zircons from the granite and quartz porphyries are -14.2 to -9.1(with an exception of +4.1) and -10.8 to -8.6 respectively, indicating a crustal-dominant source. Regionally, numerous Middle Triassic granitoids were previously reported to be formed under the consumption of Paleotethyan Ocean. These facts indicate that the granitic porphyries from Walegen Au deposit may have been formed in the processes of the closing of Paleotethyan Ocean, which could correlate with the arc-related magmatism in the Kunlun orogen to the west and the Qinling orogen to the east.  相似文献   

Politicians and geomorphological blunders. Some examples relating to rivers and coasts from Queensland,Australia     

Jonathan Nott 《Singapore journal of tropical geography》2010,31(3):283-298

Editors' Note: The following is the eighth in the Singapore Journal of Tropical Geography Lecture Series. It is based on the plenary presentation of 10 July at the 7th International Conference on Geomorphology held in Melbourne in 2009. Geomorphologists have an important role to not just understand and interpret the nature of processes operating within the physical landscape, but also to communicate this information to those who can use it to benefit society. Policy makers and legislators often develop documents relating to the management and use of landforms and landscapes that contain little or no input from geomorphologists, which can and do have undesirable consequences for governments, communities and the natural environment. Examples relating to rivers and coasts from Queensland, Australia highlight inadequacies in policies and legislation because of a lack of input from geomorphologists. In one instance the definition of a stream channel has been reinterpreted by the legal system because of a poorly developed definition within the legislation. The outcome is a legal definition of a stream channel based on the Q3 month flow (3‐month average recurrence interval discharge or flow). In another instance, people and property are being placed at risk from coastal erosion and impact from tropical cyclone generated marine inundations (waves and surge) because a lack of understanding of geomorphic processes operating along the coast has been inscribed into policies and legislation. These are examples from one region but similar situations will exist elsewhere globally. Both politicians and geomorphologists have a role to communicate better with each other about these matters. Geomorphologists in particular need to be more proactive in advising politicians on issues in which they have expertise.  相似文献   

A discontinuous finite element baroclinic marine model on unstructured prismatic meshes     

Richard Comblen  Sébastien Blaise  Vincent Legat  Jean-François Remacle  Eric Deleersnijder  Jonathan Lambrechts 《Ocean Dynamics》2010,60(6):1395-1414

We describe the time discretization of a three-dimensional baroclinic finite element model for the hydrostatic Boussinesq equations based upon a discontinuous Galerkin finite element method. On one hand, the time marching algorithm is based on an efficient mode splitting. To ensure compatibility between the barotropic and baroclinic modes in the splitting algorithm, we introduce Lagrange multipliers in the discrete formulation. On the other hand, the use of implicit–explicit Runge–Kutta methods enables us to treat stiff linear operators implicitly, while the rest of the nonlinear dynamics is treated explicitly. By way of illustration, the time evolution of the flow over a tall isolated seamount on the sphere is simulated. The seamount height is 90% of the mean sea depth. Vortex shedding and Taylor caps are observed. The simulation compares well with results published by other authors.  相似文献   

Organic carbon inputs,common ions and degassing: rethinking mixing dissolution in coastal eogenetic carbonate aquifers          下载免费PDF全文

Jason D. Gulley  Jonathan B.Martin  Amy Brown 《地球表面变化过程与地形》2016,41(14):2098-2110

Caves deliver freshwater from coastal carbonate landscapes to estuaries but how these caves form and grow remains poorly understood. Models suggest fresh and salt water mixing drives dissolution in eogenetic limestone, but have rarely been validated through sampling of mixing waters. Here we assess controls on carbonate mineral saturation states using new and legacy geochemical data that were collected in vertical profiles through three cenotes and one borehole in the Yucatan Peninsula. Results suggest saturation states are primarily controlled by carbon fluxes rather than mixing. Undersaturation predicted by mixing models that rely on idealized end members is diminished or eliminated when end members are collected from above and below actual mixing zones. Undersaturation due to mixing is limited by CO₂ degassing from fresh water in karst windows, which results in calcite supersaturation. With respect to saline groundwater, controls on capacity for mixing dissolution were more varied. Oxidation of organic carbon increased pCO₂ of saline groundwater in caves (pCO₂ = 10^–2.06 to 10^–0.96 atm) relative to matrix porosity (10^–2.39 atm) and local seawater (10^–3.12 atm). The impact of increased pCO₂ on saturation state, however, depended on the geochemical composition of the saline water and the magnitude of organic carbon oxidation. Carbonate undersaturation due to mixing was limited where gypsum dissolution (Cenote Angelita) or sulfate reduction (Cenote Calica) increased concentrations of common ions (Ca²⁺ or HCO₃^?, respectively). Maximum undersaturation was found to occur in mixtures including saline water that had ion concentrations and ratios similar to seawater, but with moderately elevated pCO₂ (Cenote Eden). Undersaturation, however, was dominated by the initial undersaturation of the saline end member, mixing was irrelevant. Our results add to a growing body of literature that suggests oxidation of organic carbon, and not mixing dissolution, is the dominant control on cave formation and enlargement in coastal eogenetic karst aquifers. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Relations between hydrology and velocity of a continuously moving landslide—evidence of pore-pressure feedback regulating landslide motion?   总被引：1，自引：0，他引：1  

William H. Schulz  Jonathan P. McKenna  John D. Kibler  Giulia Biavati 《Landslides》2009,6(3):181-190

We measured displacement, pore-water pressure, and climatic conditions for 3 years at the continuously moving Slumgullion landslide in Colorado, USA. The landslide accelerated when pore-water pressure increased within the landslide body, but this occurred as pore-water pressure decreased along the landslide margin. The decrease probably occurred in response to shear-induced soil dilation at rates greater than pore-pressure diffusion and likely increased resistance to shear displacement and resulted in landslide deceleration. This dilative strengthening has been experimentally observed and explained theoretically, but not previously identified during field studies. Although landslide displacement should have exceeded that required to achieve critical-state density of shear boundaries, observed relocation of these boundaries indicates that shearing is episodic at fixed locations, so it permits renewed dilative strengthening when “fresh” soil is sheared. Thus, dilatant strengthening may be a considerable mechanism controlling landslide velocity, even for landslides that have continuously moved great distances.  相似文献   

Trade Fair Educational Programs and Access to Knowledge: Evidence from the Solar PV Sector     

Jonathan D. German  Ronald V. Kalafsky 《The Professional geographer》2013,65(4):715-724

In view of a globalizing marketplace and the continual need for market intelligence, firms seek venues in which to access cost effective, functional information. Significant sources of such knowledge, especially in tacit form, can be found within temporary clusters: international trade fairs. This article explores how firms in the solar photovoltaic (PV) industry use educational programs held during a trade fair as a means of information acquisition and exchange, providing a new angle to research on the economic geographies of these events, especially in terms of learning processes. Specifically, it analyzes how firms use educational programs to access remote knowledge (i.e., tacit information unavailable in a local context) in these temporary, spatially confined environments. Analyses of firm-level survey data gathered at a recent solar industry trade fair revealed that there is a significant effect of educational program participation on accessing remote knowledge. The results provide evidence that firms participate in trade fair educational programs to access remote knowledge that is critical to international success. Key Words: educational programs, knowledge exchange, remote knowledge, trade fairs.  相似文献   

BIBLIOGRAPHY—BIBLIOGRAPHIE     

Jiahu Wang  Li Li  Jonathan J. Gourley  Sadiq I. Khan  Koray K. Yilmaz 《水文科学杂志》2013,58(1):84-98

Abstract

The Coupled Routing and Excess STorage model (CREST, jointly developed by the University of Oklahoma and NASA SERVIR) is a distributed hydrological model developed to simulate the spatial and temporal variation of land surface, and subsurface water fluxes and storages by cell-to-cell simulation. CREST's distinguishing characteristics include: (1) distributed rainfall–runoff generation and cell-to-cell routing; (2) coupled runoff generation and routing via three feedback mechanisms; and (3) representation of sub-grid cell variability of soil moisture storage capacity and sub-grid cell routing (via linear reservoirs). The coupling between the runoff generation and routing mechanisms allows detailed and realistic treatment of hydrological variables such as soil moisture. Furthermore, the representation of soil moisture variability and routing processes at the sub-grid scale enables the CREST model to be readily scalable to multi-scale modelling research. This paper presents the model development and demonstrates its applicability for a case study in the Nzoia basin located in Lake Victoria, Africa.

Citation Wang, J., Yang, H., Li, L., Gourley, J. J., Sadiq, I. K., Yilmaz, K. K., Adler, R. F., Policelli, F. S., Habib, S., Irwn, D., Limaye, A. S., Korme, T. &; Okello, L. (2011) The coupled routing and excess storage (CREST) distributed hydrological model. Hydrol. Sci. J. 56(1), 84–98.  相似文献   

Distribution and properties of soft weathered bedrock at ≤ 1 m depth in the contiguous United States     

Jonathan A. Wald  Robert C. Graham  Phillip J. Schoeneberger 《地球表面变化过程与地形》2013,38(6):614-626

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RELATIVE AGES OF WETLAND AND UPLAND SURFACES AS INDICATED BY PEDOGENIC DEVELOPMENT     

Jonathan D. Phillips 《自然地理学》2013,34(4):363-378

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HUMAN IMPACTS ON THE ENVIRONMENT: UNPREDICTABILITY AND THE PRIMACY OF PLACE     

Jonathan D. Phillips 《自然地理学》2013,34(4):321-332

Landscapes, environments, and ecosystems (i.e., places) are historically and spatially contingent and therefore unique. Generalizations and laws are based on “all other things being equal.” Owing to historical and spatial contingency, all other things are never completely equal and often do not approach that ideal closely enough to allow for reliable prediction. The problem is illustrated by examining effects of grazing and fire suppression on transitions between grass and woody vegetation communities. In three different environments in the southern United States (central Texas, southwestern Virginia, and eastern North Carolina), three different relationships exist between grazing and fire regime, and vegetation. Other examples are common in the geographic and environmental literature. This suggests that the search for a single applicable generalization or predictive model of a given human-induced environmental change that can be applied without accounting for the particular characteristics of places may be futile. Several general ways to address this issue are suggested. First is the recognition that place matters. Conditions specific to a location or region will influence what, how, or even if generalizations apply. Second is the adoption of a “demographic” approach. This is based on the idea that for places, like people, it is possible to make aggregate or probabilistic generalizations or predictions, but these cannot be applied to deterministic prediction of individuals. Third is a synoptic approach based on forecasting not via simple cause-effect relationships, but based on a typology of situations that recognizes and incorporates the unique characteristics of site and situation. Several converging threads of inquiry in geography and geosciences explicitly or implicitly address the issue of historical and spatial contingency. [Key words: landscape, environment, place, prediction.]  相似文献