Thermal evolution of inverted basins: Constraints from apatite fission track thermochronology in the Cuyo Basin, Argentine Precordillera

Apatite fission track thermochronology (AFTT) was applied to derive the thermal history of formation and inversion of the oil-bearing Triassic–Cretaceous Cuyo Basin, Argentine Precordillera. The obtained central fission track ages range from 13 to 163 Ma, and the mean track lengths from 8.2 to . Based on the integration of AFTT, stratigraphic and structural data, five evolutionary phases are here proposed for the studied area: I—Late Permian cooling related to the extrusion of basement volcanics, and initial extensional regime responsible for the Cuyo Basin formation, II—Triassic–Jurassic heating linked with the filling, and consequent burial, of the Cuyo Basin, III—Jurassic–Paleogene tectonic stabilization, IV—Early Miocene heating related to the load of foreland sedimentation, V—Late Miocene rapid cooling related to the Cuyo Basin inversion. During the Late Miocene, rock units formed in different crustal levels were juxtaposed through thrust, reverse and normal faulting, resulting in contrasting old and very young central fission track ages in closely spaced samples.     

Thermotectonic and fault dynamic analysis of Precambrian basement and tectonic constraints with the Parana basin

The Precambrian crystalline basement of southeast Brazil is affected by many Phanerozoic reactivations of shear zones that developed during the end of the Neoproterozoic in the Brasiliano orogeny. These reactivations with specific tectonic events, a multidisciplinary study was done, involving geology, paleostress, and structural analysis of faults, associated with apatite fission track methods along the northeastern border of the Parana basin in southeast Brazil.The results show that the study area consists of three main tectonic domains, which record different episodes of uplift and reactivation of faults. These faults were brittle in character and resulted in multiple generations of fault products as pseudotachylytes and ultracataclasites, foliated cataclasites and fault gouges.Based on geological evidence and fission track data, an uplift of basement rocks and related tectonic subsidence with consequent deposition in the Parana basin were modeled.The reactivations of the basement record successive uplift events during the Phanerozoic dated via corrected fission track ages, at (Ordovician); (Triassic); (Jurassic), (Early Cretaceous); (Late Cretaceous) and (Late Cretaceous). These results indicate differential uplift of tectonic domains of basement units, probably related to Parana basin subsidence. Six major sedimentary units (supersequences) that have been deposited with their bounding unconformities, seem to have a close relationship with the orogenic events during the evolution of southwestern Gondwana.     

Post-Gondwana break-up record constraints from apatite fission track thermochronology in NW Namibia

The break-up of Western Gondwana Supercontinent was responsible in NW Namibia for significant tectono-thermal events at Early Cretaceous. In the Kaoko Belt and Walvis Basin, several evidences of this plate readjustment are registered: Etendeka Province, Great Escarpment Mountains, Precambrian structure reactivations, unconformities of surfaces in both continental area and margin basins. Apatite fission track thermochronology applied to the Kaoko basement rocks provides evidence of long-lived cooling history since the Early Cretaceous. The thermal modelings indicate accelerated uplift and/or upwarping of the local crust at followed by a gradual and continuous cooling history.     

Modeling the fission track etching process in apatite: Segmentation or crystallography influence

In this study, two factors which can influence fission track etching in apatite are considered: track segmentation (induced by thermal annealing) and variable radial etching speed (due to the reagent diffusion during the etching process).

During the latent track annealing, two distinguishable steps can be identified by measuring track lengths or diameters. A length reduction is firstly observed, followed by a segmentation process which leads to the emergence of disrupted regions (gaps).

At present time, electron microscopy studies on fission tracks in apatite show profiles which lead to hypotheses of a variable radial etching speed versus depth. These variations can be interpreted in terms of acid diffusion along the track. Moreover, the existence of several bulk etching speeds related to crystallographic orientation is approached.

Taking into account these different points, a software program, integrating parameters as original track orientation and depth, number of gaps, etc., is developed in order to model the track profile evolution during the etching process. Comparison with experiments in Durango apatite (Mexico) are also undertaken.     

The effect of simultaneous temperature, pressure and stress on the experimental annealing of spontaneous fission tracks in apatite: a brief overview

Tracks made in minerals by the electronic stopping of uranium fission fragments provide a modern geological dating tool, and are believed also to yield specific information on the low-temperature thermal history of rocks. Experimental work showing that the damaged crystal lattice along a fission track recovers primarily as a function of temperature ignored the fact that the basic theory of atomic diffusion requires an exponential decrease in the intrinsic diffusion coefficient with increasing pressure. Here, fission track recovery was experimentally investigated in basic apatite under the simultaneous influences of temperature, pressure and stress. We show that track fading is a complex recovery mechanism responding to several environmental physical parameters simultaneously. In particular a strong decrease in the track recovery rate was observed as a function of increasing pressure. And a nearly temperature-independent recovery was observed in samples under stress.     

Thermochronology of the South American platform in the state of São Paulo, Brazil, through apatite fission tracks

The fission-track method (FTM) in apatite was applied to 45 samples collected in the Serra da Mantiqueira (Mantiqueira mountain range), the Serra do Mar (Mar mountain range), regions next to these mountain ranges and the coastal region between Ubatuba and Santos in the State of São Paulo, Brazil, to study the thermochronology of the South American Platform in southeast Brazil and its influence on Santos and Campos basins. The data presented in this work complement the previously presented data on the same region (Tello Saenz et al., 2003. J. S. Am. Earth Sci. 15, 765–774) with 31 new samples analyzed. The weighted mean of the corrected ages from high Mantiqueira (around 1000 m), , coincides with the South Atlantic opening. The fact that its thermal history starts at a relatively low temperature suggests that the age of would be the formation age of Serra da Mantiqueira due to a rapid pulse, in which tracks had no time to be retained at the closure temperature, that is . The Serra do Mar presents a more complicated thermal history, with several reactivations indicated by the changes in the slope of its cooling curve. The thermal histories obtained in the regions next to these mountain ranges are compatible with the results mentioned above. The Santos Basin has unconformities that agree with changes in the slope thermal histories of the studied region.     

Detection efficiency of fission tracks in apatite related to mica external detectors by the spike irradiation technique

Detection efficiency of fission tracks in non-annealed and annealed Durango apatite crystals related to mica external detectors for fission track dating was estimated experimentally using the spike irradiation technique [Suzuki, 2002a. Abstracts of 21st International Conference on Nuclear Tracks in Solids, p. 22]. The relation of the fission track density between apatite samples and mica external detectors is an important parameter for the determination of fission track ages using an absolute approach especially for crystalline minerals. Spike irradiation of uranium-235-induced fission fragments was carried out using a high uranium content glass, GE1497, fixed firmly on the sample surface. Experimental works were carried out for sections parallel and perpendicular to the crystallographic c-axis of apatite. The detection efficiency of fission tracks in non-annealed apatite related to the mica external detectors was estimated to be 0.90 for the prism face and 0.99 for the basal face. The fission track age of Durango apatite averaged for the prism and basal faces was estimated to be 30.6 (±2.5) Ma, which is concordant with reference values reported previously, using the detection efficiency data with a B₀ value of the CN5 monitor glass and a U-238 spontaneous decay constant value of . The results also indicate that the B₀ age calibration method can be used effectively for the absolute evaluation of fission track ages of apatite.     

The fission systematics of (15.9 MeV/u) Au ions in polymer CR-39

It has been demonstrated that high-energy heavy ions undergo fission while propagating in dielectric solids. Since these materials act as particle detectors because of their ability to retain primary ionization damage that can be fixed and enlarged with chemical etching, therefore, in principle, a complete kinematical analysis of fission events is possible. The crucial point in this regard is the availability of a well-calibrated range-energy relation, which is necessary for mass identification. We have developed an analytical method to convert the geometrical parameters of fission fragment tracks into physical parameters using an equation that expresses velocity as a polynomial of mass and range. A set of nine different polynomials was used to represent small regions of mass and range in order to improve accuracy. In the case of (15.9 MeV/u) Au ions incident normally on CR-39, we have found about 200 events which could be categorized as in-flight fission of Au ions inside the body of the detector. Mass distributions and cross sections of fission events have been calculated.     

Observations on the geometries of etched fission and alpha-recoil tracks with reference to models of track revelation in minerals

The kinetic and atomistic theories of crystal growth and dissolution are used to interpret the shapes and orientations of fission-track, recoil-track and dislocation etch pits in tri-octahedral phlogopite and di-octahedral muscovite. An atomistic approach combined with symmetry considerations lead to the identification of the periodic bond chains that determine the etch pit morphologies and relative etch rates at a chemical level: O–Mg–O in phlogopite, O–Mg–O–Fe in biotite and O–Al–O in muscovite. Using first-order estimates of the bond strengths, it is possible to account for the relative track etch rates in these minerals. The reported, sometimes simultaneous, occurrence of triangular, polygonal and hexagonal etch pit contours in phlogopite, some of which violate the crystal symmetry, suggests that the cohesion of the phlogopite lattice is lost over a much larger radius than that of the track core around the trajectories of particles for which the energy loss exceeds a threshold value. This is interpreted as an indication of pronounced sublattice and anisotropic effects during track registration.     

The pore opening process of etching polymer films irradiated by single and multiple heavy ions. The etching process in the range of the track core radius (10 nm)

The technique of electrochemical etching of irradiated polymer films is an useful method to investigate structures of the track cores. In the case of the investigation of multiple track foils, the mean effective radius corresponds to the average of all synchron etching pores. On the other hand, the etching cones of all tracks do not break through to conducting micro channels coincidentally. The statistical character of this pore opening (break through) process is still unexplained, although several effects concerning this topic have been observed in the past. Another computer program simulates by way of the Monte Carlo Method the etching process of an ensemble of tracks within a thin polymer film. The conductivity of the multiple track etching foil can be described by the convolution between the conductivity of a single pore and the time dependent breakthrough rate. By way of the Laplace Transforms the measurements of the multiple and single track etching polymer films can be deconvoluted and yield the statistical nature of the pore opening process.     

The use of track registration detectors to reconstruct contemporary and historical airborne radon (RN) and radon progeny concentrations for radon-lung cancer epidemiologic study

Epidemiologic studies that investigate the relationship between radon and lung cancer require accurate estimates for the long-term average concentrations of radon progeny in dwellings. Year-to-year and home-to-home variations of radon in domestic environments pose serious difficulties for reconstructing an individual's long-term radon-related exposure. The use of contemporary radon gas concentrations as a surrogate for radon-related dose introduces additional uncertainty in dose assessment. Studies of glass exposed in radon chambers and in a home show that radon progeny deposited on, and implanted in, glass hold promise for reconstructing past radon concentrations in a variety of atmospheres. We developed an inexpensive track registration detector for the Iowa Radon Lung Cancer Study (IRLCS) that simultaneously measures contemporary airborne radon concentrations, surface deposited alpha activity density, and implanted ²¹⁰Po activity density. The implanted activity is used to reconstruct the cumulative radon and radon progeny exposure from the age of the glass and the ratios of the contemporary deposited activiteis to airborne radon gas activity. We placed over 2500 of these detectors in more than 1000 homes and retrieved 97% of them after a one-year exposure period. A preliminary analysis of the 1280 detectors that have undergone quality assurance review shows that the modules are meeting their accuracy and precision goals (10%). There is good correlation (r²0.5) between the total radon exposure estimated from contemporary radon gas measurements and historical average reconstructed from the implanted ²¹⁰Po surface activity. The linear regression slope of the airborne radon exposure to implanted activity is the same as the room model slope based on typical room parameters. This correlation improves (r²0.7) when the deposited surface activity measurements are added to the linear regression. Thus, track-registration detectors can contribute to accurate radon-related dose assessment in epidemiologic studies. Additional work is planned to incorporate the deposited activities in a more sophisticated reconstruction model.     

Insights from stable isotopes of water and hydrochemistry to the evolutionary processes of groundwater in the Subei lake basin,Ordos energy base,Northwestern China

ABSTRACT

Changes in groundwater evolutionary processes due to aquifer overexploitation show a world-wide increase and have been of growing concern in recent years. The study aimed to improve the knowledge of groundwater evolutionary processes by means of stable water isotopes and hydrochemistry in a representative lake basin, Ordos energy base. Groundwater, precipitation, and lake water collected during four campaigns were analysed by stable isotopes and chemical compositions. Results showed that temperature effect predominated the isotope fractionation in precipitation, while evaporation and inadequate groundwater recharge were the key factors explaining high salinity and isotopic enrichment in lake water. Additionally, the Kuisheng Lake was a preferential area of groundwater recharge, while the Subei Lake received less sources from underlying aquifer due to the combined effects of low permeable zone and upstream groundwater captured by the production wells. The homogeneous isotope signatures of groundwater may be ascribed to the closely vertical hydraulic connectivity between the unconfined and the confined aquifers. Isotopically enriched groundwater pumping from well field probably promoted isotopic depletion in groundwater depression cone. These findings not only provide the conceptual framework for the inland basin, but also have important implications for sustainable groundwater management in other groundwater discharge basins with arid climate.     

集合经验模态分解在区域降水变化多尺度分析及气候变化响应研究中的应用

集合经验模态分解(EEMD)是一种适用于非线性、非平稳序列的信号分析方法, 将EEMD 应用于气候要素时间序列, 可提取可靠真实的气候变化信号, 同时, EEMD可以得到气候变化的固有时间尺度.本文使用EEMD方法, 从气候时间序列中提取气候信号中各个尺度的变化, 对渭河流域过去50年来的秋季降水进行多尺度分析,结果显示, 对于20世纪70年代末80年代初的全球气候突变, 渭河流域的秋季降水也有很好的响应, 而且大尺度上的响应要早于中小尺度, 其中在大尺度上主要表现为波动形式, 即降水距平正负位相持续期的变化, 从持续正位相到正负位相周期性交替出现; 而在中小尺度上主要是振幅大小, 即降水距平正负位相量级的变化, 量级从相对较大变为相对较小再逐渐增大. 关键词： 集合经验模态分解 多尺度变化 秋季降水 渭河流域     

The use of histological, histochemical and ultramorphological techniques to detect gill alterations in Oreochromis niloticus reared in treated polluted waters

Fish gills are constituted by primary filaments and secondary lamellae, which are formed, basically, by three different cell types: pillar cells, respiratory cells and erythrocytes that circulate in the lamellae interior. This respiratory organ is very appreciated in environmental studies since it is constantly in contact with the water, accomplishing exchanges; besides this, it presents a high adaptation capacity. In this work, some fishes were reared in polluted waters treated by the flotation method (treated group) and compared with others that were reared in clean waters (control group). The ultramorphological, histological and histochemical analyses were used. The fishes from the treated group presented morphological alterations when compared with the control groups, such as lamellar fusion, aneurism and detachment of the respiratory epithelium. These alterations demonstrate the several adaptations, as morphologic as physiologic, that fishes can present when exposed to an inappropriate environment. The techniques employed are good tools to detect morphological biomarkers in gills of Oreochromis niloticus submitted to polluted waters.     

The use of a data envelopment analysis efficient rule to produce a steady and high cooperation frequency in a spatial evolvement game

We use the data envelopment analysis (DEA) method to estimate the relative efficiency of the current strategy for each player in a game by taking the spatial distribution of strategies as input and the total payoff as output. Based on the optimal value of the DEA model, we present a DEA efficient rule to update the strategy in evolutionary games. Simulations of the prisoner’s dilemma game (PDG) [4] and the snowdrift game (SG) on two-dimensional regular lattices of four, six, and eight neighbors with periodic boundary conditions, are carried out; the results show the emergence of high and stable cooperator frequency. The heuristic analysis of the DEA efficient rule are discussed in detail. Our work may be helpful in exploring the promotion of cooperator behavior.     

Doping dependent metal to insulator transition in the (Bi,Pb)-2212 system: The evolution of structural and electronic properties with europium substitution

The present work investigates the effect of europium substitution on the(Bi,Pb)-2212 system in the concentration range 0.5 ≤ x ≤ 1.0.Phase analysis and lattice parameter calculations on the powder diffraction data and the elemental analysis of EDX show that the Eu atoms are successfully substituted into the(Bi,Pb)-2212 system.Resistivity measurements(64-300 K) reveal that the system exhibits superconductivity at x ≤ 0.5 and semiconductivity at x > 0.5.With the complete suppression of superconductivity which is known to be a quasi-two dimensional phenomenon in these materials,a metal to insulator transition takes place at x = 0.6 and the predominant conduction mechanism is found to be variable range hopping between localized states,resulting in macroscopic semiconducting behaviour.The results of electrical and structural properties of the doped(Bi,Pb)-2212 compounds suggest that the decrease of charge carrier concentration and the induced structural disorder are the more effective and dominant mechanisms in the origin of the metal to insulator transition and suppression of superconductivity due to Eu substitution at its Sr site.     

The use of symmetry in the search for canted ferromagnetism, its application to the molecular magnets Mn[N(CN)2]2 and Fe[N(CN)2]2

Canted ferromagnets present a important class of molecular magnets. In these materials the uncompensated magnetisation, created by the DzyaloshinskyMoriya interaction, has the particular property of being compatible with the symmetry of the underlying antiferromagnetic Hamiltonian. If the ordering transition is continuous, Landau theory and simple symmetry arguments about the crystal structure can be used to determine whether such parasitic ferromagnetism is possible, and therefore to aid the systematic search for new molecular ferromagnets.