Effect of grain‐scale pressure variations on garnet growth: a numerical approach          下载免费PDF全文

X. Zhong  J.C. Vrijmoed  L. Tajčmanová 《Journal of Metamorphic Geology》2017,35(1):19-33

  相似文献   

Diamond in metasedimentary crustal rocks from Pohorje,Eastern Alps: a window to deep continental subduction          下载免费PDF全文

M. Janák  N. Froitzheim  K. Yoshida  V. Sasinková  M. Nosko  T. Kobayashi  T. Hirajima  M. Vrabec 《Journal of Metamorphic Geology》2015,33(5):495-512

We report the first finding of diamond and moissanite in metasedimentary crustal rocks of Pohorje Mountains (Slovenia) in the Austroalpine ultrahigh‐pressure (UHP) metamorphic terrane of the Eastern Alps. Microscopic observations and Raman spectroscopy show that diamond occurs in situ as inclusions in garnet, being heterogeneously distributed. Under the optical microscope, diamond‐bearing inclusions are of cuboidal to rounded shape and of pinkish, yellow to brownish colour. The Raman spectra of the investigated diamond show a sharp, first order peak of sp³‐bonded carbon, in most cases centred between 1332 and 1330 cm^?1, with a full width at half maximum between 3 and 5 cm^?1. Several spectra show Raman bands typical for disordered graphitic (sp²‐bonded) carbon. Detailed observations show that diamond occurs either as a monomineralic, single‐crystal inclusion or it is associated with SiC (moissanite), CO₂ and CH₄ in polyphase inclusions_. This rare record of diamond occurring with moissanite as fluid‐inclusion daughter minerals implies the crystallization of diamond and moissanite from a supercritical fluid at reducing conditions. Thermodynamic modelling suggests that diamond‐bearing gneisses attained P–T conditions of ≥3.5 GPa and 800–850 °C, similar to eclogites and garnet peridotites. We argue that diamond formed when carbonaceous sediment underwent UHP metamorphism at mantle depth exceeding 100 km during continental subduction in the Late Cretaceous (c. 95–92 Ma). The finding of diamond confirms UHP metamorphism in the Pohorje Mountains, the most deeply subducted part of Austroalpine units.  相似文献   

Sandstone Turning by Abrasive Waterjet     

Petr Hlaváček  Ján Cárach  Sergej Hloch  Karol Vasilko  Dagmar Klichová  Jiří Klich  Dominika Lehocká 《Rock Mechanics and Rock Engineering》2015,48(6):2489-2493

  相似文献   

Cholera resurgence in Piura,Peru: examining climate associations during the 1997–1998 El Niño     

Iván J. Ramírez 《GeoJournal》2015,80(1):129-143

  相似文献   

The capacity of European Higher Educational Institutions to address threats imposed by natural hazards     

Skevi Perdikou  Jiri Horak  Lena Halounová  Roshani Palliyaguru  Andrew Lees 《Natural Hazards》2016,81(3):1447-1466

  相似文献   

Understory and small trees contribute importantly to stemflow of a lower montane cloud forest          下载免费PDF全文

Teresa Margarita González‐Martínez  Guadalupe Williams‐Linera  Friso Holwerda 《水文研究》2017,31(5):1174-1183

Stemflow (Sf) measurements in tropical rain and montane forests dominated by large trees rarely include the understory and small trees. In this study, contributions of lower (1‐ to 2‐m height) and upper (>2‐m height and <5‐cm diameter at breast height [DBH]) woody understory, small trees (5 < DBH < 10 cm), and canopy trees (>10‐cm DBH) to Sf per unit ground area (Sf_a) of a Mexican lower montane cloud forest were quantified for 32 days with rainfall (P) during the 2014 wet season. Rainfall, stemflow yield (Sf_y), vegetation height, density, and basal area were measured. Subsequently, stemflow funneling ratios (SFRs) were calculated, and three common methods to scale up Sf_y from individual trees to the stand level (tree‐Sf_y correlation, P‐Sf_y correlation, and mean‐Sf_y extrapolation) were used to calculate Sf_a. Understory woody plants, small trees, and upper canopy trees represented 96%, 2%, and 2%, respectively, of the total density. Upper canopy trees had the lowest SFRs (1.6 ± 0.5 Standard Error (SE) on average), although the lower understory had the highest (36.1 ± 6.4). Small trees and upper understory presented similar SFRs (22.9 ± 5.4 and 20.2 ± 3.9, respectively). Different Sf scaling methods generally yielded similar results. Overall Sf_a during the study period was 22.7 mm (4.5% of rainfall), to which the understory contributed 70.1% (15.9 mm), small trees 10.6% (2.4 mm), and upper canopy trees 19.3% (4.4 mm). Our results strongly suggest that for humid tropical forests with dense understory of woody plants and small trees, Sf of these groups should be measured to avoid an underestimation of overall Sf at the stand level.  相似文献   

Dynamics of Saxothuringian subduction channel/wedge constrained by phase‐equilibria modelling and micro‐fabric analysis          下载免费PDF全文

S. Collett  P. Štípská  V. Kusbach  K. Schulmann  G. Marciniak 《Journal of Metamorphic Geology》2017,35(3):253-280

Subduction and exhumation dynamics can be investigated through analysis of metamorphic and deformational evolution of associated high‐grade rocks. The Erzgebirge anticline, which forms at the boundary between the Saxothuringian and Teplá‐Barrandian domains of the Bohemian Massif, provides a useful study area for these processes owing to the occurrence of numerous meta‐basites preserving eclogite facies assemblages, and coesite and diamond bearing quartzofeldspathic lithologies indicating subduction to deep mantle depths. The prograde and retrograde evolution of meta‐basite from the Czech portion of the Erzgebirge anticline has been constrained through a combination of thermodynamic modelling and conventional thermobarometry. Garnet growth zoning indicates that the rocks underwent burial and heating to peak conditions of 2.6 GPa and at least 615 °C. Initial exhumation occurred with concurrent cooling and decompression resulting in the growth of amphibole and zoisite poikiloblasts overgrowing and including the eclogite facies assemblage. The development of clinopyroxene–plagioclase–amphibole symplectites after omphacite and Al‐rich rims on matrix amphibole indicate later heating at the base of the lower crust. Omphacite microstructures, in particular grain size analysis and lattice‐preferred orientations, indicate that the prograde evolution was characterized by a constrictional strain geometry transitioning into plane strain and oblate fabrics during exhumation. The initial constrictional strain pattern is interpreted as being controlled by competing slab pull and crustal buoyancy forces leading to necking of the subducting slab. The transition to plane strain and flattening geometries represents transfer of material from the subducting lithosphere into a subduction channel, break‐off of the dense slab and rebound of the buoyant crustal material.  相似文献   

Generalized plasticity state parameter‐based model for saturated and unsaturated soils. Part II: Unsaturated soil modeling     

Diego Manzanal  Manuel Pastor  José Antonio Fernández Merodo 《国际地质力学数值与分析法杂志》2011,35(18):1899-1917

The aim of this paper is to extend the generalized plasticity state parameter‐based model presented in part 1 to reproduce the hydro‐mechanical behavior of unsaturated soils. The proposed model is based on two pairs of stress–strain variables and a suitable hardening law taking into account the bonding—debonding effect of suction and degree of saturation. A generalized state parameter for unsaturated state is proposed to reproduce soil behavior using a single set of material parameters. Generalized plasticity gives a suitable framework to reproduce not only monotonic stress path but also cyclic behavior. The hydraulic hysteresis during a drying—wetting cycle and the void ratio effect on the hydraulic behavior is introduced. Comparison between model simulations and a series of experimental data available, both cohesive and granular, are given to illustrate the accuracy of the enhanced generalized plasticity equation. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Volume thermal expansion along the jadeite–diopside join     

Francesco Pandolfo  Fernando Cámara  M. Chiara Domeneghetti  Matteo Alvaro  Fabrizio Nestola  Shun-Ichiro Karato  George Amulele 《Physics and Chemistry of Minerals》2015,42(1):1-14

  相似文献   

Flood forecasting in the upper Uruguay River basin     

A. S. Fernández Bou  R. Ventura De Sá  M. Cataldi 《Natural Hazards》2015,79(2):1239-1256

  相似文献