Quantitative X‐ray maps of composition from a chlorite, K‐white mica, albite, quartz and garnet bearing thin section from a Sambagawa blueschist facies metapelite were combined with a multi‐equilibrium calculation method to calculate a P–T‐Fe3+/Fe2+‐deformation map at the millimetre scale. The studied sample was chosen because elongated chlorite crystallization tails (pressure shadows) rimmed by phengite are present, which is an appropriate assemblage for the quantification of the P–T evolution. Chlorite temperature and Fe3+ content maps were calculated by successive iterations for each pixel analysis of Fe3+ until convergence of the four chlorite‐quartz‐H2O equilibria that can be written using the Fe‐ and Mg‐amesite, clinchlore, daphnite and sudoite chlorite end‐members. The calculated map of Fe2+/Fe3+ in chlorite is in good qualitative agreement with the in situ mapping of this ratio using XANES (X‐ray absorption near edge structure) techniques. The temperature map indicates that high temperature chlorite zones with low Fe3+ contents alternate with lower temperature zones and higher Fe3+ contents in the crystallization tail. Late fractures perpendicular to the elongation axis of the tail are filled by very low temperature chlorite (<250 °C) showing Fe3+/Fetotal up to 0.4. Groups of chlorite and mica pixels were then identified based on compositional and structural criteria, and a P–T‐deformation map was calculated using representative analyses of these groups. The calculated P–T‐deformation map suggests that in contrast to chlorite, the composition of most mica did not change significantly during exhumation. Mica reequilibrated in late EW shear bands only. EW shearing was already active at 0.1 GPa, 500 °C, which corresponds to the peak temperature (and probably pressure) conditions, at reduced redox conditions. The intensity of deformation probably decreased with decrease in temperature to ~350–400 °C. At this temperature, a second main deformation event corresponding to a further EW stretching occurred and was still active below 250 °C and more oxidizing conditions. These results indicate that the scale at which P–T data can be obtained is now close to the scale of observation of structural geologists. A close link between deformation and mineral reaction is therefore possible at the microscopic scale, which provides information about the relationship between deformation and mineral reactivity, the modalities of deformation with time and the P–T conditions at which it occurred. 相似文献
A constitutive law for viscoelastic behaviour of rocks is derived from irreversible thermodynamics. To this model, two specific parameters are introduced; one is an internal state variable which is a variable concerning the microstructures such as defects in crystals or microcracks, and the other is a temperature reduced time obtained by normalizing the various temperature behaviours. A large number of internal state variables have the respective relaxation times and show the respective time evolutions, while a set of the time evolutions generates temporal power-law behaviour of rocks. The time evolutions of internal states are regarded as dynamics of elements of the generalized Maxwell model, and the stress–strain relation is represented by a response function following a temporal power-law in terms of linear system theory. This relation is inversely formulated to investigate the source field from output data. This model enables us to explain experimentally-based constitutive laws for transient and steady-state behaviour of rocks (e.g., lherzolite) following a temporal power-law and for attenuation behaviour of polycrystals (e.g., olivine) represented by a relation between the quality factor and frequency. Both laws show power-laws on deformation time or frequency depending on the fractal structure in polycrystals or rocks, and the experimental high-temperature behaviours can be extrapolated to long deformation time or high frequency behaviour. 相似文献
We present results of computations on the interaction of solid-phase electrum–argentite–pyrite (weight ratios 210−5/ 210−3/1 and 210−5/410−2/1) association with Cl-containing aqueous moderately acid solutions (0.5m NaCl, pH = 3.08) at 300 °C and 500 bars. These data are a physicochemical basis for predicting the geochemical behavior of Au and Ag during the hydrothermal-metasomatic transformation of Au-Ag-pyrite. We also propose a technique of study of this process based on the phase equilibria of the subsystem Au–Ag–S with the aqueous solution at different liquid/solid (l/s) ratios, with the use of new graphic diagrams. The relationship of the composition of the solid-phase association with l/s ratio in real boundary conditions (Au = 17 ppm, mAu/mAg = 10–3.57–10–2.28) is shown. The maximum l/s values for complete leaching of gold and silver (l/smax = 200–800) are estimated. It has been established that argentite is the first to dissolve when mAu/mAg(s) > mAu/mAg(sol), and electrum, when mAu/mAg(s) < mAu/mAg(sol).
The experimental results showed that at 300 °C, the conversion of electrum (NAu = 300‰) nonequilibrated with pyrite into an Au-richer form (NAu = 730‰) and argentite follows an intricate kinetic scheme. Using the Pilling-Bedwords kinetic equation for processing data yielded the process rate constant K = 2.8(±0.5)10−5 g2cm−4day−1. With this equation, the time of the complete conversion of 200 μm thick flat gold grains is 604 days. These data evidence a significant role of kinetic factors in hydrothermal-metasomatic processes involving native gold, which requires combination of thermodynamic and kinetic approaches on the construction of geologo-genetic models for hydrothermal sulfide formation. 相似文献
The European Emissions Trading System (EU ETS) is the central pillar of the EU response against climate change. This trading mechanism is considered, from the theoretical point of view, as the most cost-effective method to reduce GHG. However, previous studies show that the agents who participate in these markets may behave in a way that may lead to inefficient CO2 prices, creating doubts about the static and dynamic efficiency of the system. This article analyses these possible anomalies by first trying to model the ETS in a more realistic way, addressing some of the limitations of previous models, and second, by comparing the results with real market transactions. For this, a bottom-up, multi-sector model has been built, which represents the EU ETS in an integrated, cross-sectoral way, paying particular attention to the interactions among the most emissions intensive industries. The results show the benefits of this modelling approach and how it better reflects real market conditions. Some preliminary conclusions regarding the behaviour of the agents in the ETS market are also presented.
POLICY RELEVANCE
Low allowance prices in the EU ETS have put into question the dynamic efficiency of the EU ETS system, prompting various ideas for structural reform. However, determining the right reform also requires estimating correctly how agents will respond to it. This article proposes a tool to realistically simulate the EU ETS under the assumption of rational agents, and compare it to real market outcomes, in order to understand better the behaviour of agents in this carbon market, and therefore how to design better policies. 相似文献
Sustainability of urban transportation and residents' daily mobility is increasingly important for the future of urban regions. In this paper, we present a novel methodology combining mapped survey responses (gathered using public participation GIS) and sophisticated multimodal routing analysis to understand patterns of suburban residents' daily mobility. Our particular focus is on residents' mode choices and their optimality in terms of travel time. We also examine the carbon-intensity of potential mode choice mismatches where a comparatively slower travel mode is chosen for a particular trip. This paper shows how the combination of the two data sources create new possibilities for analysing daily mobility by enabling the comparison of self-reported, geographically referenced mobility patterns and modelled, objectively “optimal” patterns. Our case study results from a rapidly growing metropolitan area, Greater Helsinki in Finland, indicate that people have rather sustainable daily mobility practices. Their daily trips are typically short (median 1.8 km), and non-motorised travel modes are the most popular. Also the share of car travel is significant. While public transport clearly has the lowest modal share, it is frequently used on longer trips to destinations where public transport connections are good (particularly the city centre). In 44% of trips, the respondents choose the fastest travel mode. When a comparatively slower travel mode is chosen, it most often produces less CO2 emissions than the fastest mode. However, particularly on shopping trips – the most commonly reported type of trip – car driving dominates as the fastest means of transportation. When a slower mode is chosen on a shopping trip, it is typically more carbon-intensive than the fastest mode would have been in that case. The methodology presented here can be used to support local decision making, particularly when daily services and transport infrastructure are planned or reorganised. 相似文献
Ecological data for the Atlantic humpback dolphin Sousa teuszii are scant. Six on-effort Sousa teuszii sightings were recorded during 817.6?km of boat-based effort in the Río Nuñez region of Guinea during October and November 2013. Two incidental sightings were also reported. Groups comprised 1–25 animals. Photo-identification produced a minimum population estimate of 47 animals. Most sightings (n = 5) were located close (<1?km) to shore along a 5.7?km stretch of coast on the west side of Île de Taïdi, primarily over shallow, sand–mud habitat. Two very distinctive individuals were present in all four Taïdi photo-identification encounters, suggesting high site fidelity and stable associations. Two sightings occurred in the outer Río Nuñez Estuary much farther from the coast (5–12?km) but in relatively shallow water (≤15?m) over sand–mud sediment. Focal follows (n = 5: 0.2–3.8?h duration) produced 9.02?h of behavioural data. Travel (51%), foraging (39%) and feeding (9.2%) dominated, with Taïdi dolphins spending more time foraging and feeding than the outer estuary groups. Three individuals had linear-severed dorsal fins consistent with injuries from fishing line. Some management implications of variation in habitat, site fidelity and movements of Sousa teuszii groups are discussed. 相似文献
A long-term mark-recapture study was used to assess the movement patterns of surf-zone fishes in the St Lucia Marine Reserve, a marine protected area within the iSimangaliso Wetland Park, a World Heritage Site on the east coast of South Africa. Between 2001 and 2013, 6 613 fish from 71 species, caught by hook and line, were tagged at four sites within and adjacent to a no-take marine sanctuary area. A total of 1 004 (15.2%) recaptures were made from 17 species. The majority (82.4%) of these species displayed station-keeping behaviour, whereas only three were classified as wider-ranging species, and no species with discernible migratory behaviour was observed. Findings for five species with the highest recapture rates, namely Pomadasys furcatus, Epinephelus andersoni, E. marginatus, Dinoperca petersi and Lutjanus rivulatus, are presented in greater detail. Recapture rates ranged from 7% to 50% and time at liberty from 0 to 3 163 days. Individuals of all five species displayed station-keeping behaviour, with the 95th percentile of intra-study-site movements varying between 200 and 1 025 m (linear distance). However, four of the five species also displayed some ranging behaviour and made exploratory excursions ranging from 3.5 to 125 km, in both northerly and southerly directions. The dominance of station-keeping behaviour suggests that the St Lucia Marine Reserve sanctuary zone provides an important refuge for these species, with some export to adjacent areas. 相似文献